## RISK ASSESSMENT FOR ALTERNATIVE REFRIGERANT HFO-1234yf

PREPARED FOR:

SAE INTERNATIONAL Cooperative Research Program 1234

PREPARED BY:

GRADIENT CORPORATION 600 Stewart Street Seattle, WA 98101



### February 26, 2008 (Original Report Date) April 3, 2009 (General Release Date)G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### Table of Contents



## Executive Su mmary............................................................................................................ vi

1 Introduction .............................................................................................................. 1 1.1 European Union F-Gas Regulation..................................................................................... 1 1.2 U.S. EPA Significant New Alte rnatives Program (SNAP)................................................. 1 1.3 U.S. EPA Sponsored Risk Assessment of R-152a and R-744 (CO 2 

### ).................................. 2 1.4 SAE Cooperative Research Program (CRP) 150................................................................ 3 1.5 SAE Cooperative Research Program 1234 (CRP1234)...................................................... 3



## 2 Conducting Risk Assessment for A lternative Refrigerants...................................... 5 2.1 Approach....................................................................................................................... ...... 5 2.2 Evaluating Potential AR Toxicity....................................................................................... 6 2.2.1 Criteria for Evaluating Manufacturer-Supplied Toxicity Data.............................. 6 2.2.2 Acute Toxicity ....................................................................................................... 7 2.2.2.1 Acute Toxicity - Lethality...................................................................... 7 2.2.2.2 Anesthetic Potency................................................................................. 8 2.2.2.3 Cardiac Sensitization.............................................................................. 9 2.2.3 Subacute, Sub-Chronic and Chronic Toxicity (Repeated Dose Studies)............. 12 2.2.4 Genotoxicity ........................................................................................................ 12 2.2.5 Carcinogenesis..................................................................................................... 13 2.2.6 Reproductive/Developmental Toxicity................................................................ 13 2.2.7 Ecotoxicity........................................................................................................... 14 2.2.8 Toxicity Criteria Used for Risk Assessment........................................................ 15 2.3 Evaluating Flammability of ARs ...................................................................................... 17 2.3.1 Relevant Flammability Properties........................................................................ 18 2.4 Exposure A ssessment........................................................................................................ 19 2.4.1 Passenger Compartm ent Scenario........................................................................ 20 2.4.2 Potential AR Concentrations in Vehicle Passenger Compartment ...................... 21 2.4.2.1 CFD Modeling ..................................................................................... 21 2.4.2.2 Field Testing ........................................................................................ 22 2.4.3 Potential AR Concentrations After a Leak in the Engine Compartment ............. 23 2.4.4 Potential AR Concentrations Associat ed with Leaks in Vehicle Repair Areas .................................................................................................................... 24 2.4.4.1 Professional Service Technician Scenario ........................................... 25 2.4.4.2 DIY Scenarios ...................................................................................... 27 2.5 Risk Character ization........................................................................................................ 29 2.5.1 Health Risks for Passengers a nd Vehicle Repair Workers .................................. 29 2.5.2 Ignition Risks for Passengers and Vehicle Repair Workers ................................ 30 2.5.3 Ecological Risks .................................................................................................. 30 2.5.4 Risks for Other Exposure Scenarios .................................................................... 31 2.6 Fault Tree Analysis for Evaluating Potential Risks.......................................................... 32 2.6.1 Fault Tree Assumptions for Passenger Compartment Scenario........................... 33 2.6.1.1 Fault Tree Assumptions Related to Health Risks for Vehicle Passengers ............................................................................................ 33 2.6.1.2 Fault Tree Assumptions Related to AR Ignition Risks for Vehicle Passengers............................................................................... 35 2.6.2 Fault Trees for Engine Compartment AR Ignition Scenario ............................... 38G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### 2.6.3 Fault Trees for Vehicle Repair Scenarios ............................................................ 39 2.6.3.1 Fault Trees Related to Health Risks for Vehicle Repair Workers........ 39 2.6.3.2 Fault Trees Related to AR Ignition Risks for Vehicle Repair Workers................................................................................................ 40 2.6.4 Interpretation of FTA Results .............................................................................. 41 2.7 Sources of Uncertainty in the Risk Assessment................................................................ 42



## 3 Summary of R-12 Risk Assessment....................................................................... 44 3.1 General Properties............................................................................................................. 44 3.2 Toxicity A ssessment ......................................................................................................... 45 3.2.1 Summary of Toxicological Findings ................................................................... 45 3.2.2 Toxicity Criteria Used for Risk Assessment........................................................ 48 3.3 Results of Expos ure Assessment ...................................................................................... 48 3.4 Risk Character ization........................................................................................................ 49 3.5 FTA............................................................................................................................ ....... 50 3.6 Conclusions Regarding R-12 ............................................................................................ 51



## 4 Risk Assessment – HFO-1234yf ............................................................................ 52 4.1 General Properties............................................................................................................. 52 4.2 Toxicity A ssessment ......................................................................................................... 52 4.2.1 Evaluation of Available Toxicity Data from Manufacturer................................. 52 4.2.3 Summary of Toxicological Findings ................................................................... 54 4.2.4 Toxicity Criteria Used for Risk Assessment........................................................ 56 4.3 Flammability Properties.................................................................................................... 56 4.4 Results of Expos ure Assessment ...................................................................................... 57 4.4.1 Results for Passenger Compartment Scenarios – CFD Modeling ....................... 57 4.4.2 Results for Passenger Compartment Scenarios – Field Measurements ............... 59 4.4.3 Results for Engine Compartment AR Ignition Scenario – Field Measurement........................................................................................................ 60 4.4.4 Results for Repair Worker Scenarios – Perfect Mixing Model ........................... 60 4.5 Risk Character ization........................................................................................................ 61 4.5.1 Health Hazard Indices for HFO-1234yf for Passenger Compartment and Repair Worker Scenarios ..................................................................................... 61 4.5.2 Ignition Risks for HFO-1234yf for Passenger Compartment, Engine Compartment and Repair Worker Scenarios ....................................................... 63 4.5.3 Ecological Risks .................................................................................................. 65 4.5.4 Potential Risks to Other Receptors ...................................................................... 66 4.5.5 Degradation Products........................................................................................... 67 4.6 FTA............................................................................................................................ ....... 68 4.6.1 Toxicity FTAs...................................................................................................... 68 4.6.2 Flammability FTAs.............................................................................................. 68 4.6.3 Comparative Risks............................................................................................... 69 4.7 Conclusions Regarding HFO-1234yf ............................................................................... 70



## 5 References .............................................................................................................. 72G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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## LIST OF TABLES

Table 1 LC 50 

### s of Select Refrigerants Table 2 Anesthetic Concentrations of Select Refrigerants Table 3 Results of Cardiac Sensitization Studies for Different Fluorocarbons Table 4 Inputs for Passenger Scenario Fault Trees Addressing Health Effects – Normal Operation Table 5 Inputs for Passenger Scenario Fault Tr ees Addressing Health Effects – Collision Scenario Table 6 Inputs for Passenger Scenario Fault Trees Addressing Flammability Table 7 Inputs for Passenger Scenario (Collision) Fault Trees Addressing Flammability Table 8 Inputs for Engine Compartment Scenario Fault Trees Addressing Flammability Table 9 Generic Inputs for Repair Worker Fault Trees Addressing Health Effects Table 10 Generic Inputs for Repair Worker Fault Trees Addressing Flammability Table 11 Summary of Available Toxicity Data for R-12 Table 12 Comparison of Toxicity of R-12 to the Toxicity of R-134a Table 13 Passenger Modeling Scenarios for R-12 Evaluation (R-12 Simulation Key) 

### Table 14 Predicted Passenger Compartment R-12 Concentrations Table 15 Results of Air Modeling for Repair Worker Scenarios, R-12 

### Table 16 Hazard Indices Associated with Di fferent Exposure Scenarios, R-12 

### Table 17 Summary of Available Toxicity Data for HFO-1234yf Table 18 Comparison of Toxicity of HFO-1234yf to the Toxicity of R-134a Table 19 Flammability of HFO-1234yf Relative to Other Refrigerants Table 20 CFD Modeling Scenarios Table 21 Results of Air Modeling Simulations for Passenger Scenarios, HFO-1234yf Table 22 Results of Field Measurements for Passenger Compartment Scenarios, HFO-1234yf Table 23 Results of Air Modeling for Repair Worker Scenarios, HFO-1234yf Table 24 Hazard Indices Associated with Passenger Exposure Scenarios, HFO-1234yf Table 25 Hazard Indices Associated with Vehicle Repair Scenarios, HFO-1234yf Table 26 Ignition Risk Associated with Passenger Compartment Scenarios, HFO-1234yf Table 27 Ignition Risk Associated with Passenger Compartment Scenarios, HFO-1234yf Table 28 Ignition Risk Associated with Repair Scenarios, HFO-1234yf Table 29 Ecological Toxicity Data for Selected Chemicals Compared to HFO-1234yf Table 30 Acute Exposure Limits fo r Fluorocarbon Decomposition Products Table 31 Risks of Injury or Fatality from Various Events Compared to Risks Associated with Leaks of HFO-1234yfG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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## LIST OF FIGURES

Figure 1 Example Fault Tree Figure 2 R-12 Fault Tree – Summary Figure 3 R-12 Fault Tree – Small Leak Scenario Figure 4 R-12 Fault Tree – Medium Leak Scenario Figure 5 R-12 Fault Tree – Large Leak Scenario Figure 6 R-12 Fault Tree – Collision Scenario Figure 7 R-12 Fault Tree – Vehicle Repair Scenarios Figure 8 Aggregate risk of potentially adverse exposure due to HFO-1234yf releaseFigure 9 Fault tree describing risk of potentially adverse exposure associated with a small HFO1234yf leak into passenger compartmentFigure 10 Fault tree describing risk of potentially adverse exposure associated with a medium HFO1234yf leak into passenger compartment Figure 11 Fault tree describing risk of potentially adverse exposure associated with a large HFO1234yf leak into passenger compartment Figure 12 Fault tree describing risk of potentially adverse exposure associated with a HFO-1234yf leak due to vehicle collision Figure 13 Fault tree describing risk of potentially adverse exposure associated with a HFO-1234yf leak during vehicle repair Figure 14 Aggregate ignition risk due to HFO-1234yf release Figure 15 Fault tree describing ignition risk asso ciated with a small HFO-1234yf leak into passenger compartment Figure 16 Fault tree describing ignition risk associated with a medium HFO-1234yf leak into passenger compartment Figure 17 Fault tree describing ignition risk asso ciated with a large HFO-1234yf leak into passenger compartment Figure 18 Fault tree describing ignition risk asso ciated with a HFO-1234yf leak in passenger compartment caused by collision Figure 19 Fault tree describing ignition risk associated with a HFO-1234yf leak in engine compartment Figure 20 Fault tree describing ignition risk associated with a HFO-1234yf leak during vehicle repair by professional service technicians Figure 21 Fault tree describing ignition risk associated with a HFO-1234yf leak during vehicle repair by DIYersG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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## LIST OF ATTACHMENTS

Attachment A Ignition Source Table Attachment B Modeling Results for Repair Worker Scenarios: R-12 Attachment C Modeling Results for Repair Worker Scenarios: HFO-1234yf Attachment D List of Technical Terms and Acronyms Used in the Risk AssessmentG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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## Executive Summary

Due to concerns about global warming, the use of refrigerant R-134a ( i.e. , 1,1,1,2- tetrafluoroethane), will be banned for air conditioni ng systems for new vehicle platforms throughout the European Union (EU) on January 1, 2011. Use of R- 134a will be banned in the EU for all new vehicles by January 1, 2017 (European Fluorocarbon Technical Committee, 2007). Regulations developed by the European Union require that any refrigerant(s) intended to replace R-134a have a global warming potential less than or equal to 150 based on a 100-year time horizon. The replacement(s) will also have to be acceptable in terms of human and ecological toxi city, environmental effects, effectiveness, and compatibility with other air conditioning components. No regulatory scheme equivalent to that adopted by the EU exists in the U.S. or Japan, but the global automobile market creates an incentive for each manufacturer to use a single refrigerant for all ve hicle designs. Because the automotive companies are already engaged in design for the 2011 model year, the evaluation and selection of an alternative refrigerant (AR) involves considerable urgency.

To assist member companies with selection of a R-134a replacement, the Society of Automotive Engineers (SAE), in co-operation with E.I. du P ont de Nemours and Company (DuPont) and Honeywell International (Honeywell), has undertaken an evaluati on of the DuPont/Honeywell alternative refrigerant 2,3,3,3-Tetrafluoropropene (HFO -1234yf, IUPAC nomenclature). 1 

### The evaluation is intended to address risks to passengers and potential vehicle repair wo rkers based on toxicology and flammability data

obtained for this chemical.

The current risk assessment follo ws the approach of the U.S. EPA-sponsored risk assessment of R-152a and R-744 (CO 2 

### ) (Blackwell et al ., 2006) so as to employ a consis tent methodology and generate a product familiar to regulatory agencies. The appro ach is also consistent with a more recent risk assessment of other ARs prepared by Gradient for SAE Cooperative Research Project (CRP) 150 (Gradient, 2008). In a number of cases, the current risk assessment also considers additional scenarios or input values which are believed to provide a more r obust or realistic estimate of passenger or repair

worker risks.

1 ASHRAE is currently reviewing a proposal to accept the refri gerant designation nomenclature for this hydro-fluoro-olefin (HFO) as R-1234yf. In this report, we will use the Du Pont/Honeywell recommended designation of HFO-1234yf for this chemical.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### The SAE CRP150 risk assessment was initially conducted using R-12 as a study example, both to resolve any questions about risk assessment methodology and to provide a comparison for the actual ARs.

The R-12 section of the SAE CRP150 risk assessment has been carried forward into the present risk assessment to provide a similar frame of reference. However, because R-12 is non-flammable, the R-12 risk assessment only addressed health risks. Air modeli ng for the R-12 analysis indicated that passengers could be exposed to R-12 concentra tions above health-based limits in th e event of a large leak while the vehicle was operated in recirculation mode. The results also suggested exposures above health-based limits in the event of a vehicle collision although this was not explicitly modeled. For all other scenarios evaluated (involving vehicle passengers and vehicle repa ir personnel), the predicted air concentrations did

not exceed the health-based limits. Wh en these findings were incorporated in a fault tree analysis (FTA), Gradient estimated that in both Europe and the U.S ., use of R-12 as an automotive refrigerant could result in 11 exposures per year above health-based limits (equi valent to 1 such exposure every 50 years). This is less than or equal to the level of risk tolera ted by the general public with many commonly accepted activities ( e.g. , airplane travel, riding in elevators).

The risk assessment for HFO-1234yf incorporated various types of data including toxicity data, vehicle design and use characteristics, bench scale testing results ( i.e ., flammability metrics), modeled air concentrations (vehicle cabin concen trations), and vehicle measurements ( i.e ., measurements of vehicle cabin and engine compartment concentrations and sub sequent ignition tests). These data were generated by CRP1234 members. Toxicity testing reports were re viewed by a Gradient toxicologist in order to confirm the appropriateness of the methodology employed and to verify the reported health effect levels.

All other data that we received from CRP1234 team me mbers were assumed to be accurate and complete for the purposes of the risk assessment.

The DuPont/Honeywell AR, HFO-1234yf, offers equi valent or lower toxicity compared to R134a or R-12 in terms of both human health effects and ecological effects. The material also has an ozone depletion potential (ODP) of 0 and a global warm ing potential (GWP) of 4 based on a 100-year time horizon, which meets the European Union F-gas requi rements. HFO-1234yf is considered flammable (by definitions applied to mobile air-conditioning systems i.e ., ASTM E681-01, E681-85, etc.), although testing conducted by DuPont and Honeywell indicates th e ignition potential of this chemical is far less than that of other flammable refrigerants ( e.g., R-152a, which is also considered flammable using the same definitions). Nonetheless, due to the fla mmability of HFO-1234yf, the risk assessment addressed both health effects and potential ignition risks for this chemical.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### Based on a review of toxicity data developed by the manufacturers as well as the results of air modeling to predict exposure concentrations, poten tial HFO-1234yf exposures of vehicle passengers in the event of small, medium and large system leaks are expected to be below levels associated with potential health risk. Similarly, HFO-1234yf expos ures of vehicle repair workers (both professional technicians and do-it-yourselfers) are expected to be be low levels associated with potential health risk. In the event of a vehicle collision and refrigerant release, air concentrations could potentially exceed healthbased limits. However, the health-based limit for acute exposure used in this risk assessment for exposures involving stress, such as a collision, was 120,000 ppm. This is approximately four times the

concentration measured in a test vehicle after re lease of HFO-1234yf in a large (0.5 mm) leak. In addition, the frequency of collision related releases is quite small and results in a very low overall

estimate of health risk. Across the entire vehicle fl eet in Europe or the U.S., use of HFO-1234yf could result in 0.02 exposures per year above limits protec tive of human health for acute exposures. This frequency is equivalent to 1 such exposure every 50 years. This level of risk is several orders of magnitude less than the comparable risks estimated for R-12. The estimated level of health risk associated with use of HFO-1234yf as an AR is also subs tantially less than the level of risk tolerated by the general public as part of every day life and less than the risk inherent in many commonly accepted activities ( e.g. , airplane travel, riding in elevators).

Potential ignition hazards of HFO-1234yf were evaluated though both CFD modeling and field testing. Together, these evaluations suggested a lack of ignition risk in the event of small, medium or large leaks into the passenger cabin or leaks in repair worker areas. Consideration of the large leak data suggests that an HFO-1234yf release associated with a severe vehicle collision could potentially result in passenger compartment concentrations which could pose an ignition risk. However, data from laboratory experiments suggest that the flame stability and propa gation potential in such an event would be very limited. In addition, the frequency of this event is expected to be extremely small, amounting to 0.004 events per year across the entire vehicle fleet in eith er the U.S. or Europe (equivalent to 1 such event every 250 years). CRP1234 also evaluated potential ignition risks from leaks of HFO-1234yf in the engine compartment via vehicle testing. The results of this study indicated that concentrations of HFO1234yf could be detected in the flammable range in highly conservative field conditions. However, an attempt to ignite HFO-1234yf after a release in th e engine compartment was unsuccessful. Additional testing by CRP1234 to support this finding is now underway.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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## 1 Introduction

1.1 European Union F-Gas Regulation

On June 14, 2006, the F-Gas Regulation and Mobile Air Conditioning (MAC) Directive were published in the official journal of the European Uni on. The objective of these regulations is to contain, prevent, and thereby reduce emissions of fluorinat ed greenhouse gases covered by the Kyoto Protocol. The measures became effective as of July 4, 2007. The F-gas regulation covers the use of hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and SF 6 

### (sulfur hexafluoride) in all their applications, except Mobile Air Conditioning, whic h is covered by the MAC Directive (European Fluorocarbon Technical Committee, 2007).

The MAC Directive covers the use of HFCs in Mobile Air Conditioning for passenger cars only (Directive 2006/40/EC). The main objectives of the Di rective are the control of leakage of certain fluorinated greenhouse gases with a global warming potential (GWP) higher than 150 in MAC systems and the prohibition of MAC systems using those gases after a certain date (Kozakiewicz, 2007). R-134a will be banned for air conditioning systems for new ve hicle models by January 1, 2011, and for all new vehicles by January 1, 2017 (European Fluorocar bon Technical Committee, 2007). No equivalent regulatory scheme exists in the U.S. or Japan, but the global automobile mark et creates an incentive for each manufacturer to use just one refrigerant for all vehicle designs.



## 1.2 U.S. EPA Significant New Alternatives Program (SNAP)

Section 612 of the U.S. Clean Air Act (CAA) requires the U.S. Environmental Protection Agency (EPA) to establish a program to identify alterna tives to Class I (CFCs, halons, carbon tetrachloride, methyl chloroform, methyl bromide, and HBFCs) and Class II (HCFCs) ozone-depleting substances and to publish lists of acceptable and unacceptable substitu tes. U.S. EPA implements these requirements through the Significant New Alternatives Policy (SNAP ) Program. The purpose of the program is to allow a safe, smooth transition away from ozone-d epleting compounds by identifying substitutes that

offer lower overall risks to human health and the e nvironment. SNAP evaluates substitutes for ozonedepleting compounds in a number of industrial sect ors including the automotive industry. Although R134a is not an ozone depleting subs tance, U.S. EPA will have jurisdiction over the evaluation of the R134 replacements because these chemicals are, in term s of the regulations, substitutes for R-12 as well asG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### R-134a. Substitutes are reviewed based on their e ffects on human health and the environment, and assessed based on the potential for human exposure, toxi city, flammability, ozone depletion, impact on global warming, and other environmental effects. The final rulemaking describing the process for administering the SNAP program and issuing the fi rst acceptability lists for substitutes was published on March 18, 1994. Under the rule it is illegal to repl ace a Class I or Class II substance with any substitute which U.S. EPA determines may produce adverse effects on human health or the environment where

other substitutes have been identified that reduce ove rall risk and are currently or potentially available (U.S. EPA, 2007).



## 1.3 U.S. EPA Sponsored Risk Assessment of R-152a and R-744 (CO 2 

## )

Blackwell et al . (2006) presented a risk assessment for alternative MAC systems employing either R-152a (1,1-difluoroethane) or R-744 (CO 2 

### ). The risk assessment was sponsored by U.S. EPA, the Australian Greenhouse Gas Office; the European Commi ssion; the Japanese Ministry of Environment; the Japanese Ministry of Economy, Trade and Industry; and Environment Canada. In order to examine these risks, U.S. EPA identified AR release scenarios with the highest risks of an adverse outcome. These scenarios were the potential for a moderate to large l eak into the passenger compartment, and the potential for technicians to be exposed during vehicle AC system service. For R-152a, unacceptable exposures were defined as those exposures above 3.5% in air, which is slightly less than the lower flammability

limit of 3.7%. Potential toxic effects of R-152a were not addressed because the thresholds for these effects are above the lower flammability limit. For CO 2 

### , unacceptable exposures were defined as those above 4% for a period of an hour, or above 6% for exposures of one to two minutes or more. 2 

### These levels were selected because human exposure to CO 2 

### at and above these levels can reduce a driver’s capacity to handle a vehicle in a safe manner. Com putational fluid dynamic (CFD) modeling simulated a

reasonable worst-case scenario leak into the passenger compartmen t and the potential for passenger exposures. The simulated exposure con centrations were then used in a fault tree analysis to estimate and broadly quantify the potential for passenger exposure and technician exposure in a range of scenarios.

Taken together, the fault tree analysis and the CFD consequence modeling indicated that a

reasonable worst-case scenario leak for both R-152a and CO 2 

### systems resulted in unacceptable exposures to vehicle occupants. For R-152a, U.S. EPA estimated 50 events per year where flammable

2 In the September 21, 2006 SNAP notice concerning the use of CO 2 as a mobile air conditioning refrigerant, U.S. EPA stipulated an exposure limit of 3% averaged over 15 minutes (Federal Register, Vol. 71, No. 183). The 3% concentration limit i s identical to the National Institute for Occupational Safety and Health (NIOSH) recomme nded exposure limit (REL) for CO 2 and the American Conference of Governmental Industrial Hygienists (ACGIH) short- term exposure limit (STEL).G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### concentrations of R-152a might be present in the passenger compartment along with an ignition source. U.S. EPA also estimated 1,600 events per year wh ere flammable concentrations of R-152a might be present in repair areas along with an ignition source. For CO 2 

### , U.S. EPA estimated 4,300 passenger exposures per year above the health-based limit and 2,400 repair worker exposures above the healthbased limit. 3 

### The authors found that proper engineering to reduce the amount of refrigerant that can leak into the passenger compartment would reduce estimat ed exposures to acceptable levels. For example, a directed release system (squib valve) where the re frigerant charge is released outside the passenger compartment in the event of a large leak was modeled and shown to effectively reduce potential passenger exposure to below levels of concern for both CO 2 

### and R-152a. Other risk mitigation strategies

were also described.



## 1.4 SAE Cooperative Research Program (CRP) 150

The Society of Automotive Engineers (SAE), in conjunction with the German Association of the Automotive Industry (VDA), requested that Gradient Corporation (Gradient) conduct a risk assessment of alternative refrigerants from several different ch emical manufacturers (SAE CRP150). An assessment of potential risks associated with the use of R-12 as an automotive refrigerant was also included as a

baseline evaluation. The risk assessment followed th e approach of the U.S. EPA-sponsored risk assessment of R-152a and R-744 (Blackwell et al ., 2006) so as to allow comparison with the risks from the other alternatives. In a number of cases, the SAE CRP150 risk assessment also considered additional scenarios or input values which were believed to provi de a more robust or realistic estimate of passenger

or worker risks. Because the ri sk assessment included proprietary information from a number of chemical manufacturers, the details of the SAE CRP150 risk assessment remain confidential to CRP150 members. However, because the R-12 evaluation did not involve proprietary information, the R-12 portion of the CRP150 risk assessment is included in this report.



## 1.5 SAE Cooperative Research Program 1234 (CRP1234)

The SAE, in conjunction with E.I. DuPont de Nemours and Company (DuPont) and Honeywell International Inc. (Honeywell), is undertaking an additional risk assessment of a new AR, HFO-1234yf.

3 Note that the results of U.S. EPA’s analysis of R-152a and CO 2 cannot be directly compared to the results of the CRP150 and CRP1234 analyses due to some differences in fault tree parameters . In addition, U.S. EPA assumed that all repair worker exposures would be above concentrations of concern and did not conduct modeling to c onfirm that this was the case. Modeling for repair worker exposures in CRP150 and CRP1234 consistently indicated exposures were below concentrations of concern.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### This current risk assessment generally follows the approach used in the U.S. EPA-sponsored risk assessment of R-152a and R-744 (Blackwell et al ., 2006) and the assessment conducted for CRP150. This facilitates comparison with the risks determined for the other alternatives. In a number of cases, the

most recent SAE risk assessment also considers additional scenarios ( i.e., those associated with material flammability) or input values which are believed to provide a more robust or realistic estimate of passenger or worker risks. The details of this assessm ent are described in the following sections of this report. It should be noted that the risk assessment for HFO-1234yf incorporated various types of data including toxicity data, vehicle design and use characteristics, bench scale testing results ( i.e ., flammability metrics), modeled air concentrations, and vehicle measurements ( i.e ., measurements of vehicle cabin and engine compartment concentrations and subsequent ignition tests). These data were generated by CRP1234 members. Toxicity testing reports were reviewed by a Gradient toxicologist in order to confirm the appropriateness of the methodology employed and to verify the reported health effect

levels. All other data that we received from CRP 1234 team members were assumed to be accurate and complete for the purposes of the risk assessment.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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## 2 Conducting Risk Assessment for Alternative Refrigerants

2.1 Approach

Like all risk assessments, the risk assessment of a potential AR is a multi-step process in which different types of data are reviewed and then brought together to develop a mathematical estimate of potential health risk. The risk assessment procedure employed in this evaluation consisted of the following steps:

1. A review of toxicity studies sponsored by the AR manufacturers to ensure they were conducted appropriately. Our review include d evaluating the study design, the results, any deviations noted from the study protocol , and the conclusions drawn by the testing laboratory from the data.

2. Determining the most significant toxicological effects for potential AR exposures, the levels at which these occur, and any human health criteria related to these effects, including any safety factors considered to be necessary.

3. An evaluation of ecological toxicity data in the context of limits developed by regulatory agencies for classifying chemicals of ecological concern.

4. Based on the available toxicity data, an eval uation of the absolute toxicity as well as the relative toxicity of the AR compared to R-134a, the refrigerant to be replaced. The toxicity relative to R-134a is expected to be a criterion used by U.S. EPA in their SNAP evaluation.

5. An assessment of the flammability of the potential AR, including determining the upper and lower flammable limits, the minimum ignition energy, the autoignition temperature, and the fundamental burning velocity.

6. An assessment of potential concentrations in th e event of an AR release in the passenger compartment, engine compartment, or vehicle repair areas.

7. Estimation of probabilities of specific risks (toxicological and flammability-related) from AR releases through the use of fault tree analys is (FTA). The risks of the proposed ARs were then compared to the risks that would be expected from the use of R-12.

8. A qualitative evaluation of the potentia l risks of AR breakdown products.

9. A characterization of risks in the context of other commonly encountered life events which may involve adverse effects.

Methods and issues related to each stage of the ri sk assessment process are descr ibed in generic form below. The specific assessment of individual ARs is then described in successive chapters of this report.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### This approach was taken so that proprietary info rmation can be readily removed from the report in case distribution of the methodology outside CRP1234 is desired.



## 2.2 Evaluating Potential AR Toxicity

Potential AR toxicity is a primary considera tion for the evaluation. There are a number of toxicological tests that are employed, each of which relates to a different type of toxicological endpoint. These are described below. The goal of these studies is to define a No Observed Adverse Effect Level (NOAEL), a dose that did not produce any observable indications of toxicity. In some instances, a Lowest Observed Adverse Effect Level (LOAEL) is also defined. A LOAEL may be important in cases where the experiment did not include a dose at which no toxicological effects were observed or where it is useful to understand the margin of safety between the NOAEL and LOAEL. Note that because only discrete doses are tested in these experiments, the "t rue" no effect level may be between the observed

NOAEL and the LOAEL.

2.2.1 Criteria for Evaluating Manufacturer-Supplied Toxicity Data

Valid data on the toxicity of the potential AR ar e critical to the risk assessm ent. To ensure that the available toxicity data for the AR were of accep table quality, Gradient obtained laboratory test reports from the chemical manufacturers (or published studies wh ere relevant) for each toxicological endpoint of

interest. Gradient then reviewed the study reports for the following elements:

1. Gradient considered each contract laboratory i nvolved in terms of their reputation for producing quality data and their ability to carry out the work described.

2. Gradient reviewed each study report in detail, including the methods employed, the results (both as summarized in text and in tabular form), th e conclusions drawn from the data, any notes of deviations from the established study protocol, and all report backup such as measurements of exposure concentrations.

3. Gradient ensured that the study used standard met hods (if such exist) or if the methods used were non-standard, that the rationale for their use w as sound and was not simply intended to produce a

more favorable outcome.

4. Overall, Gradient considered the completeness of the assembled data pack age to ensure that it fully addressed all questions about the poten tial toxicity of the proposed refrigerant.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 7 Gradient CORPORATION 

### The following sections describe the types of toxi city data evaluated, indicate how these endpoints are studied, and give some background information on th e relevant toxicity of existing refrigerants.

2.2.2 Acute Toxicity

Acute toxicity describes the adverse effects of a substance which result either from a single exposure or from multiple exposures in a short space of time (usually less than 24 hours). It suggests the possible risk levels for the consequences of accidental releases, such as from a spill or rupture. To be described as acute toxicity, the adverse effects should be noticeable within 14 days of the administration of the substance. Because it is generally unethical to test for acute (or chronic) toxicity in humans, most acute toxicity data are obtained from animal testing. Some acute toxicity data also come from studies of accidental human exposures.

2.2.2.1 Acute Toxicity - Lethality

A key measure of acute toxicity is the median lethal concentration (LC 50 

### ), which is the

concentration that is lethal to half of the test animals, typically during a 4-hour exposure (OECD Test

Method 403 4 

### ). It is a very gross measure of toxicity but is often the first test conducted in order to establish the appropriate doses in more extended studies. LC 50 

### s for refrigerants are generally very high ( i.e. , indicating a relatively low toxicity). Table 1 shows LC 50 

### s for several refrigerants. For comparison, the 4-hr LC50 for the common industrial solvent xylene (found in paints and adhesi ves) is reported to be 5,000 ppm in the rat.

4 The Organization for Economic Cooperation and Development (OECD) has published a list of standard test protocols for evaluating product chemistry and toxicity. The full list of tests can be found at www.oecd.org/department/0,3355,en_2649_34377_1_1_1_1_1,00.htmlG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 8 Gradient CORPORATION Table 1. LC 50 s of Select Refrigerants 

### Haloalkane LC 50 

### (ppm) b 

### Source R-12 >600,000; 800,000 (2-h) Ritchie et al ., 2001 R-23 663,000 Tsai, 2005 R-32 520,000 Tsai, 2005 R-113 110,000 (rats); 95,000 (mice) (2-h) Trochimowicz et al

., 1988 R-123 32,000 Trochimowicz, 1993 R-124 262,500 Trochimowicz, 1993 R-125 800,000 Tsai, 2005 R-134a 567,000 Ritchie et al ., 2001 R-152a 383,000 Tsai, 2005 R-227ea 789,000 Tsai, 2005 R-236ea 85,000 Tsai, 2005 R-236fa 457,000 Tsai, 2005

a Based on 4-hour exposure unless otherwise noted. b Some of these values are considered approximate LC 50 s. ppm = parts per million.



### All of the refrigerants identified above are haloalkanes ( i.e. , compounds containing only single bonds). Acute lethality data for fluoroalkenes (that is, fl uorinated hydrocarbons containing at least one double bond) are more limited than data for fluoroalkanes. Data are publicly available for one fluoroalkene, hexafluoropropene. The LC50 for hexa fluoropropene has been reported to be in the range of 1,800 to 3,000 ppm for rats and 750 ppm for mice (IUCLID database, 2007).

2.2.2.2 Anesthetic Potency

An anesthetic effect is the impairment of th e ability to perceive pain and other sensory stimulation or reduced coordination (ISO, 2007). Ha logenated hydrocarbons such as chloroform were among the first general anesthetics and certain form s (particularly fluorinated hydrocarbons) are still widely used for clinical purposes. There is no single mandated test method for evaluating anesthetic potency. In experimental animals, anesthetic effect s can be tested by measuring changes in coordination or posture, such as the loss of righting ability of mice or rats, or loss of balance in a rotating apparatus. More commonly, anesthetic effects are evaluated as pa rt of acute or subchronic studies where the activity level of the animals (locomotion, inquisitiveness, br eathing rates) are tracked by the investigators and compared to those in control animals. Table 2 iden tifies concentrations associated with anesthetic effects for a number of well known refrigerants.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### Table 2. Anesthetic Concentrations of Select Refrigerants Refrigerant NOEL (ppm) Source R-11 50,000 12,500* Lester and Greenberg, 1950 ASHRAE, 2007 R-12 22,700** ASHRAE, 2007 R-32 86,000 250,000* Ellis et al . 1996 ASHRAE, 2007 R-134a 81,000 Silber and Kennedy 1979 R-152a 100,000# Limperos and Zapp, 1951 R-227ea 105,000 DuPont, 2006 R-744 (CO 2 ) <75,000 Blackwell et al. , 2006 *ASHRAE values may differ because ASHRAE has access to unpublished manufacturer data ** Value adapted from a human study which indicated escape impairment potential. # The Lowest Observed Effect Levels (LOEL) All values from studies with rats unless otherwise noted ppm = parts per million



### 2.2.2.3 Cardiac Sensitization

An increased sensitivity of the heart to e ndogenous epinephrine (also called adrenaline), a phenomenon referred to as cardiac sensitization, has l ong been recognized as a risk during exposure to refrigerants and related chemicals (Brock et al ., 2003). In the early 1900s, Levy and Lewis (1911; as

cited in Brock et al ., 2003) reported that cats lightly anestheti zed with chloroform were unexpectedly sensitive to injected epinephrine. Based on this observation and further studies, the potential hazard associated with administering hydrocarbon anesthetic agents followed by epinephrine became clearly recognized. In the 1960s when CFCs were increasi ngly being used as aerosol propellants, numerous sudden deaths from their abuse to achieve a light anesth esia (a "high") led to further investigation of the phenomenon of cardiac sensitization. It should be noted that these deaths were due to extreme exposures, doses sufficient to cause central nervous system effects.

The first detailed description of a method for determining the cardiac sensitization potential of compounds was published by Reinhardt and colleagu es (1971) of DuPont. The method used a fixed epinephrine dose protocol. Briefly, a beagle dog w as exposed to various concentrations of the test compound in air and given an intravenous epinephr ine injection before and during exposure to the potential sensitizing agent. The electrocardiogram (ECG) response was continuously monitored over the course of the 17-minute protocol. If the compound at a given concentration was a cardiac sensitizer, a life-threatening arrhythmia was seen on the ECG. The dose of epinephrine used in the Reinhardt et al

. protocol was 8 μg/kg, which provides a dose rate that is about 10-times higher than the dose rate calculated to occur in humans during times of stress (Brock et al ., 2003). Using this protocol, nearly 100G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### halocarbons and hydrocarbons were tested for the pur pose of ranking the potency of the test compounds. Nearly all were capable of sensitizing the beagle hear t to an epinephrine challenge, resulting in a serious arrhythmia. Of the CFCs, R-11 and R-113 (trichlorotr ifluoroethane) were the most potent, each with a lowest-observed-adverse-effect level (LOAEL) of 5,000 ppm.

In the 1980s and early 1990s, there was a significant amount of toxicological investigation undertaken to evaluate the toxicity of HCFCs and HFCs as CFC replacements. The protocol for cardiac

sensitization studies was similar to that of Reinhardt et al . (1971), except that the dose of epinephrine used was adjusted for each experimental animal ( i.e. , the titration protocol). That is, prior to testing the refrigerant chemical, a dose of epinephrine was established for each individual dog that would be minimally arrythmiogenic. Once the dose of epinephr ine was established, that dose would be used when the dog was exposed to the test compound following the same 17-minute protocol described above. Hardy et al. (1994) reported that titration of the dose for each dog with epinephrine at doses of 2-12 μ g/kg was more sensitive for detecting cardiac sensitizati on than when using the fixed epinephrine dose protocol. Results from cardiac sensitization studies for a number of fluorocarbon compounds studied with the earlier and later methodologies are presented in Table 3.

Table 3. Results of Cardiac Sensitizat ion Studies for Different Fluorocarbons a 

### Compound LOAEL (ppm) NOAEL (ppm) Epinephrine Dose ( μ g/kg) b 

### Fixed epinephrine dose CFC-11 25,000 1,000 8 CFC-12 50,000 25,000 8 CFC-114 25,000 Not determined 8 CFC-115 150,000 Not determined 8 CFC-113 5,000 2,500 8 Titrated epinephrine dose HCFC-141b 9,000 Not determined 10, 12 HCFC-225cb 20,000 15,000 8, 12 HFC-125 100,000 75,000 12, 12 HFC-134a 75,000 50,000 4, 8 HFC-143a 300,000 250,000 4, 12 HFC-236fa 150,000 100,000 8, 12 HFC-32 Not determined 350,000 8, 12

a Results adapted from Brock et al ., 1999, 2003 b For titrated doses, the first number is the lowest dose used in the study to elicit a cardiac sensitization response, the LOAEL. The second number is the highest epine phrine dose used in the study at the NOAEL.



### In the protocols discussed above, exogenous doses of epinephrine were expected to result in blood levels that were greater than physiological levels attained in humans under stress conditions. Therefore, endogenous epinephrine studies were conduc ted to determine the exposure concentrationsG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### needed to induce sensitization without the administra tion of exogenous epinephrine. In one approach (Reinhardt et al ., 1971), dogs were exposed to 80% test co mpound while simultaneously being subjected to "fright stimuli" ( e.g. , sirens, gongs, and jet engines) with the intention of stimulating the release of endogenous epinephrine. In this study, a cardiac sen sitization response could not be elicited with any dose of R-12 in the 12 dogs being tested, even at a dose of 800,000 ppm, which is sixteen times higher than the R-12 concentration found to produce cardiac sensiti zation with injected epinephrine. In the other endogenous epinephrine approach (Mullin et al ., 1972), dogs were exposed to specific inhaled concentrations of test compounds for approximately 20 minutes while they ran on a treadmill to generate their own adrenaline. In this study, the dose of R-12 producing cardiac sensitization was 100,000 ppm, or twice that producing such an effect with injected epinephrine. These studies indicated the conservative nature of the test result from studies involving injected adrenalin.

Investigators have also examined how dose metric ( e.g. , peak dose, cumulative dose, dose over a specific time period) affects cardiac sensitization. A series of studies in dogs (summarized in Brock et al

., 2003) found that blood fluorocarbon concentrations ge nerally increase rapidly during the first 5 minutes of inhalation exposure and more slowly or not at all for the remaining minutes of exposure. At the end of exposure, there is a rapid decline in blood concentra tion for the first few minutes which then levels off substantially. Trochimowicz et al . (1974) found that tissue concentrations of fluorocarbon were directly

correlated with the blood and inhaled concentrations of fluorocarbon associated with cardiac sensitization.

There was no evidence of retention of fluorocarbon in tissues after a 10-minute acute inhalation exposure.

Beck et al . (1973) demonstrated that the peak blood concentration of the test compound is the most important factor regarding the timing of the epinephr ine challenge, and that it does not matter whether the peak concentration is reached quickly or gradually.

Concerns have been raised about the protectiv eness of results from the dog studies for particularly susceptible human populations, such as individuals w ith pre-existing heart conditions (Trochimowicz et

al ., 1976). Trochimowicz and colleagues conducted a study in which they compared the thresholds for cardiac sensitization in dogs with recent artificially induced myocardial infarctions ( i.e. , heart attacks) to those thresholds in normal dogs (Trochimowicz et al ., 1976). The authors reported that dogs with recent myocardial infarctions were not more susceptib le to cardiac sensitization by R-11 or Halon 1301 (bromotrifluoromethane) than normal dogs, and concl uded that there was "no greater potential for cardiac sensitization among dogs having recovered from myocardi al infarction as compared to normal, healthy animals" (Trochimowicz et al ., 1976). It should also be noted that the United States National Research Council (NRC) (2004) concluded that no uncertainty factors are necessary when the normal cardiacG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### sensitization protocol is used, because the doses of exogenous epinephrine achieve plasma concentrations that are 10 times greater than those achieved during physiologic stress, such as exercise or loud noise. Therefore the dog cardiac-sensitization test, when perfo rmed using the standard methodology, is believed to be sufficiently conservative to compensate for un certainties related to dog-to-human extrapolation or inter-individual sensitivity.

2.2.3 Subacute, Sub-Chronic and Chronic Toxicity (Repeated Dose Studies)

As opposed to acute toxicity, sub-chronic and ch ronic toxicity refer to adverse effects resulting from continuous or repeated exposures of intermediate (sub-chronic) or long-term (chronic) duration. Sub-chronic and chronic toxicity tests are performed to assess the cumulative toxicity of chemicals. Tests are generally conducted in rodents for reasons of cost and space. Subacute studies involve exposing animals to test materials for either 14 or 28 days (OECD 412). Subchronic studies involve exposure of the test animals to the test chemical for a period of 90 days (for inhalation studies, this usually involves exposure 6 hours per day, 5 days per week), followe d by detailed examination of tissues for signs of damage (OECD 413). Chronic studies follow a similar approach but the exposure period is one to two years (if rodents are used) (OECD 452/453). The studies are usually conducted in series, with results of the shorter term studies informing the design of the l onger term studies. Because the risk of exposure to refrigerants will be due to accidental discharges in high concentrations over an acute time frame, subchronic and chronic effects are not specifically addressed in the risk assessment. These types of effects could be significant for automotive or chem ical manufacturing workers who may be exposed to low concentrations of refrigerant over extended periods of time.

2.2.4 Genotoxicity

Genotoxicity refers to potentially harmful effect s on the hereditary material (DNA) and on the genetic processes of living things. Such effects can be assessed directly by measuring the interaction of agents with DNA or more indirectly through the assessment of DNA repair or the production of gene

mutations or chromosome alterations. A number of assays are used to screen for possible mammalian mutagens and carcinogens. These tests include the Ames assay (OECD 471), the chromosomal aberration assay (OECD 473), the micronucleus assay (OECD 474), th e sister chromatid assay, and the unscheduled DNA synthesis assay. The first two of these assays are conducted using isolated cells ( i.e. , in vitro ) whereas the latter three tests involve exposure of whole an imals. All evaluate changes in some part of the DNA replication process. In general, regulatory agenci es give greater credence to tests results obtained inG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### whole animal assays and in tests using mammalian cells ( e.g. , the chromosomal aberration and micronucleus assays) rather than tests using bacteria ( i.e. , the Ames assay).

2.2.5 Carcinogenesis

Chronic toxicity tests often include a consideration of the carcinogenic potential of chemicals so that a separate lifetime feeding study that addresses car cinogenicity does not have to be performed. These studies are usually performed in rats and mice and ex tend over the lifetime of the species (18 months to 2 years for mice; 2 to 2.5 years for rats) (OECD 451/453). Recognizing that lifetime studies are both very costly and slow to provide needed data, re gulatory agencies have recently begun considering carcinogenicity screening tests. Such tests can i nvolve exposures of genetically susceptible animals, which may evidence early signs of carcinogenicity ( e.g. , molecular or microscopic alterations) in substantially shorter timeframes.

Although the possible carcinogenicity of most refrigerant chemicals has not been studied in detail, those studies which have been conducted (primar ily on the haloalkanes) have suggested a lack of carcinogenic potency relevant for humans. For example, in two chronic studies of R-134a in rats, inhaled concentrations of up to 50,000 ppm for 6 hr/day for up to 2 years did not result in any tumors relevant to humans (NRC, 1996). In a chronic inhalation study of HCFC-123 at exposure levels up to 5,000 ppm, rats at the end of the 24-month exposure period show ed an increased incidence of microscopic, benign tumors of the liver, pancreas, and testes. Ther e was evidence that these tumors were caused by nongenotoxic mechanisms and would not be relevant to humans, but a more in-depth understanding of these findings needs to be developed (Dekant, 1996; Trochimowicz, 1993). Two-year cancer studies of chlorotetrafluoroethane (HCFC-124) and 1,1-dich loro-1-fluoroethane (HCFC-141b) conducted in rats also yielded findings indicating a lack of carcinogenic potential in humans (Malley et al. , 1998,

Millischer et al. , 1995).

2.2.6 Reproductive/Developmental Toxicity

Several types of animal tests are utilized to exam ine the potential of an agent to alter development and reproductive capacity ( e.g. OECD 414,422,423). Developmental toxi city refers to adverse effects on the developing organism occurring anytime during the life span of the organism that may have resulted from exposure to chemical or physical agents befo re conception (either parent), during prenatal development, or postnatally until the time of puberty. Tests are generally conducted in rats and/or rabbits.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### Reproductive toxicity refers to adverse effects on the male or female reproductive system that may result from exposure to chemical or physical agents (OECD 415,416). Examples of reproductive and developmental toxicity studies for some haloalkanes are presented below.

In three inhalation studies (two in rats a nd one in rabbits) conducted to examine the developmental effects of R-134a, high concentrations (10,000 ppm and greater) resulted in developmental effects, including maternal toxicity, reduction in fetal weight, and delays in skeletal ossification. No

treatment-related effects were seen at lower con centrations (NRC, 1996). NRC (1996) identified a developmental NOAEL of 2,500 ppm from these studies. In reproductive studies of R-134a in rats, there was an increase in testicular weight from exposure to 50,000 ppm for 6 hr/day, 5 days/wk for 2 years, but

no such effects at lower concentrations or for shorter durations (NRC, 1996). NRC (1996) did not consider the increase in testicular weight to be an adverse effect by itself, and thus identified a reproductive NOAEL of 50,000 ppm.

2.2.7 Ecotoxicity

Ecotoxicity (or ecological toxicity) studies measu re the effects of chemicals on fish, wildlife, plants, and other wild organisms. Due to their physiochemical properties, CFCs, HFCs, and HCFCs are expected to have a low potential for ecotoxicity and bioaccumulation (Dekant, 1996). These properties include low octanol/water coefficients and high volatility . Most are gases and have very low solubility in water at room temperature and thus are unlikely to remain in water (Dekant, 1996; Tsai, 2005).

Ecological toxicity is typically tested in a few indicator species including the algae Selenastrum capricornutum (OECD 201), the invertebrate Daphnia magna (OECD 210), and fish such as the small head minnow ( Pimephales promelas ) or carp ( Cyprinus carpio ) (OECD 211). In these studies the test organism is exposed to the agent of interest di ssolved in water for relatively short durations ( e.g. , 96- hours in the fish test) and measures of gross toxicity are evaluated. For algae, the concentration which causes 50% inhibition of growth relative to a control group is calculated. For animals, measures such as immobility or mortality are recorded. The value reco rded is generally the concentration producing a 50% effect ( e

. g ., 50% mortality).

Most CFC replacements have been only partly tested for toxic effects on organisms in the

environment. Berends et al . (1999) tested R-134a, HCFC-123, HCFC-141b, and HCFC-225ca for effects on algae, Daphnia , and fish. R-134a showed the lowest toxicity, with LC 50 

### values ranging from 450 toG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### 980 mg/L, indicating a classification of “not dangerous to the environment” according to EC regulations (EC Directive 67/548/EEC). The low toxicity of R-134a in acute aquatic toxicity tests is said to be in agreement with results from mammalian toxicity testi ng and could be related to its low bioaccumulation potential (Berends et al ., 1999). Some of the acute aquatic LC 50 

### values for HCFC-123, HCFC-141b, and HCFC-225ca were less than 100 mg/L, but all were greater than 10 mg/L, indicating a classification of “harmful” under European Union regulations ( i.e. , R52/R53) However, because these compounds are volatile and will disappear from aquatic ecosystems rapi dly, they do not constitute a long-term danger to the environment (Berends et al ., 1999).

2.2.8 Toxicity Criteria Used for Risk Assessment

In considering how to relate the toxicity data described in the proceeding sections to potential risks for humans exposed to ARs, we followed th e approach developed by the American National Standards Institute (ANSI) and American Societ y of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) in their joint standard 34-2007, Designation and Safety Classification of Refrigerants. An nearly identical standard (ISO 817) is also under review by the International Standards Organization (ISO, 2007).

The ANSI/ASHRAE standard describes the pro cess of establishing a refrigerant concentration limit (RCL) which is defined as a concentration limit "intended to reduce the risks of acute toxicity, asphyxiation, and flammability hazards in normally o ccupied, enclosed spaces." With respect to acute toxicity, the standard specifies that an Acute Toxi city Exposure Limit (ATEL) is determined from the

lowest of several values:

1. A fraction of the animal LC50.

2. The cardiac sensitization NOAEL.

3. A fraction of the concentration producing anesthetic or central nervous system effects in animals.

4. Eighty percent of the lowest concentrati on reported to cause effects in humans which would impair the ability to escape or whic h causes irreversible health effects.

For criteria 1 and 3, the specific fraction employed is dependent on the type of data available. For example, criterion 3 allows for 50% of the 10-minute EC50 in rodents for loss of righting ability in the rotating apparatus test, 50% of the lowest effect leve l for signs of anesthetic or CNS effects in any acuteG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### study, or 80% of the no effect level for signs of an esthetic or CNS effects in any acute, subchronic, or chronic study. For refrigerant blends, the ATEL is calculated by weighting the critical value for each component by its mole fraction in the blend, according to the following formula:



### . 2 2 % 1 1 % 1

etc Component Value Toxicity Component Mole Component Value Toxicity Component Mole Blend for Value Toxicity

+ + =

Once the ATEL is calculated, the RCL is then selected as the lowest concentration among the ATEL, the oxygen deprivation limit (140,000 ppm), or 25% of the LFL. The ANSI/ASHRAE RCL is meant to be a generic standard applicable to all situ ations where exposure to refrigerants may occur. The ANSI/ASHRAE use of a single RCL does not allow one to consider various aspects of product safety which are important in selecting an AR. Because the scenarios addressed in this risk assessment are fairly specific, the ANSI/ASHRAE methodology was adapted in the following ways to derive a modified RCL (mRCL):

• In exposure scenarios where an element of fright/stress is possible, the exposure concentration is compared to the cardiac sensitization NOAEL, unless some other healthbased criterion produces a lower value. Stress may be induced by sudden, lifethreatening events ( e.g. . vehicle accidents) or sudden and strong auditory or visual stimuli ( e.g. , a high pressure leak which produces an audible sound).

• In exposure scenarios which are unlikely to pr oduce stress, the exposure is considered in comparison to an "mRCL" 5 

### based on a set of criteria that do not include cardiac sensitization ( i.e. , acute toxicity or anesthetic/CNS effects). Because the cardiac sensitization endpoint required both chemical exposure and an element of significant stress to produce an adverse outcome, applying the toxicity criteria based on cardiac sensitization to non-stress situa tions would be inappropriate.

Flammability concerns were addressed by calculating a separate Flammability Hazard value (Section 2.5.2). Oxygen deprivation concerns were not rele vant to the present case since flammability and healthbased values were always more restrictive. With respect to the mRCL, note that subchronic/chronic effects are only relevant for on-going, non-episodic exposures. Because potential exposures of vehicle passengers or vehicle repair personnel are acute in natu re, subchronic or chronic toxicity health effects are not quantitatively addressed in the risk assessment. However, effects such as subchronic, chronic, reproductive and developmental t oxicity; genotoxicity; and carcinogenesis may be of concern for

5 Because RCL as defined by ANSI/ASHRAE is a comprehensive term incorporating both toxicity and flammability concerns and also does not distinguish betw een stressful and non-stressful situations, the term mRCL is used to describe separate health

based values for stressful a nd non-stressful situations.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### chemical company production workers or automotive la b technicians who may have repeated exposures. These effects are evaluated qualitatively.

The ANSI/ASHRAE standard also describes a process for classifying refrigerants into " safety

groups " based on both toxicity and flammability. Refrige rants are given an alphanumeric code (A1, A2, A3, B1, B2, or B3) where the letter indicates toxicity class and the number indicates flammability. Refrigerants where the occupational exposure limit is at or above 400 ppm are designated class A, whereas refrigerants where the occupational exposur e limit is below 400 ppm are designated class B. Refrigerants which are not flammable according to th e ASHRAE specified tests are designated class 1, whereas flammable refrigerants are designated class 2 or class 3 depending on factors such as the lower flammable limit (LFL) and heat of combustion, as determined using specified test methods and

conditions. It should also be noted that the draft ISO refrigerant standard (ISO 817) includes within the “class 2” flammability designation, an additional subc lass, 2L, which applies to refrigerants with a burning velocity of less than or equal to 0.1 mete r per second, when evaluated under ISO specified test conditions. Thus, under the proposed ISO standard A2L and B2L are also possible safety designations (ISO, 2007). The 2L flammability classification category was proposed by ISO participating member countries in recognition of the substantially lower fire damage and fire spread risk associated with low burning velocity refrigerants ( i.e ., those with burning velocities less than 0.1 meters per second) relative to Class 2 or Class 3 refrigerants with higher burning velocities.

Finally, in addition to the alphanumeric code , the ANSI/ASHRAE standard assigns the term

" toxic " to refrigerants with rodent LC50 values between 200 ppm and 2,000 ppm, and the term " very

toxic " to refrigerants with LC50 values less than or e qual to 200 ppm. This terminology does not appear to be part of the draft ISO 817 standard.



## 2.3 Evaluating Flammability of ARs

Flammability of refrigerants is a long-standing issue. Some of the earliest refrigerant gases were flammable and the development of R-12 was in part driven by a desire to avoid fire risks. The discovery that the highly unreactive and largely non-flammable CFCs and HCFCs pose ozone depletion and global warming risks has forced a reconsideration of refrigera nts that are slightly to moderately flammable. Thus, U.S. EPA conducted a risk assessment of R-152a (1,1-difluoroethane) that specifically addressed risk of fire and potential methods for mitigation (Blackwell et al ., 2006).G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### 2.3.1 Relevant Flammability Properties

To evaluate the potential flammability of an AR , one must know the flammability characteristics of the chemical, including the lower and upper flammable limits, the minimum ignition energy, the autoignition temperature, and the burning velocity . Since these parameters can depend on the test apparatus and criteria used, the actual method used to determine each value should be identified. Wellestablished testing methodologies ( e.g. , ASTM E681 for flammable limits) should be employed where possible.

Definitions of the key flammability properties are given below :

• The upper and lower flammable limits (LFL and UFL). The minimum and maximum concentrations of a substance between which it is possible to propagate a flame through a homogeneous mixture of the substance and ai r under specified test conditions (based on ASHRAE, 2007). Below the LFL, there is insufficient fuel to support combustion. Above the UFL, the material dilutes the oxygen required for combustion.

• Minimum Ignition Energy (MIE). Energy is required to initiate the reaction of the gaseous fuel with atmospheric oxygen. The MIE is the minimum amount of external energy that must be added to the system to start the self-sustaining reaction. The MIE is determined at the optimal mixture of the gas and air that supports combustion.

• Autoignition Temperature (AIT). Contact with a hot surface may potentially increase the energy of the gas molecules to a level where combustion (combination with oxygen) can occur in the absence of an ignition source. No te that the gas needs to be exposed to the hot surface for a long enough time to acquire suffi cient energy to self-ignite. In the U.S. the AIT is generally determined at atmospheric pressure using ASTM E659, “Standard Test Method for Autoignition Temperature of Liquid Chemicals.” While the ASTM standard states that the method is to be u sed for liquid and solid phase materials, it is often used for vapor-phase chemicals as well. The test method involves injecting a known concentration of flammable vapor/air mixture into a 500 cc flask maintained at constant temperature. Visual observations ar e made to determine whether ignition occurs within 10 minutes of exposure. Both concentration and temperature are varied until a temperature is reached at which no ignition is found for any concentration tested. It would be more correct to refer to this value as the minimum AIT, since autoignition will also occur for richer or leaner concentrations of the refrigerant, but at higher temperatures. AIT is not an intrinsic prope rty of a refrigerant, but rather dependent uponG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### system volume, pressure, boundary conditions for heat transfer, and time of contact (induction time) between the hot environment and gas mixture. This is clearly stated in ASTM E659.

• Fundamental Burning Velocity (Burning Velocity). The maximum speed at which a laminar flame propagates through a stationary optimal fuel/air mixture under specified conditions. This is a fundamental paramete r of the potential damage a propagating flame may cause. As a fuel/air mixture burns, hot gases are produced and the expansion of these hot gases causes an increase in local air pr essure. The rate of this pressure increase can be determined from the burning velocity , the volume change of combustion and the area of the flame front. The combustion rate ( i.e ., the burning velocity multiplied by the area of the flame front) combined with the rate the fuel material is vented into the system determines the maximum pressure obtained. The maximum pressure and the rate of pressure change are related to the resulting structural damage.

These properties are generally tested in a laboratory setting using well-established methodologies ( e.g. , ASTM E681 for determining the upper and lower flamma ble limits). The results of these studies provide a baseline indication of whether a material has the pot ential to initiate and/or sustain a fire. These tests are highly conservative, however, and do not accurately simulate real world conditions. Field testing, where the gas is introduced in a lik ely release scenario and brought into contact with an ignition source, can provide a better idea of the real world flammability potential. Field testing carried out as part of this

evaluation is described in Section 2.4.2.2.



## 2.4 Exposure Assessment

Determining potential exposure is a critical el ement in any risk assessmen t. Even the most inherently toxic chemical will pose no risk if there is no exposure. Similarly, even the most flammable chemical will not pose a risk if the concentration is not within the flammable range. In order to evaluate the risks of potential AR exposures, we first develope d a set of potential exposure scenarios, based largely on U.S. EPA's prior risk assessment of R-152a and CO 2 

### ( e.g ., Blackwell, 2006). SAE CRP1234 then conducted air modeling and field testing to determine th e air concentrations of the AR in each scenario.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### 2.4.1 Passenger Compartment Scenario

A primary concern for the automotive industry is the potential risks for vehicle passengers in the case of a system failure or accidental release of refrigerant from the vehicle AC system. Under normal operating conditions, the systems are self-contained and no release of refrigerant is expected to occur. However, leaks in system piping may occur over time ( e.g. , as a result of corrosion) and could cause a release of refrigerant into the passenger compartment. In addition, in a vehicle collision the AC system may be damaged in such a way as to cause release of a large portion of the refrigerant charge into the vehicle cabin. Both types of leaks we re considered in this risk assessment.

Information solicited from CRP1234 team members indicated that leaks generally fall into four categories: small, medium, large, and very large leaks. The first three categories would involve corrosion-type leaks of the system piping whereas the ve ry large leak would be associated with rupture of the evaporator tube from the condenser, as could occur in a severe vehicle collision. The size of the leak is critical to the exposure assessment because the diameter of the leak hole not only affects the amount of material that can be discharged but also the pressure and rate of the leak. Based on consultation with SAE CRP1234 members, three leak sizes considered were quantitatively evaluated in the risk assessment: 0.01, 0.1, and 0.5 mm. The very large leak (associated with rupture of the evaporator tube near the condenser)

was not evaluated via modeling but was considered in the FTA assuming the resulting passenger cabin concentrations would be greater than those associated with the large leak.

Assuming a release does occur, passengers may be a ffected if they inhale the refrigerant above a health-based limit ( i.e ., in this case the mRCL). Passengers ma y also be adversely affected if the refrigerant is flammable (per definitions associat ed with the mobile air-conditioning application, i.e

. ASTM E681, E582, etc .), if it is present in a flammable concentration, and if there are ignition sources

within the flammable concentration zone. A revi ew by CRP1234 members considered possible ignition sources which could be expected to be present in the passenger compartment and which could possibly have sufficient energy to ignite a material such as HFO-1234yf. A table summarizing the review of potential automotive ignition sources is included as Att achment A. The review identified three possible worst-case ignition sources: a butane lighter or match used to light a cigarette 6 

### , a spark generated by a

6 Studies by Arthur D. Little (1982) indicated that filament ciga rette lighters such as those pres ent in automotive vehicles wil l not ignite a mixture of methane and air. Since the methane-air mixture would be more flammabl e than HFO-1234yf, this potential ignition source was not considered in the risk assessment.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### short of an internal vehicle battery, and a mechani cal short from a PTC heater present within the vehicle air ducts. Each of these potential ignition sources was evaluated in the risk assessment.

In its evaluation of R-152a and CO 2 

### , the U.S. EPA considered the potential of a large leak to startle the passenger to the extent that they loose cont rol of the vehicle and have an accident. U.S. EPA's analysis showed that the probability of this outcome ( i.e. , passenger or bystander injury from accident) was approximately 40-times less than the probability of a corresponding adverse health effect of exposure of vehicle passengers. In addition, risks of chemical exposure or ignition and risks of being injured by an out-of-control vehicle represent different types of outcomes and combining these into an overall risk estimate is questionable. We therefore did not incl ude the startled driver accident-related injury scenario

in the current risk assessment.

2.4.2 Potential AR Concentrations in Vehicle Passenger Compartment

2.4.2.1 CFD Modeling

Air modeling for the passenger exposure consisted of a two step process: estimation of the mass of refrigerant released through the leak over time follo wed by dispersion modeling to estimate refrigerant concentrations in the passenger compartment. The pr edicted emission leak rates were determined based on empirical leak data collected by Honeywell (Honeyw ell, 2008). Honeywell measured the leak rate of HFO-1234yf using a cylinder discharge system (simulating leak through evaporator) with a specific hole

diameter of 0.5 mm.

The predicted emission rates were used as input for CFD modeling in order to estimate chemical concentrations in the passenger compartment. CFD m odeling is a powerful tool that can predict localized refrigerant concentrations in the passenger compar tment. In the CFD model the passenger cabin was represented by a set of several hundred thousand cells , each cell representing a small discrete air space. The refrigerant concentration in each cell is then simulated over time, taking into account air flow patterns within the vehicle.

CFD modeling was conducted by DuPont, using a vi rtual vehicle with the same dimensions as the vehicle model used by the U.S. EPA in its evaluation of R-152a and CO 2 

### (R-744). Specific details pertaining to the passenger cabin modeling are described in the DuPont document CFD Modeling of a Large Car (DuPont, 2008). Honeywell also conducted modeling using a smaller vehicle (2.5 m 3 

### internalG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### volume vs . 3.1 m 3 

### ) in order to understand the potential impacts of a refrigerant release on another segment of the vehicle fleet (Honeywell, 2008). Because same vehicle specifications were used as the model for earlier CFD efforts ( i.e ., the U.S. EPA assessment of CO2 and R-152a as well as the work of CRP150), the Honeywell results were not used in the risk assessment. The Honeywell study nonetheless reached conclusions similar to the DuPont study and provide c onfidence in the use of the DuPont data in the risk

assessment.

To evaluate modeled concentrations of the AR in the passenger compartment we calculated three values. To evaluate the potential risks of cardi ac sensitization, we calculated the maximum 5-minute Time Weighted Average (TWA) concentration. This represents the highest 5-minute exposure the passenger might experience. Note that the animals in the cardiac sensitization studies are exposed to a steady concentration whereas the passenger would be exposed to a variable concentration. While it is true that the actual peak exposure ( i.e. , the highest level reached over any time frame) may be higher than the 5-minute TWA, studies of cardiac sensitization suggest that a 5-minute exposure is most comparable with the data obtained with the experimental animals.

To evaluate other health effects ( e.g. , anesthetic effects, acute lethality), we calculated the

maximum 30-minute TWA concentration. This is because the ASHRAE criteria specify human exposures of 30 minutes which involve escape-impairing e ffects. As regards animal data, the ASHRAE RCL criteria specify lethality in 4-hour studies or an esthetic effects from acute exposures (again, likely to be at least 4 hours in duration). Thus a 30-minute TWA is conservative.

To evaluate potential ignition risks, we looked at the peak AR concentration in the passenger compartment ( i.e ., the maximum concentration occurring at any second). This is also conservative because it assumes that the peak o ccurs in the same time frame as the ignition source and that the concentration of AR stays above the LFL for a suffici ent time for the passenger to be injured or other materials in the passenger cabin to be ignited.

2.4.2.2 Field Testing

To supplement and confirm the CFD results, pot ential AR concentrations and ignition risks associated with a leak of refrigerant into the passenge r and engine compartments were field tested using an actual vehicle by Exponent, Inc. (Exponent). Obviously, the amount of testing ( i.e. , the combinationG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### of operating and environmental conditi ons that can be considered) is constrained by cost and vehicle availability. The testing done was intended to reflect a worst-case situation.

Briefly, a commercial vehicle was obtained a nd equipped with six mannequins encased in Nomex

suits. The vehicle was located inside a tem porary shed to minimize the effect of wind. During the test, the refrigerant was released into the air conditioni ng system air distribution system. The release simulated a 0.5 mm hole in the evaporator (the “lar ge” leak considered in the CFD modeling) with refrigerant leaking into the passenger compartment. During the refrigerant release (full system charge was released) and a significant time after the full refri gerant release, refrigerant concentrations were

determined at different locations in the vehicle in terior (driver and front seat passenger breathing zones, driver and passenger lap areas, driver and passenger foot areas, AC vents, and inside the AC ductwork). Concentrations were monitored for approximate ly 1,600 seconds as the refrigerant concentration dissipated. The vehicle fan was operated at low sp eed, using an outside source of electric power. A separate test was also conducted in an attempt to ign ite the refrigerant using a butane lighter. The lighter was placed near the location having the highest refrige rant concentration in the preceding concentration

studies. Pressure transducers and video cameras were used to monitor potential refrigerant combustion. Other variables ( e.g. , temperature inside vehicle, wind speed, humidity) were also measured. More detail regarding the field testing is provided in the Exponent report HFO-1234yf Refrigerant Concentrations and Ignition Tests in Full-Scale Vehicle Passenger Cabin and Engine Compartment (Exponent, 2008).

2.4.3 Potential AR Concentrations After a Leak in the Engine Compartment

CFD modeling was not conducted to determine potential AR concentrations in the engine compartment. Given the complex and variable geomet ry of the engine compartment, developing such a

model would have been both time cons uming and of questionable validity. Instead, field testing was used to estimate AR concentrations and ignition risk s from a refrigerant release within the engine compartment. The leak involved a 12.4 g/s refrigera nt leak rate, mimicking a leak at the compressor outlet hose. This leak rate is approximately ten times the large leak rate used in the CFD modeling. The refrigerant was released into the engine space through a 1⁄4” nylon tube. After the complete release of the charge (approximately 691 grams), measurements of th e refrigerant concentration were recorded at locations in the engine compartment near the exha ust manifold, the anticipated location of highest temperature. As with the passenger compartment study , the potential to ignite the refrigerant was also evaluated by introducing a heating element into th e engine compartment at the location of highest

concentration. Pressure transducers were used to ch aracterize the potential combustion. Other variablesG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### ( e.g ., the temperature inside the vehicle, wind speed, hum idity) were also measured. Greater detail on the field testing can be found in the Exponent report HFO-1234yf Refrigerant Concentrations and Ignition Tests in Full-Scale Vehicle Passenger Cabin and Engine Compartment (Exponent, 2008).

2.4.4 Potential AR Concentrations Associat ed with Leaks in Vehicle Repair Areas

There are an estimated 20 to 25 million vehicle AC system service events annually performed by repair workers in the U.S. (Carley, 2004). Of these, approximately 75% involve work with the refrigerant loop. Persons engaged in AC system repair could be exposed to refrigerants in the event of a release from the vehicle or from service equipment. In their "R isk Analysis for Alternative Refrigerant in Motor Vehicle Air Conditioning," U.S. EPA addressed repair worker risks qualitatively, but not quantitatively (Blackwell et al ., 2006). We have conducted modeling an alyses in order to address these release scenarios quantitatively. We have specifically addressed two sets of scenarios – professional service technicians and DIY non-professionals.

For all repair scenarios air modeling was conduc ted using a simple perfect mixing model (also called a box model). The box model is the simplest model type for estimating concentrations of a released or leaking chemical in an air space. It assumes the air space is in the shape of a box and that the air pollutants inside the box are homogeneously distribut ed. Air concentrations are calculated iteratively assuming a constant emission rate over the time of the release ( i.e. , the total amount of refrigerant involved in the release is divided by the time of th e release). The following fo rmula was used in the

calculations:



# ( ) t AER C V t ER C C t 

# Δ

− ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ Δ + = * * *

Where

C t = the concentration at time point of interest (g/m 3 

### ) C = the air concentration of the chem ical at the proceeding time step (g/m 3 

### ) ER = the emission or release rate of the chemical (g/minutes) V = the volume of the room or airspace of interest (m 3 

### ) AER = the air exchange rate for the room or space of interest (minutes -1 

### ) Δ t = the time step interval (minutes)

For situations involving an instantaneous release of material ( i.e. , the professional repair scenario involving a system rupture), the air concentration is initially set by dividing the entire charge amount byG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### the available air volume and then calculating the changing air concentration over time based on exponential decay.

t AER

t 

# Ce C Δ

− 

# = *



### Although these models are very simple and thus limited in their ability to accurately predict complex air dispersion patterns, the approach is reasonable for sm all spaces such as those likel y to be encountered in vehicle repair. Furthermore, unlike the passenger comp artment of an automobile, where an individual is confined to one position, individuals conducting repair are likely to move about within the "box" and thus experience exposures that are closer to an average chemical concentration.

2.4.4.1 Professional Service Technician Scenario

Using professional service equipment ( e.g. , Snap-on Dual II, Kool Kare, and ECO-12), the refrigerant in the AC system is first removed and stored in the service unit reservoir. After any necessary repair, the system is then recharged to ensure that a full refrigerant charge is present. Data from various equipment manufactures indicate that it takes approximately 15 minutes to remove the refrigerant from the system and 10 minutes or less to recharge the system with fresh refrigerant.

Two potential AR release scenarios were evaluate d for the professional repair situation: an instantaneous AC system rupture duri ng repair which vents the entire vehicle charge to repair area, and an equipment leak during refrigerant removal and rechar ging. In the first scenario, one might envision a case where some repair activity places stress on a damaged AC system which causes the system to rupture and vent the entire refrigerant charge (691 grams, consis tent with the CFD modeling) to the repair room atmosphere. To address this as worst case, we assume d that the rupture caused an instantaneous release

rather than a slow release over several minutes. In the second scenario considered, leaks in the service equipment hoses could allow for a leak of refrigerant of various magnitudes, depending on the size of the hole in the hoses. This scenario requires that the servi ce technician fails to monitor the equipment or note that the equipment is malfunctioning. This would be possible if the service technician were to hook up the equipment and then leave to perform other t asks while the system was being evacuated and/or recharged. If system monitoring were neglected for a sufficient duration, the entire draining and recharging cycle could be involved in a release. For this scenario, we assumed that 15% of the transferred refrigerant would be released, theorizing that a hi gher release rate would produce a sound that would be noticed by service personnel.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### The professional service technician exposure scen ario is assumed to occur in a small service station with only two service bays, where the doors and windows are closed. This results in a relatively small air space with limited ventilation. A review of property sales records suggested that a typical

volume for the service area of a small station is a pproximately 1,000 square feet (approximately 93 m 2 

### ). Assuming an interior area height of 9.5 feet (approximately 2.9 m), the total work area volume would be

270 m 3 

### . If the estimated volumes of two vehicles (16 m 3 

### ) and miscellaneous equipment (8 m 3 

### ) are deducted, this leaves an open air volume of approximately 230 m 3 

### . We assumed an air exchange rate of 1 room volume per hour (0.017/minute), which is a lo w-end estimate for a commercial facility (U.S. EPA, 2002). It should be noted that many professional re pair shops have good ven tilation by design and are often open to outside air during much of the year. Finally, we assumed that only one vehicle is having the AC system serviced at a time and that the time betw een different vehicles being serviced is such that accumulation of refrigerant does not occur.

Two other theoretically possible professional repa ir scenarios were not evaluated in the risk assessment because they were judged to be implausibl e. One of these would involve a release which could occur if an improper seal were made between the vehicle and the service equipment, allowing the refrigerant charge to escape. Most, if not a ll, service units are equipped with auto shut-off adapters/couplers which prevent release of refrigerant during connection/disconnection and also ensure a locked seal to the vehicle AC system. Thus we judged this scenario to be implausible. In addition, this scenario is unlikely to result in greater exposure than the system rupture scenario described above. The other implausible scenario involved release of resi dual refrigerant from the 30-pound storage canisters once they were changed out of the charging equipment. Results from the Disposable Container Heel Testing Study Report [Heel Study] (Perrin Quarles, 2007) showed that only minimal residual refrigerant remained in the 30 pound canisters after charging. Fu rther, due to the design of recharge systems, a release from the canister itself is unlikely. Therefore, this type of release was not included in the risk

assessment.

It should be noted that visits to facilities wher e AC systems were being evaluated and discussions with industry professionals indicated that refrigerant exposures to professional service technicians are likely to be very rare. Most service shops are we ll ventilated and, as noted above, AC service equipment is designed to provide a tight seal between the ser vice unit and the vehicle AC system. The scenarios

evaluated should therefore be considered worst-case and unlikely to occur in the vast majority of service

locations.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### 2.4.4.2 DIY Scenarios

Some individuals may not use professional service technicians to service their MAC systems and instead may attempt to perform repairs themselves. Because MAC systems are now better built, need less refrigerant, and are more complicated, there are fewe r DIYers now than in the past. However, it is estimated that 3% of MAC service work is done by DIYers (MACS, 2003). These individuals could be at an increased risk of injury because they may not know the appropriate precautions to take and would not have access to specialized tools and safety equipment.

In the DIY scenarios, the amount of refrigerant will be more limited than in the professional repair technician scenario. DIYers are not assumed to have access to professional service equipment (units which cost several thousand dollars) and instead are assumed to use commercially available recharge cans. These cans involve much smaller volumes ( e.g ., one may purchase 350 gram cans of R134a, which constitutes slightly more than one-half the normal R-134a system charge).

The potential for release of refrigerant from sma ll recharge cans was evaluated by Perrin Quarles Associates for U.S. EPA in 2007 (Perrin Quarles A ssociates, 2007). In their document, "Disposable Container Heel Testing Study Report," Perrin Quarles Associates described the varying use conditions under which recharge cans are employed and the imp act of these recharge conditions on the AC system charging time and the residual volume left in the can. They reported that the most efficient charging method involved turning the can upside down. After five minutes of system charging in this position,

98.6% of the can's contents were tran sferred, leaving only 1.4% residual ( i.e ., heel). In contrast, when AC system charging was performed holding the cans in an upright position, only 25.3% of the can contents was transferred within 5 minutes, and only 42.7% was transferred within 15 minutes. They reported that it would take approximately 90 minutes to empty the remainder of the can contents into the room atmosphere. In an intermediate condition, in which the can is rotated while charging, 79.6 percent of the

can contents were transferred in the first 5 minutes and 98.4% were transferred in the first 15 minutes (see Perrin Quarles Associates, 2007, Table 4). Despite th e fact that charging in the upside down position was the most efficient in terms of refrigerant transfer, a survey conducted at a training institute (Universal Technical Institute, Avondale Arizona) revealed that only approximately 25% of respondents indicated using the upside down method whereas 75% indicated they held the can upright (Perrin Quarles Associates, 2007). This is consistent with directions printed on the can which instruct users to hold the can upright. All survey respondents also indicated they would charge a system with a single can forG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### either less than 5 minutes (41%) or 5 to 10 minutes (59% ). None reported that they would charge for a longer time (Perrin Quarles Associates, 2007). Perrin Qu arles also reported that charge kits, used to connect the refrigerant cans to the vehicle AC system , were prone to leaks, at either the service port adaptor or the can tap. The magnitude of the leaks from these locations was not measured.

In the upright can position scenario, the DIYer u ses 2 cans of refrigerant and charges the vehicle AC system with cans in the upright position. This resu lts in a limited amount of transfer of refrigerant to vehicle AC and 75% remaining in cans (see Perrin Quarles Associates, 2007, Table 4). The Perrin Quarles study was conducted with 134a and we assumed r esults would be similar for a future AR (lacking specific information on future retail plans, we also assumed the mass of AR in each can would be the same the current situation with R-134a, i.e ., 350 grams). The cans are set out and slowly release the remaining refrigerant to the garage air over 90 minutes ( i.e. , the time it reportedly took for cans in this position to empty). Note that charging the system with the can in other orientations ( e.g. , upside down, sideways, with shaking) causes more refrigerant to be transferred to the vehicle AC system and thus less

to be released to room air.

In the upside down position scenario, the DIYer uses 2 cans of refrigerant and charges the vehicle AC system with cans in the upside down position. This results in the most rapid and complete transfer of refrigerant to vehicle. We assumed that due to a leak in the charge kit hook up or an improper connection, 15% of the refrigerant escapes and enters r oom air. The leakage is assumed to occur over the

10 minutes it takes to transfer most of the contents of the two cans to the vehicle (see Heel Study, Table 4). Note that in reality a small amount of time (0 .5 to 2 minutes) would be required to hook up the second can. This additional amount of time is not included in the modeling since the time will vary among individuals and its exclusion is more conservative ( i.e ., a shorter time for material release results in greater air concentrations).

For the DIY scenario involving a heel release, we assumed a small garage volume of 36 m 3 

### (4m x 3m x 3m). We deducted the estimated volumes of a typical vehicle (8 m 3 

### ) and miscellaneous garage equipment (5 m 3 

### ). An air exchange rate of 0.1 room air volumes/hour was used, which is likely to be excessively low for a home garage, which would tend to be poorly insulated. At least one recent study has reported that air exchange rates in garages averaged 0.77 per hour (Batterman et al. , 2007). These assumptions are meant to represent a worst-case scen ario when the garage door is closed ( e.g. , in winter). With the garage door open, it is likely that there w ould be sufficient ventilation to substantially reduce

risk.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### For the DIY scenario involving leak from the ch arge kit assembly while charging a vehicle, we assumed a very small volume of 0.5 m 3 

### , which characterizes the amount of air volume surrounding the engine with the hood raised. In charging the vehicle, we assumed the DIYer would be stationary at the side of the car, leaning over the engine area until char ging is complete. This small air space will clearly be overly conservative if air currents ( e.g. , those generated by the leak itself) are sufficient to rapidly disperse the released refrigerant beyond the immediate vicinity of the hood area.



## 2.5 Risk Characterization

Risk characterization represents the step in the analysis where data on toxicity, flammability and anticipated air concentrations are brought together to quantify the potential risks of the AR. The results

of the risk characterization contribute to the FTA and allow a final estimate of the number of adverse

events.

2.5.1 Health Risks for Passeng ers and Vehicle Repair Workers

The first step in the characterization of potentia l health risks is to compare the predicted air concentrations for the passenger compartment and repa ir areas to the mRCL. This is done using a Hazard Index approach wherein the Hazard Index is calculated as:



### ) ( ) ( ) ( ppm value mRCL ppm ion Concentrat Exposure HI Index Hazard =

For situations where the HI is less than 1.0, we c onclude that the potential exposure is not of concern from the standpoint of potential health effects. In addition, the magnitude of the HI ( e.g. , 0.1, 0.001, 0.0001) gives a sense of the margin of safety betw een the exposure and the concentration at which adverse health effects might be expected. This ma y be useful in evaluating ARs where there is some disagreement regarding the adequacy of the data or the need to apply additional safety factors to data obtained in experimental animals. Note that for ch emicals where the HI exceeds 1.0 (that is, the exposure concentration is higher than the mRCL) there is no guarantee that adverse effect will occur because the assessment employs conservative assumptions. A HI great er than 1.0 only indicates that the exposure in question should be of concern and s hould be looked at more carefully.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### 2.5.2 Ignition Risks for Passengers and Vehicle Repair Workers

The evaluation of potential ignition risks involves a two step process. First, one determines whether the AR concentration in the location of interest ( i.e. , passenger compartment, engine compartment, repair area) exceeds the LFL 7 

### . A formula analogous to that used to calculate the hazard index may be used:



### ) ( ) (

ppm LFL ppm ion Concentrat Exposure Hazard ty Flammabili =

The resulting value should indicate some reasonable margin below the LFL ( e.g ., 90% of the LFL or 0.9) to provide an adequate margin of safety and account for uncertainties in measurement or model predictions. Note that this calculation is a screen ing step, intended to address the question: “is the estimated concentration in the passenger compartment sufficiently below the LFL”. If the answer is yes ( e.g. , Flammability hazard <0.9) then the fault tree branch for the scenario in question is “zeroed out”. If the answer is no ( e.g., Flammability hazard ≥ 0.9) then the fault tree analysis continues and we consider how frequently an ignition source might be in the fla mmable area. Once it is determined whether or not a potentially flammable concentration was present in the passenger compartment, it is then necessary to consider whether an ignition source is present in th e same point in time and space where the refrigerant exists in the flammable range. This latter step was considered in the FTA (Section 2.6).

2.5.3 Ecological Risks

As stated above, ecological risks associated with refrigerants are not anticipated to be substantial due to the low water solubility of these chemicals and their tendency not to accumulate in biological tissues. Nevertheless an evaluation of ecological risks is required in order to fully understand the potential environmental impacts of each AR. This evaluation is conducted qualitatively, by comparing the ecotoxicity test results for the AR with compar able results for other industrial chemicals, including common solvents and materials used in the automotive industry ( e.g. , gasoline components, brake fluid components, anti-freeze). The data from ecological toxi city studies are also considered in terms of the European ecological toxicity classifications and risk phrases (as set forth in EC directive 67/548/EEC).

7 Technically, the air concentration is compared to both the LFL and UFL to determine if it lies within the flammable range. In this assessment, predicted concentr ations were all well below the UFL.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### 2.5.4 Risks for Other Exposure Scenarios

Three other potential scenarios of concern to the automotive industry involve vehicle assembly workers, workers at scrap yards who may be involve d in disassembling automotive vehicles, and risks for the general public from AC system leaks which may o ccur while a leaking vehicle is parked in a public parking garage.

Regarding vehicle assembly workers, data fro m one OEM (General Motors) indicate that refrigerant concentrations (in this case R-134a) in assembl y plants is generally in the single digit parts per million (ppm) range (M. Anticoli, 2007). These data ar e based on both personal and area sampling. It is reasonable to assume that exposures to any future AR would be of the same order of magnitude ( i.e. , 0 to 10 ppm). This level of exposure is well below o ccupational exposure limits fo r known refrigerants which are established as safe levels of chronic exposure ( i.e. , 8 hours per day, 5 days per week for multiple years). It is also several orders of magnitude below the LFL of any likely refrigerant (LFLs for refrigerants are measured in percentages in air, 1% is equal to 10,000 ppm). Based on this large margin of safety, we concluded that risks for automotive assem bly plant workers did not need to be addressed in

the risk assessment.

Regarding exposures of scrap yard worker s who may disassemble automotive AC systems, current U.S. EPA regulations require that these worker s use the same equipment used by repair workers to drain and reclaim refrigerant prior to crushing or scrapping the vehicle. The risk assessment conducted for repair workers should therefore address the risks of these workers as well. It should be noted that scrap yard operations would be expected to be even less enclosed than vehicle repair facilities and the potential for build of released AR material to levels of concern is therefore unlikely. As a result, risks for scrap yard workers also were not quan titatively addressed in the risk assessment.

Finally, with respect to the parking garage scenario , the leak situations that could be considered ( e.g. , slow leak over time or instantaneous rupture) ar e identical to those that are being evaluated for repair workers (Section 2.4.4). However, while the repair worker scenarios involve relatively small air spaces and small air exchange rates, a parking garage would have a much greater air volume and much higher rates of air exchange (either due to larg e windows or active ventilation). The potential risks associated with release of ARs from a leak in a pa rking garage will therefore be lower than those associated with vehicle repair and we did not deem it necessary to quantitatively address the former

situation.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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## 2.6 Fault Tree Analysis for Evaluating Potential Risks

In order to quantify the potential adverse effects associated with a refrigerant release, we used Fault Tree Analysis (FTA). FTA is a methodol ogy that graphically presents the sequences and combinations of failures that lead to a particular outcome. It utilizes a "top-down" approach, starting with the undesired effect as the top event of a tree of logic. Each situation that could cause that effect is added to the tree as a series of logic expressions. This technique analyzes the potential combinations or sequences of events by which an undesired event may occur. FTA can consider such causal effects as human error, equipment failure, and operating and maintenance procedures, though it cannot cover those causes of system failure that cannot be envisioned by risk analysts (Blackwell et al ., 2006).

FTA provides insight on failure sequences and serves as a guide for identifying system components, use patterns, or failure modes that are most likely to contribute to an undesirable outcome. Though fault trees can be labeled with quantitative failure probabilities, not all fault trees are quantified. When quantified, absolute accuracy is often secondary to the identification of failure sequences and the determination of the effectiveness of various mitigati on measures, particularly in daily safety management activities (Blackwell et al ., 2006).

FTAs consist of various event "boxes", which refl ect the probability or frequency of key events leading up to a system failure. The event boxes ar e linked by connectors ("gates") which describe how the contributing events may combine to produce the failu re. Events may be combined in different ways:

in cases where a series of events must all occur in order to produce an outcome ( e.g. , ignition source and sufficient oxygen to support combustion), the probab ilities or frequencies of the individual contributing events are multiplied via an "AND" gate; in cases where only one of a series of events is needed to produce an outcome ( e.g. , a spark, a lighted cigarette, a hot surface all possibly leading to ignition), the probabilities are added via an "OR" gate. 8 

### More complex combinations are possible ( e.g. , conditional situations in which a series of contributing events must occur in a specific order in order to produce a failure) but these are not required by the present an alysis. An example fault tree illustrating these principals is shown in Figure 1.

8 In the special case when the inputs to an OR gate ar e probabilities of vents that could occur simultaneously ( e.g. , driver fatigued/vehicle operated at night) and which can each by themse lves cause the failure, the math is A+B-A*B. When the probabilities are mutually exclusive (vehicle st ationary/vehicle moving) the math is A+B.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### To construct the fault trees and conduct the FTA analysis, we used the software program FaultrEASETM (ICF Consulting Services, 2003). This soft ware package is the same as that used by U.S. EPA in the prior evaluation of R-152a and CO2 (Blackwell et al. , 2006).

2.6.1 Fault Tree Assumptions for Passenger Compartment Scenario

For both the health and flammability risk evaluations, the fault trees for the passenger compartment scenarios include 3 branches, each branch reflecting a different leak size ( i.e. , small, medium and large leaks). In addition, a fourth bran ch is included to address risks related to a vehicle collision which damages the AC system to an extent that a refrigerant release occurs.

The fault tree branches corresponding to the differe nt leak sizes are identical in terms of the events, gates, and multipliers involved; the primary difference is in the assigned probability of each type of release (small leaks being the most common, large leaks being the least common). The other critical

difference between the different fault tree branch es is the determination whether the modeled air concentration exceeds the relevant criterion ( i.e. , mRCL or LFL). Note that in this FTA, the value of an exceedance event is either 0 or 1, meaning that the air concentration either exceeds the limit (1.0) or it does not (0.0). The value for this input is B oolean in nature because the air modeling or field measurement result is based on a single set of conditions ( e.g. , fan speed, air infiltration rate). In order to generate a probability of an exceedance ( i.e. , a value between 0 and 1.0), di fferent conditions would need to be considered in a large number of simulations or field measurements to yield an overall distribution of results. This level of effort is outside the scope of the current project. Note that the consequence of the "0 or 1" value for this input is that in cases where the air concentration does not exceed the relevant limit,

the value of "0" causes the risks of that fault tree branch to become zero.

2.6.1.1 Fault Tree Assumptions Related to He alth Risks for Vehicle Passengers

Input values for the FTAs addressing toxicity concerns are given in Tables 4 and 5 below. These input values were selected based on the values identified by Jetter et al . (2001), Blackwell et al . (2006) as well as additions from the CRP150 analysis. Where possible, data from the Jetter et al . and Blackwell et al

. analysis were updated with newer information. Th e most significant changes to values from these earlier assessments involve the frequency of various sizes of leak as well as changes to the series of events required for the collision scenario. Regarding l eak sizes, the CRP1234 members decided to model different sizes of evaporator corrosion leaks (0.01, 0.1, 0.5 mm) in lieu of U.S. EPA's approach of onlyG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 34 Gradient CORPORATION 

### considering the rupture of the evaporator tube with a resulting leak orifice diameter of 1.8 mm. The CRP1234 members felt that this type of leak was highly unlikely and the risk assessment would be better directed at evaluating risks of leaks that are more realistic. As regards the collision scenario, the earlier CRP150 analysis required that the collision damage no ot her AC system components such that refrigerant would be vented away from the passenger compartmen t. This assumption was retained in the present analysis. This more realistic scenario r esults in a lower probability of exposure.

Table 4. Inputs for Passenger Scenario Fault Trees Addressing Health Effects – Normal Operation

Value Input Parameter USA Europe Basis

Passenger vehicles in fleet 230, 000,000 241,200,000 U.S. National Tran sportation Statistics, 2002. For the U.S. we assume all vehicles have AC. In Europe, it anticipates that about 90% of the fleet will have AC. These values reflect the 2027-2032 timeframe when the new ARs are fully in use. Number of hours per year car is in

use 340 340 Blackwell et al ., 2006

Number of occupants in vehicl e 1.59 1.59 Average value, Jetter et al ., 2001 Frequency of sudden leak from AC system. 4E-4/yr 4E-4/yr Conservative VDA field data indicates 4E-4 is the probability of a leaking evaporator. The field data average is approximately 100ppm. A factor of 4 is applied to account for lifetime influence. Factor accounting for impact of inadequate repair on leak frequency 1.5 1.5 Expert judgment.

Probability of leak of specific size: - sudden large leak - sudden medium leak - sudden small leak 0.01 0.05 0.94 0.01 0.05 0.94 Based on OEM expe rt opinion and understanding of the corrosion process. Also based on Jetter et al., 2001 which indicated that leaks of a significant size (1-3 grams per minute) are exceptionally rare. Probability leak not detected by occupants: - sudden large leak - sudden medium leak - sudden small leak 0.4 0.6 0.8 0.4 0.6 0.8 Based on OEM expert opinion. Jetter et al

. (2001) indicated that l eaks bigger than 0.05g/s are clearly noticeable by passengers.

Probability system is in recirculation mode when AC is in use 0.32 0.16 OEM updating of Jetter et al. 2001 value (0.2) based on expert opinion. Probability fresh air flap is open when AC in use 0.68 0.84 OEM updating of Jetter et al. 2001 value (0.8) based on expert opinion. Probability windows are closed when AC is in use. 0.95 0.95 OEM estimate base d on field observation.

Probability passenger air compartment concentration exceeds health-based limit. 0 or 1 0 or 1 Based on resu lts of air modeling/field measurementsG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 35 Gradient CORPORATION Table 5. Inputs for Passenger Scenario Fault Trees Addressing Health Effects – Collision Scenario

Value Input Parameter USA Europe Basis

Number of occupants in vehicle 1.59 1.59 Average value, Jetter et al ., 2001

Frequency of serious collision (every crash involving an injury of whatever severity) 5.60E-3/yr 5.60E-3/yr Five times th e national transportation statistics fatal crash rate multiplied by 12,000 miles drivenper year. Consistent with 2.5% of all crashes (3E6/mile) involving vehicle towing (9E-4/yr). Probability collision deforms A pillar > 35cm in serious collision. 0.0187 0.0187 BMW Accident Research data (Severe crashes involving BMW vehicles in Bavaria 1976-2007)

Probability evaporator piping fails in a collision. 0.05 0.05 Expert judgment.

Probability occupant survives a collision severe enough to deform A pillar > 35 cm 0.9 0.9 Jetter et al ., 2001.

Probability that only evaporator piping fails while side crash. 0.1 0.1 Estimate from DOE. In case of side crash> 35cm there’s always danger to destroy piping. Risk is higher if no other parts in engine compartment are destroyed. OEM estimation. Probability that collision does not break any windows 0.0001 0.0001 BMW Accident Research data (Severe crashes involving BMW vehicles in Bavaria 1976-2007). Data suggest true likelihood is near zero. Probability passenger air compartment concentration exceeds health-based limit. 0 or 1 0 or 1 Based on results of air modeling.



### 2.6.1.2 Fault Tree Assumptions Related to AR Ignition Risks for Vehicle Passengers

A key step in evaluating potential ignition or fl ammability hazards is the determination whether potential ignition sources are present. If no ignition s ource is present which can produce sufficient energy (either via open flames, hot surfaces or electrical sparks ) then there is no ignition hazard. Furthermore, it is necessary that the ignition source be present in the sam e location as that where the refrigerant is within the flammable range. In order to evaluate the potential ignition sources for the exposure scenarios of interest, SAE CRP1234 relied on the expert opinion of t eam members. The results of the deliberations are provided in Attachment A. The members of CRP1234 concluded that the most credible ignition sources capable of igniting an automotive refrigerant we re butane lighters or matches that might be used to light cigarettes or cigars, sparks generated by the short of a vehicle battery located on the floor of the passenger compartment, and sparks generated by a shor t of a PTC heater located within the dashboard.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### These were believed to be the worst-case ignition sour ces. Based on previous reports, a number of other ignition sources ( e.g. , lit cigarettes/cigars, electrical cigarette li ghters, vehicle clocks and radios) do not have the potential to ignite the flammable AR under consideration.

Input values for the passenger-associated flammability FTAs are given in Tables 6 and 7 below. Many of the values are shared with the toxicity fau lt trees but a number of parameters, particularly those relating to smoking and other possible ignition sources, are novel. Input values for these scenarios were

taken from the studies of Jetter et al . (2001), Blackwell et al . (2006) and CRP150 or were based on input

from CRP1234 members.

Table 6. Inputs for Passenger Scenar io Fault Trees Addressing Flammability Parameter Value Basis

Average time vehicle is operated per year 340 Blackwell et al. , 2006

Probability passenger smokes 0.21 Percentage of adults in U.S. who smoke. MMWR, 2005. Fraction of time spent in vehicle lighting cigarette 0.003 The average smoker consumes 17 cigarettes per day (MMWR, 2005) or 6,205 per year. Assuming 1/8th of cigarettes are consumed while driving (Blackwell et al ., 2006), this is 776 cigarettes per year smoked in the car. Assuming 5 seconds to light each cigarette, the fraction of the total y early amount of time spent in the vehicle that involve s lighting a cigarette is 776*5 seconds/340 hr = 0.003. Probability cigarette is lit with butane lighter or match ( i.e. , not electric lighter) 0.5 Blackwell et al. , 2006

Sudden leak in passenger compartment 4.6E-8 per hr VDA field data indi cate 4E-4 is the probability of a leaking evaporator. The field data average is approximately 1E-4 and a factor of 4 was applied to account for lifetime influence. This value is divided by 8,760 hr/yr. Probability leak size is Small 0.94 Medium 0.05 Large 0.01 Based on OEM expert opi nion and understanding of the corrosion process. Also based on Jetter et al., 2001 which indicated that l eaks of a significant size (1-3 grams per minute) are exceptionally rare. Probability doors and windows are closed when AC system is in use 0.95 OEM estimate based on field observation.

Probability vehicle is in recirculation mode when AC system in use 0.32 OEM updating of Jetter et al. 2001 value (0.2) based on expert opinion. Probability vehicle is in outside air mode when AC system in use 0.68 OEM updating of Jetter et al. 2001 value (0.8) based on expert opinion. Number of occupants per vehi cle 1.59 Average value, Jetter et al. 2001 Probability smoking related ignition source ( i.e ., lighter, match) is within flammable zone Small leak = 0.2 Med. leak = 0.4 Large leak = 0.6 Preliminary value. Refined for specific AR based on modeling results.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### Table 6. Inputs for Passenger Scenar io Fault Trees Addressing Flammability Parameter Value Basis

Probability vehicle has interior battery 0.05 This value currently does not include hybrid vehicles that will come into se rvice in the future. Probability of external short with a battery located inside vehicle * 1E-7 Does not include “jumper cable” situations where vehicle door will be opened. Probability sufficient energy released in battery system short 1.0 OEMs agreed to assume such a short will exceed minimum ignition energy. Probability battery short occurs within flammable zone Small leak = 0.0 Med. leak = 0.1 Large leak = 0.5 Preliminary value. Refined for specific AR based on modeling results. Probability that vehicle has a PTC heater 0.30 Value for Europe, value for U.S. would be much lower (currently <1%). Probability that PTC heater is in use 0.1 The PTC heater is used 6 months of the year (factor =0.5) and only during cold starts (factor=0.2). Frequency of fault from PTC heat er 1E-5 Based on OEM opinion. Probability sufficient energy released during interior PTC heater fault 1.0 OEMs agreed to assume such a short will exceed minimum ignition energy.

Probability PTC heater short is within flammable zone Small leak = 1.0 Med. leak = 1.0 Large leak = 1.0 Based on location of PTC heater.

AR concentration in passenger compartment exceeds LFL 0 or 1 Determined from CFD and/or field measurements.

*Applies to design intent electrical circuits and excludes any after market alteration of the vehicle



### For the collision scenario involving leaks into the passenger cabin it should be noted that the CRP1234 members assumed that any sparks associated with a collision ( e.g. , from grinding or rubbing metals parts either within the cabin or the AC duc twork) would have sufficient energy to ignite the

material and would occur in the same time frame in which a release reaches the flammable range. CRP1234 team members acknowledged that this is a highly conservative assumption that would be expected to overestimate poten tial risks in this scenario.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### Table 7. Inputs for Passenger Scenario (C ollision) Fault Trees Addressing Flammability Parameter Value Basis Number of occupants per vehi cle 1.59 Average value, Jetter et al. 2001 Occupant survives collision 0.9 Jetter et al ., 2001 Probability occupant does not escape vehicle 0.2 OEM members felt the value should be between 0.1 and 0.2 and elected to use the more conservative value of 0.2 in the analysis. Probability evaporator piping fails and refrigerant is released 0.05 Based on OEM expert opinion

Probability collision deforms Apillar >6“ 0.0187 OEM data.

Frequency of serious collision 5.6E-3 per yr Blackwell et al ., (2006) value of 8E-4 per year updated with VDA data from Statistisches Bundesamt Probability collision does not break windows and windows not already open 1E-4 Based on OEM expe rt opinion. Actual data suggest the value is near zero.

Probability collision does not break any other component in refrigerant cycle 0.1 Estimate from U.S. Department of Energy.

Probability collision produces sparks with sufficient energy to ignite material 1.0 It was conservatively assumed that sparks associated with a collision ( i.e ., collision-related sparks located inside passenger compartment) would be sufficient to ignite the material. The likelihood of a collision producing such sparks within the passenger compartment may in reality be quite low. In addition, this assumption may be overly conservative for refrigerants with very high minimum ignition energies.



### 2.6.2 Fault Trees for Engine Compartment AR Ignition Scenario

With respect to the engine compartment scenario , there is only one fault tree, corresponding to risk of AR ignition (since passengers are not presen t in the engine compartment the release is not evaluated in terms of human health risk). Input valu es for this scenario are given in Table 8. Input values

were taken from the studies of Jetter et al . (2001), Blackwell et al . (2006) and CRP150 or were based on new input from CRP1234 members.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### Table 8. Inputs for Engine Compartment Scenario Fault Trees Addressing Flammability Parameter Value Comment Number of occupants per vehi cle 1.59 Average value, Jetter et al. 2001. Average time vehicle is operated per year 340 hr/yr Blackwell et al ., 2006.

Frequency of a large leak in the engine compartment 6.8E-10 /yr Based on the frequency of a leak (4.6E-8 p er hr) multiplied by the probability the leak is large and the factor accounting for the effect of inadequate repair.

Probability of battery cable short* 1E-5 This was the scenario OEM representatives felt had sufficient energy to be a possible ignition

source. Probability sufficient energy released from battery cable short to ignite material. 1.0 Based on OEM expert opinion.

Probability battery cable short occurs within flammable concentration zone 0 or 1 Based on field data.

Probability manifold temperature exceeds autoignition temperature 0.05 Exhaust manifold temperature only reaches autoignition temperature (405°C) during high work phases ( e.g., climbing hills) . Probability hot component is within flammable concentration zone 0 or 1 Based on field data. Probability the refrigerant is actually ignited by the hot engine component 0 or 1 Based on field data.

Probability HFO-1234yf concentration in underhood area exceeds LFL 0 or 1 Based on field data.

*Applies to design intent electrical circuits and ex cludes any after market alteration of the vehicle.



### 2.6.3 Fault Trees for Vehicle Repair Scenarios

2.6.3.1 Fault Trees Related to Health Risks for Vehicle Repair Workers

The fault tree for repair workers is very similar to that used by U.S. EPA in their 2005 evaluation of R-152a and CO2 in terms of the professional repair workers. With respect to the DIY workers, the fault tree is similar although the exposure variable is based on modeling results for the two exposure subscenarios. As with the passenger fa ult trees, a value of either 0 or 1 is used to indicate whether the predicted air concentration in the repair area exceeds the mRCL.

Input values for the FTAs are given in Table 9 below. As with the passenger scenario FTAs, input values for these scenarios were taken from the studies of Jetter et al . (2001), Blackwell et al . (2006) and CRP150 or were based on input from CRP1234 members.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 40 Gradient CORPORATION Table 9. Generic Inputs for Repair Worker Fault Trees 

### Addressing Health Effects

Value Input Parameter USA Europe Basis

Vehicle AC systems serviced annually 22,000,000 7,236,000 Estimates suggest 20 to 25 million AC systems are serviced annually in U.S. (Carley, 2004). OEM data used for EU estimate. Probability work is carried out by a trained technician 0.97 0.99 MACs meeting, August 2003.

Probability work is carried out by a DIYer 0.03 0.01 MACs meeting, August 2003.

Frequency of sudden leak from vehicle system during service 0.005/yr 0.005/yr Jetter et al. (2001) survey for U.S. data. In EU, it assumed to be the same as USA.

Sudden leak from AC service equipment 0.001/serviced vehicle/yr 0.001/serviced vehicle/yr Jetter et al . (2001). Only applicable for amount of serviced vehicles , not complete fleet. Probability of inadequate ventilation in professional shop 0.10 0.10 Expert opinion base d on discussions at the MACS meeting, 2008.

Probability of inadequate ventilation in DIY location 0.20 0.20 Expert opinion base d on discussions at the MACS meeting, 2008. Probability air concentration exceeds health-based limit. 0 or 1 0 or 1 Based on results of modeling.



### 2.6.3.2 Fault Trees Related to AR Igniti on Risks for Vehicle Repair Workers

The fault tree used to assess flammab ility risks for repair workers is very similar to that used to assess health risks but contains unique inputs relating to potential ignition sources ( i.e ., smoking and equipment sparks). FTA input values are given in Ta ble 10 below. As with the passenger scenario FTAs, input values for these scenarios were taken from the studies of Jetter et al . (2001), Blackwell et al . (2006) and CRP150 or were based on new input from CRP1234 members.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 41 Gradient CORPORATION Table 10. Generic Inputs for Repair Worker Fault Trees 

### Addressing Flammability

Input Parameter Value Basis Vehicle AC systems serviced annually 22,000,000 (U.S.) 7,236,000 (Europe) Estimates suggest 20 to 25 million AC systems are serviced annually in U.S. (Carley, 2004). OEM data used for EU estimate.

Probability work is carried out by a trained technician 0.97 MACs meeting, August 2003.

Probability work is carried out by a DIYer 0.03 MACs meeting, August 2003.

Frequency of sudden leak from vehicle system during service 0.005/yr Jetter et al. (2001) survey for U.S. data. In EU, this is not relevant: Technicians wear gloves and goggles and all pressure testing is done with vacuum or nitrogen. Sudden leak from AC service equipment 0.001/serviced vehicle/yr Jetter et al . (2001). Only applicable for amount of serviced vehicles , not complete fleet. Probability of inadequate ventilation in professional shop 0.10 OEM opinion.

Probability of inadequate ventilation in DIY location 0.20 Value agreed upon during Team 1 call on June 12, 2007 Probability that high energy generating activities are occurring in a professional repair shop. 1E-3 OEMs agreed to a ssume that these activities could produce sufficient energy to ignite the material if the source was in the flammable

Probability that welding, grinding, or other high energy generating activities are occurring at a given time in a DIY location 1E-5 OEMs agreed to a ssume that these activities could produce sufficient energy to ignite the material if the source was in the flammable region.

Probability employees smoke in a professional repair shop 0.01 OEM opinion.

Probability smoking occurs in a DIY location 0.10 OEM opinion.



### 2.6.4 Interpretation of FTA Results

Risk estimates from FTA by themselves are of little value unless they can be placed in proper context. Clearly, in an idealized world we would a ll opt for situations which present no risk whatsoever. Unfortunately, all facets of life involve some elemen t of risk. Life involves the identification and selection of activities that present an acceptable level of risk, based on the knowledge available about the risk involved. With this in mind, the risks associat ed with AR exposure developed in the FTA analysis are compared to common risks of death and injury re ported in the literature. This allows the automotiveG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### manufacturers not only to weigh risks of one AR against another, but also to consider the significance of individual AR risks in an appropriate context.



## 2.7 Sources of Uncertainty in the Risk Assessment

As with any risk assessment, the pr esent work contains a number of sources of uncertainty that make the resulting risk estimates themselves are uncertain. Ho wever, in each area of uncertainty, an effort was made to err on the side of over predicting rather th an under predicting actual risks since the goal of this

risk assessment is to ensure the cho sen AR does not pose a threat to human health or the environment. Areas of uncertainty present in the risk assessment include the following:

• Modeling Uncertainty – Both the CFD and perfect mixing models require simplification of the real world situation. It is possible that deta ils not included in the models could affect processes such as airflow patterns and cause inaccurate results . While such errors may be possible, the magnitude of their effect is likely to be sma ll relative to the margin of safety present in the

Hazard Indices calculated in the risk assessment. That is, one would not expect inclusion of such

details in the models to cause a 50% increase in the predicted air concentration. In addition, with respect to the passenger compartment modeling, it should be noted that the work involved a

worst-case vehicle situation. Because the results of the modeling were applied across the entire vehicle fleet, the final risk estimates can be expected to be unrealistically high.

• Measurement Uncertainty – Measurement uncertainty concerns the ability of test instruments or protocols to accurately detect the parameter of inte rest. This type of uncertainty is present in both the bench top testing of flammability parameters and in the field assessment of AR concentrations and ignition potential. In both cases, tests were designed to reflect worst-case situations. For example, in the field testing, the vehicle was st ationary and shielded from external airflow, both

factors which minimized dilution of the released material and maximized contact with the potential ignition source. As noted in the Exponent report HFO-1234yf Refrigerant Concentrations and Ignition Tests in Full-Scale Vehicle Passenger Cabin and Engine Compartment (Exponent, 2008), there was also some degree of measurement bias in the sensor measurements of HFO-1234yf in those cases where senso rs were used more than once. However, the level of error associated with this phenome non is believed to be sm all and relatively minor compared to test-to-test variability and the overa ll conservativeness of the vehicle test relative toG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### real-world conditions. Thus, in this risk assessm ent, the measurement uncertainty was generally

biased towards overestimation rather than underestimation of real world risks.

• Parameter Uncertainty – A number of the parameters used in the FTA were based on expert judgment and only limited data. In many cases, the values reflect conservative assumptions that are likely to result in overestimates of the actual ri sks. For example, OEM data suggest that the probability of a vehicle sustaining sufficient damage in a collision such that the evaporator tube is rupture but the windows remain unbroken is close to zero. The fact that this probability was

assumed to be 1 x 10 -4 

### reflects a desire on the OEMs to err on the side of being conservative when data are lacking. Similarly, air exchange rates used in the repair scenario modeling (for both the professional shop and DIY location) are likely unrealistically low for most facilities. Since the results of that analysis were used to represent risks associated with all vehicle AC repair operations, the predicted risks are again likely to be overly high.

• Toxicological Uncertainty – There are a number of uncertainties involved in applying toxicological data obtained with experimental anim als in a risk assessment of human health risks. Studies typically involve a limited number of animals per dose group, the species involved may not be as sensitive as humans, and specially sen sitive subpopulations may exist in the human population which are not addressed by the uniform strains of animals used for experimental testing. These uncertainties are addressed by ag ain being cautious in the application of the toxicological data. For example, endpoints based acute toxicity are obtained from animal studies which generally involve 4 hours of continuous exposure to the test compound whereas human exposures would be expected to be substan tially shorter based on the modeling results. Furthermore, human health-based exposure crite ria used in the risk assessment were based on either a No Observed Adverse Effect Level (NOAEL) from the animal study ( e.g. , for cardiac sensitization) or an effect level divided by a safety factor ( e.g. , for acute toxicity or anesthetic potency). These values are biased towards the conservative. Fo r example, exposures somewhat above the NOAEL may not produce any adverse effects, the NOAEL is simply the highest dose

tested where effects were not seen.

Based on the rationale stated above, it can be reasona bly expected that the ri sks associated with AR exposures developed in this risk assessment are likely to be greater than risks experienced by real world vehicle passengers or repair personnel. This is appropriate if one goal of the risk assessment is to ensure health and safety.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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## 3 Summary of R-12 Risk Assessment

To validate the risk assessment methodology (and in particular the air modeling component) we first conducted an assessment of R-12, the refrigerant in use prior to R-134a. We evaluated R-12 as if it were a potential AR, even though the ODP of this materi al renders this impossible. R-12 was chosen over R-134a for this purpose because it has longer history of use in mobile air conditioning. This analysis allowed us to refine the air modeling and fault tr ees and optimize modeling and data collection when we

turned to evaluation of the actual ARs. Because R-12 is not flammable, the risk assessment only dealt with potential health risks and did not include an analysis of the risks of potential AR ignition.



## 3.1 General Properties

Dichlorodifluoromethane (R-12, CFC-12) has primarily been used as a refrigerant and aerosol propellant and, to a lesser extent, as a blowing agen t in the production of foam products (NRC, 2000). R-12 is a gas at standard temperature and pressure with a boiling point of -29.8°C (NRC, 2000; ACGIH, 2001). Like most other refrigerants, R-12 is fairly stable but may decompose into toxic and corrosive gases (hydrogen chloride, phosgene, hydrogen fluoride, carbonyl fluoride) when in contact with hot surfaces or flames (NIOSH, 2002; ACGIH, 2001). The ODP of R-12 has been designated as 1.0, the same value as assigned to R-11 (U.S. EPA, 2007). The GWP of R-12 has been reported to be 10,600,

relative to CO 2 

### (U.S. EPA, 2007). R-12 is non-flammable according to ASHRAE test requirements (NRC, 2000).

Reacting to the environmental threat of ozone depletion from CFCs, the 1987 Montreal Protocol established requirements that began the worldwide phaseout of ozone-depleti ng CFCs. All developed countries agreed to phase out production of most ozone -depleting substances, including CFCs, by the end

of 1995. The 1990 Clean Air Act Amendments in the U.S. incorporated this production end date and directed U.S. EPA to develop regulations to maxi mize recycling, ban nonessential uses, develop labeling requirements and examine safe alternatives for ozone -depleting substances. On December 31, 1995, R-12 production essentially ended in the US. Production in the European Union countries was phased out in the same time frame. Limited production of R-12 for “essential uses” ( e.g. , for use in medical inhalers) is permitted under U.S. and E.U. regulations until suitable replacements are developed (IPCC, 2005).G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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## 3.2 Toxicity Assessment

3.2.1 Summary of Toxicological Findings

The toxicology of R-12 has been extensively discussed in a number of publications (WHO, 1975; NRC, 1984, 2000; U.S. EPA, 1987) and therefore only the key studies are described in this section.

When inhaled, R-12 has very low acute toxicity and acts like a weak narcotic (ACGIH, 2001). The inhalation lethal concentrations (LC 50 

### ) of R-12 in rats after 30-minute and 2-hour exposures are 800,000 ppm (Ritchie et al. , 2001) and 600,000 ppm (Scholz, 1962), respectively. In guinea pigs exposed to R-12 at concentrations ranging from 21,000 to 304,000 ppm for time durations of between 5 and 120 minutes, 51,000 ppm was found to be a NOAEL for a ll times up to 2 hours (Nuckolls, 1933). Ritchie et

al. (2001) also evaluated neurobehavioral toxicity in rats exposed for up to 30 minutes to R-12. Rats were exposed while performing in either a rotarod/ motorized running wheel apparatus (rotawheel) or in an operant chamber. The results indicated that 3 to 20 minutes of exposure to R-12 at concentrations ranging from 140,000 to 470,000 ppm induced acute ne urobehavioral effects ranging from operant performance deficits to anesthesia with occasional convulsions. A NOAEL was not defined in this study

because the authors increased concentr ations across the dose range during the course of the experiment rather than evaluating specific concentrations. The finding of increasingly severe effects starting at 140,000 ppm is consistent with the NOAEL of 51,000 ppm reported by Nuckolls (1933). As regards data in humans, Azar et al. (1972) exposed two human volunteers to concentrations of 1,000 and 10,000 ppm of R-12 for 2.5 hours. There were no adve rse effects resulting from exposure to 1,000 ppm. Exposures to 10,000 ppm resulted in an apparent slight reduction in some standardized test scores (a card sorting and clerical test), although the data are di fficult to interpret given that there were only two subjects and considerable inter- and intra-s ubject variability in test performance.

Cardiac sensitization to epinephrine, resulting in multiple ventricular beats or cardiac arrest, has been observed in dogs inhaling R-12 at 50,000 ppm for 5 minutes (LOAEL) but not at 25,000 ppm (NOAEL) (Reinhardt et al ., 1971; Trochimowicz and Reinhardt, 1975). It should also be noted that Kehoe (1943, as cited in NRC, 2000) reported a "si gnificant degree of cardiac arrhythmia" in a single human volunteer exposed to 110,000 ppm R-12 for 10 minutes. This single case report in a human does not provide sufficient data to establish a safe exposure le vel but is consistent with the reported findings in dogs.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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### As regards longer term studies, Scholz reporte d that 4 weeks of 3.5-hour exposures at 100,000 ppm R-12 produced no pathologic changes in guinea pigs , rats, cats, or dogs (Scholz, 1962). In another study, rats, monkeys, dogs, rabbits, and guinea pi gs were exposed to 810 ppm R-12 twenty-four hours/day for 90 days (Prendergast et al ., 1967). There were no treatment-related adverse effects in rats, monkeys, dogs or rabbits. Some microscopic effects we re seen in the livers of treated guinea pigs but the authors expressed uncertainty that the effects were treatment related. A 90-day NOAEL from a later study conducted in rats was repor ted to be 10,000 ppm (Leuschner et al. , 1983). Stewart et al . (1978) found that repetitive exposures (8 hours per day, 5 da ys per week, for 3.5 weeks) of eight human volunteers at 1,000 ppm were without adverse cardiac, respiratory, or CNS effects.

R-12 was found to be negative for genotoxicity in various experimental systems: the Ames assay, the BHK21 cell-transformation assay, the CHO/HPRT assay, and the dominant lethal assay (Longstaff et

al. 1984; Longstaff 1988; Krahn et al. 1980; ACGIH, 2001).

Regarding the potential carcinogenicity of R-12, a study by Maltoni et al . (1988) found no exposure-related cancers in rats or mice exposed to R-12 at 0, 1,000, and 5,000 ppm repeatedly for 104 (rats) and 78 weeks (mice). The NRC (2000) noted that the highest tested concentration (5,000 ppm) might not have been sufficient to firmly establis h R-12 as noncarcinogenic. However, given the absence of genotoxicity and the lack of carcinogenicity of related compounds, it appears highly unlikely that R-12 is carcinogenic.

The available data concerning the toxicity of R-12 are summarized in Table 7. The acute and chronic toxicities of R-12 are low and the occupa tional exposure limit is correspondingly high. The compound does not appear to pose any significant specia lized toxicological risks such as genotoxicity or carcinogenicity. Studies have not been conducted to indicate whether R-12 exhibits developmental toxicity.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 47 Gradient CORPORATION Table 11. Summary of Availa ble Toxicity Data for R-12 Endpoint R-12 Reference Acute (LC50) (ppm) 600,000 Scholz, 1962 Anesthetic effect level (ppm) 51,000* Nuckolls, 1933 Cardiac sens. No effect level (ppm) 25,000 Reinhardt et al ., 1971 Worker exposure limit (ppm) 1,000 OSHA, MAK 28-day no effect level (ppm) 100,000 Scholz, 1962 90-day no effect level (ppm) 10,000 Leuschner et al ., 1983 Developmental toxicity no effect level No data Genotoxicity Negative NRC, 2000 Carcinogenicity Negative NRC, 2000

mRCL (ppm) 40,800 (based on anesthetic effects) 25,000 (based on cardiac sensitization) ODP 1.0 Montreal Protocol GWP 10,600 U.S. EPA, 2007 *The value from the Nuckolls (1933) study is a no effect level. For calculating the mRCL, 80% of this value was used, as described in the ASHRAE/ANSI standard. ** This was the only dose tested in a 90-day study. Th e true no effect level is likely to be much higher.



### According to the U.S. EPA SNAP regulations, each new AR will also be evaluated in terms of potential health risk relative to the current MAC re frigerant, R-134a. We therefore also compared key toxicity indices for R-12 to those associated with R-134a in Table 12 below.

Table 12. Comparison of Toxicity of R-12 to the Toxicity of R-134a Endpoint R-12 R-134a Acute (LC50) (ppm) 600,000 >500,000 Anesthetic effect level (ppm) 51,000* 81,000 Cardiac sensitization no effect level (ppm) 25,000 50,000 Worker exposure limit (ppm) 1000 1000 28-day no effect level (ppm) 100,000 50,000 90-day no effect level (ppm) 10,000 50,000 Developmental toxicity no eff ect level (ppm) No data 50,000 Genotoxicity Negative Negative Carcinogenicity Negative Negative

mRCL (ppm)** 40,800 (based on anesthetic effects) 25,000 (based on cardiac sensitization) 50,000 (cardiac sensitization)

ODP 1 0 GWP 10,600 1410 Flammability Not Flammable Not Flammable Shading highlights values indicating greater t oxicity/environmental hazard compared to R-134a. * This value is a no effect level.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 48 Gradient CORPORATION 

### 3.2.2 Toxicity Criteria Used for Risk Assessment

As indicated in Section 2.2.8, we have adapted the ANSI/ASHRAE RCL methodology for use in

this risk assessment. The mRCL values for R-12 are 25,000 ppm based on cardiac sensitization potential and 40,800 ppm based on anesthetic properties. As indicated in Section 2.2.8, these will be compared to the 5-minute and 30-minute TWA air concentrations, respectively, based on whether the exposure scenario in question involves potential stress.

Based on the available toxicological data and lack of flammability, R-12 is classified as a "A1" refrigerant in terms of the ANSI/ASHRAE safety groups.



## 3.3 Results of Exposure Assessment

For the passenger exposure scenarios, air mode ling was conducted using various leak sizes, vehicle speeds, system pressures, etc ., as described in Table 13 below.

Table 13. Passenger Modeling Scenarios for R-12 Evaluation (R-12 Simulation Key)

Sim #

Vehicle Condition Blower Status Leakage Condition - Evaporator hole diameter Air Exchange Rate Mode Temperature Behind Orifice or Behind Evap Leak Hole. Venting to Atmospheric

Pressure Sim 1 1.8 ACH Recirc Sim 2 Small leak (0.01 mm) 

### 34.3 ACH Outside air Sim 3 1.8 ACH Recirc Sim 4 Medium leak (0.1 mm) 

### 34.3 ACH Outside air Sim 5 1.8 ACH Recirc Sim 6 All at Idling All at Low (60 cfm) Large leak (0.5 mm) 

### 34.3 ACH Outside air All at 0.5 MPa At 15 C Quality = 0.5

All outlet flow through rear package shelf. Charge=833g, Unoccupied 270 g/m 3 , Occupied 298 g/m 3



### Results of the air modeling are shown in Table 14 be low. More detail concerning the passenger exposure modeling for R-12 may be found in the CRP150 risk assessment.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 49 Gradient CORPORATION Table 14. Predicted Passenger Compartment R-12 Concentrations

Sim # Simulation Conditions Peak 5-minute TWA (ppm) Peak 30-minute TWA (ppm) Sim 1 Vehicle idling, low fan, sm all leak (0.01 mm orifice), 1.8 ACH, 0.5 mPa pressure behind leak, recirc mode 55 55

Sim 2 Vehicle idling, low fan, sm all leak (0.01 mm orifice), 1.8 ACH, 0.5 mPa pressure behi nd leak, outside air mode 2.9 2.9

Sim 3 Vehicle idling, low fan, medium leak (0.1 mm orifice), 1.8 ACH, 0.5 mPa pressure behind leak, recirc mode 5,490 5,490

Sim 4 Vehicle idling, low fan, medium leak (0.1 mm orifice), 1.8 ACH, 0.5 mPa pressure be hind leak, outside air mode 289 289

Sim 5 Vehicle idling, low fan, la rge leak (0.5 mm orifice), 1.8 ACH, 0.5 mPa pressure behind leak, recirc mode 35,000 28,720

Sim 6 Vehicle idling, low fan, la rge leak (0.5 mm orifice), 1.8 ACH, 0.5 mPa pressure behi nd leak, outside air mode 7,067 2,867



### Air modeling for repair workers (both professionals and DIYers) who may be exposed to R-12 was

carried out as described in Section 2.3.3. Results of the air modeling simulations are summarized in

Table 15.

Table 15. Results of Air Modeling for Repair Worker Scenarios, R-12

Scenario Predicted R-12 Concentration (ppm) Professional repair – complete charge loss due to rupture (5-minute TWA) 708

Professional repair – hose leak during system drain and recharge (30-minute TWA) 139

DIY – Scenario 1, slow loss of heel from 2 cans of R-12 (30-minute TWA) 2,182

DIY – Scenario 2, leak from charge kit while charging system (30-minute TWA) 30,896



### A series of graphs, indicating the predicted air concentrations over time that are associated with each repair scenario are included as Attachment B.



## 3.4 Risk Characterization

Results of the air modeling for passenger exposur es indicated that refrigerant releases associated with a large leak in recirculation mode w ould result in an unacceptable level of risk ( i.e. , HI>1.0). Predicted exposure levels were below the mRCL for all small and medium leak scenarios, and for the large leak scenario involving a vehicle operated in out side air mode. Modeling was not conducted for theG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 50 Gradient CORPORATION 

### collision scenario. However, the leak involved in a rupture of the AC piping (as envisioned in the collision scenario) would be greater than that considered by the large leak, and thus a leak associated with

a serious collision would result in air concen trations above the health-based limit.

For the vehicle repair scenarios, none of the m odeled air concentrations exceeded the relevant mRCL. As a result, the vehicle repair scenarios di d not contribute to risks calculated in the FTA.

The calculated HIs for all of the R-12 scenarios are shown in Table 16, below.

Table 16. Hazard Indices Associated with Different Exposure Scenarios, R-12 Scenario Predicted R-12 Concentration (ppm) Health-Based Comparison Value (ppm) Hazard Index

Passenger Exposure Scenarios Small leak, recirc mode 55 40,800* 0.001 Small leak, outside air 2.9 40,800* 0.00007 Medium leak, recirc mode 5,490 40,800* 0.13 Medium leak, outsi de air 289 40,800* 0.007 Large leak, recirc mode 35,000 25,000** 1.4 Large leak, outside air 7,067 25,000** 0.28 Collision not modeled 25,000** >1.4 Repair Worker Exposure Scenarios Professional repair – system rupture 708 25,000** 0.03 Professional repair – hose leak during system drain and recharge 139 40,800* 0.003

DIY – slow loss of heel from 2 cans 2,182 40,800* 0.05 DIY – charge kit leak while charging system 30,896 40,800* 0.76

* Based on anesthetic properties. ** Based on cardiac sensitization potential because the exposure scenario involves potential stress

.



## 3.5 FTA

Fault trees related to the risk assessment of R-12 are shown in Figures 4 through 9. As indicated in these figures, for the small and medium leak s ituations, concentrations of R-12 in the passenger compartment are not predicted to exceed health-based limits. The FTA risks associated with these fault tree branches are therefore zero. With respect to the large leak scenarios, the fault tree involving the

vehicle in recirculation mode is associated with an air concentration above the health-based limit, whereas the vehicle with a large leak while in outside air mode does not achieve an air concentration above the limit. With respect to the vehicle collision scenario , air modeling data are not directly available toG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 51 Gradient CORPORATION 

### evaluate the potential risks with certainty. However, given that the HI for the large leak (0.5 mm) scenario (recirculation mode) substantially exceeds the health based limit, and given the larger leak size contemplated by the collision scenario ( i.e ., 1.45 or 2.3 mm), R-12 concentrations in the passenger cabin can be expected to exceed health-b ased limits, at least in the event of the extreme collision scenario as

described. The risks associated with this fault tree branch were therefor e retained in the FTA. HI values for vehicle repair scenarios never exceeded 1.0 and therefore the contribution of these exposure scenarios

to overall risk is zero. The final estimated risk s from the FTA are 11 per year, in both the U.S. and Europe. These risks are largely due to the large leak scenario associated with the vehicle in recirculation mode. The collision scenario contributes negligibly to the overall risk.



## 3.6 Conclusions Regarding R-12

The overall result of the FTA was an estimate of 11 refrigerant exposures above health-based limits per year to R-12 in the U.S. and in Europe. Wh ile the number of vehicles in the fleet in Europe is somewhat higher, the difference when multiplied agai nst the low frequency is less than 1 exposure per year. To place this number in perspective, if divide d by the number of drivers currently registered in the U.S. (200 million), the annual risk per driver would be 5.5 x 10 -8 

### per year. This value is comparable to the reported risk of being injured in an elevator ride (2x10 -7 

### ) and substantially less than the risk of dying during a 5,000-mile plane trip (2x10 -6 

### ).G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 52 Gradient CORPORATION 

## 4 Risk Assessment – HFO-1234yf

4.1 General Properties

The joint DuPont Honeywell product is 2,3, 3,3-tetrafluoropropene (HFO-1234yf). HFO-1234yf is a new proprietary chemical being developed by th e companies and has been s ubjected to an extensive battery of evaluations. HFO-1234yf is slightly fla mmable; the LEL is 6.5% (65,000 ppm) at 21°C and the minimum ignition energy is greater than 1,000 mJ (DuPont/Honeywell, 2007). Thus, in addition to toxicity, the potential flammability of HFO-1234yf is a concern for the risk assessment.

The occupational exposure limit established by Honeywell for HFO-1234yf is 1,000 ppm. Studies by Honeywell have indicated that the ODP of HFO-1234yf is zero (Dupont/Honeywell, 2007). The GWP of the HFO-1234yf has been estimated to be 4 (Nielsen et al., 2007). Thus, the chemical will satisfy the EU F-gas directive.



## 4.2 Toxicity Assessment

4.2.1 Evaluation of Available Toxicity Data from Manufacturer

Honeywell has provided results for a large number of studies conducted on HFO-1234yf. These consisted of the following laboratory reports:

Mammalian Toxicity

 

### 4-hour inhalation range finding study in the m ouse (Huntingdon Life Sciences, March 11, 2004)

 

### 4-hour inhalation screening study with micronuc leus assay in rats and mice (Huntingdon Life Sciences, March 30, 2004)

 

### 14-day inhalation study in ra ts (TNO, November 4, 2005)

 

### Chromosomal aberration test in cultured human lymphocytes (TNO, November 8, 2005)

 

### Bacterial reverse mutation test (Ames Assay) (TNO, November 15, 2005)

 

### Micronucleus test in bone marrow cells of mice treated via inhalation (TNO, November 23, 2005)

 

### 4-hour inhalation toxicity test in rats (TNO, January 17, 2006)G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 53 Gradient CORPORATION  

### Toxicogenomic assessment of carcinogenic potential (H amner Institutes for Health Sciences, May 26, 2006)

 

### Cardiac sensitization study in dogs (WIL Research Laboratories, August 23, 2006)

 

### 4-week (28-day) inhalation toxicity study in rats, including unscheduled DNA synthesis and micronucleus test results (TNO, September 5, 2006)

 

### Prenatal developmental inhalation toxic ity study in rats (TNO, April 17, 2007)

 

### 13-week (90-day) inhalation toxicity test in rats (TNO, May 11, 2007)

Ecological Toxicity

 

### Preliminary experiment for developing methods to ma intain test concentrati ons in aquatic toxicity tests (TNO, May 5, 2006)

 

### Freshwater algal growth inhibition test (TNO, May 8, 2006)

 

### Acute toxicity study in Daphnia magna (TNO, May 8, 2006)

 

### 96-hour acute toxicity study in carp (TNO, June 15, 2006)

At the time of this report, Honeywell has complete d a full range of toxicity testing on HFO-1234yf. Honeywell is currently conducting an optional de velopmental toxicity test in a second species ( i.e ., rabbits), and is starting a 2-genera tion reproductive toxicity test whic h would be required by European authorities when commercial imports reach certain size limits. In lieu of a full 2-year carcinogenicity study, Honeywell has conducted a 13-week inhalation exposure in rats and mice followed by a genomic carcinogenicity examination. Honeywell has reviewed the study design with both the U.S. EPA and with a European ( i.e. , Belgian) regulatory agency before initiating the toxicology program, and has not received any objections to the approach. Honeywell has indicated it would perform a 2-year carcinogenicity study if required by regulatory author ities; however, given the lack of activity in the mammalian mutagenicity assays, the lack of specific or gan toxicity in the 13-week inhalation study, and the lack of a positive carcinogenic response in th e genomic assays, the probability that HFO-1234yf would show a positive response is considered by the Honeywell Director of Toxicology to be low.

Honeywell's toxicity testing was conducted prim arily at TNO Laboratories in the Netherlands. TNO is one of the largest toxicology research labor atories and has a solid reputation. Some work (including the cardiac sensitization study of HFO-1234yf) was conducted at WIL Research Laboratories

in the U.S. WIL is another well recognized toxicological testing laboratory with experience in cardiac sensitization testing (Chengelis, 1993; 1997). The fina l research laboratory used, the Hamner InstitutesG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 54 Gradient CORPORATION 

### for Life Sciences, conducted the genomics study. Hamn er (formerly the Chemical Industry Institute of Toxicology) is also well regarded and specializes in cutting edge research.

For each of the toxicity studies identified above, Gradient was able to obtain the final and complete laboratory report and reviewed the methodology , data generated, and c onclusions. Based on the information provided in the study reports, most of the studies appear to have been conducted appropriately, using standard methodology. The onl y exception may be the cardiac sensitization study. The Honeywell cardiac sensitization study appears to have several design elements that may be less conservative than the standard test. The study used baseline epinephrine doses in some dogs that did not produce any arrythmiogenic effect ["the highest dose le vel tested during the pre-study evaluation that did not elicit significant ECG findings ( e.g. , PVC)"] rather than a minimally arrythmiogenic effect (the standard method). In addition, Honeywell/WIL used th e criterion of eleven or more premature ventricular contractions in 10 seconds to identify an adverse eff ect. This particular criterion has not been cited elsewhere. These study design differences would be exp ected to have fairly limited effects on the final outcome of the study. Given that the cardiac sensitization NOAEL of HFO-1234yf is 120,000 ppm (the highest dose tested), these study design differences shoul d not be a barrier to adoption of the chemical.

It should be noted that in discussions with Honeywell about the cardiac sensitization study, the company indicated that the study was conducted in the same manner as previous studies and that differences in terminology ("minimally arrythmiogenic" vs "no significant ECG findings") do not indicate differences in study design.

4.2.3 Summary of Toxicological Findings

The available data concerning the toxicity of HFO-1234yf are summarized in Table 17. Overall the acute and chronic toxicity of HFO-1234yf appear to be low. Based on the toxicological data provided by Honeywell, as well as the flammable nature of the chemical, HFO-1234yf would be placed into the "A2" ANSI/ASHRAE safety group and into the A2L ISO 817 safety group.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 55 Gradient CORPORATION Table 17. Summary of Available Toxicity Data for HFO-1234yf Endpoint HFO-1234yf Acute (LC50) (ppm) >405,800 (TNO, 2006a)* Anesthetic effect (ppm) >405,800 (TNO, 2006a)* Cardiac sens. No effect level (ppm) 120,000 (WIL, 2006) Worker exposure limit (ppm) 1,000 (Honeywell 8-hr value) 28-day NOAEL (ppm) 50,000 (TNO, 2006f) 90-day NOAEL (ppm) 50,000 (TNO, 2007b) Developmental toxicity NOAEL (ppm) 50,000 (TNO, 2007a) Genotoxicity Negative (Huntingdon, 2004;2005b,c,d; 2006f) Carcinogenicity Screen Negative (Hamner, 2006) Aquatic toxicity (mg/L) A cceptable (TNO 2006c,d,e) mRCL (ppm)* 120,000 (based on card. sens.) 115,000 (based on acute toxicity) ODP 0 (Dupont/Honeywell, 2007) GWP 4 (Nielsen et al. , 2007) * Based on the highest dose tested



### According to the U.S. EPA SNAP regulations, each ne w AR will also be evaluated in terms of potential health risk relative to the current MAC refrigerant , R-134a, a comparison of key health indices for HFO1234yf relative to R-134a is included in Table 18, below.

Table 18. Comparison of Toxicity of HFO-1234yf to the Toxicity of R-134a Endpoint 1234yf R-134a Acute (LC50) (ppm) >405,800 >500,000 Anesthetic effect (ppm) >405,800 81,000 Cardiac sensitization no effect level (ppm) 120,000 50,000

Worker exposure limit (ppm) 1,000 (Honeywell 8-hr value) 1,000 (PEL) 1,000 (MAK) 28-day NOAEC (ppm) 50,000 50,000 90-day NOAEL (ppm) 50,000 50,000 Developmental toxicity NOAEL (ppm) 50,000 50,000 Genotoxicity Negative Negative Carcinogenicity Screen Negative Negative Aquatic toxicity (mg/ L) >83 (Daphnia) 450

mRCL (ppm) 120,000 (based on card. sens.) 115,000 (based on acute toxicity) 50,000 (cardiac sensitization) 141,000 (acute toxicity) 64,800 (anesthetic effects) ODP 0 0 GWP 4 1,410



### Like R134a, HFO-1234yf displays low acute and chronic toxicity. In fact, for each of the toxicological measures listed in Table 12, HFO-1234yf evidences equal or lesser toxicity compared to R-134a. TheG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 56 Gradient CORPORATION 

### Honeywell suggested worker exposure limit for HF O-1234yf (1,000 ppm) is identical to the exposure limits for R-12 and R134a. HFO-1234yf also appears to be a good substitute for R134a in terms of ODP

and GWP.

4.2.4 Toxicity Criteria Used for Risk Assessment

As indicated in Section 2.2.8, we have adapted the ANSI/ASHRAE RCL methodology for use in

this risk assessment. We have therefore es timated mRCL values for HFO-1234yf as follows:

 

### For exposure scenarios involving potentially stressful stimuli we will use a mRCL of 120,000 ppm, based on the cardiac sensitization NOAEL for Honeywell's study of HFO-1234yf (WIL Research Laboratories, 2006).

 

### For exposure scenarios not involving potentially stressful stimuli we will use a mRCL of 115,000 ppm, which was calculated as 28.3% of the maximum dose of HFO-1234yf from the acute toxicity study in rats (TNO, January 17, 2006). No te that no lethality was observed at this dose.

Note that the mRCL for non-stress involving exposures is slightly less than the mRCL based on cardiac

sensitization. The cardiac sensitization value is none theless more conservative to use in stress-related situations because this value will be compared to th e peak 5-minute TWA concentration rather than the peak 30-minute TWA.



## 4.3 Flammability Properties

As noted previously, the manufacturers of HFO- 1234yf have conducted considerable research to understand its potential for combustion. These properties are summarized in Table 19, along with comparative data for some other common refrigerants. ASHRAE Standard 34 testing indicates that the flammable range lies between 6.5 and 12.3 percent ( i.e ., 65,000 ppm and 123,000 ppm). This range is

narrower than that for R-152a and the LFL is substan tially higher, indicating a higher accumulation of gas is required before ignition is possible. The mi nimum ignition energy of HFO-1234yf appears to be exceptionally high among refrigerants that would be assigned to ASHRAE Classification 2. Tests using a 1000 mJ ignition spark were not able to ignite the material. In contrast, the minimum ignition energy of R-152a is below 1 mJ ( i.e , more than 1,000 times less than HFO-1234yf). The autoignition temperature of HFO-1234yf is similar to that of R-152a and we ll below that of R-32. However tests run byG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 57 Gradient CORPORATION 

### Honeywell on ignition of HFO-1234 vapors on hot steel surfaces up to 800C, as reported to CRP1234 members, have not shown an indication of ignition (H oneywell, 2008). It should also be noted that the inability to ignite HFO-1234yf on hot surfaces was demonstrated in engine compartment ignition tests conducted by Exponent (Exponent, 2008). Finally, the h eat of combustion and burning velocity of HFO1234yf are both fairly low, particularly in comparison to R-152a. This suggests HFO-1234yf has a weak potential to sustain a serious fire if the gas were to be ignited. HFO-1234yf has not yet received a safety classification from ASHRAE or ISO, but the known flammability properties would result in a flammability classification of 2L. A toxicity classification of A would be expected given that the current recommended occupational exposure limit is 1,000 ppm.

Table 19. Flammability of HFO-1234yf Relative to Other Refrigerants Property 1234yf R-12 R-134a R-152a R-32 LFL (% volume in air) 6.5 NA NA 3.9 14.4 UFL (% volume in air) 12.3 NA NA 16.9 29.3 Minimum Ignition Energy (mJ) >1,000 NA NA 0.38 >30, <100 Autoignition temperature (oC) 405 >750 # 

### >743 454 648 Heat of combustion (kJ/g) 9.5 -0.8* 4.2 16.5 9.4 Burning velocity (cm/s) 1.5 NA NA 23 6.7 Safety Classification A2L † 

### A1 A1 A2 A2 NA – Property not relevant for this material. Source: DuPont/Honeywell presentation 12/13/2007. * U.S. EPA, 2007. http://www.epa.gov/oz one/snap/refrigerants/safety.html # DuPont MSDS for R-12 † Anticipated ISO safety classi fication based on known properties.



## 4.4 Results of Exposure Assessment

4.4.1 Results for Passenger Compar tment Scenarios – CFD Modeling

Earlier modeling conducted as part of the SAE CRP150 effort indicated that modeling of the

recirculation and outside air use conditions were most important to the FTA. Therefore, recirculation and

outside air scenarios were evaluated for each of the three leak sizes (0.01, 0.1, and 0.5 mm holes in the evaporator face). For each simulation, the vehicle was assumed to be idling and the fan was operated at low speed. Previous modeling from CRP150 indicated that these were the most conservative options; i.e. , moving vehicles and vehicles with the fan operating at high speed yielded lower concentrations in the passenger compartment. The various CFD simulation c onditions used by DuPont are shown in Table 20.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 58 Gradient CORPORATION Table 20. CFD Modeling Scenarios Sim Number Conditions Leak Rate (g/s) 1 Vehicle idling, low fan, large leak (0.5 mm orifice), recirc mode 1.14

2 Vehicle idling, low fan, medium leak (0.1 mm orifice), outside air mode 0.04

3 Vehicle idling, low fan, small leak (0.01 mm orifice), recirc mode 0.00036

4 Vehicle idling, low fan, large leak (0.5 mm orifice), outside air mode 1.14

5 Vehicle idling, low fan, medium leak (0.1 mm orifice), recirc mode 0.04

6 Vehicle idling, low fan, small leak (0.01 mm orifice),outside air mode 0.00036



### According to DuPont, CFD modeling was only conducte d for the first 200 seconds of the leak. In the case of the large leaks with the vehicle in recircula tion mode and outside air mode, linear extrapolation

was then used to calculate the maximum concentration that would be reached at the end of the leak (at 606 seconds). From this data we were able to estimate the maximum, 5-minute, and 30-minute TWA

concentrations. The 5-minute TWA values were based on the results of the CFD modeling for 200 seconds plus linear extrapolation for the remaining time period, assuming linear decay of concentrations

after the end of the leak.

For the small and medium leak conditions (both r ecirculation and outside air), maximum, 5- and 30- minute TWA were not calculated due to the long time required to reach the end of the leak. For these situations, it was assumed that because results for th e large leak did not exceed the health-based limit, results for the smaller leaks would also be acceptable.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 59 Gradient CORPORATION Table 21. Results of Air Modeling Simulations for Passenger Scenarios, HFO-1234yf Sim Number Conditions Maximum Concentration (ppm) Peak 5- minute TWA* Peak 30- minute TWA* 1 Vehicle idling, low fan, large leak (0.5 mm orifice), recirc mode 65,000 63,000 51,000

2 Vehicle idling, low fan, medium leak (0.1 mm orifice), recirc air mode Will not exceed relevant criterion based on results for large leak 3 Vehicle idling, low fan, small leak (0.01 mm orifice), recirc mode Will not exceed relevant criterion based on results for large leak 4 Vehicle idling, low fan, large leak (0.5 mm orifice), outside air mode 

### 34,000 32,000 21,000

5 Vehicle idling, low fan, medium leak (0.1 mm orifice), outside air mode Will not exceed relevant criterion based on results for large leak 6 Vehicle idling, low fan, small leak (0.01 mm orifice),outside air mode Will not exceed relevant criterion based on results for large leak * Data for measurement point P4, which yields the highest results.



### 4.4.2 Results for Passenger Compartmen t Scenarios – Field Measurements

In addition to CFD modeling, field measurements of HFO-1234yf concentration are available from the Exponent field study (Exponent, 2008). Although Exponent collected data from multiple locations in the vehicle cabin, 3 locations are used in the risk assessment. Data for the driver’s side breathing area are used to evaluate potential health eff ects. The driver’s side breathing zone estimate is used to assess the risks of an AR ignition from sm oking, the floor value is used to assess the risks associated with a short from an internal battery, and th e duct value is used to assess the risks of a short in a PTC heater. In all cases, the maximum detected con centration is used. Data for each of these scenarios

is shown in Table 22.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 60 Gradient CORPORATION Table 22. Results of Field Measurements for Passenger Compartment Scenarios, HFO-1234yf 

### Test Maximum Measured Concentration (ppm) 

### Driver’s Breathing Area PCC1 28,721 

### PCC3 28,993 

### PCI1 22,001 

### Duct Location PCC1 23,270 

### PCC3 20,431 

### PCI1 28,254 

### Driver’s Floor Area PCC1 17,717 

### PCI1 29,774 Data from Exponent (2008). PCC= Passenger cabin test PCI = Passenger cabin ignition test (con centrations of HFO-1234yf were also measured in this test)



### 4.4.3 Results for Engine Compartment AR Ignition Scenario – Field Measurement

Exponent also measured HFO-1234yf concentrations and attempted ignition after a release in the engine compartment. Two tests were conducted to evaluate reproducibility. Results of measurements in the engine compartment were more variable than results for the passenger compartment, which is not surprising given that the engine compartment is more open to outside air and has a more complicated geometry. The highest value measured in the engine compartment (87,000 ppm, engine compartment test 1, sensor 5) suggests a potential ignition hazard. However, the engine compartment field test also showed that it was not possible to ignite the released refrigerant with the high temperature source. This suggests that, while theoretically possible, ignition and propagation of a HFO-1234yf fire in the engine compartment during normal vehicle operation is extremely unlikely

4.4.4 Results for Repair Worker Scenarios – Perfect Mixing Model

Air modeling for repair workers (both professi onals and DIYers) who may be exposed to HFO1234yf was carried out as described in Section 2.3.3. Results of the air modeling simulations are

summarized in Table 23.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 61 Gradient CORPORATION Table 23. Results of Air Modeling for Repair Worker Scenarios, HFO-1234yf Scenario Predicted HFO1234yf Concentration

(Maximum, ppm) Predicted HFO1234yf Concentration (5-minute TWA, ppm) Predicted HFO1234yf Concentration (30-minute TWA, ppm) Professional repair – complete charge loss due to rupture (5-minute TWA) 590 566 464

Professional repair – hose leak during system drain and recharge (30-minute TWA) 146 141 122

DIY – Scenario 1, slow loss of heel from 2 cans of HFO-1234yf (30-minute TWA) 2,670 2,636 2,493

DIY – Scenario 2, leak from charge kit while charging system (30-minute TWA) 38,900 37,800 32,800



### A series of graphs, indicating the predicted air concentrations over time which are associated with each repair scenario are included as Attachment C.



## 4.5 Risk Characterization

4.5.1 Health Hazard Indices for HFO-1234yf fo r Passenger Compartment and Repair Worker

Scenarios

Results of the air modeling and risk characterization (Table 24) indicate that none of the modeled HFO-1234yf releases would result in an unacceptable leve l of health risk (HI<1.0). Note that the measurement from the field test of the large leak results in a substantially lower HI than the CFD modeling. Also note that the collision scenario was not modeled for HFO-1234yf, and it seems unlikely

that air concentrations in this scenario would exceed the health-based limits given the large margin of safety present with the large leak, particularly as rela tes to the field measurements. However, lacking specific data to support this conclusion, the co llision scenario will be evaluated in the FTA.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 62 Gradient CORPORATION Table 24. Hazard Indices Associated with Passenger Exposure Scenarios, HFO-1234yf

Scenario Predicted HFO1234yf Concentration (ppm) Health Based Comparison Value (ppm) Hazard Index (HI) Results of CFD Modeling Large leak, recirc mode (CFD Sim 1) 63,000 120,000 (mRCLcs) 0.53 Medium leak, recirc mode (CFD Sim 2) NA 115,000 (mRCLat) NA Small leak, recirc mode (CFD Sim 3) NA 115,000 (mRCLat) NA Large leak, outside air (CFD Sim 4) 32,000 120,000 (mRCLcs) 0.27 Medium leak, outside air (CFD Sim 5) NA 115,000 (mRCLat) NA Small leak, outside air (CFD Sim 6) NA 115,000 (mRCLat) NA

Results of Field Measurement Large leak, recirc mode <29,000* 120,000 (mRCLcs) <0.24 Collision Scenario – imputed from CFD res ults for large leak (recirc condition) Collision >63,000 120,000 (mRCLcs) Possibly >1 NA – value must be less than value for the rele vant large leak and therefore well below 1.0. MRCLcs = health criterion based on cardiac sensitization. MRCLat = health criterion based on acute toxicity. * The maximum measured value, the 5-mi nute TWA would be less than this value.



### The risk characterization indicates that HFO-1234yf re leases associated with all of the vehicle repair scenarios (Table 25) are associated w ith HI values < 1.0, indicating exposures that are below levels of concern. The highest HI value, associ ated with the charge kit leak, w as 0.29. This particular scenario results in a substantially higher HI value because th e air volume under consideration is extremely small ( i.e. , 0.5 m 3 

### ). The air volumes associated with the other re pair worker scenarios are substantially greater and allow for greater dispersion of the leaked material into the room.

Table 25. Hazard Indices Associated with Vehicle Repair Scenarios, HFO-1234yf Scenario Predicted HFO1234yf Concentration (ppm) Health Based Comparison Value (ppm) Hazard Index (HI)

Professional repair – complete charge loss 566 120,000 (mRCLcs) 0.005

Professional repair – hose leak during system drain and recharge 122 115,000 (mRCLat) 0.001

DIY – Scenario 1 (slow loss of heel from 2 cans) 2,493 115,000 (mRCLat) 0.022

DIY – Scenario 2 (leak while charging) 32,800 115,000 (mRCLat) 0.29G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 63 Gradient CORPORATION 

### 4.5.2 Ignition Risks for HFO-1234yf for Passenger Compartment, Engine Compartment and Repair Worker Scenarios

Results from the CFD modeling and vehicle testing pertaining to the potential ignition hazard of HFO-1234yf in the passenger compartment are shown in Table 26 below. With respect to ignition from a potential smoking-related ignition source, the CFD modeling indicated that maximum HFO-1234yf concentrations in the passenger compartment r esulting from the small and medium leaks (both recirculation and outside air) as well as the large leak (outside air only) did not approach the LFL. These situations therefore do not present a potential smoki ng related ignition hazard. The CFD modeling did indicate that passenger compartment concentrations ma y exceed the LFL in the case of the large leak with the vehicle operating in recirculation mode. This suggests a potential ignition hazard if a smoking-related ignition source is present, as indicated in Table 26. No te however, that field test results indicated that HFO-1234yf concentrations in the passenger compartm ent do not reach the LFL, indicating a lack of ignition hazard. Because the Exponent field test results are derived from a more realistic situation than the results of the DuPont CFD modeling, the overall conclusion should be that a large leak (0.5 mm) while the vehicle is operating in recirculation mode will not result in a potential ignition hazard. This conclusion is also supported by the CFD modeling work conducted by Honeyw ell and Fluent with a smaller vehicle. In the Honeywell/Fluent simu lations (conducted for the full leak duration of 600 seconds), the peak concentration associated with the large 0.5 mm leak was well below the LFL (53,000 ppm versus 65,000 ppm) (Honeywell, 2008). In add ition, actual concentration measurements made during and after a simulated 0.5 mm leak in a mock-up vehicle also confirmed that the passenger compartment concentration of HFO-1234yf remained below the LFL (Honeywell, 2008).

With respect to ignition from a short from an in ternal battery, the DuPont CFD modeling results show that in the event of a large leak, concentra tions of HFO-1234yf at the floor of the passenger cabin do not exceed the LFL. This is confirmed by the results of the Exponent vehicle testing (Table 26). Aswith the smoking-related ignition source scenario, the Exponent vehicle test measurements of HFO1234yf concentrations were substa ntially lower than concentrations estimated by CFD modeling.

CFD modeling was not conducted to evaluate the risks of a short from a PTC heater located in the AC duct system. Vehicle testing for this scenario indicated that HFO-1234yf concentrations would not exceed the LFL (Table 26). Thus, this scenar io also does not present an ignition risk.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 64 Gradient CORPORATION 

### Neither the DuPont CFD modeling nor the Exponent field measurements addressed the vehicle collision scenario. Results from the DuPont CFD modeling of the large leak suggest that, in the event of a collision and complete rupture of the evaporator tubing, the HFO-1234yf concentration in the passenger compartment would likely exceed the LFL. It is not cl ear how the results of vehicle testing can contribute to this speculation. Lacking specific data to address the collision scenario, we will assume the LFL is

exceeded and will include this scenario in the FTA. 9

Table 26. Ignition Risk Associated with Passenger Compartment Scenarios, HFO-1234yf Scenario Maximum Concentration (ppm) LFL (ppm) Ratio: Concentration to LFL Conclusion

Passenger Compartment Smoking Scenario (CFD Modeling) Large leak, recirc mode (Sim 1) 65,000 65,000 1.0 Possible ignition risk* Medium leak, recirc mode (Sim 2) <65,000 † 65,000 <1.0 No ignition risk Small leak, recirc mode (Sim 3) <65,000 † 65,000 <1.0 No ignition risk Large leak, outside air (Sim 4) 34,000 65,000 0.52 No ignition risk Medium leak, outside air (Sim 5) <34,000 † 65,000 <0.52 No ignition risk Small leak, outside air (Sim 6) <34,000 † 65,000 <0.52 No ignition risk Passenger Compartment Internal Ba tter Scenario (CFD Modeling) Concentration on vehicle floor 56,500 65,000 0.87 No ignition risk Passenger Compartment Scenarios (Vehicle Test) Driver’s Breathing area 29,000 65,000 0.45 No ignition risk Driver’s side floor 27,500 65,000 0.42 No ignition risk Duct Location 29,500 65,000 0.45 No ignition risk 

### Passenger Compartment Collision Scenario (Data imputed from CFD results for large leak during recirculation mode) Collision >65,000 65,000 >1 Potential ignition risk * Possible ignition risk from CFD modeling is countered by results of vehicle test. † The maximum concentration was not determined because the l eak duration is greater than the time frame addressed by

CFD modeling. However, the leak rate in the small and medium leaks is lower than that in the large leak case and thus more affected by cabin leakage to the exterior air. Thus, the maximum concentration in the event of small and medium leaks must be less than that observed with the corresponding large leaks.



### Results from the CFD modeling and vehicle testing pertaining to the potential ignition hazard of HFO-1234yf in the engine compartment are shown in Ta ble 27 below. The results of the vehicle test

indicate that while the LFL was exceeded in one locati on (near the exhaust manifold), the investigators were unable to ignite the material. Thus, the conclu sion for this scenario is that a very large leak such as that simulated would not result in a potential engine compartment ignition hazard.

9 Note that CFD modeling and mock-up m easurements by Honeywell for the smaller size vehicle (Honeywell, 2008) indicate that a very large leak such as might occur in a collision could produce concentrations above the LF L. However, Honeywell also found that it was not possible to ignite the HFO-1234yf in such cas es using either a butane lighter or an electrical arc welder

. Thus, the decision of the CRP1234 team to retain the collision scenario in the fault tree analysis is conservative.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 65 Gradient CORPORATION Table 27. Ignition Risk Associated with Passenger Compartment Scenarios, HFO-1234yf Scenario Maximum Concentration (ppm) LFL (ppm) Ratio: Concentration to LFL Conclusion

Engine Compartment AR Ignition Scenario (Vehicle Test) Engine compartment 87,000 65,000 1. 3 Failed to ignite, no ignition risk



### Results from the CFD modeling and vehicle testing pertaining to the potential ignition hazard of HFO-1234yf in vehicle repair areas are shown in Ta ble 28 below. None of the modeled HFO-1234yf concentrations in the repair areas approached the LFL. In most instances, the concentrations were extremely low. Only in the char ge kit leak scenario was the modele d peak air concentration a sizeable fraction of the LFL ( i.e ., 60%). Recall that this scenario c onservatively assumed the refrigerant was released and remains over the course of release (10 minutes) in a 0.5 m 3 

### volume around the engine

compartment.

Table 28. Ignition Risk Associated with Repair Scenarios, HFO-1234yf Scenario Maximum Concentration (ppm) LFL (ppm) Ratio: Concentration to LFL Conclusion

Repair Scenarios (Modeling) Professional repair – complete charge loss 590 65,000 0.009 No ignition risk

Professional repair – hose leak during system drain and recharge 146 65,000 0.002 No ignition risk

DIY – Scenario 1 (slow loss of heel from 2 cans) 2,670 65,000 0.04 No ignition risk

DIY – Scenario 2 (leak while charging) 38,900 65,000 0.60 No ignition risk



### 4.5.3 Ecological Risks

Honeywell has completed a set of ecological aquatic toxicity tests for HFO-1234yf. All test results appear to be at levels which would preclude a designation of "very toxic", "toxic" or "harmful" to aquatic organisms under the EU Dir ective. Although results for the Daphnia and algal tests, expressed as "greater than" values, are not clearly above the threshold of 100 mg/L (for designation as "harmful to aquatic organisms") the testing laboratory laboratory' s opinion, in which we concur, is that because no

effects at all were observed at the maximum tested concentrations, the EC50s must be above the 100 mg/L criterion. A comparison of toxicity values is provided in Table 29.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 66 Gradient CORPORATION Table 29. Ecological Toxicity Data for Selected Chemicals Compared to HFO-1234yf Chemical Usage EC50 algal growth inhibition in 96-

hr test (mg/L) EC50 Daphnia in 48-hr test

(mg/L) LC50 fish in 96-hr test (mg/L) Source

1234yf Potential AR >75 >83 >197 (carp) Honeywell Comparison Chemicals Benzene Gasoline component > 1,360 356-390 5.3 (salmon) ESIS

Toluene Gasoline component >433 11.5L 26 (minnow) 24 (trout) ESIS

Xylenes Gasoline component 10* no data 26.7 (minnow) >780 (carp) ESIS

Pentane Gasoline component no data 9.74 no data ESIS

Gasoline Fuel 4,700 (72-hr test) no data no data ESIS Ethylene glycol Antifreeze component 6,500-7,500 >10,000 17,800 (trout) ESIS

Triethylene glycol monobutyl ether Brake fluid component >500** 1740 -2,802 2,400 (minnow) ESIS

Chlorine Disinfectant gas no data 0.017-0.085 0.08 (minnow) 0.014 (trout) ESIS

Chloroform Water disinfection by-product 950** 66-90 18 (trout) 71 (minnow) ESIS

Malathion Pesticide 4.06 (72-hr test) 0.0009 0.04 (minnow) ESIS 2,4-D Herbicide 33.2 417 (72 hr test) 128-217 (silverside) ESIS

R-134a Current automotive refrigerant no data 980 450 (trout) DuPont

ESIS – European Chemical Substances Information System, http://ecb.jrc.it/esis Unless otherwise noted, algal tests were conducted with Selenastrum capricornutum . Where more than one test result was available in the ESIS database, the most representative number was chosen. * Test conducted with Cricosphaera carterae ** Test conducted with Scenedesmus subspicatus



### 4.5.4 Potential Risks to Other Receptors

As indicated in Section 2.5.3, risks for au tomotive assembly workers ar e anticipated to be insignificant. Data from GM indicate that R-134a le vels measured in assembly plants were consistently below 10 ppm ( i.e. , 100 times less than the Occupational Exposure Limit of 1,000 ppm). Although there is some uncertainty in extrapolating results for R- 134a to HFO-1234yf, it would be reasonable to expect that HFO-1234yf levels would be generally similar to levels of R-134a. The no effect level for HFO1234yf, based on the 90-day animal studies of the components is 38,500 ppm. This concentration isG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 67 Gradient CORPORATION 

### almost 4,000 times higher than the R-134a concentr ation measured in the GM assembly plants, which provides a sufficient margin of safety for assembly workers.

4.5.5 Degradation Products

Although fluorocarbons such as the components of refrigerants are generally perceived to be chemically stable, under extreme conditions, such as a fire, they may decompose. For example, the decomposition temperature of R-134a is reported to be greater than 340oC (>700oF), a temperature which may be reached in a vehicle fire but not under normal operating conditions. The products of the decomposition of hydrofluorocarbons include hydrogen fluoride (HF), carbon dioxide (CO 2 

### ), carbon monoxide (CO), and carbonyl fluoride (COF 2 

### ). The toxicity of HF and COF 2 

### is of an irritant or caustic nature as these gases are highly reactive and water solubl e. The respiratory tract and mucous membranes will be the primary organ systems affected. The irritancy properties of HF is a means to warn occupants

to evacuate the area if HF is formed or released at de tection levels similar to its exposure limits. The air odor threshold for hydrogen fluoride is 0.04 ppm (OSHA, 2008) and if leve ls substantially above the odor threshold are present, the car occupant would likely seek outside air circulation or open windows, providing mitigation measures. Acute exposure limits for HF and COF 2 

### are summarized in Table 30.

Table 30. Acute Exposure Limits for Fl uorocarbon Decomposition Products Chemical Exposure Limit (ppm) Basis

Hydrogen Fluoride (HF) 1 AEGL1 – a level without adverse effect. Value for 10 minutes to 8 hours of exposure. U.S. EPA acute exposure guideline. Carbonyl Fluoride (COF 2 ) 5 TEEL1 – a level expected to produ ce only mild or tr ansient health effects. NOAA guideline



### Decomposition of HFO-1234yf in a fire scenario mi ght, in theory, pose a significant acute health risk to passengers or firemen. But in the event of a fire, other toxic chemicals will be produced by combustion of other automotive components and thus decomposition of the refrigerant may increase the risk for fire fighters and would not introduce an entirely new type of hazard. It is also anticipated that only a small portion of the refrigerant charge will be converted to these decomposition products. In U.S.

EPA's assessment of risk of R-152a and CO 2 

### (R-744), the agency cited a study by Southwestern

Laboratories which indicated that a 100% R-134a atmo sphere only produced an HF concentration of 10 ppm when passed through a tube heated to 1,000 oF (Blackwell et al ., 2006). A search of the medical literature also did not reveal any published reports of injuries to fire fighters or vehicle passengers resulting from exposures to COF 2 

### or HF produced in fires involving refrigerants.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 68 Gradient CORPORATION 

### With respect to risk of HF, use of HFO-1234yf would not be expected to create a significantly greater risk than that which exists with refrigera nts such as R-12 or R-134a. HFO-1234yf contains four moles of fluorine per mole of chemical, the same value as R-134a. However, when one accounts for the molecular weights of R-134a (102 grams per mole) and HFO-1234yf (114 grams per mole), the amountof HF that could be produced by complete decomposition of 1 kilogram of material is less for HFO1234yf (702 grams per kilogram) relative to R-134a (784 grams per kilogram). 10 

### As noted above, the Southwestern Laboratories study of R-134 decomposition suggests the actual amount of HF produced by decomposition of HFO-1234yf in a fire would be subs tantially less than this theoretical estimate.



## 4.6 FTA

4.6.1 Toxicity FTAs

Fault trees related to the toxicity of HFO-1234yf are shown in Figures 8 through 13. As indicated in these figures, for the small, medium and large l eak situations, concentrations of HFO-1234yf in the passenger compartment are not predicted to exceed h ealth-based limits. The FTA risks associated with

these fault tree branches are therefore zero. With r espect to the vehicle collision scenario, air modeling data are not available to evaluate the potential risks with certainty. However, the HI for the large leak (0.5 mm) scenario (recirculation mode) was <0.56 a nd the earlier R-12 scenario suggests that with the larger leak size contemplated by the collision scenario ( i.e. , 1.45 or 2.3 mm), HFO-1234yf concentrations in the passenger cabin could possibly exceed health-based limits. The risk s associated with this fault tree

branch were therefore retained in the FTA. HI va lues for vehicle repair scenarios never exceeded 1.0 and therefore the contribution of the repair fault tree to ove rall risk is zero. The final estimated risks from the FTA are 0.02 per year, in both the U.S. and Europe. These risks are entirely due to the collision scenario.

Note that this risk level is several orders of ma gnitude less than the equivalent risks estimated for R-12 (11 exposures of concern per year).

4.6.2 Flammability FTAs

Fault trees related to the potential flammab ility of HFO-1234yf are shown in Figures 14 through 21. As indicated in these figures, the probability of reaching the LFL and having a potential ignition

10 A similar analysis can be conducted for R- 12, which consists of two moles of fluorin e and two moles of chlorine per mole of R-12. Complete decomposition of R-12 would produ ce 332 grams of HF and also 606 grams of HCl.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 69 Gradient CORPORATION 

### situation is zero for small and medium HFO-1234yf leaks into the vehicle compartment and all leaks involving worker repair areas. As noted above, neither large leak scenario involving the passenger compartment ( i.e ., vehicle in recirculation or outside air mode) is expected to result in a potential ignition hazard based on the results of the field testing. W ith respect to the engine compartment, while field measurements did indicate the LFL was exceeded in one test/measurement location, it did not prove possible to ignite the material after an engine compar tment release. This also suggests that the possibility of ignition in the engine compartment is negligible . Thus, as shown in the fault trees, the only scenario which contributes to a potential ignition risk is the vehicle collision scenario. Including this scenario in the analysis results in a very small risk of ign ition, 0.004 per year, which translates into once per 250

years.

4.6.3 Comparative Risks

The risk of exposure to HFO-1234yf above human health-based criteria is estimated in the FTA to be 0.02 per year and the risk of HFO-1234yf ignition is estimated to be 0.004 per year. Both values are solely attributable to the collision scenario, the only scenario for which neither modeling nor field

measurement has been conducted. Because the values represent different types of outcome, they should not be added but considered individually. An even t frequency of 0.02 per year is equivalent to one occurrence every 50 years whereas an event frequency of 0.004 per year is equivalent to one occurrence every 250 years. These event frequencies compare very favorably to the risks estimated for R-12, which were 11 exposures above the human health-based criterion per year.

To place these estimated risks in better perspective, they can be compared to annual risks of other adverse outcomes. If the risk estimates for HFO-1234yf derived from the FTA are divided by the number of drivers currently registered in the U.S. (200 milli on) the annual risk per driver of an exposure above

the mRCL would be 1 x 10

- 10 

### and the risk of an HFO-1234yf release leading to an ignition event and an injury would be 2 x 10 -11 

### . Similar values can be derived based on European statistics. As shown in Table 31, these risks are far below those associated with other commonly encountered and accepted risks

and are in fact smaller than risks of even ts that are considered extremely unlikely.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 70 Gradient CORPORATION Table 31. Risks of Injury or Fatality from Various Events Compared to Risks Associated with Leaks of HFO-1234yf Risk Risk per individual per year Citation

Risk of stroke 2.7 x 10 -3 Rhys Williams, 2001 Fatal accident in the home 1.1x 10 -4 Wilson and Crouch, 1987 Serious injury while using a chainsaw# 2.2 x 10 -4 CDC, 2004 # Fatal accident while climbing m ountains (if mount aineer) 6 x 10 -4 Wilson and Crouch, 1987 Risk of being injured as a pedestrian 2.1 x 10 -5 NSC, 2004 Fatal injury at work (all occupations) 3.6 x 10 -5 NSC, 2004 Injury during use of fireworks 3.6 x 10 -5 Hall, 2007 § Risk of catastrophic asteroid impact with the earth 1 x 10 -6 Chapman and Morrison, 1994* Injury from lightni ng strike 1 x 10 -6 NWS, undated** Risk of dying during a 5000-mile plane trip 3x10 -6 Wilson and Crouch, 1987 Fatal electrocution 5.3 x 10 -6 Wilson and Crouch, 1987 Risk of being fatally injured in an elevator ride 2x10 -7 McCann and Zalesky, 2006 Risk of being struck by airplane while on the ground 6 x 10 -8 Goldstein et al ., 1992 Risk of exposure to HFO-1234yf above health based limits resulting from a collision 1 x 10 -10 Current analysis &

Risk of being injured by an HFO-1234yf ignition resulting from a collision 2 x 10 -11 Current analysis &

*Risk cited is 1 in 10,000 over the next century # Injury sufficiently serious to require hospital visit. Based on number of injuries per year divided by U.S. adult population

. § Total number of injuries requiring hospital visit per year divided by the total U.S. population. ** Total number of documented injuries from lightning st rikes per year, divided by total U.S. population. & Number of FTA predicted events divided by the number of estimated drivers in the U.S.



## 4.7 Conclusions Regarding HFO-1234yf

The DuPont/Honeywell AR, HFO-1234yf, offers equi valent or lower toxicity compared to R134a or R-12 in terms of both human health effects and ecological effects. The material also has an ODP of 0 and a GWP of 4 which meets the European Union F-gas requirements. HFO-1234yf is flammable, although testing conducted by DuPont and Honeywell indicates the ignition potential of this chemical is far less than that of other flammable refrigerants ( e.g., R-152a). Nonetheless, due to the flammability of HFO-1234yf, the risk assessment addressed both health e ffects and potential ignition. Based on a review of toxicity data developed by the manufacturers as we ll as the results of air modeling to predict exposure concentrations, potential exposures of vehicle passengers and repair workers are expected to be below

levels associated with health risk . In the event of a vehicle collision and refrigerant release, air concentrations could potentially exceed health-based limits. However, the frequency of collision related releases is quite small and results in a very low overall estimate of health risk. Evaporator failures are not found to occur in the case of frontal impact based on OEM experience. In the case of side impact, theG:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 71 Gradient CORPORATION 

### probability of evaporator rupture is very small and if they do fail, the passenger compartment will damaged such that it will no longer be sealed as a resu lt of the same side impact. Consideration of the large leak data suggests that an HFO-1234yf release asso ciated with a severe vehicle collision could result in passenger compartment concentrations that could pose an ignition hazard. However, the frequency of this event is expected to be extremely small, amoun ting to 0.009 events per year across the entire vehicle fleet in either the U.S. or Europe (equivalent to 1 such event every 111 years).

Across the entire vehicle fleet in Europe or the U.S., use of HFO-1234yf could result in 0.02 exposures per year above health-based limits as eval uated for the USA and European vehicle fleet, a value protective of human health for acute exposures. This frequency is equiva lent to 1 such exposure every 50 years. This level of risk is several orders of magnitude less than the comparable risks estimated

for R-12. The estimated level of health risk asso ciated with use of HFO-1234yf as an AR is also substantially less than the level of risk tolerated by the general public as part of every day life and less than the risk inherent in many commonly accepted activities ( e.g. , airplane travel, riding in elevators).

Potential ignition hazards of HFO-1234yf were evaluated through laboratory testing, CFD modeling, and vehicle testing. Together, these ev aluations suggested an absence of potential ignition hazards in the event of small, medium or large leak s into the passenger cabin or repair worker areas. CRP1234 also evaluated potential ignition risks from leaks of HFO-1234yf in the engine compartment via vehicle testing. The issues of collision that are di scussed above also apply to the additional risks of flammability following a collision. The results of this study indicated that concentrations of HFO-1234yf could be detected in the flammable range in highly conservative vehicle conditions. However, an attempt to ignite HFO-1234yf after a release in the engine compartment was unsuccessful. Additional testing by CRP1234 to support this finding is now underway.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

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## 5 References

American Conference of Industria l Hygienists (ACGIH). 2001. 7 th Edition Documentation of the Threshold Limit Values for Chemical Substances. ACGIH Worldwide. Cincinnati, OH. American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). 2007. ANSI/ASHRAE Standard 34-2007, Designation and Safe ty Classification of Refrigerants. American Society of Heating, Refrigerating, and Air-Conditioni ng Engineers. Atlanta, GA. Anticoli, M. General Motors Corpora tion. 2007. Personal communication rega rding testing results for R-134a in General Motors Corporation assembly plants. August 11. Arthur D. Little Company. 1982. Ignition sources of LNG [ liquefied natural gas] vapor clouds. Project for the Gas Research Institute (GRI-80/0108), January. Azar A, Reinhardt CF, Maxfield ME, Smith PE Jr, Mullin LS.1972. Experimental human exposures to fluorocarbon 12 (dichlorodifluoromethane). AIHA Jour nal. April Batterman S, Jia C, Hatzivasilis G. 2007. Migration of volatile organic compounds from attached garages to residences: a major exposure source. Environ Res . 104(2):224-40. Beck, PS; Clark, DG; Tinston, DJ. 1973. The pharm acologic actions of bromoc hlorodifluoromethane (BCF). Toxicol. Appl. Pharmacol. 24 (1) :20-29. Berends, AG; de Rooij, CG; Shin-ya, S; Thompson, RS. 1999. Biodegradation a nd ecotoxicity of HFCs and HCFCs. Arch Environ Contam Toxicol . 36(2):146-51 Blackwell, N; Bendixen, L; Birgfeld, E. 2006. Risk Anal ysis for Alternative Refrigerant in Motor Vehicle Air Conditioning. September. Brock WJ, Shin-Ya S, Rusch GM, Hardy CJ, Trochimowi cz HJ. 1999. Inhalation toxicity and genotoxicity of hydrochlorofluorocarbon (HCFC)-225ca and HCFC -225cb. J Appl Toxicol. 19(2):101-12. Brock, WJ; Rusch, GM; Trochimowicz, HJ. 2003. Cardiac sensitization: methodology and interpretation in risk assessment. Reg. Tox. Pharmacol . 38:78-90. Carley, L. 2004. Automatic Climate Control. Counterman . March 01, 2004. Available at: www.aftermarketnews.com/default.aspx?type=w m&module=4&id=3&state=DisplayFullText&item=5368 Centers for Disease Control (CDC). 2004. Preventing Ch ain Saw Injuries During Tree Removal After a Disaster. Available at: http://www.bt.cdc .gov/disasters/chainsaws.asp Centers for Disease Control (CDC). 2004. Ciga rette smoking among adults – United States, 2004. MMWR Weekly

. 54(44):1121-1124. Available at: http://www.cd c.gov/MMWR/preview/mmw rhtml/mm5444a2.htm Chapman, C.R. and Morrison, D., 1994. Impacts on the Earth by asteroids and comets: assessing the hazard, Nature , v. 367, p. 33-40. Chengelis, C.P., (1993). Acute cardiac sensitization study in dogs with FM-200 by inhalation. WIL Research Laboratories, unpublished data. Cited in Brock et al ., 2003. Chengelis, C.P. 1997. Epinephrine sensitivity of the canine h eart: A useful test. In R. Snyder, K.S. Bakshi, and B. M. Wagner, Abstracts of the Workshop on Toxic ity of Alternatives to 34 Chlorofluorocarbons. Inhalat. Toxicol

. 9:775-810. Dekant, W. 1996. Toxicology of chlorofluorocarbon replacements. Env. Health Perspect. 104(Suppl. 1): 75-83. DuPont. 2008. CFD modeling of a large car. DRAFT. January 25. DuPont/Honeywell. 1234yf: A Low GW P Refrigerant For MAC. [Meeti ng Presentation]. September 28, 2007 European Fluorocarbon Technical Committee. 2007. F-Gas Regulation. Obtained online at: http://www.fluorocarbons.org/en/debate/regulat ory_developments/f_gas_regulation.html.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 73 Gradient CORPORATION Exponent Inc. 2008. HFO-1234yf Refrigerant Concentrations and I gnition Tests in Full-Scale Vehicle Passenger Cabin and Engine Compartment. February Goldstein BD, Demak M, Northridge M, Wartenberg D. 1992. Risk to gr oundlings of death due to airplane accidents: a risk communication tool. Risk Anal. 12(3):339-41. Gradient Corporation. 2008. Risk Assessment For Alte rnative Refrigerants. Prepared for the Society of Automotive Engineers (SAE) Cooperative Research Project 150. Confidential. February. Hall, JR. 2007. Fireworks. Fire Analys is and Research Division, National Fire Protection Association, Quincy MA. Available at: http://www.nfpa.org/a ssets/files/pdf/os.fireworks.pdf Hamner Institutes for Health Sciences. 2006. Toxicoge nomic assessment of the carcinogenic potential of 2,3,3,3- tetrafluoropropene. Final Report. MA-RR-07-3454 Hardy CJ, Kieran PC, and Sharman IJ. 1994. Assessment of the cardiac sensitization potential (CSP) of a range of halogenated alkanes. Toxicologist. 14:378 Honeywell International. 2008. Evaluation of Leak Rate s, CFD Modeling of a Typical European Size Vehicle, and Flammability Testing in a Passenger Compartment Mock-up and on Hot Surfaces. February. Huntingdon Life Sciences. 2004. Final Report. Study No . 03-5471. Trans HFO-1234: An Acute (4-hour) Inhalation Range finding study in the mouse via whole-body exposure. Huntingdon Life Sciences. 2004. Trans HFO-1234: an acute (4-hour) inhalation toxicity screening study with a micronucleus assay in the mouse and rat via nose-only exposure. MA-RR-04-2768. ICF Consulting. FaultrEASE TM software. www.icfi.com. Intergovernmental Panel on Climate Change (IPCC). 2005. Special Report on Safeguarding the Ozone Layer and the Global Climate System: Issues Related to Hydrof luorocarbons and Perfluorocarbons. Special Report of the Intergovernmental Panel on Climate Change. Bert Metz, La mbert Kuijpers, Susan Solomon, Stephen O. Andersen, Ogunlade Davidson, José Pons, David de Jager, Tahl Kestin, Martin Manni ng, and Leo Meyer (Eds.). Cambridge University Press, UK. pp 478. Obtained online at: http://arch.rivm.nl/env/int/ipcc/docs/full-reports/SROCFullVolumev2.pdf International Standards Organization (ISO). 2007. Refrigerants – Designation a nd safety classification. Committee Draft. International Organization fo r Standardization. ISO/CD 817:2007.

International Uniform Chemical Inform ation Database (IUCLID). 2007. Data base file for hexafluoropropene. Jetter JJ, Forte R Jr, Rubenstein R. 2001. Fault tree analys is for exposure to refrigerants used for automotive air conditioning in the United States. Risk Anal. 21(1):157-70 Kozakiewicz, A. 2007. Update on Legal Situation on Gr eenhouse Gas Emissions of MACs. European Commission presentation at VDA Alternative Refrigerant Wi nter Meeting. Saalfelden. February 14. Krahn DF, Barsky FC, McCooey KT. 1980. CHO/HGPRT Mutation Assay: Evaluati on of Gases and Volatile Liquids. Pp. 91-103 in Genotoxic Effects of Airborne Agents , R.R. Tice, D.L. Costa, and K.M. Schaich, eds. New York: Plenum Press. Leuschner F, Neumann W, Hübscher F. 1983. Report on subacute toxicological studies with several fluorocarbons in rats and dogs by inhalation. Arzneimittelforschung . 33(10):1475-6 Longstaff E, Robinson M, Bradbrook C, Styles JA, Pu rchase IF. 1984. Genotoxicity and carcinogenicity of fluorocarbons: assessment by short-term in vitro tests and chronic exposure in rats. Toxicol Appl Pharmacol

. 72(1):15-31. Longstaff E.1988. Carcinogenic and mutage nic potential of several fluorocarbons. Ann N Y Acad Sci. 1988;534:283- 98. Malley LA, Frame SR, Elliott GS, Bentley KS, Brock WJ , Trochimowicz HJ, Rusch GM. 1998. Chronic toxicity, oncogenicity, and mutagenicity studies w ith chlorotetrafluoroethane (HCFC-124). Drug Chem Toxicol . 21(4):417- 47. Maltoni C, Lefemine G, Tovoli D, Perino G. 1988. Long-term car cinogenicity bioassays on three chlorofluorocarbons (trichlorofluoromethane, FC11; dichlo rodifluoromethane, FC12; chlorodifluoromethane, FC22) administered by inhalation to Spra gue-Dawley rats and Swiss mice. Ann N Y Acad Sci. 534:261-82.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 74 Gradient CORPORATION Millischer RJ, de Rooij CG, Rush GM, Farr CH, Ben-Dyke R, Hardy CJ , Lewis DJ, Hodson-Walker G. 1995. Evaluation of the genotoxicity potential and chronic inha lation toxicity of 1,1-dichloro-1-fluoroethane (HCFC141b). Food Chem Toxicol . 33(6):491-500. Mobile Air Conditioning Society (MACS). 2003. Presentations at Worldwide convention. Jan. 30 to Feb. 1. New Orleans, LA. McCann, M., Zalesky, N. 2006. Deaths and Injuries Invol ving Elevators and Escalators. The Center to Protect Workers’ Rights, Silver Spring, MD. http://www.cpwr .com/pdfs/pubs/research_pubs/e levatorconstructors2006.pdf Mullin, LS; Azar, A; Reinhardt, CF; Smith, PE; Fabryka, EF. 1972. Halogenated hydrocarbon-induced cardiac arrhythmias associated with re lease of endogenous epinephrine. Am. Ind. Hyg. Assoc. J. 33 (6) :389-396. National Institute for Occupational Safety and Health (NIO SH) [U.S.A.] 2002. International Chemical Safety Cards. Dichlorodifluoromethane. ICSC: 0048. h ttp://www.cdc.gov/niosh /ipcsneng/neng0048.html National Research Council (NRC). 1984 . Emergency and continuous exposure limits for selected airborne contaminants. Vol. 2 . National Academy Press. Washington, DC. National Research Council (NRC) [U.S.A .]. 1996. Toxicity of Alternatives to Chlorofluorocarbons: HFC-134a and HCFC-123. Commission on Life Sciences (CLS). Th e National Academies Pre ss. Washington, D.C. National Research Council (NRC) [U.S .A.]. 2000. Spacecraft Maximum Allowabl e Concentrations for Selected Airborne Contaminants: Volume 4. Commission on Life Sciences (CLS). Obtained online at: http://books.nap.edu/openbook.php?record_id=9786&page=R1 National Safety Council (NSC) [U.S.A]. 2004. Website. www.nsc.org. A ccessed on December 23, 2007. National Weather Service [U.S.A.] unda ted. Thunderstorms, Tornadoes, Light ning, Natures most violent storms. www.nws.noaa.gov/os/brochures/ttl.pdf Nielsen, OJ; Javadi, MS; Sulbaek A ndersen, MP; Hurley, MD; Wallington, TJ; Singh, R. 2007. Atmospheric chemistry of CF3CF@CH2: Kinetics and mechanisms of gas-phase reactions w ith Cl atoms, OH radicals, and O3. Chemical Physics Letters 439: 18–22 Nuckolls, A.H. 1933. Underwriter's Laboratories' Report on the Com parative Life, Fire, and Explosion Hazards of Common Refrigerants. Miscellaneous Hazard No. 2375 . Underwriter's Laboratories. Chicago, IL. Occupational Safety and Health Admi nistration (OSHA). 2008. Occupationa l Safety and Health Guideline for Hydrogen Fluoride. http://www.osha. gov/SLTC/healthguidelines/hydrogenfl uoride/recognition.html. Accessed 2/8/2008. Perrin Quarles Associates. 2007. Disposable Container H eel Testing Study Report. Prepared for U.S. EPA, Stratospheric Protection Divisi on. March 21, 2007. 38 p. Prendergast JA, Jones RA, Jenkins LJ, Siegel J. 1967. Effects on experimental animals of long-term inhalation of trichloroethylene, carbon tetrachloride, 1,1,1-trichloroeth ane, dichlorodifluoromethane, and 1,1-dichloroethylene. Toxicol. Appl. Pharmacol. 10:270–289 Reinhardt, CF; Azar, A; Maxfield, ME; Smith, PE; Mullin , LS. 1971. Cardiac arrhythmias and aerosol sniffing. Arch. Environ. Health . 22:265-279. Rhys Williams, G. 2001. Incidence and Characteristics of Total Stroke in the United States. BMC Neurol. 2001; 1: 2.. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=32314

Ritchie et al . 2001. Acute neurobehavioral effects in ra ts from exposure to HFC 134a or CFC 12. NeuroToxicology

. 22:233-248. Scholz J. 1962. New toxicologic investiga tions of freons used as propellants fo r aerosols and sprays. Translation of: Fortschr. Biol. Aerosol-Forsch. Jahren 1957–1961, Ber. Aerosol-Kongr. 4:420–429 Silber, L.S., and G.L. Kennedy. 1979. Acute Inhalation Toxi city of Tetrafluoroethane. Rep. No. 422-79. Haskell Laboratory , Wilmington, Del. (as cited in NRC, 1996)

Stewart RD, Newton PE, Baretta ED, Herrm ann AA, Forster HV, Soto RJ. 1978. Physiological response to aerosol propellants. Environ Health Perspect . 26:275-85. TNO. 2005a. Sub-acute (2-week) inhalation toxicity study w ith HFO-1234yf in rats. Study code 6394. November 4.G:\Projects\206703\1234yf\Deliverable\Risk Assessment_final.doc 

### 75 Gradient CORPORATION TNO. 2005b. Chromosomal aberration test with HFO-1234y f in cultured human lymphocytes. Study code 6202/07. November 8.

TNO. 2005c. Bacterial reverse mutation test with HFO-1234yf. Study code 6205/09. November 15.

TNO. 2005d. .Micronucleus test in bone marrow cells of mice treated with HFO- 1234yf, administered by inhalation. Study code 6204/03. November 23. TNO. 2006a. Acute (4-hour) inhalation toxicity study w ith HFO-1234yf in rats. Study code 6201/06. January 17. TNO. 2006b. Preliminary experiment for development of a method for optimal ma intenance of test concentration in aqueous media as used in aquatic toxicity test s with HFO-1234yf. Study code 6472/01. May 5. TNO. 2006c. Acute toxicity study in Daphnia magna with HFO-1234yf. Study code 6472/03. May 8. TNO. 2006d. Freshwater algal growth inhibition te st with HFO-1234yf. Study code 6472/02. May 8. TNO. 2006e. 96-hour acute toxicity study in carp w ith HFO-1234yf (static). Study code 6472/04. June 15. TNO. 2006f. Sub-acute (4-week) inhalation toxicity study (including Unsche duled DNA Synthesis and Micronucleus test) with 2-week recovery period, with HFO-1234yf in rats. Study code 6872/02. September 5. TNO. 2007a. Prenatal developmental inha lation toxicity study with HFO-1234yf in rats. Study code 6986. April 17. TNO. 2007b. Sub-chronic (13-week) inhalation toxicity study with HFO-1234yf in rats. Study code 6872/01. May 11. Trochimowicz, HJ. 1993. Industrial re search on alternative fluorocarbons. Toxicology Letters . 68:25-30. Trochimowicz HJ, Azar A, Terrill JB, Mullin LS. 1974. Blood levels of fluorocarbon related to cardiac sensitization: II. Am Ind Hyg Assoc J . 35(10):632-9. Trochimowicz HJ, Reinhardt CF. 1975. Studies clar ify potential toxicity of aerosol propellants. DuPont Innovation 6(3):12-16 Trochimowicz, HJ; Reinhardt, CF; Mullin, LS; Azar, A; Ka rrh, BW. 1976. The effect of myocardial infarction on the cardiac sensitization potential of certain halocarbons. J. Occup. Med. 18(1): 26-30. Trochimowicz, HJ; Rusch, GM; Chiu, T; Wood, CK. 1988. Ch ronic inhalation toxicity/carcinogenicity study in rats exposed to Fluorocarbon 113 (FC-113). Fundam. Appl. Toxicol . 11:68-75. Tsai, WT. 2005. An overview of environmental hazards and exposure risk of hydrofluorocarbons (HFCs). Chemosphere . 61: 1539-47. United States Environmental Protection Ag ency (U.S. EPA). 1987. Integrated Risk Information System (IRIS) file: Dichlorodifluoromethane. www.epa.gov/ir is/subst/0040.htm. Accessed 1/10/08.

United States Environmental Protection Agency (U.S. EPA). 2002. A guide to selected algorithms, distributions, and databases used in exposure models developed by the office of air quality planning and standards. Office of Research and Development. Prepared by Ted Johnson, TRJ Environmental, Inc. EPA Grant No. CR827033. Obtained online at: http://www.epa.gov /ttn/fera/data/human/report052202.pdf. United States Environmental Protection Agency (U.S . EPA). 2007. Ozone Depletion. Obtained online at: www.epa.gov/ozone/strathome.html World Health Organization (WHO). 1978. Toxicologi cal evaluation of some food colours, thickening agents, and certain other substances

. Who Food Additives Series No. 8

. World Health Organization, Geneva WIL Research Laboratories, LLC. 2006. Acute cardiac se nsitization study of <redacted name> and HFO-1234yf in dogs. WIL study number-447008. Final Report. Wilson R, Crouch EA

. 1987. Risk assessment and comparisons: an introduction. Science . 236(4799):267-70.

### FIGURESFigure 1. Example Fault TreeSufficient oxygenpresent to supportcombustion0.90Concentration offlammable materialsufficient0.1Conditions favorable to afire0.09Hot surfacepresent0.02Open flamepresent0.001Ignition Source Present0.031Combustion Event0.0028&&ORLightedcigarettepresent0.01Figure 2. R-12 Fault Tree – SummaryExposure due to small leak0 /yrExposure due to leak causedby collision7.5 x 10-11/yrTotal number of passenger exposuresto refrigerant concentration exceedingexposure limits (per vehicle and year)4.5 x 10-8/yrExposure due to medium leak0 /yrExposure due to large leak4.5 x 10-8/yrNumber of vehicles in U.S.and Europe230 million (U.S.)241 million (Europe)Number of exposures torefrigerant concentrationexceeding exposure limit11 /yr (U.S.)11 /yr (Europe)Number of exposures of servicetechnicians/DIYers0 /yr (U.S.)0 /yr (Europe)OR&Number of vehicles inU.S. and Europe230 million (U.S.)241 million (Europe)Number of AC servicesper vehicle and year0.1Exposure above limitduring vehicle service(per serviced vehicle)0 /yr&ABCDEFigure 3. R-12 Fault Tree – Small Leak ScenarioExposure due to suddensmall leak3.26 x 10-9/hDoors and windowsclosed0.95Exposure to refrigerant concentrationexceeding exposure limit due tomedium leak0 /yrSize of leak is small(0.01 mm)0.05Sudden leak inpassenger compartment(400 ppm/yr / 8,760 h/yr)4.6 x 10-8/hLeakage is not detectedby passenger0.80&Number of occupantsper vehicle1.59Additional exposures dueto inadequate repair inservice (plus 50%)1.5Air control inoutside air mode0.68Refrigerant concentration in passengercompartment exceeds exposure limitfor small leakand outside air mode(Input from 3D-CFD-simulations)0(CFD Sim 2)&Probability of exceedingexposure limits inrecirculation mode0Probability of exceedingexposure limits inoutside air mode0Probability of exceedingexposure limits0ORAverage time of operationper car per year340 h/yrAAir control inrecirculation mode0.32Refrigerant concentration in passengercompartment exceeds exposure limitfor small leak recirculation mode0(CFD Sim 1)&&Note: Simulationnumbers refer to CFDmodeling conducted forCRP150 and not thecurrent CRP1234 riskassessment.Figure 4. R-12 Fault Tree – Medium Leak ScenarioExposure due to suddenmedium leak6.5 x 10-10/hDoors and windowsclosed0.95Exposure to refrigerant concentrationexceeding exposure limit due tomedium leak0 /yrSize of leak is medium(0.1 mm)0.01Sudden leak inpassenger compartment(400 ppm/yr / 8,760 h/yr)4.6 x 10-8/hLeakage is not detectedby passenger0.60&Number of occupantsper vehicle1.59Additional exposures dueto inadequate repair inservice (plus 50%)1.5Air control inoutside air mode0.68Refrigerant concentration in passengercompartment exceeds exposure limitfor medium leakand outside air mode(Input from 3D-CFD-simulations)0(CFD Sim 4)&Probability of exceedingexposure limits inrecirculation mode0Probability of exceedingexposure limits inoutside air mode0Probability of exceedingexposure limits0ORAverage time of operationper car per year340 h/yrB&Note: Simulationnumbers refer to CFDmodeling conducted forCRP150 and not thecurrent CRP1234 riskassessment.Air control inrecirculation mode0.32Refrigerant concentration in passengercompartment exceeds exposure limitfor medium leakrecirculation mode0(CFD Sim 3)&Figure 5. R-12 Fault Tree – Large Leak ScenarioExposure due to suddenlarge leak6.5 x 10-10/hDoors and windowsclosed0.95Exposure to refrigerant concentrationexceeding exposure limit due tolarge leak4.5 x 10-8/vehicleSize of leak is large(0.5 mm)0.01Sudden leak inpassenger compartment(400 ppm/yr / 8,760 h/yr)4.6 x 10-8/hLeakage is not detectedby passenger0.40&Number of occupantsper vehicle1.59Additional exposures dueto inadequate repair inservice (plus 50%)1.5Air control inoutside air mode0.68Refrigerant concentration in passengercompartment exceeds exposure limitfor large leakand outside air mode(Input from 3D-CFD-simulations)0 (Sim 6)&Probability of exceedingexposure limits inrecirculation mode0.32Probability of exceedingexposure limits inoutside air mode0Probability of exceedingexposure limits0.32ORAverage time of operationper car per year340 h/yrC&Note: Simulationnumbers refer to CFDmodeling conducted forCRP150 and not thecurrent CRP1234 riskassessment.Air control inrecirculation mode0.32Refrigerant concentration in passengercompartment exceeds exposure limitfor large leak recirculation mode1(CFD Sim 5)&Figure 6. R-12 Fault Tree – Collision ScenarioLeak in passengercompartment causedby collision5.2 x 10-6/yrExposure to refrigerantconcentrations exceedingexposure limit due to collision7.5 x 10-11/yrOccupant survivescollision0.9Probability collisiondeforms A-pillar >6“0.0187Frequency of seriouscollision5.6 x 10-3/yrProbability evaporatorpiping fails0.05Probability collision does notbreak windows and windowsnot already open0.0001Probability collision does notbreak any other componentin refrigerant cycle0.1Number of occupants pervehicle1.59&&DRefrigerant concentration in passengercompartment exceeds exposure limitin collision scenario1(likely based on Sim 5)Note: Simulationnumbers refer to CFDmodeling conducted forCRP150 and not thecurrent CRP1234 riskassessment.Figure 7. R-12 Fault Tree– Vehicle Repair ScenariosAir concentration isabove health-basedlimit0Leak duringservice0.006 /yrProbability ofinadequateventilation inshop0.001Work is carriedout by trainedtechnician0.97Leak from vehiclesystem duringservice0.005 /yrLeak from ACserviceequipmentduring service0.001 /yrTrained Technician hasexposure above limit0 /yrAir concentration isabove health-basedlimit0Leak during service0.006 /yrProbability ofinadequateventilation ingarage0.02Work is carriedout by DIYer0.03Leak fromvehicle systemduring service0.005 /yrLeak from ACcan duringservice0.001 /yrDIYer has exposureabove limit0 /yrExposure above limitduring vehicle service(per serviced vehicle)0 /yr&&&OROROREProfessionalshop airconcentrationexceeds limit0DIY garageairconcentrationexceeds limit0&Exposure events due to smallleak0 /yrExposure events due to leakcaused by collision7.5 x 10-11/yrTotal number of exposure eventsinvolving 1234yf (per vehicle andyear)7.5 x 10-11/yrExposure events due tomedium leak0 /yrExposure events due to largeleak0 /yrNumber of vehicles in U.S.and Europe230 million (U.S.)241 million (Europe)&Number of vehicles inU.S. and Europe230 million (u.S.)241 million (Europe)Number of exposureevents associated withvehicle repair –0 /serviced vehicle&abcdePotential exposure eventsrelated to 1234yf releaseassociated with vehicle repairin Europe and U.S.0 /yrORNumber of ACservices pervehicle andyear0.1Potential exposure eventsrelated to 1234yf releaseassociated with vehicle usein Europe and U.S.0.02 /yr (U.S.)0.02 /yr (Europe)Figure 8.Aggregate risk of potentially adverse exposure due toHFO-1234yf releaseExposure due to suddensmall leak6.16 x 10-8/hDoors and windowsclosed0.95Exposure to 1234yf concentrationexceeding exposure limit due tosmall leak0 /yrSize of leak issmall0.94Sudden leak inpassenger compartment(400 ppm/yr / 8,760 h/yr)4.6 x 10-8/hLeakage is not detectedby passenger0.8“a”Number of occupantsper vehicle1.59Air control inoutside air mode0.68 (U.S.)0.84 (Europe)1234yf concentration in passengercompartment exceeds exposure limitfor small leak and outside air mode0&&Probability of exceedingexposure limits inrecirculation mode0Probability of exceedingexposure limits inoutside air mode0Probability of exceedingexposure limits0Average time of operationper car per year340 h/yr&Air control inrecirculationmode0.32 (U.S.)0.16 (Europe)1234yf concentration in passengercompartment exceeds exposure limitfor small leak and recirculation mode0&ORFigure 9.Fault tree describing risk of potentially adverse exposure associatedwith a small HFO-1234yf leak into passenger compartmentAdditionalexposures due toinadequate repair inservice1.5Exposure due to suddenmedium leak3.3 x 10-9/hDoors and windowsclosed0.95Exposure to 1234yf concentrationexceeding exposure limit due tomedium leak0 /yrSize of leak ismedium0.05Sudden leak inpassenger compartment(400 ppm/yr / 8,760 h/yr)4.6 x 10-8/hLeakage is not detectedby passenger0.6“b”Number of occupantsper vehicle1.59Air control inoutside air mode0.68 (U.S.)0.84 (Europe)1234yf concentration in passengercompartment exceeds exposure limitfor medium leak and outside air mode0&&Probability of exceedingexposure limits inrecirculation mode0Probability of exceedingexposure limits inoutside air mode0Probability of exceedingexposure limits0Average time of operationper car per year340 h/yr&Air control inrecirculationmode0.32 (U.S.)0.16 (Europe)1234yf concentration in passengercompartment exceeds exposure limitfor medium leak and recirculation mode0&ORFigure 10.Fault tree describing risk ofpotentially adverse exposureassociated with a medium HFO-1234yf leak into passengercompartmentAdditionalexposures due toinadequate repair inservice1.5Exposure due to suddenlarge leak6.6 x 10-10/hDoors and windowsclosed0.95Exposure to 1234yf concentrationexceeding exposure limit due tolarge leak0 /yrSize of leak islarge0.01Sudden leak inpassenger compartment(400 ppm/yr / 8,760 h/yr)4.6 x 10-8/hLeakage is not detectedby passenger0.4“c”Number of occupantsper vehicle1.59Air control inoutside air mode0.68 (U.S.)0.84 (Europe)1234yf concentration in passengercompartment exceeds exposure limitfor large leak and outside air mode0&&Probability of exceedingexposure limits inrecirculation mode0Probability of exceedingexposure limits inoutside air mode0Probability of exceedingexposure limits0Average time of operationper car per year340 h/yr&Air control inrecirculationmode0.32 (U.S.)0.16 (Europe)1234yf concentration in passengercompartment exceeds exposure limitfor large leak and recirculation mode0&ORFigure 11.Fault tree describing risk ofpotentially adverse exposureassociated with a large HFO-1234yf leak into passengercompartmentAdditionalexposures due toinadequate repair inservice1.5Exposure to 1234yfconcentration exceedingexposure limit due tocollision7.5 x 10-11/yrProbability collisiondeforms A-pillar >6“0.0187Frequency ofserious collision5.6 x 10-3/yrProbability evaporatorpiping fails0.05“d”Leak in passengercompartment causedby collision5.2 x 10-6/yrOccupant survivescollision0.9Probability collision does notbreak windows and windowsnot already open0.0001Probability collision does notbreak any other componentin refrigerant cycle0.1Number of occupants pervehicle1.59&&Figure 12.Fault tree describing risk ofpotentially adverse exposureassociated with a HFO-1234yf leak due to vehicle collision“e”Airconcentrationsabove LFL0/yrORService carried outwith inadequateventilation0.006 (U.S.)0.002 (Europe)Probability ofinadequateventilation0.20Work is carriedout by DIYer0.03 (U.S.)0.01 (Europe)&Air concentrationsabove LFL due tosystem rupture0/yrAir concentrationsabove LFL due toequipment leak0/yrShop airconcentrationexceeds mRCL0Rupture ofvehicle systemduring service0.005 /yr&Shop airconcentrationexceeds mRCL0Leak from ACserviceequipmentduring service0.001 /yr&&DIYer has exposureabove mRCL0 /yrExposure to 1234yfabove limit during vehicleservice(per serviced vehicle)0 /yrORService carried outwith inadequateventilation0.097 (U.S.)0.099 (Europe)Probability ofinadequateventilation0.10Work is carriedout by trainedtechnician0.97 (U.S.)0.99 (Europe)&Airconcentrationsabove mRCL0/yrShop airconcentrationexceeds mRCL0Release of canheel contentsduring service0.005 /yrShop airconcentrationexceeds mRCL0Release fromcharge kit whilecharging system0.001 /yrAir concentrationsabove mRCL due toheel release0/yrAir concentrationsabove mRCL dueto charge kit leak0/yrOR&&&Professional technicianhas exposure abovemRCL0 /yrFigure 13.Fault tree describing riskof potentially adverseexposure associated with a HFO-1234yf leak duringvehicle repairNumber of events of possibleHFO-1234yf -associated firefrom small leak0 /yrNumber of events of possibleHFO-1234yf-associated firefrom leak caused by collision1.5 x 10-11/yrTotal number of events where a 1234yffire injury associated with vehicle useis possible (per vehicle and year)1.5 x 10-11/yrNumber of events of possibleHFO-1234yf -associated firefrom medium leak0 /yrNumber of events of possibleHFO-1234yf -associated firefrom large leak0 /yrNumber of vehicles in U.S.and Europe230 million (U.S.)241 million (Europe)&Number of vehicles inU.S. and Europe230 million (U.S.)241 million (Europe)Number of events ofpossible 1234yfassociated fire,professional shop0 /serviced vehicle&ABCDFPotential fire events related to1234yf release associatedwith vehicle repair in Europeand U.S.0 /yrNumber of events of possibleHFO-1234yf -associated firein engine compartment0 /yrEORGNumber of events ofpossible 1234yfassociated fire, DIYlocation0 /serviced vehicleNumber of ACservices pervehicle andyear0.1Potential injurious fire eventsrelated to 1234yf releaseassociated with vehicle usein Europe and U.S.0.004/yr (U.S.)0.004/yr million (Europe)Figure 14.Aggregate risk of fires due to HFO-1234yf releaseDoors andwindows closed0.95Potential injury fromfire related to1234yf release via small leak0 /yrProbabilitysize of leakis small0.94Frequency ofevaporatorleaks4.57 x 10-8/h“A”Air control inoutside air mode0.68 (U.S.)0.84 (Europe)1234yf concentration inpassengercompartment exceedsLFL0&Probability 1234yfconcentration exceeds LELinrecirculation mode0Probability 1234yfconcentration exceeds LELin outside air mode0Probability of LELbeing exceeded0Air control inrecirculation mode0.32 (U.S.)0.16 (Europe)1234yf concentration inpassenger compartmentexceeds LFL0Release due tosudden small leak6.12 x 10-8/hProbability spark frominternal batterywillignite material0Probability smoking-relatedignition source(match/lighter) present3.15 x 10-4Probability sufficient ignitionsource present0OROR&&&Battery spark is withinflammableconcentration area0 (based on CFD)Probabilitydriver or passengersmokes0.21&Ignition source iswithin flammableconcentration area0 (based on CFD)&Probabilitysmokingsource will ignitematerial0Probability vehicle hasinternal battery0.05&Number of hoursvehicle is operatedper year340 hr/yrProbabilitylighting is withflame source0.5Number ofoccupantsper vehicle1.59Factor toaccount for leaksdue to improperrepair1.5Probabilityvehicle hasPTC heater0.30ProbabilityPTCheaterspark willignite material0Probability of batteryshort1 x 10-7Battery short is ofsufficient energy1.0Probability of PTCheater short1 x 10-5PTC heater spark iswithin flammableconcentration area0 (based on CFD)PTC heater shortis of sufficientenergy1.0&Probability PTC heateris powered on0.1Fraction oftime spent invehicle lightingcigarette0.003Figure 15.Fault tree describing risk of fire associated with a smallHFO-1234yf leak into passenger compartmentDoors andwindows closed0.95Potential injury fromfire related to1234yf release via medium leak0 /yrProbabilitysize of leakis medium0.05Frequency ofevaporatorleaks4.57 x 10-8/h“B”Air control inoutside air mode0.68 (U.S.)0.84 (Europe)1234yf concentrationin passengercompartmentexceeds LFL0&Probability 1234yfconcentration exceeds LELinrecirculation mode0Probability 1234yfconcentration exceeds LELin outside air mode0Probability of LELbeing exceeded0Air control inrecirculation mode0.32 (U.S.)0.16 (Europe)1234yf concentration inpassenger compartmentexceeds lower explosivelimit0Release due tosudden mediumleak3.26 x 10-9/hProbability spark frominternal batterywillignite material0Probability smoking-relatedignition source(match/lighter) present3.15 x 10-4Probability sufficient ignitionsource present0OROR&&&Battery spark is withinflammableconcentration area0 (based on CFD)Probabilitydriver or passengersmokes0.21&Ignition source iswithin flammableconcentration area0 (based on CFD&Probabilitysmokingsource will ignitematerial0Probability vehicle hasinternal battery0.05&Number of hoursvehicle is operatedper year340 hr/yrProbabilitylighting is withflame source0.5Number ofoccupantsper vehicle1.59Factor toaccount for leaksdue to improperrepair1.5Probabilityvehicle hasPTC heater0.30ProbabilityPTCheaterspark willignite material0Probability of batteryshort1 x 10-7Battery short is ofsufficient energy1.0PTC heater spark iswithin flammableconcentration area0 (based on CFD&Probability of PTCheater short1 x 10-5PTC heater shortis of sufficientenergy1.0Probability PTC heateris powered on0.1Fraction oftime spent invehicle lightingcigarette0.003Figure 16.Fault tree describing risk offire associated with amedium HFO-1234yf leakinto passenger compartmentDoors andwindows closed0.95Potential injury fromfire related to1234yf release via large leak0 /yrProbabilitysize of leakis large0.01Frequency ofevaporatorleaks4.57 x 10-8/h“C”Air control inoutside air mode0.68 (U.S.)0.84 (Europe)1234yf concentrationin passengercompartmentexceeds LFL0&Probability 1234yfconcentration exceeds LELinrecirculation mode0Probability 1234yfconcentration exceeds LELinoutside air mode0Probability of LELbeing exceeded0Air control inrecirculation mode0.32 (U.S.)0.16 (Europe)1234yf concentration inpassenger compartmentexceeds lower explosivelimit0Release due tosudden large leak6.5 x 10-10/hProbability spark frominternal batterywillignite material0Probability smoking-relatedignition source(match/lighter) present3.15 x 10-4Probability sufficient ignitionsource present0OROR&&&Battery spark is withinflammableconcentration area0 (based onmeasurement)Probabilitydriver or passengersmokes0.21&Fraction oftime spent invehicle lightingcigarette0.003Ignition source iswithin flammableconcentration area0 (based on CFD)&Probabilitysmokingsource will ignitematerial0Probability vehicle hasinternal battery0.05&Number of hoursvehicle is operatedper year340 hr/yrProbabilitylighting is withflame source0.5Number ofoccupantsper vehicle1.59Factor toaccount for leaksdue to improperrepair1.5Probabilityvehicle hasPTC heater0.30ProbabilityPTCheaterspark willignite material0Probability of batteryshort1 x 10-7Battery short is ofsufficient energy1.0Probability of PTCheater short1 x 10-5PTC heater spark iswithin flammableconcentration area0 (based onmeasurement)PTC heater shortis of sufficientenergy1.0&Probability PTC heateris powered on0.1Figure 17.Fault tree describing risk offire associated with alarge HFO-1234yf leak into passenger compartmentLeak in passengercompartmentcaused by collision5.24 x 10-6/yrPotential injury from firerelated to 1234yf release inpassenger compartmentvia collision1.5 x 10-11/yrOccupantsurvivescollision0.9Probability collision doesnot break windows andwindows not already open0.0001Probability collision does notbreak other components inrefrigerant cycle0.1“D”Number ofoccupants pervehicle1.59&Probability collisionproduces ignition sourcewith enough energy toignite refrigerant1.0Probability collisiondeforms A-pillar >6“0.0187Frequency ofserious collision5.6 x 10-3/yrProbability evaporatorpiping fails andrefrigerant is released0.05&Probabilityconcentration inpassenger compartmentexceeds LFL1.0Survivingoccupants do notescape vehicle0.2Figure 18.Fault tree describing risk of fireassociated with a HFO-1234yfleak in passenger compartment caused by collisionPotential injury fromfire related to1234yf release in under hood area0 / yrProbability sufficientignition source present0“E”Number of occupantsper vehicle1.59Probability of LFL beingexceeded in underhood area1.0Number of hours vehicle isoperated per year340 hr/yr&Frequency of leak inunder hood area6.8 x 10-10/hrProbability spark frombattery will ignitematerialTBDORBattery spark is withinflammableconcentration zoneTBD&Probability hotmanifold will ignitematerial0Probability ofbattery cable short1 x 10-5Battery short is ofsufficient energy1.0&Hot manifold iswithin flammableconcentration zone1.0Probability manifoldexceeds autoignitiontemperature0.05Probability gas isactually ignited0Figure 19.Fault tree describing riskof fire associatedwith a HFO-1234yf leak in engine compartmentCurrently subject tofurther testing“F”Possibility of refrigerantrelated fire inprofessional shop0 /yr&Airconcentrationsabove LFL0/yrAir concentrationsabove LFL due tosystem rupture0/yrAir concentrationsabove LFL due toequipment leak0/yrORSufficient ignition sourcepresent0.006Probability smokingrelated source presentwith sufficient energy toignite material0.005Probability other shopactivities in area of releaseproduce sufficient energyto ignite material1 x 10-3ORService carried outwith inadequateventilation0.097 (U.S.)0.099 (Europe)Probability ofinadequateventilation0.10Work is carriedout by trainedtechnician0.97 (U.S.)0.99 (Europe)&Probabilitylighting is withflame source0.5Probabilitytrained techniciansmokes whileworking0.01&Shop airconcentrationexceeds LFL0Rupture ofvehicle systemduring service0.005 /yr&Shop airconcentrationexceeds LFL0Leak from ACserviceequipment duringservice0.001 /yr&Figure 20.Fault tree describing risk of fireassociated with a HFO-1234yfleak during vehicle repair byprofessional service technicians“G”Possibility of refrigerantrelated fire in DIYlocation0 /yr&Airconcentrationsabove LFL0/yrAirconcentrationsabove LFL dueto heel release0/yrAir concentrationsabove LFL due tocharge kit leak0/yrORSufficient ignition sourcepresent0.05Probability smokingrelated source presentwith sufficient energy toignite material0.05Probability other shopactivities in area of releaseproduce sufficient energyto ignite material1 x 10-5ORService carried outwith inadequateventilation0.006 (U.S.)0.002 (Europe)Probability ofinadequateventilation0.20Work is carriedout by DIYer0.03 (U.S.)0.01 (Europe)&Probabilitylighting is withflame source0.5Probabilitytrained techniciansmokes whileworking0.1&Shop airconcentrationexceeds LFL0Release of canheel contentsduring service0.005 /yr&Shop airconcentrationexceeds LFL0Release fromcharge kit whilecharging system0.001 /yr&Figure 21.Fault tree describing risk of fireassociated with a HFO-1234yfleak during vehicle repair by DIYers

### ATTACHMENT A

Ignition Source TablePossible Ignition Sources for Passenger CompartmentScenariosPotential IgnitionSourceIs Source of Sufficient Energy toIgnite RefrigerantIgnition Energy(mJ)SourceTemperature(C)Source Power(W)Conditions when sparking or high temperature occurs(i.e.,normal operation or fault)Burningcigarettes/cigarsNot likely based on 1982 ADLstudy and recent testing of 1234yfNA 400-780oC NAThe ADL study evaluated ignition potential in a 7%methane air mixture. The ADL study results are highlyconservative for HFO-1234yf which is much lessflammable. Activity occurs in normal use but thereis avery brief time of useElectrical cigarettelighter (nickelchromium heatingelement)Not likely based on 1982 ADLstudy and recent testing of 1234yfNA NA NA The ADL study evaluated ignition potentialin a 7%methane air mixture. The study results are highlyconservative for HFO-1234yf which is much lessflammable.Activity occurs in normal use but there is a very brief timeof useLit match Possibly ND 600-800oC ND Occurs in normal use but there is a very brief time of useButane lighter Possibly (heat of combustion:49MJ/kg)1977oC NA Activity occurs in normal use but there is a very brief timeof useElectricalequipment inpassengercompartmentNot likely, ADL study founddevices such as car radios andclocks did not ignite 7% methaneatmosphereND ND ND The ADL study evaluated normal operation of thealternator, starter relay, distributor and spark plug inhousing. Other passenger compartment electronics (e.g.,power windows) presumably present a lower level ofrisk.Starter/ignitionNot likely based on 1982 ADLstudyND ND ND OEMs felt other ignition sources would better represent theworst case.RadioNot likely based on 1982 ADLstudyNA NA NA ADL study suggests this source is not a concern in normaloperation.PassengeritemsNot likely, based on ADL study forclocks and radios, passengeritems would be expected toproduce a lesser hazard.ND ND NDStatic spark frompassengers incontact withcarpet/upholsteryNo, an upper end value for ahuman static electricity dischargeis given as 20 mJ, well below theignition energy of 1234yf.approx. 20 mJ orlessNANAThe value of 20 mJ is widely quoted but we requirereliabledocumentation for this value.Internal battery Yes, OEM members felt that anexternal short of a battery locatedinside the vehicle could havesufficient energyND NA 95/110 A800/950 AData from Fiat for passenger transportation versionoftruckPTC heaters Possibly, location of PTC heaterin the duct could result inrefrigerant contact with source atmaximum concentrationND ND 1.5kw with30Amp fuse;1 kW with 13.5V.Data from two OEMsND – no data available NA – not applicable tothe source in questionPossible Ignition Sources for Repair Worker ScenariosPotential IgnitionSourceIs Source of SufficientEnergy to IgniteRefrigerantIgnition Energy(mJ)SourceTemperature(C)Source Power(W)CommentBurningcigarettes/cigarsNot likely (based on 1982ADL study and recentHFO-1234yf testing)NA 400-780oC NA Will containers of 1234yf display aflammability warning?Electrical cigarettelighterNot likely (based on 1982ADL study and recentHFO-1234yf testing)NA NA NA Are there any statistics for frequency ofelectrical lighterversus butane lighters?Lit match Yes (based on recenttesting)ND 600-800oC ND Will containers of 1234yf display aflammability warning?Butane lighter Yes (based on recenttesting)(heat ofcombustion= 49MJ/kg)1977oC (heat ofcombustion: 49MJ/kg)NA Will containers of 1234yf display a flammabilitywarning?AC service units No, equipment will bedesigned to be nonsparkingNA NA NAOther AC serviceequipment (e.g.,detectors)Possible, but ignitionpotential will be far lessthan activities such aswelding, grinding, etc.NDNDNDSparks fromactivities that maybe performed onother vehicles(e.g., metalsanding, weldingor grindingassociated withbody work)Possible, grinding,sanding or welding metalparts would generatesparks/arcs of very highenergy1 to 1000 mJ(Eckhoff, 2003)Acetylene/O2welding -3300oCNA A MACS survey indicated that most mobile air conditioningshops use flammable gases in their operations. Acetylenewas in use in 82% of shops, propane in 18%. Open flameoperations included brazing (47% of shops), cutting(29%),soldering (14%), and welding (65%) (U.S. EPA, TigerTeamReport, Oct. 12, 2007). Not that these numbers maynot berelevant for the small 2-vehicle shop used for airmodeling.Lights used duringrepair, if these areof high wattageand pulled intowards theengine areaUnlikely. Severalincandescent or halogenlights would be required incontact with gas cloud.NA Tungstenhalogen: 600-900oCIncandescent:100-300oCNAND – no data availableNA – not applicable to the source in questionPossible Ignition Sources for Engine Compartment ScenarioPotential IgnitionSourceIs Source of SufficientEnergy to IgniteRefrigerantIgnition Energy(mJ)SourceTemperature (C)Source Power (W) Conditions when sparks or hightemperature occurs (normal or fault)Equipment sparksfrom vehiclecomponents while inoperationPossible, broken wiringwas able to ignite a 7%methane-air mixture in theADL study. Unclear if thesame would be true for1234yf.ND NA ND This source is probably adequately addressedby considering the effect of a battery cableshort.Battery Possible with short acrossterminalsND NA 36 kW (12 V boatbattery)FaultHot surfaces in/nearengine compartment(would need toexceed autoignitiontemperature ofrefrigerant)Battery No NA 200oC NA Fault (when crushed)Exhaust System Possible NA 600oC NA Under strenuous uphill climbCatalytic conv. NA 200-900oC (internaltemp)NACarley, 2007Fires generatedfrom otherautomotivecomponents (e.g.,motor oil leaks)Possible ~2000oC (gasolineheat of combustion:47 mJ/kg)Fault.DuPont/Honeywell test data suggest thepotential for HFO-1234yf to contributesignificantly to a fire initiated by othermaterials may be limited.ND – no data availableNA – not applicable to the source in question

### ATTACHMENT B

MODELING RESULTS FOR REPAIR WORKER SCENARIOS: R-12Plots of Concentration vs. Time for Professional Mechanic ExposureLeak Due to Complete Evaporator Rupture During Service01002003004005006007008000 100 200 300 400 500 600Time in minutes

R-12 Concentration in ppm5-minute TWA = 708 ppmPlots of Concentration vs. Time for Service Technician ExposureLeak from Service Equipment During Service0204060801001201401601800 100 200 300 400 500 600Time in minutes

R-12 Concentration in ppm30-minute TWA = 139 ppmPlots of Concentration vs. Time for DIY ExposureRelease of Heel Contents of 2 Cans of R-12 Over 90Minutes05001,0001,5002,0002,5003,0000 100 200 300 400 500 600Time in minutes

R-12 Concentration in ppm30-minute TWA = 2,182 ppmPlots of Concentration vs. Time for DIY ExposureSmall Leak from 2 Cans of R-12 While Charging05,00010,00015,00020,00025,00030,00035,00040,0000100200300400500600Time in minutes

R- 12 Concentration in ppm30-minute TWA = 30,896 ppm

### ATTACHMENT C

MODELING RESULTS FOR REPAIR WORKER SCENARIOS: HFO-1 234yfPlots of Concentration vs. Time for Service Technician ExposureLeak Due to Complete Evaporator Rupture During Service01002003004005006007000100200300400500600Time in minutesMaximum Concentration = 590 ppm5-minute TWA = 566 ppm30-minute TWA = 464 ppm

HFO - 1234yf Concentration in ppmPlots of Concentration vs. Time for Service Technician ExposureLeak From Service Equipment During Service0204060801001201401600100200300400500600Time in minutesMaximum Concentration = 146 ppm5-minute TWA = 141 ppm30-minute TWA = 122 ppm

HFO - 1234yf Concentration in ppmPlots of Concentration vs. Time for DIY ExposureRelease of Heel Contents of 2 Cans of HFO-1234yf Over 90 Minutes0500100015002000250030000 100 200 300 400 500 600Time in minutes

1234yf Concentration in ppmMaximum Concentration = 2,670 ppm5-minute TWA =2,636 ppm30-minute TWA = 2,493 ppmPlots of Concentration vs. Time for DIY ExposureSmall Leak From 2 Cans of HFO-1234yf While ChargingAC System050010000150002000025000300003500040000450000100200300400500600Time in minutesMaximum Concentration = 38,946 ppm5-minute TWA = 37,800 ppm30-minute TWA = 32,800 ppm

HFO- 1234yf Concentration in ppm

### ATTACHMENT D

LIST OF TECHNICAL TERMS AND ACRONYMS USED IN THE RI SK ASSESSMENTG:\projects\206703\1234yf\Deliverables\Acronyms 

### 1 List of Technical Terms and Acronyms Used in the Ri sk Assessment

Term or Acronym Full name Explanation

ACGIH American Conference of

Governmental Industrial Hygienists A not-for-profit organization of industrial health

professionals. A key activity of this group is the setting of Threshold Limit Values (TLVs), which are health-based limits for worker exposures to chemicals and other agents ( e.g ., noise). Acute toxicity - Concerns adverse health effects that are related to single or short-term ( e.g., several hour) exposures.

AEGL1 - Exposure levels developed by U.S. EPA to address once-in-a-lifetime or rare exposures to airborne chemicals. Level 1 indicates concentrations above which non-disabling, reversible discomfort may

occur.

Ames assay - A toxicological test for genotoxicity in which a material of concern is applied to specialized bacterial cultures which are subsequently evaluated for signs of DNA mutation.

ANSI American National Standards Institute A private institute in the U.S. that oversees the

development of testing and production standards for materials and devices. AR Alternative Refrigerant A new refrigerant intended to replace R-134a in mobile air conditioning systems.

ASHRAE America Society of Heating,

Refrigerating and AirConditioning Engineers An international organization which develops standards related to refrigeration processes and th e design and maintenance of indoor environments Carcinogenicity, Carcinogenic - Producing cancer, having the potential to produce

cancer.

Cardiac sensitization - The ability of certain chemicals to render the hear t more sensitive to the effects of epinephrine (also called adrenalin).

CFC Chlorofluorocarbons Hydrocarbons in which all of the hydrogen atoms have been replaced with chlorine or fluorine atoms, for example, dichlorodifluoromethane.

CFD Computational Fluid Dynamics A computational methodology which yields predictions of the flow of materials such as liquid s or gases.

Chromosomal aberration test - A toxicological test for genotoxicity which evaluates the potential for a material to cause damage to genetic material when a cell divides.

Chronic toxicity - Concerns adverse health effects related to exposure s lasting longer than 6 months and potentially as lon g as a lifetime.

DIY Do It Yourselfer An individual who performs automotive repairs without using the services of a professional automotive repair technician. Epinephrine (also called adrenalin) - A natural hormone produced which mediates the body’s response to stress.

FTA Fault Tree Analysis A methodology for studying the chain of events leading to system failures and for quantifying the resulting risks.G:\projects\206703\1234yf\Deliverables\Acronyms 

### 2 List of Technical Terms and Acronyms Used in the Ri sk Assessment

Term or Acronym Full name Explanation

Genotoxicity - Causing damage to the genetic material of the cell. Genotoxicity can be a possible indication of carcinogenic potential.

GWP Global Warming Potential The potential of a particular chemical to contribut e to the greenhouse gas effect measured over a specific time frame ( e.g. , 100 years) and often standardized to the effect of CO 2 .

HCFC Hydrochlorofluorcarbons Hydrocarbons containing, in addition to hydrogen and carbon atoms, varying substitution with fluorin e and chlorine atoms, for example chlorodifluoromethane.

HFC Hydrofluorocarbons Hydrocarbons containing, in addition to hydrogen and carbon atoms, varying substitution with fluorin e atoms (but no chlorine atoms), for example, 1,1- difluoroethane. HFO Hydrofluoroolefin A fluorinated hydrocarbon which has at least 1 carbon-to-carbon double bond.

IPCC Intergovernmental Panel on

Climate Change A scientific intergovernmental body established by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP). The IPCC studies aspects of climate change and makes recommendations for lessening human activities that may potentially alter the environment.

ISO International Standards

Organization An organization working to harmonize chemical and equipment testing standards that have been adopted by different countries.

LC50 Lethal Concentration 50 The concentration of a gas or vapor which kills 50% of the test animal population after an acute (often 4- hour) exposure.

LOAEL Lowest Observed Adverse Effect Level The lowest dose evaluated in a toxicity study whic h

produced signs of adverse effects in the test animals. By definition, the LOAEL represents a higher concentration than the NOAEL.

Micronucleus test - A test for genotoxicity which evaluates the potenti al for a material to induce chromosome fragmentation when cells divide.

mRCL Modified Recommended

Concentration Limit A health-based exposure limit used in this risk assessment which differentiates between stressful and non-stressful exposure situations.

NIOSH National Institute of

Occupational Safety and Health A research branch of the U.S. Centers for Disease Control which establishes Recommended Exposure Limits (RELs), which are health-based guidelines for worker exposures to chemical agents.

NOAEL No Observed Adverse Effect Level The highest dose tested in a toxicity study which

does not produce signs of adverse effects.

NOEL No Observed Effect Level The highest dose tested in a toxicity study which does not produce signs of any effects. Often used when the effect of interest may not necessarily be considered adverse.G:\projects\206703\1234yf\Deliverables\Acronyms 

### 3 List of Technical Terms and Acronyms Used in the Ri sk Assessment

Term or Acronym Full name Explanation

NRC National Research Council A unit of the U.S. National Academy of Sciences, consisting of scientists from different disciplines who advise the U.S. government in matters of science policy.

ODP Ozone Depletion Potential The potential of a particular chemical to cause stratospheric ozone depletion measured over a specific time frame ( e.g ., 100 years).

OECD Organization for Economic

Cooperation and Development In the context of this report, an international bod y which has developed standard chemical testing protocols.

RCL Recommended Concentration Limit A health-based exposure limit developed in

ANSI/ASHRAE Standard 34-2007 which is meant to be protective for acute exposures to refrigerant s.

SNAP Significant New Alternatives Program U.S. EPA program which evaluates new chemicals

proposed as replacements for those with ozone depletion or global warming potential. Subacute toxicity - Concerns adverse health effects that are related to exposures lasting several days to a few weeks. Subchronic toxicity - Concerns adverse health effects that are related to exposures lasting a few weeks to several months.

TEEL1 Temporary Emergency Exposure

Limit, level 1 An acute exposure level developed by the U.S. National Oceanic and Atmospheric Administration. Level 1 indicates a level which produces only minimal and transient health effects. TWA Time Weighted Average The average concentration over a specified time interval ( e.g ., 5 minutes or 8 hours).