If the lifetime of a chemical is short compared to the lifetime of the reference gas, the GWP of the chemical declines as the period of integration increases.  If the lifetime of the chemical is long compared to the lifetime of the reference gas, the GWP of the chemical rises as the period of integration increases.

      	In practice a high GWP does not necessarily mean a large impact on warming.  If chemicals are never emitted they cannot cause a direct contribution to global warming even if they have high GWPs.  For example, if good service practices are in place, emissions from hermetically sealed household refrigerators are very small.  If the material is recovered for recycling or destruction after the useful life of the equipment, the refrigerant is never released to affect the atmosphere.  In contrast, mobile air conditioners tend to be leaky.  Substitutes used in this end use are more likely to be released to the atmosphere and, thus, impact global warming.

4.7.4	Indirect Effects from Changes in Energy Efficiency

      In addition to direct and indirect atmospheric effects, ODS substitutes may also have indirect energy effects that can influence global warming.  Use of alternative chemicals may change the energy efficiency of equipment and products currently using CFCs.  Because most energy is derived from burning fossil fuels, changes in energy efficiency may result in changes in carbon dioxide, nitrous oxide, and methane emissions, which will impact radiative forcing and global warming.  The two major end use categories in which the use of alternatives can impact the energy efficiency of equipment or products are refrigeration and air conditioning applications and foam insulation applications.  The key factors affecting energy efficiency for each of these applications are discussed below.

<IP_ADDRESS>		Refrigeration and Air Conditioning End Uses

      Refrigeration and air conditioning equipment can consume significant quantities of energy during normal operation.  Whether used in new or existing equipment, a new refrigerant can impact both the energy efficiency and cooling capacity of the refrigeration system.  The specific factors that impact the potential change in energy consumption associated with the use of a new refrigerant are as follows:

      	Thermodynamic Properties of the Alternative Refrigerant:  The thermodynamic properties of the refrigerant affect the amount of energy used by the compressor.  This is because these properties determine the evaporating and condensing pressures at which the equipment can operate given the temperature requirements of the application.  In practice, the greater the pressure difference between the evaporator and the condenser, the more the compressor must work to achieve a given cooling capacity.

      	Design of Equipment Components:  New refrigeration equipment is always designed around the refrigerant to be used.  System components such as the condenser, evaporator, or other heat exchangers are selected to minimize the work that a refrigeration system needs to do given a particular refrigerant.  For example, switching from a CFC to an alternative refrigerant might require a different type of heat exchanger tubing in the evaporator to enhance heat transfer or different sized expansion devices to better control the amount of refrigerant metered to the evaporator.

      	Retrofit Optimization:  The use of an alternative refrigerant in existing equipment (retrofits) often results in a decrease in the energy efficiency or refrigerating capacity of the equipment.  This is because the equipment was originally designed to operate most efficiently given the thermodynamic properties of the CFC refrigerant.  A number of steps can be taken to alter existing equipment so that it operates more efficiently with a given alternative.  Such steps include changing the motor drive train, increasing the motor speed, changing the heat exchangers, and replacing the impeller (for chillers).  The gains in energy efficiency associated with such measures must be weighed against cost and possible impact on refrigeration capacity.

      A widely used measure for the energy efficiency of refrigeration equipment is the coefficient of performance (COP).  This is defined as the total amount of refrigeration delivered by the equipment divided by the total amount of energy (i.e., work) input into the system.  The COP can be calculated for an ideal cycle.  The COP for an actual piece of equipment can be measured through field testing of the actual energy input and refrigerating effect of the equipment.  Field measurements of COP may vary from the ideal COP because of energy losses not accounted for in the model, or variations from the ideal cycle caused by friction losses or pressure drops.

      Finally, it is important to note that actual changes in energy efficiency are equipment and application specific.  As a result, it can be difficult to generalize about the potential impacts of a given substitute on energy efficiency in a given refrigeration or air conditioning application.

<IP_ADDRESS>		Foam Insulation

      Several factors combine to limit heat flow in thermal insulating foams including the volume fraction of the solid phase; the cell size which suppresses convection and radiation through cell walls; and the conductivity of the enclosed cell gases.  In addition to the conductivity per unit volume of the foam, the foam thickness also affects the thermal insulating capacity of foam products.

      CFCs were highly suitable as blowing agents in part because their low thermal conductivity contributed to the insulating capacity of the foam product.  Substitute blowing agents with higher thermal conductivity contribute less.  Higher thermal conductivity of the substitute blowing agent, however, does not necessarily translate into lower energy efficiency in foam products if formulation or thickness changes are made to compensate for the relative change in substitute blowing agents.

	CHAPTER 4 REFERENCES

Isaksen, I.S.A.  1986.  Ozone Perturbation Studies in a Two Dimensional Model with Temperature 	Feedbacks in the Stratosphere Included.  Presented at the UNEP Workshop on the Control of Chlorofluorocarbons, Leesburg, Virginia.  September 1986.

National Aeronautics and Space Administration (NASA).  1989.  An Assessment Model for 	Atmospheric Composition.  National Aeronautics and Space Administration Conference Publication 3023.

U.S. EPA.  1992.  Regulatory Impact Analysis: Compliance with Section 604 of the Clean Air Act 	for the Phaseout of Ozone Depleting Substances, Appendix A.  Office of Air and Radiation.  March 12, 1992.

U.S. EPA.  1987.  Assessing the Risks of Trace Gases that Can Modify the Stratosphere.  Office of 	Air and Radiation.  December 1987.

	5.  OCCUPATIONAL EXPOSURE AND HAZARD ANALYSIS

5.1	INTRODUCTION

      This section presents an analysis of potential occupational exposures to alternative refrigerant materials during the manufacture, installation, repair, and disposal of refrigeration equipment in several end-use sectors.  Evaluation of potential occupational exposures to these materials was based primarily on the use of a modelling approach that is similar to the approach used by EPA in their previous analyses of potential occupational exposure to refrigerant vapors (EPA 1990).  Where possible, the results obtained from the model were compared to available worker exposure data to determine the direction and magnitude of any uncertainty resulting from assumptions used in the model.  The following discussion describes the model used to evaluate potential occupational exposures to alternative refrigerants; this is followed by a discussion of the results obtained.

5.2	DESCRIPTION OF THE MODEL

      Occupational exposure to a gas or vapor is the result of two events:  a release of the material to the air and the presence of a worker within the contaminated space.  The duration and magnitude of the resulting exposure is influenced by (1) the duration and intensity of the release, (2) the rate at which contaminated air is diluted with uncontaminated air in the space affected by the release, (3) the proximity of the worker to the source of the release, and (4) the length of time that the worker remains in the space affected by the release.

      The first two factors are addressed directly by the mathematics of the "box" model used in this analysis.  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 (NIOSH 1973).  Starting with a fundamental material balance, assuming that contaminated air is diluted with uncontaminated air:

	Rate of Accumulation = Rate of Generation - Rate of Removal

	Where:
            C = Concentration of gas or vapor at time t
            G = Rate of generation of the contaminant (cubic feet per minute (cfm))
            Q'= Effective rate of ventilation that is
                    corrected for incomplete mixing (cfm)
            V = Volume of room or enclosure (ft[3])

Converting units and rearranging the equation yields the mass balance equation

      Where:

            	V = Room Volume (m[3])
            	Ci = Indoor Concentration (g/m[3])
			S = Source Generation Rate (g/hr)
            	rt = Residence Time of the indoor air (hr)
            	m = Mixing Factor (dimensionless)
            	Co = Outdoor Concentration (g/m[3])

      The integrated form of this equation can be used to calculate the average concentration of a contaminant in a room during the release of a chemical substance:

      Where:

            	Cb = Concentration already existing in the room when 				the emission starts (i.e., at time = 0)

      Assuming that the concentration of contaminant at time = 0 is zero (i.e., Cb = 0), that contaminated air is diluted with uncontaminated air (i.e., Co = 0), and that the concentration has reached a steady-state (equilibrium) level, the integrated equation above can be further simplified:

A dimension analysis reveals that:

      Since it is customary to measure occupational exposures to gasses and vapors in units of parts per million, the equation above can be modified to:

where MW is the molecular weight of the contaminant.

      Because the residence time r is the inverse of the air exchange rate in air changes per hour (ACH), the following can be derived, which is the working equation used to estimate worker exposure to alternative refrigerants:

      However, as described above, the degree to which a worker is exposed to a gas or vapor also depends on the location of the worker at the time the contaminant is released.  To address this aspect, the use of the box model was modified to recognize the fact that workers move around an area where a release occurs.  Specifically, the workspace was divided into four areas or zones.  These zones are defined as follows:

      	Zone 1 represents a space measuring 3' x 3' x 3' centered around an emission source.  A worker is said to be in Zone 1 whenever his/her breathing zone is within 18 inches of the emission source.  Thus, this zone represents an area occupied by a worker performing operations within an arm's reach of the emission source;

      	Zone 2 represents a space measuring 12' x 12' x 12' centered around an emission source.  A worker is said to be in Zone 2 while working within 6 feet of the source;

      	Zone 3 represents a space measuring 30' x 30' x 30' centered around an emission source.  A worker is considered to be in Zone 3 while working within 15 feet of the emission source; and

      	Zone 4 represents a space sufficiently far from the emission source that no measurable exposure occurs.

Thus, refrigerant vapor concentrations will be highest in Zone 1 and will decrease as the worker moves through each zone away from the emission source.  Use of this approach captures the idea that there is a vapor concentration gradient surrounding the emission source, and that a worker, in the course of performing normal work duties, will move between these zones.

      A second important assumption concerns the rate at which air is exchanged within each zone.  In the implementation of the box model, air within a small space is exchanged at a faster rate than is air within a larger space.  This is due to the presence of local air currents and eddies.  In Zone 1, which is the smallest space defined in the model, the motion of the worker's hands and tools will serve to increase the rate of air exchange; however, in a larger space, local air currents will have a lesser effect on the overall rate of air exchange within that space.  As such, the air within a 3' x 3' x 3' space may be exchanging with surrounding air at a rate of 30 air changes per hour (ACH) even though the overall rate of air exchange within a 30' x 30' x 30' room is only 0.5 ACH.  In the model, it is assumed that air within Zone 1 is moving through the zone at a rate of about 2 mph.  This rate is cut in half for Zone 2, and by 75 percent in Zone 3.  The rate of air movement within Zone 3 is equivalent to about 50 feet per minute, which represents a background rate of air movement frequently seen in industrial facilities having moderate general dilution ventilation.  A mixing factor of 0.5 is assumed, which cuts the effective air exchange rate in half.

      Thus, to implement the box model, the variables in the working equation above were substituted as follows.  The variable S is the release rate in g/hr.  The value of S was derived from the Vintaging model used to estimate refrigerant release rates for various release scenarios.  The release rate per event (from the Vintaging model) 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 produced per plant per year divided by 365 days per year.  For scenarios where fewer than 365 units are manufactured per year, it is assumed that the event causing the emission occurs over a single 8-hour workday, rather than over several days.  For installation and repair operations, it is assumed that one event occurs per workday for large refrigeration systems and four events per workday for small systems.  For disposal operations involving refrigerators and freezers, other refrigeration appliances, and mobile air conditioners, it is assumed that 100 units are disposed of over an 8-hour shift.  For all other end-use sectors, it is assumed that one unit is disposed of during a single shift.

      The variable V represents the volume of space in which the worker is performing his or her work duties.  For each exposure scenario, it is assumed that a worker spends a certain percentage of time within each of the four zones, as follows.  For manufacturing and installation operations, it is assumed that a worker spends 10 percent of his or her time over an 8-hour workday in Zone 1, 50 percent in Zone 2, 30 percent in Zone 3, and 10 percent in Zone 4.  For repair operations, it is assumed that a worker spends 20 percent of the workday in Zone 1, 40 percent in Zone 2, 20 percent in Zone 3, and 20 percent in Zone 4; this reflects the likely possibility that, in repair operations as compared to manufacturing or installation operations, a worker will spend a larger proportion of the workday in close proximity to the emission source, but will also spend a greater proportion of the day away from the emission source while travelling to the repair site.

      After using the box model to estimate the average vapor concentration within each zone, a worker's 8-hour time-weighted-average exposure is calculated as follows:

where
      Cx = Concentration of vapor within Zone x; and
      Px = Percent of time spent in Zone x by the worker.

The term representing Zone 4 drops out because there is no exposure to refrigerant vapors in Zone 4 (by definition).

      To estimate short-term (i.e., 30-minute) worker exposures to refrigerant vapors and gasses, it is assumed that 25 percent of the daily emission is released over a 30-minute period.

5.3	DISCUSSION OF RESULTS

5.3.1	Presentation of Results

      The attached tables (Attachment 5-A) show the modelling results for each end-use sector, work operation, and alternative refrigerant.  For each scenario, the tables report the average 8-hour and 30-minute time-weighted average (TWA) concentrations of refrigerant present in each of the zones, and the estimated 8-hour and 30-minute TWA levels to which workers may be exposed.

      Exhibit 5-1 summarizes the occupational exposure limits for the alternative refrigerants that were used to determine whether workers may be exposed to potentially hazardous airborne gas or vapor concentrations.  Exhibit 5-2 summarizes the results for those scenarios where the model suggests that worker exposures may exceed either the 8-hour or 30-minute occupational exposure limit for the alternative refrigerant.  The highest exposures are predicted to occur during the manufacturing and disposing of industrial process (high pressure build-up) refrigeration systems.

5.3.2	Interpretation and Comparison of Model Results with Sampling Data

      Several observations suggest that the model will tend to overstate likely occupational exposures to alternative refrigerant vapors and gasses.  First, the emission estimates from the

	EXHIBIT 5-1
	OCCUPATIONAL EXPOSURE LIMITS FOR
	POTENTIAL ALTERNATIVE REFRIGERANTS*

                                  Substitute
                                   Material

                                   WGL (ppm)

                                   EGL (ppm)
HCFC-22
                                     1,000
                                     5,000
HFC-23
                                     1,000
                                     3,000
HCFC-123
                                        30
                                     2,500
HCFC-124
                                     1,000
                                     3,000
HFC-125
                                     1,000
                                     3,000
HFC-134a
                                     1,000
                                     3,000
HFC-143a
                                     1,000
                                     3,000
HCFC-142b
                                     1,000
                                     5,000
HFC-152a
                                     1,000
                                     4,000
HFC-227ea
                                     1,000
                                     3,000

*  This table may contain or utilize exposure limits that are not Agency verified or that were updated after this chapter was written.  Chapter 3 presents the most recent exposure limits for each chemical, identifies which are verified versus estimated values, identifies methods used to derive estimated values, and provides information sources.

Vintaging model are considered to be worst-case estimates.  Second, the assumptions regarding air exchange rates for each of the work zones do not reflect the use of any local exhaust ventilation, which is likely to be used in manufacturing and disposal operations involving any significant releases.

      The use of properly designed local exhaust ventilation or other means of isolating the worker from emission sources would likely prevent gas or vapor concentrations from exceeding the occupational exposure limits most of the time.  Given the assumed sizes of many of the potential releases (some of them exceeding a few hundred pounds), it would appear unlikely that an employer would conduct such operations without providing some means of mechanical ventilation.  It is for this reason that the exposure estimates for high-pressure industrial process refrigeration systems are certain to be unrealistically high.  In addition, for each release scenario, it is assumed that the entire estimated daily release occurs over a single 8-hour workday and at a single location.  This is not the case for many scenarios, and particularly for manufacturing operations, where the estimated daily release may occur over two or three workshifts or where the release may be spread out over two or more production lines.  Finally, most of the predicted exceedances over the occupational exposure limits are the result of assuming that there will be no recycling of HFC refrigerants.  To the extent that recycling technologies are used, exposures to HFCs should be below the occupational exposure limits for these compounds.

      The model's tendency to overstate worker exposures is further supported by sampling data obtained for HCFC-123 refrigerant during repair operations conducted on low-pressure

	EXHIBIT 5-2
	SUMMARY OF ESTIMATED WORKER EXPOSURE TO ALTERNATIVE REFRIGERANTS
	FOR SCENARIOS WHERE THE OCCUPATIONAL EXPOSURE LIMIT IS EXCEEDED[a]

                                 8-Hour TWA[b]
                                 30-Minute TWA
                                End-Use Sector
                                   Operation
                                  Substitute
                                  Material[c]
                                   Predicted
                                Exposure (ppm)
                                   Operation
                                  Substitute
                                  Material[c]
                                   Predicted
                                Exposure (ppm)
Retail Food (Parallel System)
Disposal

HFC-134a
HFC-125
HFC-143a
HFC-23
                                                                          1,579
                                                                          1,342
                                                                          1,917
                                                                          2,300
Disposal
HFC134a
HFC-125
HFC143a
HFC-23
                                                                          4,742
                                                                          4,030
                                                                          5,757
                                                                          6,909
Cold Storage Warehouses
Disposal
HFC-152a
HFC-23
                                                                          1,309
                                                                          1,234

Centrifugal Chillers (Low Pressure)
Manufacture
HCFC-123
                                                                          73[d]

Centrifugal Chillers (High Pressure)
Disposal
HFC-124
HFC-134a
HFC-227ea
                                                                          2,271
                                                                          3,050
                                                                          1,647
Disposal

HFC-124
HFC-134a
HFC-227ea
                                                                          6,819
                                                                          9,159
                                                                          4,928
Industrial Process (Low Pressure)
Manufacture
Repair
HCFC-123
HCFC-123
                                                                             54
                                                                             49

	EXHIBIT 5-2 (continued)
	SUMMARY OF ESTIMATED WORKER EXPOSURE TO ALTERNATIVE REFRIGERANTS
	FOR SCENARIOS WHERE THE OCCUPATIONAL EXPOSURE LIMIT IS EXCEEDED[a]

                                 8-Hour TWA[b]
                                 30-Minute TWA
                                End-Use Sector
                                   Operation
                                  Substitute
                                  Material[c]
                                   Predicted
                                Exposure (ppm)
                                   Operation
                                  Substitute
                                  Material[c]
                                   Predicted
                                Exposure (ppm)
Industrial Process
  (High Pressure          Build-Up)
Manufacture

Disposal
HFC-143a
HFC-152a

HFC-134a
HFC-152a
HFC-125
HFC-143a
HFC-23
                                                                          1,293
                                                                          1,016

                                                                         30,840
                                                                         47,661
                                                                         15,740
                                                                         18,375
                                                                         13,490
Manufacture

Disposal
HFC-134a
HFC-143a
HFC-152a
HFC-134a
HFC-152a
HFC-125
HFC-143a
HFC-23
                                                                          3,941
                                                                          7,751
                                                                          6,090
                                                                         92,608
                                                                        143,122
                                                                         47,266
                                                                         56,260
                                                                         40,509
Large Ice Makers
Repair
HFC-152a
                                                                          1,076

Ice Rinks
Disposal
HFC-134a
HFC-152a
HFC-23
                                                                          4,609
                                                                          7,123
                                                                          2,016
Disposal
HFC-134a
HFC-152a
HFC-23
                                                                         13,840
                                                                         21,390
                                                                          6,054
Central A/C and Home Heat Pumps
Manufacture
HFC-152a
                                                                          1,332

[a]	Exposure levels are rounded to the nearest whole number.
[b]	Time-weighted average.
[c]	The refrigerant blends analyzed for these sectors may be considered confidential business information (CBI) by the manufacturer.  As a result, the identification of the constituents of any blend and the proportion of each constituent contained in any blend are not presented in this exhibit.
[d]	One manufacturer's representative states that worker exposures to HCFC-123 during centrifugal chiller manufacture are typically 1 ppm or less, due to the use of exhaust ventilation.

centrifugal chillers (EPA 1991).  This study showed that worker exposures were generally well below 1 ppm as an 8-hour TWA during repair operations involving the use of recycling equipment; however, results from the model suggest that workers may be exposed to about 4 ppm HCFC-123 during these repair operations, even when proper recycling is used.  For the manufacture of low-pressure centrifugal chillers, the model suggests that workers could be exposed to HCFC-123 concentrations as high as 73 ppm as an 8-hour TWA; however, a representative of one manufacturer indicated that, due to the use of local exhaust ventilation, worker exposures were typically in the range of 1 ppm (personal communication).

      The analyses presented above did not consider the use of ammonia, butane, propane, or perfluoropropane as alternative refrigerants.  However, existing OSHA and ASHRAE standards governing the handling and use of these materials should serve to limit occupational exposures to them.  Currently, OSHA enforces permissible exposure limits (PELs) for two of these materials: ammonia (50 ppm as an 8-hour TWA), and propane (1000 ppm as an 8-hour TWA).  In addition, ASHRAE classifies butane and propane as "highly flammable" refrigerants, and ammonia as a "moderately flammable" refrigerant having high toxicity (ASHRAE Standard 34); as such, special requirements set forth in ASHRAE Standard 15 apply to the use of these materials as refrigerants.  These requirements include:

      	Prohibiting the use of any of these refrigerants in systems designed for human comfort;

      	Limiting the amount of refrigerant that can be used in systems installed in occupied areas;

      	Requiring the use of vapor detection alarms that activate when concentrations of refrigerant exceed toxic or explosive levels; and

      	Prohibiting the use of butane or propane in any system installed in commercial or institutional buildings (i.e., only industrial use is permitted).

5.4	POTENTIAL WORKPLACE FLAMMABILITY AND EXPLOSIVITY RISKS

      One of the alternative refrigerants considered in this analysis, HFC-152a, has been classified as a moderately flammable material under proposed ASHRAE Standard 34.  It has a lower flammability limit (LFL) of 4.4 percent in air (44,000 ppm) and a heat of combustion of less than 19,000 kJ/kg.  As such, it represents a lesser fire and explosion risk than propane or butane, which have LFL's that are less than half that of HFC-152a and heats of combustion greater than 19,000 kJ/kg.

      The risk of fire or explosion in an industrial setting arises when local concentrations of a flammable or explosive gas or vapor are allowed to exceed the lower flammable limit for the gas or vapor in the presence of an ignition source (i.e., flame, heat, electrical energy, or static sparks).  In general, when handling flammable or explosive materials, most industrial facilities consider that accumulations of gas or vapor concentrations of from 10 to 25 percent of the LFL or higher for that substance represent an emergency situation that requires corrective action.  For HFC-152a, an emergency concentration would therefore be considered to exist if concentrations exceeded 4,400 to 11,000 ppm (i.e., 10 to 25 percent of the LFL).

      The exposure assessment analysis presented above shows that, under worst-case assumptions and assuming no recycling, local short-term concentrations of HFC-152a would not be expected to exceed 4,400 ppm under normal operating conditions in all but one end-use sector (high-pressure industrial process refrigeration).  As stated above, EPA believes that the exposure estimates for this end-use sector are unrealistically high because of the assumption that no mechanical ventilation would be used during operations involving the release of such large quantities of refrigerant.  Thus, with the appropriate use of equipment designed for the safe use of flammable or explosive gases and with the use of mechanical ventilation systems, concentrations of HFC-152a are not likely to exceed 10 percent of the LFL and should therefore not present a substantial fire or explosion risk in the workplace.  Isolation of potential ignition sources (such as welding operations conducted on the assembly line) from processes involving the handling of HFC-152a, and the use of combustible gas detectors and alarm systems, will serve to further reduce this potential risk.

	CHAPTER 5 REFERENCES

NIOSH (Mutchler, J.E.)  1973.  "Principles of Ventilation."  The Industrial Environment--It's 	Evaluation and Control.  NIOSH, Center for Disease Control, U.S. Department of Health and Human Services.  ch. 39.

U.S. EPA.  1990.  Revised Draft:  Occupational Exposure and Environmental Release Data for 	Chlorofluorocarbons (CFCs) and Their Substitutes.  Office of Toxic Substances.

U.S. EPA.  1991.  Results of Employee Exposure Monitoring for HCFC-123 at Centrifugal Chiller 	Installations.  Final Report.  November, 1991.

	ATTACHMENT 5-A

	6.  CONSUMER EXPOSURE AND RISK SCREENING ANALYSIS

      This chapter presents a screening level assessment of the risks to consumers from releases of CFC substitutes used in home appliances (refrigerators and freezers, central air conditioners, window air conditioners, and miscellaneous refrigerated appliances) and automobile air conditioners.  These are the only applications in the refrigeration and air conditioning sectors that have consumer end uses.

      The end uses and substitutes evaluated in this chapter are presented below.  The composition of one -- R200b -- is confidential:

      	Refrigerators and Freezers:

            	HCFC-22
            	HFC-134a
            	HFC-152a
            	HCFC-22/HCFC-142b
            	HCFC-22/HFC-152a/HCFC-124
            	R200b

      	Dehumidifiers: Same as refrigerators and freezers.

      	Central Air Conditioners and Home Heat Pumps:

            	HFC-125
            	HFC-134a
            	HFC-125/HFC-143a
            	HFC-23/HFC-134a
            	HFC-125/HFC-143a/HFC-134a
            	HCFC-22/propane/HFC-125

      	Window Air Conditioners:

            	HFC-125
            	HFC-134a
            	HFC-125/HFC-143a
            	HFC-23/HFC-134a

      	Mobile Air Conditioners:

            	HFC-134a
            	HCFC-22/HFC-152a/HCFC-124

      This chapter first presents an assessment of consumer exposure to releases from home appliances, followed by an analysis for mobile air conditioners.  The analyses performed are screening analyses whose purpose is to identify the proposed substitutes for all end uses that may pose any potential concern for human health or environmental risk.  As a result, the analyses employ conservative assumptions that tend to overestimate potential risk.  Considerable uncertainty exists in these analyses.

6.1	HOME APPLIANCES

      Three types of releases from home appliances are of interest for consumer exposure and risk:  (1) routine operating leakage, (2) releases during servicing, and (3) accidental releases.

      A report on consumer exposure to CFCs and their substitutes prepared for EPA (Versar 1990) examined exposures from leakage and servicing releases from refrigerators, freezers, and dehumidifiers.  Using engineering estimates of releases as input to an equation given on page 4-5 of this report, average annual concentrations of CFC substitutes were calculated in median-sized and 10th percentile-sized homes.  Because this consumer exposure analysis spreads the releases and resulting concentrations over a year's time, it assesses only long-term, chronic exposures.  It does not address potential risks from short-term exposure to higher concentrations that result from servicing or accidental releases.

      Below, potential risks from chronic exposures are examined by comparing estimated doses from the consumer exposure report to toxicity values for the CFC substitutes.  Subsequently, a screening analysis of potential risks associated with higher, but shorter-term, exposures is presented.  Finally, potential safety concerns from the use of HFC-152a in household refrigerators are discussed.

6.1.1	Risks from Long-term Exposure to Leakage and Servicing Events  Previous Estimates

      The consumer exposure report estimated releases from refrigerators, freezers, and dehumidifiers with refrigerant charge sizes ranging from about 140 to 570 g.  The annual leakage rate was assumed to be 0.2 percent of the charge (0.28 to 1.1 g), and the servicing emission was assumed to be 85 g.

      The estimated average annual concentrations in two different house sizes  a median size of 411 m[3] (equivalent to 1,808 ft[2], assuming an 8-ft ceiling height) and a 10th percentile size of 174 m[3] (766 ft[2], assuming an 8-ft ceiling)  ranged from 0.4 μg/m[3] to 3.7 μg/m[3] for annual leakage.  To estimate potential risk from chronic exposure to leakage, the consumer exposure report's exposure information was combined with available toxicity information as follows:

      	To evaluate noncarcinogenic effects, the modeled exposure concentrations were compared to reference concentrations (RfCs).

      	To calculate cancer risks, a lifetime average daily dose of the substitute was estimated using the exposure concentration, a 20 m[3]/day inhalation rate, and a 70 kg body weight.

The RfCs and cancer slope factor used in this assessment are given in Chapter 3 of this document.

      The highest estimated average annual exposure for routine leakage from the consumer exposure report  3.7 μg/m[3]  is well below the RfCs for all substitutes.  Only one of the substitutes  HCFC-22  is a possible carcinogen.  Assuming that people are exposed to an HCFC-22 concentration of 3.7 μg/m[3] 24 hours per day, 365 days per year, over a 70-year lifetime, the cancer risk for HCFC-22 is 2.1E-07.  Based on EPA guidelines regarding levels of risk, chronic health effects from long-term exposure to routine leakage of CFC substitutes from home appliances are not of concern.

      The consumer exposure report estimated the typical servicing emissions from all pieces of equipment to be 85 grams per service.  During a year in which the equipment is serviced once, the report calculated average annual concentrations ranged from 118 μg/m3 for a median-sized house to 279 μg/m[3]  for a house sized in the 10th percentile.  These are also well below the RfCs for the substitutes.  If it is assumed that servicing occurs once every year and that people spend all of their time at home, the cancer risk associated with lifetime exposure to HCFC-22 would be 6.7E-06 in the median house and 1.6E-05 in the smaller house.  However, these values overstate potential cancer risks because (1) home appliances such as refrigerators, freezers, and humidifiers are serviced much less frequently than once a year; and (2) people typically do not spend all of their time at home.  Given these factors, EPA believes that actual cancer risks are well below 10[-5], the threshold level of concern.

6.1.2	Risks from Short-term Exposure During Servicing and Accidental Releases

      The next step was to examine potential health risks from short-term exposure to temporarily higher concentrations associated with servicing emissions and accidental releases.  Four situations were examined:

      	Exposure to vapors from refrigerators or freezers located in the kitchen;

      	Exposure to vapors from a dehumidifier located in a room;

      	Exposure to vapors from a central air conditioner or heat pump, where the release occurs in the basement; and

      	Exposure to vapors from a window air conditioner located in a room.

Approach

      To simulate the initial increase and subsequent decrease in airborne concentrations resulting from refrigerant releases, the same "box model" approach was used as in the previous analysis of occupational exposure (see Chapter 5).  This model was derived from a differential material balance that, when integrated, provides a basis for relating the air concentration of a contaminant to the generation and removal rates of the contaminant.

      To calculate releases, it was assumed that the amount of substitute released was equal to the amount of CFC released.  CFC release information was derived from input files to the Vintaging Model.  The following assumptions concerning releases were made for this analysis:

      	Servicing releases occur over 15 minutes.  HCFCs are recycled at servicing (under Section 608 of the Clean Air Act, HCFC recycling became mandatory in 1992).  Because HFC recycling will not be mandatory until 1995, servicing releases for HFCs are calculated both with and without recycling.  If there is no recycling, the entire charge is released.  The releases are as follows:

                                                Recycling	No Recycling

            Refrigerators and Freezers		   	   15 g	   	  300 g
            Dehumidifiers					   20 g	   	  400 g
            Central A/Cs and Heat Pumps		   80 g	 	3,840 g
            Window Air Conditioners			   40 g	 	1,820 g

      	Accidental releases are modeled as leakage of the entire charge over two different time frames:  15 minutes and four hours.  The releases are the same as those listed above under the "no recycling" scenario.

      The following inputs were made to the box model:

      	Room sizes:

            	411 m[3] for house volume (equivalent to 1,808 ft[2], assuming an 8-ft ceiling height);
            	18 m[3] (79 ft[2]) for the kitchen;
            	102 m[3] (449 ft[2]) for the basement; and
            	41 m[3] (180 ft[2]) for the room housing the window A/C or miscellaneous unit.

      	Air exchange rate:

            	0.25 air changes per hour (ACH) for the house, basement, and room; and
            	2.3 ACH for the kitchen.

      Thirty minute time weighted average (TWA) exposures were calculated and compared to the interim emergency guidance levels (EGLs) shown in Chapter 3.

Results

      Exhibits 6-1 through 6-4 show the 30 minute average concentrations and their ratios to the interim EGLs for the relevant substitutes.  (The values shown in these tables are based on the substitute being composed of 100 percent of the named chemical.  In practice, some substitutes would be used only in a blend.)  The results are discussed below.

      The results show that servicing with recycling never results in concentrations above the EGL.  All of the other scenarios involve release of the entire charge.  This can result from an accident or  for the HFCs only  from a servicing event that does not involve recycling.  The modeling indicates that, unless otherwise noted, the concentrations of the following substitutes or combinations of substitutes never exceed the EGL even if the entire charge is released:

      	Refrigerators and freezers:

            	HCFC-22;

            	HFC-134a;

            	HFC-152a;

                                  EXHIBIT 6-1
                30-MINUTE AVERAGE CONCENTRATIONS FROM SERVICING
                     AND ACCIDENTAL RELEASES, AND RATIO TO
                   INTERIM EMERGENCY GUIDANCE LEVELS (EGLs):
                          REFRIGERATORS AND FREEZERS

                            Service, With Recycling
                          Service, Without Recycling
                              Accidental 15-Min.
                                    Release
                            Accidental 4-Hr Release
KITCHEN
30-Min. TWA, mg/m[3]

Ratio to EGL:
        HCFC-22
        HCFC-124
        HCFC-142b
        HFC-134a
        HFC-152a
        HFC-227ea
     430

     0.025
     0.025
     0.022
     0.034
     0.032
     0.020
   10,000

    NA
    NA
    NA
    0.79
    0.74
    0.48
   10,000

    0.57
    0.58
    0.50
    0.79
    0.74
    0.48
  3,300

   0.19
   0.19
   0.17
   0.26
   0.24
   0.16
HOUSE
30-Min. TWA, mg/m[3]

Ratio to EGL:
        HCFC-22
        HCFC-124
        HCFC-142b
        HFC-134a
        HFC-152a
        HFC-227ea
      24

     0.0014
     0.0014
     0.0012
     0.0019
     0.0018
     0.0011
     550

     NA
     NA
     NA
    0.044
    0.041
    0.026
     550

    0.031
    0.032
    0.028
    0.044
    0.041
    0.026
    570

   0.033
   0.033
   0.029
   0.045
   0.042
   0.027

                                  EXHIBIT 6-2
                30-MINUTE AVERAGE CONCENTRATIONS FROM SERVICING
                     AND ACCIDENTAL RELEASES, AND RATIO TO
                   INTERIM EMERGENCY GUIDANCE LEVELS (EGLs):
                                 DEHUMIDIFIERS

                            Service, With Recycling
                          Service, Without Recycling
                              Accidental 15-Min.
                                    Release
                            Accidental 4-Hr Release
ROOM
30-Min. TWA, mg/m[3]

Ratio to EGL:
        HCFC-22
        HCFC-124
        HCFC-142b
        HFC-134a
        HFC-152a
        HFC-227ea
     440

     0.025
     0.026
     0.022
     0.035
     0.033
     0.021
   6,100

    NA
    NA
    NA
    0.48
    0.45
    0.29
   6,100

    0.35
    0.36
    0.31
    0.48
    0.45
    0.29
  6,400

   0.37
   0.37
   0.32
   0.51
   0.47
   0.30
HOUSE
30-Min. TWA, mg/m[3]

Ratio to EGL:
        HCFC-22
        HCFC-124
        HCFC-142b
        HFC-134a
        HFC-152a
        HFC-227ea
      42

     0.0024
     0.0025
     0.0021
     0.0033
     0.0031
     0.0020
     610

    NA
    NA
    NA
    0.048
    0.045
    0.029
     610

    0.035
    0.036
    0.031
    0.048
    0.045
    0.029
     630

   0.036
   0.037
   0.032
   0.050
   0.047
   0.030

                                  EXHIBIT 6-3
                30-MINUTE AVERAGE CONCENTRATIONS FROM SERVICING
                     AND ACCIDENTAL RELEASES, AND RATIO TO
                   INTERIM EMERGENCY GUIDANCE LEVELS (EGLs):
                 CENTRAL AIR CONDITIONERS AND HOME HEAT PUMPS

                            Service, With Recycling
                          Service, Without Recycling
                              Accidental 15-Min.
                                    Release
                            Accidental 4-Hr Release
BASEMENT
30-Min. TWA, mg/m[3]

Ratio to EGL:
        HCFC-22
        HFC-23
        HFC-125
        HFC-134a
        HFC-143a
     590

     0.034
     0.069
     0.040
     0.047
     0.058
  28,000

    NA
    3.3
    1.9
    2.2
    2.7
   28,000

     1.6
     3.3
     1.9
     2.2
     2.7
  29,000

    1.7
    3.4
    2.0
    2.3
    2.8
HOUSE
30-Min. TWA, mg/m[3]

Ratio to EGL:
        HCFC-22
        HFC-23
        HFC-125
        HFC-134a
        HFC-143a
     150

     0.0086
     0.018
     0.010
     0.012
     0.015
   7,000

    NA
    0.82
    0.48
    0.56
    0.69
   7,000

    0.40
    0.82
    0.48
    0.56
    0.69
   7,200

    0.41
    0.84
    0.49
    0.57
    0.71

                                  EXHIBIT 6-4
                30-MINUTE AVERAGE CONCENTRATIONS FROM SERVICING
                     AND ACCIDENTAL RELEASES, AND RATIO TO
                   INTERIM EMERGENCY GUIDANCE LEVELS (EGLs):
                            WINDOW AIR CONDITIONERS

                            Service, With Recycling
                          Service, Without Recycling
                              Accidental 15-Min.
                                    Release
                            Accidental 4-Hr Release
ROOM
30-Min. TWA, mg/m[3]

Ratio to EGL:
        HFC-23
        HFC-125
        HFC-134a
        HFC-143a
     740

     0.087
     0.050
     0.059
     0.073
  34,000

    4.0
    2.3
    2.7
    3.3
  34,000

    4.0
    2.3
    2.7
    3.3
  34,000

    4.0
    2.3
    2.7
    3.3
HOUSE
30-Min. TWA, mg/m[3]

Ratio to EGL:
        HFC-23
        HFC-125
        HFC-134a
        HFC-143a
      74

     0.0087
     0.0050
     0.0059
     0.0073
   3,300

    0.39
    0.22
    0.26
    0.32
   3,300

    0.39
    0.22
    0.26
    0.32
   3,400

    0.40
    0.23
    0.27
    0.33

            	R200b.  The weighted average of the ratios is below 1.0, indicating that this blend is of no concern even if the health hazards are additive.

            	HCFC-22/HCFC-142b.  The weighted average of the ratios is below 1.0, indicating that this blend is of no concern even if the health hazards are additive.

            	HCFC-22/HFC-152a/HCFC-124.  The weighted average of the ratios is below 1.0, indicating that this blend is of no concern even if the health hazards are additive.

            Releases from refrigerators and freezers are based on a charge size of 300 g.  A conservative estimate of charge sizes for refrigerators and freezers is 240 g for refrigerators and 340 g for freezers.  Since more people own refrigerators than freezers, the estimated charge size of 300 g used in this analysis actually overstates releases and exposures for most of the population.

      	Dehumidifiers:

            	HCFC-22;

            	HFC-134a;

            	HFC-152a;

            	R200b.  The weighted average of the ratios is below 1.0, indicating that this blend is of no concern even if the health hazards are additive.

            	HCFC-22/HCFC-142b.  The weighted average of the ratios is below 1.0, indicating that this blend is of no concern even if the health hazards are additive.

            	HCFC-22/HFC-152a/HCFC-124.  The weighted average of the ratios is below 1.0, indicating that this blend is of no concern even if the health hazards are additive.

      Under the assumptions used in this analysis, all of the other substitute/end use combinations result in exposures above the EGL if the entire charge is released:

      	Central air conditioners and home heat pumps:  None of these compounds or blends exceed their EGLs in the house.  In the basement, however, all alternatives (taken either individually or as blends) exceed their EGLs.  These figures are based on the assumption that about 20 percent of central air conditioners and home heat pumps have a charge size of 3,800 g, about 75 percent have a charge size of 3,000 g, and 5 percent have a charge size of 700 g.

      	Window air conditioners:  All alternatives exceed their EGLs in the room where the air conditioner is located.  All window air conditioners are assumed to have a charge size of 1,800 g.

As discussed above, these results are based on a comparison of 30-minute TWA exposures with interim EGLs.  Another way to approach this assessment would be to calculate shorter-term exposures and compare them to the cardiotoxic LOAELs or NOAELs given in Chapter 3.  If EPA were to calculate 15 minute TWA exposures for the scenarios with 15-minute releases (i.e., servicing without recycling, 15-minute accidental release), the TWA exposures would be well below the cardiotoxic NOAELs and LOAELs for every substitute.

6.1.3	Summary of Modeling Results

      Analysis has shown that unless the entire refrigerant charge is released over a short period of time, none of the substitutes exceed EPA's threshold of concern for human health risk in any piece of equipment.  Routine leakage and servicing with recycling simply will not release enough refrigerant to pose significant short-term or long-term risks to human health.

      If the entire charge is released, the calculated 30-minute average concentrations exceed the EGLs for substitutes in air conditioning equipment.  The following factors should be considered when judging whether these exceedances are cause for concern:

      	Recycling at servicing will be required for the HFCs by 1995.  Until then, EPA believes that most HFCs will be recycled anyway, because of their high cost relative to CFCs.

      	Accidental releases of an entire refrigerant charge occur infrequently.  The UNEP (1992) reports that less than 5 percent of the refrigerators and freezers have accidental releases of the entire charge.

      	The analysis is based on conservative assumptions:

            	Exposures are generally calculated for the equipment with the largest charge size.

            	All releases are assumed to occur indoors.  This is not necessarily the case for central air conditioners, home heat pumps, and window air conditioners.

            	It was assumed that people remain in the room in which the release occurs for 30 minutes.

            	Air exchange rates estimated are conservative; they reflect an energy efficient house with no windows or doors open.

            	The EGLs that are used as toxicity benchmarks are conservative, and incorporate a margin of safety.  A similar approach based on cardiotoxic LOAELs or NOAELs would show that exposures are below the concern level.

6.1.4  Safety Concerns:  HFC-152a in Household Refrigerators

      The release of HFC-152a in a household kitchen can potentially cause personal injury in a few ways:

      	injury from sudden overpressure (i.e., shock wave);
      	injury from shrapnel resulting from an explosion; and
      	injury from thermal radiation.

The likelihood and severity of these risks were studied in a report on risk assessment of flammable refrigerants for home appliances.  (EPA 1991).  Using a mathematical model to relate vapor concentration to peak overpressure, the report found that the sudden ignition of a typical charge of HFC-152a would be sufficient to cause eardrum rupture of a person who was in the kitchen at the time of ignition.  The explosion would also likely cause structural damage to the house.  However, the report also found that sudden ignition of a full charge was an extremely unlikely event; rather, there would be some dispersion of HFC-152a vapor below the lower flammable limit of 4.4 percent, and thus the subsequent event would be limited to a vapor fire rather than an explosion.

      Using information on historical leakage rates coupled with a fault tree analysis, the report predicts that the probability of a fire or explosion due to an external refrigerant leak is

2.0 x 10[-8]/yr (5.0 x 10[-7] under worst-case assumptions).  The probability of an explosion due to leakage of HFC-152a inside the refrigerator is considerably smaller (2.7 x 10[-13]/yr under average-case assumptions and 7.0 x 10[-12]/year under worst-case assumptions).

6.2	MOBILE AIR CONDITIONERS (MACs)

6.2.1	Approach Used in a Previous Consumer Exposure Report

      The consumer exposure report (Versar 1990) estimated MAC emissions to which consumers could be exposed as the product of four factors: (1) total charge of refrigerant in the system; (2) fraction of refrigerant that leaks from the system before it is noticed and repaired; (3) fraction of refrigerant entering the vehicle passenger compartment; and (4) frequency of leak episodes.

      	Total charge:  Total refrigerant charge is based on averages from a previous study (Chilton 1985) for four vehicle class sizes: subcompact, 27 ozs.;  compact, 38 ozs.; midsize, 47 ozs.; and large, 53 ozs.

      	Total refrigerant leaked before being noticed/repaired:  In newer vehicles with protection devices and in warmer climates, the consumer exposure report assumed that leaks would be noticed and fixed quickly.  In cooler climates and older cars without protection devices, a MAC leak would probably go unnoticed until most of the refrigerant had leaked.  Overall, the report assumed an average leak of 50 percent of charge capacity.

      	Fraction of leak entering passenger compartment:  This parameter depends on the location of the leak (evaporator case or engine compartment) and whether the vehicle is in motion or stationary.  The consumer exposure report assumed that the vehicle is stationary 15 percent of the time that it is in use; that the air conditioning or heat are on 2/3 of the time a vehicle is in operation; and that the average annual consumer vehicle operation time is 526 hours.

      	Leak episodes per vehicle:  The consumer exposure report assumed that there are 0.76 leaks/yr/vehicle.

      Leaks from the evaporator case result in infiltration of the entire release into the passenger compartment, and therefore the highest consumer exposures.  Therefore, the remainder of this discussion focuses on evaporator case leaks.  The consumer exposure report's emission calculations for evaporator case leaks are as follows:

            Emissions, g/yr = (oz. charge/vehicle class) x (0.50 fraction emitted) x (28.35 g/oz) x (0.76 leaks/yr)

                  Size class			Emissions, g/yr
                  Subcompact				290
                  Compact				409
                  Midsize				506
                  Large					602

      When a leak occurs in the evaporator case, the rate of air intake affects the concentration of the refrigerant in the passenger compartment by either circulating the compartment air out of the vehicle (high ventilation rate) or letting the air stand in the compartment (low ventilation rate), allowing refrigerant concentrations to build up.  The consumer exposure report assumed that the MAC is working at maximum level while it is on, minimizing ventilation.  The average speed of travel for a vehicle, according to this report, is 30 mph, yielding a 27 ACH (27 full compartment volumes/hour) ventilation rate.  Concentrations are then calculated in terms of buildup of refrigerants in the recirculated air.  Refrigerant concentrations also depend on passenger compartment sizes, which are broken down into the same four units by a previous study (Chilton 1985):  subcompact vehicles, 2.3 m[3];  compact, 2.5 m[3];  midsize, 2.8 m[3];  and large, 3.1 m[3].  The consumer exposure report's calculated passenger compartment concentrations are as follows:

            Concentration, mg/m[3] = (emissions, g/yr) x (1 yr/8760 hrs) x (ventilation rate,
            1 hr/27) x (1000 mg/g) x (1/passenger compartment volume, m[3]) =

                  Size class			Concentration, mg/m[3]							Subcompact				 0.53
                  Compact				 0.69
                  Midsize				 0.76
                  Large					 0.82

      Comparing these concentrations to reference concentrations (RfCs) for the substitutes (see Chapter 3) shows that the highest estimated passenger compartment concentration (0.82 mg/m[3]) is far below all of the RfCs.

      HCFC-22 is the only possible carcinogen of the four substitutes analyzed in the study.  If the consumer exposure report's exposure assumptions are used (inhalation rate is 0.6 m[3]/hr for a driving adult; average consumer vehicle operation time is 526 hours per year), the lifetime cancer risk is 2.0 x 10[-6].

6.2.2	Comparison of Parameters Contained in Consumer Exposure Report with Data from Other Sources

      Some of the parameters built into the consumer exposure report's MAC analysis (Versar 1990) are also included in EPA's Vintaging Model and the Market Vision Research Report.  Parameters addressed by both the consumer exposure report and one of these other sources include: (1) total MAC charge; (2) total charge lost before leak is detected and fixed; (3) frequency of operational leak events; and (4) emissions to the vehicle passenger compartment.  Below, the values used in these other sources are compared to those used by the consumer exposure report.

      	Total MAC charge:  While the consumer exposure report assumed 53 oz. maximum for total refrigerant charges, the Vintaging Model uses a less conservative 42.3 oz. upper bound.

      	Total charge lost before the leak is detected and fixed:  The Vintaging Model assumes a loss of 30 percent of the initial charge, substantially less than the more conservative average of 50 percent loss of initial charge used by the consumer exposure report.

      	Frequency of operational leak events:  According to the consumer exposure report, the frequency of leak events is 0.76 leaks/car/year.  This value is based on an Automotive Refrigeration Products Institute study in which 384 recharges were performed on 506 air-conditioned vehicles in one year.  According to the Vintaging Model, 37 percent of cars with MACs have their MACs serviced in any given year.  Thus, the servicing (and therefore, leakage) frequency in the consumer exposure report is about two times higher than the Vintaging Model.

      	Total emissions to the passenger compartment:  The Vintaging Model assumes that upper end operating releases from MACs are about 100 grams per year.  This is much lower than the upper end of 602 grams per year assumed by the consumer exposure report.

      All else being equal, a decrease in the value of any of these parameters would result in reduced risk.  As shown above, the values assigned to these parameters by the other sources are always lower than those used by the consumer exposure report.  Therefore, any adjustments that might be made to the consumer exposure analysis to be consistent with these other sources would only serve to reduce the already-low exposures and associated health risks.

6.2.3	Summary

      The consumer exposure report estimated consumer exposure to emissions of CFC substitutes from MACs.  These exposure levels are below those that would raise concern for human health risks.  An examination of this report's inputs and assumptions indicates that the analysis is conservative, confirming that consumer exposure is not of concern.

	CHAPTER 6 REFERENCES

Automotive Refrigeration Products Institute.  1988.  1988 Private Sector Vehicle Refrigerant Consumption Study.  Published by the Automotive Refrigeration Products Institute, Lanham, MD.

Chilton.  1985.  Chilton's Guide to Air Conditioning Repair and Service.  Chilton Book Co., Radnor, PA.

Market Vision Research Report.  Results from survey work performed for the Automotive Refrigerant Products Institute.

U.S. EPA.  1991.  Risk Assessment of Flammable Refrigerants for Use in Home Appliances, Revised Draft Report.  Global Change Division.  September 10, 1991.

Versar Inc.  1990.  June 19.  Revised Draft Final Report, Consumer Exposure to Chlorinated Fluorocarbons (CFCs) and CFC Substitutes.

	7.  GENERAL POPULATION EXPOSURE AND RISK ANALYSIS

      This chapter presents a screening level assessment of the risks to the general population from exposure to ambient air releases of substitutes for CFCs in the refrigeration and air conditioning sectors.  EPA previously performed a similar study (EPA 1990a) using data from another report (EPA 1990c).  Since then, more recent data on CFC emissions from refrigeration and air conditioning equipment have been collected and a new analysis conducted.  The evaluation of substitutes has also been expanded to include compounds not previously included in EPA reports.

      This analysis assesses each of 20 main end uses in the refrigeration and air conditioning sectors.  To develop this list of 20 end uses, the 49 end uses covered by the Vintaging Model were subdivided into equipment types with similar charge sizes and emission rates.  For each end use, this report examines compounds identified by EPA as possible substitutes for present CFC use.  The list of end uses and substitutes is presented in Attachment 7-A.

      The substitutes are grouped into four categories for this analysis:  (1) the HCFCs and HFCs; (2) other alternative refrigerants, including ammonia, butane, isobutane, propane, perfluoropropane, cyclopropane, and dimethyl ether; (3) chlorine; and (4) lithium bromide/water absorption and ammonia/water absorption.  Each category is discussed in a separate section below.  Alternatives to mechanical refrigeration (e.g., evaporative coolers and turbochillers) are not analyzed, since these alternatives do not use chemical refrigerants and therefore pose no exposure risks to the general population.

      The four analyses below are presented as screening analyses.  Their purpose is to identify the proposed substitutes for all end uses that may pose any potential concern for human health or environmental risk.  As a result, the analyses employ conservative assumptions that tend to overestimate potential risk.  Considerable uncertainty exists in these analyses.  The reader should recognize the caveats and limitations identified throughout the chapter.

7.1	HCFCs AND HFCs

7.1.1	Approach

      This analysis of the HCFCs and HFCs uses conservative screening assumptions to estimate potential risks.  The basic approach is to:  (1) estimate high-end annual releases of substitutes from equipment manufacturing plants, operating sites, service stations, and recycling centers or salvage yards; (2) use generic dispersion factors to calculate concentrations of the substitutes in air near the release site; and (3) compare these concentrations to health-based reference concentrations (RfCs) and, for carcinogens, calculate cancer risk.  These three steps are discussed in more detail below.

A.	Estimating Ambient Air Releases

      To estimate releases to ambient air, the first step was to identify the activities that lead to emissions and the types of sites at which such activities occur.  Activities through which CFC substitutes are released to the environment include equipment manufacture, installation, operation, servicing, and disposal.  The types of sites at which these activities occur include factories, operating sites, service stations, and recycling centers or salvage yards.

      The second step was to calculate the amount of CFC substitute released during each activity.  For the screening-level analysis, it was assumed that in all cases the amount of substitute released would equal the amount of CFC released presently.  Most CFC release information was derived from input files to the Vintaging Model; some data were received directly from industry associations and individual manufacturers.

      The emissions values used in the exposure assessment for each end use represent the highest values that would be expected to occur as a result of typical refrigeration practices.  Release estimates for each of the 20 end uses were based on the equipment type with the highest emission rate within that end use (generally the equipment with the largest charge size).  Catastrophic scenarios, such as a factory explosion that could cause temporarily high exposures in a nearby town, were excluded.

      Emissions during servicing and disposal are subject to recycling, which can greatly decrease the amount of refrigerant released to ambient air.  Under Section 608 of the Clean Air Act, the recycling of HCFCs became mandatory in 1992.  However, HFC recycling will not be required until 1995.  Therefore, scenarios both with and without recycling were examined for HFCs, but only scenarios with recycling for HCFCs.

      The third step in estimating releases involved using the information generated in the first two steps to calculate the amount of CFC substitute released to the atmosphere, in a year's time, from each type of release site.  The methods used to calculate these releases are summarized below.

      	Releases from factories:  Annual air releases of HCFCs and HFCs from factories were calculated by multiplying the number of units manufactured per factory per year by the amount of substitute released per unit at the factory.  One end use, low pressure centrifugal chillers, was an exception.  On the recommendation of a leading manufacturer, it was assumed that only 20 percent of the units were tested (and therefore charged and recovered) at the factory.  Data derived from the Vintaging Model, and originally from comprehensive industry surveys, were used to estimate the total number of pieces of equipment manufactured per year in the U.S.  In calculating the number of units manufactured per plant per year, unequal market share was assumed (i.e., that some manufacturers are larger and produce more units per year).  More accurate data were used if verifiable information was readily accessible.  Manufacturing emissions include emissions associated with equipment and component testing.  Where applicable, charging and leak testing emissions were also included.

      	Releases from equipment operating sites:  To estimate air releases from operating sites, the highest possible amount of CFC substitute that could be released from an operating site in any given year was calculated, which would be either the year of installation or disposal.  To do this, the releases from equipment operation, servicing, and either installation or disposal were added together, depending upon which of the latter two activities' releases was higher.  ("Disposal" releases occur at the equipment operating site if the charge is drained or removed at the site before the equipment is dismantled, which has been assumed in all cases except for automobile air conditioners (MACs) and household appliances.)

      	Releases from service stations:  This release site applied only to the MACs end use.  Two types of activities that cause emissions typically occur at service stations: the installation of after-market MACs and the servicing of MACs.  Annual air releases associated with each activity were calculated by multiplying the number of MACs installed and serviced annually at service stations by the amount of substitute released during each installation or servicing.  Since Section 609 of the CAA mandates the recycling of refrigerants during the servicing of MACs, emission estimates for servicing assumed that recycling would occur.  The annual installation and servicing releases were added together to derive the total annual releases from the service station.

      	Releases from recycling centers/salvage yards releases:  A centralized equipment disposal scenario was created for each of two types of end uses  household appliances and MACs:

            	The disposal scenario for household appliances was based on an actual site  an Appliances Recycling Centers of America (ARCA) facility in Minneapolis, Minnesota  which processes refrigerators, freezers, room air conditioners, and dehumidifiers.  Releases were calculated by multiplying disposal emissions by the number of appliances processed annually at that site.

            	The disposal scenario for MACs is a large automobile salvage yard.  Releases were estimated by multiplying disposal emissions by the number of cars processed annually that contain MACs which still possess their charge.  Information on these parameters was obtained from a New Jersey Department of Environmental Protection study (Aucott 1990).

      Attachment 7-B details all of the assumptions used for estimating ambient air releases for each end use.

B.	Estimating Downwind Concentrations

      Downwind concentrations were estimated using the Industrial Source Complex Long Term (ISCLT) Dispersion Model, provided by Versar, an Agency contractor, and summarized in Attachment 7-C.  This approach consisted of converting the release estimates from kilograms per year to grams per second, and then multiplying by normalized dispersion factors (in μg/m[3] per g/sec).  These calculations yielded fence-line concentrations in μg/m[3].  Professional judgment was used to determine which factors to apply to each type of site.

C.	Screening Potential Risks

      To estimate potential risk, exposure information was merged with available toxicity data, as follows:

      	To evaluate noncarcinogenic effects, the modeled exposure concentrations were compared to reference concentrations (RfCs).

      	To calculate cancer risks, EPA's standard risk equation was used.  A lifetime average daily dose of the substitute was estimated using an exposure concentration, an average 20 m[3]/day inhalation rate, and an average body weight of 70 kg.  For factory releases, the calculated cancer risks were adjusted to account for the phaseout of HCFCs.  HCFC-22 (a long-lived HCFC) will be phased out of new equipment production by 2010; therefore, a person living downwind of a factory producing equipment using HCFC-22 would be exposed to the substitute for only 18 years (1992 to 2010), instead of the full 70 years which the cancer risk equations assume.  Thus, a correction factor of 18/70 was used to calculate cancer risks for HCFC-22 from factories.  Similarly, for HCFC-123, a short-lived HCFC scheduled to be out of production by 2015, a correction factor of 23/70 was applied to the calculated cancer risks.  The reader should note that the projected dates for these accelerated phaseouts are tentative and subject to change.

The reference concentrations and cancer potency factors used in this assessment are given in Chapter 3 of this document.

7.1.2	Results

      All end uses have calculated exposure concentrations well below the reference concentrations for each HCFC and HFC substitute.  Estimated cancer risks from HCFC-22 and HCFC-123 were highest during factory releases, but still below 1E-05, and are therefore not considered to be of concern.  Exhibit 7-1 summarizes the results, showing the highest exposure concentration for each substitute and the end use responsible.  Complete results for each end use and potential substitute can be found in Attachment 7-D.

7.1.3	Caveats and Limitations

      This screening analysis of risks to the general population is a simple screening analysis that incorporates a variety of simplifying assumptions.  The approach was intended to be conservative, i.e., to overestimate exposure point concentrations and potential human health risks.  The major caveats and limitations of the analysis are listed below.

A.	Estimating Releases.  It was necessary to make assumptions to characterize releases, and the assumptions that would lead to the most conservative risk estimates were generally chosen.

      	Within each end use grouping, there may have been several types of equipment with slightly varying charge sizes.  It was assumed that the charge size of all equipment was equal to the largest charge of a piece of equipment in that category.  In about half of the end uses, this assumption is true, but for the other half this is a very conservative assumption.  For example, only 10 percent of commercial direct air conditioning equipment has the assumed charge size of 33 kg.  The other 90 percent has a charge of only 10.2 kg, and so the charge size (and thus releases) for 90 percent of commercial direct air conditioning equipment has

	EXHIBIT 7-1
	RESULTS SUMMARY FOR HCFCs AND HFCs

                                  Substitute
                        Highest Exposure Concentration/
                                 RfC Ratio[a]
                              Highest Cancer Risk
                            Associated End Use/Site
HCFC-22
                                   9.7 E-03
                                   7.1 E-06
Central A/C and Home Heat Pumps/Factory
HCFC-123
                                   1.0 E-02
                                   4.3 E-06
High Pressure Centrifugal Chillers/Factory
HCFC-124
                                   1.1 E-03
                                      N/A
Retail Food Stand Alone/Factory
HCFC-141b
                                   2.1 E-04
                                      N/A
Low Pressure Centrifugal Chillers/Factory
HCFC-142b
                                   3.2 E-03
                                      N/A
Refrigerators and Freezers/Factory
HFC-23
                                   8.1 E-02
                                      N/A
Central A/C and Home Heat Pumps/Factory
HFC-125
                                   4.9 E-02
                                      N/A
Central A/C and Home Heat Pumps/Factory
HFC-134
                                   1.0 E-02
                                      N/A
High Pressure Centrifugal Chillers/Factory
HFC-134a
                                   4.9 E-02
                                      N/A
Central A/C and Home Heat Pumps/Factory
HFC-143
                                   1.4 E-03
                                      N/A
High Pressure Centrifugal Chillers/Factory
HFC-143a
                                   6.9 E-03
                                      N/A
Central A/C and Home Heat Pumps/Factory
HFC-152a
                                   9.5 E-03
                                      N/A
Window A/C Units/Salvage Yard
HFC-227ea
                                   1.1 E-02
                                      N/A
Refrigerators and Freezers/Factory

N/A =  Not Applicable

[a]	Some of the RfCs are Agency-verified while others are not.  See Exhibit 3-1 for further information.

            been overestimated.  See Attachment 7-E for a table detailing the charge sizes for the actual equipment versus the assumed charge size for each end use.

      	The number of units manufactured per factory is not tracked by the Vintaging Model, so estimates for this analysis had to be developed.  Data for production rates were based on estimated market shares for the largest manufacturer.  For example, if there are three manufacturers of chillers, it was assumed, based on information from these manufacturers, that the largest manufacturer has 50 percent of the market share and of total annual production.  It was also assumed that this manufacturer's total annual production was manufactured at one factory.  These assumptions will, in many cases, result in an overestimation of the true production (and thus releases) at the actual largest factory.

      	With one exception (low pressure chillers), it was assumed that every piece of equipment is charged (and recovered) at least once in the factory for run testing, although some manufacturers' quality control may include testing only a portion of all equipment sold.

      	It was assumed that the equipment contains its full original charge at the point of service.  In practice, this would rarely be the case since most servicing calls are made after leaking of refrigerant causes the equipment to malfunction.  The effect of this assumption is to overstate releases, since the amount released is a percentage of the charge at the time of servicing.

      	Disposal emissions also assume that a percentage of the total charge is vented at disposal, although this is rarely the case.  As in servicing, a portion of the charge will have leaked before disposal.

      	Reports from manufacturers of certain types of equipment, such as chillers, indicate that refrigerant leakage from operating equipment varies significantly depending on whether the equipment's level of maintenance is poor, average, or above average.  Poor maintenance was assumed in all cases.  An example of the amount of overestimation of releases which this approach could yield can be seen in chillers, of which only five percent to ten percent are generally poorly maintained.

      	The amount of substitute used may not equal the amount of CFC used, due to the use of blends, increased efficiency in newly-built equipment, and the increased cost of the substitutes and the concomitant smaller equipment charge sizes.  Also, some substitutes, such as HCFC-123, are already in use today and are known to be handled very differently from CFCs (i.e., they are handled more carefully).  In the case of HCFC-123, a possible carcinogen, the actual risks will be smaller than those predicted.

B.	Estimating Downwind Concentrations.  Uncertainties associated with derivation of the dispersion factors are discussed by EPA (EPA 1990b).  They include the following:

      	EPA used a generic site location to model downwind concentrations.  The meteorological conditions at this generic site were selected to cause conservative estimates of downwind concentrations.

      	EPA's selection of model parameters characterizing the release (e.g., release height, size of the release facility) were based on professional judgment.

      	Facility fenceline distance estimates (where exposure was simulated to occur) were also assumed by EPA.  For some types of release sites, the model could not estimate concentrations at the assumed fenceline distance because in some cases the distances were as close as 10 meters.  In these cases, the modeled concentrations at the exposure point were based on the highest concentrations predicted, but could be underestimates.

      	The uncertainty faced in selecting dispersion factors to apply to each type of release site is discussed in detail in Attachment 7-C.

C.	Screening Potential Risks.  There are three important caveats associated with the risk calculations:

      	Most of the calculations assume that an exposed individual lives and works in the same zone of concentration 24 hours per day, year-round, throughout a 70-year lifetime.  Although this conservative assumption is often used in risk assessments, it is overly conservative for the HCFCs, which are scheduled to be phased out of production.  To account for the phaseout in HCFC production, it was assumed that equipment manufacturing facilities would stop placing HCFC-22 and HCFC-123 in equipment by 2010 and 2015, respectively.  Therefore, when calculating cancer risk, the duration of exposure to factory releases of these substitutes was shortened to 18 and 23 years, respectively.  A similar adjustment was not made in exposures to operating site releases because the phaseout will not preclude HCFCs from being used in existing equipment for the length of the equipment's lifetime.  However, because the equipment is likely to replaced before 2062  the end of the exposed individual's 70-year lifetime  cancer risks from releases of HCFC-22 and HCFC-123 from operating sites are overestimated in this analysis.

      	Risks from exposure to operating site releases were based on the highest amount of substitute that would be released in any one year (i.e., the sum of releases from equipment operation, servicing, and either installation or disposal).  Because installation and disposal each happen only once over the equipment's lifetime, and servicing typically occurs less frequently than once a year, exposures and risks from operating sites are overestimated.

7.1.4	Conclusions

      Even employing conservative screening assumptions, EPA found that there are no end uses within the refrigeration or air conditioning sectors where the use of HFCs or HCFCs as substitutes for CFCs will result in exposure concentrations above the chemicals' health-based reference concentrations for non-cancer effects.  Similarly, there are no areas for which predicted cancer risks would be above the upper-bound cancer risk level of concern, 10[-5].

7.2	OTHER ALTERNATIVE REFRIGERANTS

      This section discusses the following refrigerant substitutes:  ammonia, butane, isobutane, propane, cyclopropane, perfluoropropane, and dimethyl ether (DME).  After a background discussion, the approach for the analysis and the results are discussed.

7.2.1	Background

      Many of these alternative refrigerants currently find wide use in industrial applications.  Ammonia was one of the first refrigerants to gain acceptance, and is used almost exclusively in the meat packing, dairy, frozen juice, brewery, cold storage, and other food industries.  The hydrocarbon refrigerants are used primarily in oil refineries and chemical plants, where they are frequently available as part of the process stream.  The expanded use of many of the refrigerants in this section in other refrigeration and air conditioning equipment has been proposed, particularly as components in blends with the HFCs and HCFCs.

      Most industrial process refrigeration systems are designed by consulting firms that specialize in the field.  The consultants typically work with the client to determine the exact specifications (cooling loads, for example), then design the system using off-the-shelf or specially- fabricated components.  Smaller, more standard designs, such as those for a cold storage warehouse, are more likely to use off-the-shelf components as these are cheaper and more readily available.  The consultants sometimes supervise construction, installation, and start-up of the refrigeration system.

      Compressors for large industrial process refrigeration systems are built by a handful of companies.  Because they are large, complicated pieces of machinery, compressors are tested at the factory, but for safety purposes testing is not done with the refrigerant that will ultimately be used.  For hydrocarbon refrigerants, run testing is typically done with dry air, and a correlation made with the refrigerant to determine the compressor's operating performance (Shephard 1992).  Ammonia compressors are tested with air and a soap solution or tested under water to see if bubbles appear at joints.  Ammonia package systems (those that have the evaporating and condensing units attached) are similarly tested with an air/soap solution, then charged with dry nitrogen before being shipped (Anderson 1992; Pillis 1992).

      Industrial systems are erected in the field, leak tested again, then charged with the refrigerant.  Care is taken during the charging operation to ensure that vapor concentrations are kept below hazardous levels.  Ammonia systems usually have a charge size that makes them subject to OSHA PEL limits for ammonia (Anderson 1992), while ASHRAE standards for refrigeration systems recognize that worker exposure due to routine operating leakage from the system, or that occurs during servicing, should be kept below threshold levels.  These codes are adopted into local and state building codes in most of the U.S. and are used as guidelines by the system designers.  In all cases, it is unlikely that emissions from a process refrigeration system operating on an industrial refrigerant would exceed those of a similar system operating on CFCs or HCFCs.

7.2.2	Approach

      This analysis of ammonia, butane, isobutane, propane, cyclopropane, perfluoropropane, and DME is a simple screening analysis to determine whether general population exposure is potentially of concern in specific end uses.  The analysis used the fenceline exposure concentrations predicted above for HCFCs and HFCs and assumed that the fenceline concentrations of the alternative refrigerants noted above would be the same.  This is a conservative approach because (1) the HCFC and HFC fenceline concentrations were calculated using conservative assumptions that are likely to overestimate exposure levels, and (2) releases of these alternative refrigerants are likely to be even lower because of the OSHA and ASHRAE standards to which their refrigerant uses are subject.

      Conclusive data on the significance of factory releases were unavailable.  Consequently, to be conservative in the analysis for these alternative refrigerants, factory releases were evaluated in addition to releases on-site during operation and servicing and those at disposal.  The only exception to this approach was for ammonia.  Although compressors for large industrial process refrigeration systems are tested at the factory, for safety purposes this testing is not done with ammonia.  Similarly, charging of ammonia systems is typically performed at the operating site rather than the factory.  Therefore, ammonia is unlikely to be released from a factory setting.

      These fenceline concentrations were then compared to reference concentrations for each of the substitutes.  From Chapter 3, the following reference concentrations were employed:

      Ammonia:		0.1 mg/m[3]		Perfluoropropane:	4.5 mg/m[3]

      Butane:		0.95 mg/m[3] 		Cyclopropane:		0.9 mg/m[3]

      Isobutane:		0.95 mg/m[3]		Dimethyl ether:	0.4 mg/m[3]

      Propane:		0.9 mg/m[3]

7.2.3	Results

      Exhibit 7-2 summarizes the results of the approach described in 7.2.2.  For each end use, the highest exposure concentration (from Attachment 7-D) is shown.  The location of this exposure (i.e., at the factory, on-site, or at the disposal site) is also reported.  For the applicable refrigerants, the ratio of the concentration to the substitutes' reference concentrations is calculated.  None of these ratios exceeded the health-based thresholds.

      Caveats and limitations associated with this analysis are the same as those discussed above for HCFCs and HFCs.  In addition, there is considerable uncertainty associated with the health-based thresholds used for butane, propane, and perfluoropropane, which were extrapolated from workplace exposure limits rather than calculated from laboratory studies.  EPA believes that the exposure limits used in this analysis are conservative.

      Given the conservative nature of the release estimates and interim health-based levels used in this analysis, EPA concludes that general population exposure is not of concern for these seven substitutes.

7.3	CHLORINE

      Chlorine has been proposed as a Class I substitute refrigerant for use in chlorine liquification, a processing step in the manufacture of the chemical.  When chilled below its boiling point, chlorine can be stored as a liquid at atmospheric pressure, a method that for safety reasons is much preferred to storing the chemical as a pressurized gas at ambient temperatures.  Compatibility of the refrigerant with liquid chlorine is critical because of chlorine's high reactivity; CFC-12 is widely used because it is nonreactive.

	EXHIBIT 7-2:  RESULTS SUMMARY FOR OTHER ALTERNATIVE REFRIGERANTS[a]

a Releases are based on the assumption that the refrigerant is not recycled when the equipment is serviced or dismantled for disposal.  This does not reflect common operating practices and therefore overstates true risk.

      Chlorine refrigeration systems generally do not exchange chlorine with the process stream.  However, the system would be placed so that any leakage or losses of chlorine would be contained and neutralized by the process safety mechanisms.  Charge sizes in the refrigeration system would probably be less than 1000 kg, as compared to a bulk storage container havingseveral hundred times that capacity.  Chlorine emissions from the refrigeration system are likely to be dwarfed by those emanating from the process and storage systems, which are already kept small for reasons of worker safety.

      Based on these considerations, EPA does not believe that the use of chlorine as a refrigerant in this limited application  the manufacture of chlorine  poses significant incremental risk to the general population.

7.4	LITHIUM BROMIDE AND AMMONIA IN ABSORPTION SYSTEMS

      Lithium bromide is used in commercial absorption systems, where it serves as an absorbent.  Such systems operate at very low pressure to allow water to act as a refrigerant.  The lithium bromide is in the form of an ionic salt having a negligible vapor pressure, so there is no possibility of a gaseous release in other than catastrophic circumstances.  Lithium is also a relatively nontoxic, nonflammable, nonexplosive, chemically stable chemical, and poses little incremental risk to the general population.

      Absorption refrigeration systems employing a mixture of ammonia and water have been used for many years.  Small refrigeration units are popular in recreational vehicles and hotel refrigerators as they need no electrically-driven mechanical pump.  Domestic absorption type systems use hydrogen to maintain a system pressure high enough to allow the ammonia refrigerant to evaporate at low pressure and temperature (and condense at room temperature), and are  ruggedly constructed; the absorption mechanism itself is a sealed unit, which usually needs no servicing over its operating life.  Commercial ammonia absorption systems are used for air conditioning comfort cooling, particularly in instances where waste heat is available.  These produce chilled water, which is circulated to the space being cooled.  The same standards and guidelines that apply to ammonia vapor compression equipment also apply to commercial ammonia absorption systems.  In a well-maintained system, it is unlikely that ammonia emissions would pose a problem.

	CHAPTER 7 REFERENCES

Anderson, Kent.  1992.  May 5. Phone conversation between Mark Radka, ICF Incorporated, and Kent Anderson, Chairman of the International Institute of Ammonia Refrigeration.

Aucott, Michael.  1990.  December 14.  Feasibility of CFC-12 Reclamation from Salvaged Vehicles.  Department of Environmental Protection, Division of Solid Waste Management, State of New Jersey.

Pillis, J.  1992.  May 5.  Phone conversation between Mark Radka, ICF Incorporated, and J. Pillis, Chief Engineer, The Frick Company.

Shephard, James.  1992.  May 4.  Phone conversation between Mark Radka, ICF Incorporated, and James Shephard, Vice President of Engineering, Lewis Energy Systems, and Chair of the ASHRAE Technical Committee on Custom Refrigeration Systems.

U.S. EPA.  1992.  Regulatory Impact Analysis:  Compliance with Section 604 of the Clean Air Act for the Phaseout of Ozone Depleting Chemicals.  Office of Air and Radiation.  March 12, 1992.

U.S. EPA.  1990a.  External Review Draft, Hydrofluorocarbons and Hydrochlorofluorocarbons, Interim Report.  Office of Toxic Substances.  November, 1990.

U.S. EPA.  1990b.  Potential Ambient Inhalation Exposures for Chlorofluorocarbon Substitutes.  	Office of Toxic Substances.  Exposure Evaluation Division, Exposure Assessment Branch.  November 7, 1990.

U.S. EPA.  1990c.  Revised Draft: Occupational Exposure and Environmental Release Data for Chlorofluorocarbons (CFCs) and Their Substitutes.  Office of Toxic Substances.

	ATTACHMENT 7-A

	DETAILED CATEGORIZATION OF REFRIGERATION END USES
	AND EQUIPMENT TYPES
	("Near-Term" Substitutes In Italics)

1.	Retail Food - Parallel Systems

   	CFC-12 (medium temperature)  	HFC-134a
                                          HCFC-22
                                          HCFC-22/HFC-152a/HCFC-124
                                          HFC-125/HFC-143a/HFC-134a
                                          ammonia

   	CFC-502 (low temperature)   	HFC-125
                                          HFC-143a
                                          HCFC-22
                                          HCFC-22/propane/perfluoropropane
                                          HCFC-22/propane/HFC-125

   	HCFC-22 (medium and low temperature)  	HFC-125
                                          HFC-134a
                                          HFC-23/HFC-134a
                                          HFC-125/HFC-143a
                                          HCFC-22/propane/HFC-125

2.	Retail Food - Stand Alone Systems

   	CFC-12 (medium temperature)   	HFC-134a
                                          HCFC-22
                                          HCFC-22/HFC-152a/HCFC-124
                                          HFC-125/HFC-143a/HFC-134a
                                          ammonia

   	CFC-502 (low temperature)   	HFC-125
                                          HFC-143a
                                          HCFC-22
                                          HCFC-22/propane/perfluoropropane
                                          HCFC-22/propane/HFC-125

3.	Cold Storage Warehouses

   	CFC-12 (medium/high temperature)   	HFC-134a
                                          HFC-152a
                                          HCFC-22
                                          HCFC-22/HFC-152a/HCFC-124
                                          ammonia
                                          turbochill

   	HCFC-22 (medium/high temperature)   	HFC-134a
                                          HFC-152a
                                          HFC-23/HFC-134a

HCFC-22/HFC-152a/HCFC-124
                                          ammonia
                                          turbochill

   	CFC-502 (low temperature)   	HFC-125
                                          HCFC-22
                                          HCFC-22/propane/perfluoropropane        						ammonia

4.	Reciprocating Chillersa

   	CFC-12  	HFC-134a
                                          HFC-152a
                                          HCFC-22
                                          HCFC-123
                                          HFC-125/HFC-143a/HFC-134a

   	HCFC-22 	HFC-134a
                                          HFC-23/HFC-134a
                                          HFC-125/HFC-143a
                                          HCFC-22/propane/HFC-125
                                          ammonia

5.	Screw Chillers[a]

   	HCFC-22   	HFC-134a
                                          HFC-23/HFC-134a
                                          HCFC-22/propane/HFC-125
                                          ammonia

6.	Centrifugal Low Pressure Chillers[a]

   	CFC-11  	HFC-134a
      	HCFC-22
                                          HCFC-123
                                          HCFC-141b
                                          lithium bromide/water absorption
                                          ammonia/water absorption

7.	Centrifugal High Pressure Chillers[a]

   	CFC-12   	HFC-134a
                                          HCFC-22
                                          HCFC-123
                                          lithium bromide/water absorption

   	CFC-114   	HCFC-124
                                          HCFC-142b
                                          R200b
                                          R200c
                                          R200d
                                          R200e
                                          R200f
                                          R200g
                                          R200i
                                          R200j

   	CFC-500   	HFC-134a
                                          HCFC-22/HFC-152a/HCFC-124
                                          HFC-134a/HFC-152a
                                          ammonia

   	HCFC-22   	HFC-134a
                                          ammonia

8.	Industrial Process Refrigeration - Low Pressure Systems

   	Centrifugal Package Systems (CFC-11)   	HCFC-123
                                          HCFC-141b

   	Centrifugal Built-Up Systems (CFC-11)   	HCFC-123
                                          HCFC-141b

9.	Industrial Process Refrigeration - High Pressure Package Systems

   	CFC-12 Reciprocating  	HFC-134a
                                          HFC-143a
   	HCFC-22 Reciprocating	HFC-152a
                                          HCFC-22
   	CFC-502 Reciprocatinga	HFC-23/HFC-134a
                                          HFC-125/HFC-143a
                                          HCFC-22/HFC-152a/HCFC-124
                                          HFC-125/HFC-143a/HFC-134a
                                          HCFC-22/propane/HFC-125
                                          propane
    		butane
                                          ammonia

10.	Industrial Process Refrigeration - High Pressure Built-Up Systems

   	CFC-12 Reciprocating	HFC-134a
                                          HFC-152a
   	HCFC-22 Centrifugal	HCFC-22
                                          HFC-23/HFC-134a
   	CFC-500 Centrifugal	HFC-125/HFC-143a
                                          HCFC-22/HFC-152a/HCFC-124
   	CFC-12 Reciprocating	HFC-125/HFC-143a/HFC-134a
                                          HCFC-22/propane/HFC-125
   	HCFC-22 Reciprocating 	propane
butane
                                          ammonia
                                          chlorine

11.	Ice Skating Rinks

   	CFC-12	HFC-134a
                                          HFC-152a
   	HCFC-22	HCFC-22
                                          HFC-23/HFC-134a
   	CFC-502	HCFC-22/HFC-152a/HCFC-124
                                          ammonia

12.	Medium Ice Makers

   	CFC-12	HCFC-22
                                          HFC-134a
                                          HFC-152a
                                          HCFC-22/HFC-152a/HCFC-124
                                          ammonia

13.	Large Ice Makers

   	CFC-12	HCFC-22
                                          HFC-134a
                                          HFC-152a
                                          HCFC-22/HFC-152a/HCFC-124
                                          ammonia

14.	Refrigerated Transport Units

   	CFC-12   	HFC-134a
                                          HCFC-22
HCFC-22/HFC-152a/HCFC-124
                                          HFC-125/HFC-143a/HFC-134a

   	CFC-500   	HFC-134a
                                          HCFC-22
                                          HCFC-22/HFC-152a/HCFC-124
                                          HCFC-22/propane/HFC-125

   	CFC-502   	HFC-125

                                          HFC-134a
                                          HCFC-22
                                          HCFC-22/propane/HFC-125

15.	Window Air Conditioners

   	HCFC-22   	HFC-125
                                          HFC-134a
                                          HFC-23/HFC-134a
                                          HFC-125/HFC-143a

16.	Central Air Conditioners and Home Heat Pumps

   	Package Terminal Air 	HFC-125
     Conditioners (HCFC-22)			HFC-134a
                                          HFC-23/HFC-134a
   	Residential Unitary Air 	HFC-125/HFC-143a
     Conditioners (HCFC-22)	HFC-125/HFC-143a/HFC-134a
                                          HCFC-22/propane/HFC-125
   	Unitary Heat Pumps (HCFC-22)

   	Water Source Heat Pumps (HCFC-22)

17.	Commercial Direct Expansion Air Conditioning Systems

   	Small Commercial Air 	HFC-125
     Conditioners (HCFC-22)			HFC-134a
                                          HFC-23/HFC-134a
   	Large Commercial Air	HFC-125/HFC-143a
     Conditioners (HCFC-22)

18.	Refrigerators and Freezers

   	Refrigerators (CFC-12)   	HFC-134a
                                          HFC-152a
   	Freezers (CFC-12)	HCFC-22
R200b
                                      	HCFC-22/HFC-152a/HCFC-124
                                          HCFC-22/HCFC-142b
                                          ammonia/water absorption

19.	Other Refrigerated Appliances

   	Dehumidifiers (CFC-12) 	HFC-134a
                                          HFC-152a
   	Vending Machines (CFC-12)	HCFC-22/HFC-152a/HCFC-124

   	Small Ice Makers (CFC-12)	HCFC-22

   	Water Coolers (CFC-12)

   	Small Ice Makers (CFC-502)   	HCFC-22

20.	Mobile Air Conditioners

   	CFC-12   	HFC-134a
                                          HCFC-22/HFC-152a/HCFC-124

	ATTACHMENT 7-B:
	ASSUMPTIONS FOR AMBIENT AIR RELEASE CALCULATIONSa

                              RETAIL FOOD SYSTEMS
                             Type/Site of Release
                               Parallel Systems
                              Stand-Alone Systems
MANUFACTURING RELEASES - FACTORY

   No. of units manufactured per plant per year
                                                                          2,900
       30,000b
   Release per unit manufactured (kg)
                                                                            6.0
                                                                            2.0
ON-SITE RELEASES

   No. of units per site

                                                                              1
                                                                              2
   Release per unit installed (kg)

                                                                             93
                                                                            3.0
   Release per unit serviced (kg)

     without recycling
                                                                            7.7
                                                                             20
     with recycling
                                                                            3.1
                                                                            1.2
     recycling efficiency

                                                                            99%
                                                                            99%
   Release per unit operating (kg/yr)

                                                                            130
                                                                            1.9
   Release per unit disposed (kg)

     without recycling
                                                                            470
                                                                             19
     with recycling
                                                                            4.7
                                                                           0.19
     recycling efficiency
                                                                            99%
                                                                            99%

                            COLD STORAGE WAREHOUSES
                             Type/Site of Release
                            Cold Storage Warehouses
MANUFACTURING RELEASES - FACTORY

   No. of units manufactured per plant per year
                       57a
   Release per unit manufactured (kg)
                                                                             15
ON-SITE RELEASES

   No. of units per site

                        4b
   Release per unit installed (kg)

                                                                            3.5
   Release per unit serviced (kg)

     without recycling
                                                                             52
     with recycling
                                                                            5.0
     recycling efficiency

                                                                            99%
   Release per unit operating (kg/yr)

                                                                             50
   Release per unit disposed (kg)

     without recycling
                                                                            250
     with recycling
                                                                            2.5
     recycling efficiency
                                                                            99%

                                   CHILLERS

                             Type/Site of Release
                                   Recipro-
                                cating Chillers

                                Screw Chillers
                             Centrifugal Chillers

                                 Low Pressure
                                 High Pressure
MANUFACTURING RELEASES - FACTORY

   No. of units manufactured per plant per year
 3,000a
    230b
1,200c
  370[c]
   Release per unit manufactured (kg)
                                                                            5.0
                                                                            5.1
                                                                            16d
                                                                             52
ON-SITE RELEASES

   No. of units per site

                                                                              1
                                                                              1
                                                                              1
                                                                              1
   Release per unit installed (kg)

                                                                            1.1
                                                                            1.1
                                                                            2.0
                                                                            2.0
   Release per unit serviced (kg)

     without recycling
      5.1e
      11[e]
   28[e]
   37[e]
     with recycling
                                                                           0.15
                                                                           0.21
                                                                            1.3
                                                                            1.4
     recycling efficiency

                                                                            99%
                                                                            99%
                                                                            99%
                                                                            99%
   Release per unit operating (kg/yr)

    23f
      54[f]
  110[f]
  260[f]
   Release per unit disposed (kg)

     without recycling
                                                                             73
                                                                            230
                                                                            450
                                                                            900
     with recycling
                                                                           0.73
                                                                            2.3
                                                                            4.5
                                                                            9.0
     recycling efficiency
                                                                            99%
                                                                            99%
                                                                            99%
                                                                            99%

                       INDUSTRIAL PROCESS REFRIGERATION

                             Type/Site of Release
                                 Low Pressure
                             High Pressure Package
                            High Pressure Built Up
                               Ice Skating Rinks
                               Medium Ice Makers

                               Large Ice Makers
MANUFACTURING RELEASES - FACTORY

   No. of units manufactured per plant per year
    32a
      130[a]
  130[a]
     41[a]
50,000b
                                                                           8.0c
   Release per unit manufactured (kg)
                                                                             24
                                                                             13
                                                                            190
                                                                            1.0
                                                                           0.19
                                                                            2.1
ON-SITE RELEASES

   No. of units per site

                                                                              1
                                                                              1
                                                                              1
                                                                              1
                                                                              1
                                                                              1
   Release per unit installed (kg)

                                                                             11
                                                                             11
                                                                             11
                                                                             11
                                                                              0
                                                                           0.68
   Release per unit serviced (kg)

     without recycling
                                                                            140
                                                                             19
                                                                            910
                                                                             28
                                                                            2.3
                                                                             34
     with recycling
                                                                             15
                                                                            2.8
                                                                             10
                                                                            1.3
                                                                           0.05
                                                                           0.68
     recycling efficiency

                                                                            99%
                                                                            99%
                                                                            99%
                                                                            99%
                                                                            99%
                                                                            99%
   Release per unit operating (kg/yr)

                                                                             68
                                                                             27
                                                                          1,800
                                                                             57
                                                                           0.15
                                                                            2.2
   Release per unit disposed (kg)

     without recycling
                                                                            680
                                                                            180
                                                                          9,100
                                                                          1,400
                                                                            2.3
                                                                             34
     with recycling
                                                                            6.8
                                                                            1.8
                                                                             91
                                                                             14
                                                                           0.02
                                                                           0.34
     recycling efficiency
                                                                            99%
                                                                            99%
                                                                            99%
                                                                            99%
                                                                            99%
                                                                            99%

                            TRANSPORT REFRIGERATION

                             Type/Site of Release
                            Transport Refrigeration
MANUFACTURING RELEASES - FACTORY

   No. of units manufactured per plant per year
                14,100a
   Release per unit manufactured (kg)
                                                                            1.0
ON-SITE RELEASES

   No. of units per site

                                                                              1
   Release per unit installed (kg)

                                                                           0.25
   Release per unit serviced (kg)

     without recycling
                                                                            2.0
     with recycling
                                                                           0.02
     recycling efficiency

                                                                            99%
   Release per unit operating (kg/yr)

                                                                           0.20
   Release per unit disposed (kg)

     without recycling
                                                                            8.1
     with recycling
                                                                           0.08
     recycling efficiency
                                                                            99%

                  HOUSEHOLD AND OTHER REFRIGERATED APPLIANCES

                             Type/Site of Release

                               Window A/C Units

                       Central A/C & Home Heat Pumps
                        Commercial Direct Expansion A/C
MANUFACTURING RELEASES - FACTORY

   No. of units manufactured per plant per year
300,000a
  400,000[a]
   38,600b
   Release per unit manufactured (kg)
                                                                           0.05
                                                                           0.23
                                                                           0.33
ON-SITE RELEASES

   No. of units per site

                                                                              1
                                                                              1
                                                                              1
   Release per unit installed (kg)

                                                                              0
                                                                              0
                                                                             11
   Release per unit serviced (kg)

     without recycling
                                                                            1.8
                                                                            3.8
                                                                             33
     with recycling
                                                                           0.04
                                                                           0.08
                                                                           0.66
     recycling efficiency

                                                                            99%
                                                                            99%
                                                                            99%
   Release per unit operating (kg/yr)

                                                                           0.38
                                                                           0.80
                                                                            6.9
   Release per unit disposed (kg)

     without recycling
                                                                             NA
                                                                            3.8
                                                                             33
     with recycling
                                                                             NA
                                                                           0.04
                                                                           0.33
     recycling efficiency
                                                                             NA
                                                                            99%
                                                                            99%
DISPOSAL RELEASES - RECYCLING/SALVAGING CENTER

   No. of units processed per site per year
  26,000c
                                                                             NA
                                                                             NA
   Release per unit processed (kg)

     without recycling
                                                                            1.8
                                                                             NA
                                                                             NA
     with recycling
                                                                           0.02
                                                                             NA
                                                                             NA
     recycling efficiency
                                                                            99%