  FILENAME   \* MERGEFORMAT  EO12866_SNAP HFO-1234yf MVAC_RIN
2060-AP11_Final_Rule_20101214.doc 

ENVIRONMENTAL PROTECTION AGENCY					

40 CFR Part 82 

[EPA-HQ-OAR-2008-0664; FRL-xxxx-x] 

RIN 2060-AP11

Protection of Stratospheric Ozone: New Substitute in the Motor Vehicle
Air Conditioning Sector under the Significant New Alternatives Policy
(SNAP) Program

AGENCY:  Environmental Protection Agency (EPA).

ACTION:  Final Rule.

_______________________________________________________________________

SUMMARY:  The Environmental Protection Agency’s (EPA) Significant New
Alternatives Policy (SNAP) program is expanding the list of acceptable
substitutes for use in the motor vehicle air conditioning end-use as a
replacement for ozone-depleting substances.  The Clean Air Act requires
EPA to review alternatives for ozone-depleting substances and to
disapprove substitutes that present overall risks to human health and
the environment more significant than those presented by other
alternatives that are available or potentially available.  The
substitute addressed in this final rule is for use in new passenger cars
and light-duty trucks in the motor vehicle air conditioning end-use
within the refrigeration and air conditioning sector.  EPA finds
hydrofluoroolefin (HFO)-1234yf acceptable, subject to use conditions, as
a substitute for chlorofluorocarbon (CFC)-12 in motor vehicle air
conditioning for new passenger cars and light-duty trucks. The
substitute is a non-ozone-depleting gas and consequently does not
contribute to stratospheric ozone depletion.

DATES:  This final rule is effective on [insert date 60 days after
publication].  

ADDRESSES:  EPA has established a docket for this action under Docket ID
No. EPA-HQ-OAR-2008-0664.  All documents in the docket are listed on the
  HYPERLINK "http://www.regulations.gov"  www.regulations.gov  web site.
 Although listed in the index, some information is not publicly
available, e.g., confidential business information (CBI) or other
information whose disclosure is restricted by statute.  Certain other
material, such as copyrighted material, is not placed on the Internet
and will be publicly available only in hard copy form.  Publicly
available docket materials are available either electronically through  
HYPERLINK "http://www.regulations.gov"  www.regulations.gov  or in hard
copy at the Air Docket, EPA/DC, EPA West, Room 3334, 1301 Constitution
Ave., NW, Washington, DC.  This Docket Facility is open from 8:30 a.m.
to 4:30 p.m., Monday through Friday, excluding legal holidays. The
telephone number for the Public Reading Room is (202) 566-1744, and the
telephone number for the Air Docket is (202) 566-1742.

FOR FURTHER INFORMATION CONTACT:  Margaret Sheppard, Stratospheric
Protection Division, Office of Atmospheric Programs; Environmental
Protection Agency, Mail Code 6205J, 1200 Pennsylvania Avenue NW.,
Washington DC 20460; telephone number (202) 343-9163, fax number, (202)
343-2338; e-mail address at   HYPERLINK
"mailto:sheppard.margaret@epa.gov"  sheppard.margaret@epa.gov . 

Notices and rulemakings under the SNAP program are available on EPA's
Stratospheric Ozone Web site at   HYPERLINK
"http://www.epa.gov/ozone/snap/regulations.html" 
http://www.epa.gov/ozone/snap/regulations.html . The full list of SNAP
decisions in all industrial sectors is available at
http://www.epa.gov/ozone/snap.

SUPPLEMENTARY INFORMATION:  

This final rule provides motor vehicle manufacturers and their suppliers
an additional refrigerant option for motor vehicle air conditioning
(MVAC) systems in new passenger cars and light-duty trucks.  HFO-1234yf
(2,3,3,3-tetrafluoroprop-1-ene), the refrigerant discussed in this final
action, is a non-ozone-depleting substance.

Table of Contents

Does this action apply to me?

What abbreviations and acronyms are used in this action?

What is EPA’s final decision for HFO-1234yf for motor vehicle air
conditioning (MVAC)?

What are the final use conditions and why did EPA finalize these
conditions?

Why is EPA finding HFO-1234yf acceptable subject to use conditions?

What is the relationship between this SNAP rule and other EPA rules?

Significant New Use Rule

Rules under Sections 609 and 608 of the Clean Air Act

What is EPA’s response to public comments on the proposal?

Acceptability decision

Use conditions

Environmental impacts

Health and safety impacts

Retrofit usage

Use by “do-it-yourselfers”

Servicing issues

Cost, availability, and small business impacts

VIII.	How does the SNAP program work?

A.   What are the statutory requirements and authority for the SNAP
program?

		   B. 	What are EPA's regulations implementing section 612?

C.	How do the regulations for the SNAP program work?

	D. 	Where can I get additional information about the SNAP program?

IX.	Statutory and Executive Order Reviews

Executive Order 12866: Regulatory Planning and Review

Paperwork Reduction Act

Regulatory Flexibility Act

Unfunded Mandates Reform Act

Executive Order 13132: Federalism

Executive Order 13175: Consultation and Coordination with Indian Tribal
Governments

Executive Order 13045: Protection of Children from Environmental Health
and Safety Risks

Executive Order 13211: Actions that Significantly Affect Energy Supply,
Distribution, or Use

National Technology Transfer and Advancement Act

Executive Order 12898: Federal Actions to Address Environmental Justice
in Minority Populations and Low-Income Populations

Congressional Review Act

X.	References

Does this Action Apply to Me?

	This final rule regulates the use of the chemical HFO-1234yf
(2,3,3,3-tetrafluoroprop-1-ene, Chemical Abstracts Service Registry
Number (CAS Reg. No. 754-12-1) as a refrigerant in new motor vehicle air
conditioning (MVAC) systems in new passenger cars and light-duty trucks.
 Businesses in this end-use that might want to use HFO-1234yf in new
MVAC systems in the future include:

automobile manufacturers

manufacturers of motor vehicle air conditioners

Regulated entities may include:

Table 1–Potentially Regulated Entities, 

by North American Industrial Classification System (NAICS) Code

Category	NAICS code	Description of regulated entities

Industry	336111	Automobile Manufacturing

Industry	336391	Motor Vehicle Air-Conditioning Manufacturing



This table is not intended to be exhaustive, but rather a guide
regarding entities likely to be regulated by this action.  If you have
any questions about whether this action applies to a particular entity,
consult the person listed in the preceding section, “FOR FURTHER
INFORMATION CONTACT.”

II.	What abbreviations and acronyms are used in this action?

100-yr-one-hundred year time horizon

AEGL-Acute Exposure Guideline Level

AIST-the National Institute for Advanced Industrial Science and
Technology of Japan

ASHRAE-American Society for Heating, Refrigerating, and Air-Conditioning
Engineers

ATSDR-the U.S. Agency for Toxic Substances and Disease Registry

BAM-Bundesanstalt fuer Materialforschung und –pruefung (the German
Federal Institute for Materials Research and Testing)

CAA-Clean Air Act

CAS Reg. No.-Chemical Abstracts Service Registry Number

CBI-Confidential Business Information

CFC-chlorofluorocarbon

CFC-12-the ozone-depleting chemical dichlorodifluoromethane, CAS Reg.
No.  75-71-8

CFD-Computational Fluid Dynamics

CFR-Code of Federal Regulations

cm/s-centimeters per second

CO2-carbon dioxide, CAS Reg. No. 124-38-9

CRP-Cooperative Research Program

DIN-Deutsches Institut fuer Normung (designation for standards from the
German Institute for Standards)

DIY-“do-it-yourself”

DOT-the United States Department of Transportation

EPA-the United States Environmental Protection Agency

EO-Executive Order

FMEA-Failure Mode and Effect Analysis

FR-Federal Register

GWP-Global Warming Potential

HF-Hydrogen Fluoride, CAS Reg. No. 7664-39-3

HI-Hazard Index

HFC-hydrofluorocarbon

HFC-134a-the chemical 1,1,1,2-tetrafluoroethane, CAS Reg. No. 811-97-2

HFC-152a-the chemical 1,1-difluoroethane, CAS Reg. No. 75-37-6

HFO-hydrofluoroolefin

HFO-1234yf-the chemical 2,3,3,3-tetrafluoroprop-1-ene, CAS Reg. No.
754-12-1

ISO-International Organization for Standardization

JAMA-Japan Automobile Manufacturers Association

JAPIA-Japan Auto Parts Industries Association

LCA-Lifecycle Analysis

LCCP-Lifecycle Climate Performance

LFL-Lower Flammability Limit

LOAEL-Lowest Observed Adverse Effect Level

mg/L-milligram per liter

MIR-Maximum Incremental Reactivity

mJ-millijoule

mm-millimeter

MOE-Margin of Exposure

MPa-megapascal

MRL-Minimal Risk Level

MVAC-Motor Vehicle Air Conditioning

NAICS-North American Industrial Classification System

ng/L-nanograms per liter

NHTSA-the U.S. National Highway Traffic Safety Administration

NOAEL-No Observed Adverse Effect Level

NOEC-No Observed Effect Concentration

NPRM-Notice of Proposed Rulemaking

NTTAA-National Technology Transfer and Advancement Act

ODP-Ozone Depletion Potential

ODS-Ozone-Depleting Substance

OEM-Original Equipment Manufacturer

OMB-Office of Management and Budget

OSHA-the United States Occupational Safety and Health Administration

PAG-Polyalkylene Glycol

PMN-Pre-Manufacture Notice

POCP-Photochemical Ozone Creation Potential

POD-Point of Departure

ppm-parts per million

ppt-parts per trillion

psig-pounds per square inch guage

R-1234yf-ASHRAE designation for refrigerant HFO-1234yf 

R-134a-ASHRAE designation for refrigerant HFC-134a

R-152a-ASHRAE designation for refrigerant HFC-152a

R-744-ASHRAE designation for refrigerant CO2

RCRA-the Resource Conservation and Recovery Act

RFA-Regulatory Flexibility Act

SAE-SAE International, formerly the Society of Automotive Engineers

SBA-the United States Small Business Administration

SIP-State Implementation Plan

SNAP-Significant New Alternatives Policy

SNUN-Significant New Use Notice

SNUR-Significant New Use Rule

SO2-sulfur dioxide, CAS Reg. No. 7446-09-5

TEWI-Total Equivalent Warming Impact

TFA-Trifluoroacetic acid, CF3COOH, also known as trifluoroethanoic acid,
CAS Reg. No. 76-05-1

TSCA-the Toxic Substances Control Act

TWA-Time-Weighted Average

UF-Uncertainty Factor

UMRA-Unfunded Mandates Reform Act

VDA-Verband der Automobilindustrie (German Association for the
Automobile Industry)

VOC-Volatile Organic Compound

v/v-volume to volume

WEEL-Workplace Environmental Exposure Limit

What is EPA’s final decision for HFO-1234yf for motor vehicle air
conditioning (MVAC)?

In this final rule, EPA is finding HFO-1234yf acceptable, subject to use
conditions, as a substitute for CFC-12 in new MVAC systems for passenger
cars and light-duty trucks.  This determination does not apply to the
use of HFO-1234yf as a conversion or retrofit for existing MVAC systems.
 In addition, it does not apply to the use of HFO-1234yf in the air
conditioning or refrigeration systems of heavy-duty trucks, refrigerated
transport, or off-road vehicles such as agricultural or construction
equipment. 

EPA is not mandating the use of HFO-1234yf or any other alternative for
MVAC systems.  This final rule is adding HFO-1234yf to the list of
acceptable substitutes, subject to use conditions, in new MVAC systems. 
Automobile manufacturers have the option of using any refrigerant listed
as acceptable for this end-use, so long as they meet any applicable use
conditions.  

Under this decision, the following enforceable use conditions apply when
HFO-1234yf is used in a new MVAC system for passenger cars and
light-duty trucks: 

The high-pressure side of the MVAC system shall have a pressure relief
device located in the high pressure side of the compressor or
immediately adjacent to the compressor discharge fitting.  The device
shall release refrigerant only outside of the passenger, trunk, and
storage compartments and MVAC air distribution system.  These pressure
relief devices shall be designed to minimize impingement of the
refrigerant and oil on hot surfaces.

The MVAC system high-pressure side relief device identified above in 1.
shall be self-sealing.  In no case shall the maximum release (blow-off)
pressure be greater than the maximum refrigerant working pressure.

To prevent unnecessary discharge of refrigerant during operation, the
system shall have a means to limit the compressor operation by cutting
off transmission of power to the compressor before any component failure
occurs and before activation of any pressure relief device (i.e.,
compressor cutoff switch).

In no case shall any high-pressure side refrigerant pressure relief
valves (or burst disks) have an activation pressure greater than the
maximum working pressure of 4.14 MPa. Gauge (600 psig).  

The maximum pressure on the low-pressure side of the MVAC system shall
not exceed the saturation pressure of HFO-1234yf at 56oC.

HFO-1234yf refrigerant systems connections shall either be:

Located outside the passenger compartment and outside the passenger
cabin airflow path.

or

Designed to prevent leakage if the connections are located inside the
passenger cabin or in the passenger cabin airflow path.  For safety
reasons, individuals performing servicing shall follow the service and
repair leakage recommendations (e.g., from manufacturer and in service
shop manual), including any service procedures established to prevent
refrigerant from entering the cabin or airflow path.

High-side and low-side fittings shall be fitted with protective or
sealing caps.

All MVAC system service fittings shall be located for ease of attachment
of service hoses and shall be designed to minimize direct impingement of
refrigerant on the service technician.  Piping shall be of robust design
to avoid damage or permanent deformation while connecting or
disconnecting the service hose coupling(s) from factory charging and
service equipment.

HFO-1234yf must be used with the following service fittings:

For the low-side service port, use quick-connect fittings with an
outside diameter of 14 + 0.2 mm (0.551 + 0.00787 inches).  

For the high-side service port, use quick-connect fittings with an
outside diameter of 17 + 0.2 mm (0.669 + 0.00787 inches).

For connections with containers of 20 lbs or greater, use quick-connect
fittings with an outside diameter of 14 + 0.2 mm (0.551 + 0.00787
inches).

All fittings must be different from those for any other refrigerant.

A plainly legible and durable refrigerant label shall be mounted in a
clearly visible location under hood that does not require the removal of
any parts or covers to be read.  The label shall:  identify the
refrigerant; state the amount of refrigerant charge in grams (or
kilograms, to three decimal places); and identify the lubricant type
(polyalkylene glycol [PAG] or polyolester [POE]). The label either shall
include the chemical safety symbol for “flammable” or shall state in
text that the refrigerant is flammable in letters at least 3 mm in
height that are red in color.  The label shall contain the name or logo
of the original equipment vehicle manufacturer or the refrigeration
system manufacturer responsible for design compliance with this rule and
with SAE standards.  The label shall have a minimum size of 60 mm by 30
mm.  It shall have text in bold-type letters at least 3 mm in height for
identifying refrigerant, lubricant type and refrigerant amount.  If the
label contains text only and no symbols, the label shall also state the
following:

“CAUTION SYSTEM CONTAINS REFRIGERANT R-1234yf UNDER HIGH PRESSURE-TO
BE SERVICED ONLY BY QUALIFIED PERSONNEL” 

Manufacturers must conduct Failure Mode and Effect Analysis (FMEA) as
provided in SAE J1739 (adopted 2009).  Manufacturers must keep the FMEA
on file for at least three years from the date of creation. 

Once the standard SAE J639 becomes final with provisions for HFO-1234yf,
EPA will consider replacing use conditions 1 through 10 with a use
condition requiring the safety provisions of SAE J639. 

What are the final use conditions and why did EPA finalize these
conditions?

Summary of the use conditions

This rule finalizes ten use conditions that were included in the draft
SAE standard J639, which was available during the comment period on the
proposed rule.  The SAE standard has not yet been finalized.  Thus,
since EPA is unable to refer to the final SAE standard in the final
rule, EPA instead is including in the use conditions the safety
requirements provided in the draft SAE standard referred to in the
proposed rule and included in the docket (EPA-HQ-OAR-2008-0664-0012).  

The eleventh use condition requires the manufacturer of MVAC systems and
vehicles (i.e., the original equipment manufacturer [OEM]) to conduct
and keep records of a risk assessment and failure Fault Mode and Effects
Analysis (FMEA) for at least three years from the date of creation. 
There is an existing industry standard, SAE J1739, that gives guidance
on how to do this.  It is standard industry practice to perform the FMEA
and to keep it on file while the vehicle is in production and for
several years afterwards (US EPA, 2010a).

Reasons for revised use conditions

EPA proposed five use conditions in the Notice of Proposed Rulemaking
(NPRM) (October 19, 2009; 74 FR 53445).  One use condition required
manufacturers to meet all the safety requirements in the standard SAE
J639, “Safety Standards for Motor Vehicle Refrigerant Vapor
Compression Systems” and required use of unique servicing fittings
from that standard.  Another use condition required automobile
manufacturers to perform Fault Mode and Effect Analysis (FMEA) and to
keep records of the FMEA. 

The remaining three proposed use conditions specifically addressed risks
of flammability of HFO-1234yf and indirectly addressed risks of
generating hydrogen fluoride (HF) from combustion of HFO-1234yf.  For
the first of those proposed use conditions, which addressed the
passenger compartment, the concentration of HFO-1234yf was not to exceed
the lower flammability limit (LFL) in the free space for more than 15
seconds.  For the second proposed use condition, which addressed the
engine compartment, the concentration of HFO-1234yf was not to exceed
the LFL for any period of time.  A third proposed use condition, which
also addressed the engine compartment, would have required protective
devices, isolation and/or ventilation techniques in areas where there is
a potential to generate HFO-1234yf concentrations at or above 6.2%
volume to volume (v/v) in proximity to exhaust manifold surfaces and
hybrid or electric vehicle electric power sources.  

EPA based our determination of the appropriate use conditions to include
in the final rule using information in the docket at the time of
proposal, comments received on the proposed rule, and additional
information we have received since the NPRM was published.  We provided
additional opportunities for comment on the public comments and
additional information we received with them when we re-opened the
comment period on the proposed rule (74 FR 68558, December 28, 2009; 75
FR 6338, February 9, 2010).  First, SAE International’s Cooperative
Research Program (hereafter called the SAE CRP) issued a new report on
December 17, 2009 assessing risks of HFO-1234yf and carbon dioxide (CO2)
as refrigerants for MVAC.  This report found that the risks of
HFO-1234yf were low overall, and somewhat less than risks for another
potential alternative refrigerant (CO2, also know as R-744).  The
December 2009 CRP report found that the greatest risks from HFO-1234yf
are likely to come from generation of HF, both from thermal
decomposition and from ignition, rather than direct fire risks from
ignition of HFO-1234yf (EPA-HQ-OAR-2006-0664-0056.2).  (HF is a severe
irritant to the skin, eyes, and respiratory system.)  The SAE CRP
estimates risks of excessive HF exposure at approximately 4.6 x 10-12
occurrences per vehicle operating hour and risks of ignition at
approximately 9 x 10-14 occurrences per vehicle operating hour.  These
correspond roughly to one occurrence in the entire US fleet of passenger
vehicles over 2 years for HF risks and one occurrence in the US vehicle
fleet every 100 years for flammability risks.  For comparison, the risk
for excessive HF exposure is less than one ten-thousandth the risk of a
highway vehicle fire and one fortieth or less of the risk of a fatality
from deployment of an airbag during a vehicle collision
(EPA-HQ-OAR-2008-0664-0056.2).  Even these estimates may be conservative
because they assume that refrigerant could be released in a collision
severe enough to rupture the evaporator (under the windshield) while the
windshield and windows would remain intact and would prevent ventilation
into the passenger cabin in case of a collision
(EPA-HQ-OAR-2006-0664-0056.2). 

Second, we received a number of public comments regarding the proposed
use conditions.  Some commenters claimed that the second use condition
concerning concentrations in the engine compartment was infeasible
because in the event of a leak, there would always be some small volume
that would have a concentration over the LFL; these commenters further
stated that exceeding the LFL would not necessarily create a risk of
ignition, because one could have a leak that is not near a source of
heat or flame (EPA-HQ-OAR-2006-0664-0116.2; EPA-HQ-OAR-2006-0664-0060). 
Some commenters stated that flammability was not a significant risk from
use of HFO-1234yf, given the results of the SAE CRP risk assessment
(December 17, 2009).  These commenters stated that the use conditions
limiting refrigerant concentrations were not necessary.  These
commenters also suggested a number of alternative ways of phrasing the
use conditions in order to address risks from HF as well as
flammability.  Most of these comments suggested relying on the
performance of a risk assessment and Fault Mode Effect Analysis (FMEA)
consistent with SAE J1739 to determine appropriate protective
strategies.  Other commenters stated that the use conditions were not
sufficiently protective as proposed because of other risks:  (1) risks
due to generation of HF from HFO-1234yf, both from thermal decomposition
and from combustion; (2) risks from direct toxicity of HFO-1234yf; and
(3) risks from flammability of HFO-1234yf because the LFL becomes lower
than 6.2% at temperatures higher than 21ºC (EPA-HQ-OAR-2006-0664-0088,
-0054, -0089, -0097 and -0057).

After evaluating the comments and the additional information made
available to the public through the re-opened comment period, we have
decided not to include the three use conditions that directly address
flammability in the final rule.  We believe these use conditions are not
necessary to ensure that overall risks to human health and the
environment from HFO-1234yf will be similar to or less than those of
other available or potentially available refrigerants that EPA has
already listed or proposed as acceptable for MVAC.  This is because of
the low overall levels of risk identified for HFO-1234yf from
flammability and from ignition of HF (EPA-HQ-OAR-2008-0664-0056.2).  The
highest risk identified for HFO-1234yf is potential consumer exposure to
HF from decomposition and ignition, which is of the same order of
magnitude of risks of HF from the current most common automotive
refrigerant, hydrofluorocarbon (HFC)-134a (order of magnitude of 10-12
events per vehicle operating hour).  EPA previously found HFC-134a
acceptable for use in new and retrofit MVAC systems (59 FR 13044; March
18, 1994; and 60 FR 31092, June 13, 1995), without use conditions
addressing risks of HF.  Since that time, EPA has heard of no cases
where someone has been injured due to exposure to HF from decomposition
of HFC-134a from an MVAC system, and a risk assessment from the SAE CRP
found no published reports in the medical literature of injuries to fire
fighters or vehicle passengers from HF or other decomposition products
of HFC-134a (EPA-HQ-OAR-2008-0664-0008).  The direct risk of
flammability from HFO-1234yf is extremely small.  Further, the risks of
HFO-1234yf are comparable to or less than the risks from other available
or potentially alternatives in this end-use that EPA has already listed
or proposed as acceptable (e.g., HFC-152a, HFC-134a, and CO2)
(EPA-HQ-OAR-2008-0664-0086.1).

We have concluded that the use conditions we are including in the final
rule address the risks from both HF and flammability.  Use conditions in
the final rule that were taken from the draft industry standard SAE J639
provide for a pressure relief device designed to minimize direct
impingement of the refrigerant and oil on hot surfaces and for design of
the refrigerant circuit and connections to avoid refrigerant entering
the passenger cabin. These conditions will mitigate risks of HF
generation and ignition.  The pressure release device ensures that
pressure in the system will not reach an unsafe level that might cause
an uncontrolled, explosive leak of refrigerant, such as if the air
conditioning system is overcharged.  The pressure release device will
reduce the likelihood that refrigerant leaks would reach hot surfaces
that might lead to either ignition or formation of HF.  Designing the
refrigerant circuit and connections to avoid refrigerant entering the
passenger cabin ensures that if there is a leak, the refrigerant is
unlikely to enter the passenger cabin.  Keeping refrigerant out of the
passenger cabin minimizes the possibility that there would sufficient
levels of refrigerant to reach flammable concentrations or that HF would
be formed and transported where passengers might be exposed.  

	The last proposed use condition, requiring manufacturers to conduct and
keep records of FMEA according to the standard SAE J1739 remains
unchanged. 

The proposed use condition regarding conducting and keeping records of a
Fault Mode and Effects Analysis according to the standard SAE J1739
remains unchanged. We have revised the remaining proposed use condition
by replacing the reference to SAE J639 (adopted 2009) with specific
language adopted from the 2010 draft version of the standard.  This
incorporates language from the most recent version of the standard, with
new provisions designed specifically to address use of HFO-1234yf.  In
terms of substance, the final use conditions are essentially the same as
a number of provisions that were under consideration by SAE and were
made in the docket at the time of proposal (see
EPA-HQ-OAR-2008-0664-0012 and the proposed use condition). 

Why is EPA finding HFO-1234yf acceptable subject to use conditions?

EPA is finding HFO-1234yf acceptable subject to use conditions because
the use conditions are necessary to ensure that use of HFO-1234yf will
not have a significantly greater overall impact on human health and the
environment than other available or potentially available substitutes
for CFC-12 in MVAC systems.  Examples of other substitutes that EPA has
already found acceptable subject to use conditions for use in MVAC
include HFC-134a and HFC-152a.  HFC-134a is the alternative most widely
used in MVAC systems today.  EPA has also proposed to find CO2 (R-744)
acceptable subject to use conditions in MVAC (September 14, 2006; 71 FR
55140).

All alternatives listed as acceptable for use in MVAC systems in
passenger cars and light-duty trucks are required to have unique
fittings under use conditions issued previously under the SNAP Program
at 40 CFR part 82, appendix D to subpart G (61 FR 54040, October 16,
1996).  Thus, all substitutes for use in MVAC systems in passenger cars
and light-duty trucks are subject to those use conditions, at a minimum,
if found acceptable and thus are identified as acceptable subject to use
conditions.  For HFO-1234yf, the unique fittings that must be used for
MVAC systems are quick-connect fittings with an external diameter large
enough that they will not connect with cars or refrigerant containers
for HFC-134a or any other refrigerant, as described in the ninth use
condition above in section II.  The original submitter of HFO-1234yf to
the SNAP program has provided EPA with a copy of and a diagram for these
unique fittings.  As described above, the fittings will be quick-connect
fittings, different than those for any other refrigerant.  The low-side
service port and connections with containers of 20 lbs or greater will
have an outside diameter of 14 mm (0.551 inches) and the high-side
service port will have an outside diameter of 17 mm (0.669 inches), both
accurate to within 2 mm.  The submitter has not provided, and the draft
SAE J639 standard does not include, unique fittings for use with small
refrigerant containers or can taps.  Thus, the final use conditions do
not allow use of small containers for servicing MVAC systems.

In addition to the use conditions regarding unique fittings, which apply
under appendix D to subpart G of 40 CFR part 82, EPA is requiring use
conditions for the safe design of new MVAC systems using HFO-1234yf,
consistent with standards of the automotive industry (e.g., SAE J1739,
draft standard SAE J639).  These use conditions are intended to ensure
that new cars and light-duty trucks that have MVAC systems that use
HFO-1234yf are specifically designed to minimize release of the
refrigerant into the passenger cabin or onto hot surfaces that might
result in ignition or in generation of HF.  The industry standard SAE
J1739 gives guidelines on designing vehicles to address these risks.  

Cost and Availability

EPA received initial estimates of the anticipated cost of HFO-1234yf
from the manufacturer, claimed as confidential business information, as
part of the initial SNAP submission (EPA-HQ-OAR-2008-0664-0013 and
-0013.1).  Initial publicly available estimates on the cost of
HFO-1234yf were for approximately $40-60/pound (Weissler, 2008).  The
first automobile manufacturer to announce its commitment to use
HFO-1234yf as a refrigerant has confirmed that the prices in its
long-term purchase contracts are in the range that EPA considered at the
time of proposal (Sciance, 2010).

In May 2010, two major chemical manufacturers, including the original
submitter, issued a press release, committing to building a
“world-scale manufacturing facility” to produce HFO-1234yf
(EPA-HQ-OAR-2008-0664-0128.1).  The same manufacturers have committed to
providing HFO-1234yf in time to meet requirements of a European Union
directive to use only refrigerants with GWP less than 150 in new
automobile designs starting in 2011.  

Environmental impacts

EPA finds that HFO-1234yf does not pose significantly greater risk to
the environment than the other substitutes that are currently or
potentially available.  In at least in one aspect, HFO-1234yf is
significantly better for the environment than other alternatives
currently found acceptable subject to use conditions.  HFO-1234yf has a
hundred-year time horizon (100-yr) global warming potential (GWP) of 4
(Nielsen et al., 2007; Papadimitriou et al., 2007), compared to a GWP of
124 for HFC-152a, and a GWP of 1430 for HFC-134a (IPCC, 2007).  CO2,
another substitute currently under review in this end-use, has a GWP of
1, which is lower, but comparable to the GWP of HFO-1234yf.  A number of
other refrigerant blends containing HFCs or HCFCs have been found
acceptable subject to use conditions in MVAC that have higher GWPs in
the range of 1000 to 2400, such as R-426A, R-414A, R-414B, R-416A, and
R-420A.  Further, HFO-1234yf has no ozone depletion potential
(EPA-HQ-OAR-2008-0664-0013), comparable to CO2, HFC-152a, and HFC-134a,
and has less risk of ozone depletion than all refrigerant blends
containing HCFCs that EPA previously found acceptable subject to use
conditions for MVAC systems.

EPA also considered the aggregate environmental impact of all
anticipated emissions of HFO-1234yf, both for the proposed rule and for
this final rule.  We performed a conservative analysis that assumed
widespread use of HFO-1234yf as the primary refrigerant for MVAC, as
well as for other refrigeration and air conditioning uses that were not
included in the manufacturer’s original submission (ICF, 2009; ICF,
2010a,b,c,e).  Thus, we believe that actual environmental impacts are
likely to be less than those we considered, either at the proposal or
final stage.

Under Clean Air Act regulations (see 40 CFR 51.100(s)) addressing the
development of state implementation plans (SIPs) to attain and maintain
the national ambient air quality standards, HFO-1234yf is considered a
volatile organic compound (VOC).  Available information indicates that
HFO-1234yf has greater photochemical reactivity than HFC-134a, which is
exempt from the definition of “VOC” in 40 CFR 51.100(s).  Some of
the other acceptable substitutes in the MVAC end-use contain VOCs, such
as R-406A, R-414A, R-414B, and R-426A.  VOCs can contribute to
ground-level ozone (smog) formation.  For purposes of state plans to
address ground-level ozone, EPA has exempted VOCs with negligible
photochemical reactivity from regulation (40 CFR 51.100(s)).  The
manufacturer of HFO-1234yf has submitted a petition to EPA requesting
that the chemical be exempted from regulation as a VOC, based on a claim
that it has maximum incremental reactivity comparable to that of ethane
(EPA-HQ-OAR-2008-0664-0116.1).  Separate from this action, EPA is
reviewing that request and plans to issue a proposed rule shortly to
address it.  

Regardless of whether EPA determines to exempt HFO-1234yf from
regulation as a VOC for state planning purposes, other analyses
available in the docket during the public comment period indicated that
the additional contribution to ground-level ozone due to a widespread
switch to HFO-1234yf is likely to be around 0.01% or less of all VOC
emissions, based on the formation of reactive breakdown products such as
OH- (Luecken et al., 2009).  Since issuing the NPRM, we performed an
additional analysis that finds a worst-case increase in the Los Angeles
region of 0.080 ppb, or a contribution of only 0.1% of the 1997 8-hour
standard for ground-level ozone of 0.08 ppm (ICF, 2010b).  Our initial
analysis at the proposal stage had estimated a maximum increase in ozone
of 1.4 to 4.0% of the standard in the same region (ICF, 2009).  The
major difference between the 2009 and the 2010 versions of this analysis
involved modeling of atmospheric chemistry.  The 2010 study was based on
the kinetics and decomposition products predicted for HFO-1234yf, rather
than using the oxidation of sulfur dioxide (SO2) as a proxy for
decomposition of HFO-1234yf as was done in the 2009 study.  The 2010
analysis used updated baseline emission estimates that were 1.5% higher
to 5.8% lower than those in the 2009 analysis, depending on the year
analyzed (ICF, 2010e).  We also evaluated environmental impacts based on
alternative emissions estimates from a peer-reviewed journal article
provided during the public comment period (Papasavva et al., 2009);
these values ranged from 26.3% to 51.1% lower than EPA’s estimates in
the 2009 analysis (ICF, 2009; ICF, 2010c).  

Another potential environmental impact of HFO-1234yf is its atmospheric
decomposition to trifluoroacetic acid (TFA, CF3COOH).  TFA is a strong
acid that may accumulate on soil, on plants, and in aquatic ecosystems
over time and that may have the potential to adversely impact plants,
animals, and ecosystems.  Other fluorinated compounds also decompose
into TFA, including HFC-134a.  However, the amount of TFA produced from
HFO-1234yf in MVAC is estimated to be at least double that of current
natural and artificial sources of TFA in rainfall (Luecken et al.,
2009).  An initial analysis performed for EPA at the proposal stage
found that, with highly conservative emission estimates, TFA
concentrations in rainwater could be as high as 1.8 mg/L for the maximum
monthly concentration for the Los Angeles area and would be no higher
than 0.23 mg/L on an annual basis, compared to a no observed adverse
effect concentration of 1 mg/L for the most sensitive plant species
(ICF, 2009).  This analysis concluded, “Projected levels of TFA in
rainwater should not result in a significant risk of ecotoxicity.”  A
more recent analysis by Luecken et al (2009) that became available
during the initial public comment period reached the conclusion that
emissions of HFO-1234yf from MVAC could produce TFA concentrations in
rainwater of 1/800th to 1/80th the no-observed adverse effect level
(NOAEL) for the most sensitive algae species expected (Luecken et al.,
2009).  The conclusions in the Luecken study are supported by additional
analyses that have become available since we issued the proposed rule. 
A study from the National Institute of Advanced Industrial Science and
Technology (AIST) in Japan, which became available during the re-opened
comment period, estimated that concentrations of TFA in surface water
would be approximately twice the level in rainwater (Kajihara et al.,
2010).  This study found that this higher level in surface water would
be roughly 1/80th the NOAEL for the most sensitive algae species, even
with assumptions of high emissions levels (i.e., assuming that all types
of refrigeration and AC equipment currently using HFCs or HCFCs, not
just MVAC systems, would use HFO-1234yf).  Kajihara et al. (2010)
evaluated scenarios specific to Japan, with emissions of approximately
15,172 ton/yr in 2050, compared to a maximum of 64,324 metric tons/yr in
2050 in ICF, 2009 or a maximum of 24,715 metric tons/yr in 2017 in
Luecken et al (2009).  All three studies noted the potential for
accumulation in closed aquatic systems.

As we developed the proposed rule, the data we relied on indicated that
in the worst case, the highest monthly TFA concentrations in the area
with the highest expected emissions, the Los Angeles area, could exceed
the no observed adverse effect concentration for the most sensitive
plant species, but annual values would never exceed that value. 
Further, TFA concentrations would never approach levels of concern for
aquatic animals (ICF, 2009).  In a more recent analysis, ICF (2010a, b,
c, e) performed modeling for EPA using the kinetics and decomposition
products predicted specifically for HFO-1234yf and considered revised
emission estimates that were slightly lower than in a 2009 analysis
(ICF, 2009).  The revised analysis found a maximum projected
concentration of TFA in rainwater of approximately 1,700 ng/L, roughly
one-thousandth of the estimate from our 2009 analysis (ICF, 2010b). 
This maximum concentration is roughly 34% higher than the 1,264 ng/L
reported by Luecken et al. (2009), reflecting the higher emission
estimates we used (ICF, 2010b).  A maximum concentration of 1700 ng/L
corresponds to roughly 1/600th of the NOAEL for the most sensitive algae
species—thus, it is not a level of concern.  We find these additional
analyses confirm that the projected maximum TFA concentration in
rainwater and in surface waters should not result in a significant risk
of aquatic toxicity, consistent with our original proposal.

Human health and safety impacts

Occupational risks could occur during the manufacture of the
refrigerant, initial installation of the refrigerant into the MVAC
system at the car assembly plant, servicing of the MVAC system, or final
disposition of the MVAC system (i.e., recycling or disposal).  Consumer
risks could occur to drivers or riders in the passenger compartment. 
Risks of exposure to consumers could also occur if they purchase
HFO-1234yf and attempt to install or service the MVAC system without
proper training or use of refrigerant recovery equipment.  In addition,
members of the general public, consumers, and first-responders could
face risks in the case of a vehicle accident that is severe enough to
release the refrigerant.

To evaluate these potential human health and safety impacts, we
considered EPA’s own risk assessments (EPA-HQ-OAR-2008-0664-0036 and
-0038), as well as detailed risk assessments with fault-tree analysis
from the SAE CRP for HFO-1234yf and CO2 (EPA-HQ-OAR-2008-0664-0008 and
-0056.2), and scientific data provided in public comments on the topics
of health and safety risks.  Health and safety risks that we evaluated
included direct toxicity of HFO-1234yf, both long-term and short-term;
toxicity of HF formed through thermal decomposition or combustion of
HFO-1234yf; and flammability of HFO-1234yf.  

Occupational risks

For long-term occupational exposure to HFO-1234yf, EPA compared worker
exposures to a workplace exposure limit of 250 ppm over an 8-hour
time-weighted average.  For short-term occupational exposure to
HFO-1234yf, we compared worker exposure to an acute exposure limit of
98,211 ppm, divided by a margin of exposure of 30, for a value of 3270
ppm over 30 minutes.,

Section 609 of the Clean Air Act requires technicians servicing MVAC
systems for consideration (e.g., receiving money, credit, or services in
exchange for their work) to use approved refrigerant recycling equipment
properly and to have proper training and certification.  Therefore, we
expect that professional technicians have the proper equipment and
knowledge to minimize their risks due to exposure to refrigerant from an
MVAC system.  Thus, we found that worker exposure would be low. 
Further, EPA intends to pursue a future rulemaking under Section 609 of
the CAA to apply also to HFO-1234yf (e.g., servicing practices,
certification requirements for recovery and recycling equipment intended
for use with MVACs using HFO-1234yf, any potential changes to the rules
for training and testing technicians, and recordkeeping requirements for
service facilities and for refrigerant retailers).  If workers service
MVAC systems using certified refrigerant recovery equipment after
receiving training and testing, exposure levels to HFO-1234yf are
estimated to be on the order of 4 to 8.5 ppm on an 8-hour time-weighted
average (as compared with a 250 ppm workplace exposure limit) and 122
ppm on a 30-minute average (as compared with a short-term exposure level
of 98,211 ppm/[margin of exposure of 30] or 3270 ppm). 
(EPA-HQ-OAR-2008-0664-0036; EPA-HQ-OAR-2008-0664-0038).  We also
analyzed exposure levels during manufacture and final disposition at
vehicle end-of-life, and found that they would be no higher than 28 ppm
on a 15-minute average or 8.5 ppm on an 8-hour time-weighted average
(EPA-HQ-OAR-2008-0664-0038).  Therefore, the manufacture, use, and
disposal or recycling of HFO-1234yf are not expected to present a
toxicity risk to workers.

We did not analyze the risk of generation of HF in the workplace.  In
its December 17, 2009 Risk Assessment for Alternative Refrigerants
HFO-1234yf and R-744 (CO2), the SAE CRP indicated that “service
technicians will be knowledgeable about the potential for HF generation
and will immediately move away from the area when they perceive the
irritancy of HF prior to being exposed above a health-based limit”
(EPA-HQ-OAR-2008-0664-0056.2).  Since there is a similar potential to
form HF from other MVAC refrigerants that have been used for years, such
as CFC-12 or HFC-134a, it is reasonable to assume that service
technicians, recyclers, and disposers will handle HFO-1234yf similarly
and that use of HFO-1234yf does not pose a significantly greater risk in
the workplace with regard to HF generation than the use of those other
refrigerants.

In that same report, the SAE CRP also discussed qualitatively the risks
for emergency responders, such as firefighters or ambulance workers that
respond in case of a vehicle fire or collision.  With regard to risk of
fire, the CRP report stated that “Due to the low burning velocity of
HFO-1234yf, ignition of the refrigerant will not contribute
substantially to a pre-existing fire” (EPA-HQ-OAR-2008-0664-0056.2). 
EPA considers this reasonable, given a burning velocity for HFO-1234yf
of only 1.5 cm/s.  This is more than an order of magnitude less than the
burning velocity of gasoline, which is approximately 42 cm/s (Ceviz and
Yuksel, 2005).  Concerning first responder exposure to HF, the SAE CRP
stated, “Professional first responders also have training in chemical
hazards and possess appropriate gear which will prevent them from
receiving HF exposures above health-based limits”
(EPA-HQ-OAR-2008-0664-0056.2).  We agree with this assessment.  Other
MVAC refrigerants containing fluorine such as CFC-12, which was
historically used, and HFC-134a, which is the predominant refrigerant
currently in use, also can produce HF due to thermal decomposition or
combustion, and smoke and other toxic chemicals are likely to be present
in case of an automotive fire (CRP, 2008).  Therefore, it is reasonable
to expect that first responders are prepared for the presence of HF and
other toxic chemicals when approaching a burning vehicle and that they
will wear appropriate personal protective equipment.

EPA’s risk screen for HFO-1234yf evaluated flammability risks,
including occupational risks.  Modeling of concentrations of HFO-1234yf
in workplace situations such as at equipment manufacture and during
disposal or recycling at vehicle end-of-life found short-term, 15-minute
concentrations of 28 ppm or less—far below the lower flammability
limit (LFL) of 6.2% by volume (62,000 ppm) (EPA-HQ-OAR-2008-0664-0038). 
The SAE CRP’s risk assessments evaluated flammability risks by
comparing concentrations of HFO-1234yf with the LFL of 6.2%.  The SAE
CRP conducted Computational Fluid Dynamics (CFD) modeling of exposure
levels in case of a leak in a system in a service shop.  The SAE CRP’s
earlier February 26, 2008 risk assessment found that a leaked
concentration of HFO-1234yf exceeded the LFL only in the most
conservative simulation, with the largest refrigerant leak and with all
air being recirculated within the passenger cabin
(EPA-HQ-OAR-2008-0664-0010).  Updated CFD modeling performed for the
December, 2010 SAE CRP risk assessment found that concentrations of
HFO-1234yf sometimes exceeded the LFL, but only within ten centimeters
of the leak or less (EPA-HQ-OAR-2008-0664-0056.2).  The risk assessment
found the risk of this occupational exposure scenario to be on the order
of 10-26 cases per working hour.  We note that HFO-1234yf is less
flammable and results in a less energetic flame than a number of fluids
that motor vehicle service technicians and recyclers or disposers deal
with on a regular basis, such as oil, anti-freeze, transmission fluid,
and gasoline.  HFO-1234yf is also less flammable than HFC-152a, a
substitute that we have already found acceptable for new MVAC systems
subject to use conditions.  Thus, EPA finds that the risks of
flammability in the workplace from HFO-1234yf are similar to or lower
than the risk posed by currently available substitutes when the use
conditions are met.

Consumer exposure

EPA’s review of consumer risks from toxicity of HFO-1234yf indicated
that potential consumer (passenger) exposure from a refrigerant leak
into the passenger compartment of a vehicle is not expected to present
an unreasonable risk (EPA-HQ-OAR-2008-0664-0036,
EPA-HQ-OAR-2008-0664-0038).  However, consumer exposure from filling,
servicing, or maintaining MVAC systems may cause exposures at high
enough concentrations to warrant concern.  Specifically, this risk may
be due to a lack of professional training and due to refrigerant
handling or containment without the use of refrigerant recovery
equipment certified in accordance with the regulations promulgated under
CAA Section 609 and codified at 40 CFR part 82, subpart B.  Consumer
filling, servicing, or maintaining of MVAC systems may cause exposures
at high enough concentrations to warrant concern
(EPA-HQ-OAR-2008-0664-0036).  However, this rule does not specifically
allow for use of HFO-1234yf in consumer filling, servicing, or
maintenance of MVAC systems.  The manufacturer’s submission
specifically addressed HFO-1234yf as a refrigerant for use by OEMs and
by professional technicians (EPA-HQ-OAR-2008-0664-0013.1).  

The use conditions in this final rule provide for unique service
fittings relevant to OEMs and to professional technicians (i.e., unique
fittings for the high-pressure side and for the low-pressure side of the
MVAC system and unique fittings for large cylinders of 20 lb or more). 
EPA would require additional information on consumer risk and a set of
unique fittings from the refrigerant manufacturer for use with small
cans or containers of HFO-1234yf before we would be able to issue a
revised rule that allows for consumer filling, servicing, or maintenance
of MVAC systems with HFO-1234yf.

EPA has issued a significant new use rule (SNUR) under the authority of
TSCA. (October 27, 2010; 75 FR 65987).  Under 40 CFR part 721, EPA may
issue a SNUR where the Agency determines that activities other than
those described in the premanufacture notice may result in significant
changes in human exposures or environmental release levels and that
concern exists about the substance’s health or environmental effects. 
Manufacturers, importers and processors of substances subject to a SNUR
must notify EPA at least 90 days before beginning any designated
significant new use through a significant new use notice (SNUN).  EPA
has 90 days from the date of submission of a SNUN to decide whether the
new use "may present an unreasonable risk" to human health or the
environment.  If the Agency does not determine that the new use “may
present an unreasonable risk,” the submitter would be allowed to
engage in the use, with or without certain restrictions.  The
significant new uses identified in the SNUR for HFO-1234yf are:  (1) use
other than as a refrigerant in motor vehicle air conditioning systems in
new passenger cars and vehicles; (2) commercial use other than in new
passenger cars and vehicles in which the charging of motor vehicle air
conditioning systems with HFO-1234yf was done by the motor vehicle OEM;
and (3) distribution in commerce of products intended for use by a
consumer for the purposes of servicing, maintenance and disposal
involving HFO-1234yf. 

Under existing regulations in appendix D to subpart G of 40 CFR part 82,
“A refrigerant may only be used with the fittings and can taps
specifically intended for that refrigerant and designed by the
manufacturer of the refrigerant.  Using a refrigerant with a fitting
designed by anyone else, even if it is different from fittings used with
other refrigerants, is a violation of this use condition.”  The
manufacturer and submitter for HFO-1234yf has provided unique fittings
for the high-pressure side and for the low-pressure side of the MVAC
system and for large cylinders for professional use (typically 20 lb or
more).  Therefore, until the manufacturer provides unique fittings to
EPA’s SNAP Program for use with can taps or other small containers for
consumer use and until EPA publishes a final rule identifying such
unique fittings, it would be a violation of the use condition in
appendix D to use HFO-1234yf in small cans or containers for MVAC. 
Before issuing a rule allowing use of HFO-1234yf with fittings for small
cans or containers for MVAC, we would first need to conclude through
either review under TSCA or under the SNAP program that use of these
smaller canisters would not pose an unreasonable risk to consumers.  

In our review of consumer risks from HFO-1234yf, we considered
information concerning consumer exposure to HF from thermal
decomposition or combustion of HFO-1234yf.  EPA’s analysis at the time
of the proposed rule focused on the flammability risk to consumers,
which at the time we believed to be a significant risk in its own right,
as well as a way to prevent consumer exposure to HF from combustion of
HFO-1234yf.  However, in preparing our proposal, we had available and
did consider the SAE CRP’s 2008 evaluation of scenarios that might
cause consumer or occupational exposure to HF (CRP, 2008).  This report
stated:

Decomposition of HFO-1234yf in a fire scenario might, in theory, pose a
significant acute health risk to passengers or firemen.  But in the
event of a fire, other toxic chemicals will be produced by combustion of
other automotive components and thus decomposition of the refrigerant
may increase the risk for fire fighters and would not introduce an
entirely new type of hazard.  It is also anticipated that only a small
portion of the refrigerant charge will be converted to these
decomposition products.  In U.S. EPA's assessment of risk of R-152a and
CO2 (R-744), the agency cited a study by Southwestern Laboratories which
indicated that a 100% R-134a atmosphere only produced an HF
concentration of 10 ppm when passed through a tube heated to 1,000 ºF
(Blackwell et al., 2006). A search of the medical literature also did
not reveal any published reports of injuries to fire fighters or vehicle
passengers resulting from exposures to COF2 or HF produced in fires
involving refrigerants.  (EPA-HQ-OAR-2008-0664-0008, p. 67)

After the SAE CRP’s 2008 evaluation, SAE CRP members conducted tests
to measure HF concentrations and to identify factors that were most
likely to lead to HF formation (EPA-HQ-OAR-2008-0664-0056.2).  One test
on HF concentrations inside a car cabin found maximum concentrations
were in the range of 0 to 35 ppm in trials both with HFO-1234yf and with
HFC-134a, with concentrations dropping to 10 ppm or less after 10
minutes.  In a second test of HF generated in the engine compartment, HF
concentrations from thermal decomposition of HFO-1234yf reached as high
as 120 ppm in the engine compartment in the worst case, with interior
passenger cabin values of 40 to 80 ppm.  Under the same extreme
conditions (flash ignition, temperature of 700 °C, closed hood), HF
concentrations from thermal decomposition of HFC-134a reached 36.1 ppm
in the engine compartment with interior passenger cabin values of 2 to 8
ppm.  The other trials with less extreme conditions found HF
concentrations from HFO-1234yf in the engine compartment of 0 to 8 ppm. 


The SAE CRP selected an Acute Exposure Guideline Limit (AEGL)-2 of 95
ppm over 10 minutes as its criterion for determining toxicity risk from
HF.  Thus, even assuming levels inside a passenger compartment reached
the highest level that occurred during the tests – 80 ppm –  a
passenger inside a vehicle would at worst experience discomfort and
irritation, rather than any permanent effects.  HF levels that could
result in similar effects were also observed for HFC-134a.  The SAE CRP
concluded that the probability of such a worst-case event is on the
order of 10-12 occurrences per operating hour
(EPA-HQ-OAR-2008-0664-0056.2).  This level of risk is similar to the
current level of risk of HF generated from HFC-134a
(EPA-HQ-OAR-2008-0664-0086.1).  To date, EPA is unaware of any reports
of consumers affected by HF generated by HFC-134a, which has been used
in automobile MVAC systems across the industry since 1993.  Thus, we do
not expect there will be a significant risk of HF exposure to consumers
from HFO-1234yf.

Depending on the charge size of an HFO-1234yf MVAC system, which may
range from as little as 400 grams to as much as 1600 grams (ICF, 2008),
it is possible in a worst case scenario to reach a flammable
concentration of HFO-1234yf inside the passenger compartment.  This
could occur in the case of a collision that ruptures the evaporator in
the absence of a switch or other engineering mitigation device to
prevent flow of high concentrations of the refrigerant into the
passenger compartment, provided that the windows and windshield remain
intact.  As stated in the SAE CRP, ignition of the refrigerant once in
the passenger cabin is unlikely (probability on the order of 10-14
occurrences per operating hour) because the only causes of ignition
within the passenger cabin with sufficient energy to ignite the
refrigerant would be use of a butane lighter (EPA-OAR-2008-0664-0056.2).
 If a passenger were in a collision, or in an emergency situation, it is
unlikely that they would choose to operate a butane lighter in the
passenger cabin.  Additionally, it is unlikely ignition would occur from
a flame from another part of the vehicle because automobiles are
constructed to seal off the passenger compartment with a firewall.  If a
collision breached the passenger compartment such that a flame from
another part of the vehicle could reach it, that breach would also
create ventilation that would lower the refrigerant concentration below
the lower flammability limit.  Similarly, if either a window or the
windshield were broken in the collision, the ventilation created would
lower the refrigerant concentration below the lower flammability limit. 
Therefore, EPA finds that flammability risks of HFO-1234yf to passengers
inside a vehicle will be low.  Further, these risks are likely to be
less than those from HFC-152a, another flammable refrigerant that EPA
has previously found acceptable subject to use conditions, because
HFC-152a has a lower LFL and a lower minimum ignition energy than
HFO-1234yf (EPA-HQ-OAR-2008-0664-0008, -0013.4, -0056.2).

Overall conclusion

EPA finds that the use of HFO-1234yf in new passenger vehicle and
light-duty truck MVAC systems, subject to the use conditions being
adopted in the final rule, does not present a significantly greater risk
to human health and the environment compared to the currently-approved
MVAC alternatives or as compared to CO2, which has been proposed for
approval in this end-use. 

VI.	What is the relationship between this SNAP rule and other EPA rules?

Significant New Use Rule

Under the Toxics Substances Control Act, EPA has issued a Significant
New Use Rule (75 FR 65987; October 27, 2010) for 1-propene,
2,3,3,3-tetrafluoro-, which is also known as HFO-1234yf.  This rule
requires persons who intend to manufacture, import, or process
HFO-1234yf for a use that is designated as a significant new use in the
final SNUR to submit a SNUN at least 90 days before such activity may
occur.  EPA has 90 days from the date of submission of a SNUN to decide
whether the new use "may present an unreasonable risk" to human health
or the environment.  If the Agency does not determine that the new use
“may present an unreasonable risk,” the submitter would be allowed
to engage in the use, with or without certain restrictions.  The
significant new uses identified in the final SNUR and subject to the
SNUN requirement are:  use other than as a refrigerant in motor vehicle
air conditioning systems in new passenger cars and vehicles; commercial
use other than in new passenger cars or vehicles and in which the
charging of motor vehicle air conditioning systems with HFO-1234yf was
done by the motor vehicle OEM; and distribution in commerce of products
intended for use by a consumer for the purpose of servicing, maintenance
and disposal involving HFO-1234yf.  The health concerns expressed in the
final SNUR are based primarily on potential inhalation exposures to
consumers during “do-it-yourself” servicing, as well as a number of
other relevant factors.  

B.	Rules under Sections 609 and 608 of the Clean Air Act

Section 609 of the CAA establishes standards and requirements regarding
servicing of MVAC systems.  These requirements include training and
certification of any person that services MVAC systems for
consideration, as well as standards for certification of equipment for
refrigerant recovery and recycling.  EPA has issued regulations
interpreting this statutory requirement and those regulations are
codified at 40 CFR part 82 subpart B.  The statutory and regulatory
provisions regarding MVAC servicing apply to any refrigerant alternative
and are not limited to refrigerants that are also ODS.  This final SNAP
rule addresses the conditions for safe use of HFO-1234yf in new MVAC
systems.  Thus, the requirements in this rule apply primarily to OEMs,
except for specific requirements for service fittings unique to
HFO-1234yf.  MVAC end-of-life disposal and recycling specifications are
covered under section 608 of the CAA and our regulations issued under
that section of the Act.

VII. What is EPA’s response to public comments on the proposal?

This section of the preamble summarizes the major comments received on
the October 19, 2009 proposed rule.  Additional comments are addressed
in a response to comments document in docket EPA-HQ-OAR-2008-0664.

Acceptability decision

Comment:  Several commenters supported EPA’s proposal to find
HFO-1234yf an acceptable substitute for CFC-12 in MVACs.  These
commenters stated that available information indicates that HFO-1234yf
will not pose significant health risks or environmental concerns under
foreseeable use and leak conditions and that it has a strong potential
to reduce greenhouse gas emissions from motor vehicles.  Also, these
commenters declared that HFO-1234yf’s risks were similar to or less
than those of other available alternatives, such as HFC-134a, HFC-152a,
and CO2.  A commenter referenced the work of the SAE CRP, which
concluded that HFO-1234yf can be used safely through established
industry practices for vehicle design, engineering, manufacturing, and
service.  

Other commenters opposed finding HFO-1234yf acceptable or stated that
there was insufficient information to support a conclusion.  These
commenters stated that the risks of HFO-1234yf were greater than those
of other available alternatives, such as HFC-134a, CO2, and
hydrocarbons.

Response:  For the reasons provided in more detail above, EPA has
determined that HFO-1234yf, if used in accordance with the adopted use
conditions, can be used safely in MVAC systems in new passenger vehicles
and light-duty trucks.  The use conditions established by this final
rule ensure that the overall risks to human health and the environment
are comparable to or less than those of other available or potentially
available substitutes, such as HFC-134a, HFC-152a, or CO2.  EPA did not
compare the risks to those posed by hydrocarbons since we have not yet
received adequate information for hydrocarbons that would allow us to
make such a comparison for use in MVAC.

Comment:  Some commenters suggested that EPA should consider other
substitutes for CFC-12 in MVAC, such as CO2 or hydrocarbons.  An
organization representing the automotive industry stated that the risks
from using CO2 in MVAC systems are below the probability of other
adverse events which society considers acceptable and are roughly 1.5
orders of magnitude greater than the risks from using HFO-1234yf.

Response:  This rule only concerns EPA’s decision on the use of
HFO-1234yf in new passenger vehicles and light-duty trucks.  In a
separate action, EPA has proposed to find CO2 acceptable subject to use
conditions as a substitute for CFC-12 in MVAC systems for new motor
vehicles (September 16, 2006; 71 FR 55140).  We anticipate taking final
action on that proposal shortly.  We currently have inadequate
information on hydrocarbons to consider adding them to the list of
substitutes for MVAC.  We will review additional substitutes if they are
submitted with complete and adequate data to allow an evaluation of
whether such substitutes may be used safely within the meaning of
section 612 of the CAA as compared with other existing or potential
substitutes in the MVAC end-use.  

 Use conditions

Comment:  Several commenters stated that the proposed use conditions
limiting concentrations of HFO-1234yf below the lower flammability limit
are overly stringent or even impossible to meet and are not needed for
safe usage.  Some automobile manufacturers suggested relying upon
established standards and practices, such as SAE protocols and
standards, instead of use conditions.  Some commenters suggested
alternative language for use conditions.  Other commenters expressed
concern that the proposed use conditions limiting concentrations of
HFO-1234yf would preclude the use of HFO-1234yf by any vehicle that is
not initially designed to use this refrigerant.

Response:  As described above, EPA agrees that the use conditions, as
proposed, require modification.  In this final rule, we have removed the
first three proposed use conditions, which required design to keep
refrigerant concentrations below the LFL.  See section IV of the
preamble, “What are the final use conditions and why did EPA finalize
these conditions?” for our basis.  With respect to the commenter who
suggested that the proposed use conditions limiting concentrations of
HFO-1234yf below the LFL would not allow use except in systems initially
designed to use this refrigerant, we note that this decision is limited
to use in new motor vehicles and light-duty trucks.  Further, the
proposed use conditions limiting refrigerant concentration are not
included in the final rule and thus do not have implications for a
future decision concerning retrofits. 

Comment:  One commenter provided test results from the Bundesanstalt
fuer Materialforschung und –pruefung (BAM—Federal Institute for
Materials Research and Testing) that tested various mixtures of
HFO-1234yf and ethane (EPA-HQ-OAR-2008-0664-0053.3).  The commenter
stated that the tests show that explosions can occur at HFO-1234yf
concentrations below its lower flammability limit (LFL) of 6.2% when
minimal amounts of gaseous hydrocarbons are available.  This commenter
stated that the maximum concentrations of HFO-1234yf allowed under any
use condition need to be far below the 6.2% LFL to ensure safety.  Other
commenters agreed with these concerns.  Yet other commenters looked at
the same test data and stated that the testing was not relevant to
real-world situations in MVAC because it is unlikely that such large
amounts of ethane or other gaseous hydrocarbons (0.8-2.4% by volume)
would form in a vehicle.  One commenter stated that HFO-1234yf reduces
the flammability of ethane compared to ethane alone, and that HFO-1234yf
reduces flammability of ethane more than CO2 or argon, substances used
as fire suppressants (EPA-HQ-OAR-2008-0664-0115.1).

Response:  We do not believe that the BAM testing of the flammability
limits of mixtures of HFO-1234yf and ethane is relevant to assessing the
risks of HFO-1234yf as a refrigerant in MVAC.  Examples of flammable
substances in the engine compartment may include compressor oil mixed
with the refrigerant, motor oil, cleaners, anti-freeze, transmission
fluid, brake fluid, and gasoline.  These are typically liquid and there
is no evidence that any vapors that might form would include significant
amounts of ethane.  These fluids typically contain larger molecules with
higher boiling points than ethane (e.g., octane, polyalkalene glycol). 
It seems more likely, as one commenter suggested, that these flammable
fluids would ignite before breaking down into concentrations of ethane
considered in the BAM testing.  Further, the results of the testing are
not surprising; based on a scientifically known chemical equilibrium
principle known as Le Chatelier’s principle--the lower flammability
limit of a mixture of two flammable substances falls between the lower
flammability limit of the two individual substances.  The range of
flammable mixtures of ethane and refrigerants HFC-134a, HFO-1234yf, and
CO2 is largest for CO2 and is similar for HFC-134a and HFO-1234yf
(Besnard, 1996).

A more relevant test to compare risks for HFO-1234yf and other
alternative refrigerants in MVAC is to consider flammability of a
mixture of compressor oil and refrigerant, as occurs in MVAC systems. 
Such testing, conducted as part of the SAE CRP, found that mixtures of
HFO-1234yf and 5% oil and HFC-134a and 5% oil both ignited at
temperatures higher than what usually occurs in a vehicle (730 ºC or
higher for HFO-1234yf and 800 ºC or higher for HFC-134a).  

Furthermore, we note that the final use conditions do not rely on the
lower flammability limit.  As explained in more detail in sections IV
and V of the preamble, “What are the final use conditions and why did
EPA finalize these use conditions?” and “Why is EPA finding
HFO-1234yf acceptable subject to use conditions?”, we believe that the
risks from HFO-1234yf and its decomposition products are very small and
are comparable to or less than the risks from other acceptable
alternatives available or potentially available for use in MVAC systems.
 The use conditions established in the final rule require manufacturers
to design the system to prevent leakage from refrigerant system
connections that might enter the passenger cabin, and to minimize
impingement of refrigerant and oil onto hot surfaces.  These use
conditions will further reduce already low risks from flammability and
HF generation.  

Comment:  One commenter provided data from a presentation showing that
the lower flammability limit of HFO-1234yf decreases as temperature
increases.  The commenter stated that the proposed LFL of 6.2% may not
be conservative enough. 

Response:  EPA agrees that the LFL decreases as temperature increases. 
However, for the analysis relied on for the proposed rule, we considered
an LFL relevant to the temperatures that might be expected in a
collision or leak scenario and that would not be so high as to be a
higher risk factor than exposure to HF.  The data provided by the
commenter show an LFL of 5.7% at 60 ºC (140 ºF) and an LFL of 5.3% at
100 ºC (212 ºF).  If a passenger were exposed to temperatures this
high in the passenger compartment for any extended period of time, he or
she would suffer from the heat before there was a risk of the
refrigerant igniting.  However, after considering the available
information, we find it is not necessary to require a concentration of
HFO-1234yf below the LFL to address this refrigerant’s risks; rather,
risks are sufficiently addressed with the final use conditions.  As
discussed above in section IV of the preamble, “What are the final use
conditions and why did EPA finalize these conditions?”, we believe
that the flammability risks from HFO-1234yf are very small and overall
risks from HFO-1234yf are comparable to or less than the risks from
other acceptable alternatives used in MVAC.  EPA finds that the use
conditions in this final rule are sufficient to manage risks of injury
or adverse health effects caused by HFO-1234yf. 

Comment:  Regarding the first proposed use condition that would limit
the concentration of HFO-1234yf below the LFL in the passenger cabin,
several commenters stated that the risks of refrigerant leaking into the
passenger compartment and exceeding the LFL are very low.  Some
automobile manufacturers stated that it may not be possible to keep the
concentration below the LFL in the event of a collision; however, the
commenters said that even if concentrations in the passenger cabin
exceeded the LFL, it would be extremely difficult to ignite the
refrigerant.  Some commenters stated that the engineering strategies
that would be necessary to implement the proposed use condition would
actually increase overall risk by increasing the risk of conveying smoke
and fumes from the engine compartment into the passenger compartment in
the event of an accident.  Some commenters suggested alternative
language for the use condition to give greater flexibility in
engineering responses to allow for differences between vehicles.  

Response:  As discussed above in section IV of the preamble, EPA is not
including the proposed use condition requiring that a specific level of
refrigerant concentration inside the passenger cabin is not exceeded.  

	Comment:  One commenter suggested that the use conditions for limiting
concentrations in the passenger cabin should require the incorporation
of engineering strategies and/or devices “such that foreseeable
leaks” rising to the specified concentration levels can be avoided. 
Similarly, the commenter stated that any use condition limiting
concentrations in the engine compartment should be limited to
“prevention of ignition caused by foreseeable leaks.”  The commenter
noted that EPA did this in a similar use condition in its final SNAP
rule for HFC-152a, another flammable refrigerant for MVAC with greater
flammability risk.  The commenter stated that this would be consistent
with safety requirements of the National Highway Traffic Safety
Administration (NHTSA) and would ensure that EPA’s use conditions are
feasible.

Response:  As discussed above in section IV of the preamble, EPA is not
including the proposed use condition and is not limiting the refrigerant
concentration inside the passenger cabin or the engine compartment.  

Comment:  A number of commenters did not support the proposed use
condition on concentrations of HFO-1234yf in hybrid and electric
vehicles.  One commenter recommended eliminating this use condition, as
the SAE CRP risk assessment concludes there are no real world safety
risks.  Another commenter suggested referring to the SAE or ISO
(International Organization for Standardization) standards in place of a
specific use condition.  One commenter stated that electric terminals on
hybrid vehicles are well protected to prevent fires and should not
ignite the refrigerant.  Another commenter stated that an accident
severe enough to cause refrigerant leakage would also result in damage
to the duct between the evaporator [in the MVAC system] and the battery
pack, preventing an increase in refrigerant concentrations at the
battery pack.  One commenter stated that it is difficult to establish
generic SNAP use conditions for hybrid vehicles, and individual
manufacturers need to understand particular design features of their
hybrid vehicles to ensure safe refrigerant application.

Three commenters expressed concern for using HFO-1234yf in hybrid and
electric vehicles and stated that the use condition is not conservative
enough.  One commenter stated that the maximum concentrations of
HFO-1234yf need to be far below the 6.2% LFL based on new tests done at
the Federal Institute for Materials Research and Testing (BAM) and that
they are unsure whether or not additional measures can effectively avoid
the risk of explosive mixtures.  Another commenter stated that
HFO-1234yf would raise concerns in the field of battery cooling needed
in electric vehicles because flammability and chemical reactions would
pose major risks, which could lead to legal consequences for OEMs.

Response:  As discussed above in section IV of the preamble, EPA is not
including the proposed use condition and is not requiring protective
devices, isolation and/or ventilation techniques where levels of
refrigerant concentration may exceed the LFL in proximity to exhaust
manifold surfaces or near hybrid or electric vehicle power sources.  As
discussed above, we do not believe that the BAM testing of the
flammability limits of mixtures of HFO-1234yf and ethane is relevant to
assessing the risks of HFO-1234yf as a refrigerant in MVAC.  Based on
information provided by OEMs that manufacture hybrid vehicles, we
conclude that there will be sufficient protection against fire risk and
generation of HF in the engine compartment for hybrid vehicles because
they have protective coverings on power sources that will prevent any
sparks that might have enough energy to ignite refrigerant and engine
surfaces will not be hotter than those in conventional vehicles
(EPA-HQ-OAR-2008-0664-0081.1, -0081.2).  Further, we agree that it is
reasonable to assume that a collision severe enough to release
refrigerant from the evaporator (under the windshield) would also
release it in a location far enough away from the battery pack to keep
down refrigerant concentrations at the battery pack below the LFL.  CFD
modeling performed for the December, 2010 SAE CRP risk assessment found
that concentrations of HFO-1234yf only exceeded the LFL within ten
centimeters of the leak or less (EPA-HQ-OAR-2008-0664-0056.2), but the
battery pack is typically placed more than ten centimeters away from the
evaporator.  EPA expects that OEMs will include assessment of risks from
the exhaust manifold, hybrid power source, and electric vehicle power
source as part of the FMEA required under one of the final use
conditions in this rule. 

Comment:  Some commenters responded to EPA’s request for comment as to
whether the use conditions should apply only when the car ignition is
on.  These commenters indicated that it is unnecessary for the use
conditions on refrigerant concentrations within the passenger
compartment to apply while a vehicle’s ignition is off because it is
unlikely that a collision would occur, that high temperatures would
occur, or that refrigerant would enter the passenger cabin when the
ignition, and thus the MVAC system, is off.  Another commenter stated
that it should be mandatory for all electric power sources to be shut
off when the ignition is off. 

Response:  As discussed above in section IV of the preamble, EPA is not
including the proposed use conditions that specified a refrigerant
concentration not to be exceeded.  

Comment:  Several commenters stated that the proposed limits on
concentrations of HFO-1234yf in the engine compartment cannot be met,
even hypothetically, and that imposition of such a use condition would
delay or even prevent the use of HFO-1234yf.  Other commenters stated
that the engineering required to meet the proposed use condition is
almost certain to preclude the use of HFO-1234yf by any vehicle that was
not initially designed to use this refrigerant.

Response:  EPA is not including in the final rule the proposed use
condition that sets a specific limit for refrigerant concentrations
inside the engine compartment.  See section IV of the preamble, “What
are the final use conditions and why did EPA finalize these
conditions?” for further rationale.  

Comment:  Several commenters agreed with EPA’s proposal to have unique
fittings and a warning label that identify the new refrigerant and
restrict the possibility of cross-contamination with other refrigerants.
 Other commenters suggested that no use conditions are necessary because
established standards and practices would be adequate for safe use of
HFO-1234yf.

Response:  The use conditions referenced by the commenters were
established in a separate final rule, promulgated in 1996, which applies
to all refrigerants used in MVAC (see appendix D to subpart G of 40 CFR
part 82).  EPA has not proposed to modify that existing rule for
purposes of its acceptability determination for HFO-1234yf.  These
requirements indicate to technicians the refrigerant they are using and
thus help reduce risks to the technician by ensuring that the technician
will handle the refrigerant properly.  In addition, these use conditions
serve to prevent contamination of refrigerant supplies through
unintended mixing of different refrigerants.  For purposes of meeting
that existing regulatory requirement, this final rule specifies use of
fittings for the high-pressure side service port, the low-pressure side
service port, and for refrigerant containers of 20 pounds or greater. 
The submitter for HFO-1234yf has provided these fittings to the Agency
and they are consistent with the draft SAE standard J639.  In addition,
the final rule retains the requirement for a warning label identifying
the refrigerant, consistent with both the current (2005) edition of SAE
J639 and the current draft version. 

Comment:  Some commenters agreed with EPA’s proposal to have a
high-pressure compressor cut-off switch, as per SAE J639.  Another
commenter suggested that the compressor cut-off switch would be useful
for all systems if the discharge pressure can reach the burst pressure,
not just those systems with pressure relief devices.

Response:  EPA is including as a final use condition the requirement
that HFO-1234yf MVAC systems must have a high-pressure compressor
cut-off switch.  The use condition requires a pressure relief device on
the high-pressure side of the compressor for all MVAC systems using
HFO-1234yf, and so the compressor cut-off switch will be required for
all systems using HFO-1234yf, as suggested by the commenter. 

Comment:  Several commenters supported the requirement for vehicle
makers to conduct and maintain FMEAs.  Other automobile manufacturers
stated that the final SNAP rule finding HFC-152a acceptable as a
substitute for CFC-12 in MVAC included this as a comment rather than as
a use condition, and suggested that EPA do the same in the final rule
for HFO-1234yf.  Another commenter stated that FMEAs for each vehicle
design are standard industry practice, and so no use condition is
required; this commenter provided language for an alternate use
condition should EPA choose to specify a use condition for vehicle
design.

Response:  EPA is retaining the requirement for FMEAs in the final rule
as a use condition, rather than simply as an unenforceable comment.  In
an FMEA, vehicle designers analyze all the ways in which parts of the
MVAC system could fail and identify how they will address those risks in
design of the system.  In addition, keeping records of an FMEA is
important to ensuring safe use because it documents that vehicle
designers have complied with the safety requirements of this rule.  We
believe that it is necessary to retain this requirement as a use
condition in order to ensure that OEMs are required to analyze and
address the risks and to document those efforts such that this analysis
is available to demonstrate compliance to EPA in case of an EPA
inspection.  Information in the FMEAs complements the use conditions of
this rule and is useful for demonstrating compliance.  

Comment:  A commenter requested that EPA specifically allow
manufacturers to perform FMEAs according to equivalent standards
developed by organizations other than SAE (e.g., the International
Organization for Standardization [ISO], the German Institute for
Standards [DIN], or the Japan Automobile Manufacturers Association
[JAMA]).

Response:  We agree that standards from other standard-setting
organizations may provide equivalent assurance of safe use.  However, we
are not aware at this time of any standards that do so.  In order to
ensure safe use of HFO-1234yf, we would need to review any other
standard to ensure that it provides equivalent assurances of safety
before allowing its use in place of the SAE standard.  An OEM, for
example, could petition EPA’s SNAP program and provide copies of the
other standard for consideration.  If we agree that the other standard
is equivalent, then we would add it to the use condition on FMEAs
through a rulemaking.

Comment:  A commenter expressed that EPA’s approach to setting use
conditions impedes upon the Department of Transportation’s motor
vehicle safety jurisdiction and that EPA does not have the authority to
protect against any fire risk associated with motor vehicles.

Response:  As an initial matter, we note that the commenter does not
point to any specific legislative authority that supports his claim. 
Regardless, EPA disagrees with this commenter.  Section 612 of the CAA
provides that EPA may find substitutes for ODS acceptable if they
present less risk to human health and the environment than other
substitutes that are currently or potentially available.  Congress did
not establish any limits on EPA’s authority for ensuring that
substitutes are not more risky than other substitutes that are available
and EPA has consistently interpreted this provision to allow the Agency
to establish use conditions to ensure safe use of substitutes.  In this
case, we find that HFO-1234yf may be used safely, and with risks
comparable to or less than those of other available substitutes for
CFC-12 in the MVAC end-use, so long as it is used according to the use
conditions established by this action.  If the commenter were correct
that the Department of Transportation (DOT) has sole authority to
address fire risk from MVAC systems, in the absence of such standards
from DOT, EPA would need to determine that HFO-1234yf is unacceptable
for use in MVACs. 

  Environmental impacts

Ozone Depletion Potential

Comment:  Several commenters agreed with EPA’s proposed finding that
HFO-1234yf would not contribute significantly to stratospheric ozone
depletion, and that the ozone depletion potential (ODP) of HFO-1234yf is
at or near zero.  Two commenters claimed that the ODP of HFO-1234yf
should be stated as “zero” instead of “nearly zero,” and one
commenter requested that EPA clarify that HFO-1234yf has an ODP less
than that of HFC-134a. 

Other commenters disagreed with EPA’s statement that the ODP of
HFO-1234yf is at or near zero.  One commenter expressed concern that ODS
may be used in the HFO-1234yf manufacturing process, or emissions of
HFO-1234yf and its by-products from the manufacturing process may break
down into gases with ODPs; this commenter advised EPA against listing
HFO-1234yf as an acceptable replacement for HFC-134a in MVACs.  Another
commenter stated that HFO-1234yf requires further investigation since
unsaturated HFCs such as HFO-1234yf might break down into gases that are
ozone depleting. 

Response:  It is generally agreed among scientists that substances that
contain chlorine, bromine or iodine may have an ozone depletion
potential while those that contain only fluorine effectively have no
ODP.  In particular, this is because the CF3 radical produced from HFCs
has negligible reactivity (Ravishankara et al., 1993); the same radicals
would be expected from HFO-1234yf.  HFO-1234yf contains no chlorine,
bromine, or iodine.  Also, the atmospheric lifetime of HFO-1234yf is
estimated at only 11 to 12 days (Orkin et al., 1997; Papadimitrou et
al., 2007), further reducing the amount of the chemical that could
possibly reach the stratosphere.  Unsaturated HFCs, such as HFO-1234yf,
have at least one double bond or triple bond between two carbon atoms. 
Double bonds, like those in HFO-1234yf, are less stable than single
bonds.  A saturated HFC, such as HFC-134a, has only single bonds between
atoms of carbon, and is thus more stable.  Although HFO-1234yf may be
more unstable than HFC-134a, EPA is not aware of any chemical reactions
or decomposition pathways that would cause HFO-1234yf or its breakdown
products to lead to ozone depletion and the commenter has provided no
technical or scientific support for their claims.  For purposes of our
determination, whether its ODP is zero or nearly zero, we expect
HFO-1234yf to have negligible impact on the ozone layer and we are
listing it as acceptable, subject to use conditions.

  Global Warming Potential

Comment:  Several commenters agreed with EPA’s statement that
HFO-1234yf has a global warming potential (GWP) of 4 over a 100-year
time horizon.  Some commenters noted the potential environmental
benefits of having a lower GWP refrigerant available.  Other commenters
stated that HFO-1234yf would not be a solution to high global warming
impacts because of environmental and health impacts of breakdown
products, including HF, trifluoroacetic acid (TFA), and aldehydes.  

Response:  EPA continues to believe that the 100-yr GWP of HFO-1234yf is
4, as supported by the commenters.  We further agree with the commenters
who state that there will be an environmental benefit if car
manufacturers switch to HFO-1234yf from HFC-134a, a refrigerant with a
GWP of 1430 relative to CO2.  

We disagree with the commenters who claim that environmental and health
impacts of breakdown products is a major cause for concern or will
prevent HFO-1234yf from being a useful solution to high global warming
impacts.  One commenter mentioned concerns about HF in the atmosphere,
but HFO-1234yf does not decompose to form significant amounts of HF in
the atmosphere.  In fact, HFC-134a and HFC-152a result in more HF in the
atmosphere than HFO-1234yf because those two compounds decompose to form
both COF2, carbonyl fluoride (and then HF and CO2) and CF3COF,
trifluoroacetyl fluoride (and then TFA); in contrast, HFO-1234yf favors
forming trifluoroacetyl fluoride (and then TFA) and does not decompose
to carbonyl fluoride or to HF (ICF, 2010d).  For a discussion on the
potential human health impacts of HF, see sections V and VII.D.3, “Why
is EPA finding HFO-1234yf acceptable subject to use conditions?“ and
“Toxicity of Hydrogen Fluoride.”  

The fluorinated breakdown product that we have identified of greatest
concern is TFA, because of its persistence and potential impacts on
aquatic plants.  As discussed above in section V and below in section
VII.C.5, “Formation of Trifluoroacetic Acid and Ecosystem Impacts,”
the projected concentrations of TFA, based on a conservative analysis,
will be far below the level expected to cause any adverse impacts on
aquatic life.  

EPA agrees that the breakdown products from the decomposition of
HFO-1234yf will include aldehydes, but we disagree that this is a cause
for concern.  As part of the analysis of the atmospheric breakdown
products of HFO-1234yf, we found that worst-case concentrations of
formaldehyde would reach 6 to 8 parts per trillion (ppt) on a monthly
basis or an average of 3 ppt on an annual average basis, compared to a
health-based limit of 8000 ppt, i.e., a level that is roughly 1000 to
2600 times lower than the health-based limit (ICF, 2010d).  Acetaldehyde
levels would be even lower, with worst-case concentrations of 1.2 ppt
and annual average concentrations of 0.23 ppt, compared to a
health-based limit of 5000 ppt (ICF, 2010d).  As discussed further below
in section VII.D.1 of the preamble, “Toxicity of HFO-1234yf,” these
concentrations are one to three orders of magnitude less than ambient
concentrations of formaldehyde and acetaldehyde without the introduction
of HFO-1234yf (ICF, 2010d).  Thus, aldehydes that would be decomposition
products of HFO-1234yf in the atmosphere would not contribute
significantly to adverse health effects for people on earth’s surface.
 

Other fluorinated alternatives that are acceptable in the MVAC end-use,
HFC-134a and HFC-152a, also create fluorinated breakdown products, and
there is not evidence to show that those from HFO-1234yf create
significantly more risk for human health or the environment than
breakdown products from other alternatives.  Thus, even assuming that
risks from breakdown products would exist, based on use of HFO-1234yf in
the MVAC end-use, we do not believe those risks are greater than the
risks posed by other acceptable alternatives. 

Lifecycle Emissions of HFO-1234yf

Comment:  One commenter stated that HFO-1234yf has the best global
lifecycle climate performance (LCCP) and lower CO2 [equivalent]
emissions compared to other alternatives.  However, another commenter
stated that HFO-1234yf has a lower thermodynamic efficiency than
HFC-134a and that its use could lead to increases in CO2 and other air
pollutant emissions.  The same commenter stated that there is no
assurance that automakers would voluntarily add technologies to maintain
current levels of MVAC efficiency when using HFO-1234yf.

Response:  We note that EPA has chosen to use GWP as the primary metric
for climate impact for the SNAP program, while also considering energy
efficiency (March 18, 1994; 59 FR 13044).  We have not used specific
lifecycle metrics such as Total Equivalent Warming Impact (TEWI),
Lifecycle Analysis (LCA) or LCCP as metrics for climate impact, since it
is not clear that there is agreement in all industrial sectors or
end-uses on which of these measures is most appropriate in which
situations or how these metrics are to be calculated (SROC, 2005).

The available information on efficiency, LCCP and lifecycle emissions
for MVAC does not raise concern that the indirect climate impacts from
HFO-1234yf will cause significantly greater impacts on human health and
the environment than other available alternatives.  Looking at some of
the information referenced by the commenters, we learned that:

Bench testing for the Japan Automobile Manufacturers Association (JAMA)
and the Japan Auto Parts Industry Association (JAPIA) found a system
efficiency (coefficient of performance) for HFO-1234yf that is roughly
96% of that for HFC-134a (JAMA-JAPIA, 2008)

LCCP analysis conducted by JAMA found that indirect CO2 equivalent
emissions from less efficient fuel usage due to use of the MVAC system
were a few percent higher for HFO-1234yf and roughly 20 to 25% higher
for CO2, compared to HFC-134a (JAMA, 2008)

JAMA’s LCCP analysis found that when both direct emissions of
refrigerant and indirect emissions from less efficient fuel usage are
considered, HFC-134a has higher total climate impact than either
HFO-1234yf or CO2; in hotter climates like Phoenix, Arizona, HFC-134a
has higher total climate impact than HFO-1234yf but slightly lower
climate impact than CO2; and in all cases, HFO-1234yf had the lowest
total climate impact of the three alternatives. (JAMA, 2008)

MVAC systems can be designed to improve efficiency through steps such as
changing the compressor, sealing the area around the air inlet, changing
the thermal expansion valve, improving the efficiency of the internal
heat exchanger, adding an oil separator to the compressor, and changing
the design of the evaporator.  Optimized new MVAC systems using either
HFO-1234yf or CO2 can reduce fuel usage compared to current MVAC systems
using HFC-134a.  (Benouali et al., 2008; Meyer, 2008; Monforte et al.,
2008)

EPA believes that there is good reason to expect that automobile
manufacturers will choose to design new cars using more efficient MVAC
components and systems than in the past because of recent regulations. 
The Department of Transportation has issued new regulations raising the
Corporate Average Fuel Economy standards for vehicles and EPA has issued
new regulations restricting greenhouse gas emissions from light-duty
vehicles (75 FR 25324; May 7, 2010).  Thus, in order to ensure that
their fleets meet these standards, it is highly likely that automobile
manufacturers will include MVAC systems optimized for efficiency in
future models, regardless of the refrigerant used.

Comment:  Concerning an appropriate rate of emissions for estimating
environmental impacts of HFO-1234yf, three commenters recommended that
EPA use 50 g per vehicle per year total lifecycle emission rate.  These
commenters cited the work of Wallington et al. (2008) and Papasavva et
al. (2009). Another commenter stated that HFO-1234yf is very likely to
have a lower leak rate than HFC-134a, citing data on permeability for
both refrigerants. 

Response:  EPA agrees that the permeability data indicate that regular
leakage emissions of HFO-1234yf, which is released slowly through hoses,
is likely to be lower than those from HFC-134a.  However, this is only a
portion of total emissions expected because emissions may also come
through irregular leaks due to damage to the MVAC system, refrigerant
loss during servicing, and refrigerant loss at the end of vehicle life. 
In response to the commenters who suggested that we use an annual
emission rate of 50 g/vehicle/yr, we reexamined environmental impacts as
part of our final environmental analysis (ICF, 2010c) using the
recommended 50 g/vehicle/yr value and compared this to the impacts
calculated assuming emissions are similar to those from HFC-134a in
MVAC, as we did at the time of proposal (closer to 100 g/vehicle/yr). 
The emission values from  using 50 g/vehicle/yr (i.e., values from the
Pappasavva et al. (2009) study) were 26.3% to 51.1% less than the
emission estimates used in our analysis at the time of proposal (ICF,
2009; ICF, 2010a; ICF, 2010c).  In either case, as described more fully
in section V above and in sections VII.C.4 and VII.C.5, below, the
overall environmental impacts on generation of ground-level ozone and of
TFA were sufficiently low and the impacts of HFO-1234yf are not
significantly greater than those of other available substitutes for
MVAC.  For further information, see the ICF analyses in the docket (ICF,
2010a,b,c,e).

  Ground-Level Ozone Formation

Comment:  Some commenters expressed concern about a potential increase
in ground-level ozone of >1-4% calculated in EPA’s initial assessment
(ICF, 2009) of environmental impacts of HFO-1234yf.  Other commenters
stated that HFO-1234yf will not contribute significantly to ground-level
ozone.  One commenter suggested that EPA provide an updated assessment
of the potential contribution of HFO-1234yf to ground-level ozone,
considering the additional information provided in public comments
(e.g., Luecken et al., 2009 and Wallington et al., 2009).

Response: We proposed that HFO-1234yf would be acceptable, even with a
worst-case increase in ground-level ozone of >1 to 4%.  In response to
comments, EPA performed a new analysis that (1) used revised estimates
of  the expected emissions of HFO-1234yf; and (2) used reactions with
ozone formation from hydroxyl radicals rather than using sulfur dioxide
(SO2) as a surrogate for the hydroxyl radical, OH-, and rather than
making assumptions about the relative reactivity of compounds.  Our
revised analysis (ICF, 2010b) estimates that emissions of HFO-1234yf
might cause increases in ground-level ozone of approximately 0.08 ppb or
0.1% of the ozone standard in the worst case, rather than an increase of
1.4 to 4% as determined in our initial analysis (ICF, 2009).  This value
also agrees with results from Kajihara et al., 2010 and Luecken et al.,
2009.  This revised analysis provides additional support that HFO-1234yf
will not create significant impacts on ground level ozone formation or
on local air quality.

Comment:  Some commenters disagreed with EPA’s statement that
HFO-1234yf has a photochemical ozone creation potential (POCP)
comparable to that of ethylene (100), while others agreed with this
conclusion.  One commenter provided a peer reviewed study that estimated
the POCP of HFO-1234yf to be 7 (Wallington et al., 2010).  

Response:  Based on the comments received and additional studies, EPA
believes that the initial assessment that assumed a POCP of 100 to 300
is overly conservative.  We have revised our initial analysis to
incorporate reaction kinetics specific to HFO-1234yf, consistent with
Luecken et al., 2009, which avoids making an assumption of POCP. 
EPA’s revised analysis estimates worst-case increases in ground-level
ozone formation of approximately 0.1% (ICF, 2010b).  Compared to the
uncertainty in the sources of emissions, the uncertainty in the measures
that localities will take to meet the ozone standard, and the
uncertainty in the analysis, a projected worst-case increase in ozone of
0.1% is not significant for purposes of determining that HFO-1234yf
poses substantially greater human health or environmental risk than
other alternatives.  This provides further support for our proposed
determination that the conditioned use of HFO-1234yf does not present a
significantly larger risk to human health and the environment compared
to HFC-134a, and in many cases likely poses less risk.  For further
information, see the analysis of environmental impacts in section V of
the preamble, “Why is EPA finding HFO-1234yf acceptable subject to use
conditions?” and see the analysis in the docket (ICF, 2010b).

Comment:  A commenter provided a link to a paper (Carter, 2009) that
found the maximum incremental reactivity (MIR) for HFO-1234yf to be
about the same as that for ethane.  Based on the MIR value for
HFO-1234yf, some commenters stated that EPA should find HFO-1234yf to be
exempt from the definition of VOC.  

Response:  (Note:  EPA has previously found certain compounds exempt
from the definition of “volatile organic compound”[VOC] for purposes
of air regulations in State Implementation Plans, 40 CFR 51.100(s), if
they have a MIR equal to or less than that of ethane on a mass basis.
[69 FR 69298, November 29, 2004; 74 FR 29595, June 23, 2009; also see
interim EPA guidance at 70 FR 54046, September 13, 2005])  In a separate
rulemaking process, EPA is considering whether to list HFO-1234yf under
40 CFR 51.100(s) as exempt from the definition of VOC for purposes of
air regulations that States may adopt in State Implementation Plans.  

5.	Formation of Trifluoroacetic Acid and Ecosystem Impacts

Comment:  Several commenters agreed with EPA’s proposed finding that
the projected maximum concentration of TFA in rainwater from degradation
of HFO-1234yf does not pose a significant aquatic toxicity risk.  Other
commenters raised concern about the potential impacts of TFA on
biodiversity, ecosystems, and human health.  One commenter questioned
the sustainability of HFO-1234yf, so long as there are questions
remaining about its environmental fate and degradation.  One commenter
stated that artificial input of TFA into the environment should be
avoided because of its toxicity and chemical properties.  Another
commenter stated that HFO-1234yf poses additional environmental concerns
compared to HFC-134a and advised against finding it acceptable while the
issue of TFA production is being further researched.

Response:  We continue to conclude for purposes of our decision here
that the degradation of HFO-1234yf into TFA does not pose a significant
risk of aquatic toxicity or ecosystem impacts.  All available research
indicates that, assuming emissions are no more than twice the current
level of emissions from HFC-134a from MVAC, TFA concentrations in
surface water and rainwater will be on the order of 1/800th to 1/80th of
the no observed adverse effect level (NOAEL) for the most sensitive
known alga (Luecken et al., 2009; Kajihara et al., 2010).  We have
revised our analysis on TFA concentrations using the known reaction
kinetics of HFO-1234yf.  The revised estimate of the worst-case TFA
concentration in rainwater is approximately 1700 ng/L, similar to the
concentrations in Luecken et al. (2009) of 1260 ng/L and Kajihara et al.
(2010) of 450 ng/L.  We believe this provides a sufficient margin of
protection to find that the use of HFO-1234yf in MVAC will not pose
significantly greater risks than other available alternatives in this
end-use. 

Comment:  Some commenters stated that further research on TFA is
necessary.  

Response:  EPA has considered additional studies submitted during the
public comment period (Luecken et al., 2009; Kajihara et al., 2010) and
has performed further analysis on this issue.  Luecken et al. (2009)
predicted through modeling that in the U.S., HFO-1234yf used in MVAC
would result in enough TFA to increase its concentration in rainwater to
1/80th to 1/800th of the NOAEL for the most sensitive plant species
considered.  Kajihara et al. (2010) predicted through modeling that in
Japan, HFO-1234yf use in all potential refrigeration uses would increase
the TFA concentration in surface water to no more than 1/80th of the
NOAEL for the most sensitive plant species considered.  This study also
found that surface water concentrations were roughly twice those in
rainwater.  Thus, even with highly conservative modeling that also
considered accumulation in surface water, the concentrations of TFA are
likely to be at least 80 times lower than a level expected to have no
impact on the most sensitive aquatic species.

We also performed a further modeling analysis using refined assumptions
on emissions and the mechanisms by which HFO-1234yf might break down. 
We found that the worst-case concentration of TFA would be approximately
1700 ng/L, similar to the concentrations in Luecken et al. (2009) of
1260 ng/L and Kajihara et al. (2010) of 450 ng/L (ICF, 2010b).  These
additional studies and analyses indicate even less risk than the studies
available at the time of proposal and thus provide further support that
TFA emissions from MVAC system will not pose a significant risk of
aquatic toxicity or ecosystem impacts.  

We also note that EPA has an obligation to act on submissions in a
timely manner under the Clean Air Act (§612(d)).  Given that research
to date has not indicated a significant risk, we disagree that the
Agency should delay a final decision to await further studies that may
be done in the future.  If future studies indicate that HFO-1234yf poses
a significantly greater environmental risk than we now believe, section
612(d) provides a process for an interested party to petition the Agency
to change a listing decision.

Comment:  Two commenters stated that EPA’s initial modeling
(EPA-HQ-OAR-2008-0664-0037) greatly overestimates the local deposition
of TFA from oxidation of HFO-1234yf.  In particular, one commenter
claimed that the modeling’s use of the oxidation of SO2 to sulfate
ion, SO3-, as a proxy for the oxidation of HFO-1234yf is overly
conservative because a large portion of SO2 is in aerosol form, unlike
for HFO-1234yf.  This commenter also referred to the impacts found in
the peer-reviewed paper by Luecken et al. (2009).

Response:  EPA agrees that the use of the oxidation of SO2 to SO3- as a
proxy for the oxidation of HFO-1234yf likely results in overestimating
TFA concentrations.  This is because the sulfate particle is a
condensation nuclei in the wet deposition process and it has a very high
removal efficiency compared to the gas phase process for wet deposition
that acts with HFO-1234yf and its decomposition products.  Further, TFA
forms more slowly from HFO-1234yf than sulfate forms from SO2 (ICF,
2010b).  

We have repeated the modeling using refined assumptions on emissions and
the mechanisms by which HFO-1234yf might break down.  This revised
assessment (ICF, 2010b) found TFA concentrations roughly one-thousandth
those in the earlier assessment (1700 ng/L compared to 1,800,000 ng/L in
ICF, 2009).  This additional research provides stronger support for our
conclusion that the degradation of HFO-1234yf into TFA does not pose a
significant risk of aquatic toxicity or ecosystem impacts.

Comment:  Some commenters disagreed with a statement in the ICF (2009)
analysis concerning TFA concentrations in surface waters, that “the
exception to this is vernal pools and similar seasonal water bodies that
have no significant outflow capacity.”  These commenters believe that
Boutonnet et al. (1999) showed that accumulation of trifluoroacetate, a
compound closely related to TFA, was rather limited in seasonal water
bodies.  The commenters also stated that Benesch et al. (2002) conducted
an experimental study of the impacts of TFA on vernal pools, in which no
impacts were observed.  

Response:  The statement from ICF, 2009 in context stated:

NOECs [No-observed effect concentrations] were compared to rainwater TFA
concentrations because for most water bodies, it is difficult to predict
what the actual TFA concentration will be.  This is because
concentrations of environmental contaminants in most fresh water bodies
fluctuate widely due to varying inputs and outputs to most ponds, lakes,
and streams.  Comparison of NOECs to rainwater concentrations of TFA is
actually more conservative because TFA is expected to be diluted in most
freshwater bodies.  The exception to this is vernal pools and similar
seasonal water bodies that have no significant outflow capacity.  (ICF,
2009)

We note that the “exception” described in the analysis is an
exception to the expectation that TFA will be diluted more in freshwater
bodies that in rainwater.  We believe that the available evidence
confirms that vernal pools do not dilute TFA as much as freshwater
bodies with outflow capacity.  Modeling by Kajihara et al., 2010 found
surface water concentrations were roughly twice those in rainwater. 
However, even these concentrations were not high enough to be of
significant concern for environmental impacts.  As noted previously,
even the highest levels of TFA concentrations were at least 80 times
less that the NOAEL for the most sensitive aquatic species examined.  

Health and safety impacts

1.	Toxicity of HFO-1234yf

Comment:  Three commenters stated that there are no toxicity concerns
with using HFO-1234yf, and two commenters noted that HFO-1234yf is
comparable to HFC-134a in terms of human health effects.  One commenter
also stated that HFO-1234yf does not present a developmental toxicity or
lethality risk.  Six commenters stated that there are potential toxicity
concerns with use of HFO-1234yf.  One commenter cautioned EPA against
listing HFO-1234yf as acceptable for use in MVACs on the grounds of
increased concerns over developmental effects and other toxic effects on
human health. 

Response:  EPA continues to believe that HFO-1234yf, when used in new
MVAC systems in accordance with the use conditions in this final rule,
does not result in significantly greater risks to human health than the
use of other available or potentially available substitutes, such as
HFC-134a or CO2.  The results of most of the toxicity tests for
HFO-1234yf either confirmed no observed adverse health effects, or found
health effects at similar or higher exposure levels than for HFC-134a. 
For example, HFC-134a caused cardiac sensitization at 75,000 ppm but
HFO-1234yf did not cause cardiac sensitization even at 120,000 ppm, the
highest level in the study (NRC, 1996; WIL 2006).  NOAELs from subacute
exposure were higher for HFO-1234yf than for HFC-134a (NOAELs of 51,690
for HFO-1234yf with no effects seen in the study, compared to 10,000 ppm
for HFC-134a with lung lesions and reproductive effects seen at 50,000
ppm [NRC, 1996; TNO, 2005]).  No adverse effects were seen at 50,000 ppm
or any other level in subchronic (13-week) studies for both HFO-1234yf
and HFC-134a (NRC, 1996; TNO, 2007a).  

In mutagenicity testing for HFO-1234yf, the two most sensitive of five
strains of bacteria showed mutation; however, this screening test for
carcinogenic potential is known to have only a weak correlation with
carcinogenicity (Parodi et al., 1982; Kirkland et al., 2005), so a
positive result in this test for the two most sensitive strains is not
sufficient reason to consider HFO-1234yf to be a significant health
risk.  Mutagenicity testing for HFC-134a by the same test found no
evidence of mutagenicity.  Screening for carcinogenic potential in a
genomics study did not identify HFO-1234yf as a likely carcinogen
(Hamner Institutes, 2007).  A two-year cancer assay for HFC-134a did not
find evidence of carcinogenicity (NRC, 1996).  

EPA considers the results of developmental testing to date to be of some
concern, but not a sufficient basis to find HFO-1234yf unacceptable for
purposes of this action under the SNAP program.  In a developmental
study on rats, cases of wavy ribs were seen in some developing fetuses
during exposure to HFO-1234yf (TNO 2007b); however, effects on bone
formation were also seen for HFC-134a (NRC, 1996).  It is not clear if
this effect is reversible or not.  Interim results from a two-generation
reproductive study did not find an association between exposure to
HFO-1234yf and skeletal effects.  This two-generation reproductive study
for HFO-1234yf finds a NOAEL of 5000 ppm for delayed mean time to
vaginal opening in F1 females (females in the first generation of
offspring).  A subacute (28-day) test for HFC-134a (single generation)
found a NOAEL of 10,000 ppm for male reproductive effects (NRC, 1996). 
A developmental test on rabbits exposed to HFO-1234yf did not find
effects on the developing fetus.  However, some of the mother rabbits in
this study died.  The reason for the deaths is not known.  The data on
developmental effects are inconsistent depending on the test performed
and the species tested.  The development effects observed in the
developmental study on rats are not significantly different from the
developmental effects observed for HFC-134a.  In any case, as discussed
above in section V and below in this section, our risk assessments found
that HFO-1234yf would likely be used with exposure levels well below
those of concern in the uses allowed under this rule.  Thus, we do not
find the observed developmental effects sufficient reason for finding
HFO-1234yf unacceptable in this rule.

For purposes of this action, we prepared our risk assessment for
long-term exposure using the level at which no deaths or other adverse
health effects were seen in the rabbit developmental study—a “no
observed adverse effect level” or NOAEL—to ensure that exposed
people would be protected.  The longer-term, repeated exposure in that
study would be the exposure pattern (though not necessarily the exposure
level) for a worker using HFO-1234yf on a regular basis or for a
consumer exposed in a car due to a long, slow leak into the passenger
compartment.  Using the NOAEL concentration of 4000 ppm as a starting
point, we found no situations where we expect exposure to exceed the
level that EPA considers safe for long-term or repeated exposure
(EPA-HQ-OAR-2008-0664-0036).  Thus, we consider the potential toxicity
risks of HFO-1234yf for those uses allowed under this action to be
addressed sufficiently to list it as acceptable subject to use
conditions.

Comment:  Based on a risk assessment conducted by one commenter, the
commenter concluded that if HFO-1234yf is used under the conditions
specified in the commenter’s risk assessment, adverse health impacts
would not be expected to car occupants, to servicing personnel, or to
do-it-yourself (DIY) consumers.  This commenter noted differences
between the margin-of-exposure approach to assessing risk, as in EPA’s
risk assessment (EPA-HQ-OAR-2008-0664-0036), and the commenter’s
hazard index (HI) approach.  The commenter further stated that in all
cases, the predicted hazard index for HFO-1234yf was only one-half of
the values predicted for HFC-134a, and in some cases, only one-third of
the HFC-134a values, demonstrating from a health perspective that
HFO-1234yf is a viable alternative to HFC-134a.  

Response:  EPA agrees that adverse health impacts would not be expected
to car occupants or to servicing personnel, so long as the use
conditions of this rule are observed.  However, EPA has issued a
Significant New Use Rule under TSCA (October 27, 2010; 75 FR 65987) that
would require submission of additional information to EPA prior to the
manufacture, import or processing of HFO-1234yf for certain uses,
including distribution in commerce of products intended for use by a
consumer for the purposes of servicing, maintenance and disposal
involving HFO-1234yf (e.g., “do-it-yourself” servicing of MVAC
systems).  

Where available, it is EPA policy to use a NOAEL
(No-Observed-Adverse-Effect Level) for the point of departure (POD) for
risk assessment.  This is the highest exposure level that did not cause
an adverse health effect in a study.  In this case, EPA selected the POD
from an animal (rat 2-week inhalation) study.  Because animals may
respond to different exposure levels than humans, there is some
uncertainty when extrapolating from animals to humans.  For this reason,
an Uncertainty Factor (UF) is applied when extrapolating from animals to
humans – typically a factor of 10 is used but, in this case, since
there was a reasonable estimate of the pharmacokinetic component of the
uncertainty, this UF was reduced to 3.  An additional UF is applied to
account for variation in the human population response to a chemical
exposure – in this case, a UF of 10 was used.  The two UFs give a
resultant UF of 30 to yield an acceptable level of health risk.  As
stated in the final SNUR, EPA’s policy for review of new chemicals
under TSCA is to divide the POD by the exposure level to obtain the MOE.
 For HFO-1234yf, the “acceptable level of health risk” would be an
MOE of 30 or greater

The commenter proposed dividing the estimated exposure to HFO-1234yf by
the POD levels to obtain a HI.  As a result, if the exposure is less
than the POD, the HI is <1 and the commenter considered this an
“acceptable level of health risk.”  The commenter’s approach to
the hazard index does not factor in uncertainties about extrapolating
from animal to human responses, nor does it address variability within
the human population with regard to thresholds of response to chemical
exposures.  EPA has consistently applied the margin of exposure (MOE)
approach to evaluations of pre-manufacture notices (and for certain
other risk assessments) in order to account for the uncertainties
discussed above.  The SNAP program considered work performed during
evaluation of the pre-manufacture notice (EPA-HQ-OAR-2008-0664-0036), as
well as a separate SNAP program risk screen (EPA-HQ-OAR-2008-0664-0038).
 SNAP program risk screens compare expected exposures to exposure limits
that incorporate uncertainty factors based on EPA guidance, rather than
calculating either a hazard index or a margin of exposure.  Any of these
approaches to risk assessment will come to a similar conclusion about
whether there is a potential health concern when using the same point of
departure, uncertainty factors, and exposure estimates.  

The Agency and the commenter disagree on all three of these inputs to
the risk assessment and hence have reached different conclusions. 
Despite these differences, the assessments relied on by both the
commenter and EPA show that there is low risk both to car occupants and
to service technicians.  EPA’s risk assessment indicates a potential
risk to DIYers (EPA-HQ-OAR-2008-0664-0036).  As stated previously in
this action, this issue is further addressed through the Agency’s
authority under TSCA. 

Comment:  In response to EPA’s risk assessment
(EPA-HQ-OAR-2008-0664-0036), two commenters disagreed with the use of a
2-week study for evaluating 30 minute exposures and stated that acute
toxicity (4-hour test) or cardiac sensitization test results would be
more appropriate for acute exposure evaluations. 

Response:  Commenters have suggested that EPA use data from the 4-hour
acute toxicity study or from the cardiac sensitization study as a
starting point (“point of departure”) for assessing risks of
short-term (acute) exposure.  However, cardiac sensitization studies are
for very short durations – on the order of 10 minutes – and they
only address cardiac sensitization.  HFO-1234yf does not induce cardiac
sensitization.  EPA selected the point of departure for acute effects
from a multiple-exposure 2-week (subacute) rat inhalation study on
HFO-1234yf, reasoning that if no effects were seen in the duration of
the study (6 hours per day, 5 days per week for 2 weeks), that no
effects would be seen from a single exposure at a similar exposure
level, either.  Further, the subacute exposure rat study included more
thorough pathology examinations than those included in a cardiac
sensitization study.

	The acute 4-hour exposure study in rats showed some lung effects at
approximately 200,000 ppm, the lowest exposure level in the study.  Thus
EPA considers 200,000 ppm to be a LOAEL (Low-Observed-Adverse-Effect
Level).  If a LOAEL were used in the risk assessment instead of a NOAEL,
EPA would use an uncertainty factor to estimate a NOAEL, which would
result in a lower POD than what was used.  For example, if EPA had
started with the LOAEL of 200,000 ppm, it would have required an
additional MOE of 10 to estimate a NOAEL from a LOAEL, for a total MOE
of 300 instead of 30.  This would have resulted in a more conservative
risk assessment than using the NOAEL from the 14-day subacute study.  In
the 4-hour acute toxicity study, some of the animals had grey,
discolored lungs at all exposure levels in the study, and we considered
this an adverse effect.  Thus, EPA could only determine a lowest
observed adverse effect level (LOAEL) from the 4-hour acute study and
could not determine a no observed adverse effect level (NOAEL).  It is
longstanding Agency policy to use the NOAEL where available instead of a
LOAEL, because of greater assurance of a safe exposure level.  EPA
instead used the NOAEL for the next shortest study, the subacute 14-day
study, as the endpoint of concern for short term exposure because the
LOAEL from the acute 4-hour study is an endpoint showing effects that
may not result in safe exposure levels for humans.  If we had used the
value from the 4-hour acute toxicity study, we would have had to
consider additional uncertainty that would have resulted in a more
conservative, more restrictive risk assessment than using the NOAEL from
the 14-day subacute study.

	Further, EPA has uncertainties about using the available single
exposure studies on HFO-1234yf to determine the MOEs for different
exposure scenarios.  As a result of concerns with these studies, EPA
calculated single exposure MOEs from the NOAEL in the 2-week inhalation
toxicity study of HFO-1234yf in rats.  There are some uncertainties in
the single exposure (acute) assessments because of the observation of
lethality in rabbit dams after multiple exposures to HFO-1234yf in a
developmental study.  For these reasons, EPA recommended an acute
inhalation toxicity study on rabbits in the proposed SNUR to address the
question of whether pregnant rabbits would die from a single exposure
(April 2, 2010; 75 FR 16706).  

Comment:  A commenter asserted that EPA’s methodology to estimate the
exposure levels associated with the DIY use, using the SAE CRP (2008)
Phase II Report, greatly exaggerates the exposure that could be
experienced in actual use conditions.  Another commenter calculated
exposure to a DIYer assuming that the refrigerant fills a garage and
concluded that exposure would be less than the manufacturer’s
recommended exposure limit of 1000 ppm.  The first commenter stated that
the 30 minute time-weighted average (TWA) value used by the EPA is
unrealistic as are the exposure estimates presented in Scenarios 1 and 2
of the supporting document EPA-HQ-OAR-2008-0664-0036.  The specific
exposure parameters that the commenters questioned were assumptions
regarding:

	• garage volume;

	• time the user spent under the hood during recharging operations;

	• the size of the space where any leaking gas would disperse;

	• the air exchange rate in a service area that should be
well-ventilated when the engine is running;

	• use of the refrigerant in a closed garage with no ventilation; and,

	• the amount of refrigerant used during recharge operations.

During the comment period for the proposed SNUR, the PMN and SNAP
submitter conducted a simulated vehicle service leak testing, using
HFC-134a as a surrogate, indicating that exposures from use of a 12-oz
can during consumer DIY use are below the Agency’s level of concern
for HFO-1234yf (Honeywell, 2010a).

Response:  Concerning exposure estimates for DIYers, the exposure values
in the EPA risk assessment (EPA-HQ-OAR-2008-0664-0036) are bounding
estimates of the maximum possible theoretical concentrations.  The EPA
assessment used the industry-modeled DIY scenarios and assumptions in a
2008 report by Gradient Corporation for the SAE CRP (CRP, 2008) as a
starting point for creating the bounding estimates.  To do so, EPA
assumed that the entire leakage mass of each industry-modeled scenario
was released to its corresponding volume with no air exchange.  These
assumptions are conservative and protective, as intended.  

We considered the calculations provided by one commenter that assumed
that the refrigerant fills a garage.  However, this analysis assumes a
longer-term, steady-state concentration after the refrigerant has
diffused throughout the garage and uses a long-term, 8-hour
time-weighted average exposure recommendation for comparison.  EPA’s
concerns about DIY consumer exposure focuses on short-term acute
exposures, including peak exposures over a few minutes near the
consumer’s mouth and nose because typically a DIY consumer will only
need a short period of time to recharge a single MVAC system (Clodic,
2008).  Thus, the commenter’s calculations do not address EPA’s
concerns.

After reviewing the consumer DIY use exposure study from the SNAP/PMN
submitter, EPA responded with a list of clarifying questions (US EPA,
2010c), to which the submitter subsequently responded (Honeywell,
2010b).  Although the submitter’s responses were helpful, EPA still
has concerns about potential exposures to consumers during DIY use and
the inherent toxicity of HFO-1234yf.  However, since this acceptability
determination is limited to use with fittings for large containers,
which DIYers would not purchase, our concerns about potential health
risk to DIY users need not be addressed in this action.  We would plan
to evaluate this issue further before taking a final action on a SNAP
submission for unique fittings for small containers.  We further note
that the Agency would analyze this issue in the context of any SNUN
filed pursuant to the recently issued SNUR (75 FR 65987).  Although we
do not reach any conclusion in this final rule regarding safe use by
DIYers, we make the following observations about the submitted study. 
With regards to exposure, the peak concentration values from the
submitted study are as high as 3% by volume, equivalent to 30,000 ppm. 
These peaks appeared to occur in the first one or two minutes of each
emission.  Accordingly, EPA would need exposure data presented and
averaged out over shorter Time Weighted Averages (TWAs) than the 30
minutes currently in the study, because it would appear that a number of
these early exposure peaks could result in TWA values that would result
in MOEs less than the acceptable Agency level of 30 described above in
this section.  This is important because the data on HFO-1234yf are
insufficient to differentiate whether the toxicity is due to blood level
alone from an acute exposure, is due to accumulated exposure over time
(“area under the curve”), or is due to some combination of both. 
Since blood equilibrium levels are reached within minutes, a high level
of exposure in a short duration could result in blood levels exceeding a
threshold if the mode of action of the toxicity of HFO-1234yf is due to
blood levels of the chemical.  EPA expects that exposure data with
additional TWAs of 3, 5, and 10 minutes would help to resolve these
issues of consumer exposure. 

Comment:  One commenter stated that HFOs could harm the human nervous
system.  The commenter cited a diagram of breakdown products in a slide
presentation given by the Montreal Protocol Scientific Assessment Panel
in July 2009 and suggested that the toxic impact of aldehydes formed as
breakdown products would be higher than that of carbonic acids.  

Response:  EPA agrees that the breakdown products from the decomposition
of HFO-1234yf will include aldehydes, but we disagree that this is a
cause for concern.  The aldehydes that would be produced as atmospheric
breakdown products of HFO-1234yf are formaldehyde and acetaldehyde (ICF,
2010d).  Their health effects include respiratory effects; irritation of
the eyes, nose, and throat; and corrosion of the gastrointestinal tract.
 EPA also considers formaldehyde and acetaldehyde to be probable human
carcinogens  (US EPA, 2000; ICF, 2010d).  The decomposition products of
HFO-1234yf are not noted for causing neurotoxic effects, and toxicity
tests for HFO-1234yf did not identify this as an effect.  

As part of analysis of the atmospheric breakdown products of HFO-1234yf,
we found that worst-case concentrations of formaldehyde would reach 6 to
8 parts per trillion (ppt) on a monthly basis or an average of 3 ppt on
an annual average basis, compared to a health-based limit of 8000
ppt—i.e., a level that is roughly 1000 to 2600 times lower than the
health-based limit (ICF, 2010d).  Acetaldehyde levels would be even
lower, with worst-case concentrations of 1.2 ppt and annual average
concentrations of 0.23 ppt, compared to a health-based limit of 5000 ppt
(ICF, 2010d).  Thus, aldehydes that would be decomposition products of
HFO-1234yf in the atmosphere would not contribute significantly to
adverse human health effects (ICF, 2010d).  

Aldehydes, including formaldehyde and acetaldehyde, are already present
in the atmosphere in significant amounts from natural sources such as
plants, from direct emissions, from combustion products, or from
breakdown of other compounds such as hydrocarbons (NRC, 1981; Rhasa and
Zellner, 1987).  The current background level of formaldehyde in the
atmosphere ranges from 80 ppt in pristine areas to approximately 3300
ppt in New York, NY—one to three orders of magnitude more than the
worst-case generation of formaldehyde from HFO-1234yf (ICF, 2010d).  The
maximum incremental acetaldehyde concentration calculated due to use of
HFO-1234yf was approximately three orders of magnitude less than the
average concentration of acetaldehyde in areas with pristine air quality
(ICF, 2010d).  Thus, the additional aldehydes created during
decomposition of HFO-1234yf in the atmosphere are not likely to have a
significant impact on human health.

Comment:  Some commenters stated that additional research and review of
the available information regarding toxicity of HFO-1234yf needs to be
conducted.

Response:  EPA has an obligation to act on submissions in a timely
manner under the Act (§612(d)).  Our risk assessments to date have
found no significant risk for car passengers or drivers, professional
servicing personnel, or workers disposing of or recycling vehicles
containing HFO-1234yf.  We believe these assessments are sufficient to
support this action.  We note that these assessments rely on somewhat
conservative assumptions. 

We note that we expect there will be no toxicity risks to DIYers because
EPA must receive and take regulatory action to allow unique fittings for
use with small cans of refrigerant before DIYers could be exposed, as
per appendix D to subpart G of 40 CFR part 82.  Further, because
HFO-1234yf is not expected to be introduced into any new cars  until
late 2011 or later, we expect to have further information and to take
further action before DIYer could be exposed.  In addition, the final
SNUR would not allow distribution in commerce of products intended for
use by a consumer for the purposes of servicing, maintenance and
disposal involving HFO-1234yf until at least 90 days after submission of
a SNUN.

We recognize that more studies will be performed on HFO-1234yf, further
addressing risk.  EPA’s New Chemicals Program has recommended
additional testing of acute exposure in rabbits, including pregnant
rabbits (April 2, 2010; 75 FR 16706).  In addition, the manufacturer is
voluntarily conducting a multi-generation reproductive study.  If these
or other future studies call into question the basis for our decision
today, section 612 allows citizens to petition EPA to change or modify a
listing decision or EPA could determine on its own to reassess this
decision. 

Comment:  In late comments, a commenter stated that EPA appears to be
relying on a SNUR to reduce risks to human health from exposure to
HFO-1234yf.  This commenter stated that EPA must re-open the comment
period on the proposed SNAP rule so that commenters may reassess the
extent to which the final restrictions of the SNUR will be effective at
limiting adverse human health effects.  The same commenter noted that
information on new price levels and availability is needed to assess the
effectiveness of the SNUR. 

Response:  EPA’s final SNUR addresses potential risks to human health
from exposure to HFO-1234yf.  However, as discussed above in section V
of the preamble, “Why is EPA listing HFO-1234yf as acceptable subject
to use conditions?”, this final SNAP rule does not allow for the use
of HFO-1234yf with small cans or containers (i.e., container sizes that
would be purchased by DIY users, such as small cans and containers less
than 5 lbs) because it does not contain specifications for unique
fittings for can taps and for these smaller containers.  Existing SNAP
program regulations in appendix D to subpart G of 40 CFR part 82 require
the use of unique fittings for specific purposes (e.g., high
pressure-side service port, small can taps) for each MVAC refrigerant,
as submitted by the refrigerant manufacturer.  Before HFO-1234yf can be
introduced in small containers typically used by DIYers, the
manufacturer must submit unique fittings to EPA, we must conclude that
they are unique, and we must issue new proposed and final rules
specifying those fittings.  In addition, the final SNUR would not allow
distribution in commerce of products intended for use by a consumer for
the purposes of servicing, maintenance and disposal involving HFO-1234yf
until at least 90 days after submission of a SNUN.  These and other
requirements ensure – to the extent possible, with the information
currently available to EPA – that HFO-1234yf has no greater risk
overall for human health and the environment than other available
refrigerants for MVAC.

Under the final SNUR, it is necessary for EPA to receive and complete
its review of a significant new use notice (SNUN) with additional
information on consumer exposure risks before – if the Agency so
decides –  HFO-1234yf may be manufactured, imported or processed for
the purpose of use in DIY servicing, with or without other restrictions.
 We would also consider information in the SNUN before issuing a final
rule specifying unique fittings for use with small containers of
refrigerant.

In comments EPA received on the proposed SNAP rule, the initial direct
final SNUR that was withdrawn and the proposed SNUR, no commenters
suggested making the provisions of the SNUR stricter or suggested adding
use conditions under the SNAP program for addressing risks to consumers
during DIY servicing.  A number of commenters stated that no
restrictions were needed to address risks to consumers during DIY
servicing, while other commenters stated more broadly that EPA should
find HFO-1234yf unacceptable because of its toxicity risks.  We provided
an additional opportunity for comment on the SNAP rule after the direct
final SNUR was issued (February 1, 2010; 75 FR 4083), in response to a
request to reopen the public comment period
(EPA-HQ-OAR-2008-0664-0077.1), in part to allow comment on the
relationship between these two rulemakings that both address HFO-1234yf.
 However, we do not believe that the conditions of the final SNUR are
necessary to the determination that we are making here.  As noted above,
this final rule does not allow for the servicing of HFO-1234yf from
container sizes that would be purchased by DIY users because of the lack
of an approved unique fitting for smaller containers.  Further
rulemaking under SNAP will occur prior to such use and any risks can be
addressed in that rulemaking package.  At that time, we will be able to
fully consider the impact of the final SNUR. 

2.	Flammability

Comment:  Five commenters stated that HFO-1234yf has a low likelihood of
ignition, especially under the conditions encountered in an automotive
application.  One commenter stated that the mere presence of high
refrigerant concentrations does not contribute to a hazardous condition
because an ignition source of sufficient energy must also be present. 
Another commenter disagreed with EPA’s view that a flammability risk
exists.  Other commenters stated that additional review of the available
information regarding flammability of HFO-1234yf needs to be conducted. 
Some commenters stated that EPA should consider restricting
concentrations of HFO-1234yf to much lower concentrations than to the
lower flammability limit (LFL) of 6.2%.

Response:  The available evidence indicates that HFO-1234yf will not
present a significant risk of flammability and that any risk it poses is
not greater than the risk presented by other available alternatives. 
For example, because of its higher LFL, its considerably higher minimum
ignition energy (5000 mJ to 10,000 mJ), and its slower flame speed (1.5
cm/s), HFO-1234yf is less flammable than HFC-152a, a substitute that EPA
has already found acceptable subject to use conditions.  

Further, an analysis conducted for SAE International’s Cooperative
Research Program by Gradient Corporation (CRP, 2009) found that there
was a very low flammability risk (on order of 10-14 occurrences per
operating hour or 1 occurrence in 100 years across the entire U.S. fleet
of passenger vehicles).  This was due to the low probability of
achieving a concentration of HFO-1234yf above the LFL at the same time
as having a sufficiently high energy source to cause the refrigerant to
ignite.  Further, even that low probability of ignition of HFO-1234yf
may be overstated, because it assumes that a vehicle collision severe
enough to crack open the evaporator (located under the windshield and
steering wheel) is not severe enough to crack the windshield or windows
that would hold refrigerant in the passenger compartment.  In a
sensitivity analysis, the SAE CRP considered how the flammability risk
would change if a refrigerant release into the passenger compartment
only occurs in a collision causing damage to more than the MVAC system. 
That analysis estimated that the risk of exposure to an open flame would
then be reduced by a factor of 23,000, to approximately 4 x 10-19
occurrences per vehicle operating hour (EPA-HQ-OAR-2008-0664-0056.2).

For the reasons provided above in sections IV and VII.B of the preamble,
“What are the final use conditions and why did EPA finalize these use
conditions?” and “Use conditions,” EPA does not believe it is
necessary to establish a use condition limiting refrigerant
concentrations, whether at 6.2% or some other, lower value.  We believe
the final use conditions sufficiently address flammability risks.

Comment:  Three commenters stated that HFO-1234yf is flammable and that
the proposed regulation does not offer any restrictions to protect those
persons handling HFO-1234yf, nor does it restrict its sale and use by
the general public.

Response:  The purpose of the use conditions is to ensure that
HFO-1234yf will not pose a greater risk to human health or the
environment than other available or potentially available substitutes. 
For all of the reasons provided in sections IV and V above, EPA has
determined that HFO-1234yf will not pose a greater risk than other
substitutes for MVAC.  As explained above, EPA proposed restricting
concentrations of the refrigerant below the LFL of 6.2% as a use
condition.  Based on comments and additional analysis, EPA has concluded
that it is not necessary to require use conditions limiting refrigerant
concentrations to below the LFL; rather, the use conditions now specify
design parameters for MVAC systems and require an FMEA.  This will
ensure that systems are designed to minimize risk not only from
flammability, but also from exposure to HF.  

We will address use by service personnel through a rulemaking under
section 609 of the CAA.  Although these rules will further address
issues of interest to service personnel and others that might handle
HFO-1234yf used in MVAC systems, we note that our risk assessments of
use of HFO-1234yf found that significant flammability risks do not exist
for personnel installing the refrigerant at equipment manufacture,
professional servicing personnel, and personnel working with automobiles
at equipment end-of-life (EPA-HQ-OAR-2008-0664-0036 and -0038). 
Moreover, we note that an industry-sponsored analysis of risks found the
risk of ignition of HFO-1234yf to a technician is extremely small, on
the order of 10-26 occurrences per working hour
(EPA-HQ-OAR-2008-0664-0056.2).

As we have explained above, this rule only addresses the use of large
containers for professional use (typically 20 lbs or larger) and thus
HFO-1234yf may not be used in small container sizes that would be the
type purchased by the general public.  We will address the issue of risk
to DIY users through a future rulemaking under SNAP if we receive a
request for unique fittings for smaller containers from the refrigerant
manufacturer.  We also are addressing risks to DIY users through the
Significant New Use Rule under the Toxic Substances Control Act (October
27, 2010; 75 FR 65987). 

Comment:  One commenter stated that compared with HFC-134a, the
explosion probability of HFO-1234yf is much higher based on testing done
at the Federal Institute for Materials Research and Testing
(Bundesanstalt fuer Materialforschung und –pruefung, BAM).  Other
commenters disagreed with those flammability conclusions, finding the
testing results to be expected but not representative of real-world use
in MVAC.  These commenters stated that the flammability risks of
HFO-1234yf were not significant and that the mixtures of HFO-1234yf and
ethane used in the testing would not be seen in MVAC in actual
operations.

Response:  As explained above in section VII.B, we do not believe that
these tests  are relevant for assessing the flammability risks of
HFO-1234yf as used in MVAC systems because they evaluated flammability
based on the presence of ethane, a substance that should not be present
in any situation that might cause flammability risks for MVAC systems.

3.	Toxicity of Hydrogen Fluoride (HF)

Comment:  Two commenters stated that there is low risk of exposure to
HF.  One of these commenters stated that (1) for vehicles that do not
discontinue the use of the blower after collision, the risk of exposure
to HF from use of HFO-1234yf is approximately twice the risk with the
current use of HFC-134a, and (2) for vehicles that discontinue the use
of the blower after collision, the risk of implementing HFO-1234yf due
to exposure to HF is approximately the same as that with the current use
of HFC-134a (on order of 10-12 occurrences per operating hour, or one in
one trillion).  The second commenter stated that there is no need for
concentration limits to protect against exposure to HF because the risks
from exposure to HF from HFO-1234yf are similar to what would be
experienced with HFC-134a.  One commenter also stated that
concentrations of HF as low as 0.3 ppm cause a sensation of irritation. 
The commenter stated that this characteristic would deter someone from
remaining exposed to excessive concentrations from an open hood.

Other commenters stated that that there is a high probability of HF
generation in cars from HFO-1234yf.  One commenter stated that the
flammability of HFO-1234yf makes the production of HF more likely and
increases the risk of HF exposure to vehicle passengers, to workers at
chemical facilities, automotive manufacturing facilities, vehicle
servicing facilities, and to the general public.  Two commenters stated
that various health and safety concerns related to HF generation and its
toxicity are well studied and documented, and three commenters stated
that use of HFO-1234yf is unacceptable as there is increased potential
for HF exposure and related casualties.

Response:  EPA has considered the potential for generation of HF from
HFO-1234yf, including the SAE CRP’s evaluation of scenarios that might
cause workplace and consumer exposure to HF
(EPA-HQ-OAR-2008-0664-0056.2).  SAE CRP members conducted tests to
measure HF concentrations and to identify factors that were most likely
to lead to HF formation.  One set of tests conducted in a car found that
HF measurements inside the passenger cabin were 35 ppm or less
(EPA-HQ-OAR-2008-0664-0056.2).  This highest value occurred during
release of the entire charge of refrigerant of 1000 g into the passenger
cabin with ignition started by a butane lighter augmented with an
additional spark—a highly conservative scenario.  (A more typical
charge would be 575 g, and it would be unlikely to have the amount of
ignition energy that occurred artificially in the experiment with use of
both a butane lighter and an additional spark source.)  A second set of
tests focusing on HF in the engine compartment tried to simulate a major
rupture in the AC system that would release 12 g/s of refrigerant across
5 cm onto an artificial hot surface at temperatures of 450 ºC (typical
of the exhaust manifold) and 700 ºC (most extreme case), with the car
hood in various positions.  This testing found HF concentrations as high
as 120 ppm at the hot surface in the engine compartment in the worst
case, with interior passenger cabin values of 40 to 80 ppm in the worst
case (EPA-HQ-OAR-2008-0664-0056.2).  This test was conservative for the
following reasons:  the temperature was high, representing extreme
conditions; the refrigerant was released extremely close to the hot
surface; the hood was closed; and the refrigerant ignited briefly.  The
other test trials under less extreme conditions resulted in HF
concentrations of a few ppm.  The test trials also found somewhat lower
concentrations of HF generated during testing of HFC-134a using the same
procedures and apparatus, with maximum concentration of 36 ppm in the
engine compartment and concentrations of less than 8 ppm in the
passenger compartment in the worst case.  The SAE CRP selected an Acute
Exposure Guideline Limit (AEGL)-2 of 95 ppm over 10 minutes as its
criterion for determining excessive risk.  This limit was developed to
protect against irreversible health effects when exposure remains below
the limit of 95 ppm over 10 minutes, but short-term discomfort or
irritation could still occur.  Thus, even assuming a passenger inside a
vehicle was exposed to HF at the highest level found in the test of 80
ppm, exposure at this level would at worst cause discomfort and
irritation, rather than permanent or disabling health effects.  

For both HFO-1234yf and for HFC-134a, HF concentrations in the passenger
compartment fell between the level that would protect against all
adverse health effects (AEGL-1 of 1.0 ppm for 10 minutes to 8 hours) and
the level that would protect against irreversible or disabling health
effects (AEGL-2 of 95 ppm over 10 minutes) (NRC, 2004).  The SAE CRP
concluded that the probability of such a worst case event is on the
order of 10-12 occurrences per operating hour
(EPA-HQ-OAR-2008-0664-0056.2).  Commenters provided information
indicating that this level of risk for HF generation is the same order
of magnitude for both HFC-134a and for HFO-1234yf.  EPA considers the
risk level presented by HFO-1234yf to be similar to that of the
refrigerant currently being used by automobile manufacturers, HFC-134a. 
Therefore, there is no reason to regulate HFO-1234yf more stringently to
protect against HF exposure than for HFC-134a.

Comment:  One commenter stated that testing with HFOs commissioned by
the environmental organization Greenpeace in 2001 hinted at a multitude
of decomposition products with high reactivity.  The commenter stated
that apparently even lubricants (polyalkylene glycol--PAG) break down to
HF when in contact with HFO-1234yf in a MVAC system.  The commenter
further expressed that BAM testing showed that burning HFO-1234yf
resulted in concentrations of HF greater than 90 ppm in the engine
compartment.  The commenter concluded that the tests prove that in a
standard system with standard charge (900 grams) and oil, the risk for
humans would be incalculable.

⁰C and HF concentrations of over 90 ppm were measured in the engine
compartment.  According to a risk assessment from an automobile
manufacturer, such a high temperature is unlikely and could only be
achieved on the exhaust manifold under heavy engine loads such as when a
vehicle is climbing a hill, and the temperature of the exhaust manifold
would drop in a minute or so during deceleration
(EPA-HQ-OAR-2008-0664-0081.1).  It is not clear what the conditions were
for the study mentioned by the commenter.  For example, it is not clear
if the refrigerant was mixed with compressor oil as it normally would be
in an MVAC; inclusion of oil with a relatively low flashpoint would be
expected to lead to ignition at lower temperatures
(EPA-HQ-OAR-2008-0664-0056.2, EPA-HQ-OAR-2008-0664-0118.1).  It also is
not clear if the compressor fan was operating during the test.  During
normal vehicle operation, the fan would cool down the compressor and the
engine compartment, avoiding the temperature of 600 °C on hot surfaces
in the engine.  

Other tests have found that HF concentrations in the engine compartment
were approximately 5 ppm or less and only in the worst case (hot surface
temperature of 700 ° C, closed hood on engine compartment) did HF
concentrations attain a value of approximately 120 ppm in the engine
compartment (OAR-2008-0664-0056.2).  This level is slightly higher than
the AEGL-2 of 95 ppm on a 10-minute average and is lower than the AEGL-3
for HF of 170 ppm on a 10-minute average, the value that would protect
against life-threatening exposure but would not necessarily prevent
long-term health effects.  However, we note that we do not anticipate
any circumstance where a person would be exposed to these levels in an
engine compartment because such conditions would not occur during
vehicle servicing, but rather during vehicle operation.  Further, in the
case of a collision resulting in a fire, we would expect that
professional first responders have training in chemical hazards and
possess appropriate gear which would prevent them from receiving HF
exposures above health-based limits (EPA-HQ-OAR-2008-0664-0056.2) and an
interested by-stander would quickly back away from a fire or from
irritating HF vapors, thus preventing excessive HF exposure.  The
concentration measured in the passenger compartment in the same
worst-case situation was in the range of 40 to 80 ppm, less than the
concentration in the engine compartment and less than the AEGL-2
intended to protect against long-term health effects.  Thus, we disagree
with the commenter’s assertion that HF exposures from thermal
decomposition or combustion of refrigerant would be likely to results in
fatalities.  We further note that the HF concentrations found in the
passenger compartment were lower than the health-based limit, the AEGL-2
of 95 ppm over 10 minutes.

We also note that the risks presented by HFO-1234yf are not
significantly different than the risk posed by HFC-134a, the refrigerant
currently in use in MVAC systems.  Mixtures of HFC-134a and compressor
oil also combust and generate HF.  Testing performed using HFC-134a
under worst-case conditions in the engine compartment (hot surface
temperature of 700 ºC, closed hood on engine compartment) found HF
concentrations as high as 36 ppm in the engine compartment and 2 to 8
ppm in the passenger compartment.  The amount of HF generated from a
typical charge of HFC-134a, if it all burned or decomposed, could be
even more than for the expected charge of HFO-1234yf because charge
sizes using HFO-1234yf are expected to be smaller
(EPA-HQ-OAR-2008-0664-0056.2).  The SAE CRP considered potential risks
of HF exposure from both HFO-1234yf and from HFC-134a.  Both presented
potential risks on the order of 10-12 occurrences per operating hour
(EPA-HQ-OAR-2008-0664-0056.2, -0096.1).  This corresponds to less than
one case per year across the entire fleet of motor vehicles in the U.S. 
Although there is no specific testing data on HF production from
HFC-152a, another acceptable refrigerant for MVAC, since this compound
contains fluorine, it presents risks of HF generation as well.  As
discussed above in Section IV of the preamble, we are not requiring
specific use conditions that regulate production of HF, either directly
or indirectly, because of the low level of risk.  However, the final use
conditions in this rule address the risks of HF production, as well as
risks of flammability, by requiring certain design safety features of
MVAC systems using HFO-1234yf and by requiring risk analysis for each
car model through FMEAs.

Comment:  A commenter provided results from a test by IBExU on the
decomposition of HFO-1234yf under heat (EPA-HQ-OAR-2008-0664-0053.3). 
This commenter strongly warned against a decision in favor of HFO-1234yf
because it would form highly toxic HF when burning.  Three commenters
disagreed that the results of the IBExU testing were relevant because
test conditions did not represent realistic conditions.  One commenter
said that the SAE risk assessment, which used actual vehicle test data
for HF formation, found that actual HF formation rates are far below the
levels [from the IBExU test results] cited by the first commenter, the
Federal Environmental Agency (Umweltbundesamt—UBA).

Response:  The IBExU testing of HF generation from HFO-1234yf is not
relevant to assessing the risks of HFO-1234yf as a refrigerant in MVAC. 
Laboratory tests concerning the nature of HF generation on hot surfaces
found that this depends on the contact time of reactants on the hot
surface, the temperature of the hot surface and the movement of
refrigerant in diluted concentrations due to airflow
(EPA-HQ-OAR-2008-0664-0056.2; EPA-HQ-OAR-2008-0664-0116.2).  The IBExU
testing involved heating the refrigerant steadily in a sealed flask. 
Thus, the contact time in that test was far greater than would occur in
an engine compartment and the movement of refrigerant in that test was
essentially zero, unlike in an engine compartment where there would be
constant air movement.  

Comment:  Another test from BAM reported by UBA examined HF formation
from HFO-1234yf and from HFC-134a (EPA-HQ-OAR-2008-0664-0080.1).  Fifty
grams of refrigerant was streamed through a hole of 2 mm diameter onto a
hot metal surface.  The study found that pure HFO-1234yf exploded on the
hot surface whereas pure HFC-134a did not.  The study also found that
when HFO-1234yf was mixed with 3% oil, it exploded at 600 °C.  The
commenter stated that handling of HFO-1234yf in the presence of hot
metal surfaces results in HF formation in concentrations far above
allowed workplace concentrations.

Response:  These results are not consistent with results from hot-plate
tests conducted by an automobile manufacturer and by a chemical
manufacturer for the SAE CRP (EPA-HQ-OAR-2008-0664-0056.2;
EPA-HQ-OAR-2008-0664-0115.1).  Those manufacturers found that neither
HFO-1234yf nor HFC-134a alone ignited at 900 °C.  One of these tests
found that HFO-1234yf mixed with PAG oil combusted starting at 730 °C,
while HFC-134a mixed with PAG oil ignited at 800°C and above; the other
test observed no ignition of a blend of each refrigerant with PAG oil at
800 °C, but both blends ignited at 900 °C.  Based on the lack of
reproducibility of the specific ignition temperature, it appears that
the specific ignition temperature may depend on variables in the testing
(e.g., flash point of the oil used, amount of mixture used, angle of
application, and air flow available).  This information also shows that
mixtures of refrigerant with compressor oil can combust at lower
temperatures than pure refrigerant and that mixtures of HFO-1234yf and
oil and mixtures of HFC-134a and oil present similar risks of ignition
and HF generation.  Thus, we concluded that the risks of toxicity from
HF exposure due to combustion or decomposition of HFO-1234yf are
comparable to those from HFC-134a.  

Further, the risks from toxicity of HF posed by both refrigerants are
small.  The SAE CRP estimates this risk on the order of 10-12 cases per
operating hour (EPA-HQ-OAR-2008-0664-0086.1).  This is equivalent to
less than one event per year across the entire fleet of motor vehicles
in the U.S.  For comparison, this is less than one ten-thousandth the
risk of a highway vehicle fire and one fortieth or less of the risk of a
fatality from deployment of an airbag during a vehicle collision
(EPA-HQ-OAR-2008-0664-0056.2).  

Retrofit usage

Comment:  Several commenters stated that HFO-1234yf should be used
initially in new vehicles but should not be used to retrofit vehicles
using HFC-134a, or at least not unless there are industry standards to
guide such a process.  Other commenters stated that it is critical to
allow a natural phase-out of the fleet of cars using HFC-134a as the
refrigerant, rather than requiring retrofitting existing cars with
HFO-1234yf.  A commenter expressed concern that retrofitting of HFC-134a
MVAC systems with HFO-1234yf would result in cases of
cross-contamination of refrigerant, while another commenter contested
this statement and found it unsupported.  Other commenters opposed
obstacles that would prevent older MVACs from being retrofitted to the
new refrigerant.  These commenters mentioned the potential for
greenhouse gas benefits when retrofitting systems currently using
HFC-134a with HFO-1234yf. 

Response:  The submitter did not request review of HFO-1234yf for
retrofitting vehicles and thus EPA did not review HFO-1234yf as
acceptable (or acceptable subject to use conditions) for retrofitting in
MVAC in this rulemaking.  Consistent with the request submitted to the
Agency, we proposed to find HFO-1234yf acceptable for use subject to use
conditions in new MVAC systems and evaluated its risks only for use in
new systems.  We will consider the retrofit use of HFO-1234yf in MVAC
systems if we receive a submission that specifically addresses
retrofitting and the risks that are unique to retrofitting.  In response
to the commenter who raised a concern about a “phase-out” of
HFC-134a and the potential that we would “require” use of
HFO-1234yf, we note that our rulemakings under SNAP do not require use
of any specific substitute.  Rather, under SNAP, we have established
lists of substitutes that are acceptable for use in various end-uses
(such as for MVACs) and end-users are free to choose which substitute to
use, but must do so consistent with any use conditions that apply.  As
stated in the rule establishing the SNAP program, “The Agency…does
not want to intercede in the market’s choice of available substitutes,
unless a substitute has been proposed or is being used that is clearly
more harmful to human health and the environment than other
alternatives.”  59 FR 13046, March 18, 1994.  We further note that
this rulemaking does not change the status of HFC-134a, which remains an
acceptable substitute for use in MVACs, subject to use conditions.

Use by “do-it-yourselfers”

Comment:  Some commenters raised concerns about EPA’s statements in
the proposed rule about potential health effects that might occur
without professional training and the use of CAA Section 609 certified
equipment.  These commenters stated that the studies and testing in the
docket support a finding that use of HFO-1234yf by non-professionals is
safe and do not offer valid technical support for EPA’s concerns.  

Response:  EPA’s risk assessment and risk screen both indicated that
worst-case exposure levels expected during servicing by
do-it-yourselfers are of potential concern (EPA-HQ-OAR-2008-0664-0036
and EPA-HQ-OAR-2008-0664-0038).  In both documents, this was based upon
estimated exposure levels from a 2008 risk assessment by Gradient
Corporation for the SAE CRP (EPA-HQ-OAR-2008-0664-0008).  In EPA’s
risk assessment (EPA-HQ-OAR-2008-0664-0036), we found that the level
that EPA determined did not cause health effects in laboratory animals
might be only 2 to 3 times higher than the exposure predicted for that
use (the “margin of exposure”).  Our risk assessment indicated a
higher, more protective margin of exposure of at least 30 was needed to
account for uncertainty in the extrapolation from animals to humans and
for variability in the human population.  In other words, we found that
based on worst-case assumptions, a do-it-yourselfer’s exposure could
be 10 or more times the level that EPA considered safe.  The margin of
exposure was calculated using a conservative estimated exposure level of
45,000 ppm over 30 minutes and a human equivalent concentration of
98,211 ppm from a no-observed adverse effect level that we selected as
the point of departure for risk assessment (EPA-HQ-OAR-2008-0664-0036). 


However, under this final rule, unique fittings have only been submitted
for servicing fittings for the high-side and low-side ports and for
large containers of HFO-1234yf and thus the acceptability listing is
limited to use of HFO-1234yf with the unique fittings specified (e.g.,
for large containers of 20 pounds or more).  We expect these containers
would not be purchased by DIYers because of their expense ($800 or more
per container) and because they would contain enough refrigerant for 10
charges or more.  We will continue to review the issue of safe use for
DIYers if and when we are requested to review unique fittings for a
smaller container size.  In addition,  EPA is further addressing the
issue of risks to DIYers in the Significant New Use Rule for
1-propene-2,3,3,3-tetrafluoro- (75 FR 65987, October 27, 2010).  This
SNUR requires submission of a SNUN at least 90 days before sale or
distribution of products intended for use by a consumer for the purpose
of servicing, maintenance and disposal involving HFO-1234yf.  

EPA’s proposed rule on the use of HFO-1234yf as a substitute for
CFC-12 in new MVAC systems did not propose to establish use conditions
for servicing vehicles by certified professionals, but our analyses
indicate that there is not significant risk to certified professionals,
because HFC-134a, which is currently used in most MVAC systems, presents
similar risks and professionals have the knowledge and equipment to
mitigate any risks.  We plan to further address servicing by
professionals when we develop a new rule under section 609 of the Clean
Air Act for servicing and maintenance of MVAC systems.  

Comment:  Some commenters supported prohibiting sale of HFO-1234yf in
small containers.  Other commenters stated that only certified
technicians should be allowed to purchase and use refrigerants,
including HFC-134a and HFO-1234yf.  Other commenters found no data to
support restrictions on the sale of HFO-1234yf to non-professionals.

Response:  As noted previously, the submission only addressed unique
fittings for large containers (e.g., 20 lbs or larger) of HFO-1234yf. 
If anyone is interested in using HFO-1234yf in small cans or other small
containers, they would need to contact the refrigerant manufacturer to
submit unique fittings for approval under the SNAP program.  Thus, under
this final rule, we believe that only certified technicians will
purchase HFO-1234yf because the larger containers are likely to be
prohibitively expensive for individuals performing DIY servicing ($800
or more for a 20 lb cylinder) and are likely to be too large for most
individuals to use, containing enough refrigerant for 10 or more
charges.

We also note that in a separate final rule under the authority of TSCA
(October 27, 2010; 75 FR 65987), EPA requires among other things, that
notice must be given to EPA 90 days before (1) HFO-1234yf is used
commercially other than in new passenger cars and vehicles in which the
charging of motor vehicle air conditioning systems with HFO-1234yf was
done by the motor vehicle OEM or (2) sale or distribution of products
intended for use by a consumer for the purpose of servicing, maintenance
and disposal involving HFO-1234yf.

Comment:  A commenter stated that banning DIY use of HFO-1234yf will
mean that car owners will be forced to have professionals perform
service work on their AC systems at a significantly higher cost.  This
commenter stated that millions of lower-income motorists may be forced
to go without air conditioning each year or may seek out lower-cost
alternatives such as propane or HFC-152a.

Response:  While this final rule effectively prohibits DIY use because
the final use conditions do not include unique fittings allowing for use
with small refrigerant containers, we are not making any final
determination about whether HFO-1234yf may be safely used by DIYers.  As
we noted above, we have not yet received a submission for DIY use or
received unique fittings for small containers from the manufacturer, but
would evaluate such submissions when we receive one.  We note that
because it is unlikely that any cars will have MVAC systems with
HFO-1234yf before the 2013 model year, we believe the availability of
small containers for DIY use will not be of concern until such cars are
sold and there is a need to recharge a new MVAC system on a model year
2013 vehicle.  The separate final Significant New Use Rule that the
Agency has issued under TSCA (75 FR 65987; October 27, 2010) requires
submission of a Significant New Use Notice at least 90 days before sale
or distribution of products intended for DIY use.  

With respect to the commenter who suggests that some people may seek
lower cost alternatives, presumably to repair an existing MVAC, we note
that under current EPA regulations in appendix D to subpart G of 40 CFR
part 82, it is not legal to top-off the refrigerant in an MVAC system
with a different substitute refrigerant.  

G.	Servicing issues

Comment:  Several commenters stated that appropriate training and
certification should be required to purchase HFO-1234yf for use in
MVACs.  Four commenters also stated that the final regulation should
include a provision requiring proof of certification in order to
purchase HFO-1234yf, and recommended that current AC systems tests
(i.e., for CAA section 609 certification) be updated.

Some commenters disagreed with EPA’s statement that HFO-1234yf may
cause serious health effects when used in servicing and maintaining
MVACs without professional training.  Another commenter stated that EPA
is limiting productivity by only allowing dealerships to perform
refrigerant maintenance, and that independent MVAC serviced shops should
be allowed to be certified.  The commenter also questioned who will
monitor “certified” technicians employed by dealerships that may do
work on the side.  A commenter representing automobile dealerships
specifically opposed mandatory requirements for certification of
technicians because of potential costs and burden on small businesses. 

Response:  As background for the public comments, we note that under
EPA’s regulations implementing section 609, one must be a section 609
certified technician in order to purchase CFC-12 or other ODS for use in
MVAC (40 CFR 82.34(b)).  Section 609(e) of the CAA itself specifically
prohibits sale of small containers less than 20 pounds with Class I or
Class II substances suitable for use as a refrigerant in MVAC, except
for individuals performing service for consideration in compliance with
section 609.  However, there is no comparable restriction on the sale of
HFC-134a or on other substitutes for MVAC that do not contain Class I or
Class II ODS, such as HFO-1234yf.

In the NPRM (74 FR 53449), EPA stated that any specific training and
certification requirements would be adopted through a rulemaking under
the authority of CAA section 609 and would be codified in 40 CFR part 82
subpart B, which contains the regulations implementing section 609.  We
will address concerns regarding certification and training requirements
during that separate rulemaking process.  We note, however, that the CAA
itself mandates that persons performing service for consideration that
involve the refrigerant must be properly trained and certified. 
Furthermore, as noted previously, we believe that there is not a
significant health risk to professionals from HFO-1234yf because they
will have the knowledge and equipment to mitigate any risks.  Also,
because HFC-134a presents similar risks to HFO-1234yf, and the
flammability risks of HFO-1234yf are less than those for HFC-152a, the
health risks of HFO-1234yf are not significantly greater than those of
other available substitutes.  

With regard to whether independent service shops could service MVACs
with HFO-1234yf or whether service would be limited to
“dealerships,” we note that neither this rule nor any other CAA
regulation would limit servicing to dealerships.  The comment may
concern the withdrawn SNUR, 75 FR 4983 (February 1, 2010), which
referred to the “original equipment manufacturer”; the commenter may
have interpreted this term to mean an automobile dealership.  The final
SNUR (October 27, 2010; 75 FR 65987) requires a significant new use
notice to EPA at least 90 days before “commercial use other than in
new passenger cars and vehicles in which the charging of motor vehicle
air conditioning systems with the PMN substance [HFO-1234yf] was done by
the motor vehicle original equipment manufacturer.”  This requirement
restricts commercial use of HFO-1234yf to use for vehicles that were
initially charged with HFO-1234yf by the automobile’s manufacturer, as
opposed to allowing commercial use of HFO-1234yf for vehicles initially
charged with a different refrigerant.  The term “original equipment
manufacturer” refers to the automobile manufacturer, not to
dealerships.    

Comment:  Commenters indicated that SAE International is developing
standards for safety and servicing of alternative refrigerant HFO-1234yf
MVAC systems.  Another commenter stated that there are appropriate
mechanisms within the industry for training.  One commenter representing
automobile dealerships objected to mandatory Section 609 technician
certification and training for use of HFO-1234yf, stating that because
dealerships already train technicians on flammable substances in
accordance with hazard communication standards of the Occupational
Safety and Health Administration (OSHA), and since the risks associated
with HFO-1234yf are similar to those that already exist in MVAC service
facilities, mandatory training and proof of training is not necessary. 
To enable training pursuant to the OSHA hazard communication standard,
the commenter stated that MVAC system and refrigerant suppliers should
provide dealerships with sufficient information on the hazards posed by
HFO-1234yf. 

Response:  EPA is issuing use conditions in this final rule that
reference relevant SAE technical standards on safety.  This rule does
not, however, include a use condition  requiring technician training and
does not refer to specific training standards.  We agree with the
commenter that current technician training generally should be
sufficient to ensure that professional technicians will use HFO-1234yf
safely.  Although this SNAP determination does not contain a use
condition regarding technician training, as noted above, section 609 of
the CAA requires technician training for persons servicing for
consideration.  EPA will consider in a separate rulemaking under section
609, whether it is necessary to modify our existing regulations under
section 609 to include additional specifications for HFO-1234yf.  

Comment:  A commenter representing automobile dealerships opposed
mandatory requirements for recycling and containment of the refrigerant
because of potential costs and minimal environmental benefits. 

Response:  This rulemaking does not impose requirements for recycling or
containment of the refrigerant.  A separate rulemaking under CAA section
609 will address practices required in the servicing of MVAC systems
using HFO-1234yf, including recycling and recovery.  Further, EPA notes
that Section 608 of the CAA prohibits the intentional release of any
refrigerant during the maintenance, repair, service, or disposal of
refrigeration and air conditioning equipment, unless the Administrator
determines through rulemaking that such release does not pose a threat
to the environment.  We have not made such a determination for
HFO-1234yf.

H.	Cost, availability, and small business impacts

Comment:  One late commenter stated that there was insufficient
information in the record on the cost, terms of availability and
anticipated market share of HFO-1234yf for EPA to make the required
statutory findings that HFO-1234yf “reduces the overall risk to human
health and the environment” by comparison to other alternatives that
are already available.  The commenter stated that this information is
necessary in order for EPA to assess anticipated environmental effects
adequately.  The same commenter stated that EPA’s environmental
analysis is based on price assumptions that were not disclosed and are
no longer valid, and thus, EPA should subpoena the information from the
manufacturer and reopen the public comment period.

Response:  EPA believes that there was sufficient information in the
record at the time of proposal for us to complete a meaningful
environmental analysis, even in the absence of definitive cost
information.  At the time of proposal, we had available both estimates
from a trade magazine provided by the manufacturer (Weissler, 2008), as
well as estimates of price provided in the initial submission from the
manufacturer (EPA-HQ-OAR-2008-0664-0013).  The estimates of price
provided by the manufacturer were claimed as confidential business
information and thus were not available in the record to the public.  

We typically use this type of information for purposes of determining
market penetration for a particular substance, so that we can evaluate
how much of the substitute will likely be used and thus the
environmental risks it might pose.  In this case, however, because the
automobile industry tends to prefer use of a single substitute,
information on the cost of the substitute was not critical to our
analysis.  Thus, in conducting our environmental analysis, we took a
conservative approach, assuming that all new MVAC systems began using
HFO-1234yf by 2020 (i.e., full market penetration).  We also considered
an even more conservative scenario, in which HFO-1234yf would be the
only refrigerant used for stationary air conditioning and for
refrigeration as of 2020, as well as for MVAC.  Even with these highly
conservative assumptions, we found that there would not be sufficient
negative environmental impacts due to emissions of HFO-1234yf to warrant
finding it unacceptable.

In the proposal, we mentioned a cost estimate for HFO-1234yf of
$40-$60/lb (Weissler, 2008).  More recently, the first automobile
manufacturer announcing its intension to use HFO-1234yf confirmed that
this range does not underestimate prices of HFO-1234yf and is consistent
with the manufacturer’s long-term purchase contracts (Sciance, 2010). 
Thus, the most recent information shows costs to be similar to those we
considered at the time of proposal.  This data contradicts the late
commenter’s assertion that the manufacturer’s effective monopoly
would result in significantly different, higher costs that would
invalidate EPA’s earlier analysis.  In any event, assuming that costs
were higher as suggested by the commenter, then we expect that use of
HFO-1234yf would be less than assumed for our health and environmental
risk analysis.  As mentioned in the proposal, emissions, and thus the
resulting environmental effects such as impacts on local air quality or
on production of TFA, would be expected to be less under a scenario with
higher prices and less use of HFO-1234yf.  Our analysis assumes
widespread use and thus its results would be protective.

We note that where a new chemical is introduced, there is some
uncertainty in the price.  At best, the manufacturer can provide rough
estimates of price and of market share before the chemical is produced
in commercial quantities and becomes subject to supply and demand
pressures.  EPA’s requirement for information on cost, anticipated
availability in the market, and anticipated market share (40 CFR
82.178(a)(14) through (16)) should not be construed as requiring
precise, detailed cost estimates based upon a well-defined methodology. 
As noted above, we use these numbers for the purposes of predicting
market penetration and thus how much of a particular substitute may be
used and thus pose an environmental risk.  As we did for HFO-1234yf, we
typically take a environmentally-protective approach to our evaluation,
assuming use at least as high as that the cost and availability
information may indicate.

Comment:  A late commenter stated that the information in the record is
insufficient for EPA to make a statutory finding that HFO-1234yf is
“currently or potentially available.”  The commenter stated that a
previous decision by the United States Court of Appeals for the District
of Columbia Circuit (Honeywell International, Inc. V. EPA, 374 F.3d 1363
(D.C. Cir. 2004)) implied that an interpretation of the term
“available” in CAA section 612(c)(2) could potentially consider
economic factors if EPA adopted such an approach as a reasonable
interpretation of the statutory language.  The commenter states that EPA
should obtain information as to the anticipated cost of HFO-1234yf if
the manufacturer does not grant licenses to produce.

Response:  The CAA does not require that EPA find a substitute to be
available or potentially available when finding it acceptable.  Section
612(c) states:

…It shall be unlawful to replace any class I or class II substance
with any substitute substance which the Administrator determines may
present adverse effects to human health or the environment, where the
Administrator has identified an alternative to such replacement that—

 reduces the overall risk to human health and the environment; and

 is currently or potentially available….

(emphasis added.)

This section makes clear that it is not the substitute under review that
must be available or potentially available, but rather alternative
replacements for ODS that EPA determines pose less overall risk to human
health and the environment than the substitute being reviewed.  Thus, if
there are alternatives to the substance under review that are currently
or potentially available and that pose less risk, EPA cannot find the
substitute under review acceptable.  Section 612(c) establishes no
requirement that EPA must determine that the substitute under review is
“available.”  See also 40 CFR 82.180(b)(describing types of listing
decisions EPA can make in reviewing substitutes).

We note that even if EPA was required to determine that the substitute
under review is available or potentially available before it could make
an acceptability determination, we believe that the available
information supports that HFO-1234yf is potentially available.  EPA’s
definition of “potentially available” at 40 CFR 82.172 provides:

  SEQ CHAPTER \h \r 1 Potentially available is defined as any
alternative for which adequate health, safety, and environmental data,
as required for the SNAP notification process, exist to make a
determination of acceptability, and which the Agency reasonably believes
to be technically feasible, even if not all testing has yet been
completed and the alternative is not yet produced or sold.

This definition makes explicit that it is not necessary to have perfect
information on a substitute nor is it necessary for the substitute to be
produced or sold in order for EPA to consider it “potentially
available.”  Instead, it is necessary for EPA to find the health,
safety and environmental data adequate to make a determination of
acceptability, and for the Agency to reasonably believe that the
alternative is “technically feasible,” in order for the alternative
to be potentially available.  We believe the record contains adequate
information showing that HFO-1234yf is potentially available.  The
manufacturer has submitted the information required under 40 CFR 82.178
(e.g., pre-manufacture notice form and TSCA/SNAP addendum form
containing:  name and description of the substitute, physical and
chemical information, information on ODP and global warming impacts,
toxicity data, data on environmental fate and transport, flammability,
exposure, cost and estimated production).  The submitter has also
provided unique fittings as required under appendix D to subpart G of 40
CFR part 82.  Thus, we believe that there is “adequate health, safety,
and environmental data.”  Even if the commenter were correct about
claims that higher costs would result if the manufacturer does not grant
licenses for production, as discussed above, this does not affect the
adequacy of the health, safety, and environmental data for HFO-1234yf,
because we have protectively assumed widespread use that would result in
more emissions and greater environmental impacts.  In addition, based on
the experimental work conducted by the automobile industry, we
reasonably believe that HFO-1234yf is technically feasible as a
refrigerant.  Thus, HFO-1234yf would still be “potentially
available” under the SNAP program’s definition.

One commenter points to Honeywell International, Inc. v. EPA, 374 F.3d
1363 in urging EPA to explicitly include cost as a consideration in
determining whether a substitute is “potentially available.”  In
that case, the court vacated and remanded a SNAP decision in which EPA
listed a foam blowing substitute as acceptable subject to “narrowed
use limits” on the basis that for some niche foam blowing uses, the
substitutes that were already listed as acceptable might not be
available.  Under the narrowed use limits, the end-user would need to
demonstrate and document that other substitutes were not technically
feasible for a particular use.  The court vacated and remanded EPA’s
rule on the basis that EPA had considered cost in concluding that
already listed substitutes might not be available based on
“technical” feasibility, and that EPA had not attempted to justify
the rule on the ground that the statute allows it to consider economic
factors in making its SNAP determinations.  The court left open the
question of whether EPA could attempt to interpret the term
“available” in section 612(c) as allowing for consideration of
costs. 

Again, we note that “available or potentially available” applies
only to the substitutes against which the substitute at issue is being
compared.  The Agency has not decided whether consideration of the cost
of other substitutes should be a factor to consider in determining
whether they are available or potentially available and thus should (or
should not) be used for comparison to a substitute under review. 
However, we note that for purposes of the substitute under review, the
Agency firmly believes that cost should not be the primary or sole basis
for finding a substitute unacceptable.  EPA’s role is to determine the
health and environmental risk associated with the use of substitutes and
the market should serve to address the issue of costs.  Costs will
necessarily be a factor considered by the automobile manufacturers in
deciding which substitute to use. 

Comment:  Two commenters stated that EPA needed to perform further
analysis on the potential small business impacts and costs of EPA’s
regulations and the introduction of HFO-1234yf.  A commenter
representing recyclers of automobiles and scrap metal expressed concern
about the regulatory burden and costs that automotive recyclers are
likely to incur if they must manage flammable refrigerants that are
regulated as hazardous waste under EPA’s regulations implementing the
Resource Conservation and Recovery Act (RCRA).  The same commenter also
suggests that the RCRA subtitle C regulations would need to be changed
to alleviate the hazardous-waste management requirements for handling
HFO-1234yf.  The other commenter mentioned the costs to service and
repair shops, end-of-life vehicle recyclers, and automobile dealerships,
and stated that EPA needed to analyze costs to these small businesses
under the Regulatory Flexibility Act.  This latter commenter stated that
EPA should determine if a significant change in price and supply
expectations would affect the way that these businesses handle and deal
with automobile repairs and recycling.

Response:  The RFA applies only when there are small entities subject to
the requirements of the proposed or final rule.  5 U.S.C. § 604(a)(3). 
We believe the potential burden of complying with RCRA regulations
placed on those recycling or recovering a substitute is generally not
pertinent to a decision of whether HFO-1234yf should be found acceptable
under SNAP.  To the extent the commenters are suggesting that we must
evaluate such costs for purposes of the Regulatory Flexibility Act, we
note that under the RFA we evaluate costs imposed by the enforceable
regulations being promulgated.  To the extent the costs referred to by
the commenter are already imposed under RCRA, they would not be new
costs, but costs associated with the relevant RCRA regulations. 
Moreover, under this SNAP final rule, EPA is not requiring the use of
HFO-1234yf, and thus the costs associated with its use are not due to
enforceable regulatory requirements under SNAP.  To the extent there are
enforceable requirements for those persons who choose to use this new
substitute, those requirements (the “use conditions”) apply
primarily to manufacturers of automobiles and MVAC systems, because they
concern design of MVAC systems.  The one use condition of the rule that
applies to servicing of MVAC systems, and thus, could apply to small
businesses, is the requirement for specific unique service fittings. 
However, EPA’s existing SNAP regulations at appendix D to subpart G of
40 CFR part 82 already require unique service fittings as specified by
the refrigerant manufacturer.  Thus, the costs of purchasing new unique
fittings for this refrigerant are imposed by the pre-existing
regulation.  This rule specifies the requirements for the type of unique
fitting, in accordance with the fittings provided to EPA by the
manufacturer.  These fittings are proposed for adoption as part of the
draft SAE J639 standard.  It is not clear that there would be any cost
differential between these specific unique fittings and others that the
automotive industry could adopt instead.  For these reasons, EPA is able
to certify that this regulation will not create a significant impact on
a significant number of small entities.

EPA notes that there may be costs of servicing or of disposal
(end-of-life) to small businesses under future regulations under section
609 or 608 of the CAA.  We will conduct an analysis of such costs, as
necessary, as part of those future rulemakings.

Comment:  A commenter stated that to comply with requirements of the
Unfunded Mandates Reform Act (UMRA), EPA needed to perform further
analysis on the potential costs of EPA’s SNAP regulations for
HFO-1234yf to determine if the rule would result in the expenditure of
$100 million or more per year by the private sector.  In particular, the
commenter stated that EPA must obtain more information on pricing and
the effect of the manufacturer’s patent to analyze this.

Response:  UMRA applies only to “enforceable duties” imposed on
State, local, and tribal governments or on the private sector.  The SNAP
rule does not impose duties on governments.  As we have noted
previously, the SNAP program does not mandate the use of any specific
substitute for ozone depleting substances.  Rather, through this action,
we are expanding the choices of MVAC refrigerants available to the
private sector.  The issue raised by the commenter concerning the cost
of the refrigerant and the effect of the manufacturer’s patent on
pricing is not related to any requirement of the rule, and thus, EPA is
not required to consider that cost under UMRA.  

VIII.	How does the SNAP program work?

	A. 	What are the statutory requirements and authority for the SNAP
program?

Section 612 of the Clean Air Act (CAA) requires EPA to develop a program
for evaluating alternatives to ozone-depleting substances (ODS).  EPA
refers to this program as the Significant New Alternatives Policy (SNAP)
program.  The major provisions of section 612 are: 

Rulemaking

Section 612(c) requires EPA to promulgate rules making it unlawful to
replace any class I (i.e., chlorofluorocarbon, halon, carbon
tetrachloride, methyl chloroform, methyl bromide, and
hydrobromofluorocarbon) or class II (i.e., hydrochlorofluorocarbon)
substance with any substitute that the Administrator determines may
present adverse effects to human health or the environment where the
Administrator has identified an alternative that (1) reduces the overall
risk to human health and the environment, and (2) is currently or
potentially available.

Listing of Unacceptable/Acceptable Substitutes

Section 612(c) requires EPA to publish a list of the substitutes
unacceptable for specific uses and to publish a corresponding list of
acceptable alternatives for specific uses.  The list of acceptable
substitutes is found at http://www.epa.gov/ozone/snap/lists/index.html
and the lists of “unacceptable”, “acceptable subject to use
conditions”, and “acceptable subject to narrowed use limits”
substitutes are found at 40 CFR part 82 subpart G. 

Petition Process

Section 612(d) grants the right to any person to petition EPA to add a
substance to, or delete a substance from, the lists published in
accordance with section 612(c).  The Agency has 90 days to grant or deny
a petition.  Where the Agency grants the petition, EPA must publish the
revised lists within an additional six months.

90-day Notification

Section 612(e) directs EPA to require any person who produces a chemical
substitute for a class I substance to notify the Agency not less than 90
days before new or existing chemicals are introduced into interstate
commerce for significant new uses as substitutes for a class I
substance.  The producer must also provide the Agency with the
producer's unpublished health and safety studies on such substitutes. 

Outreach

Section 612(b)(1) states that the Administrator shall seek to maximize
the use of federal research facilities and resources to assist users of
class I and II substances in identifying and developing alternatives to
the use of such substances in key commercial applications.

Clearinghouse

Section 612(b)(4) requires the Agency to set up a public clearinghouse
of alternative chemicals, product substitutes, and alternative
manufacturing processes that are available for products and
manufacturing processes which use class I and II substances.

B. 	What are EPA’s regulations implementing section 612?

On March 18, 1994, EPA published the original rulemaking (59 FR 13044)
which established the process for administering the SNAP program and
issued EPA's first lists identifying acceptable and unacceptable
substitutes in the major industrial use sectors (40 CFR part 82, subpart
G).  These sectors include:  refrigeration and air conditioning; foam
blowing; cleaning solvents; fire suppression and explosion protection;
sterilants; aerosols; adhesives, coatings and inks; and tobacco
expansion.  These sectors compose the principal industrial sectors that
historically consumed the largest volumes of ODS.

	Section 612 of the CAA requires EPA to list as acceptable only those
substitutes that do not present a significantly greater risk to human
health and the environment as compared with other substitutes that are
currently or potentially available.  

C.  	How do the regulations for the SNAP program work?

Under the SNAP regulations, anyone who plans to market or produce a
substitute to replace a class I or II ODS in one of the eight major
industrial use sectors must provide notice to the Agency, including
health and safety information on the substitute at least 90 days before
introducing it into interstate commerce for significant new use as an
alternative.  This requirement applies to the person planning to
introduce the substitute into interstate commerce, typically chemical
manufacturers, but may also include importers, formulators, equipment
manufacturers, or end-users when they are responsible for introducing a
substitute into commerce.

	The Agency has identified four possible decision categories for
substitutes: acceptable; acceptable subject to use conditions;
acceptable subject to narrowed use limits; and unacceptable.  Use
conditions and narrowed use limits are both considered “use
restrictions” and are explained below.  Substitutes that are deemed
acceptable with no use restrictions (no use conditions or narrowed use
limits) can be used for all applications within the relevant end-uses
within the sector.  Substitutes that are acceptable subject to use
restrictions may be used only in accordance with those restrictions.  It
is illegal to replace an ODS with a substitute listed as unacceptable,
unless certain exceptions (e.g., test marketing, research and
development) provided by the regulation are met.

	After reviewing a substitute, the Agency may determine that a
substitute is acceptable only if certain conditions in the way that the
substitute is used are met to minimize risks to human health and the
environment.  EPA describes such substitutes as "acceptable subject to
use conditions."  Entities that use these substitutes without meeting
the associated use conditions are in violation of section 612 of the
Clean Air Act and EPA’s SNAP regulations.

	For some substitutes, the Agency may permit a narrowed range of use
within an end-use or sector.  For example, the Agency may limit the use
of a substitute to certain end-uses or specific applications within an
industry sector.  The Agency requires a user of a narrowed use
substitute to demonstrate that no other acceptable substitutes are
available for their specific application by conducting comprehensive
studies.  EPA describes these substitutes as “acceptable subject to
narrowed use limits.”  A person using a substitute that is acceptable
subject to narrowed use limits in applications and end-uses that are not
consistent with the narrowed use limit, are using these substitutes in
an unacceptable manner and are in violation of section 612 of the CAA
and EPA’s SNAP regulations.

	The Agency publishes its SNAP program decisions in the Federal Register
(FR).  EPA publishes decisions concerning substitutes that are deemed
acceptable subject to use restrictions (use conditions and/or narrowed
use limits), or for substitutes deemed unacceptable, as proposed
rulemakings to allow the public opportunity to comment, before
publishing final decisions. 

	In contrast, EPA publishes substitutes that are deemed acceptable with
no restrictions in “notices of acceptability,” rather than as
proposed and final rules.  As described in the rule initially
implementing the SNAP program (59 FR 13044), EPA does not believe that
rulemaking procedures are necessary to list alternatives that are
acceptable without restrictions because such listings neither impose any
sanction nor prevent anyone from using a substitute.

	Many SNAP listings include “comments” or “further information”
to provide additional information on substitutes.  Since this additional
information is not part of the regulatory decision, these statements are
not binding for use of the substitute under the SNAP program.  However,
regulatory requirements so listed are binding under other regulatory
programs.  The “further information” classification does not
necessarily include all other legal obligations pertaining to the use of
the substitute.  While the items listed are not legally binding under
the SNAP program, EPA encourages users of substitutes to apply all
statements in the “further information” column in their use of these
substitutes.  In many instances, the information simply refers to sound
operating practices that have already been identified in existing
industry and/or building-codes or standards.  Thus, many of the
statements, if adopted, would not require the affected user to make
significant changes in existing operating practices.	

D.  	Where can I get additional information about the SNAP program?

For copies of the comprehensive SNAP lists of substitutes or additional
information on SNAP, refer to EPA’s Ozone Depletion web site at
www.epa.gov/ozone/snap/index.html.  For more information on the Agency's
process for administering the SNAP program or criteria for evaluation of
substitutes, refer to the SNAP final rulemaking published March 18, 1994
(59 FR 13044), codified at 40 CFR part 82, subpart G.  A complete
chronology of SNAP decisions and the appropriate citations are found at 
 HYPERLINK "http://www.epa.gov/ozone/snap/chron.html" 
http://www.epa.gov/ozone/snap/chron.html .

IX.  Statutory and Executive Order Reviews

A.	Executive Order 12866: Regulatory Planning and Review

Under Executive Order (EO) 12866   SEQ CHAPTER \h \r 1 (58 FR 51735,
October 4, 1993), this action is a "significant regulatory action.”  
SEQ CHAPTER \h \r 1  It raises novel legal or policy issues arising out
of legal mandates, the President's priorities, or the principles set
forth in the Executive Order. 

Accordingly, EPA submitted this action to the Office of Management and
Budget (OMB) for review under EO 12866 and any changes made in response
to OMB recommendations have been documented in the docket for this
action.

B.	  SEQ CHAPTER \h \r 1   SEQ CHAPTER \h \r 1 Paperwork Reduction Act

This action does not impose any new information collection burden. 
Today's action is an Agency determination.  It contains no new
requirements for reporting.  The only new recordkeeping requirement
involves customary business practice.  Today's rule requires minimal
record-keeping of studies done to ensure that MVAC systems using
HFO-1234yf meet the requirements set forth in this rule.  Because it is
customary business practice that OEMs conduct and keep on file Failure
Mode and Effect Analysis (FMEA) on any potentially hazardous part or
system from the beginning of production of a car model until three or
more years after production of the model ends, we believe this
requirement will not impose an additional paperwork burden.  However,
the Office of Management and Budget (OMB) has previously approved the
information collection requirements contained in the existing
regulations in subpart G of 40 CFR part 82 under the provisions of the
Paperwork Reduction Act, 44 U.S.C. 3501 et seq. and has assigned OMB
control numbers 2060-0226. The OMB control numbers for EPA's regulations
are listed in 40 CFR Part 9.

	C.	Regulatory Flexibility Act  

The Regulatory Flexibility Act (RFA) generally requires an agency to
prepare a regulatory flexibility analysis of any rule subject to notice
and comment rulemaking requirements under the Administrative Procedure
Act or any other statute unless the agency certifies that the rule will
not have a significant economic impact on a substantial number of small
entities.  Small entities include small businesses, small organizations,
and small governmental jurisdictions.

For purposes of assessing the impacts of today's rule on small entities,
small entity is defined as: (1) A small business as defined by the Small
Business Administration's (SBA) regulations at 13 CFR 121.201; for NAICS
code 336111 (Automobile manufacturing), a small business has <1000
employees; for NAICS code 336391 (Motor Vehicle Air-Conditioning
Manufacturing), a small business has <750 employees; (2) a small
governmental jurisdiction that is a government of a city, county, town,
school district or special district with a population of less than
50,000; and (3) a small organization that is any not-for-profit
enterprise which is independently owned and operated and is not dominant
in its field.

	After considering the economic impacts of today's final rule on small
entities, I certify that this action will not have a significant adverse
economic impact on a substantial number of small entities.  The only new
requirement on small entities in this final rule is a requirement
specifying the type of unique service fittings required when servicing
MVAC systems using the refrigerant HFO-1234yf.  Existing regulations at
appendix D to subpart G of 40 CFR part 82 already require that there be
unique service fittings for each refrigerant used in MVAC systems. 
Thus, the costs of purchasing new unique fittings for this refrigerant
have already been imposed by the pre-existing regulation.  This rule
specifies the requirements for which type of unique fitting, in
accordance with the fittings provided to EPA by the manufacturer.  These
fittings are proposed for adoption as part of the draft SAE J639
standard.  It is not clear that there would be any cost differential
between these specific unique fittings and others that the automotive
industry could adopt instead.  Thus, cost impacts of this final rule on
small entities are expected to be small.  This final rule is expected to
relieve burden for some small entities, such as car repair shops, by
allowing them the flexibility to use a new refrigerant that otherwise
would have been prohibited under previous requirements at appendix B to
subpart G, 40 CFR part 82 and by allowing them to use the easy-to-use
“quick-connect” fittings for this refrigerant.  Other final rule
requirements apply to original equipment manufacturers, which are not
small entities.  These final rule requirements are the least burdensome
option for regulation.

Original equipment manufacturers are not mandated to move to MVAC
systems using HFO-1234yf.  EPA is simply listing HFO-1234yf as an
acceptable alternative with use conditions in new MVAC systems.  This
rule allows the use of this alternative to ozone-depleting substances in
the MVAC sector and outlines the conditions necessary for safe use.  By
approving this refrigerant under SNAP, EPA provides additional choice to
the automotive industry which, if adopted, would reduce the impact of
MVACs on the global environment.  This rulemaking does not mandate the
use of HFO-1234yf as a refrigerant in new MVACs.

	D.	Unfunded Mandates Reform Act

	Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Public Law
104-4, establishes requirements for Federal agencies to assess the
effects of their regulatory actions on State, local, and tribal
governments and the private sector. Under section 202 of the UMRA, EPA
generally must prepare a written statement, including a cost-benefit
analysis, for proposed and final rules with ``Federal mandates'' that
may result in expenditures to State, local, and tribal governments, in
the aggregate, or to the private sector, of $100 million or more in any
one year.  Before promulgating an EPA rule for which a written statement
is needed, section 205 of the UMRA generally requires EPA to identify
and consider a reasonable number of regulatory alternatives and adopt
the least costly, most cost-effective or least burdensome alternative
that achieves the objectives of the rule.  The provisions of section 205
do not apply when they are inconsistent with applicable law.  Moreover,
section 205 allows EPA to adopt an alternative other than the least
costly, most cost-effective or least burdensome alternative if the
Administrator publishes with the final rule an explanation why that
alternative was not adopted.  Before EPA establishes any regulatory
requirements that may significantly or uniquely affect small
governments, including tribal governments, it must have developed under
section 203 of the UMRA a small government agency plan.  The plan must
provide for notifying potentially affected small governments, enabling
officials of affected small governments to have meaningful and timely
input in the development of EPA regulatory proposals with significant
Federal intergovernmental mandates, and informing, educating, and
advising small governments on compliance with the regulatory
requirements.

EPA has determined that this rule does not contain a Federal mandate
that may result in expenditures of $100 million or more for State,
local, and tribal governments, in the aggregate, or the private sector
in any one year.  Today's rule does not affect State, local, or tribal
governments.  The enforceable requirements of today's rule related to
system design and documentation of the safety of alternative MVAC
systems affect only a small number of original equipment manufacturers. 
Further, those requirements are consistent with requirements that the
automotive industry is proposing to adopt through consensus standards of
SAE International.  We expect that most manufacturers of automobiles and
MVAC systems would attempt to meet those requirements or something very
similar, even in the absence of EPA’s regulations.  The only
requirement that is applied more widely than for original equipment
manufacturers is a requirement specifying the type of unique service
fittings required when servicing MVAC systems using the refrigerant
HFO-1234yf.  Existing regulations at appendix D to subpart G of 40 CFR
part 82 already require that there be unique service fittings for each
refrigerant used in MVAC systems.  The fittings required in this final
rule are proposed for adoption as part of the draft SAE J639 standard. 
Thus, the costs of this rule are consistent with standard industry
practice and are expected to be much less than $100 million per year.

This action provides additional options allowing greater flexibility for
industry in designing consumer products.  The impact of this rule on the
private sector will be less than $100 million per year.  Thus, today's
rule is not subject to the requirements of sections 202 and 205 of the
UMRA.  EPA has determined that this rule contains no regulatory
requirements that might significantly or uniquely affect small
governments. This regulation applies directly to facilities that use
these substances and not to governmental entities.  This rule does not
mandate a switch to HFO-1234yf and the limited direct economic impact on
entities from this rulemaking is less than $100 million annually.

	E.	Executive Order 13132: Federalism

Executive Order 13132, entitled ``Federalism'' (64 FR 43255, August 10,
1999), requires EPA to develop an accountable process to ensure
``meaningful and timely input by State and local officials in the
development of regulatory policies that have federalism implications.''
``Policies that have federalism implications'' is defined in the
Executive Order to include regulations that have ``substantial direct
effects on the States, on the relationship between the national
government and the States, or on the distribution of power and
responsibilities among the various levels of government.''

This action does not have federalism implications.  It will not have
substantial direct effects on the States, on the relationship between
the national government and the States, or on the distribution of power
and responsibilities among the various levels of government, as
specified in Executive Order 13132.  This regulation applies directly to
facilities that use these substances and not to governmental entities. 
Thus, Executive Order 13132 does not apply to this rule.

	F.	Executive Order 13175:  Consultation and Coordination with Indian
Tribal Governments

Executive Order 13175, entitled ``Consultation and Coordination with
Indian Tribal Governments'' (59 FR 22951, November 6, 2000), requires
EPA to develop an accountable process to ensure ``meaningful and timely
input by tribal officials in the development of regulatory policies that
have tribal implications.''  This final rule does not have tribal
implications, as specified in Executive Order 13175.  It does not
significantly or uniquely affect the communities of Indian tribal
governments, because this regulation applies directly to facilities that
use these substances and not to governmental entities. Thus, Executive
Order 13175 does not apply to this rule.

G.	Executive Order 13045: Protection of Children from Environmental
Health Risks and Safety Risks 

	This action is not subject to EO 13045 (62 FR 19885, April 23, 1997)
because it is not economically significant as defined in EO 12866, and
because the Agency does not believe the environmental health or safety
risks addressed by this action present a disproportionate risk to
children.  This action’s health and risk assessments are discussed in
sections V and VII.D of the preamble and in documents
EPA-HQ-OAR-2008-0664-0036 and HQ-OAR-2008-0664-0038 in the docket for
this rulemaking.  

H.	Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use

	This action is not a “significant energy action” as defined in
Executive Order 13211 (66 FR 28355 (May 22, 2001)), because it is not
likely to have a significant adverse effect on the supply, distribution,
or use of energy.  This action could impact manufacturing and repair of
MVAC systems using an alternative refrigerant. This rule does not
mandate a switch to HFO-1234yf.  Preliminary information indicates that
these new systems are more energy efficient than currently available
systems in some climates.  Therefore, we conclude that this rule is not
likely to have a significant adverse effect on energy supply,
distribution or use.

	I.	National Technology Transfer and Advancement Act  SEQ CHAPTER \h \r
1  

	Section 12(d) of the National Technology Transfer and Advancement Act
of 1995 (“NTTAA”), Public Law No. 104-113, 12(d) (15 U.S.C. 272
note) directs EPA to use voluntary consensus standards in its regulatory
activities unless to do so would be inconsistent with applicable law or
otherwise impractical.  Voluntary consensus standards are technical
standards (e.g., materials specifications, test methods, sampling
procedures, and business practices) that are developed or adopted by
voluntary consensus standards bodies.  NTTAA directs EPA to provide
Congress, through OMB, explanations when the Agency decides not to use
available and applicable voluntary consensus standards. 

This rulemaking involves technical standards.  EPA has decided to use
SAE International’s most recent version of the SAE J1739 standard. 
This standard can be obtained from
http://www.sae.org/technical/standards/.  This standard addresses safety
and reliability issues in motor vehicle design, including MVAC systems
using alternative refrigerants.

J.	Executive Order 12898:  Federal Actions to Address Environmental
Justice in Minority Populations and Low-Income Populations

Executive Order (EO) 12898 (59 FR 7629 (Feb. 16, 1994)) establishes
federal executive policy on environmental justice.  Its main provision
directs federal agencies, to the greatest extent practicable and
permitted by law, to make environmental justice part of their mission by
identifying and addressing, as appropriate, disproportionately high and
adverse human health or environmental effects of their programs,
policies, and activities on minority populations and low-income
populations in the United States.  

EPA has determined that this final rule will not have disproportionately
high and adverse human health or environmental effects on minority or
low-income populations because it increases the level of environmental
protection for all affected populations without having any
disproportionately high and adverse human health or environmental
effects on any population, including any minority or low-income
population. HFO-1234yf is a non ozone-depleting substance with a low
GWP.  Based on the toxicological and atmospheric work described earlier,
HFO-1234yf will not have any disproportionately high and adverse human
health or environmental effects on any population, including any
minority or low-income population.  This final rule requires specific
use conditions for MVAC systems, if car manufacturers chose to make MVAC
systems using this low GWP refrigerant alternative.

K.	Congressional Review Act

The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the
Small Business Regulatory Enforcement Fairness Act of 1996, generally
provides that before a rule may take effect, the agency promulgating the
rule must submit a rule report, which includes a copy of the rule, to
each House of the Congress and to the Comptroller General of the United
States.  EPA will submit a report containing this rule and other
required information to the U.S. Senate, the U.S. House of
Representatives, and the Comptroller General of the United States prior
to publication of the rule in the Federal Register.  A Major rule cannot
take effect until 60 days after it is published in the Federal Register.
 This action is not a “major rule” as defined by 5 U.S.C. 804(2). 
This rule will be effective [insert date 60 days after publication].

XI. References

The documents below are referenced in the preamble.  All documents are
located in the Air Docket at the address listed in section titled
``ADDRESSES'' at the beginning of this document.  Unless specified
otherwise, all documents are available in Docket ID No.
EPA-HQ-OAR-2008-0664 at   HYPERLINK
"http://frwebgate.access.gpo.gov/cgi-bin/leaving.cgi?from=leavingFR.html
&log=linklog&to=http://www.regulations.gov"  http://www.regulations.gov
.

Benesch et al., 2002.  Investigation of Effects of Trifluoroacetate on
Vernal Pool Ecosystems.  Environ. Tox and Chem. Vol. 21, No. 3 pp.
640-647.  2002.  Available online at
http://www3.interscience.wiley.com/journal/122678081/abstract?CRETRY=1&S
RETRY=0

Benouali et al., 2008.  “A/C System Control Strategies for Major
Refrigerant Options” June 11, 2008, Alternative Refrigerant Systems
Symposium Phoenix, AZ.  Available online at   HYPERLINK
"http://www2.dupont.com/Refrigerants/en_US/assets/downloads/SmartAutoAC/
2008_SAE_ARSS_Valeo_Eval.pdf" 
http://www2.dupont.com/Refrigerants/en_US/assets/downloads/SmartAutoAC/2
008_SAE_ARSS_Valeo_Eval.pdf 

Besnard, S., 1996.  Full Flammability Test of Gases and Gas Mixtures in
Air.  CERN.  European Organization for Nuclear Research.  1996. 
Available online at
http://cdsweb.cern.ch/record/1217583/files/CM-P00055900.pdf

Boutonnet et al., 1999.  Boutonnet, J.C., et al. "Environmental Risk
Assessment of Trifluoroacetic Acid," Human and Ecological Risk
Assessment, Feb. 1999.  Available online at   HYPERLINK
"http://www.informaworld.com/smpp/content~db=all~content=a922749285~frm=
abslink" 
http://www.informaworld.com/smpp/content~db=all~content=a922749285~frm=a
bslink . 

CARB, 2008.  Technical Support Document “Staff Analysis on Emissions
and Economic Impact of Proposed Regulation for Small Containers of
Automotive Refrigerant.” Appendix G to Certification Procedures for
Small Containers of Automotive Refrigerant. California Air Resources
Board, effective March 10, 2010. Document incorporated by reference in
California Code of Regulations (CCR), title 17, sections 95360 through
95370. Available online at  HYPERLINK
"http://www.arb.ca.gov/regact/2009/hfc09/hfc09.htm"
http://www.arb.ca.gov/regact/2009/hfc09/hfc09.htm .

Carter, 2009.  Investigation of Atmospheric Ozone Impacts of
2,3,3,3-Tetrafluoropropene.  Final report to Honeywell Internationl
Contract UCR-09010016.  William Carter, University of California,
Riverside CA.  June 2, 2009.  Available online at   HYPERLINK
"http://www.cert.ucr.edu/%7Ecarter/pubs/YFrept.pdf" 
http://www.cert.ucr.edu/%7Ecarter/pubs/YFrept.pdf .

Ceviz and Yuksel, 2005.  “Cyclic variations on LPG and
gasoline-fuelled lean burn SI engine.”  Renewable Energy.  In press. 
Available online at   HYPERLINK
"http://www.pm-kbase.com/articles/LPGsdarticle(8).pdf" 
http://www.pm-kbase.com/articles/LPGsdarticle(8).pdf .

Clodic et al., 2008.  Evaluation of the Potential Impact of Emissions of
HFC-134a From Non Professional Servicing of Motor Vehicle Air
Conditioning Systems.  D. Clodic, A. Tremoulet, Y, Riachi, D. Sousa, L.
Palandre, A. Garnier,  S.Clodic and M. Lansard.  Prepared under CARB
Agreement No. 06-341. December, 2008.  Available online at
http://www.arb.ca.gov/research/apr/past/06-341.pdf.

CRP, 2008.  Risk Assessment for Alternative Refrigerants HFO-1234yf 
Phase II. Prepared for SAE International Cooperative Research Program
1234 by Gradient Corporation.  February 26, 2008.  Docket number
EPA-HQ-OAR-2008-0664-0008

CRP, 2009.  Risk Assessment for Alternative Refrigerants HFO-1234yf and
R-744 (CO2)  Phase III. Prepared for SAE International Cooperative
Research Program 1234 by T. Lewandowski, Gradient Corporation.  December
17, 2009.  Docket number EPA-HQ-OAR-2008-0664-0056.2

DuPont, 2008.  DuPont internal testing.  Cited in docket number
EPA-HQ-OAR-2008-0664-0052.1.

Hamner Institutes, 2007.  Toxicogenomic assessment of the carcinogenic
potential of 2,3,3,3-tetrafluoropropene.  The Hamner Institutes for
Health Sciences.  January 5, 2007.  Docket numbers   HYPERLINK
"https://fdms.erulemaking.net/fdms-web-agency/custom/jsp/agency/dockettr
ee/PhaseSequenceDocument.jsp" \l "#"  EPA-HQ-OAR-2008-0664-0030  through
-0030.6.

Honeywell, 2010a.  Comment on EPA Proposed Rule (simulated vehicle
service leak testing and exposure study).  Docket ID:
EPA-HQ-OPPT-2008-0918-0088.

Honeywell, 2010b.  Response to EPA questions.  Docket ID:
EPA-HQ-OPPT-2008-0918-0096.

ICF, 2008.  ICF International.  2008.  Air Conditioning Refrigerant
Charge Size to Passenger Compartment Volume Ratio Analysis.  Docket
number EPA-HQ-OAR-2008-0664-0003

ICF, 2009.  ICF International.  2009.  Revised Final Draft Assessment of
the Potential Impacts of HFO-1234yf and the Associated Production of TFA
on Aquatic Communities and Local Air Quality.  Docket number
EPA-HQ-OAR-2008-0664-0037

ICF, 2010a.  ICF International.  2010.  Summary of HFO-1234yf Emissions
Assumptions.

ICF, 2010b.  ICF International.  2010.  Revised Assessment of the
Potential Impacts of HFO-1234yf and the Associated Production of TFA on
Aquatic Communities, Soil and Plants, and Local Air Quality. 

ICF, 2010c.  ICF International.  2010.  Sensitivity Analysis CMAQ
results on projected maximum TFA rainwater concentrations and maximum
8-hr ozone concentrations. 

ICF, 2010d.  ICF International.  2010.  Analysis of Potential Impacts of
Aldehydes as Breakdown Products from HFO-1234yf.

ICF, 2010e.  ICF International.  2010.  Summary of Updates to the
Vintaging Model that Impacted HFO-1234yf Emissions Estimates.

IPCC, 2007.  Contribution of Working Group I to the Fourth Assessment
Report of the Intergovernmental Panel on Climate Change, 2007.  Solomon,
S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and
H.L. Miller (eds.).  Cambridge University Press, Cambridge, United
Kingdom and New York, NY, USA.  Available online at   HYPERLINK
"http://www.ipcc.ch/publications_and_data/ar4/wg1/en/contents.html" 
http://www.ipcc.ch/publications_and_data/ar4/wg1/en/contents.html  .

JAMA, 2008.  “LCCP Result from JAMA,” Japan Automobile Manufacturers
Association , T. Ikegami; K. Inui; K. Aoki. VDA Alternative Refrigerant
Winter Meeting, Saalfelden, Austria, February 13-14, 2008.  Available
online at   HYPERLINK
"http://www.vda-wintermeeting.de/fileadmin/downloads2008/presentations/T
ohru_Ikegami_Toyota_Kenta_Aoki_Nissan_JAMA.pdf" 
http://www.vda-wintermeeting.de/fileadmin/downloads2008/presentations/To
hru_Ikegami_Toyota_Kenta_Aoki_Nissan_JAMA.pdf   (begins, p. 23)

JAMA-JAPIA, 2008.  ”New Refrigerants Evaluation Results” Japan
Automobile Manufacturers Association-Japan Auto Parts Industries
Association Consortium.  T. Ikegami, M. Iguchi, K. Aoki, K. Iijima; VDA
Alternative Refrigerant Winter Meeting, Saalfelden, Austria, February
13-14, 2008.  Available online at   HYPERLINK
"http://www.vda-wintermeeting.de/fileadmin/downloads2008/presentations/T
ohru_Ikegami_Toyota_Kenta_Aoki_Nissan_JAMA.pdf" 
http://www.vda-wintermeeting.de/fileadmin/downloads2008/presentations/To
hru_Ikegami_Toyota_Kenta_Aoki_Nissan_JAMA.pdf  .

Kajihara et al., 2010.  “Estimation of environmental concentrations
and deposition fluxes of R-1234-YF and its decomposition products
emistted from air conditioning equipment to atmosphere”.  H. Kajihara,
K. Inoue, K. Yoshida, R. Nagaosa.  February 17-19, 2010.  2010
International Symposium on Next-generation Air Conditioning and
Refrigeration Technology.  Docket number EPA-HQ-OAR-2008-0664-0114.1

Kirkland et al. (2005) Evaluation of a battery of three in vitro
genotoxicity tests to determine rodent carcinogens and non-carcinogens.
I. Sensitivity, specificity and relative predictivity, Mutation
Research, 584, 1-256.  Available online at   HYPERLINK
"http://www.sciencedirect.com"  www.sciencedirect.com .

Luecken et al., 2009. Luecken, D.J., Waterland, R.L., Papasavva, S.,
Taddonio, K.N., Hutzell, W.T., Rugh, J.P., Andersen, S.O. 2009.  Ozone
and TFA Impacts in North America from the Degradation of
2,3,3,3-Tetrafluoropropene (HFO-1234yf), A Potential Greenhouse Gas
Replacement. Environ. Sci. Technol., submitted for publication.  Docket
number EPA-HQ-OAR-2008-0664-0112.3

Meyer, 2008.  “R-1234yf System Enhancements and Comparison to
R-134a.” 2008, Alternative Refrigerant Systems Symposium Phoenix, AZ 
Available online at   HYPERLINK
"http://www2.dupont.com/Refrigerants/en_US/assets/downloads/SmartAutoAC/
2008_SAE_ARSS_Visteon_Eval.pdf" 
http://www2.dupont.com/Refrigerants/en_US/assets/downloads/SmartAutoAC/2
008_SAE_ARSS_Visteon_Eval.pdf 

Monforte et al., 2008 ”Updated situation about alternative refrigerant
evaluation” June 10-12, 2008, Alternative Refrigerant Systems
Symposium Phoenix, AZ.    HYPERLINK
"http://www2.dupont.com/Refrigerants/en_US/assets/downloads/SmartAutoAC/
2008_SAE_ARSS_Renault_Fiat_PSA_Eval.pdf" 
http://www2.dupont.com/Refrigerants/en_US/assets/downloads/SmartAutoAC/2
008_SAE_ARSS_Renault_Fiat_PSA_Eval.pdf 

Nielsen et al., 2007.  Nielsen, O.J., Javadi, M.S., Sulbaek Andersen,
M.P., Hurley, M.D., Wallington, T.J., Singh, R. 2007. Atmospheric
chemistry of CF3CF=CH2: Kinetics and mechanisms of gas-phase reactions
with Cl atoms, OH radicals, and O3. Chemical Physics Letters 439, 18-22.
 Available online at   HYPERLINK
"http://www.cogci.dk/network/OJN_174_CF3CF=CH2.pdf" 
http://www.cogci.dk/network/OJN_174_CF3CF=CH2.pdf .

NRC, 1981.  Atmosphere-Biosphere Interactions:  Toward a Better
Understanding of the Ecological Consequences of Fossil Fuel Combustion. 
Committee on the Atmosphere and the Biosphere, Board on Agriculture and
Renewable Resources, Commission on Natural Resources, National Research
Council.  1981.  Available from NRC Press or online at   HYPERLINK
"http://www.nap.edu/catalog.php?record_id=135" 
http://www.nap.edu/catalog.php?record_id=135 .

NRC, 1996.  NRC Toxicity of Alternatives to Chlorofluorocarbons:
HFC-134a and HCFC-123 (1996).  Available online at
http://www.nap.edu/openbook.php?record_id=9268&page=29.

NRC, 2004.    HYPERLINK "http://www.nap.edu/catalog.php?record_id=10902"
 Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume
4  (2004) Board on Environmental Studies and Toxicology.  The National
Academies Press.  Available online at
http://www.nap.edu/openbook.php?record_id=10902&page=127#p2000a02f996012
7001.

Orkin et al., 1997.  Rate constants for the reactions of OH with
HFC-245cb (CH3CF2CF3) and some fluoroalkenes (CH2CHCF3, CH2CFCF3,
CF2CFCF3, and CF2CF2),  Journal of Physical Chemistry A 101 (1997),
pp.9118-9124. Available online at
http://pubs.acs.org/doi/abs/10.1021/jp971994r.

Papadimitriou et al., 2007.  CF3CF=CH2 and (Z)-CF3CF=CHF:  temperature
dependent OH rate coefficients and global warming potentials.  V.
Papadimitriou, R Talukdar, R. Portmann, A. Ravishankaraa and J.
Burkholder.  Phys. Chem. Chem. Phys., 2007, Vol. 9, p. 1–13.  Docket
number EPA-HQ-OAR-2008-0664-0002.  Available online at   HYPERLINK
"http://pubs.rsc.org/en/Content/ArticleLanding/2008/CP/b714382f" 
http://pubs.rsc.org/en/Content/ArticleLanding/2008/CP/b714382f . 

Papasavva et al., 2009.  Estimated 2017 Refrigerant Emissions of
2,3,3,3-tetrafluoropropene (HFC-1234yf) in the United States Resulting
from Automobile Air Conditioning.  Environ. Sci. Technol. 2009.  43 pp.
9252-9259.  Docket number EPA-HQ-OAR-2008-0664-0112.1.  Available online
at http://www.ncbi.nlm.nih.gov/pubmed/20000517.

Parodi et al., 1982.  Predictive ability of the autoradiographic repair
assay in rat liver cells compared with the Ames test ; S. Parodi; M.
Taningher; C. Balbi ;L. Santi  . Journal of Toxicology and
Environmental Health, Vol.   HYPERLINK
"http://www.informaworld.com/smpp/title~db=all~content=t713667303~tab=is
sueslist~branches=10" \l "v10" \o "Click to view volume" \t "_top"   10,
Issue 4 & 5 October 1982 , pages 531 – 539.  Available online at  
HYPERLINK
"http://www.informaworld.com/smpp/content~db=all~content=a915968516" 
http://www.informaworld.com/smpp/content~db=all~content=a915968516 .

Ravishankara et al., 1993.  Do Hydrofluorocarbons Destroy Stratospheric
Ozone?  A. R. Ravishankara, Andrew A. Turnipseed, Niels R. Jensen,
Stephen Barone, Michael Mills, Carleton J. Howard, and Susan Solomon.
Science,  Vol. 263. no. 5143, pp. 71 – 75.  January 4, 1994. 
Available online at
http://www.sciencemag.org/cgi/content/abstract/263/5143/71.

Rhasa and Zellner, 1987.  Atmospheric Oxidation of Hydrocarbons. Free
Radical Research 1987, Vol. 3, No. 1-5:  Pages 199-209. Available online
at   HYPERLINK
"http://informahealthcare.com/doi/abs/10.3109/10715768709069785" 
http://informahealthcare.com/doi/abs/10.3109/10715768709069785  .

Sciance, 2010.  “General Motors R-1234yf Implementation,”
Presentation by Fred Sciance, General Motors to EPA staff.  October 28,
2010.  Docket number EPA-HQ-OAR-2008-0664-0xxx.

Spatz, 2008.  Spatz, M and B. Minor 2008 “HFO-1234yf: A Low GWP
Refrigerant for MAC”, VDA Winter meeting.  Available online at  
HYPERLINK
"http://www2.dupont.com/Refrigerants/en_US/assets/downloads/SmartAutoAC/
MAC_VDA08_HFO_1234yf.pdf" 
http://www2.dupont.com/Refrigerants/en_US/assets/downloads/SmartAutoAC/M
AC_VDA08_HFO_1234yf.pdf . 

SROC, 2005.  Chapter 3 from Safeguarding the Ozone Layer and the Global
Climate System:  Special Report of the Intergovernmental Panel on
Climate Change.  Edited by Bert Metz, Lambert Kuijpers, Susan Solomon,
Stephen O. Anderson, Ogunlade Davidson, Jose Pons, David de Jager, Tahl
Kestin, Martin Manning and Leo Meyer.  Cambridge University Press. 
2005.  Available online at
http://www.cambridge.org/catalogue/catalogue.asp?isbn=9780521682060.

TNO, 2005.  Sub-acute (2-week) Inhalation Toxicity Study with HFO-1234yf
in Rats.  2005.  Docket number EPA-HQ-OAR-2008-0664-0020 and attachments
-0020.1 through -0020.4. 

TNO, 2007a.  Sub-chronic (13-week) inhalation toxicity study with
HFO-1234yf in rats.  2007. Docket number EPA-HQ-OAR-2008-0664-0022 and
attachments -0022.1 through -0022.5.

TNO, 2007b.  Prenatal Developmental Inhalation Toxicity Study with
HFO-1234yf in Rats.  2007. Docket number EPA-HQ-OAR-2008-0664-0023 and
attachments -0023.1 through -0023.9.

US EPA, 1994.  U.S. Environmental Protection Agency (US EPA).  1994. 
Methods for derivation of inhalation reference concentrations and
application of inhalation dosimetry.  EPA/600/8-90/066F.  Office of
Health and Environmental Assessment, Washington, DC.  1994. Available
online at   HYPERLINK
"http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=71993" 
http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=71993 

US EPA, 2000.  Hazard Summary for Formaldehyde, CAS ID# 50-00-0. 
Revised 2000.  Available online at   HYPERLINK
"http://www.epa.gov/ttn/atw/hlthef/formalde.html" 
http://www.epa.gov/ttn/atw/hlthef/formalde.html 

US EPA, 2010a.  Email from Yaidi Cancel, EPA. To William Hill and Ward
Atkinson, SAE Interior Climate Control Committee re:  Minimum
recordkeeping on SAE J1739.  August 16, 2010.

US EPA, 2010b.  Email from Margaret Sheppard, EPA to Christopher Seeton
and Kasia Bober, Honeywell re:  Summary of our conference call on
service fittings for HFO-1234yf.  November 8, 2010.

US EPA, 2010c.  Clarifying questions for Honeywell on Exposure Study. 
Docket number EPA-HQ-OPPT-2008-0918-0095.

Wallington et al., 2008.  Emissions of CO2, CO, NOx, HC, PM, HFC-134a,
N2O and CH4 from the Global Light Duty Vehicle Fleet.  Meterolo. Z. 17.
109-116.  Available online at   HYPERLINK
"http://www.schweizerbart.de/resources/downloads/paper_free/56618.pdf" 
http://www.schweizerbart.de/resources/downloads/paper_free/56618.pdf 

Wallington et al., 2010.  “Estimated Photochemical Ozone Creation
Potentials (POCPs) of CF3CF=CH2 (HFO-1234yf) and Related
Hydrofluoroolefins (HFOs).”  T. Wallington, M. Andersen, O. Nielsen. 
Atmospheric Environment, in press 2010. Docket number
EPA-HQ-OAR-2008-0664-0084.2.  Available online at   HYPERLINK
"http://www.sciencedirect.com"  http://www.sciencedirect.com  or at  
HYPERLINK "http://dx.doi.org/10.1016/j.atmosenv.2010.01.040" \t
"doilink"  doi:10.1016/j.atmosenv.2010.01.040 . 

Weissler, P., 2008.  “Consensus Building on Refrigerant Type.” 
Automotive Engineering 

Protection of Stratospheric Ozone:  New Substitute in the Motor Vehicle
Air Conditioning Sector under the Significant New Alternatives Policy
(SNAP) Program (Page   PAGE  130  of   NUMPAGES  134 )

International.  9: 30-32.  Docket number EPA-HQ-OAR-2008-0664-0006.

WIL, 2006.  Acute Cardiac Sensitization Study of [name redacted] and
HFO-1234yf in Dogs.  WIL Laboratories, 2006.  Docket number
EPA-HQ-OAR-2008-0664-0019 and attachments -0019.1 through -0019.2.

List of Subjects in 40 CFR Part 82

	Environmental protection, Administrative practice and procedure, 

Air pollution control, Reporting and recordkeeping requirements,
Stratospheric ozone layer.

Dated: ______________________________________

_____________________________________________ 

Lisa P. Jackson,

Administrator.

For the reasons set out in the preamble, 40 CFR part 82 is amended as

follows:

PART 82--PROTECTION OF STRATOSPHERIC OZONE

1. The authority citation for part 82 continues to read as follows:

   Authority: 42 U.S.C. 7414, 7601, 7671-7671q.

Subpart G--Significant New Alternatives Policy Program

2.  The first table in Subpart G to Appendix B of Part 82 is amended by
adding one new entry to the end of the table to read as follows:

Appendix B to Subpart G of Part 82 - Substitutes Subject to Use
Restrictions and Unacceptable Substitutes

REFRIGERANTS-ACCEPTABLE SUBJECT TO USE CONDITIONS

Application	Substitute	Decision	Conditions	Comments

*****

CFC-12 Automobile Motor Vehicle Air Conditioning (New equipment in
passenger cars and light-duty trucks only)	HFO-1234yf as a substitute
for CFC-12	Acceptable subject to use conditions	The high-pressure side
of the MVAC system shall have a pressure relief device located in the
high pressure side of the compressor or immediately adjacent to the
compressor discharge fitting.  The device shall release refrigerant only
outside of the passenger, trunk, and storage compartments and MVAC air
distribution system. These pressure relief devices shall be designed to
minimize impingement of the refrigerant and oil on hot surfaces.

The MVAC system high-pressure side relieve device identified above in 1
shall be self-sealing.  In no case shall the maximum release (blow-off)
pressure be greater than the maximum refrigerant working pressure.

To prevent unnecessary discharge of refrigerant during operation, the
system shall have a means to limit the compressor operation by cutting
off transmission of power to the compressor before any component failure
occurs and before activation of any pressure relief device (i.e.,
compressor cutoff switch).

In no case shall any high-pressure side refrigerant pressure relief
valves (or burst disks) have an activation pressure greater than the
maximum working pressure of 4.14 MPa. Gauge (600 psig).  

The maximum pressure on the low-pressure side of the MVAC system shall
not exceed the saturation pressure of HFO-1234yf at 56oC.

HFO-1234yf refrigerant systems connections shall either be:

Located outside the passenger compartment and outside the passenger
cabin airflow path.

or

Designed to prevent leakage if the connections are located inside the
passenger cabin or in the passenger cabin airflow path.  For safety
reasons, individuals performing servicing shall follow the service and
repair leakage recommendations (e.g., from manufacturer and in service
shop manual), including any service procedures established to prevent
refrigerant from entering the cabin or airflow path.

High-side and low-side fittings shall be fitted with protective or
sealing caps.

All MVAC system service fittings shall be located for ease of attachment
of service hoses and shall be designed to minimize direct impingement of
refrigerant on the service technician.  Piping shall be of robust design
to avoid damage or permanent deformation while connecting or
disconnecting the service hose coupling(s) from factory charging and
service equipment.

HFO-1234yf must be used with the following service fittings:

For the low-side service port, use quick-connect fittings with an
outside diameter of 14 + 0.2 mm (0.551 + 0.00787 inches).  

For the high-side service port, use quick-connect fittings with an
outside diameter of 17 + 0.2 mm (0.669 + 0.00787 inches).

For connections with containers of 20 lbs or greater, use quick-connect
fittings with an outside diameter of 14 + 0.2 mm (0.551 + 0.00787
inches).

All fittings must be different from those for any other refrigerant.

10.  A plainly legible and durable refrigerant label shall be mounted in
a clearly visible location under hood that does not require the removal
of any parts or covers to be read.  The label shall:  identify the
refrigerant; state the amount of refrigerant charge in grams (or
kilograms, to three decimal places); and identify the lubricant type
(polyalkylene glycol [PAG] or polyolester [POE]). The label either shall
include the chemical safety symbol for “flammable” or shall state in
text that the refrigerant is flammable in letters at least 3 mm in
height that are red in color.  The label shall contain the name or logo
of the original equipment vehicle manufacturer or the refrigeration
system manufacturer responsible for design compliance with this rule and
with SAE standards.  The label shall have a minimum size of 60 mm by 30
mm.  It shall have text in bold-type letters at least 3 mm in height for
identifying refrigerant, lubricant type and refrigerant amount.  If the
label contains text only and no symbols, the label shall also state the
following:

“CAUTION SYSTEM CONTAINS REFRIGERANT R-1234yf UNDER HIGH PRESSURE-TO
BE SERVICED ONLY BY QUALIFIED PERSONNEL” 

11.  Manufacturers must conduct Failure Mode and Effect Analysis (FMEA)
as provided in SAE J1739 (adopted 2009).  Manufacturers must keep the
FMEA on file for at least three years from the date of creation. 

	Additional training for service technicians recommended.

Observe requirements of Significant New Use Rule at 40 CFR 721.10182. 





3.  Appendix B to Subpart G is amended by revising the entry for
``CFC-12 Motor Vehicle Air Conditioners (Retrofit and New
Equipment/NIKs)'' in the table titled ``Refrigerants--Unacceptable
Substitutes'' to read as follows:

Refrigerants--Unacceptable Substitutes

                                                  * * * * * 

End -use	Substitute	Decision	Comments

CFC-12 Motor Vehicle Air Conditioners (Retrofit and New Equipment/NIKs)
R-405A....... 	Unacceptable. 	R-405A contains R-c318, a PFC, which has
an extremely high GWP and lifetime. Other Substitutes exist which do not
contain PFCs.

	Hydrocarbon Blend B....  	Unacceptable. 	Flammability is a serious
concern.  Data have not been submitted to demonstrate it can be used
safely in this end-use.                                                 
                       

	Flammable Substitutes, other than R-152a or HFO-1234yf in new
equipment.   	Unacceptable. 	The risks associated with using flammable
substitutes (except R-152a and HFO-1234yf) in this end-use have not been
addressed by a risk assessment. R-152a and HFO-1234yf may be used in new
equipment with the use conditions in appendix B to this subpart. 

                                       

[FR Doc.              ]

BILLING CODE 6560-50-P

 The safety requirements cited here are from sections 5, 7, 9, 10, and
12 of the draft standard SAE J 639 (System and Component Requirements;
Service Port Fittings; Service Fitting Caps; Requirements for MAC System
Labeling; and Refrigerant Line Routing and Refrigerant Connections). 

 Assumes a fleet of approximately 250 million passenger vehicles and
typical vehicle operation of 500 hours per year.  Sources:  U.S. Census,
  HYPERLINK
"http://www.census.gov/compendia/statab/2010/tables/10s1060.pdf" 
http://www.census.gov/compendia/statab/2010/tables/10s1060.pdf ; SAE
J2766, as cited in EPA-HQ-OAR-2008-0664-0056.2

 HFC-134a is also known as 1,1,1,2-tetrafluoroethane or, when used as a
refrigerant, R-134a.  The Chemical Abstracts Service Registry Number
(CAS Reg. No.) is 811-97-2.

 HFC-152a is also known as 1,1-difluoroethane or, when used as a
refrigerant, R-152a.  The CAS Reg. No.  is 75-37-6.

 The draft SAE J639 standard specifies unique fittings for high-side and
low-side service ports and the manufacturer of HFO-1234yf supports these
fittings.  The unique fitting for large containers for use in servicing
by professionals (e.g., 20 or 30 lbs) is the same as the fitting for the
low-side service port in draft SAE J639 and is also specified in SAE J
2844, “R-1234yf New Refrigerant Purity and Container Requirements Used
in Mobile Air-Conditioning Systems.”  (US EPA, 2010b)

 These changes in estimates reflect ongoing updates to EPA’s Vintaging
Model, a model that considers industry trends in different end-uses that
historically have used ODS. 

 Analyzed scenarios considered HFO-1234yf emissions from MVAC and from
both MVAC systems and stationary air conditioning and refrigeration
systems.  The analysis also considered scenarios with typical emissions
from MVAC systems during the entire year similar to those from current
MVAC systems using HFC-134a and another scenario with reduced emissions
of HFO-1234yf of approximately 50 g/yr per vehicle, in line with
emissions estimates in a study by Papasavva et al. (2009)
(EPA-HQ-OAR-2008-0664-0114.1).  Major differences between the data
sources include assumptions of a lower leak rate (5.6% of charge vs. 8%
of charge) and a lower annualized rate of leaks during servicing (3.2%
of charge vs. 10% of charge) for the Papasavva et al. paper compared to
assumptions in EPA’s Vintaging Model (ICF 2010a).

 On September 30, 2010, we received a final report from the German
Federal Environment Agency (UBA) with additional information from
testing of HFO-1234yf’s potential for flammability and for generating
hydrogen fluoride.  Although this comment was received too late in the
rulemaking process for us to analyze it in depth, our preliminary review
found that the procedures they used contain many unrealistic provisions
that are not relevant to our decision and in some tests did not provide
proper controls (e.g., lacking a comparison to HFC-134a under the same
conditions).  Concerning flammability risk, the results do not vary
significantly from those we are relying on for the final rule. Thus, our
preliminary review of the UBA test procedures and results does not
suggest that we should re-evaluate our decision to find HFO-1234yf
acceptable subject to use conditions. 

 This was based on a NOAEL of 4000 ppm from the study, “An Inhalation
Prenatal Developmental Toxicity Study of HFO-1234yf
(2,3,3,3-Tetrafluoropropene) in Rabbits,” EPA-HQ-OAR-2008-0664-0041.
We used a factor of 1.9 to account for differences in blood
concentrations between animals and humans, and a margin of exposure or
collective uncertainty factor of 30.  Uncertainty factors of 3 were
assigned for animal to human extrapolation, and 10 for variability
within the human population.  The long-term workplace exposure limit was
calculated as follows: 4000 ppm (animal exposure) x 1.9 (ratio of
estimated human exposure/animal exposure) x 1/3 (UF for animal to human
extrapolation) x 1/10 (UF for variability within the human population)
exposure) = 250 ppm.  This value was compared against 8-hour average
concentrations.  See EPA-HQ-OAR-2008-0664-0036 and
EPA-HQ-OAR-2008-0664-0038.

 This was based on a NOAEL of 51,690 ppm from the study, “Sub-acute
(2-week) Inhalation Toxicity Study with HFO-1234yf in rats,”
EPA-HQ-OAR-2008-0664-0020 through-0020.4, a factor of 1.9 to account for
differences in blood concentrations between animals and humans  and a
margin of exposure or collective uncertainty factor of 30.  Uncertainty
factors of 3 were assigned for animal to human extrapolation, and 10 for
variability within the human population.  The short-term workplace
exposure value was calculated as follows: 51,690 ppm (animal exposure) x
1.9 (ratio of estimated human exposure/animal exposure)=  98,211 ppm 
This value was then divided by the expected exposure in each scenario,
and compared against the target margin of exposure of 30.  See
EPA-HQ-OAR-2008-0664-0036 and EPA-HQ-OAR-2008-0664-0038.

.  These are based on the 8-hr Workplace Environmental Exposure Limit
(WEEL) for HFO-1234yf and for short-term exposure, assuming a NOAEL of
approximately 405,800 ppm from the study, “Acute (4-hour) inhalation
toxicity study with HFO-1234yf in rats.”  Note that EPA disagrees with
the finding that the acute inhalation toxicity study found a NOAEL.  We
consider this study to show adverse effects at all levels because of the
presence of grey discoloration in the lungs of the test animals.  In
order to ensure sufficient protection, EPA’s risk assessment used a
NOAEL from a subacute study instead of a LOAEL from an acute study. 

 EPA has issued lists of approved unique fittings for refrigerants in
MVAC (see   HYPERLINK
"http://www.epa.gov/ozone/snap/refrigerants/fittlist.html" 
http://www.epa.gov/ozone/snap/refrigerants/fittlist.html ).  These have
been issued for the high-side service port, low-side service port, 30-lb
cylinders (that is, the most typical size container for use in
professional servicing), and small cans (containers typically used by
consumers).  The label “30-lb cylinders” is not intended to restrict
the existence of other container sizes that professional service
technicians might use (e.g., 50 lb, 20 lb, 10 lb).

 The AEGL-2 is defined as “the airborne concentration of a substance
…above which it is predicted that the general population, including
susceptible individuals could experience irreversible or other serious,
long lasting adverse effects or an impaired ability to escape.” 
http://www.epa.gov/oppt/aegl/pubs/define.htm

 If we assume 250 million passenger vehicles in the US and typical
driving times of 500 hours per year per vehicle, a risk of 4.6 x 10-12
per operating hour equates roughly to one event every 2 years for all
drivers in the entire U.S.

 Service for consideration means receiving something of worth or value
to perform service, whether in money, credit, goods, or services.

 EPA previously reviewed two hydrocarbon blends for use in MVAC and
found them unacceptable, stating “Flammability is a serious concern. 
Data have not been submitted to demonstrate that [the hydrocarbon blend]
can be used safely in this end-use.”  Appendixes A and B to subpart G
of 40 CFR part 82.                                                      
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                                        
                                                              

 The Agency for Toxic Substances and Disease Registry (ATSDR) has
established a chronic inhalation minimal risk level (MRL) of 0.008 ppm
(8,000 ppt) for formaldehyde (ICF, 2010d).  MRLs are available online at
http://www.atsdr.cdc.gov/mrls/mrls_list.html.

 EPA has established a Reference Concentration (RfC) of 0.005 ppm (5,000
ppt or 0.009 mg/m3) for acetaldehyde (ICF, 2010d).  A summary of EPA’s
documentation for its risk assessment and RfC derivation for
acetaldehyde is available online at
http://www.epa.gov/ncea/iris/subst/0290.htm.

 Papasavva et al. (2009) includes several sources of emissions of
automobile refrigerant, including regular leaks through hoses, irregular
leaks, refrigerant loss during servicing, and refrigerant loss at end of
vehicle life. 

 Prepublication version of Wallington et al., 2010 (Docket item
EPA-HQ-OAR-2008-0664-0084.2)

 Predictive ability of the autoradiographic repair assay in rat liver
cells compared with the Ames test ; S. Parodi; M. Taningher; C.
Balbi; L. Santi   Journal of Toxicology and Environmental Health, Vol.  
HYPERLINK
"http://www.informaworld.com/smpp/title~db=all~content=t713667303~tab=is
sueslist~branches=10" \l "v10" \o "Click to view volume" \t "_top"   10,
Issue 4 & 5 October 1982, pages 531 – 539.

 Kirkland et al. (2005) Evaluation of a battery of three in vitro
genotoxicity tests to determine rodent carcinogens and non-carcinogens.
I. Sensitivity, specificity and relative predictivity, Mutation
Research, 584, 1-256.

 The Agency for Toxic Substances and Disease Registry (ATSDR) has
established a chronic inhalation minimal risk level (MRL) of 0.008 ppm
(8,000 ppt) for formaldehyde (ICF, 2010d).  MRLs are available at
http://www.atsdr.cdc.gov/mrls/mrls_list.html.

 EPA has established a Reference Concentration (RfC) of 0.005 ppm (5,000
ppt or 0.009 mg/m3) for acetaldehyde (ICF, 2010d).  A summary of EPA’s
documentation for its risk assessment and RfC derivation for
acetaldehyde is available online at
http://www.epa.gov/ncea/iris/subst/0290.htm.

 An AEGL-2 is intended to apply to an emergency situation where someone
would try to move away from the hazard in a short period of time and may
suffer some temporary irritation, but no permanent health damage. 
Irreversible or disabling but non-fatal health effects could occur
between the AEGL-2 and the higher AEGL-3.

 The regulations for the SNAP program include cost and availability as
one of the criteria for review as to whether a substitute is acceptable
or unacceptable as a replacement for ozone depleting substances
(82.180(a)(7)(vii)), along with a number of criteria for different
aspects of health and environmental impacts.  Cost and availability are
included as criteria because they affect assumptions we may make about a
substitute regarding its risks, i.e., we need to know its cost and
availability so we can make assumptions about the risk it might pose. 
In this case, we assumed that HFO-1234yf would be used widely across the
industry in new MVACs because widespread use of a single refrigerant in
new car models has been the industry practice with MVAC systems.  Thus,
more detail on cost and availability of the substitute was not necessary
in order to identify assumptions we should make for estimating risk.  

 As defined at 40 CFR 82.104 “interstate commerce” means the
distribution or transportation of any product between one state,
territory, possession or the District of Columbia, and another state,
territory, possession or the District of Columbia, or the sale, use or
manufacture of any product in more than one state, territory, possession
or District of Columbia.  The entry points for which a product is
introduced into interstate commerce are the release of a product from
the facility in which the product was manufactured, the entry into a
warehouse from which the domestic manufacturer releases the product for
sale or distribution, and at the site of United States Customs
clearance.

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