6560-50-P

	ENVIRONMENTAL PROTECTION AGENCY

	40 CFR Part 63			

	[OAR-2003-0189; FRL-]

	RIN: 2060-AK73 			

List of Hazardous Air Pollutants, Petition Process, Lesser Quantity
Designations, Source Category List

AGENCY:  Environmental Protection Agency (EPA).		

ACTION:  Proposed rule.

SUMMARY:  The EPA is proposing to amend the list of categories of
sources that was developed pursuant to section 112(c)(1) of the Clean
Air Act (CAA) by deleting four subcategories from the stationary
combustion turbine source category.  A final maximum achievable control
technology (MACT) standard creating these subcategories was promulgated
on August 29, 2003.  The MACT standard will be codified at 40 CFR part
63, subpart YYYY.  These subcategories are (1) lean premix gas-fired
stationary combustion turbines as defined in 40 CFR 63.6175 (referred to
herein as lean premix gas-fired turbines), (2) diffusion flame gas-fired
stationary combustion turbines as defined in 40 CFR 63.6175 (referred to
herein as diffusion flame gas-fired turbines), (3) emergency stationary
combustion turbines as defined in 40 CFR 63.6175, and (4) stationary
combustion turbines located on the North Slope of Alaska, as defined in
40 CFR 63.6175.  This action is being taken in part to respond to a
petition submitted by the Gas Turbine Association (GTA) and in part upon
the Administrator’s own motion.  Petitions to remove a source category
from the source category list are permitted under section 112(c)(9) of
the CAA.

The proposed rule is based on EPA’s evaluation of the available
information concerning the potential hazards from exposure to the
hazardous air pollutants (HAP) emitted from these four subcategories. 
Today’s action includes a detailed rationale for removing lean premix
gas-fired turbines, diffusion flame gas-fired turbines, emergency
stationary combustion turbines and turbines operated on the North Slope
of Alaska from the source category list.  We request comment on the
proposal.						

Although the rule proposes to delete certain subcategories from the
stationary combustion turbines source category, the MACT standard for
those subcategories will take effect upon publication of the standard. 
Because the  MACT standard requires immediate compliance by new sources,
some sources in the subcategories which we are proposing to delist may
need to make immediate expenditures on emission controls which will not
be required if we adopt a final rule to delete these subcategories.  In
view of our initial determination that the statutory criteria for
delisting have been met for these subcategories, we consider it
inappropriate and contrary to statutory intent to mandate such
expenditures until after a final determination has been made whether or
not these subcategories should be delisted.  

Accordingly, we are publishing elsewhere in today’s Federal Register a
proposed rule to stay the enforcement of the emission standards for new
sources in these subcategories during the pendency of the rule to delete
these subcategories.

DATES:  Comments.  Written comments on the proposed rule must be
received by [INSERT DATE 60 DAYS FROM PUBLICATION OF THIS PROPOSED RULE
IN THE FEDERAL REGISTER].

Public Hearing.  A public hearing regarding the proposed rule will be
held if requests to speak are received by the EPA on or before [INSERT
DATE 15 DAYS FROM PUBLICATION OF THIS PROPOSED RULE IN THE FEDERAL
REGISTER].  If requested, a public hearing will be held on [INSERT DATE
28 DAYS FROM PUBLICATION OF THIS PROPOSED RULE IN THE FEDERAL REGISTER].
ADDRESSES:  Comments.  Comments may be submitted electronically, by
mail, or through hand delivery/courier.  Electronic comments may be
submitted on-line at http://www.epa.gov/edocket/.  Written comments sent
by U.S. mail should be submitted (in duplicate if possible) to:  Air and
Radiation Docket and Information Center (Mail Code 6102T), Attention
Docket ID Number OAR-2003-0189, Room B108, U.S. EPA, 1200 Pennsylvania
Avenue, NW., Washington, DC 20460.  Written comments delivered in person
or by courier should be submitted (in duplicate if possible) to:  Air
and Radiation Docket and Information Center (Mail Code 6102T), Attention
Docket ID Number OAR-2003-0189, Room B102, U.S. EPA, 1301 Constitution
Avenue, NW., Washington, DC 20460.  The EPA requests a separate copy
also be sent to the contact person listed below (see FOR FURTHER
INFORMATION CONTACT).

Public Hearing.  If a public hearing is requested by [INSERT DATE 15
DAYS FROM PUBLICATION OF THIS PROPOSED RULE IN THE FEDERAL REGISTER] the
public hearing will be held at the EPA facility complex, T.W. Alexander
Drive, Research Triangle Park, NC [INSERT DATE 28 DAYS FROM PUBLICATION
OF THIS PROPOSED RULE IN THE FEDERAL REGISTER].  Persons interested in
presenting oral testimony should contact Ms. Kelly A. Rimer, Risk and
Exposure Assessment Group, Emission Standards Division (C404-01), U.S.
EPA, Research Triangle Park, North Carolina 27711, telephone number
(919) 541-2962.  Persons interested in attending the public hearing
should also contact Ms. Rimer to verify the time of the hearing. 

FOR FURTHER INFORMATION CONTACT:  Ms. Kelly A. Rimer, Risk and Exposure
Assessment Group, Emission Standards Division (C404-01), U.S. EPA,
Research Triangle Park, NC 27711, telephone number (919) 541-2962,
electronic mail address rimer.kelly@epa.gov.

SUPPLEMENTARY INFORMATION:

Regulated Entities.  Categories and entities potentially regulated by
this action include:

------------------------------------------------------------

  Category      SIC   NAICS          Examples of

                                  regulated entities

------------------------------------------------------------

Any industry	4911  2211	Electric power generation, 

using a	                    transmission, or stationary     combustion  
                 distribution

turbine as	4922  486210	Natural gas transmission

defined    	1311	 211111	Crude petroleum and natural

in the				     gas production

regulation.	1321  211112	Natural gas liquids producers

4931	 221		Electric and other services 

combined	 		

This table is not intended to be exhaustive, but rather provides a guide
for readers regarding entities likely to be affected by this action.  If
you have any questions regarding the applicability of this action to a
particular entity, consult the person listed in the preceding FOR
FURTHER INFORMATION CONTACT section.

Docket.  The EPA has established an official public docket for this
action under Docket ID Number OAR-2003-0189.  The official public docket
is the collection of materials that is available for public viewing at
the EPA Docket Center (Air Docket), EPA West, Room B-108, 1301
Constitution Avenue, NW, Washington, DC 20004.  The Docket Center is
open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal
holidays.  The telephone number for the Reading Room is (202) 566-1744,
and the telephone number for the Air Docket is (202) 566-1742.

Electronic Access.  An electronic version of the public docket is
available through EPA’s electronic public docket and comment system,
EPA Dockets.  You may use EPA Dockets at http://www.epa.gov/edocket/ to
submit or view public comments, access the index of the contents of the
official public docket, and access those documents in the public docket
that are available electronically.  Once in the system, select "search"
and key in the appropriate docket identification number.

Certain types of information will not be placed in the EPA dockets. 
Information claimed as confidential business information (CBI) and other
information whose disclosure is restricted by statute, which is not
included in the official public docket, will not be available for public
viewing in EPA’s electronic public docket.  The EPA’s policy is that
copyrighted material will not be placed in EPA’s electronic public
docket but will be available only in printed, paper form in the official
public docket.  Although not all docket materials may be available
electronically, you may still access any of the publicly available
docket materials through the EPA Docket Center.

For public commenters, it is important to note that EPA’s policy is
that public comments, whether submitted electronically or in paper, will
be made available for public viewing in EPA’s electronic public docket
as EPA receives them and without change unless the comment contains
copyrighted material, CBI, or other information whose disclosure is
restricted by statute.  When EPA identifies a comment containing
copyrighted material, EPA will provide a reference to that material in
the version of the comment that is placed in EPA’s electronic public
docket.  The entire printed comment, including the copyrighted material,
will be available in the public docket.

Public comments submitted on computer disks that are mailed or delivered
to the docket will be transferred to EPA’s electronic public docket. 
Public comments that are mailed or delivered to the docket will be
scanned and placed in EPA’s electronic public docket.  Where
practical, physical objects will be photographed, and the photograph
will be placed in EPA’s electronic public docket along with a brief
description written by the docket staff.

Comments.  You may submit comments electronically, by mail, by
facsimile, or through hand delivery/courier.  To ensure proper receipt
by EPA, identify the appropriate docket identification number in the
subject line on the first page of your comment.  Please ensure that your
comments are submitted within the specified comment period.  Comments
submitted after the close of the comment period will be marked
“late.”  The EPA is not required to consider these late comments.

Electronically.  If you submit an electronic comment as prescribed
below, EPA recommends that you include your name, mailing address, and
an e-mail address or other contact information in the body of your
comment.  Also include this contact information on the outside of any
disk or CD ROM you submit and in any cover letter accompanying the disk
or CD ROM.  This ensures that you can be identified as the submitter of
the comment and allows EPA to contact you in case EPA cannot read your
comment due to technical difficulties or needs further information on
the substance of your comment.  The EPA’s policy is that EPA will not
edit your comment and any identifying or contact information provided in
the body of a comment will be included as part of the comment that is
placed in the official public docket and made available in EPA’s
electronic public docket.  If EPA cannot read your comment due to
technical difficulties and cannot contact you for clarification, EPA may
not be able to consider your comment.

Your use of EPA’s electronic public docket to submit comments to EPA
electronically is EPA’s preferred method for receiving comments.  Go
directly to EPA Dockets at http://www.epa.gov/edocket, and follow the
online instructions for submitting comments.  Once in the system, select
“search” and key in Docket ID No. OAR-2003-0189.  The system is an
“anonymous access” system, which means EPA will not know your
identity, e-mail address, or other contact information unless you
provide it in the body of your comment.

Comments may be sent by electronic mail (e-mail) to 

a-and-r-docket@epa.gov, Attention Docket ID No. OAR-2003-0189.  In
contrast to EPA’s electronic public docket, EPA’s e-mail system is
not an “anonymous access” system.  If you send an e-mail comment
directly to the docket without going through EPA’s electronic public
docket, EPA’s e-mail system automatically captures your e-mail
address.  E-mail addresses that are automatically captured by EPA’s
e-mail system are included as part of the comment that is placed in the
official public docket and made available in EPA’s electronic public
docket.

You may submit comments on a disk or CD ROM that you mail to the mailing
address identified in this document.   These electronic submissions will
be accepted in WordPerfect or ASCII file format.  Avoid the use of
special characters and any form of encryption.

By Mail.  Send your comments (in duplicate, if possible) to:  EPA Docket
Center (Air Docket), U.S. EPA West, (MD-6102T), Room B-108, 1200
Pennsylvania Avenue, NW, Washington, DC 20460, Attention Docket ID No.
OAR-2003-0189 .

By Hand Delivery or Courier.  Deliver your comments (in duplicate, if
possible) to:  EPA Docket Center, Room B-108, U.S. EPA West, 1301
Constitution Avenue, NW, Washington, DC 20004, Attention Docket ID No.
OAR-2003-0189.  Such deliveries are only accepted during the Docket
Center’s normal hours of operation.

By Facsimile.  Fax your comments to: (202) 566-1741, Docket ID No.
OAR-2003-0189.

CBI.  Do not submit information that you consider to be CBI through
EPA’s electronic public docket or by e-mail.  Send or deliver
information identified as CBI only to the following address:  Kelly
Rimer, c/o Roberto Morales, OAQPS Document Control Officer (C404-02),
U.S. EPA, 109 TW Alexander Drive, Research Triangle Park, NC 27709,
Attention Docket ID No. OAR-2003- 0189.  You may claim information that
you submit to EPA as CBI by marking any part or all of that information
as CBI (if you submit CBI on disk or CD ROM, mark the outside of the
disk or CD ROM as CBI and then identify electronically within the disk
or CD ROM the specific information that is CBI).  Information so marked
will not be disclosed except in accordance with procedures set forth in
40 CFR part 2.	

In addition to one complete version of the comment that includes any
information claimed as CBI, a copy of the comment that does not contain
the information claimed as CBI must be submitted for inclusion in the
public docket and EPA’s electronic public docket.  If you submit the
copy that does not contain CBI on disk or CD-ROM, mark the outside of
the disk or CD-ROM clearly that it does not contain CBI.  Information
not marked as CBI will be included in the public docket and EPA’s
electronic public docket without prior notice.  If you have any
questions about CBI or the procedures for claiming CBI, please consult
the person identified in the FOR FURTHER INFORMATION CONTACT section.

Worldwide Web (WWW).  In addition to being available in the docket, an
electronic copy of today’s proposed rule will also be available on the
WWW through the Technology Transfer Network (TTN).  Following the
Administrator’s signature, a copy of the proposed rule will be placed
on the TTN’s policy and guidance page for newly proposed or
promulgated rules at http://www.epa.gov/ttn/oarpg.  The TTN provides
information and technology exchange in various areas of air pollution
control.  If more information regarding the TTN is needed, call the TTN
HELP line at (919) 541-5384.

Outline.  This preamble is organized as follows:

I.  Background and Criteria for Delisting

II.  Summary of Petitioner’s Request and EPA’s Initial Determination

III.  Description of the Four Stationary Combustion Turbine
Subcategories

IV.  Analysis of Gas-Fired Subcategories

A.  Analytical Approach

B.  Planning and Scoping

C.  Source Characterization

D.  Emissions Characterization

E.  Air Dispersion Modeling

F.  Human Health Effects of Emitted HAP

G.  Human Health Values Used 

H.  Human Health Risk Results-Inhalation Pathway

I.  Multipathway Considerations

J.  Effects Due to Acute Exposure

K.  Environmental Effects Evaluation

V.  Analysis of the Emergency Turbine Subcategory 

VI.  Analysis of the North Slope Turbine Subcategory

VII.  Conclusions

VIII.  Statutory and Executive Order Reviews

A.  Executive Order 12866: Regulatory Planning and Review

B.  Paperwork Reduction Act

C.  Regulatory Flexibility Act         

D.  Unfunded Mandates Reform Act 

E.  Executive Order 13132: Federalism

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

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

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

I.  National Technology Transfer and Advancement Act

I.  Background and Criteria for Delisting 

Section 112 of the CAA contains a mandate for EPA to evaluate and
control emissions of HAP from industry sectors called source categories.
 Section 112(b)(1) of the CAA includes a list of 188 specific chemical
compounds and classes of compounds identified as HAP.  Section 112(c) of
the CAA requires the EPA to publish a list of all categories and
subcategories of sources of HAP which will be subject to regulation. 
Each category or subcategory which includes major sources of HAP must be
listed for regulation.  Under section 112(d), the CAA requires EPA to
establish national emission standards for major source categories based
on MACT for each category or subcategory which is included in the list.	

The EPA published the initial Source Category List in the Federal
Register on July 16, 1992 (57 FR 31576); you can find the most recent
update to the Source Category List in the February 12, 2002 Federal
Register (67 FR 6521).

Section 112(c)(9) of the CAA provides for the deletion of a source
category from the list of source categories.  A source category may be
deleted from the list under section 112(c)(9)(A) of the CAA if the
category no longer satisfies the criteria for inclusion on the list
because of the deletion of one or more HAP from the HAP list pursuant to
section 112(b)(3)of the CAA, or a source category may be deleted from
the list under section 112(c)(9)(B) of the CAA if certain substantive
criteria are satisfied.  The EPA construes these provisions to apply to
each listed subcategory as well.  This construction is logical in the
context of the general regulatory scheme established by the statute, and
is the most reasonable one because section 112(c)(9)(B)(ii) of the CAA
expressly refers to subcategories.  If EPA takes final action to delete
a listed

source category or subcategory, this eliminates any requirement that a
MACT standard be promulgated for the category or subcategory in
question.  If a MACT standard has already been promulgated, EPA will
amend or rescind the standard in question.

A proceeding to delete a listed category or subcategory under section
112(c)(9)(B) of the CAA may be commenced either in response to a
petition or on the initiative of the EPA Administrator.  A source
category delist petition is a formal request to the EPA from an
individual or group to remove a specific source category or subcategory
from the source category list.  The Administrator must either grant or
deny a petition within 1 year after receiving a complete petition.  To
grant such a petition, or to commence a proceeding to delete a category
or subcategory on the Administrator’s own motion, the Administrator
must make an initial determination that: 

(1)  In the case of HAP emitted by sources in the category or
subcategory that may result in cancer in humans, a determination that no
source in the category or subcategory emits such HAP in quantities that
may cause a lifetime risk of cancer greater than one in one million to
the individual in the population who is most exposed to emissions of
such HAP from the source;

(2)  In the case of HAP that may result in adverse health effect in
humans other than cancer, a determination that emissions from no source
in the category or subcategory exceed a level which is adequate to
protect public health with an ample margin of safety; and 

(3)  In the case of HAP that may result in adverse environmental
effects, a determination that no adverse environmental effect will
result from emissions from any source in the category or subcategory.

If the Administrator decides to deny a petition, the Agency publishes a
written explanation of the basis for denial in the Federal Register.  A
decision to deny a petition is final Agency action subject to review. 
If the Administrator decides to grant a petition, the Agency publishes a
written explanation of the Administrator’s decision, along with a
proposed rule to delete the affected source category or subcategory. 
After affording an opportunity for notice and comment, the Administrator
will issue a final rule determining whether or not the affected category
or subcategory will be delisted.  If the final rule delists any affected
source category or subcategory, the Administrator will also take all
necessary actions to revise the source category list and to amend or to
rescind affected MACT standards.

We do not interpret section 112(c)(9)(B) of the CAA to require absolute
certainty that a source category or subcategory will not cause adverse
effects on human health or the environment before it may be deleted from
the source category list.  The use of the words “may” and
“adequate” indicate that the Agency must weigh the potential
uncertainties and their likely significance.  Uncertainties concerning
risks of adverse health or environmental effects may be mitigated if we
can determine that projected exposures are sufficiently low to provide
reasonable assurance that such adverse effects will not occur. 
Similarly, uncertainties concerning the magnitude of projected exposures
may be mitigated if we can determine that the levels which might cause
adverse health or environmental effects are sufficiently high to provide
reasonable assurance that exposures will not reach harmful levels.   

Summary of Petitioner’s Request and EPA’s Initial

Delisting Determination	

On August 28, 2002, the GTA submitted a petition requesting EPA to
create and then delete two subcategories of the stationary combustion
turbine source category: (1) lean premix stationary combustion turbines
firing natural gas as a primary fuel with limited oil backup capability,
and (2) a low risk subcategory of stationary combustion turbines.

Upon receiving a source category or subcategory deletion petition, EPA
must first determine whether there is a match between the source
category or subcategory to which the petition applies and a listed
category or subcategory.  When a MACT standard has been promulgated for
the category in question, EPA will consult the definitions in that
standard to determine whether or not a petition refers to a listed
category or subcategory.   

In this case, neither of the two subcategories to which the petition
refers existed at the time the petition was received, nor do they
coincide with the subcategories which we have recently adopted in the
final MACT standard for stationary combustion turbines.  However, based
on the information and the arguments presented in the petition, we
decided to conduct our own analysis on the subcategories as they were
defined in the final MACT standard to determine whether any of these
subcategories meet the criteria of section 112(c)(9)(B)of the CAA.  In
the analysis on which our initial determinations are based, we used the
data and analysis presented in the petition in those instances where we
felt it was relevant and technically appropriate to do so, and we
collected additional data and performed further analysis where those in
the petition were inadequate.

We construe our action in issuing the proposed rule to constitute a
partial grant and a partial denial of the GTA petition.  The lean premix
gas-fired turbines subcategory in the final MACT standard is similar to
one of the subcategories that the petitioner proposed:  namely, the lean
premix stationary combustion turbine firing natural gas as a primary
fuel with limited oil use.  We have made an initial determination that
the substantive criteria for delisting are satisfied for this
subcategory.  However, in the final MACT standard, we did not create any
subcategory coinciding with the low-risk subcategory proposed by the
petitioner.  Therefore, we must deny that portion of the petition. 
Also, we have made an initial determination that several additional
subcategories included in the final MACT standard satisfy the
substantive criteria for delisting.  These additional subcategories are:
 diffusion flame gas-fired turbines, emergency stationary combustion
turbines and stationary combustion turbines, and stationary combustion
turbines located on the North Slope of Alaska.

III.  Description of the Four Stationary Combustion Turbine
Subcategories

The final MACT standard (40 CFR 63.6175) defines stationary combustion
turbines as, “all equipment including, but not limited to, the
turbine, the fuel, air, lubrication and exhaust gas systems, control
systems (except emissions control equipment), and any ancillary
components and sub-components comprising any simple cycle stationary
combustion turbine, any regenerative/recuperative cycle stationary
combustion turbine, or the combustion turbine portion of any stationary
combined cycle steam/electric generating system.  Stationary means that
the combustion turbine is not self-propelled or intended to be propelled
while performing its function.  A stationary combustion turbine may,
however, be mounted on a vehicle for portability or transportability.”
 Currently, there are approximately 8,000 stationary combustion turbines
operating in the U.S.

For the purposes of the MACT standard, stationary combustion turbines
have been divided into eight subcategories.  Four of those subcategories
are the subject of this delisting proposal:  (1) stationary lean premix
combustion turbines when firing gas and when firing oil at sites where
all turbines fire oil no more than 1,000 hours annually (also referred
to as “lean premix gas-fired turbines”), (2) stationary diffusion
flame combustion turbines when firing gas and when firing oil at sites
where all turbines fire oil no more than 1,000 hours annually (also
referred to herein as “diffusion flame gas-fired turbines”), (3)
emergency stationary combustion turbines, and (4) stationary combustion
turbines operated on the North Slope of Alaska (defined as the area
north of the Arctic Circle (latitude 66.5( North)).

The stationary combustion turbine MACT standard also defines these
subcategories.  The lean premix gas-fired turbines subcategory includes
those stationary combustion turbines that use lean premix technology. 
This technology was introduced in the 1990s and was developed to reduce
nitrogen oxide (NOx) emissions without the use of add-on controls.  In a
lean premix combustor, the air and fuel are thoroughly mixed to form a
lean mixture for combustion.  Mixing may occur before or in the
combustion chamber.  Lean premix combustors emit lower levels of NOx,
carbon monoxide (CO), formaldehyde and other HAP than diffusion flame
combustion turbines.

Diffusion flame gas-fired turbines operate in a different manner than
lean premix units.  In a diffusion flame combustor, the fuel and air are
injected at the combustor and are mixed only by diffusion prior to
ignition.  	Emergency stationary combustion turbines are stationary
combustion turbines that operate in an emergency situation.  Examples
include stationary combustion turbines used to produce power for
critical networks or equipment (including power supplied to portions of
a facility) when electric power from the local utility is interrupted,
or stationary combustion turbines used to pump water in the case of fire
or flood, etc.  Emergency stationary combustion turbines do not include
stationary combustion turbines used as peaking units at electric
utilities or stationary combustion turbines at industrial facilities
that typically operate at low capacity factors.  Emergency stationary
combustion turbines may be operated for the purpose of maintenance
checks and readiness testing, provided that the tests are required by
the manufacturer, the vendor, or the insurance company associated with
the turbine.     

The subcategory stationary combustion turbines located on the North
Slope of Alaska refers to all stationary combustion turbines that are
located north of the Arctic Circle.  They have been identified as a
subcategory due to operating limitations and uncertainties regarding the
application of controls to these units.

IV.  Analysis of Gas-Fired Subcategories

A.  Analytical Approach

In conducting the risk assessment for these four source categories, EPA
uses a tiered, iterative process recommended by the National Research
Council (NRC) of the National Academy of Sciences (NRC 1994).  This
process begins with the use of relatively inexpensive screening
techniques and moves to more resource-intensive levels of
data-gathering, model construction, and model application, as the
particular situation warrants (NRC 1994).  In applying this approach,
EPA typically conducts the first (and in some cases the only) iteration
of the risk assessment using limited amounts of data and simple,
health-protective assumptions.  This results in risk estimates that we
expect will over-predict the actual risk.  If the initial estimates of
risk exceeds a level of concern, then successive refinements with regard
to data and models may be useful to more accurately characterize the
actual risk.  If the initial estimate is below a level of concern, then
a more sophisticated analysis may not be necessary for decision-making
purposes.  

The analysis discussed here represents an initial assessment based on
simple, conservative assumptions.  This screening approach has not
sought to modify the assumptions in a way that would yield high-end
estimates (e.g., 95th percentile) within the distribution of expected
exposures.  Instead, through the compounding of conservative
assumptions, we feel this approach yields exposure estimates that
exceeds exposures to the most exposed individuals in the population.

B. Planning and Scoping

The first step in conducting a tiered, iterative risk assessment is to
plan and scope the assessment.  The EPA provides guidance for this step
in the Risk Characterization Handbook (EPA 2000) and in the Framework
for Cumulative Risk Assessment (EPA 2003).  The general process of
planning and scoping includes defining the elements that will or will
not be included in the risk assessment, and explaining the purposes for
which the risk assessment information will be used (EPA 2000).

In order to plan and scope this assessment we asked ourselves several
questions including:  What is the motivation for conducting this risk
assessment?  What questions does the assessment need to address?  What
will be the design of the risk assessment (the data and methods to be
used, the elements to be included and excluded from the assessment)? 
How will the design of the assessment appropriately address the
questions posed, and therefore support a decision which satisfies the
statutory criteria?

We have already established the motivation for conducting this risk
assessment.  Prompted by industry, we conducted this assessment under
section 112(c)(9)(B) of the CAA to determine whether regulatory relief
for this industry was warranted.

Section 112(c)(9)(B) of the CAA provides the questions that this
assessment needed to address.  The assessment needed to show whether or
not any source in each of the four subcategories exceeds the human
health and ecological criteria described in the statute.

In designing assessment, we considered several factors: the statutory
requirements, the amount and type of available information on the
subcategories to include in the assessment, and the available methods
and models.  In this case, the statutory criteria are to show that no
source in each of the four subcategories exceeds the human health and
environmental criteria in section 112(c)(9)(B).  Based on these
criteria, we designed an assessment to estimate cancer risks and
noncancer hazards from a worst-case exposure scenario.  This exposure
scenario likely exceeds the exposure to the person most exposed.  We
began by conducting a human health risk analysis on the two gas-fired
turbine subcategories:  stationary lean premix combustion turbines when
firing gas and when firing oil at sites where all turbines fire oil no
more than 1,000 hours annually, and stationary diffusion flame
combustion turbines when firing gas and when firing oil at sites where
all turbines fire oil no more than 1,000 hours annually.  To evaluate
the risks, hazards and potential for adverse environmental effects from
the emergency turbine and north slope turbine subcategories, we used
available information on these subcategories and the results of the
assessment on the lean premix and diffusion flame subcategories. 

 We designed the assessment to address cancer risks and noncancer
hazards to humans from the air and ingestion pathways, and also
evaluated the potential for adverse environmental effects.  As we
describe above, we used a tiered, iterative approach to the assessment. 
Given that there are thousands of facilities in these four
subcategories, and that current information on these facilities is
limited, it was not feasible to identify all turbines and their
operating characteristics on a site-specific basis.  Therefore, we used
several health-protective assumptions where we lacked data.  This is an
appropriate approach to evaluating whether to remove a source category
or subcategory from regulation as the CAA specifies that in order to be
delisted, “no source in the category” may exceed the cancer,
noncancer or environmental criteria.  

We created a worst-case exposure scenario by using a combination of
actual data and health-protective assumptions.  For the air pathway, our
approach was to:

(1) Determine which type of turbine would result in the highest modeled
air concentration of HAPs.

(2) Hypothetically “place” eleven of these turbines at an actual
facility, to create our model plant. (An actual facility is permitted
for eleven turbines, but seven turbines are currently operated there.)

(3) Calculate cancer risks, noncancer hazards and the potential for
adverse environmental effects based on the highest ambient air
concentrations of HAPs calculated by the model.

For the multipathway analysis, we ‘placed’ the model plant in 8
locations around the country : Allentown, PA; Baton Rouge LA;
Indianapolis, IN;  Kansas City, KS; Los Angeles, CA; Minneapolis, MN;
Seattle, WA; and Tampa, FL. We developed and evaluated a farmer scenario
for our model plant as if plant was located in these cities. Our goal
here was to account for the effect of meteorologic variability on the
risks and hazards.

We feel the health-protective assumptions we used, which when
compounded in the assessment, lead to very health-protective risk
estimates.  Given the combination of data and assumptions used, we have
conducted an assessment consisting of a single iteration, that
adequately addresses the questions posed, that is responsive to the
requirements in section 112(c)(9)(B), that overestimates actual risks,
and shows that the statutory criteria for deletion are met. Note we will
have this analysis peer-reviewed in between proposal and promulgation to
ensure we have used the best science and methods.  See the technical
memo located in the docket for the a more detailed description of the
analysis.

C.  Source Characterization		

Stationary combustion turbines can be operated in two basic cycles: 
simple cycle and combined cycle.  The simple cycle mode consists of the
combustion turbine-generator combination operating and producing
electricity, with the turbine exhaust vented through a stack directly to
the atmosphere.  In the combined cycle mode, the exhaust from the
turbine is passed through a heat recovery steam generator to generate
steam that is then used to produce additional electricity.  The heat
extraction at this step cools the exhaust gas stream resulting in a
lower exhaust temperature (reduced plume buoyancy).  Thus, emissions
from a turbine operating in the combined cycle mode will often produce
higher ground level pollutant concentrations.  As a conservative
assumption, our analysis only examined the combined cycle units.

 	To conduct our analysis, we used information on the physical
characteristics of these turbines that was submitted by the petitioner
after we determined the data were of sufficient quality to do so.  The
GTA provided data on a set of typical turbines ranging in power output
from five to 253 megawatts (MW) each.  These characteristics include
turbine type (i.e. make and model), heat input, stack parameters
(height, diameter, exit velocity, temperature), and building dimensions.
 	

D.  Emissions Characterization

With regard to emissions, we agree with the petitioner that the
following HAP are emitted from turbines when natural gas is used as the
fuel:  1,3-butadiene, acetaldehyde, acrolein, benzene, ethylbenzene,
formaldehyde, naphthalene, polycyclic aromatic hydrocarbons (PAH, which
the EPA classifies as a subset of a larger group of HAP, polycyclic
organic matter, or POM), propylene oxide, toluene, and xylenes (mixed). 
We also agree with the petitioner that the following non-metallic HAP
are emitted from turbines when distillate oil is used as the fuel: 
1,3-butadiene, benzene, formaldehyde, naphthalene, and PAH.  However,
the petitioner claimed that metallic HAP are not detectable in
distillate oil and are thus not present in turbine emissions; they
subsequently amended this claim to state that only chromium and lead are
emitted.  We disagree with these claims and have collected additional
data showing the following HAP metals can be emitted when turbines burn
distillate oil although the levels can vary by oil type: arsenic,
beryllium, cadmium, chromium VI, lead, manganese, mercury, nickel and
selenium.  We used emission factors for the emitted HAP that are based
on the most recent available data.  Also, we developed separate emission
factors for large and small turbines based on the burner design-type
(lean premix or diffusion flame) and based on the differences in heat
input between small versus large turbines.  To develop a conservative,
yet still realistic emission values, we calculated emission factors by
selecting the upper 95 percent confidence interval around the mean of
each dataset.  We then developed turbine-specific emissions by
multiplying the pollutant-specific emission factors with the heat input
of each unit. 

E.  Air Dispersion Modeling

The goal of our air dispersion modeling approach was to determine the
maximum annual ambient average concentration for all emitted HAP that a
person living in the vicinity of a turbine would experience.  We used
these maximum annual ambient average concentrations, without regard to
whether a person actually lives at that location, as surrogates for
exposure.  This is a health protective, or conservative, approach to
assessing exposure.  

We used the SCREEN3 model (Version 96043) to estimate the maximum annual
ambient average concentration from all emitted pollutants.  SCREEN3
consists of algorithms that tend to overestimate HAP concentrations in
air along with worst-case meteorologic conditions to estimate ambient
concentrations of HAP in air.  This results in estimates of HAP
concentrations in air that are likely to be an overestimate of what we
expect people to actually breathe.  We used this health-protective
modeling approach to evaluate the four subcategories of stationary
combustion turbines because it is not feasible to identify all turbines
and their operating characteristics due to the large number of
facilities. Also, we want to ensure that our assessment is not
underestimating potential exposures and risks.  This is an important
consideration when we are evaluating whether to grant a petition to
remove a source category from regulation as the CAA specifies that in
order to be delisted, “no source in the category” may exceed the
cancer, noncancer or environmental criteria.

Our approach to modeling was to first determine which type of turbine
(of the ten turbine types identified by the petitioner) produces the
highest maximum annual ambient average concentrations using SCREEN3.  We
then built a simulated facility and ran SCREEN3 for all HAP emitted from
lean premix gas-fired turbines and also for diffusion flame gas-fired
turbines.

In applying SCREEN3 to determine which turbine type results in the
highest maximum annual ambient average concentrations, we ran SCREEN3
using regulatory default mode; full meteorology; building downwash; flat
nearby terrain; rural dispersion; automated receptor arrangement
(50-2000 meter); and a conversion factor of 0.08 to obtain annual
average concentrations from maximum 1 hour concentrations.  As stated
above, we used turbine characteristics submitted by the petitioner and
developed updated emission factors ourselves.  We used these data as
inputs into the SCREEN3 model in order to obtain the maximum annual
average air concentrations from a worst-case type of turbine.  Our
dispersion modeling showed that the W501F turbine resulted in the
highest air concentrations.

After establishing that maximum annual ambient average concentration
are the highest from the W501F turbine, we built a simulated facility. 
We placed 11 W501Fs at our simulated facility, because the highest
number of large turbines permitted to operated at an actual facility is
11.  After accounting for source separation (see technical memo for
details), we ran SCREEN3 on our simulated facility for four scenarios:
(1) assuming the 11 turbines are lean premix gas-fired turbines
collectively using 1,000 hours of oil per year; (2) assuming the 11
turbines are diffusion flame gas-fired turbines collectively using 1,000
hours of oil per year; (3) assuming the 11 turbines are lean premix and
burn only natural gas; and (4)assuming the 11 turbines are diffusion
flame turbines and burn only natural gas.  We conducted the analyses
assuming the turbines burn only natural gas in addition to natural gas
plus 1,000 hours of oil per year because not all facilities use oil, and
because emissions are different when only natural gas is used as fuel
(no metals are emitted but formaldehyde emissions are higher).  The
maximum annual ambient average concentrations for each emitted pollutant
for natural gas plus 1,000 hours/yr of oil and for natural gas only for
the 11 W501F turbines can be found in Table 4 of the technical memo. 

We consider the maximum annual average concentrations resulting from
our dispersion modeling analysis to be conservative.  That is, we feel
that the resulting air concentrations over- rather than under-estimate
actual exposures to people.  This is because our analysis used 
conservative source parameters and atmospheric dispersion modeling
methodology; relied on conservative emission factors for all HAP; used
the maximum annual ambient average concentrations of the emitted HAP as
a surrogate for exposure; and assumed 70 years of exposure, 24 hours a
day, 365 days a year of continuous exposure.  Even though actual
emission rates, and thus ambient concentrations, of HAP may increase
above annual average levels during certain short-duration transient
operations such as unit startup, we feel that the conservative analysis
approach accounts for such transient increases in the conservative
estimates of annual average exposures.  Thus, the analyses, even though
they do not explicitly incorporate these short term events, reasonably
account for these events and result in health-protective estimates of
risk.

F.  Human Health Effects of Emitted HAP

Although numerous HAP may be emitted from combustion turbines, a few
account for essentially all the mass of HAP emissions from stationary
combustion turbines.  These HAP are formaldehyde, toluene, benzene, and
acetaldehyde.  Other emitted HAP are of potential concern not so much
because of the emitted amounts, but due to their high potency via the
inhalation route.  These include arsenic and PAH.  Four of the emitted
HAP are of potential concern from the ingestion route:  PAH, which are
of concern for cancer, and cadmium, lead and mercury which are of
concern for noncarcinogenic effects.  Below are descriptions of the
adverse health effects associated with these pollutants.

The HAP emitted in the largest quantity is formaldehyde.  Formaldehyde
is a probable human carcinogen and can cause irritation of the eyes and
respiratory tract, coughing, dry throat, tightening of the chest,
headache, and heart palpitations.  Acute (short-term) inhalation has
caused bronchitis, pulmonary edema, pneumonitis, pneumonia, and death
due to respiratory failure.  Chronic (long-term) exposure can cause
dermatitis and sensitization of the skin and respiratory tract.  

Other HAP emitted in significant quantities from stationary combustion
turbines include toluene, benzene, and acetaldehyde.  The health effect
of primary concern for toluene is dysfunction of the central nervous
system (CNS).  Toluene vapor also causes narcosis.  Controlled exposure
of human subjects produced mild fatigue, weakness, confusion,
lacrimation, and paresthesia; at higher exposure levels there were also
euphoria, headache, dizziness, dilated pupils, and nausea. 
After-effects included nervousness, muscular fatigue, and insomnia
persisting for several days.  Acute exposure may cause irritation of the
eyes, respiratory tract, and skin.  It may also cause fatigue, weakness,
confusion, headache, and drowsiness.  Very high concentrations may cause
unconsciousness and death.

Benzene is a known human carcinogen.  The health effects of benzene
include nerve inflammation, CNS depression, and cardiac sensitization. 
Acute exposure can cause dizziness, euphoria, giddiness, headache,
nausea, staggering gait, weakness, drowsiness, respiratory irritation,
pulmonary edema, pneumonia, gastrointestinal irritation, convulsions,
and paralysis.  Benzene can also cause irritation to the skin, eyes, and
mucous membranes. Chronic exposure to benzene can cause fatigue,
nervousness, irritability, blurred vision, and labored breathing and has
produced anorexia and irreversible injury to the blood-forming organs;
effects include aplastic anemia and leukemia.  

Acetaldehyde is a probable human carcinogen.  Inhalation exposures to
acetaldehyde can cause irritation of the eyes, mucous membranes, skin,
and upper respiratory tract, and CNS depression in humans.  Acute
exposure can cause conjunctivitis, coughing, difficult breathing, and
dermatitis.  Chronic exposure may cause heart and kidney damage,
embryotoxicity, and teratogenic effects. 

Arsenic, a naturally occurring element, is found throughout the
environment.  For most people, food is the major source of exposure to
arsenic.  The EPA has classified inorganic arsenic as a human
carcinogen.  Acute high-level inhalation exposure to arsenic dust or
fumes has resulted in gastrointestinal effects (nausea, diarrhea,
abdominal pain); central and peripheral nervous system disorders have
occurred in workers acutely exposed to inorganic arsenic.  Chronic
inhalation exposure to inorganic arsenic in humans is associated with
irritation of the skin and mucous membranes.  Chronic oral exposure has
resulted in gastrointestinal effects, anemia, peripheral neuropathy,
skin lesions, hyperpigmentation, and liver or kidney damage in humans. 
Inorganic arsenic exposure in humans, by the inhalation route, has been
shown to be strongly associated with lung cancer, while ingestion of
inorganic arsenic in humans has been linked to a form of skin cancer and
also to bladder, liver, and lung cancer.

Polycyclic aromatic hydrocarbons are a group of compounds that fit
within the POM HAP category.  Dermal exposures to mixtures of PAH cause
skin disorders in humans and animals.  No information is available on
the reproductive or developmental effects of PAH mixtures in humans, but
animal studies have reported that oral exposure to benzo(a)pyrene
(BaP)(a PAH compound) causes reproductive and developmental effects. 
Human studies have reported an increase in lung cancer in humans exposed
to PAH-bearing mixtures including coke oven emissions, roofing tar
emissions, and cigarette smoke.  Animal studies have reported
respiratory tract tumors from inhalation exposure to BaP and forestomach
tumors, leukemia, and lung tumors from oral exposure to BaP.  The EPA
has classified seven PAH compounds:  (BaP, benz(a)anthracene, chrysene,
benzo(b)fluoranthene, benzo(k)fluoranthene, dibenz(a,h)anthracene, and
indeno(1,2,3-cd)pyrene) as Group B2, probable human carcinogens.

The EPA reports in IRIS that via the oral route cadmium has been shown
to cause kidney damage, however, there are no positive cancer studies of
orally ingested cadmium suitable for quantification.  Consequently, we
evaluated ingestion hazards only for cadmium.  The major effect from
chronic oral exposure to inorganic mercury is also kidney damage. 
Animal studies have reported effects such as alterations in testicular
tissue, increased resorption rates, and abnormalities of development
from oral exposure to inorganic mercury.  Mercuric chloride (an
inorganic mercury compound) exposure has been shown to result in
forestomach, thyroid, and renal tumors in experimental animals.  For
lead, oral exposures can lead to central nervous system effects, as well
as effects on the blood, blood pressure kidneys and Vitamin D
metabolism.  Children are especially sensitive to the chronic effects of
lead, and can exhibit slowed cognitive development and reduced growth.

G.  Human Health Values Used

We used the human health values currently used by EPA’s air toxics
program and available at:
http://www.epa.gov/ttn/atw/toxsource/summary.html.  These dose response
values come from several sources including EPA’s IRIS, the Centers for
Disease Control’s Agency for Toxic Substances Disease Registry, and
California EPA.  See Table 5 in our technical memo for a summary of the
human health values we used in our assessment.	

For formaldehyde, we use a different dose-response value from the one
reported in IRIS.  The dose-response value in IRIS is based on a 1987
study.  Since that time, significant new data and analysis have become
available.  We based the dose-response value we used for formaldehyde on
work conducted by the CIIT Centers for Health Research (CIIT) (formerly,
the Chemical Industry Institute of Toxicology).  In 1999, the CIIT
published a risk assessment which incorporated mechanistic and
dosimetric information on formaldehyde that had been accumulated over
the past decade (see the docket for the CIIT report).  The risk
assessment analyzed carcinogenic risk from inhaled formaldehyde using
approaches that are consistent with EPA’s draft guidelines for
carcinogenic risk assessment.  The CIIT model is based on computational
fluid dynamics (CFD) models of airflow and formaldehyde delivery to the
relevant parts of the rat and human respiratory tract, which are then
coupled to a biologically-motivated two-staged clonal growth model that
allows for incorporation of different biological effects.  These
biological effects, such as interaction with DNA and cell proliferation,
are processes by which formaldehyde may contribute to development of
cancer at sites exposed at the portal of entry (e.g., respiratory
tract).  The two-staged model is a much more advanced approach for
examining the relevance of tumors seen in animal models for human
populations.  	 

We feel that the CIIT modeling effort represents the best available
application of the available mechanistic and dosimetric science on the
dose-response for portal of entry cancers due to formaldehyde exposures.
 We note here that other organizations, including Health Canada, have
adopted this approach.  Accordingly, we have used risk estimates based
on the CIIT airflow model coupled to a two-staged clonal growth model as
the basis for the dose-response values for this analysis.  The
formaldehyde risk value obtained by extrapolating with the CIIT model
that we used in our analysis differs slightly from the values used by
the petitioner.  This model incorporates state-of-the-art analyses for
species-specific dosimetry, and encompasses more of the available
biological data than any other currently available model.  As with any
model, uncertainties exist, and this model is sensitive to the inputs. 

The Agency is aware of recently completed epidemiologic analyses that
update existing cohorts of workers exposed to formaldehyde.  Not all of
these results have been published in peer reviewed journals at this
point.   These studies examine the potential for formaldehyde to cause
cancer in other organs.  These new results in combination with the
previously available literature regarding the potential for systemic
effects indicates the pollutant may be taken into the body and
distributed to extra respiratory organs, potentially causing adverse
effects that are not picked up by the CIIT model.  As these new studies
are published in peer reviewed journals and data sets are made available
for further analysis, we will evaluate them in the context of the full
body of literature to determine the relevance to our conclusions with
regard to risks from the gas-fired combustion turbines subcategories.  

The proposed rule relies on the CIIT CFD airflow model coupled with a
two-stage clonal growth model as the basis for the human health value we
used in our analysis.  Not all of the newer epidemiologic studies have
been published in the peer reviewed literature yet, and the new data are
not yet fully available.  The strengths of the analyses provided in the
CIIT study on effects at the portal of entry, make it the most
appropriate and biologically defensible choice for the proposed rule. 
The EPA plans to continue to evaluate additional information that
becomes available on formaldehyde.  In the future, EPA may or may not
determine that this other information is relevant to our analysis of
emissions from stationary combustion turbines. 	

H. Human Health Risk Results-Inhalation Pathway

We calculated the maximum excess lifetime cancer risk for the
inhalation pathway that results from the reasonable worst-case exposure
scenario described above.  We estimated risks for both the primary
firing of natural gas with 1,000 hours of oil firing per year, per
facility, and for the continuous firing of natural gas.  Diffusion flame
gas-fired turbines produced the highest risk.  When firing natural gas
plus 1,000 hours of oil per year, the total excess lifetime cancer risk
from the all emitted pollutants from the diffusion flame turbines in our
analysis is 7.7 x 10-7.  The total excess lifetime cancer risk from the
continuos burning of natural gas for our modeled scenario is 3.9 x 10-7.


In addition to estimating cancer risks, we evaluated noncancer hazards
for each pollutant where there is a noncancer human health value.  To do
this, we used a hazard quotient(HQ) approach and calculated the ratio of
the exposure concentration to the noncancer human health value (e.g.,
RfC) for each emitted HAP.  This is represented by the formula HQ=
(exposure concentration)/(RfC).  The RfC is a peer-reviewed value
defined as an estimate (with uncertainty spanning perhaps an order of
magnitude) of a daily inhalation exposure to the human population
(including sensitive subgroups) that is likely to be without appreciable
risk of deleterious noncancer effects during a life-time.

 We then generated hazard indices (HI) by summing HQ across HAP.  We
can generate two types of hazard indices. The first type is generated by
adding HQ for all emitted HAP regardless of their target organ.  This
results in an HI that is considered health-protective since the HQ for
all pollutants are added even though some pollutants cause distinctly
different effects.  For our modeled scenario, the total HI for all
noncarcinogens for the natural gas plus 1,000 hours of oil scenario is
0.6.  The HI for the natural gas burning scenario is 0.4.

We can also calculate HI by summing HQ from HAP that affect the same
target organ.  In this assessment, pollutants that affect the same
target organ are acrolein and formaldehyde; they affect the respiratory
system.  These also are the two HAP with the highest individual hazard
quotients.  When accounting for the fact that acrolein and formaldehyde
affect the same target organ, we calculate a HI of 0.4.  None of the
other HAP affect the same target organ, thus, we calculated a HI for the
respiratory system only.   The other HAP had HQ ranging from 10-6
(nickel) to 0.1 (manganese). 

I.  Multipathway Considerations

In order to fully characterize risks and hazards to humans from these
subcategories, we considered exposures from ingestion as well as
inhalation for four of the emitted HAP:  cadmium, lead, mercury and PAH.
 We chose these HAP because of all the HAP emitted, only these four
appear on lists of chemicals that EPA considers to be persistent,
bioaccumulative, and toxic (PBT) substances under the Pollution
Prevention program, the Great Waters program, or the Toxics Release
Inventory. (See the multipathway HAP memo in the docket for more
information.)  Therefore, in addressing the potential for these
subcategories to be of concern due to multipathway routes of exposure,
we need to consider emissions of cadmium, lead, mercury and PAH.

Several of the emitted PAH are carcinogenic via the ingestion pathway
and thus we evaluated these pollutants in the multipathway analysis:
benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene,
benzo(k)fluoranthene, chrysene, dibenz(a,h)anthracene, and
indeno(1,2,3-cd)pyrene.  We evaluated noncarcinogenic effects for
cadmium, lead, mercury and the following noncarcinogenic PAH:
acenaphthene, fluoranthene, fluorene,and pyrene. 	

To evaluate the potential for these HAP to cause cancer risk or
noncancer hazard to humans due to ingestion, we conducted a screening
level multipathway analysis.  As with the inhalation assessment, we did
not have enough data to  evaluate actual exposures across the entire
source category. We did not structure this assessment to reflect actual
exposures, rather we developed a worst-case exposure model scenario
based on limited data and assumptions which, when  considered in total,
provide for a health-protective analysis.  We feel this approach ensures
that we are not underestimating actual risks and hazards from emissions
from these four subcategories.  

We structured this analysis to estimate maximum risks to an individual
exposed via routes other than inhalation (e.g. ingestion of contaminated
food) to HAP emitted from combustion turbines.  We used our modeled
facility, and evaluated human ingestion of contaminated food, water and
soil.  The Human Health Risk Assessment Protocol for Hazardous Waste
Combustion Facilities (HHRAP) (U.S. EPA, 1998) provided the primary
source of chemical-specific parameter values and default environmental
parameters. We started with the HHRAP, and replaced specific inputs as
necessary, either due to updated science, or due to policy choices that
we made in order to be consistent with the mandate to  assess risks to
the individual most exposed.

To evaluate a worst-case potential exposure from our modeled facility,
we used a subsistence farmer scenario. This scenario reflects an adult
living on a farm that we hypothetically assumed to be located close to
our modeled facility.  We assumed the farmer consumes meat (pork and
beef), dairy, fruit, and vegetables that the farm produces.  The animals
raised on the farm subsist primarily on feed grown on the farm.  We also
assumed that the farmer is a recreational fisher and eats the fish
he/she catches.  Finally, we assumed that the farmer drinks treated,
local surface water (water which has gone through minimal municipal
treatment).  We assumed that the farmer eats these home-produced foods
at the rate equal to the mean intake for 20 to 39 year olds, as reported
in the EPA’s Exposure Factors Handbook (EPA-600/P-95/002).  

For several reasons, we consider this approach to multipathway
assessment scenario to be health-protective.  We used the ambient air
concentrations from our modeled facility which, as we have stated above,
produces higher ambient air concentrations than we expect to actually
occur anywhere in the U.S.  Also, we ran the IEM-2M model the using a
water body size, flow rate, watershed size and other parameters based on
a health protective analysis scenario analyzed in the Mercury Study
Report to Congress.  Further, we applied maximum pollutant deposition
rates to the entire watershed.  Thus, we feel our modeled scenario will
over-predict actual risks and hazards from ingestion and is, therefore,
health-protective.

We estimated both cancer risk and noncancer hazards from all the
ingestion pathways:  water, meats, fruits, vegetables, soil, and fish. 
The results of our multipathway analysis show that the cancer risks from
PAH are 0.16 in one million (1.6 x 10-7).  This is below the statutory
cancer risk criterion of one in one million.  When we add these risks to
the lifetime excess cancer risks of 7.7 x 10-7 from the inhalation
pathway, we get a total cancer risk of .93 in one million, which rounds
to .9 in one million (9 x 10-6). Such a summation of risks is
appropriate only if it is plausible that the person with the maximum
risks from the air pathway is also the person with the maximum risk from
the ingestion pathway.  Inherent in this assumption is that these two
maximum concentrations (therefore, the maximum risk and hazards) occur
at the exact same location.  While we calculated risk and hazards for
such a person, we feel it very unlikely that one person would be located
at the point of highest impact from both inhalation and ingestion.  If
we had more site-specific data with which to conduct this assessment, we
would likely have found that the maximum impact from inhalation was not
in the same location as the maximum impact from ingestion, and the risks
would be lower.  We feel it is inappropriate to consider this combined
inhalation/ingestion scenario because we consider it to be implausible. 
We feel that the actual combined risks, from all pathways, will be lower
than one in a million and, therefore, the statutory criteria is met.  

We estimated noncancer hazards for cadmium and mercury, combining
hazards from all ingestion pathways.  The highest total hazard index for
all ingestion pathways is 0.1. Noncancer hazards are driven by methyl
mercury via ingestion of fish. The HQ for mercury for this route of
exposure is also 0.1; it is clearly the driver for multipathway
noncancer effects.  

The EPA uses a slightly different approach in order to assess the
hazard from ingestion exposures to lead.  In general, we use a model
like the IEM-2M to obtain media concentrations.  We use an additional
model called the Integrated Exposure, Uptake and Biokinetic Model
(IEUBK) to estimate blood lead levels.  We then calculate an HQ.  In
this analysis, the inhalation HQ for lead was so low, 0.000008, that we
found it unnecessary to take the additional step of modeling further
with the IEUBK.  Based on previous analyses we have conducted on lead,
we do not feel that an air concentration that leads to an HQ of 0.000008
would translate into an HQ of concern from the ingestion route of
exposure.  The ingestion HQ would have to be four to five orders of
magnitude higher than the HQ from the air pathway to even approach a
level of concern.  Given the very low inhalation HQ for lead from
exposure to these turbines, we feel that lead emissions from these four
subcategories do not exceed a level that is adequate to protect the
public health with an ample margin of safety.  Therefore, we conclude
that both risks and hazards to humans due to multipathway exposures from
all HAP emitted from the four combustion turbine subcategories meet the
required human health criteria in CAA section 112(c)(9)(B). 

Emissions that result in the maximum modeled lifetime excess cancer risk
of 0.9 in one million, are within the statutory criteria.  With regard
to noncancer effects, we consider the emission resulting in a target
organ-specific HI of 0.4 from the turbine subcategory do not exceed a
level that is adequate to protect the public health with an ample margin
of safety.  We consider the actual risks and hazards from the turbines
in these four subcategories to be lower than what we estimated here, due
to the health-protective assumptions we included in this assessment. 
For example, in characterizing the physical and operational attributes
of the turbines, we assumed all turbines were operating in combined
cycle, used conservative temperature and exit velocities, used
worst-case meteorology, and included the potential for building
downwash.  These assumptions lead to exposures which we feel are higher
than what we would find from an actual plant.  In addition, we assumed
that individuals are exposed to  the maximum modeled concentrations of
HAP in the air continuously for their entire lives (which we
approximated as 70 years), and we used the maximum annual average
concentration as a surrogate for exposure.  These assumptions are also
health-protective.

J.  Effects due to Acute Exposure

We determined that emissions from turbines are of concern for long-term
(chronic) exposures and not from short term (acute) exposures.  Short
term exposures may arise when a facility starts up or shuts down
equipment.  This activity may result in short bursts of high emissions,
due to the fact that the unit is not running at peak efficiency during
the time it takes to start up or shut down.  In some cases, this can
lead to exposures that result in adverse health effects.  In the case of
gas-fired turbines, we have determined that upon start up, they reach
peak efficiency quickly, therefore, limiting any bursts of emissions. 
Shut downs take a short amount of time as well.  The adverse health
effects associated with exposure to the emitted HAP from combustion
turbines have not been associated with acute exposures at the
concentrations of concern in these analyses.  While these short-duration
emissions may slightly increase the overall cancer risks, this effect
would be so small as to be inconsequential.  Therefore, we conclude that
the acute exposures to HAP emissions from stationary combustion turbines
are not of concern.

K.  Environmental Effects Evaluation 

In order to assess whether the emissions from our modeled facility
could lead to adverse environmental effects, we performed a
screening-level ecological risk assessment.  We evaluated the inhalation
pathway for terrestrial mammals, the ingestion pathway for terrestrial
wildlife, contact with sediment to benthic species and contact with soil
for terrestrial plants.  We did not evaluate terrestrial plants exposed
via direct contact with the air due to a lack of toxicity data. 

 In order to assess whether the continuing emissions from our modeled
facility could contribute to adverse environmental effects from the
ingestion pathway, we performed a screening-level ecological risk
assessment.  For screening purposes, we intentionally designed this
assessment to be health-protective of ecological receptors.  We did not
intend the assessment to be used in predicting specific types of effects
to individuals, species, populations, or communities or to the structure
and function of the ecosystem.  We used the assessment to identify HAP
which may pose potential risk or hazard to ecological receptors and,
therefore, would need to be evaluated in a more refined level of risk
assessment.

For screening endpoints, we used the structure and function of generic
aquatic and terrestrial populations and communities, including
threatened and endangered species, that might be exposed to HAP
emissions via soil or water, from our modeled facility.  The assessment
endpoints are relatively generic with respect to descriptions of the
environmental values that are to be protected and the characteristics of
the ecological entities and their attributes.  We assumed in the
assessment that these ecological receptors were representative of
sensitive individuals, populations, and communities present near these
facilities. 

For the ecological assessment, we included the same HAP that we
evaluated in the multipathway human health assessment:  cadmium, lead,
mercury and PAH.  We derived estimated media concentrations for each of
these HAP from the media concentrations estimated in the multipathway
exposures assessment.  We chose exposure pathways to reflect the
potential routes of exposure through sediment, soil, water, and air.  We
selected these environments because they are considered representative
of locations of generic populations and communities most likely to be
exposed to the HAP.  Within these environments the receptors evaluated
consisted of two distinct groups:  terrestrial and aquatic (i.e.,
including aquatic, benthic, and soil organisms; terrestrial plants and
wildlife; and herbivorous, piscivorus, and carnivorous wildlife).

The chronic ecological toxicity screening values used in the assessment
were estimates of the maximum concentrations that would not be expected
to affect survival, growth, or reproduction of sensitive species after
long-term (more than 30 days) exposure to HAP.  We screened HAP,
pathways, and receptors using the ecological HQ method, which simply
calculates the ratio of the estimated environmental concentrations to
the selected ecological screening values.  

The results of our ecological assessment show that for all pollutants
assessed, and for all pathways assessed, the ecological HQ values are
less than 1.  Therefore, it is not likely that any of the HAP emitted
would pose an ecological risk to ecosystems near any of these
facilities. 

 With regard to endangered species, we assumed that the screening
values were protective of sensitive species, including threatened or
endangered species.  There are no available ecological toxicity test
data for threatened and endangered species for these HAP.  As such, the
actual sensitivities of any threatened or endangered species located in
the vicinity of these facilities is unknown.  However, in order to be
conservative, we selected ecological screening values for the most
sensitive species available for use in this analysis.  Also, we are not
familiar with any species that have become threatened or endangered as a
result of emissions of these chemicals from stationary combustion
turbines.  Therefore, we feel it is not likely that any threatened and
endangered species, if they exist around these facilities, would be
adversely affected by these HAP emissions.

V.  Analysis of the Emergency Turbine Subcategory

In addition to assessing whether the gas-fired subcategories meet the
statutory delisting criteria, we also evaluated whether the emergency
stationary combustion turbine subcategory meets the criteria.	

Emergency stationary combustion turbines are stationary combustion
turbines that operate in an emergency situation.  Examples include
stationary combustion turbines used to produce power for critical
networks or equipment (including power supplied to portions of a
facility) when electric power from the local utility is interrupted, or
stationary combustion turbines used to pump water in the case of fire or
flood, etc.  Emergency stationary combustion turbines do not include
stationary combustion turbines used as peaking units at electric
utilities or stationary combustion turbines at industrial facilities
that typically operate at low capacity factors.  Emergency stationary
combustion turbines may be operated for the purpose of maintenance
checks and readiness testing, provided that the tests are required by
the manufacturer, the vendor, or the insurance company associated with
the turbine. 

Usually one or two emergency turbines are located at a given facility. 
These units run mostly on oil, and operate approximately 30 hours/yr,
per turbine.  Regular testing of these units (done to ensure they will
be operational during an emergency) may bring the total operating hours
for a turbine up towards 200 hours/yr, per turbine, or approximately 400
hours per facility.  Given that these units burn less oil than allowed
under the MACT for lean premix and diffusion flame gas-fired turbines
(1,000 hours per facility), we expect the maximum annual average HAP
concentrations in air to be much less for emergency turbines. 
Therefore, we expect the risks and hazards to be less.	

VI.  Analysis of the North Slope Turbine Subcategory 	

The subcategory stationary combustion turbines located on the North
Slope of Alaska refers to all stationary combustion turbines that are
located north of the Arctic Circle.

We have identified 120 stationary combustion turbines that are located
on the North slope of Alaska.  Of these, 112 are diffusion flame
gas-fired units, and eight are lean premix gas-fired turbines.  The
total number of oil hours used, per year, by any facility we identified
on the North Slope is much less than 1,000 hours.  Because we have
determined that facilities burning oil for fewer than 1,000 hours/yr
meet the three statutory criteria for delisting, we concluded that
stationary combustion turbines located on the North Slope of Alaska also
meet the delisting criteria. 

VII.  Conclusions

The CAA requires that criteria for cancer, noncancer effects and
environmental effects be met in order for the EPA to remove a source or
subcategory from the source category list.  To commence a proceeding to
delete a category or subcategory on the Administrator’s own motion, 

the Administrator must make an initial determination that: 

(1) in the case of HAP emitted by sources in the category or subcategory
that may result in cancer in humans, a determination that no source in
the category or subcategory emits such HAP in quantities that may cause
a lifetime risk of cancer greater than one in one million to the
individual in the population who is most exposed to emissions of such
HAP from the source;

(2) in the case of HAP that may result in adverse health effect in
humans other than cancer, a determination that emissions from no source
in the category or subcategory exceed a level which is adequate to
protect public health with an ample margin of safety; and 

(3) in the case of HAP that may result in adverse environmental effects,
a determination that no adverse environmental effect will result from
emissions from any source in the category or subcategory.

We have made an initial determination that all these criteria have been
met for the four source categories we evaluated in the proposal: (1)
lean premix gas-fired turbines, (2) diffusion flame gas-fired turbines,
(3) emergency stationary combustion turbines, and (4) stationary
combustion turbines operated on the North Slope of Alaska.

With regard to cancer risk, the highest inhalation risk we calculated
was 0.77 in one million (7.7 x 10-7) for our modeled facility in which
we located 11 diffusion flame turbines.  Combining the inhalation cancer
risk with the cancer risk estimated from the multipathway assessment
gives us a total lifetime excess cancer risk of 0.9 in one million.  On
the noncancer side, the highest HI is a respiratory-system specific HI
of 0.4.  We consider the actual risks and hazards from the turbines in
these four subcategories to be lower than what we estimated here, due to
the health-protective assumptions we included in this assessment.  For
example, in characterizing the physical and operational attributes of
the turbines, we assumed all turbines were operating in combined cycle,
used conservative temperature and exit velocities, used worst-case
meteorology, and included the potential for building downwash.  These
assumptions lead to exposures which we feel are higher than what we
would find from an actual plant.

In addition, we assumed that individuals are exposed to  the maximum
modeled concentrations of HAP in the air, and we used the maximum annual
average concentration as a surrogate for exposure.  These assumptions
are also health-protective. 

With regard to human health values, we used values that are designed to
be health-protective.  For acetaldehyde, we used the health value
currently reported in IRIS.  We are updating the acetaldehyde IRIS file
and expect new data to show that acetaldehyde is actually less toxic
than we previously thought it to be.  For formaldehyde, while we feel
the CIIT assessment provides an adequate scientific basis from which to
analyze emissions, we will evaluate the new studies as soon as they are
available and will determine the relevance to our conclusions with
regard to risks from turbines.  For other carcinogens included in our
risk assessment, we used cancer unit risk estimates that are defined by
IRIS as “upper-bound excess lifetime cancer risk estimated to result
from continuous exposure to an agent at a concentration of ... 1 ug/m3
in the air.”  (The IRIS glossary defines upper-bound as “a plausible
upper limit to the value of a quantity.  This is usually not a true
statistical confidence limit.”)

Given the health-protective nature of our modeling scenario, and the
health-protective nature of our human health values for the emitted
pollutants, we feel that the actual maximum cancer risks faced by any
person living in the vicinity of turbines in these four subcategories is
lower than one in one million.  Therefore, we feel that the criterion
regarding cancer effects is clearly met.  

With regard to noncancer hazards, given the above factors and given the
understanding that there are generally no additional sources of HAP at
these turbine sites, we feel it is unlikely that a maximum target
organ-specific HI in the vicinity of a turbine site would ever exceed
1.0, even considering possible background contributions of similar
noncarcinogens.  Therefore, we feel that the maximum modeled target
organ-specific HI of 0.4 from the turbine subcategories supports an
initial determination that emissions from these sources do not exceed a
level which is adequate to protect public health with an ample margin of
safety.  

For ecological endpoints for which we have data, we also find very low
hazards and therefore, we do not anticipate that any adverse
environmental effects will result from emissions from any source in
these four subcategories. 

Given the standard EPA risk assessment methods used, and the
conservative assumptions made in this assessment, we have made an
initial determination that all sources in the four subcategories meet
the human health and environmental criteria in CAA section 112(c)(9)(B)
and should be removed from the source category list.

VIII.  Statutory and Executive Order Reviews

A.  Executive Order 12866:  Regulatory Planning and Review 

Under Executive Order 12866 (58 FR 51735, October 4, 1993), EPA must
determine whether the regulatory action is “significant” and,
therefore, subject to Office of Management and Budget (OMB) review and
the requirements of the Executive Order.  The Executive Order defines
“significant regulatory action” as one that is likely to result in a
rule that may:

(1)  Have an annual effect on the economy of $100 million or more or
adverse affect in a material way the economy, a sector to the economy,
productivity, competition, jobs, the environment, public health or
safety, or state, local or tribal governments or communities;

(2)  create a serious inconsistency or otherwise interfere with an
action taken or planned by another agency; 

(3)  materially alter the budgetary impact of entitlements, grants, user
fees, or loan programs, or the rights and obligation of recipients
thereof; or 

(4)  raise novel legal or policy issues arising out of legal mandates,
the President’s priorities, or the principles set forth in the
Executive Order.

Pursuant to the terms of Executive Order 12866, it has been determined
that the proposed action does not constitute a “significant regulatory
action” and is, therefore, not subject to OMB review.

B.  Paperwork Reduction Act

This action does not impose an information collection burden under the
provisions of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq.  The
proposed action will remove two subcategories from the combustion
turbine source category and, therefore, eliminate the need for
information collection toward regulatory compliance under the CAA. 
Burden means the total time, effort, or financial resources expended by
persons to generate, maintain, retain, or disclose or provide
information to or for a Federal agency.  This includes the time needed
to review instructions; develop, acquire, install, and utilize
technology and systems for the purposes of collecting, validating, and
verifying information, processing and maintaining information, and
disclosing and providing information; adjust the existing ways to comply
with any previously applicable instructions and requirements; train
personnel to be able to respond to a collection of information; search
data sources; complete and review the collection of information; and
transmit or otherwise disclose the information.  An Agency may not
conduct or sponsor, and a person is not required to respond to a
collection of information unless it displays a currently valid OMB
control number.  The OMB control numbers for EPA’s regulations are
listed in 40 CFR part 9 and 48 CFR chapter 15.	

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 business, small organizations,
and small governmental jurisdictions.  For the purposes of assessing the
impacts of today’s proposed rule on small entities, small entity is
defined as:  (1) a small business that meets the definitions for small
business based on the Small Business Association (SBA) size standards
which, for this proposed action, can include manufacturing (NAICS
3999-03) and air transportation (NAICS 4522-98 and 4512-98) operations
that employ less 1,000 people and engineering services (NAICS 8711-98)
operations that earn less than $20 million annually; (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 impact of today’s proposed rule on
small entities, I certify that the proposed action will not have a
significant economic impact on a substantial number of small entities. 
In determining whether a rule has significant economic impact on a
substantial number of small entities, the impact of concern is any
significant adverse economic impact on small entities, since the primary
purpose of the regulatory flexibility analysis is to identify and
address regulatory alternatives “which minimize any significant
economic impact of the proposed rule on small entities.”  (5 U.S.C.
603 and 604).  Thus, an agency may certify that a rule will not have a
significant economic impact on a substantial number of small entities if
the rule relieves regulatory burden, or otherwise has a positive
economic effect on all of the small entities subject to the rule.  The
proposed rule will eliminate the burden of additional controls to be
applied to two subcategories of the combustion turbine source category,
and associated operating, monitoring and reporting requirements.  We
have, therefore, concluded that today’s proposed rule will relieve
regulatory burden for all small entities.  We continue to be interested
in the potential impacts of the proposed rule on small entities and
welcome comments on issues related to such impacts.

D.  Unfunded Mandates Reform Act

Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Public
Law 1044, 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
1 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.

Today’s proposed rule contains no Federal mandates for State, local,
or tribal governments or the private sector.  The proposed rule imposes
no enforceable duty on any State, local or tribal governments or the
private sector.  In any event, EPA has determined that the proposed 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 1 year.  Because the proposed
rule removes two subcategories from the combustion turbine source
category from regulatory consideration, it actually reduces the burden
established under the CAA.  Thus, today’s proposed rule is not subject
to the requirements of sections 202 and 205 of the UMRA.

E.  Executive Order 13132: Federalism

Executive Order 13132 (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.”

The proposed rule 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.  Thus, Executive Order 13132 does
not apply to the proposal.

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

Executive Order 13175 (65 FR 67249, November 9, 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.”  The proposed rule does not have tribal
implications, as specified in Executive Order 13175.  The proposed
action will eliminate control requirements for two subcategories from
the combustion turbine source category and, therefore, reduces control
costs and reporting requirements for any tribal entity operating a
turbine contained in either of these subcategories.  Thus, Executive
Order 13175 does not apply to the proposed rule.

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

Executive Order 13045 (62 FR 19885, April 23, 1997) applies to any rule
that: (1) is determined to be “economically significant” as defined
under Executive Order 12866, and (2) concerns an environmental health or
safety risk that EPA has reason to believe may have a disproportionate
effect on children.  If the regulatory action meets both criteria, the
Agency must evaluate the environmental health or safety effects of the
planned rule on children, and explain why the planned regulation is
preferable to other potentially effective and reasonably feasible
alternatives considered by the Agency.

The EPA interprets Executive Order 13045 as applying only to those
regulatory actions that are based on health or safety risks, such that
the analysis required under section 5-501 of the Executive Order has the
potential to influence the regulation.  The proposed rule is not subject
to Executive Order 13045 because it is not economically significant as
defined in Executive Order 12866, and because the Agency does not have
reason to believe the environmental health or safety risks addressed by
this action present a disproportionate risk to children.  This
determination is based on the fact that the noncancer human health
values we used in this analysis (e.g., RfC) are determined to be
protective of sensitive sub-populations, including children.  Also,
while the cancer human health values do not always expressly account for
cancer effects in children, the cancer risks posed by turbines in these
two subcategories are sufficiently low so as not to be concern for
anyone in the population, including children.  In addition, the public
is invited to submit or identify peer-reviewed studies and data, of
which the Agency may not be aware, that assesses results of early life
exposure to the HAP emitted by lean premix gas-fired combustion turbines
and diffusion flame gas-fired combustion turbines.

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

The proposed rule is not subject to Executive Order 13211 (66 FR 28355,
May 22, 2001) because it is not a significant regulatory action under
Executive Order 12866.

I.  National Technology Transfer and Advancement Act 

Section 112(d) of the National Technology Transfer and Advancement Act
of 1995 (NTTAA), (Public Law No. 104-113, section 12(d) 915 U.S.C. 272
note), directs all Federal agencies to use voluntary consensus standards
instead of government-unique standards in their regulatory activities
unless to do so would be inconsistent with applicable law or otherwise
impractical.  Voluntary consensus standards are technical standards
(e.g., material specifications, test method, sampling and analytical
procedures, business practices, etc.) that are developed or adopted by
one or more voluntary consensus standards bodies.  Examples of
organizations generally regarded as voluntary consensus standards bodies
include the American society for Testing and Materials, the National
Fire Protection Association A), and the Society of Automotive Engineers.
 The NTTAA requires Federal agencies like EPA to provide Congress,
through OMB, with explanations when an agency decides not to use
available and applicable voluntary consensus standards.  The proposed
rule does not involve technical standards.  Therefore, EPA is not
considering the use of any voluntary consensus standards.

List of Hazardous Air Pollutants, Petition Process, Lesser Quantity
Designations, Source Category List

Page 70 of 71 

List of Subjects in 40 CFR part 63

Environmental protection, Air pollution control, Hazardous substances,
Reporting and recordkeeping requirements.

________________________

Dated:

_________________________

Marianne Lamont Horinko,

Acting Administrator



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