## MEMORANDUM

To: Margaret Sheppard , U.S. EPA CC: Yaidi Cancel, U.S EPA From: Emily Herzog, Ed Carr, Kara Altshuler, Veronica Kennedy, Mark Wagner, ICF International Date: May 25 , 2010 Re: Revised Assessment of the Potential Impacts of HFO - 1234yf and the Associated Production of TFA on Aquatic Communities , Soil and Plants, and Local Air Quality (Deliverable under EPA Contract Number EP -W- 06 - 008 Task Order 0 38 , Task 06) Please find attached a revised version of a paper that examines the emissions of HFO - 1234yf and the associated production of TFA under several scenarios. The assessment has been revised to reflect a revised approach to analyzing impacts of HFO - 1234yf emissions. This approach used EPA’s CMAQ model version 4.7 with the chemical mechanism incorporating chemistry and reaction rates for HFO 1234yf transformation to TFA. The results from this analysis confirm our previous conclusions that projected emissions of HFO - 1234yf should not result in a significant risk to aquatic communities, s oil and plants, or local air quality. Please contact Mark Wagner at 202 - 862 - 1155 with any questions or comments.

# Assessment of the Potential Impacts of

HFO - 1234yf and the Associated Production of TFA on Aquatic Communities, Soil and Plants, and

Local Air Quality

Prepared for: Stratospheric Protection Division Office of Atmospheric Programs U.S. Environmental Protection Agency

1310 L Street, NW Washington, DC 20005 Prepared by: ICF International 1725 E ye Street, NW, Suite 1000 Washington, DC 20006 May 25 , 2010

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## Table of Contents Foreword ................................ ................................ ................................ ............................... i Executive Summary ................................ ................................ ................................ ............... 1 1. Introduction ................................ ................................ ................................ ................... 1 2. Production and Environmental Fate of Trifluoroacetic acid (TFA) ................................ ..... 3 3. Toxicity of Trifluoroacetic Acid (TFA) ................................ ................................ ............... 4 3.1. Aquatic and Environmental Toxicity ................................ ................................ ............................. 4 3.2. Human and Animal Toxicity ................................ ................................ ................................ .......... 8 

### 4. Assessment of Potential HFO - 1234yf Emissions ................................ ............................. 10 4.1. Scenarios of HFO - 1234yf Market Penetration ................................ ................................ ............ 10 4.2. HFO - 1234yf Emission Assumptions ................................ ................................ ............................ 11 4.3. Estimated Emissions of HFO - 1234yf ................................ ................................ ........................... 11 

### 5. Assessment of Potential Impacts of HFO - 1234yf and T FA ................................ .............. 13 5.1. TFA Rainwater Concentrations ................................ ................................ ................................ ... 13 5.2. TFA Dry Deposition ................................ ................................ ................................ ..................... 14 5.3. Ground Level Ozone Concentrations ................................ ................................ .......................... 15 

### 6. Discussion of Results ................................ ................................ ................................ .... 16 6.1. Summary of Findings ................................ ................................ ................................ ................... 17 6.2. Limitations of this Analysis ................................ ................................ ................................ .......... 17 

### 7. References ................................ ................................ ................................ ................... 20

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i



## Foreword In a previous analysis conducted in the Spring/Summer of 2009, ICF International assessed the potential impacts of HFO - 1234yf emissions and the associated production of TFA on aquatic communities and local air quality. 1 Using the research and resources available at the time, ICF made numerous conservative as sumptions regarding the potential emissions and atmospheric reactivity of HFO - 1234yf. Specifically, in the earlier assessment, ICF scaled emissions of SO 2 proportionately to the projected emissions of HFO - 1234yf based on the understanding that the lifeti me cycle for SO 2 to sulfate conversion and removal in cloud droplets is similar to that of HFO - 1234yf to TFA removal in cloud droplets. ICF then applied EPA’s three - dimensional community multiscale air quality model (CMAQ) using emissions of SO 2 only from the Los Angeles and Houston air basins to determine the dry sulfate deposition and sulfate rainwater concentrations for a typical one -year (2001) period using hourly meteorological data. 2 The sulfate concentrations were then scaled on a n emissions molar adjusted basis to estimate the maximum potential concentration of TFA in rainwater and dry deposition both on an annual basis, as well as for the maximum month downwind deposition for both Houston and Los Angeles. To account for the minor difference in l ifetime for sulfate and for TFA (3 days vs. 5 days) due to in - cloud removal, a log - log adjustment was also made to the output of the model to estimate TFA concentrations in rainwater. The results from th e earlier analysis estimated the highest monthly aver age TFA concentration in rainwater to be 1.8 mg/L in 2050 located downwind of Los Angeles, and only 0.008 mg/L downwind of Houston for the same year . The maximum concentrations in both annual and monthly rainwater for Houston were well below the 0.12 m g/L no observed effect concentration (NOEC) reported for the most sensitive freshwater green algae species tested at the time . However, Los Angeles showed the potential for concentrations to exceed the no effect levels for this algae species starting in 202 0 for the monthly maximum concentration and 2025 for the annual average maximum. In addition, beginning sometime between 2025 and 2030 , it was estimated that the rainwater concentrations could exceed the NOEC of 1 mg/L for vernal pool plant species in ve rnal pools near Los Angeles during the month of July. However, the maximum annual average of 0.29 mg/L in rainwater downwind of Los Angeles in 2050 and both the maximum annual and monthly averages for Houston were estimated to be significantly below the N OECs for all vernal pool species. In regards to dry deposition of TFA, ICF found that the monthly peak dry deposition occurred in March for Los Angeles and in July for Houston. The modeling results indicated that projected maximum annual average deposit ion of TFA will be greater after 2015 than what has been measured in vernal pools in the last decade in Northern California. However, current toxicity data on ecological receptors indicate d that TFA has low toxicity for most aquatic microbial, plant , and animal species ; does not bioconcentrate ; and does not appear to have effects on germination on those species tested. .

1 ICF International. 2009. Assessment of the Potential Impacts of HFO - 1234yf and the Associated Production of Trifluoroacetic Acid (TFA) on Aquatic Communities and Local Air Quality . Prepared by ICF International for U.S. EPA. July 31, 2009. Available online at www.regulations.gov in docket ID: EPA- HQ- OAR - 2008 - 0664 - 0037 . 2 More information is available on the CMAQ model at http://cmascenter.org/ .

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ii To estimate potential impacts on local air quality, ICF assumed the ozone creation from the release of HFO - 1234yf to be similar to that of the volatile organic compound (VOC) ethylene, as described by Papadimitriou et al. (2008). The Houston - Galveston region and the South Coast Air Basin in California were again examined to analyze the potential impacts of using HFO - 1234yf on ground level ozone, assuming business as usual emissions of NO x and VOC. For Houston, data were taken from the Post 1999 Rate of Progress and Attainment Demonstration SIP to predict future emissions of NOx and VOC (Texas Natural Resource Commission, 2000) up to the 2 019 ozone attainment year based on model simulations during the summer ozone season. Data for the South Coast region were taken from the 2007 Air Quality Plan, which predicts future emissions of NO x and VOC for attaining the ozone standards for 2017 and 2 023 (South Coast, 2007), again based on modeling during the summer ozone season. Data for future year projections after 2023 for both Houston - Galveston and the South Coast were estimated based on a need for continued reduction in emissions due to increas ed temperatures from global warming. Climate change impacts reported in the IPCC’s 4th Assessment Report (IPCC, 2007) predict that by 2050 global warming will increase average daily ozone levels across the eastern U.S. by 3.7 ppb based on likely emission levels. It was assumed that the regional air quality plan would be adjusted accordingly to compensate for this expected increase. Thus, the Houston - Galveston regional emissions of both NO x and VOCs were proportionately reduced to maintain attainment of t he current 8 - hour ground level ozone standard of 75 ppb. While less specific data is available for the South Coast, IPCC projections report significant increase in the frequency and magnitude of ground level temperature, which leads to higher ozone concen trations. Thus, it was assumed that the same level of increase in background ozone concentration would be seen for the South Coast region as projected for the eastern United States. As a result, regional emissions for the South Coast after 2023 were also proportionately reduced to account for the expected 3.7 ppb increase in ozone due to global warming . Results from this earlier analysis showed that for Houston - Galveston ground level ozone potentially could increase by less than 1% , assuming a VOC - limited environment, or an environment where ozone formation is limited by the availability of VOC (not the availability of NOx). For the South Coast (i.e., around Los Angeles), ground level ozone was expected to increase by about 1.4%. These percentage increas es in ozone suggest how much ground level ozone could potentially increase as a result of the use of HFO - 1234yf, relative to the projected emissions of NOx and VOC over time . For other areas of the United States that were not examined in th e analysis, a s imilar conclusion was drawn: HFO - 1234yf emissions have the potential to increase ground level ozone; however, the percent increase is expected to impact other regions to a much lesser extent . Given the limitations and conservative nature of this earlier a nalysis, ICF concluded that (a) projected levels of TFA in rainwater should not result in a significant risk of ecotoxicity; (b) d ry deposition is somewhat of a concern, however more research is needed to fully understand the impacts of dry deposition on s oil, plants, and aquatic communities; and (c) non - attainment resulting from HFO - 1234yf emissions is not likely to be a major concern for local air quality in most locations. Since the completion of the analysis, new information and findings have been broug ht to the attention of ICF. As a result, the analysis has been revised and is described in the remainder of this paper.

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1 100 -year GWPs of Selected HCFCs and HFCs Gas IPCC Second

Assessment Report (SAR) IPCC Fourth

Assessment Report (AR4) HCFC-22 1,500 1,810 HCFC- 123 90 77 HCFC- 124 470 609 HCFC- 141b 600 725 HCFC- 142b 1800 2,310 HFC-23 11,700 14,800 HFC-32 650 675 HFC- 125 2,800 3,500 HFC- 134a 1,300 1,430 HFC- 143a 3,800 4,470 HFC- 152a 140 124 HFC-227ea 2,900 3,220 HFC-236fa 6,300 9,810 HFC-245fa NA 1,030 HFC-365mfc 860 794 Source: IPCC (1996), IPCC (2007) 

## Executive Summary HFO - 1234yf is a chemical under development for use in motor vehicle air conditioning (MVACs) and has the potential t o be used more broadly in other end use sectors. Although HFO - 1234yf has a low global warming potential (GWP) and is thus a desirable alternative to commonly used hydrofluorocarbons (HFCs), there is concern that use of HFO - 1234yf could negatively impact b oth local air quality and aquatic communities. HFO - 1234yf has a reactivity that could potentially lead to increased levels of ground - level ozone. Additionally, there is concern associated with the atmospheric degradation of HFO 1234yf, which results in t he production of trifluoroacetic acid (TFA). TFA has the potential to accumulate on soil, on plants, and in aquatic ecosystems over time and to impact the supported plant and animal communities. The following paper describes the production and fate of TF A, provides an in depth discussion of the toxicity of TFA, discusses the scenarios developed for this analysis, and discusses the potential impacts HFO - 1234yf could have on aquatic ecosystems, soil, plants, and local air quality. The scenarios developed for this analysis project HFO - 1234yf emissions and subsequent production of TFA up to 2050 based on market penetrations in the domestic market. In conjunction with three dimensional air quality modeling conducted using EPA’s Community Multiscale Air Qual ity (CMAQ) model (CMAQ - Byun, D. W., and J. K. S. Ching. 1999) these projections were used to estimate the maximum potential concentration of TFA in rainwater, the maximum amount of dry deposited TFA, and the potential increase in ground level ozone. Fro m this analysis, it was concluded that the projected maximum concentration of TFA in rainwater and the amount of TFA dry deposited should not result in a significant risk of ecotoxicity, and that n on - attainment resulting from HFO - 1234yf emissions is unlike ly to be a major concern for local air quality in most locations. 

## 1. Introduction Since the inception of the Significant New Alternatives Policy (SNAP) program, a large number of substitutes have been reviewed in support of the development and commercializat ion of viable replacements for ozone depleting substances (ODS) across all of the end use sectors that have traditionally used ODS. Approved substitutes have included hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), blends, hydrocarbons, and n ot - in - kind alternatives. The HFCs have been a significant alternative for many sectors because of their non - ozone depleting nature, but due to the high global warming potential (GWPs) of HFCs, new low GWP alternatives are being developed. In particular, HF O - 1234yf is a chemical under development for use in motor vehicle air conditioning (MVACs) and has the potential to be used more broadly in the refrigeration/air conditioning end use sectors. HFO - 1234yf is proposed to replace HFC - 134a in

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2 Sources of TFA Species Global TFA

P roduction (t yr- 1 ) Halothane 520 Isoflurane 280 HCFC - 123 266 HCFC - 124 4440 HFC - 134a 4560 Fluoropolymers 200 TFA (lab use etc) Negligible Total 10,266 Source: IPCC/TEAP 2005 MVACs and has a particularly low GWP of 4.4 compared to the HFCs and HCFCs currently in use (as shown in the text box above). HFO - 1234yf has the potential to significantly reduce the climate impacts of MVACs as well as that of other sectors (Papadimitriou et al., 2008). Although the use of HFO - 1234yf could potentially mitigate greenhouse gas emissions, it could also potentially contribute to increased levels of ground level ozone. While the maximum incremental reactivity of HFO - 1234yf is expected to be similar to that o f ethane (Carter 2009), it is possible that in some locations the reactivity could be considerable higher depending on regional conditions. Therefore, HFO - 1234yf may pose a risk to local air quality, if emitted in sufficient quantities. There is additiona l concern associated with the atmospheric degradation of HFO - 1234yf which results in the production of trifluoroacetic acid (TFA). TFA is a well - known environmental contaminant that results from the degradation of halothane (an anesthetic introduced clini cally in 1956), isoflurane, and fluoropolymers as well as HFC - 134a, HCFC - 123, and HCFC - 124. In its 2006 report on Environmental Effects of Ozone Depletion and Its Interactions with Climate Change, the United National Environment Programme (UNEP) stated th at risks to humans and the environment from TFA and other degradation products of HCFCs and HFCs “are considered minimal.” HFO - 1234yf was not considered in the basket of HFCs at the time that UNEP prepared its 2006 report. At the current rate of product ion from atmospheric degradation of HFCs and HCFCs, the level of TFA is projected to reach close to 0.0001 mg/L in 2020 in rainwater, about 1,000 times lower than the lowest reported no observed effect concentration of 0.1 2 mg/L (Boutonnet et al. 1999). Ho wever, the rate of production of TFA from HFO - 1234yf is significantly higher than that associated with HFC - 134a. With the anticipated use (and associated emissions) of HFO - 1234yf, TFA has the potential to accumulate in seasonal wetlands, which have both li ttle to no outflow and high evaporation rates (e.g., vernal pools, playa lakes), over time and may impact the supported plant and animal communities in those wetlands. This paper examines the emissions of HFO - 1234yf and the associated production of TFA u nder several scenarios and assesses the potential impacts of HFO - 1234yf and TFA on aquatic communities and local air quality. The remainder of the document is organized as follows:
 Section 2 describes the production and fate of TFA;  Section 3 provides an i n - depth discussion of the toxicity of TFA;  Section 4 discusses the scenarios developed for this analysis and the resulting emissions of HFO 1234yf;  Section 5 discusses the results of this analysis and presents an assessment of the potential impacts on aqu atic ecosystems and local air quality; and  Section 6 discusses the results and identifies the limitations of the analysis .

### TFA Assessment

3 Chemical and Physical Properties of TFA Molecular Formula CF 3 C(O)OH Mo lecular Weight 114.02 Vapor Pressure 1.10 x 10 2 mm Hg Boiling Point 72.4  ̊C Melting Point - 15.4  ̊C Log Kow 0.50 pKa 0.25-0.5 Koc 3 Henry’s Law Constant 1.11 x 10 - 7 atm - m 3/mol Solubility Miscible in water at 20  ̊C Source: Hazardous Substance Data B ank 

## 2. Production and Environmental Fate of Trifluoroacetic acid (TFA) Trifluoroacetic acid (TFA) is produced during the atmospheric break down of many fluorocarbons (e.g., CFC replacements) , including HFO - 1234yf . The process is initiated by the gaseous reaction of these fluorocarbons with hydroxyl (OH) radicals, eventually resulting in carbonyl products. These halogenated carbonyl compound s remain in the atmosphere for 11 days on average before they are encapsulated into water droplets and hydrolyzed to TFA (Papadimitriou et al., 2008). D ue to the re - evaporation of cloud droplets , TFA may also re - evaporate to the gas phase . A small porti on (at most 5%) of gas phase TFA is estimated to react with OH and be dry- deposited to the earth’s surface (Kotamarthi et al. 1998). However, TFA is considered highly soluble and is instead expected to reincorporate into cloud and rainwater, eventually be ing wet - deposited to the oceans and land surfaces (Kotamarthi et al. 1998). After deposition, TFA enters aquatic environments. TFA is a strong acid with a reported p K a range of ~0.25 - 0.5; therefore, it is expected to completely ionize at any pH that occu rs naturally (Boutonnet et al. 1999; HSDB 2008; Kotamarthi et al. 1998). Due to its high solubility, volatilization from aqueous solution is not considered to be a significant transport pathway. In the aqueous phase, TFA does not absorb light at wavelengths greater than 250 - 290 nm (Boutonnet et al. 1999; HSDB 2008), thus excluding photolysis as a degradation pathway. There are few studies available that provide information on the movement of TFA in solid and liquid media. Based on a low Henry’s Law constant and a low K ow (n - octanol/water partition coefficient) (Franklin 1993), it has been predicted that TFA would partition predominantly in water (Bowden et al. 1996; 1998). However, studies of TFA adsorption in soils have been performed in both upland fo rest and forest wetland environments in the Hubbard Brook Experimental Forest in New Hampshire, with varying results (Likens et al. 1997; Richey et al. 1997). These studies indicate that TFA is measurably retained in soils in those environments, with wetla nd systems retaining more applied TFA than the forest system. For example, within 1 - 3 weeks, applied TFA moved through the forest soil profile with drainage water, and more than 70% of the TFA exited the upland forest in drainage water. The authors sugge sted that TFA would likely be leached from the soil and enter drainage waters over approximately 2 years until the TFA concentrations returned to pre - application levels. In the case of the forest wetland, TFA did not move readily with water, and <5% of th e applied TFA moved out of the wetland in drainage water. Interestingly, the authors did not see an increased concentration of TFA in drainage waters following dry spells and the drying of the wetland, indicating that the compound was not concentrating du e to evaporation. The authors interpreted these data to indicate the compound was being retained in the vegetation (20 - 50%) and forest wetland soils (20 - 60%). A separate study investigated the properties of soils that affect TFA retention (Richey et al. 1997). The data indicate that soils with greater amounts of organic matter preferentially retain TFA compared to well - drained, aerobic soils, with organic soils from wetlands, peatlands, and a boreal forest showing the

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4 greatest retention of the compound. Further, TFA was retained to a greater extent in lower pH environments, but was not retained in the presence of high concentrations of fluoride, chloride, and sulfate ions. As mentioned before, TFA is a strong acid; these data suggest that soils impacte d by acid rain may be further impacted by the deposition of TFA, because of its acidity, although the presence of SO 4- (currently a primary component of acid rain) in large quantities will inhibit TFA retention. Studies evaluating effects of TFA depositio n/adsorption on soil or sediment chemistry have not been identified. Effects of TFA on soil microbial communities are described below. Studies show that TFA is extremely persistent in aquatic environments. The estimated half- life for degradation of TFA in typical environmental conditions via reaction with hydroxyl radicals in water would be  100 years (Ellis et al. 2001). Further, data provided by Alternative Fluorocarbons Environmental Acceptability Study (AFEAS) indicates that TFA is resistant to oxidati ve and reductive degradation and biodegradation (Franklin 1993; Berends et al. 1999; Boutonnet et al. 1999). This is supported by recent independent data by Emptage et al. (1997) showing that TFA is not degraded by methanogenic bacteria from various environmental sources (freshwater sediments, marine sediments, rumen, and an anaerobic digestor sample). More recently, however, Kim et al. (2000) demonstrated cometabolic biodegradation of l ow concentrations ( ≤30 mg F/L) over the span of 100 weeks in small (10 L) fermentation batches of a mixture of unidentified bacteria. The issue of environmental degradation of TFA is a subject of continuing research and the data currently do not allow one to predict whether this environmental sink will moderate TFA loading in the future. 

## 3. Toxicity of Trifluoroacetic Acid (TFA) 3.1. Aquatic and Environmental Toxicity3 TFA is mildly toxic to plant life (i.e., phytotoxic). In certain environmental conditions, TFA might reach concentrations in the future that may be toxic to surrounding plant life. For example, studies show that as seasonal wetlands evaporate, the remaining TFA is concentrated; TFA in these standing pools can be retained for years, adding to long -term accumulation of TFA in wetlands (Cahill et al. 2001). Increased concentrations of TFA can inhibit growth in the most sensitive plants and may affect the survival of endangered and endemic plant species (Cahill et al. 2001). Lower aquatic life forms, such as bacteria, certain aquatic plant species, small invertebrates, and segmented worms (such as earthworms), do not accumulate large quantities of TFA, and are not significantly impacted by the compound (Berends et al. 1999; Boutonnet et al. 1999). Acco rding to a study on the aquatic toxicity of TFA, systems exposed to a concentration of 0.10 mg/L are expected to experience no adverse effects (Berends et al. 1999), although many organisms show no toxic effects at much higher concentrations of the compoun d (see Table 1 below). Lowest observed effect concentrations (LOEC) and no observed effect concentrations (NOEC), as summarized by Boutonnet et al. (1999), 4 are shown in Table 1 . Note that values are l isted both for the

3 T he toxicity of TFA has been evaluated in algae, microbial benthic organis ms, fish, and freshwater plants. Terrestrial plant, laboratory animal, and human study data are not reviewed in this section. 4 Research sponsored by the Alternative Fluorocarbons Environmental Acceptability Study (AFEAS) and conducted by independent scien tists at universities, private research organizations, and government laboratories.

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5 sodium salt of TFA (NaTFA) and estimated equivalent TFA, in parentheses. Boutonnet et al. (1999) measured NaTFA, because the free acid itself is not likely to be present at high concentrations in environmental media. Table 1 : Summary of Studies on the Aquatic Toxicity of Sodium Trifluoroacetate (mg/L) Aquatic Organisms EC50 a LOEC b NOEC c Selenastrum capricornutum (freshwater green alga) (new name: Pseudokirchneriella subcapitata ) 4.8 (4.0) d >1.2 (1.0) 0.36 (0 .30) e <0.36 (0.30) 0.12 ( 0.1 ) Anabaena flos-aquae (blue -green alga) 2400 (2011) 1200 (1000) 600 (500) Navicula pelliculosa (freshwater diatom) 1200 (1000) 1200 (1000) 600 (500) Skeletonema costatum (marine diatom) --- --- 2400 (2011) Chlorella vul

garis (freshwater green alga) --- --- 1200 (1000) Chlamydomonas reinhardtii (freshwater green alga) --- --- >120 (>100) Microcystis aeruginosa (blue -green alga) --- --- >117 (98) Phaeodactylum tricornutum (marine alga) --- --- >117 (98) Dunaliella tertiolecta (marine alga) --- --- >124 (104) Euglena gracilis (freshwater alga) --- --- >112 (94) Daphnia magna (crustacea) --- --- 1200 (1000) Brachydanio rerio (Zebra fish) --- --- 1200 (1000) Lemna gibba (duckweed) --- vegetative growth 1100 (9 20) 600 (500) 300 (250) a EC50 = test concentration resulting in an effect in 50% of the organisms tested ; the table lists EC50 for biomass integral (adverse effects on growth) b LOEC = lowest observed effect concentration c NOEC = no observed effect con centration (defined as the lowest concentration for which the effects were not statistically different from the controls) d Values provided in parentheses represent the data normalized to TFA, mg/L e At this concentration , the inhibition of the biomass int egral was 11%. Source: Boutonnet et al. 1999 In general, high conce ntration s of NaTFA ( ≥300 mg/L; ca. 250 mg TFA/L) did not result in adverse effects in the fish, crustacean, and diatom species tested, and most of the algal species tested. In duckweed, mild negative growth effects were seen on frond and weight increase at 600 mg/L; no effects were noted at 300 mg/L . Toxicity tests conducted with select species of algae shown above are taken from a study by Berends et al. (1999) who found that, for ten of the eleven species tested , the effect concentration for 50% of the test orga nisms ( EC 50 ) was >100 mg/L NaTFA (ca 84 mg TFA/L). The lowest threshold for effects w as observed for the unicellular alga , Pseudokirchneriella subcapitata (formerly S. capricornutum), which is commonly used as an indicator species in ecotoxicity screening tests . Toxicity

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6 results varied among the different labs testing P. subcapitata as reported by these authors (Berends et al. 1999); the authors state that responses at the low range of test concentrations were generally consistent, however, and they consi der 0.12 mg NaTFA/L (0.10 mg TFA/L) to be the threshold for toxicity (e.g., no effects on growth were noted at this concentration). However, at higher concentrations TFA did not have an algicidal effect, but rather an algistatic ( e.g., slowing growth ) effect on this species, as growth resumed three days after the TFA was removed (Berends et al. 1999). Environmental receptors in seasonal wetlands vary with geography, and are established in unique ecosystem niches. Plant species tend to be annuals, as peren nials are not adapted to the seasonality of the rainfall. Animal species, such as the f reshwater fairy shrimp ( Branchinecta lynchi) and tadpole shrimp ( Lepidurus packardi), which are found only in California, are obligate vernal pool species that define t hese wetlands. They are adapted to inconsistent levels of rainfall year to year, and varying pH and salinity gradients, and typically mature from egg to reproductive - age adult in a matter of weeks. As TFA exposure studies with these species are unavailabl e, there is no definite information regarding what, if any, effects increasing TFA concentrations would have on the life cycle of these niche organisms or others. Existing data on other similar organisms, however, indicate no cause for concern. Additiona l data taken from more recent articles relative to the toxicity of TFA in fish, aquatic plants, and freshwater benthic microbial communities are shown in Table 2 . They indicate that TFA exhibits low toxicity in these receptors. Table 2 : Summary of Additional Toxicity Studies of Trifluoroacetate (mg/L) Aquatic Organisms EC50/LC50 a LOEC b NOEC b Brachydanio rerio (Zebra fish) (Wiegand et al., 2000) --- 1,000 (1,200) c (low elevation of GST activity) 4,000 (4, 770)

(no acute effects) Myriophyllum sibiricum, Myriophyllum spicatum (aquatic plants) (exposure to trichloroacetic acid and TFA mixture for 49 days) (Hanson et al., 2002) --- --- 10 Lemna gibba, Myriophyllum sibiricum, Myriophyllum spicatum (aquati c plants [macrophytes]) (Hanson and Solomon, 2004a) EC 50 range: 222.1 - 10,000 (265 - 12,000) M. sib. : 300 (360)

M. spic. : 100 (120) L. gibba : 100 (120) M. sib. : 100 (120)

M. spic. : 30 (36) L. gibba : 30 (36) Pimephales promelas (Fathead minnow) (Geiger et al., 1988, as cited in ECOTOX) 7.79 - 1.28 (9.3 - 1.5) --- --- Freshwater benthic microbial communities in stream sediments (Bott and Standley, 1998)

--- --- 0.00002 to 0.2 (0.000024 to 0.24)(no effect on acetate metabolism) a EC50 = test concentration resulting in an effect in 50% of the organisms tested; the table lists EC50 for biomass integral (adverse effects on growth); LC50 = lethal concentration for 50% of the tested organisms b LOEC = lowest observed effect concentration; NOEC = no observed effect concentration c Glutathione S -transferase The combined impact of TFA and other haloacetic acids in the environment is unlikely to create a significant impact on exposed species. Hanson et al. (2002) tested two aquatic plant species with a mixture of trichloroacetic acid (TCA) and TFA at concentrations up to 10 mg/L, and observed reversible effects on pigment concentrations at the start of the study, but no adverse effects thereafter. The authors conclude that, based on the lack of morphological or bi ochemical effects on these aquatic macrophytes, it is unlikely that the TCA/TFA mixture causes toxicity at the currently measured

### TFA Assessment

7 environmental concentrations, which they report as 0.01 mg/L. Hanson and Solomon (2004a) tested the toxicity of TFA and other haloacetic acids (HAA) in the laboratory with three aquatic plants; mass and root measures, such as root number and root length, tended to be the most sensitive indicators of HAA toxicity. The results of this study were used in an ecological risk assessm ent for macrophytes (aquatic plants) and HAA (Hanson and Solomon, 2004b). The authors compare the thresholds of toxicity for the species tested to measured concentrations of HAAs in the environment from Canada, Europe, and Africa to calculate hazard quoti ents. The Hazard Quotient, as defined by Hanson and coworkers, is the ratio of the highest expected environmental concentration of HAA (EEC) and the toxicological benchmark concentration (TBC); HQ = EEC/TBC. An HQ of greater than 1 indicates a “potentia l for toxic effects to occur” while those less than 1 essentially indicate no risk (“effects are unlikely”). The calculated hazard quotients are extremely low (those for TFA with the three macrophytes were all ≤0.000088 or lower), indicating that HAAs do n ot pose a significant risk to freshwater macrophytes at current environmental concentrations for both single compound and mixture exposures. The thresholds for toxicity in these calculations ranged from 4.1 mg/L to 45.9 mg/L, concentrations which are 400 -4500 -fold greater than those currently detected in the environment (Cahill et al. 2001). Therefore, these data indicate that even in the event of increased environmental concentrations of TFA, which might result from increased use of HFO - 1234yf, the risk t o environmental receptors is expected to be small. The potential for bioconcentration in aquatic organisms is low (HSDB 2008), based on one classification scheme (Franke et al. 1994). An estimated bioconcentration factor (BCF) of 3 for TFA was calculated in fish, using an estimated log K ow of 0.50 (Meylan and Howard 1995) and a regression - derived equation (Meylan et al. 1999). Boutonnet et al. (1999) conclude that TFA does not accumulate significantly in lower aquatic life forms such as bacteria based on results from Bott and Standley (1994, as cited in Boutonnet et al. 1999) in which incorporation of radiolabeled TFA increased over 2.5 years from 0.005% of total counts to 0.024% of total counts , and based on low BCFs derived in studies with green algae ( BCF of approximately 10; van Dijk 1996, as cited in Boutonnet et al. 1999) and duckweed (BCF of 1.0 to 1.6; Smyth et al. 1993, as cited in Boutonnet et al., 1999) . As seasonal wetlands evaporate, TFA can remain in place and could concentrate over time, re sulting in long -term accumulation. However, vernal pools have varying levels of seepage due to lateral movement of sub - surface ground water flow, or because of weak or broken hardpans at the bottom of the pools (Sefchick et al. 1994, as quoted in Boutonnet et al. 1999; Hanes, 1998). TFA accumulation is not expected in pools exhibiting seepage. Of course, as these wetlands go dry, any TFA salt present would be adsorbed to soil particles on the ground surface, and would be subject to other transport mechanis ms, such as removal by wind, etc. Potential TFA accumulation may be linked to increased concentrations of TFA in plants in these wetlands, but again, plants in seasonal wetlands are heavily represented by annual grasses and similar species and TFA has be en shown not to affect seed production for future propagation in these ecosystems. Studies in animals following long -term exposure to TFA have not been done to date. In one study, t he highest TFA concentrations in water, which occurred just prior to the pools drying up, were in the 0.00 2 to 0.01 mg/L range . This concentration range is 10 - to 60 -fold lower than the lowest reported NOEC of 0.12 mg/L for the most sensitive species of freshwater green alga e ( P . subcapitata ). P lants exposed to high aqueous co ncentrations of TFA within the seasonal pools had elevated TFA concentrations with a median concentration of 279 ng/g dry weight in their tissues , as compared to 33 ng/g for species

### TFA Assessment

8 growing outside the pools (Cahill et al. 2001) . A study of the effects of TFA on vernal pool soil microbial and plant communities indicated that, at the test concentrations, TFA will not adversely affect the development of soil microbial communities and vernal pool plant species. Microbial respiration was not affected by TFA e xposures up to 10 mg/L, and microbial degradation of TFA was not observed in soils incubated for three months. In addition, no adverse physiological responses were observed in wetland plants exposed to 0.1 and 1 mg/L TFA. TFA did accumulate in the foliar tissue of wetland plants as a function of root exposure concentration, but the concentrations in foliar tissue leveled off and/or declined with time (Benesch et al. 2002). Thus, the test concentration of 1 mg/L is a NOEC for plant species in vernal pools. Studies of stomatal uptake in plants following dry deposition are limited. For TFA that is dry deposited, ponderosa pines were shown to take up TFA through their foliage (stomatal uptake) at concentrations of 0.0015 and 0.01 mg/L for four months (Benesch and Gustin 2002). The study authors prevented misted TFA from reaching the roots of the trees to ensure they evaluated only foliar uptake. Although TFA concentrations were shown to increase in the pine needles over the course of the study, no visual morp hological or photosynthetic effects were noted at either concentration. No NOEC values have been identified based solely on dry deposition of TFA, or on a combined wet/dry deposition model. In conclusion, NOECs from the published literature for the most s ensitive species were:  0.12 mg/L for freshwater green algae  1200 mg/L for a fish species  No observed adverse effects at up to 10 mg/L for vernal pool microbial species and up to 1 mg/L for vernal pool plant species Current risk assessments indicate that vernal pool species would not be negatively impacted with current and predicted published estimates of TFA loading in the environment. 

### 3.2. Human and Animal Toxicity TFA has low inhalation toxicity, moderate oral toxicity, and the irritation threshold for human s is 54 ppm (Boutonnet et al. 1999). The free acid is considered a strong skin and eye irritant. TFA is not significantly metabolized by mammals. The sodium salt of TFA (NaTFA) has a much lower toxicity than the free acid and will be the focus of this se ction, as the free acid is not likely to be present at high concentrations in environmental media. Animal studies show that the target organ of TFA and its sodium salt is the liver. Single doses of up to 2000 mg/kg NaTFA in male mice resulted in fatty liv er changes, accompanied by increases in glycogen and vacuolization (Rosenberg and Wahlstrom 1971, as cited in Boutonnet et al. 1999). Repeated oral dosing of male rats with NaTFA at up to 150 mg/kg - day resulted in significantly increased relative liver we ights with decreased liver glycogen content (Stier et al. 1972, as cited in Boutonnet et al. 1999), and doses of up to 500 mg/kg - day of trifluoroacetate caused increased liver cell size with peroxisomal proliferation (Just et al., 1989, as cited in Boutonn et et al.; 1999). The peroxisomal proliferation is unique to the rat, as this effect was not observed in dosed guinea pigs. Single doses of 10 mg/kg (ip) or 25 mg/kg (oral) TFA in male rats resulted in no adverse testicular effects. Neither TFA nor its salts have been studied in reproductive or developmental assays; TFA was present in the amniotic fluid of halothane - dosed pregnant rats, but no fetal effects were observed (Ghantous et al.

### TFA Assessment

9 1986, as cited in Boutonnet et al. 1999). TFA has also been ident ified in the milk of lactating rats (5 - 23% following saponification) after the administration of HCFC - 123 (Buschmann 1996, as cited in Boutonnet et al. 1999). TFA has also been reported to be non - mutagenic in bacterial studies (Blake et al. 1981 and Waskel l 1978, both cited in Boutonnet et al. 1999); studies have not been conducted to determine its carcinogenic potential.

### TFA Assessment

10 

## 4. Assessment of Potential HFO - 1234yf Emissions This analysis is intended as a screening exercise to develop a reasonable worst - case esti mate of HFO 1234yf emissions under various use scenarios. The remainder of this section describes the assumptions used for this analysis to determine potential emissions of HFO - 1234yf. A discussion on the limitations of the emission projections of HFO - 123 4yf can be found in section 6.1 of this paper. 

### 4.1. Scenarios of HFO - 1234yf Market Penetration For this analysis, two scenarios were developed. These scenarios provide reasonable worst - case assumptions for the potential market penetration of HFO - 1234yf in the domestic market only. Both scenarios assume that HFO - 1234yf is used as a drop - in replacement for HFC - 134a, 5 with a replacement ratio of 1:1 HFC - 134a to HFO - 1234yf. 6 The market penetration scenarios are described below and summarized in Table 3 .  Scenario 1: HFO - 1234yf is used in the United States as a new car refrigerant in the MVAC sector. HFO - 1234yf begins penetrating the market in 2016 reaching 100 percent market penetration by 2020, as described in Table 3 below.
 Scenario 2: HFO - 1234yf is used in the United States as a new car refrigerant in MVAC systems, refrigeration, and stationary AC systems. Similar to scenario 1, by 2020, HFO - 1234yf is used in all new MVAC systems. For refrigeration and stati onary AC systems, HFO - 1234yf enters the market in 2010, reaches 30 percent penetration of the market in 2015, and 100 percent by 2020. Table 3 : Summary of Assumed Penetration of HFO1234yf in Scenarios Used in Analysis*

Sectors 2010 2015 2020 Scenario 1 MVACs 0% 0 % 100% Scenario 2 MVACs 0% 0 % 100% Refrigeration 6% 30% 100% Stationary Air Conditioning 6% 30% 100% *The dates of introduction of HFO - 1234yf are consistent with the earlier analysis, conducted in 2009 and explained i n the foreword of this document . The specific dates of introduction are used as a demonstration of how HFO - 1234yf might be phased in; actual dates may differ by several years. Examining the period from initial introduction of the refrigerant to market saturation allows the analysis to consider potential impacts of HFO - 1234yf in the near-term (i.e., 10 - 15 years), during which time there are already specific State goals for ground - level ozone impacts. In addition, the analysis considers the potential l onger term impacts of HFO - 1234yf after the refrigerant has saturated the market, assuming continued growth in motor vehicle use.

5 In all scenarios, HFO - 1234yf replaces only pure HFC - 134a, not any blends with HFC - 134a as a component. 6 The ratio of HFC - 134a to HFO - 1234yf has been estimated at 1:0.9, however a 1:1 ratio was used to provide a worst case estimate .

### TFA Assessment

11 

### 4.2. HFO - 1234yf Emission Assumptions ICF assumed that emissions of HFO - 1234yf will be equivalent to emissions of HFC- 134a. Emissi on assumptions from the MVAC sector for this analysis are summarized below in Table 4 . Table 4 : Refrigerant Loss Assumptions from the MVAC Sector

Assumption Emissions Rate a Leak Rate 8% S ervicing Leaks (annualized) 10% End -of - life Loss Rate 42.5% a HFC - 134a MVAC assumptions from the U.S. EPA Vintaging Model, Version VM IO File v4.4_12 - 16 - 09 . Emissions of refrigerant due to servicing motor vehicle air conditioning systems were expecte d to be higher during the spring and summer, with up to 80% of emissions due to repairs occurring from April through August. 7 Furthermore, refrigerant emissions from servicing motor vehicle air conditioning systems were estimated at 47% of annual refrigerant emissions from motor vehicles. 8 As a result, the analysis assumes that 59.5% of annual emissions of HFO - 1234yf would occur from April through August, with 11.9% of annual emissions occurring during each of those five months. The remaining 40.5% of an nual emissions was modeled to occur from September through March, with 5.8% of annual emissions occurring during each of those seven months. This assumption was also applied to stationary AC end uses based on the assumption that similar patterns of season al emissions would be attributable to this end - use. 

### 4.3. Estimated Emissions of HFO - 1234yf Using EPA’s Vintaging Model, ICF estimated emissions of HFO - 1234yf for both scenarios. These estimates are summarized in Table 5 while estimate d monthly emission estimates of HFO - 1234yf for the year 2050 are provided in Table 6 . E stimated annual HFO - 1234yf emissions under each scenario are also graphically depict ed in Figure 1 and Figure 2. A complete table with estima ted annual emissions can be found in Annex A. Table 5 : Summary of Estimated Emissions of HFO - 1234yf (MT)* Scenarios 20 20 20 3 0 2040 20 5 0 Scenario 1 6,244 28,327 33,093 35,851 Scenario 2 10,501 43,296 55,070 60,616 * ICF projecte d emissions of HFO - 1234yf using special scenarios designed specifically for this analysis and run on the U.S. EPA Vintaging Model, Version VM IO File v4.4_12 - 16 - 09 . Table 6 : Summary of Estimated Monthly Emissions of HFO - 1234yf i n 2050 (MT) Scenarios Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Scenario 1 2,074 2,074 2,074 4,266 4,266 4,266 4,266 4,266 2,074 2,074 2,074 2,074 Scenario 2 4,025 4,025 4,025 6,489 6,489 6,489 6,489 6,489 4,025 4,025 4,025 4,025

7 Hoffpauir, Elvis. 2009. Email to Karen Thundiyil, 10 March. 8 U.S. EPA Vintaging Model, Version VM IO File v4.2 10 - 07 - 08

### TFA Assessment

12 Figure 1 : Estimated Emission s of HFO - 1234yf by End - Use Sector under Scenario 1 (MT)

Figure 2 : Estimated Emissions of HFO - 1234yf by End - Use Sector under Scenario 2 (MT)

### TFA Assessment

13 

## 5. Assessment of Potential Impacts of HFO - 1234yf and TFA This section uses the projected emissions of HFO - 1234yf described in section 4 to predict impacts on aquatic communities, soil s and plants, and local air quality. Emissions from each scenario for the ye ar 2050 were scaled from the national emissions estimates according to population for Houston and Los Angles regions to determine reasonable worst - case impacts. These regions were chosen based on the potential presence of vernal pools, their susceptibility to high TFA deposition concentrations, and their continuin g and chronic problem with high levels of ground level ozone. Using EPA’s CMAQ model version 4.7, a one -year simulation was performed using 2001 meteorological data to project maximum monthly TFA rainwater concentrations, monthly maximum dry deposition of TFA, and maximum 8 - hr ozone concentrations for the Los Angeles and Houston regions resulting from emissions of HFO - 1234yf from those regions only. The model used the extended version of the carbo n bond five chemical mechanism as developed by Luecken et al. (2010), which incorporates the gaseous and aqueous chemistry of HFO - 1234yf and its products. The results from this analysis are described in the remainder of this section. 

### 5.1. TFA Rainwater Concent rations Monthly maximum average TFA rainwater concentrations for each region under each scenario are summarized in Table 7 . Table 7 : Summary of Estimated Monthly Average TFA Rainwater Concentrations in 205 0 ( ng/L) Region Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Scenario 1 Los Angeles 90 32 166 167. 96 9 111 6 707 944 170 120 196 94 Houston 1 8 2 1 3 2 34 50 75 106 5 9 54 19 1 6 2 7 Scenario 2 Los Angeles 174 63 322 322 1475 1700 1077 1438 319 232 380 18 2 Houston 35 40 61 51 76 114 161 90 85 37 30 51 Under scenario 1, t he results indicate that the maximum monthly average TFA rainwater concentration in the Los Angeles region in 2050 is 1,11 6 ng/L, while the maximum monthly average TFA rainwater concentr ation in the Houston region in 2050 is 10 6 ng/L. Under scenario 2, t he results indicate that the maximum monthly average TFA rainwater concentration in the Los Angeles region in 2050 is 1,700 ng/L, while the maximum monthly average TFA rainwater concentra tion in the Houston region in 2050 is 161 ng/L. For Los Angeles, June represents the month with the highest projected monthly average TFA rainwater concentration, while for Houston, July represents the month with the highest projected monthly average TFA rainwater concentration. The monthly average maximum TFA rainwater concentrations for these two peak months are geographically depicted below in Figure 3 and Figure 4, for both scenarios, for Los Angeles and Houston, respectively.

### TFA Assessment

14 Figure 3 : June 2050 Los Angeles Scenario 1 and Scenario 2 Results

Figure 4 : July 2050 Houston Scenario 1 and Scenario 2 Results



### 5.2. TFA Dry Deposition Table 8 presents the results of both the maximum annual and monthly maximum TFA deposition expressed on an annual basis . Table 8 : Summar

y of Estimated TFA Dry Deposition in 2050

Notes: Formula weight of TFA is 114 g/mole. a Maximum concentration occurred in May for Los Angeles and in July for Houston. Results are expressed on annual basis using the peak monthl y deposition rate times 12. Annualized TFA Maximum Monthly Average Flux Rate a TFA Maximum Annual Average Flux Rate nmole/m 2 -yr g/m2 -yr nmole/m 2 -yr g/m2 -yr Scenario 1 Los Angeles 15,252 566 3 , 838 143 Houston 2 , 556 95 934 35 Scenario 2 Los Angeles 23 , 232 863 6 , 393 237 Houston 3 , 912 145 1 , 551 58

### TFA Assessment

15 Dry deposition of TFA is likely more of a concern in central and southern California than is wet deposition due to the lower rainfall in th is part of th e state compared to other geographical areas of the United States. For com parison , measured TFA flux rates from two vernal pool systems outside of Sacramento, California are presented in Table 9 (Cahill et al. 2001; data taken in 1998 and 1999). Table 9 : TFA Measurements in Cali fornia Vernal Pools, 1998 - 1999 Observed Year Flux Rate Values Measured in California Vernal P ools ng/m 2 -day g/m 2 -yr 1998 - 1999 134* 49 1998 - 1999 110** 40 1998 - 1999 152*** 5 6 Notes: Values of g/m2 -yr = ng/m2 - day * 365 days/1000 . *Time -weighted avera ge of values measured in Davis, CA Jan 1 - May 16, 1998. **Time - weighted average of values measured in Davis, CA Nov 26, 1998 -Apr 2, 1999. ***Time -weighted average of values measured in Yolo Country Grasslands Regional Park, CA Jan 6 - May 6, 1999. The values above indicate that projected maximum annual average deposition of TFA will be somewhat greater than what has been measured in vernal pools in the last decade in Northern California. For S outhern California , measured values in vernal pools would be expected to be somewhat higher than those reported owing to the reduced rainfall compared to Northern California . 

### 5.3. Ground Level Ozone Concentrations Under scenario 1, results for the Los Angeles region show a maximum increase in the 8 - hr ozone concentration of 0.053 ppb, while results for the Houston region show a maximum increase in the 8 - hr ozone concentration of 0.014 ppb. Under scenario 2, results for the Los Angeles region show a maximum increase in the 8 - hr ozone concentration of 0.080 ppb, while results for the Houston region show a maximum increase in the 8 - hr ozone concentration of 0.021 ppb. Maximum increases in 8 - hr ozone concentrations under each scenario are geographically depicted in Figure 5 and

### TFA Assessment

16 Figure 6 below . Figure 5 : LA May 22, 2050 Scenario 1 and Scenario 2 Results

### TFA Assessment

17 Figure 6 : Houston June 11, 2050 Scenario 1 and Scenario 2 Results

Figure 5 : LA May 22, 2050 Scenario 1 and Scenario 2 Results

### TFA Assessment

18 Figure 6 : Houston June 11, 2050 Scenario 1 and Scenario 2 Results



## 6. Discussion of Results The following section provides a summary of the findings described in section 5 and additionally provides an overview of the limitations of this analysis. In section 3.1 of this paper, based on available studies, it was concluded that the NOEC is 0.12 mg/L (120,000 ng/L) for freshwater green algae, 10 mg/L (10,000,000 ng/L) for vernal pool microbial species, and 1 mg/L (1,000,000 ng/L) for vernal pool plant species. Relative to these levels, in the worst case scenario, TFA rainwater concentrations are expected to reach 1,11 6 ng/L in 2050, well below the NOEC of 1,000,000 ng/L for vernal pool species. The measured concentration of TFA in rainwater is only ten times greater than t he 2020 level of TFA in rainwater projected from the current rate of production from atmospheric degradation of HFCs and HCFCs, which is estimated to be almost 0.0001 mg/L or 100 ng/L (Berends et al. 1999) , but still 1,000 times lower than the NOEC for te sted vernal pool species. NOECs are compared to rainwater TFA concentrations because for most water bodies, it is difficult to predict what the actual TFA concentration will be. This is because concentrations of environmental contaminants in most fresh water bodies fluctuate widely due to varying inputs and outputs to most ponds, lakes, and streams. Comparison of NOECs to rainwater concentrations of TFA is actually more conservative because TFA is expected to be diluted in most freshwater bodies. The exception to this is that less dilution is expected in vernal pools and similar seasonal water bodies that have no significant outflow capacity. Although dry deposition of TFA in vernal pools has been projected to potentially be almost five times greate r than concentrations measured in 1998 - 1999, studies indicate that vernal pools species are unlikely to be harmed because plant and animal species tested to date do not bioconcentrate TFA and the compound has not been shown to affect plant germination rate s . It is noted that no NOEC values have been identified based solely on dry deposition of TFA, or on a combined wet/dry deposition model , but it is not expected that there will be adverse impacts based on the lack of reported bioconcentration and germinat ion effects .

### TFA Assessment

19 In regards to ground level ozone formation, based on the findings described in section 5.3 and a ssuming an 8 - hr ozone standard of 75 ppb, HFO - 1234yf is projected to contribute to a maximum of roughly 0.07 % - 0.1% and 0.02 % - 0.03% of total ground - level ozone in Los Angeles and Houston, respectively. These percentage increases are presented relative to the proposed 75 ppb standard for ozone, although it is unclear what the standard will be in the future with possible changes in standards for emissions of criteria pollutants, VOCs, and NO x . 

### 6.1. Summary of Findings Based on results presented above, certain preliminary conclusions concerning the potential impacts of HFO - 1234yf and the associated production of TFA can be made:
 Projected levels of T

FA in rainwater should not result in a significant risk of ecotoxicity. After taking into account the nature of HFO - 1234yf degradation and the resulting TFA concentration in rainwater; regional precipitation patterns; the geology of closed aquatic systems ; and no observed effect concentrations (NOEC) for TFA, TFA production resulting from HFO - 1234yf emissions is not expected to pose significant harm to aquatic communities in the near future. Future research is necessary to determine if significant TFA load ing is occurring in vernal pools near major population centers as there are insufficient data to determine whether TFA would impact these environments significantly.

 Dry deposition is a potential concern; however, more research is needed to fully understand the impacts of dry deposition on soil, plants, and aquatic communities. Only two studies were identified which investigated the effects of dry deposition in plants. While one study showed measured effects on photosynthesis, the other did not. It is un clear what impact current and future loading of TFA will have in vernal pool ecosystems. Current tests on freshwater plants and animal species that might be found in vernal pools show that only one species of algae might be affected at predicted concentra tions of deposited TFA. Howe ver, it is not possible to know without further research, whether increased TFA loading might affect other obligate vernal pool species. Current risk assessments, though, indicate this is not a significant concern.

 Non -attai

nment resulting from HFO-1234yf emissions is not likely to be a concern for local air quality in all locations. HFO - 1234yf could potentially increase ground level ozone by up to 0.1% in the most extreme case. Given the expected photochemical reactivity o f HFO - 1234yf, emissions of HFO - 1234yf are not expected to significantly result in ground level ozone formation. 

### 6.2. Limitations of this Analysis The analysis described above is based on numerous assumptions and projections that cannot be known with certainty at this time. The following discussion recognizes these uncertainties and indicates various factors that have potential to impact and change the results of this analysis. 

### Market Modeling
 The market penetration assumptions used for this analysis assume HF O - 1234yf will be the sole replacement for HFC - 134a. However, the introduction of additional substitutes could

### TFA Assessment

20 potentially lower the penetration of HFO - 1234yf into the market, thus decreasing the emissions and impacts of HFO - 1234yf and TFA.
 Even though EP A’s Vintaging Model, used to calculate emissions for both scenarios, provides output up to 2050, the assumptions used in the model are based only on current data and expert opinions regarding the near future. Since it is not possible to predict with certa inty changes that will occur in the distant future (post 2020), the assumptions in the model are not adjusted for additional unpredictable cha nges that will likely take place.
 EPA’s Vintaging Model does not account for reductions in emissions that may occu r as a result of using HFO - 1234yf as a replacement for HFC - 134a. Factors such as refrigerant price and advancements in leak-tightness of MVAC systems are not adjusted for in the modeling. Consequently, HFO - 1234yf emission projections are considered to be conservative. 

### Aquatic and Soil Impacts
 A significant source of uncertainty in the analysis of aquatic toxicity is the receptor species used in the analysis. For example, in the cited studies, researchers used widely accepted and standardized species of f reshwater and marine flora and fauna in the screening tests. These plant and animal species, however, with the possible exception of Daphnia magna, and some alga l species, are not typical of specialized vernal pool species in California such as meadow foa m, Downingia, Navarettia, fairy shrimp, tadpole shrimp, and tiger salamanders. Of course, one reason for this is that many of these species are endangered and/or protected, and it is not possible to conduct toxicity studies on them. Nevertheless, lack of knowledge regarding the susceptibility and/or resistance to TFA or similar compounds by these species affects the ability to more accurately quantify aquatic impacts from TFA deposition in certain geographical areas. However, one study (Benesch et al. 200 2) did look at vernal pool microbial and plant species and found that predicted TFA concentrations would not adversely affect these receptors. Further, current and predicted TFA concentrations are well below effect levels in many related ecological recept ors, and lower aquatic life forms do not bioconcentrate TFA. These data indicate that despite full knowledge of the effects of TFA on vernal pool species, adverse ecological effects are not anticipated.
 T he ecology considered in this analysis is a highly specialized one that is vital to many species, including migratory birds. In addition, regional areas that contain the geology necessary for vernal pool formation are subject to modification via many means, including residential and commercial development, mining, agriculture, and in California, earthquakes. These activities also produce environmental contamination that affects species adapted to vernal pool ecology. It is not possible to predict the impact of these external effects on aquatic toxicity o f vernal pools, nor how TFA concentrations, in concert with these other effects, might change the estimated results presented here. 

### Air Quality
 Improvements in the understanding of the reactivity of HFO - 1234yf and resulting production of TFA and ozone for mation have potential to change the estimates made in this analysis.

### TFA Assessment

21  Further global warming impacts will result in region - specific changes that may, for example , increase local cloud cover leading to decreases in local photolysis rates resulting in reduce d ozone production.
 The changes in standards for other pollutants such as air toxics or criteria pollutants could affect the precursor ozone emissions. For example, EPA recently finalized a rule for a new 1 - hour NO 2 standard in the range between 80 to 100 ppb. In order to meet future standard s , significant emission reductions may be required, thus impacting the potential production of ground level ozone.  The ozone air quality standard may be lowered in the future (historically the standard has been lowere d a number of times) and would require additional reductions of ozone precursor emissions, which would increase the importance of HFO - 1234yf to the production rate for ozone.

### TFA Assessment

22 

## 7. References 1234yf OEM Group. 2008. MAC Summit 2008. Available at < http://www.e pa.gov/cppd/mac/HFO1234YF%20EXPERT%20CONSENSUS%20GROUP.ppt > Abstracts : South African Association of Botanists – Annual meeting 2006 . South African Journal of Botany 72 : 313 - 347 Benesch JA, MS Gustin, GR Cramer, and TM Cahill. 2002. Investigation of effects of trifluoroacetate on vernal pool ecosystems. Environ Toxicol and Chem . 21(3):640 -47. Berends, AG, JC Boutonnet, C de Rooij, and RS Thompson. 1999. Toxicity of Trifluoroacetate to Aquatic Systems. Environ Toxicol Chem . 18(5): 1053 – 1059 . Bott, TL and LJ Standley. 1994. The effect of TFA on biological processes in streams. Proceedings of a Workshop on the Enviornmental Fate of Trifluoroacetic Acid. March 3 -4, 1994, Miami Beach, FL. Published by AFEAS, Washington, DC. Cited in Boutonnet et al., 1999. B ott, TL and LJ Standley. 1998. Effects of trifluoroacetate, and atmospheric breakdown product of hydrofluorocarbon refrigerants, on acetate metabolism by freshwater benthic microbial communities. Bull. Environ. Contam. Toxicol. 60(3):472 - 79. Bott, TL an d LJ Standley. 1999. Incorporation of trifluoroacetate, a hydrofluorocarbon decomposition byproduct, by freshwater benthic microbial communities. Water Research. 33(6):1538 -44. Boutonnet, JC, P Bingham, D Calamari, C de Rooij, J Franklin, T Kawano, J - M Libre, A McCulloch, G Malinverno, JM Odom, GM Rusch, K Smythe, I Sobolev, R Thompson, and JM Tiedje. 1999 . Environmental Risk Ass essment of Trifluoroacetic Acid. Human Ecolog Risk Assessment. 5(1) : 59 - 124 . Bowden DJ, SL Clegg, andP Brimblecombe. 1996. The Henry’s Law constant of trifluoroacetic acid and its partitioning into liquid water in the atmosphere. Chemosphere . 32(2):405 -420. Bowden DJ, SL Clegg, and P Brimblecombe. 1998. The Henry’s law constant of the haloacetic acids. J. Atmos. Chem 29 (1) :85 - 107 . Byun, DW and JKS Ching. 1999. Science Algorithms of the EPA Models - 3 Community Multiscale Air Quality (CMAQ) Modeling System. U.S. EPA Office of Research and Development, Washington, D.C. (EPA/600/R - 99/030). Cahill, TM, TM Carmen, SE Schwarzbach , and JN Seiber. 2001. Accumulation of Trifluoroacetate in Seasonal Wetlands in California. Environ Sci & Tech . 35(5 ): 820–825 . Carter, W.P.L., 2009. Investigation of atmospheric ozone impacts of trans 2,3,3,3 -tetrafluoropropene, Final Report, availabl e at http://www.cert.ucr.edu/~carter/pubs/YFrept.pdf . ECOTOX Database, USEPA/ORD/NHEERL, accessed July, 2008.

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23 Ellis, DA, ML Hanson, PK Sibley, T Shahid, NA Fineberg, KR Solomon, DCG Muir, an d SA Mabury. 2001. The fate and persistence of trifluoroacetic and chloroacetic acids in pond waters. Chemosphere . 42(3):309 - 318. Emptage, M., Tabinowski, J.A., and Odom, J.M. 1997. The effect of fluoroacetates on methanogenesis in samples from selected methanogenic environments. Environ. Sci. Technol. 31 : 732–734. Environmental Protection Agency. Accessed May 2009. Classifications of 8 - Hour Ozone Nonattainment Areas. Last Updated March 12, 2009. Available at < http://www.epa.gov/air/oaqps/greenbk/gnc.html > Environmental Protection Agency’s Vintaging Model, Version VM IO File v4. 4_12 - 16 - 09 Franke C, G Studinger, G Berger, S Böhling, U Bruckmann, D Cohors - Fresenborg, U Jöhnckeas. 1994. The ass essment of bioaccumulation. Chemosphere 29(7):1501 - 14, as cited in HSDB, accessed July, 2008. Franklin J. 1993. The atmospheric degradation and impact of 1,1,1,2 -tetrafluoroethane (Hydrofluorocarbon 134a). Chemosphere 27(8): 1565 - 1601. Geiger et al., 1 988. Acute Toxicities of Organic Chemicals to Fathead Minnows ( Pimephales promelas ) Volume IV. Ctr. f

or Lake Superior Environ. Studies, Vol 4, U. of Wisconsin - Superior, Superior, WI; 355, as cited in ECOTOX, accessed July, 2008. Hanes T. 1998. Hydrology of vernal pools on non -volcanic soils in the Sacramento Valley. Available online at <http://www.vernalpools.org/proceedings/hanes.pdf>. Hanson ML and KR Solomon. 2004 a . Haloacetic acids i n the aquatic environment. Part I: Macrophyte Toxicity. Environ. Pollution 130(3):371 - 383. Hanson ML and KR Solomon. 2004 b . Haloacetic acids in the aquatic environment. Part II: Ecological Risk Assessment. Environ. Pollution 130(3):385 -401. Hanson ML, P K Sibley, SA Mabury, KR Solomon and DC Muir. 2002. Trichloracetic acid (TCA) and trifluoracetic acid (TFA) mixture toxicity to the macrophytes Myriophyllum spicatum and Myriophyllum sibiricum on aquatic microcosms. Sci. Total Environ . 285(1 - 3):247 - 59. Ha nson ML, PK Sibley, TM Boudreau, J Small, SA Mabury, KR Solomon and RA Brain. 2005 . Microcosm evaluation of the toxicity and risk to aquatic macrophytes from perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). Available at < http://www .chem.utoronto.ca/symposium/fluoros/pdfs/TOX001Hanson.pdf> Hazardous Substance Data Bank. Accessed July 2008. Available at < http://toxnet.nlm.nih.gov/cgi bin/sis/htmlgen?HSDB >. Intergovernmental Panel on Climate Change (IPCC). 2007. IPCC Fourth Assessment Report: Climate Change 2007. Available at < http://www.ipcc.ch/ipccreports/assessments - reports.htm >. Intergovernmental Panel on Climate Change (IPCC)/Technology and Economic Assessment Panel (TEAP). 2005. IPCC/TEAP Special Report: Safeguarding the Ozone Layer and the Global Climate System: Issues

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24 related to hyrdofluorocarbons and perfluorocarbons. Available at < http://www.ipcc.ch/pdf/special reports/sroc/sroc_full.pdf>. Intergovernmental Panel on Climate Change (IPCC). 1996. IPCC Second Assessment - Clima te Change 1995. Available at < http://www.ipcc.ch/ipccreports/assessments - reports.htm > . Javadi, M.S., Sondergaard, R. Nielsen O.J., Hurley M.D., Wallington T.J. 2008. Atmospheric chemistry of trans - CF3CH=CHR: products and mechanisms of hydroxyl radical and chlorine atom initiated oxidation. Atmos. Chem. Phys. Discuss ., 8:1069 - 1088 Kim BR, MT Suidan, TJ Wallington, et al. 2000. Biodegradability of trifluoroacetic acid. Env Eng Science 17:337 - 342. Kotamarthi, VR, JM Rodriguez , MKW Ko, TK Tromp, ND Sze and MJ Prather. 1998. Trifluoroacetic acid from degradation of HCFCs and HFCs: A three - dimensional modeling study. J Geophys Research. 103(D5):5747 - 5758. Likens, GE, SL Tartowski, TW Berger, DG Richey, CT Driscoll, HG Frank, and A Klein. 1997. Transport and fate of trifluoroacetate in upland forest and wetland ecosystems. Proc. Natl Acad. Sci. USA 94(9):4499 - 4503. Lohmann, U, K Von Salzen, N McFarlane, H Leighton, and J Feichter. 1999. Tropospheric sulfur cycle in the Canadian general circulation model, J Ge ophysical Research 104(D21):26,883 - 26,858. Luecken, D.J., Waterland, R.L., Papasavva, S., Taddonio, K.N., Hutzell, W.T., Rugh, J.P., Andersen, S.O. 20 10 . Ozone and TFA Impacts in North America from the Degradation of 2,3,3,3 -Tetrafluoropropene (HFO - 1234yf), A Potential Greenhouse Gas Replacement. Environ. Sci. Technol. 44(1): 343 - 348. MACS. 2009. Email communication between Elvis Hoffpauir, MACS and Karen Thundiyil, EPA. 10 March. Meylan WM, and PH Howard. 1995. Atom/fragment contribution method for estimating octanol - water partition coefficients. J. Pharm . Sci. 84(1):83 - 92, as cited in HSDB, accessed July, 2008. Meylan WM, PH Howard, RS Boethling, D Aronson, H Printup, and S Gouchie. 1999. Improved method for estimating bioconcentration/bioaccumulatio n factor from octanol/water partition coefficient. Environ. Toxicol. Chem. 18(4):664 - 672, as cited in HSDB, 2008 . Niels e n, O.J., Javadi, M.S., Sulbaek Andersen, M.P., Hurley, M.D., Wallington, T.J., Singh, R. 2007. Atmospheric chemistry of CF 3 CF=CH 2 : Kinet ics and mechanisms of gas - phase reactions with Cl atoms, OH radicals, and O 3 . Chemical Physics Letters 439, 18 - 22. Papadimitriou, V, RK Talukdar , RW Portmann, AR Ravishankara, and JB Burkholder. 2008. CF3CF=CH2 and (Z) - CF3CF=CHF: temperature dependent OH rate coefficients and global warming potentials. Physical Chemistry Chemical Physics . 10(6):808 - 20. Papasavva, S, DJ Luecken, RL Waterland, KN Taddonio, and SO Andersen. 2009. Estimated 2017 Refrigerant Emissions of 2,3,3,3 -tetrafluoropropene (HFC - 1234yf) in the United States Resulting from Automobile Air Conditioning. Environ. Sci. Technol. 43(24): 9252 - 9259.

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25 Richey DG, CT Driscoll, and GE Likens. 1997. Soil retention of trifluoroacetate. Environ. Sci. Tech. 31 (6) :1723 - 1727. Texas Natural Resource Conserv ation Commission. 2000. Post - 1999 Rate - of- Progress and Attainment Demonstration SIP for the Houston/Galveston Ozone Nonattainment Area , August 2000. Sefchick J, J Skorupa , and S Schwarzbach. 1994. Review of evaporative concentration potential of conserva tive solutes in selected wetland systems. Final Report to AFEAS by US Fish and Wildlife Service (SP91 - 18.6/BP93 - 22) (as quoted in Boutonnet et al. 1999). S m yth , D. V ., T h omp s o n , R . S ., an d G illi n g s , E . 1993. S od i um t r i f l uo ro a c e tat e : To xici ty t o th e du c kw eed ( Le m na g i bb a ) . B r ix ha m E n v i r o n me nta l La bo r at o ry R epo rt B L4872 / B (as cited in Boutonnet et al. 1999) . South Coast, 2007 Final 2007 AQMP, Appendix V, Modeling and Attainment Demonstrations, June 2007. Available at http://www.aqmd.gov/aqmp/07aqmp/index.html . Subcommittee on Reproductive and Developmental Toxicity, Committee on Toxicology, Board on Environmental Studies and Toxicology, and National Research Council. 2001. Evaluating Chemical and Oth er Agent Exposures for Reproductive and Developmental Toxicity. National Academy of Sciences. Washington, D.C. Tromp, TK, MKW Ko, JM Rodriguez, and ND Sze. 1995. Potential accumulation of a CFC - replacement degradation product in seasonal wetlands. Nature 3 76: 327 - 330. UNEP. 2006. Environmental Effects of Ozone Depletion and its Interactions with Climate Change: 2006 Assessment. United Nations Environment Programme. Nairobi, Kenya. V an Dij k, N . R . M . 1996. P o ss i b l e b i o t r an sfo r m at i o n o f s od i um t r i f l uo ro a c e tat e b y th e a lg a S e l e na str u m c a p r i co r nu t u m . S o l v a y D up ha r R epo rt 56834/ 13/96 (as cited in Boutonnet et al. 1999). Wiegand C, S Pflugmacher, M Giese, H Frank, and C Steinberg. 2000. Uptake, toxicity, and effects on detoxication enzymes of atrazine and tril uoroacetate in embryos of zebrafish. Ecotox. Environ . Saf . 45(2):122 - 31. Wujcik, CE, TM Cahill, and JN Seiber. 1999. Determination of Trifluoroacetic Acid in 1996 - 1997 Precipitation and Surface Waters in California and Nevada. Environ. Sci. Tech. 33(10):1 747 - 1751. Zhang, L, JR Brook, and R Vet. 2003. A revised parameterization for gaseous dry d eposition in air- quality models. Atmos. Chem. Phys. 3: 2067–2082.

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26 

## Annex A: Annual HFO - 1234yf Emissions Estimated under each Scenario for the Years 2010 through 205 0 (MT)* Year Scenario 1 Scenario 2

MVACs MVACs Refrigeration Stationary AC TOTAL 2010 - - 39 7 46 2011 - - 111 20 132 2012 - - 218 40 258 2013 - - 361 66 426 2014 - - 541 98 640 2015 - - 762 138 900 2016 407 407 1,093 196 1,696 2017 1,229 1,229 1, 541 273 3,043 2018 2,472 2,472 2,110 369 4,951 2019 4,143 4,143 2,807 485 7,435 2020 6,244 6,244 3,636 620 10,501 2021 8,332 8,332 4,487 766 13,585 2022 10,413 10,413 5,389 916 16,718 2023 12,513 12,513 6,278 1,066 19,857 2024 14,644 14,644 7,209 1, 216 23,069 2025 16,812 16,812 8,128 1,367 26,307 2026 19,003 19,003 9,043 1,516 29,561 2027 21,203 21,203 9,953 1,678 32,834 2028 23,962 23,962 10,914 1,848 36,724 2029 26,335 26,335 11,817 2,017 40,170 2030 28,327 28,327 12,748 2,221 43,296 2031 29 ,926 29,926 13,591 2,412 45,929 2032 31,118 31,118 14,348 2,577 48,043 2033 31,295 31,295 14,918 2,720 48,932 2034 31,514 31,514 15,479 2,861 49,854 2035 31,791 31,791 15,924 3,010 50,725 2036 32,084 32,084 16,382 3,213 51,678 2037 32,374 32,374 16,8 24 3,408 52,606 2038 32,627 32,627 17,249 3,592 53,468 2039 32,857 32,857 17,656 3,767 54,280 2040 33,093 33,093 18,046 3,931 55,070 2041 33,345 33,345 18,371 4,008 55,724 2042 33,637 33,637 18,668 4,080 56,385 2043 33,906 33,906 18,921 4,151 56,977 2044 34,177 34,177 19,156 4,217 57,549 2045 34,450 34,450 19,374 4,278 58,102 2046 34,726 34,726 19,566 4,315 58,606 2047 35,004 35,004 19,756 4,351 59,110 2048 35,284 35,284 19,944 4,383 59,611 2049 35,566 35,566 20,132 4,415 60,112 2050 35,851 35, 851 20,318 4,447 60,616 * ICF projected emissions of HFO - 1234yf using special scenarios designed specifically for this analysis and run on the U.S. EPA Vintaging Model, Version VM IO file v4.4_12 - 16 - 09 .