November 17, 2011 1 

## Significant New **Alt ernatives Policy Pr** **ogram Refrigeration**  **and Air Conditioning**  **Sector Risk Screen on Substitutes for**  **CFC -**  **12 ,**  **HCFC -**  **22 , and**  **R -**  **502 in**  **Retail Food Refrigeration**  **Substitute: Propane**  **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 two decade s , 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, runs the Significant New Alternatives Policy (SNAP) Program , which identifies acceptable and unacceptable substitutes for ODS in specific end
-uses based on assessment of their health and environmental impacts. 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
-use applications within all of the major ODS
-using sectors, including : refrig eration 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 docke t. The purpose of this risk screen 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 , HCFC
- 22 and R
- 502 in this sector. The proposed end
-use application considered in this analysis is retail food refrigeration , specifically ice cream cabinets . The specific proposed CFC
- 12 , HCFC
- 22 and R
- 502 substitute examined in this repo rt is propane (R
- 290). The substitute would only be used in new equipment, not in retrofitted equipment. The Background Document examines the potential risks associated with use of substitutes in retail food refrigeration , and includes a detailed discussion of the methodologies used to conduct this risk screen. Occupational exposure modeling was performed to ensure that use of the proposed substitute in the application listed above did not pose unacceptable risk to workers during equip ment manufacture
. Modeling was p erformed at the end
-use to ensure that potential catastrophic releases of the substitute did not pose unacceptable risk to store employees and customers in locations where the ice cream cabinets are in use . Lastly, general population exposure modeling was performed to ensure that the proposed substitute would not pose an unacceptable risk to the population at large. The proposed substitute, propane, may contain minute quantities of impurities. Table 1 details the compos ition of the proposed substitute, including the maximum estimated concentration of impurities that may be present.November 17, 2011 2 **Table 1**  **. Composition of the**  **Proposed Substitute**  **Component Concentration**  **Substitute Percent by Weight**  Propane  99.5 % **Potential Impurities Maximum Concentration (ppm v/v)**  Ethane 1700 Propylene 300 n - Butane 1000 Sulfur 1 Water 12 Section 2 summarizes the results of the risk screen for the proposed substitute. The remainder of the risk screen is organized into the following sections:

 Section 3: Atmospheric Assessment  Section 4: Discussion of End
- Use Scenario s Modeled  Section 5 : Flammability Assessment  Section 6 : Asphyxiation Assessment  Section 7 : Toxicity Assessment  Section 8 : Volatile Organic Compound Assessment  Section 9 : References 

### 2. **SUMMARY OF RESULTS** Propane is recommended for SNAP approval for retail ice cream cabinets. EPA's risk screen indicates that the use of the proposed substitute will be less harmful to the atmosphere than the continued use of CFC
- 12 , HCFC
- 22 and R
- 502 . No significant toxicity risks to workers, consumers, or the general population are expected according to occupational and end
-use exposure modeling. Flammability models indicate that risks of explosions are not a concern for store employees or customers . To further protect against the limited risk of explosion, it is recommended that the cabinets not be used in small, poorly ventilated spaces (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) St andards 15 1 , 34 2 and 62 3 be followed.

1 Safety Standard for Refrigeration Systems ASHRAE Standard 15 establishes safeguards for life, limb, health, and property and prescribe s safety requirements. 2 Designation and Safety Classification of Refrigerants ASHRAE Standard 34 is establishes a uniform system for assigning reference numbers, safety classifications, and refrigerant concentration limits to refrigerants. Safety classif ications based on toxicity and flammability data are included. 3 Ventilation for Acceptable Indoor Air Quality ASHRAE Standard 62 establishes minimum ventilation rates and other measures intended to provide indoor air quality that is acceptable to human oc cupants and that minimizes adverse health effects.November 17, 2011 3 

### 3. **ATMOSPHERIC ASSESSMENT**  This section presents an assessment of the potential risks to atmospheric integrity posed by the use of propane in the retail food refrigeration sector. The ozone depletion potential ( ODP ) , global warming potential ( GWP ) , and atmospheric lifetime (ALT) of the proposed substitute are presented in Table 2. The environmental impacts resulting from use of prop ane 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 when compared to CFC
- 12 , HCFC
- 22 and R
- 502
. **Table 2**  **. Atmospheric Impacts of Propane**  **Compared to CF**  **C -**  **12 ,**  **HCFC -**  **22 and**  **R -**  **502 Refrigerant**  **ODP GWP**  **ALT** Propane 0 a 3.3 a 0.041 b CFC - 12 1 c 10,900 a 100 a HCFC - 22 0.055 c 1,810 a 12 a R - 502 d 0.33 c 4650 NA NA = Not Available a IPCC 4 th Assessmen t Report (Forster et al. 2007)
. b IPCC/TEAP (2005)
. Atmospheric lifetime not provided in SNAP submission. c Montreal Protocol and a vailable at: http://www.epa.gov/ozone/ods.html
. d R- 502 is a blend consisting of CFC - 115 (51%) and HCFC - 22 (49%). The ODP and GWP presented for this blend were calculated using values from http://www.epa.gov/ozone/ods.html ( Montreal Protocol) and IPCC 4 th As sessment Report (Forster et al. 2007), respectively. Alternatively, WMO (2006) has estimated the ODP for CFC - 115 to be 0.44 based on recent atmospheric modeling (rather than 0.6, as previously agreed by the Parties to the Montreal Protocol). Using the more current estimate of ODP would bring the overall ODP for R - 502 to 0.24. 

### 4. **DISCUSSION OF END -**  **USE SCENARIO S**  **MODELED** The proposed use of this substitute is in ice cream cabinets which could reasonably be expected to be located either in the main area of a store, or in a storage room. Because a storage room could be much smaller than the main area of a store, a reasonabl e worst - case scenario analysis was performed to model catastrophic release of the refrigerant in a storage room
. For the analysis, a storage room with a floor area of 14 m2 and a height of 3 meters was assumed. 4 This is equivalent to a room volume of 42 m3

. In the analysis, the full charge 5 of the unit is assumed to be emitted over the course of one minute and t he model conservatively assumes 2.5 air exchanges occur per hour
. Horizontal stratification is also assumed since propane is 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 refri gerant 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). Table 3 details the assumptions used in the models.

4 This room was considered a ‘high risk room’ due to its small size and poor ventilation. (Ben and Jerry’s/Unilever 2008) 5 Al l models in this risk screen conservatively assume that all retail ice cream cabinets are charged with 150g of propane. The submitter notes that the cabinets will have a charge size of about 90g , but that the maximum charge size will be 150g (Ben and Jerry’s/Unilever 2008 ). To ensure all models address a reasonable “worst - case” scenario, the maximum charge size was chosen for use in the models.November 17, 2011 4 **Table 3. Worst -**  **Case Scenario Model Assumptions Parameter**  **Scenario 1** Refrigeration Unit Ice Cream Cabinet Room Storage Room Charge size (g) 150 % of charge emitted 100 Length of release (minutes) 1 Room size (volume - m 3 ) 42 Room ventilation (air exchanges per hour) 2.5 Horizontal stratification Yes 

### 5. **FLAMMABILITY ASSESSMENT**  Propane is flammable when its concentration in air is in the range of 2.1%
- 9.5% by volume (this is equal to 21,000 ppm to 95,000 ppm). 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 o f propane is within these flammability limits
. The remainder of this section addresses the potential for flammability risks at the end
-use, and during manufacture an d servicing and provides a discussion of measures to be taken to ensure safe use
. Under the assumptions outlined under the catastrophic release scenario (see Section 4) 6 , the maximum instantaneous concentration of propane in the lower stratum of the room would be approximately 66 percent o f its lower flammability limit ( LFL ) , as shown in Table 4 . T he maximum instantaneous concentration is even lower in the upper stratum of the room, as only five percent of the leaked refrigerant is present in this stratum, and this stratum has a greater volume than the lower stratum
. **Table 4**  **. Flammability Assessment Room Type/**  **Appliance Type Reasonable Worst**  **- Case**  **Scenario Flammability Threshold**  **Scenario**

**Room Size (m 3**  **) Maximum** 

**Instantaneous Concentration**  **(ppm)** a ,b **Room Size Causing** 

**Flammability Risk (m**  **3 )**  **Maximum**

**Instantaneous Concentration**  **(ppm)** a ,b Storage Room/ Ice Cream Cabinet 42 (1,483 ft 3 ) 13,780 28.5 (1,006.5 ft 3 ) 20,308
a Lower Flammability Limit of propane is equal to 21,000 ppm b Values provided in these columns refer to the concentration in the lower stratum of the room. For flammability to be of concern under the conservative (protective) assumptions described above, the volume of the storage room would have to be 28.5 m3 ( 1,006.5 ft 3 ) (See Table 4) ; a ssuming a square room with a ceiling height of 3 m ( 9.8 ft), the storage room floor area would be less than 3.1 x 3.1 m (10.1 x 10.1 ft)
. Although these dimensions equate to a very small space, since storage rooms can be of varying size and because boxes and other equipment in the room may reduce the effective volume of the room, it is recommended that propane cabinets not be installed in small, poorly ventilated spaces, to avoid the risk of fire and explosion. However, for average - sized rooms the risk of explosion is minimal. Creating a hole in the bottom of storage room doors (to act as a vent and increase air circulation) and installing leak prevention devices will further protect against the limited risk of explosion. For example, in commercial refrigeration end
-uses, refrigerant leak prevention systems can be used to capture leaked

6 The submitter notes that “catastrophic leaks during operation have not been recorded.” (Ben and Jerry’s/Unilever 2008)November 17, 2011 5 refrigerant in a receiving tank during over pressure events, rather than venting th e refrigerant to the atmosphere (McKeown 1993). 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 propane . The submitter has provided information regarding their training program for service technicians . The program includes detailed information covering important topics such as potential ignition sources, proper tools to use with flammable refrigerants, safe workplace behavior and service procedures
. At the end of the training , technicians must pass a multiple choice assessment (Ben and Jerry’s/Unile ver 2008)
. A ll technicians who will be servicing cabinets using propane should receive this training and be required to pass the assessment . As a further precaution, propane storage and transport equipment should be installed with safety devices that minimize the likelihood of catastrophic releases. For example, NFPA 58 Liqu e fied Petroleum Gas C ode (NFPA 200 8 ) requires the use of overfill protection devices (OPD) on cylinders to minimize the likelihood of leaks. The NPFA 58 Code also contains storage and transportation requirements/guidelines. Similar equipment safety and procedural requirements should be implemented for this substitute
. It is important that the strictest standards be followed during the manufacture of these i ce cream cabinets
. Itis recommended that refrigerants be properly stored and caution used within manufacturing facilities to minimize explosion risk and that worker s 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 propane through adherence to g ood manufacturing p ra ctices . If refrigerant levels in the air surrounding the equipment rise above one
- fourth of the lower flammability limit7 , the space should be evacuated and re
- entry should only occur after the space has been properly ventilated. 

### V entilation is also of th e utmost importance to mitigate the risk of fire or explosion when servicing equipment using propane . During servicing operations, technicians should ensure that proper ventilation is in place through the use of fans (or other mechanical ventilation devic es) and portable refrigerant detectors should be used to alert technicians to the presence of flammable gases in the area. 

### 6. **ASPHYXIATION ASSESSMENT**  The risk of asphyxiation for a reasonable “worst
- case” scenario was investigated f or propane . This analysis considers the modeling assumptions outlined in Section 4
. This analysis does not consider additional ventilation conditions ( such as open doors or windows, fans operating, conditioned airflow, or seepage between the door and door frame ) that are likely to occur and would further reduce the exposure concentration of propane . If the proposed substitute passes the screening analysis with these restrictive assumptions in place, it can be reasonably assumed that no risks of asphyxiation will be present under real
-world conditions
. The results of the asphyxiation assessment are summariz ed in Table 5 be low
. T he maximum charge of propane necessary to reduce the oxygen levels to 1 2 percent in air 8 in a storage room of volume 42 m3 ( 1,483 ft 3 ) was calculated, assuming horizontal stratification of the refrigerant and the air. Horizontal stratification is assumed since propane is 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 propane , and that the pressure of the room does not increase significantly

7 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.” 8 Twelve percent oxygen in air is the NOAEL for hypoxia (ICF 1997).November 17, 2011 6 with the addition of the refrigerant, a charge of approximately 904 g would be necessary to reach 12 percent oxygen in the lower stratum. This amount represents more than six times the maximum intended charge size, 1 5 0 g , of a single propane ice cream cabinet. Charge requirements to reach the same effect in the upper stratum would be even higher because of the stratum’s larger volume
. **Table 5**  **. Asphyxiation Assessment Room Type**  **/ Appliance Type**  **Reasonable Worst -**  **Case Scenario**  **Asphyxiation Threshold Scenario**

**Room Size (m 3**  **) Charge Causing** 

**Impairment (g) a**  **Room Size Causing** 

**Impairment (m**  **3 )**  **Assumed Leak Size (g)**  **a** Storage Room / Ice Cream Cabinet 42 (1,483 ft 3 ) 904 6.96 (245.8 ft 3 ) 15 0
a Values provided in these columns refer to the charge required to cause impairment in the lower stratum of the room. In this s cenario, 100% of the charge leaks. Charge requirements to reach the same effect in the upper strata would be even higher because of the stratum’s larger volume. For asphyxiation to be of concern with the proposed charge size under the conservative (protective) assumptions described above, the volume of the storag e room would have to b e approximately 6.96 m3 ( 245.8 ft 3 ) , which is significantly smaller than the 42 m3 sized room assumed in the worst case scenario (see Section 4). Further, as the “threshold” room sizes for asphyxiation risks are smaller than those for flammability risks, flammability risks would be realized before asp hyxiation risks. Therefore, EPA does not believe that the use of propane in this end
-use poses a significant risk of asphyxiation or impaired coordination to room occupants under the proposed end
-use. Based on the results discussed above, EPA does not be lieve that the use of propane in this end
-use poses a significant risk of asphyxiation or impaired coordination to store employees or customers
. 

### 7. **TOXICITY ASSESSMENT** Section 7 summarizes the results of the toxicity assessment for propane in the retail refrigeration sector. This section is organized as follows:
 Section 7.1: Toxicity Reference Values  Section 7.2: Occupational Exposure  Section 7.3: End
-Use Exposure  Section 7.4: General Population Exposure **7 .1**  **TOXICITY REFERENCE VALUES** To as sess potential health risks from exposure to this substitute in th e retail food refrigeration sector, EPA identified the relevant toxicity threshold values for comparison to modeled exposure concentrations for different scenarios. For the occupational exp osure 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 or ten -ho ur 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 Table 6
. B ecause 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. Table 6 lists the relevant toxicity limits. Table 7 provides definitions for acronyms used in Table 6
. EPA’s approach for identifying or developing these values is discussed in Chapter 3 of the Background Document.November 17, 2011 7 **Table 6**  **. Toxicity Levels of Propane**  **and Potential Impurities Long**  **- term Exposure**  **ppm Short**  **- term Exposure**  **ppm Reference**  **Concentration (RfC)**  **mg/m 3**  **Substitute** Propane 1000 a (OSHA PEL/NIOSH REL) 10,000 b , c (10 minute AEGL - 1) 0.9 d 6,900 b (30 minute AEGL - 1 ) **Potential Impurities** Ethane NAe NAe NA Propylene NA f NA f NA n - Butane 800 g (NIOSH REL) NA 0. 95 d Sulfur NA NA NA NA = Not Available a http://www.cdc.gov/Niosh/npg/npgd0524.html b http://www.epa.gov/oppt/aegl/pubs/results96.htm c "An IDLH of 2,100 ppm has been established for propane. However, NIOSH (1996) states that "[b]ased on acute inhalation toxicity data in humans (ACGIH 1991; Braker 1980), a value much greater than 10,000 ppm would have been appropriate. However, the revised IDLH for propane is 2,100 ppm based strictly on safety considerations (i.e., being 10% of the lower explosive limit of 2.1%)." Therefore, as this IDLH value is based on flammability concerns and not toxicity concerns, it is not used in the evaluation of toxicity risks in this risk screen. d SNAP Refrigerant Background Document (EPA 1994). e Ethane is a "simple asphyxiant." http://www.osha.gov/dts/chemicalsampling/data/CH_238900.html f Propylene is a "simple asphyxiant." http://www.osha.gov/dts/chemicalsampling/data/CH_264442.html g http://www.cdc.gov/niosh/npg/npgd0068.html

**Table 7**  **. Explanation of Toxicity -**  **Related Acronyms a**  **Organization Definition**  OSHA Occupational Safety and Health Administration NIOSH National Institute for Occupational Safety and Health **Exposure Limit**  **Definition Explanation** 

AEGL - 1 Acute Exposure Guideline Level 1 The AEGL - 1 “is the airborne concentration, expressed as parts per million or milligrams per cubic meter (ppm or mg/m3) of a substance above which it is predicted that the general population, including susceptible individuals, could experience notab le discomfort, irritation, or certain asymptomatic nonsensory effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure.” “Airborne concentrations below the AEGL - 1 represent exposure levels that can produc e mild and progressively increasing but transient and nondisabling odor, taste, and sensory irritation or certain asymptomatic, nonsensory effects.” b 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. PEL Permissible Exposure Limit This is an 8 - hour time -weighted average exposure limit set by OSHA. REL Recommended Exposure Li mit 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.” aAll information in this table taken from EPA (1994)
. b http://www.epa.gov/oppt/aegl/pubs/define.htmNovember 17, 2011 8 **7 .2**  **OCCUPATIONAL EXPOSURE** Occupational exposure modeling was performed for the proposed substitute to ensure that use of the substitute 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. A box
- model approach was used to evaluate potential worker exposure to alternati ve refrigerants. This approach 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 (NIOSH) . This mode l 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 were obtained from the Vintaging Model. 9 T he 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. 10 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 ye ar divided by 365 workdays per year. For the purposes of this model, it is assumed that propane will have a market penetration rate of 23 % 11 and that one production facility will be in operati on. These assumptions provided by the submitter result in approximately 274 events/manufacturing facility/workday
. For disposal, it was conservatively assumed that 1 unit is disposed during an 8
-hour work day nationwide
. The maximum time weighted average (TWA) exposure was estimated for each exposure scenari o, and this value compared to the Workplace Guidance Levels (WGLs) for propane and the potential impurities in the substitute
. The modeling results indicate that the short
-term (15
- minute and 30
- minute) and long
term (8
-hour) worker exposure concentrations are , at a maximum, about 50 percent of the WGLs. Table 8 displays the maximum estimated 15
- minute TWA occupational exposure level s of propane and the potential impurities in the substitute
. The maximum estimated 15
-minute TWA occupational exposure levels are the most conservative of the modeled results and indicate the highest predicted exposure concentrations of the short
- term (15
- minute and 30
- minute) and long
-term (8
-hour) exposure scenarios. Even the maximum estimated short
-term occupational level s for propane and the potential impurities are significantly lower than the ir 8
-hour or 10
-hour long
-term WGL s . T herefore , occupational exposure to the substitute is not considered a toxicity threat.

9 ICF Internati onal 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. Th e model tracks the use and emissions of various compounds for the annual vintages of ne w 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. 10 During disposal it is assumed that only 90 percent of the refrigerant charge remains in the unit. 11 This number conservatively assumes that all Unilever cabinets in North America (a figure p rovided in the SNAP Submission) are in the US and that all will be replaced with propane cabinets by 2010. This number of cabinets was divided by the number of predicted new small retail refrigeration units produced in 2010, from the Vintaging Model
.November 17, 2011 9 **Table 8**  **. Occupational Risk Assessment Maximum 15**  **- minute TWA**  **Occupational Exposure Levels**

**(ppm) Workplace** 

**Guidance Levels (ppm)**  a **Workplace Guidance Levels**

**Time Period Substitute**  Propane 502 1000 10 - hour TWA b **Potential Impurities**  Ethane 0.9 NA NA Propylene 0.2 NA NA n - Butane 0.5 800 10 - hour TWA Sulfur 5.4 x 10 - 4 NA NA NA = Not Available a See Table 5 for m o re information. b The WGL for Propane is set as a 1000 ppm 8 - hr TWA by OSHA and a 10 - hr TWA by NIOSH. **7 .3**  **END -**  **USE EXPOSURE**  This section presents estimates of potential store employee and customer exposures to propane in ice cream cabinets
. An exposure analysis was performed to examine potential catastrophic release of the substitute in a small storage room (as in Sections 

### 5 and 

### 6 ) under a reasonable “worst
- case” scenario
. The analysis was undertaken to determine the 15
- and 30
- minute TWA exposure s for the substitute , which were then compared to the standard toxicity limits presented in Table 6 to assess the risk to consumers
. However, the TWA values are fairly c onservative 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 model involves a refrigerant leak from an ice cream c abinet into an enclosed storage room of volume 42 m3 (1,483 ft 3 ) (see Section 4)
. The model assume s 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 refrigerant to 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). Exposure concentrations were calculated using the box model described in the Background Document, which was adapted to estimate concentrations on a minute
-by
- minute basis. In the analysis, the full charge of the unit is assumed to be emitted over the course of one minute and t he model conservatively assumes 2.5 air exchanges occur per hour
. The highest expected levels of exposure at the end
-use based on this analysis occur in the lower stratum of the room. The results of the assessment are presented in Table 9
.November 17, 2011 10 **Table 9**  **. End** **- Use**  **Exposure Assessment**

**15 -**  **minute TWA Exposure (ppm)**  **30 -**  **minute TWA**

**Exposure (ppm) Substitute**  Propane 10,41 4 7,96 3

**Potential Impurities**  Ethane 19 1 5 Propylene 3. 4 2. 6 n - Butane 11 8.6 Sulfur 0.01 0.00 9 TWA = Time Weighted Average The 15
- minute TWA Exposure for propane estimated for this risk screen is 10,414 ppm , which exceeds the AEGL
- 1 value by 414 ppm. Although the calculated end
-use exposure is marginally greater than the recommended exposure limit, toxicity is not a concern for multiple reasons. First, the AEGL
- 1 exposure limit marks the 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. ” 12 Specifically, i f the 15
-minute TWA w ere to reach or exceed the AEGL
- 1, certain irritation or notable discomfort would be experienced, but symptoms would be alleviated upon leaving the affected area and no permanent damage would be sustained. Second, due to the conservative assumptio ns used in the models, it is unlikely that this worst
- case scenario would occur. The two main assumptions used in the End
-Use Exposure Assessment (see Section 4) included room size and ventilation rate. In Section 4, the most conservative , yet reasonable, values were chosen for each category. Adjusting either of these assumptions to a value that is slightly less conservative removes the modeled toxicity threat for propane exposure. In particular, the model ing used in the risk screen assumes a leak occurs in the storage room of a convenience store with an area of 14 m 2 (volume of 42 m3 ). This area is considerably smaller than the total area of a typical convenience store , which have sales area s of 100
- 300 m2 (Armines 2008). If the minimum storage room area is i ncreased to 1 5 m2 (volume of 45 m3 ), the exposure becomes 9,719 ppm. The exposure model also conservatively assumed a ventilation rate of 2.5 ACH. The average ventilation rate for a typical convenience store in the U.S. is 1.9 ACH
. 13 Although this rate is lower than the assumed rate for a storage room within a convenience store, the use of exhaust fans and door ventilators in the storage rooms of convenience stores significantly increases th e air exchange rate. In addition, Occupation al Safety & Health Administration (OSHA) requires that any storage room containing flammable material must have a ventilation system “designed to provide for a complete change of air within the room at least six times per hour.” 14 Though this storage room will only contain a small amount of propane, higher ventilation rates would further protect against flammability and toxicity concerns. If ventilation was increased in the storage room to 4.5 ACH, the 15
- min TWA would be 8,458 ppm. Further, as described above, the box
- model approach used in this modeling assumes that 95% of the refrigerant leaks evenly into the bottom 0.4 meter of the room, while the remaining 5% of refrigerant mixes evenly in the top breathing zone portion of the room. Once the refrigera nt disperses throughout the
12 http://www.epa.gov/oppt/aegl/pubs/define.htm 13 A sample of 70 small commercial buildings were tested in Florida for ventilation rate under normal building o peration and uncontrolled air flow . http://www.fsec.ucf.edu/en/publications/html/FSEC
- CR
- 1672
- 97/ 14 http://www.osha.gov/pls/oshaweb/owadisp.show _document?p_id=9752&p_table=STANDARDSNovember 17, 2011 11 entire room, exposure will be minimized. Because the ACH and room volume assumptions used in the models are both very conservative, it is unlikely that these conditions would simultaneously exist and therefore the risk of exceeding the toxicity thre shold is extremely small . It is strongly recommended , however, that s teps to protect against toxicity threat in the space should be taken, as detailed in Section 5 , such as ensuring there is adequate ventilation in rooms containing propane ice cream freezers. Finally, e xposure to the minute quantities of the impurities in the formulation (see Table 9 ) is also not expected to pose a toxicity threat, given the low toxicity of these substances. Should catastrophic release from a cabinet located in the main area of a store occur, exposure levels are not expected to pose a toxicity threat as the room volumes in the store would be larger than those used in this model
. 15 Thus, exposure concentrations would be even lower in the main area of the store. **7 .4**  **GENERAL POPULATION EXPOSURE** In the Background D ocument , the RfC value f or propane is 0.9 mg/m3

. This value was compared to estimated factory releases and on
- site releases , resulting in a ratio of exposure concentration to RfC that varies betwee n 1
. 9 x 10 - 4 to 3.5 x 10 - 1 , depending on the type of release scenario. 16 Ratios of exposure concentration to RfC for the proposed substitute’s impurities (for which RfCs are available) were even lower. Since the exposure concentrations for the substance s are lower than the RfC value s , the proposed substitute is not expected to pose a toxicity threat to the general population. 

### 8. **VOLATILE ORGANIC COMPOUND (VOC) ASSESSMENT**  Propane ha s not been exempt ed as a VOC under the CAA ( 40 CFR 51.000)
. VOC emissions from the production of retail ice cream cabinets using propane as a refrigerant are controlled through standard industry practices, and as such, emissions from the manufacture of uni ts are likely to be minimal
. For units in operation for retail applications, u sing leak estimates from the Vintaging Model, the annual release rate ( including operating, servicing, and disposal leak rates ) was calculated to be approximately 10 % of the refrigerant charge size
. 17 Assuming this r elease rate, two assessment s were performed to compare the annual VOC emissions from the use of propane in self
- contained reach
- in freezers to other anthropogenic sources of VOC emissions. 18 The first assessment approximates the annual VOC emissions that would be emitted from the use of propane in all Unilever/Ben and Jerry’s U.S. retail ice cream cabinets. 19 The second assessment approximates the annual VOC emissions if all reach
- in freezers in the U.S. were charged with propane.

15 An Armines (2008) study presents data from site visits to California convenience stores, “minimarkets” and supermarkets during which the minimum store area encountered was 1 00 m 2 . Assuming a 3 m ceiling height (as in the scenarios used in this risk screen), this is equal to a volume of 300 m3 , or more than seven times the volume of the store room used in this analysis. 16 Release scenarios include factory and on
- site release s, with and without recycling of the refrigerant. 17 The average annual leak rate (6%), annual service rate (2%) and EOL disposal rate (35%) for small retail refrigeration equipment was approximated using data from the Vintaging Model (v4.4_3.23.11). Using an average lifetime of 20 years for small retail refrigeration equipment, a total annual release rate of 10% was determined. 18 This scenario conservatively assumes that there is immediate market saturation in 2010, and does not consider commercialization and initial market uptake delays. 19 The n umber of cabinets is calculated based on the conservative assumption that all Unilever/Ben and Jerry’s cabinets in North America (a figure provided in the SNAP Submission) are located within the U.S.November 17, 2011 12 **Table 10**  **. VOC Annual Emissions Analysis**  **Set of Sources Assessed Annual**  **Propane VOC Emissions**  **Compared to VOC Emissions from**  **All Anthropogenic Sources a**  **(%)** All Unilever/Ben and Jerry’s U.S. Propane Retail Ice Cream Cabinets 7.5 x10 - 7 % All U.S. Self

- contained Reach - in Freezers b 1.3x10 - 4 % a B ased on 2010 projections calculated using 2008 EPA annual VOC e missions data (EPA 2009 ) and ICF assumptions
. b Calculations based on 2011 Buildings Energy Data Book (DOE 2011) , Energy Savings Potential and R&D Opportunities for Commercial Refrigeration ( DOE 2009), and ICF assumptions
. As illustrated in Table 10, emissions from the use of propane under both scenarios are minimal compared to other sources of VOC emissions. Assuming all Unilever/Ben and Jerry ’s ice cream cabinets in the U.S. were charged with propane, the resulting VOC emissions in one year would b e equal to approximately 8.5 x10 - 2 percent of the VOC emissions caused by the generation of electricity used to power small retail food refrigeration equipment , 20 1
. 2x10 - 3 percent of all the VOC emissions caused by the generation of electricity for all r ef

rigeration and air conditioning applications , 21 or 7
. 5 x10 - 7 p ercent of all annual anthropogenic VOC emissions in the U.S. Moreover, if all reach
- in freezers in the U.S. were charged with propane (the second, more conservative scenario), the resulting VOC emissions would be equal to approximately 1.3x10 - 4 percent of all annual anthropogenic VOC emissions in the U.S. Because these emissions of propane are several orders of ma gnitude lower than the VOC emissions generated by other anthropogenic emissions, and the VOC emissions from all Unilever/Ben and Jerry’s ice cream cabinets is only a small fraction of VOC emissions from the use of electricity in the retail refrigeration sector , the e nvironmental impacts of the incremental VOC emission s from propane releases for small refrigeration cabinets are not considered a threat to local air quality
.

20 This figure includes c ommercial reach
- in cabinets that are upright, self
- contained refrigerated cases with solid or glass doors w

hose purpose is to hold frozen and/or refrigerated food products. These cases are commonly used in commercial and institutional food
- servic e establishments. The cases are self
- contained such that the entire refrigeration system is built into the reach
- in unit and heat is rejected to the surrounding interior air. 21 Calculations based on ICF assumptions and 2010 Electric ity Projections (U.S. EI A 2011).November 17, 2011 13 

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