Document ID: EPA-HQ-OAR-2009-0286-0020
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2010-05-10T04:00Z

Significant New Alternatives Policy Program 

Refrigeration and Air Conditioning Sector

Risk Screen on Substitutes for CFC-12 and HCFC-22 in 

Household Refrigerators and Freezers

Substitute: HCR-188C1® 

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

1. 	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 decade, 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 the 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 refrigeration and air conditioning sector (EPA 1994) (hereinafter
referred to as the Background Document) by adding to the list of
potential substitutes for specific end-uses of CFC-12 and HCFC-22 in
this sector.  Proposed end-use applications considered in this analysis
include new replacements for the following end uses: household
refrigerators and freezers.  The specific proposed CFC-12 and HCFC-22
substitute blend examined in this report is shown in   REF _Ref173102842
\h  \* MERGEFORMAT  Table 1 . 

Table   SEQ Table \* ARABIC  1 .  Composition of HCR-188C1.

Component	Weight Percent %

n-Butane

	Ethane 

	Isobutane

	Propane 

	The potential risks associated with use of the constituents of this
blend in residential refrigeration have been examined at length in the
Background Document.  The reader is referred to this reference for a
detailed discussion of the methodologies used to conduct this risk
screen.  Presently, EPA’s SNAP Program has not approved any
hydrocarbon blends as a substitute for CFC-12 and HCFC-22 in residential
appliance end uses, such as those intended for this substitute (i.e.,
household refrigerators and freezers).  Of particular concern are the
flammability risks associated with hydrocarbon blends during
manufacturing, use, servicing, and disposal of household appliances. 
Occupational exposure modeling was performed to ensure that use of the
proposed blend in the applications listed above did not pose
unacceptable risk to workers.  Consumer exposure modeling was performed
to examine potential catastrophic releases for each of the chemical
constituents of the proposed blend.  Lastly, general population exposure
modeling was performed to ensure that the proposed blend would not pose
unacceptable risk to the population at large.  

Section 2 of this report summarizes the results of the risk screen for
the proposed substitute blend listed in   REF _Ref173102842 \h  \*
MERGEFORMAT  Table 1 .  The remainder of the report is organized into
the following sections:

Section 3: Atmospheric Assessment

Section 4: Flammability Assessment

Section 5: Asphyxiation Assessment

Section 6: Toxicity Assessment

Section 7: Volatile Organic Compound Assessment 

Section 8: References

2.	 SUMMARY OF RESULTS						

HCR-188C1 is recommended for SNAP approval for household refrigerators
and household freezers.  EPA's risk screen indicates that the use of the
proposed substitute and its constituents will be less harmful to the
atmosphere than the continued use of CFC-12 and HCFC-22.   No
significant toxicity risks to workers, consumers, or the general
population are expected according to occupational and consumer exposure
modeling. 

Flammability models indicate that risks of explosion are not a concern
for consumers when the substitute is used in refrigerators or freezers
provided that the refrigerators’ and freezers’ charge sizes are
determined according to the UL 250 Supplement SA standard (see Section
4).  Caution must be used in manufacturing facilities and by
refrigeration technicians to minimize explosion risk, while in the
presence of large quantities of the substitute.  This includes
installation of proper safety equipment during manufacturing,
transportation, and storage and providing proper training and
certification to technicians.  EPA recommends that American Society of
Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standards
15 and 34 be followed.  

3. 	ATMOSPHERIC MODELING

This section presents an assessment of the potential risks to
atmospheric integrity posed by the use of HCR-188C1 in the residential
refrigeration sector.  The ODP, GWP, and atmospheric lifetime (ALT) of
the proposed substitute are presented in   REF _Ref175036149 \h  \*
MERGEFORMAT  Table 2 .	

The environmental impacts resulting from use of HCR-188C1 are generally
in the range of those predicted for other substitutes examined in the
Background Document.  The substitute is substantially less harmful to
the ozone layer, has less climate impact, and a shorter atmospheric
lifetime compared to CFC-12 and HCFC-22.

Table   SEQ Table \* ARABIC  2 .  Atmospheric Impacts of HCR-188C1
Compared to CFC-12 and HCFC-22.

Refrigerant	Ozone Depleting Potential (ODP)	Global Warming Potential
-AR4a (GWP)	Atmospheric Lifetime (ALT)

n-Butane	0	4.0a	0.018b

Ethane	0	5.5a 	0.21b 

Isobutane	0	NA	0.019b

Propane	0	3.3a	0.041b

CFC-12	1c	10,900a	100a

HCFC-22	0.055c	1,810 a	12a

NA – Not available in IPCC 4th Assessment Report.

a IPCC 4th Assessment Report (Forster et al. 2007).

bIPCC/TEAP (2005).

b Available at: http://www.epa.gov/ozone/ods.html.

4.	FLAMMABILITY ANALYSIS

Due to its flammable nature, HCR-188C1 could pose a significant safety
concern for workers and consumers if it is not handled carefully.  In
the presence of an ignition source (e.g., static electricity, a spark
resulting from a closing door, or a cigarette), an explosion or a fire
could occur when the concentration of HCR-188C1 exceeds its lower
flammability limit (LFL) of 16,100 ppm.  Therefore, it is important to
ensure that the levels of HCR-188C1 do not exceed 16,100 ppm.  In
production facilities or other facilities where large quantities of the
refrigerant will be stored, proper safety precautions should be in place
to minimize the risk of explosion.  White goods installed with HCR-188C1
should be clearly labeled as containing a flammable refrigerant charge. 
Furthermore, only refrigerant technicians certified to work with
flammable refrigerants should handle these units during manufacturing,
installation, servicing, transportation and disposal.        

To determine whether flammability would be a concern for consumers, a
reasonable worst-case scenario analysis was performed to model
catastrophic releases of the refrigerant into the room.  The analysis
models the release of charge from a refrigerator into a kitchen. An
average kitchen volume is assumed to be 18 m3 (635 ft3) or approximately
2.7 x 2.7 m (8.9 x 8.9 ft) for a square room with 2.4 m (8 ft) ceilings
(EPA 1994).  The full charge of the unit is assumed to be emitted within
one minute and the kitchen is assumed to have an air flow rate of 2.5
air exchanges per hour.  Given these conservative assumptions, the
assumed “worst-case” scenario is highly unlikely.   Horizontal
stratification is also assumed since components of HCR-188C1 are denser
than air and will settle in higher concentrations closer to the ground. 
In order to simulate the horizontal concentration gradient that will
occur because of the weight differential between the refrigerant and
air, it is assumed that 95 percent of the leaked refrigerant mixes
evenly into the bottom 0.4 meter of the room, and the rest of the
refrigerant mixes evenly in the remaining volume (Kataoka 1999).

Under catastrophic release scenarios, the concentration of HCR-188C1 in
the lower stratum of the kitchen would be approximately 40 percent of
the substitute’s LFL for the average room size assumed, as shown in  
REF _Ref173919379 \h  \* MERGEFORMAT  Table 3 .  

Table   SEQ Table \* ARABIC  3 .  Flammability Assessment.

Room Type/Appliance Type	Average Scenario	Risk Scenario

	Room Size (m3)	Instantaneous Concentration (ppm)	Room Size (m3)
Instantaneous Concentration (ppm)

Kitchen/Refrigerator	18 (635 ft3)	6,628a	7.5 (265 ft3)	15,827a

a Lower Flammability Limit of HCR-188C1 is equal to 16,100 ppm

For flammability to be of concern under the conservative (protective)
assumptions described above, the volume of the kitchen would have to be
7.5 m3 (265 ft3).  Assuming a square room with a ceiling height of 2.4 m
(8.0 ft), this equates to a 1.75 x 1.75 m (5.75 x 5.75 ft) kitchen.  

To mitigate the risks of flammability at the end-use, it is recommended
that HCR-188C1 refrigerators' and freezers’ charge sizes are
determined according to the UL 250 Supplement SA standard.  Per the UL
standard, the maximum permissible leak for refrigerants with limits of
flammability and heat of combustion greater than 19,000 kj/kg (such as
the components of HCR-188C1) is 50 g.  Additional charge is not
prohibited, however, if the amount of refrigerant leaked during testing
does not exceed 50 grams.  Therefore, a slightly larger charge would be
permissible to compensate for the refrigerant’s solubility in the
system’s oils so long as any leaks would not exceed 50g.  By ensuring
HCR-188C1 refrigerators and freezers conform to the aforementioned
standard, flammability risks associated with the use of HCR-188C1 in
these appliances should be mitigated.

Catastrophic releases of large quantities of refrigerant during
servicing and manufacturing, especially in areas where large amounts of
refrigerant are stored, could cause an explosion.  For this reason, it
is important that only properly trained and certified refrigerant
technicians handle HCR-188C1.  The submitter has provided safety
guidelines for handling HCR-188C1, which should be followed.   Using
these guidelines, certification requirements and training programs for
technicians that handle HCR-188C1 should be developed.  As a further
precaution, HCR-188C1 storage and transport equipment should be
installed with safety devices that minimize the likelihood of
catastrophic releases.  For example, NFPA 58 Liquefied Petroleum Gas
Code (NFPA, 2007) for liquefied propane requires the use of overfill
protection devices (OPD) on cylinders to minimize the likelihood of
leaks.  The NPFA 58 Code also contains propane storage and
transportation requirements/guidelines.  Similar equipment safety and
procedural requirements should be developed for HCR-188C1 and other
flammable refrigerants.  

It is important that the strictest standards be followed during
manufacturing.  It is recommended that refrigerants be properly stored
and caution used within manufacturing facilities to minimize explosion
risk and that workers adhere to the requirements set by OSHA under 29
CFR 1910.  OSHA requirements include proper ventilation and storage
practices within manufacturing facilities to prevent fire and explosion.
 Proper ventilation should be maintained at all times during the
manufacture of equipment containing HCR-188C1 through adherence to good
manufacturing practices.  If refrigerant levels in the air surrounding
the equipment rise above one-fourth of the lower flammability limit, or
oxygen levels in the room fall below 19.5% as noted in the material
safety data sheet provided by the submitter, the space should be
evacuated and re-entry should only occur after the space has been
properly ventilated.  Ventilation is also of the utmost importance to
mitigate the risk of fire or explosion when servicing equipment using
HCR-188C1.  During servicing operations, technicians should ensure that
proper ventilation is in place through the use of fans (or other
mechanical ventilation devices) and portable refrigerant detectors
should be used to alert technicians to the presence of flammable gases
in the area.  

5.	ASPHYXIATION		

The risk of asphyxiation for a “worst-case” scenario was
investigated for HCR-188C1.  This analysis does not consider conditions
that are likely to occur that would reduce the levels to which
individuals would be exposed, such as open doors or windows, fans
operating, conditioned airflow (either heated or cooled), or even
openings at the bottom of doors that allow air to flow in and out.  

For the worst-case scenario, a release from a refrigerator in a kitchen
of volume 18 m3 (635 ft3), the maximum charge of HCR-188C1 necessary to
reduce the oxygen levels to 12 percent in air was calculated assuming
horizontal stratification of the refrigerant and the air.  Horizontal
stratification is assumed since components of HCR-188C1 are denser than
air and will settle in higher concentrations closer to the ground. 
Assuming that nitrogen and oxygen retain the same relative volumes in
the rooms with the balance composed entirely of HCR-188C1, and that the
pressure of the room does not increase significantly with the addition
of the refrigerant, a charge of approximately 521 g would be necessary
to reach 12 percent oxygen in the lower stratum.  This amount represents
approximately 13 times the intended charge of approximately 40 g for a
single HCR-188C1 refrigerator or freezer.   Charge requirements to reach
the same effect in the upper stratum would be even higher because of the
stratum’s larger volume.  For asphyxiation to be of concern with the
proposed charge sizes, under the conservative (protective) assumptions
described above, the volume of the kitchen would have to be about 1.3 m3
(46 ft3).     

The results of the asphyxiation assessment are summarized in   REF
_Ref175044517 \h  \* MERGEFORMAT  Table 4  below.  EPA does not believe
that the use of HCR-188C1 in this end-use poses a significant risk of
asphyxiation or impaired coordination to consumers.

Table   SEQ Table \* ARABIC  4 .  Asphyxiation Assessment.

Room Type/Appliance Type	Appliance Charge (g)	Reasonable Worst-Case
Scenario	Asphyxiation Threshold Scenario

Room Size (m3)	Charge Causing Impairment (g)a	Room Size (m3)	Charge
Causing Impairment (g)a

Kitchen/Refrigerator	40	18 (635 ft3)	521	1.3 (46 ft3)	(40

6. 		TOXICITY REFERENCE VALUES FOR SUBSTITUTES

To assess potential health risks from exposure to this substitute in the
residential refrigeration sector, EPA identified the relevant toxicity
threshold values for comparison to modeled exposure concentrations for
different scenarios.  For the occupational exposure analysis, potential
risks from chronic and acute worker exposure were evaluated by comparing
exposure concentrations to available occupational exposure limits. 
Occupational exposure limits are typically established for either an
eight-hour time period for long-term exposure, such as the Workplace
Guidance Levels (WGLs), or for a 10 to 30-minute period for short-term
exposure, such as the Emergency Guidance Levels (EGLs), as shown in  
REF _Ref175045450 \h  \* MERGEFORMAT  Table 5  for each of the
components of HCR-188C1.  Because they are designed to assess risks from
acute exposure, emergency guidance levels are used to assess risks from
short-term consumer exposures.  Reference concentrations (RfCs) are used
to assess risks to the general population from exposure to ambient air
releases and to assess potential risks associated with chronic consumer
exposures.  A list of the relevant toxicity limits are shown in   REF
_Ref175045450 \h  \* MERGEFORMAT  Table 5 .   REF _Ref233605047 \h  \*
MERGEFORMAT  Table 6  provides definitions of the acronyms used in   REF
_Ref175045450 \h  \* MERGEFORMAT  Table 5 .   EPA’s approach for
identifying or developing these values is discussed in Chapter 3 of the
Background Document. 

Table   SEQ Table \* ARABIC  5 .  Toxicity Levels of HCR-188C1
Components.

HCR-188C1 Component 	WGL (Long-term Exposure)

ppm	EGL (Short-term Exposure)

Ppm	Reference Concentration (RfC)

mg/m3

n-Butane	800b  (NIOSH REL)	6,900 ppm g  (30 min AEGL-1)	0.95 mg/m3 i

Ethane	1,000d  (ACGIH TLV)	NA	NA

Isobutane	800c  (NIOSH REL)	18,000 h (NOAEL)	0.95 mg/m3 i

Propane	1,000a 

(OSHA PEL/NIOSH REL)	2,100e  (NIOSH IDLH)

10,000 ppm f (10 min AEGL-1)

6,900 ppm f (30 min AEGL-1)	0.9 mg/m3  i

a OSHA PEL and NIOSH REL available at:   HYPERLINK
"http://www.cdc.gov/Niosh/npg/npgd0524.html" 
http://www.cdc.gov/Niosh/npg/npgd0524.html .

b NIOSH REL available at: http://www.cdc.gov/NIOSH/NPG/npgd0068.html 

c NIOSH REL available at:   HYPERLINK
"http://www.cdc.gov/Niosh/npg/npgd0350.html" 
http://www.cdc.gov/Niosh/npg/npgd0350.html 

d ACGIH TLV available at:   HYPERLINK
"http://www.cdc.gov/niosh/ipcsneng/neng0266.html" 
http://www.cdc.gov/niosh/ipcsneng/neng0266.html .

e NIOSH IDLH available at:   HYPERLINK
"http://www.cdc.gov/Niosh/npg/npgd0524.html" 
http://www.cdc.gov/Niosh/npg/npgd0524.html .

f AEGL-1 available at:   HYPERLINK
"http://www.epa.gov/opptintr/aegl/pubs/tsd96.pdf" 
http://www.epa.gov/opptintr/aegl/pubs/tsd96.pdf 

g AEGL-1 available at:   HYPERLINK
"http://www.epa.gov/opptintr/aegl/pubs/tsd102.pdf" 
http://www.epa.gov/opptintr/aegl/pubs/tsd102.pdf 

h OSHA (2004) notes the following regarding isobutane: “OSHA does not
have a PEL for isobutane, which is affirmed as "generally recognized as
safe" as a direct human food ingredient (21 CFR 184.1165). No toxic
effects reported below 18,000 ppm.”

i SNAP Refrigerant Background Document, 1994.

Table   SEQ Table \* ARABIC  6 . Explanation of Toxicity-Related
Acronymsa

Organization 	Definition

ACGIH	American Conference of Governmental Industrial Hygienists

OSHA	Occupational Safety and Health Administration

NIOSH	National Institute for Occupational Safety and Health

Exposure Limit	Definition	Explanation

AEGL-1	Acute Exposure Guideline Level	The AEGL-1 “is the airborne
concentration… above which it is predicted that the general
population, including susceptible individuals, could experience notable
discomfort, irritation, or certain asymptomatic nonsensory effects.
However, the effects are not disabling and are transient and reversible
upon cessation of exposure” (EPA 2008a).

IDLH	Immediately Dangerous to Life and Health	If exposed to this
concentration, room occupants are expected to be able to escape the room
within 30 minutes without experiencing escape-impairing or irreversible
health effects.

NOAEL	No Observed Adverse Effect Limit	“The highest exposure level at
which there are no biologically significant increases in the frequency
or severity of adverse effect between the exposed population and its
appropriate control; some effects may be produced at this level, but
they are not considered adverse or precursors of adverse effects.”b

PEL	Permissible Exposure Limit

	This is an 8-hour time-weighted average exposure limit set by OSHA. 

REL	Recommended Exposure Limit	This is a 10-hour time-weighted average
exposure limit set by NIOSH.

RfC	Reference Concentration	A concentration “designed to protect the
general population against adverse systemic (i.e., noncancer)
effects.”

TLV	Threshold Limit Value	An 8-hour time-weighted average health-based
concentration set by ACGIH.  Exposure at or below this concentration is
believed to “not create an unreasonable risk of disease or injury.”
d

a All information in this table taken from EPA (1994), except where
noted otherwise.

b From   HYPERLINK "http://www.epa.gov/riskassessment/glossary.htm#n" 
http://www.epa.gov/riskassessment/glossary.htm#n 

c   HYPERLINK "http://www.cdc.gov/niosh/npg/pgintrod.html#exposure" 
http://www.cdc.gov/niosh/npg/pgintrod.html#exposure 

d http://www.acgih.org/TLV/

6.1  	OCCUPATIONAL EXPOSURE 

Occupational exposure modeling was performed for the components of the
proposed blend to ensure that use of the blend does not pose an
unacceptable risk to workers.  The methodology used for this screening
assessment is based on the one used in the occupational exposure and
hazard analysis described in Chapter 5 of the Background Document.  To
evaluate potential worker exposure to alternative refrigerants, a model
called the “box” model was used.  This model has been widely used
for many years to estimate probable exposures of workers to hazardous
airborne materials, and has been described in detail by the National
Institute for Occupational Safety and Health.  This model takes into
consideration the duration and magnitude of the resulting exposure which
is influenced by 1) duration and intensity of the release, 2) rate at
which contaminated air is diluted with uncontaminated air, 3) proximity
of the worker to the source of the release, and 4) the length of time
the worker remains in the affected space.  

Estimates of refrigerant release per event for various release scenarios
and data on number of events in 2007 were obtained from the Vintaging
Model.  To determine the estimated level of occupational exposure for a
constituent in a blend, the total release rate of the refrigerant is
multiplied by the weight percent composition of each compound in the
blend.  For all end-uses the release per event was conservatively
assumed to be 1 percent of the equipment charge during manufacturing and
3 percent of the equipment charge during disposal.  The release rate per
event was multiplied by the number of events estimated to occur over a
workday.  For equipment manufacturing, the number of events per workday
was assumed to equal the number of units containing the substitute
produced per plant per year divided by 240 workdays per year.  For the
purposes of this model, it is assumed that HCR-188C1 will have a market
penetration rate of 3.3% and that 12 production facilities will be in
operation.  These assumptions result in approximately 60 – 70
events/manufacturing facility/day.  This is an extremely conservative
estimate, considering less than 100 pounds of HCR-188C1 is intended to
be produced annually, for a maximum of 1145 units produced annually or
at the most five events/manufacturing facility/day.  For disposal, it
was conservatively assumed that 100 units are disposed during an 8-hour
work day.  

The maximum time weighted average (TWA) exposure was estimated for each
exposure scenario, and these values compared to the Workplace Guidance
Levels (WGLs) for each constituent of the blend.  The modeling results
indicate that both the short-term (15-minute and 30-minute) and
long-term (8-hour) worker exposure concentrations at no point exceed 2
percent of the WGLs.    REF _Ref175122161 \h  \* MERGEFORMAT  Table 6 
displays the maximum estimated 15-minute TWA occupational exposure
levels of the HCR-188C1 constituents.   Even these maximum estimated
short-term occupational levels are significantly lower than the 8-hour
long-term or 10-hour long term WGLs, and therefore occupational exposure
to any HCR-188C1 component is not considered a toxicity threat.      

Table   SEQ Table \* ARABIC  7 .  Occupational Risk Assessment

HCR-188C1 Component	Maximum 15-minute TWA Occupational Exposure Levels
(ppm)	Workplace Guidance Levels (ppm)a	Workplace Guidance Levels Time
Period

Butane

800	10-hr TWA

Ethane

1,000	8-hr TWA

Isobutane

800	10-hr TWA

Propane

1,000	10-hr TWAb

a See   REF _Ref175045450 \h  \* MERGEFORMAT  Table 5  for more
information.

b The WGL for Propane is set as a 1000 ppm 8-hr TWA by OSHA and a 10-hr
TWA by NIOSH.

6.2	CONSUMER EXPOSURE	

This section presents estimates of potential consumer exposures to
HCR-188C1 in home refrigeration appliances.  A consumer exposure
analysis was performed to examine potential catastrophic releases for
each of the chemical constituents of HCR-188C1.  Estimates for
acute/short-term consumer exposures resulting from catastrophic leakage
of refrigerant from residential refrigerators were examined.  The
analysis was undertaken to determine the 15- and 30-minute TWA for each
component of HCR-188C1, which was then compared to the standard toxicity
limits presented in   REF _Ref175045450 \h  \* MERGEFORMAT  Table 5  to
assess the risk to consumers.  However, the TWA values are fairly
conservative as the analysis does not consider opened windows, fans
operating, conditioned airflow (either heated or cooled) and other
variables that would reduce the levels to which individuals would be
exposed.

The scenario involves a refrigerant leak from a refrigerator into an
enclosed kitchen of volume 18 m3 (635 ft3).  It is assumed that the
individual is present at the start of the leak and the individual
remains in the room while the refrigerant is released. It is also
assumed that horizontal stratification causes most of the HCR-188C1 to
settle in higher concentrations closer to the ground.  Considering the
horizontal stratification is important because children, a particularly
vulnerable segment of the population, breathe air that is closer to the
ground.  In order to simulate the horizontal concentration gradient that
will occur because of the weight differential between the refrigerant
and air, it is assumed that 95 percent of the leaked refrigerant mixes
evenly into the bottom 0.4 meter of the room, and the rest of the
refrigerant mixes evenly in the remaining volume (Kataoka 1999). 
Exposure concentrations for the scenarios were calculated using the box
model described in the Background Document, which was adapted to
estimate concentrations on a minute-by-minute basis.  It was assumed
that 100 percent of the unit’s charge would be released during a time
span of 1 minute, at which time the concentration of HCR-188C1 will
peak, and then steadily decline onwards.  Refrigerant concentrations
were modeled under two air change scenarios believed to represent the
range of potential flow rates for a home, assuming flow rates of 2.5 and
4.5 air changes per hour (ACH) (Sheldon 1989).   

The highest concentrations of HCR-188C1 occur in the lower stratum of
the room and when assuming 2.5 ACH.  The highest expected levels of
consumer exposure based on this analysis are presented in  REF
_Ref175045524 \h  \* MERGEFORMAT   Table 7  below.  Even under the
conservative assumptions used in the consumer exposure modeling, the
estimated 15-minute consumer exposure level of the blend’s components
are no more than 50% of the chemicals’ short-term toxicity limits (or
in the case of ethane for which a short-term limit is not available, its
8-hour TWA long-term occupational exposure limit).  Therefore, consumer
exposure to HCR-188C1 should not pose a toxicity threat.

Table   SEQ Table \* ARABIC  8 .  Consumer Exposure Assessment

HCR-188C1 Component	15-minute TWA Consumer Exposure (ppm)	30-minute TWA
Consumer Exposure (ppm)	Short-term Exposure Limits (ppm)

Butane

	6,900a 

Ethane

	NA

Isobutane

	18,000b

Propane

	6,900a

a 30-minute AEGL-1; see   REF _Ref175045450 \h  \* MERGEFORMAT  Table 5 
for more information. 

b NOAEL; see   REF _Ref175045450 \h  \* MERGEFORMAT  Table 5  for more
information.

TWA = Time Weighted Average

NA = Not available

6.3  	GENERAL POPULATION EXPOSURE

In the SNAP Background document for refrigerants, RfC values are
available for three of the HCR-188C1 components - propane, butane, and
isobutane.  Their RfC values are are 0.9 mg/m3, 0.95 mg/m3 and 0.95
m/m3, respectively.  We assumed a conservative RfC of 0.9 mg/m3 for
the whole blend, and compared this RfC to estimated factory releases and
on-site releases.  This gives a ratio of exposure concentration to RfC
that varies between 1.3 x 10-5 to 1.8 x 10-1, depending on the type of
release scenario.  Since the exposure concentrations for these
components are lower than the RfC values, HCR-188C1 is not expected to
pose a toxicity threat to the general population.

7. 	VOLATILE ORGANIC COMPOUND (VOC) ANALYSIS

Most of the components of HCR-188C1, except ethane, have not been exempt
as a VOC under the CAA (40 CFR 51.000).  Through regulations and
standard industry practices, VOC emissions should be controlled. 
Chapter 8 of the Background Document shows that potential emissions of
VOCs from all substitutes for all end uses in the refrigeration and air
conditioning sector are likely to be insignificant relative to VOCs from
all other sources (i.e., other industries, mobile sources, and biogenic
sources).  Additional analysis shows that even if all HCR-188C1 produced
in one year were to leak over the course of the year (extremely
unlikely), the resulting annual VOC emissions would be only about 3x10-7
percent of all annual anthropogenic VOC emissions.   Further, the
calculated potential VOC emissions due to use of HCR-188C1 in household
refrigerators and freezers is equal to about 4x10-6 percent of annual
residential wood combustion emissions.   As these emissions of HCR-188C1
are several orders of magnitude less than other anthropogenic emissions,
including other residential emissions (i.e., residential wood
combustion), the environmental impacts of these VOCs are not considered
a threat.

8.  	REFERENCES

A.S. Trust & Holdings, Inc. 2009.  HCR-188C New Composition.  Follow-up
to the HCR-188C Significant New Alternatives Policy Program Submission
to the United States Environmental Protection Agency.  August 2009.

A.S. Trust & Holdings, Inc.  2007. Significant New Alternatives Policy
Program Submission to the United States Environmental Protection Agency.
June 2007. 

EPA 2008a.  Acute Exposure Guideline Levels: Definitions.  Accessed 27
February 2009.  Available at:
<http://www.epa.gov/opptintr/aegl/pubs/define.htm>.

EPA 2008b.  Volatile Organic Compounds – National Summary of VOC
Emissions.  Last updated 21 October 2008.  Accessed 4 March 2009.
Available at <http://www.epa.gov/air/emissions/voc.htm>.

EPA 1994.  Significant New Alternatives Policy Technical Background
Document:  Risk Screen on the Use of Substitutes for Class I
Ozone-depleting Substances: Refrigeration and Air Conditioning. 
Stratospheric Protection Division.  March, 1994.

	

Forster, P., V. Ramaswamy, P. Artaxo, T. Berntsen, R. Betts, D.W. Fahey,
J. Haywood, J. Lean, D.C. Lowe, G. Myhre, J. Nganga, R. Prinn, G. Raga,
M. Schulz and R. Van Dorland. 2007.  Changes in Atmospheric Constituents
and in Radiative Forcing. In: Climate Change 2007:The Physical Science
Basis. Contribution of Working Group I to the Fourth Assessment Report
of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin,
M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller
(eds.)]. Cambridge University Press, Cambridge, United Kingdom and New
York, NY, USA.

ICF. 1997. Physiological Effects of Alternative Fire Protection Agents -
Hypoxic Atmospheres Conference. Stephanie Skaggs prepared the
proceedings of the conference held May 22, 1997 in New London, CT.

IPCC/TEAP. 2005. Bert Metz, Lambert Kuijpers, Susan Solomon, Stephen O.
Andersen, Ogunlade Davidson, José Pons, David de Jager, Tahl Kestin,
Martin Manning, and Leo Meyer (Eds).  Cambridge University Press, UK. pp
478.

Kataoka.  1999.  “Allowable Charge Limit of Flammable Refrigerants and
Ventilation Requirements.”  Draft Proposal.  O. Kataoka/Daikin/Japan,
June, 1999.

NFPA, 2007.  NFPA Liquified Petroleum Gas Code.  2008 Edition.	

OSHA. 2004.  “Safety and Health Topics: Isobutane.”  February 2004. 
Available online at:
<http://www.osha.gov/dts/chemicalsampling/data/CH_247840.html>.

Sheldon, L.S., et al.  1989. "An Investigation of Infiltration and
Indoor Air Quality."  New York State Energy Research & Development
Authority, Report 90-11.

 OSHA regulation 29 CFR 1910.110 considers ventilation adequate “when
the concentration of the gas in a gas-air mixture does not exceed 25
percent of the lower flammable limit.”

 Twelve percent oxygen in air is the No Observed Adverse Effect Level
(NOAEL) for hypoxia (ICF 1997).

 ICF International maintains the Vintaging Model for EPA in order to
simulate the aggregate impacts of the ODS phaseout on the use and
emissions of various fluorocarbons and their substitutes over a period
of several years across more than 40 different applications.  The model
tracks the use and emissions of various compounds for the annual
vintages of new equipment that enter service in each end-use.  The
vintage of each type of equipment determines such factors as leak rate,
charge size, number of units in operation, and the initial ODS substance
that the equipment contained.    

 During disposal it is assumed that only 90 percent of the refrigerant
charge remains in the unit. 

 Assuming 240 workdays/year = 52 weeks/year x 5 workdays/week – 10
holidays/year.- 10 vacation days

 HCR-188C SNAP application states that less than 100 pounds of HCR-188C
is intended to be produced annually.  It was assumed the same quantity
would be produced of HCR-188C1.  If all of the units produced are
refrigerators of charge 39.6 g a maximum of 1145 units will be produced
annually leading to five events/manufacturing facility/day (assuming
only one production plant is in operation and that there are 240
workdays per year).

 This figure determined using 2002 annual VOC emissions data from EPA
(2008b) and expected annual production levels from A.S. Trust &
Holdings, Inc. (2007).  It was assumed that expected annual production
for HCR-188C1 would be the same as for HCR-188C. 

 This figure determined using 2002 annual VOC emissions data from EPA
(2008b).  Residential wood combustion is the only residential source
included in the EPA (2008b) analysis.

HCR-188C1 Non-CBI Risk Screen

h