Risk Screen on Substitutes for Halon 1301

Fire Suppression and Explosion Protection Applications

Proposed Substitute: Envirogel

Total Flooding Applications in Occupied Spaces

This risk screen does not contain Clean Air Act (CAA) Confidential
Business Information (CBI) and, therefore, may be disclosed to the
public.



Introduction

Ozone-depleting substances (ODS) are being phased out of production in
response to a series of diplomatic and legislative efforts that have
taken place over the past few years, including the Montreal Protocol and
the Clean Air Act Amendments of 1990 (CAAA).  The U.S. Environmental
Protection Agency (EPA), as authorized by Section 612 of the CAAA, is
developing a program to evaluate human health and environmental risks
posed by alternatives to ODS.  The main purpose of EPA's program, called
the Significant New Alternatives Policy (SNAP) program, is to identify
acceptable and unacceptable substitutes for ODS in specific end uses.  

							

EPA’s decision on the acceptability of a substitute is based largely
on the findings of a screening assessment of potential human health and
environmental risks posed by the substitute in specific applications. 
EPA has already screened a large number of substitutes in many end uses
within all of the major ODS-using sectors, including refrigeration and
air conditioning, solvent cleaning, foam blowing, aerosols, fire
suppression, adhesives, coatings and inks, and sterilization.  The
results of these risk screens are presented in a series of Background
Documents that are available in EPA's docket.

The purpose of this report is to supplement EPA’s Background Document
on the fire suppression and explosion protection sector (hereinafter
referred to as the Background Document).1 This risk screen discusses
potential human health and environmental risks posed by Envirogel, a
gelled halocarbon/dry chemical suspension, to replace Halon 1301 for use
as a total flooding agent in occupied areas. The use of Envirogel in
streaming applications is not addressed in this risk screen.

The fire-extinguishing product submitted under the name Envirogel has
three proposed formulations: it consists of [ ] which is aerosolized
upon discharge from the fire extinguishing apparatus.  [ .]  This risk
screen reviews human health and environmental impacts of only the
formulations consisting of [ ] containing blends.  [ ] and [ ] have been
previously approved for use as a total flooding agent by EPA’s SNAP
program.  Use of [ ], [ ] and [ ] must follow the requirements in the
latest version of the National Fire Protection Association (NFPA) 2001
Standard for Clean Agent Fire Extinguishing Systems which establishes
safe exposure times based upon PBPK modeling. 

This risk screen does not further review the toxicity of [ ], [ ], [ ]
or the [ ] as all these chemicals have been previously approved for use
in fire suppression formulations under the SNAP program.  Section 2 of
this report summarizes the results of the risk screen for Envirogel;
Section 3 presents atmospheric modeling and potential environmental
risks; Section 4 discusses occupational exposure at manufacture; Section
5 discusses exposure at end use; Section 6 assesses risks associated
with general population exposure; and Section 7 assesses the emissions
of volatile organic compounds.

Table 1.  Composition of Envirogel

Constituent	Chemical Formula	CAS No.	Percent of Total (by weight)



































	

Summary of Results

Based on the assessment of [ ] and the [ ] in which it is suspended,
Envirogel is recommended for SNAP approval as a total flooding agent for
extinguishing fires in occupied spaces.  In addition, any other
halocarbon on the SNAP-approved list, to the extent that it can be
safely and efficiently blended with [ ] to form a dispersible mixture,
is also acceptable with the recommendation that the use of the [ ] blend
minimizes any exposure, follows applicable industry standards, and
prevents potential increase in body pH level of exposed individuals. 
Use conditions for total flooding applications are governed by
organizations including NFPA, Underwriters Laboratories, and OSHA.  Use
of the SNAP-approved chemical discussed in this risk screen is subject
to requirements of these agencies.

  

The risk screen indicates that the use of the proposed substitute in
occupied spaces will be less harmful to the atmosphere than the
continued use of Halon 1301.  The Envirogel blend containing [ ] should
not be used as a total flooding agent unless no technically feasible
substitute is available.  In particular, because the global warming
potential (GWP) of [ ] is [ ], EPA’s SNAP Program recommends that it
not be used in total flooding fire protection applications where other
approved formulations have been shown to be feasible.  Envirogel blends
containing [ ] or [ ] have significantly lower GWPs than those
containing [ ].

Risk to the general population is expected to be below levels of concern
for non-cancer risks, and occupational exposure should not pose a
problem as long as [ ] is manufactured under conditions that do not
utilize the highly toxic [ ].  However, during end-use,   SEQ CHAPTER \h
\r 1 in the event of an accidental release in a normally occupied space,
Envirogel may pose risks to human health.  For example, if an individual
must remain in the post-release environment to perform a critical
function, exposures may lead to unreasonable health risks.  These risks
necessitate that special training be provided for individuals required
to be in environments protected by Envirogel extinguishing systems. 
Also, it is suggested that potential hazards associated with use of
Envirogel, as well as handling procedures to reduce risk resulting from
these hazards, be clearly labeled on each canister used in total
flooding extinguishing systems, as well as in literature describing the
systems and their use.  Finally, if personnel will be exposed to the
proposed powdered aerosol blend for more than five minutes, a
self-contained breathing apparatus (SCBA) must be used. 

The [ ] component of the Envirogel blend may increase the body’s pH
level; however, the effects are expected to be negligible because of the
body’s compensatory mechanisms that restore the pH to normal range. 
Thus, the use of the [ ] blend is approved with the recommendation that
the exposure to this fire suppressant be minimized as much as possible,
and exposed individuals be offered an electrolyte solution to drink
afterwards to help restore the pH within the appropriate range. 

Atmospheric Modeling 

This section presents an assessment of the potential risks to
atmospheric integrity posed by the use of Envirogel as a total flooding
agent in occupied areas.  According to the submitter, all components of
Envirogel have ozone-depletion potentials (ODPs) of 0 (Table 2). 
Because [ ] and [ ] have already been approved under the SNAP program,
this risk screen does not address the atmospheric risks associated with
these components. Based on the findings of the previous risk screen
performed for Envirogel and on the benign atmospheric impacts of [ ],
the use of Envirogel is believed to be less damaging to the atmosphere
than continued use of Halon 1301.

  

Table 2.  ODPs, GWPs, and Atmospheric Lifetimes of the Constituents of
Envirogel

Substitute	ODP	100-Year GWP

(relative to CO2)	ALT (years)





















Source: Submitter, IPCC (1994, 1995), The UNEP Ozone Secretariat Webpage
(2000)

However, it should be noted that [ ] has a high GWP and ALT; therefore,
emissions should be kept to a minimum by avoiding discharge during
testing or training, and maintaining a high level of maintenance to
avoid leaking or accidental discharge.  Furthermore, blends with [ ]
should not be used if there are other technically feasible alternatives
available.  Envirogel blends containing [ ] and [ ] are available, and
these blends have a lower global warming potential than the blends
containing [ ].  Therefore, Envirogel blends containing [ ] should not
be used under most circumstances.  

Occupational Exposure at Manufacture

It is recommended that workers exposed to [ ] during the manufacturing
or filling of fire extinguishers handle the [ ] in a hood and follow
good manufacturing practices if there is a risk of dispersing the dust. 
For those cases where [ ] is handled outside of the hood, the
manufacturing area should be equipped with a ventilation system and
employees should be required to wear gloves, particulate respirators
with fine dust rating/capability, and goggles.  Also an eye wash
fountain and quick drench facilities must be close by the production
area.   In the case of an accidental spill, workers should wear their
protective equipment while wet vacuuming the [ ].  	

[ ] must be manufactured using methods that do not produce [ ] directly
from [ ].  [ ] is an extremely toxic substance that is dangerous in
small concentrations.  The ACGIH TLV for [ ] is 0.01 ppm.  Because it is
not possible to control the level of this impurity in the end product, a
manufacturing process that converts [ ] directly to [ ] is expected to
pose an unacceptable health risk to workers. 	

Exposure at End Use

[ ] and [ ] Exposure After Release

The toxicity of [ ] and [ ] have already been investigated and approved
under the SNAP program.  They are not expected to pose a significant
risk to manufacture workers or to consumers.

Because the assessed constituents of Envirogel have been formulated to
be minimally toxic and because only acute exposure to these chemicals
are expected, evaluation of additional information (such as aerosol
particle size distribution upon discharge) is not thought to be
necessary.

[ ] Exposure After Release

Although the toxicity of [ ] is low, the greatest risk to humans is its
ability to increase the body’s pH level.  The proposed Envirogel
formulation contains soluble particles of [ ] that, when inhaled, may
deposit in the respiratory tract.  These soluble particles could
potentially cross the biological membranes of the respiratory system and
enter the systemic circulation.  The absorption of a large amount of [ ]
could potentially have an impact on the body’s acid-base balance.  To
determine the potential impact of inhaled [ ] on the body’s acid-base
balance, the effect of an accidental release of [ ] was modeled.

						

Using information provided by the submitter, a reasonable release
scenario was constructed in which a release of the proposed blend occurs
in room with an internal volume of 300 ft3.  A fire was contained with [
] lbs of the product (information provided by submitter).  The following
assumptions were made:

twenty-five percent of the [ ] particles will be available for
dissolution and uptake within the pulmonary region of the lungs (i.e.,
diameter ≤10 µ m) (US EPA 1994);

the average ventilation rate of a 70 kg, 18-30 year-old male in moderate
activity is 1.74 m3/hr (US EPA 1997);

the average ventilation rate of a 57 kg, 18-30 year-old female in
moderate activity is 1.4 m3/hr (US EPA 1997); and

the human body has 70 mL blood/kg; therefore, a 70 kg male has 4.9 L of
blood and a 57 kg female has 4.0 L of blood (Guyton and Hall 1996).

An assumption has been made that only 25% of the [ ] particles are
respirable.  This assumption is based on a general knowledge of the
size of the particles required to be effective for fire suppression
(less than or equal to 10 microns) and the knowledge that particles that
are larger than 5 microns do not effectively enter the pulmonary region
of the human lung (where soluble particles could dissolve in surfactant
and enter the circulatory system).  This assumption considers that only
those particles entering the pulmonary region will be available to
contribute to the systemic burden of [ ] by dissolution in the alveolar
space and passage into the circulatory system.  It ignores potential
dissolution of [ ] in the tracheobronchial tree and in other parts of
the upper respiratory passages (e.g, nose and mouth).  It also ignores
potential clearance of those particles entering the upper respiratory
system and trachea via the mucociliatory escalator and those particles
that might be captured in the mouth or throat during combined nasal and
oral breathing that occurs in humans during exercise and stressful
situations/events.  In the absence of a more in-depth and complicated
analysis of the potential pathways and clearance mechanisms for [ ] in
the respiratory system, the assumption has been made that only 25% of
the aerosolized particles will be respirable and available to
potentially induce systemic toxicity (via an increase in blood pH).  

Given the assumptions listed above, a 70 kg, 18-30 year-old male would
inhale approximately 3.75 g of [ ] (0.045 mole) in the five-minute
egress time established by the NFPA.  The inhaled [ ] results in a blood
pH of 7.54. A female that is 57 kg, 18-30 year-old, would inhale
approximately 3.02 g of [ ] (0.036 mole) in a five- minute egress time.
The blood pH would be 7.54.

The normal range for blood pH is 7.35-7.45.  According to the model, the
exposure to 0.045 mole [ ] increases the blood pH to above the typical
range.  The body’s physiological response to an increase in blood pH
varies with the individual and this increase will not necessarily occur.
 Actual effects of the inhaled [ ] are expected to be negligible because
the body’s compensatory mechanisms would work to restore blood pH to
within the normal range. A blood pH of 7.52 and higher is considered
alkalemic, which can be life-threatening to susceptible individuals
(e.g., people with cirrhosis of the liver, congestive heart failure,
impairment of renal function, or toxemia related to pregnancy). Given
the assumption that 25% of the [ ] inhaled is respirable, the other 75%
is either coughed up and swallowed, or exhaled back into the breathing
space.  The remaining ingested dose is available to potentially induce
systemic effects following absorption in the gastrointestinal tract.  

Case reports from the literature indicate that metabolic alkalosis
(increase in serum pH) can occur in humans following an overdose of
ingested antacids containing [ ].  For example, in one case, metabolic
alkalosis was induced in a man who ingested over 5700 mg [ ] per day for
6 months (Okada et al., 1996).  This daily dose is much larger than
that modeled in the current risk screen.  Therefore, it is not believed
that exposure to [ ] from a 5-minute exposure to Envirogel containing [
] will induce any adverse effects related to increased serum pH. 
Because it is impossible to predict a person's susceptibility to pH
changes, however, it is advised that exposure to this fire suppressant
be minimized as much as possible, and exposed individuals should be
offered an electrolyte solution to drink afterwards to help restore
physiological pH within the appropriate range.  Finally, if personnel
will be exposed to the proposed powdered aerosol blend for more than
five minutes, a self-contained breathing apparatus (SCBA) must be used. 

Post-Activation Disposal

Workers should not enter the space following discharge until all
particles have settled and the gases released by the system have
dissipated.  The submitter should provide guidance upon installation
regarding the appropriate time frame after which workers may enter the
activation site for disposal to allow the maximum settling of all the
particulates. Clean-up operations are likely to result in the
re-circulation of dust particles.  Therefore, workers entering the
protected volume to clean-up after activation are required to wear
gloves, goggles, and a particulate removing respirator with a fine dust
rating capability.  The contents removed from the protective volume
should be disposed of according to approved safety procedures. 
Equipment should be thoroughly decontaminated after use.  When
recommended safety precautions are followed, no significant adverse
health effects should result. 

Hypothetical Maximum [ ] Release in Industrial Settings	

Using the model described in Section 5b, the hypothetical maximum
amounts of [ ] that can be released in an enclosed space without
adversely increasing the pH in the blood of occupational workers were
calculated.  Three rooms of different sizes were used: a phone closet
(192 ft3), a small office (960 ft3), and a computer room (8000 ft3).  
The following assumptions were made:

blood pH would not exceed 7.45 (the upper bound of the normal-range);

twenty-five percent of the [ ] particles will be available for
dissolution and uptake within the pulmonary region of the lungs (i.e.,
diameter ≤10 µm) (US EPA 1994);

the average ventilation rate of a 70 kg, 18-30 year-old male in moderate
activity is 1.74 m3/hr (US EPA 1997);

the average ventilation rate of a 57 kg, 18-30 year-old female in
moderate activity is 1.4 m3/hr (US EPA 1997); and

the human body has 70 mL blood/kg; therefore, a 70 kg male has 4.9 L of
blood and a 57 kg female has 4.0 L of blood (Guyton and Hall 1996)

The hypothetical maximum amount of [ ] is summarized in Table 2.  The
hypothetical maximum amount of respirable [ ] for males ranged from
0.106 to 4.43 lbs. and the calculated maximum amount that could be
released in the protected space (limited by the target blood pH) ranged
from 0.426 to 17.7 lbs.  The values for females were slightly lower due
to the lower blood volume and lower weight.

The values listed in Table 2 indicate the hypothetical maximum amount of
[ ] that could be released for the particular modeled space that would
not be expected to result in an increase in blood pH above the normal
physiological range for each of the three typical industrial scenarios. 
The results are dependent on the size of the room; therefore, the larger
the room, the greater the amount of [ ] that can be released.  The
calculations described herein [ ] can be used to estimate the amount of
respirable [ ] (and thus the hypothetical maximum amount that should be
released) for rooms whose sizes differ from those modeled in this risk
screen.  It should be noted that these values are conservative estimates
based on the conservative exposure assumptions discussed above.

Table 2.  Maximum Release Amount and Respirable Amount By Room Size for
Males and Females

Room Dimensions 

(ft, L x W x H)	Room Size (ft3)	Room Size (m3)	Max. Amount  Respirable
(lb): Males	Max. Amount  Respirable (lb): Females	Max. Amount Released
(lb): Males	Max. Amount Released (lb): Females

6 x 4 x 8	192	5.44	0.10	0.10	0.39	0.39

12 x 10 x 8	960	27.18	0.49	0.49	1.95	1.95

40 x 25 x 8	8000	226.53	4.1	4.1	16.4	16.4

													

General Population Exposure	

Exposure to Envirogel resulting from its processing or use as a flooding
agent in occupied areas is not expected to cause any significant threats
to human health in the general population.  The only consumer exposure
to Envirogel will be during discharge of fire extinguishers in occupied
spaces.  Upon discharge of a typical [ ] extinguisher with an average [
] in a 12'x12'x8' room, the submitter claims that exposure to the
Envirogel halocarbon components will be less than 1.0% (10,000 ppm),
below the NOAELs of both [ ], and [ ]. 

						

Fire fighters and those exposed to combustion should wear full
protective clothing, including self-contained breathing apparatuses. 
Equipment should be thoroughly decontaminated after use.  When
recommended safety precautions are followed, no significant adverse
health effects should result. 

Ambient Air

The general population exposure to Envirogel is not expected to cause
any significant threats to human health.  Emissions resulting from both
the processing and use of Envirogel are expected to be well below the
acceptable exposure limits for non-cancer endpoints. 

Surface Water

The physicochemical properties of the majority of halon substitutes make
it unlikely that the substitutes would be released to surface water as a
result of use.  In the case of Envirogel, [ ] constituent would rapidly
vaporize during expulsion from the container, and the [ ] gel would
settle onto the floor of the occupied space.  Because the solid waste
would be removed from the site using a wet vacuum and disposed of
according to federal, state, or local requirements, the Envirogel
components are not likely to settle into nearby streams or ponds.

Solid Waste				

As discussed above, the solid component of Envirogel must be disposed of
in accordance with federal, state, or local requirements.  However, it
is not required that the [ ] gel be handled as a hazardous waste.  

Volatile Organic Compound Analysis

In Chapter 7 of the Background Document, EPA estimated the impact of
potential increases in volatile organic compound (VOC) emissions from
the use of substitutes for ozone-depleting substances.  It was shown
that VOC emissions from substitutes for Halon 1301 in fire extinguishing
systems are likely to be insignificant compared to VOC emissions from
all other sources (i.e., both anthropogenic and biogenic).  Further, [ ]
and [ ] are VOC-exempt compounds for purposes of State implementation
plans for controlling smog, which indicates that the impacts of these
substitutes are not of concern.

References		

Guyton, A.C., MD and Hall, J.E., PhD. 1996. Textbook of Medical
Physiology 9th ed. W.B. Saunders Co.,  Philadelphia. p.  299.

NFPA. 2000. Standard on Clean Fire Extinguishing Systems.

Okada K., Kono N., Kobayashi S., and Yamaguchi S.  1996.  Metabolic
alkalosis and myoclonus from antacid ingestion.  Intern Med 35:515-6.

U.S. EPA.  1997. Exposure Factors Handbook.  EPA/600/P-95/002Fa.  Office
of Research and Development, Washington, DC.  August 1997.

	

U.S. EPA.  1994.  Methods for Derivation of Inhalation Reference
Concentrations and Application of Inhalation Dosimetry. 
EPA/600/8-90/066F.  Office of Research and Development, Washington, DC. 
October 1994.

1U.S. EPA, 1994. Risk Screen on the Use of Substitutes for Class I
Ozone-Depleting Substances: Fire Suppression and Explosion Protection
(Halon Substitutes).  Stratospheric Protection Division.  March 1994.

3 In the event of a rise in serum pH, the body compensates by decreasing
respiration, which effectively increases the pCO2 level, thus decreasing
the pH and/or the kidneys change their retention of [ ] to restore
proper balance.

Ì

Ô

&

F

ll be exposed to the blend for more than 5 minutes, then workers are
required to wear gloves, goggles, and SCBA.  

September 6, 2006

  PAGE  1 

