### MEMORANDUM

To: Margaret Sheppard, U.S. EPA Cc: Rebecca von dem Hagen and Bella Maranion, U.S. EPA From: Emily Golla, Ed Carr, and Mark Wagner , ICF International Date: January 7 , 201 5 Re: Potential i mpacts of 

### trifluoroacetic acid (TFA) generated from HFC

- 32 in room air conditioners (EPA Contract Number EP

- W

- 10

- 031 Task Order 405 , Task 1 ) In 2010, ICF conducted an analysis that examined the production of TFA associated with emissions of HFO

- 1234yf under several scenarios

. 1 Under the worst

- case scenario , it was assumed that HFO

- 1234yf will be used in the United States as a new car refrigerant in all new motor vehicle air conditioning ( MVAC ) systems, refrigeration, and stationary air conditioning systems by 2020. Even under the worst case scenario, the analysis concluded that the generation of TFA from the projected emissions of HFO

1234yf should not result in a significant risk to aquatic communities, soil and plants, or local air quality. In 2014, EPA proposed to list HFC

- 32 as acceptable for use in room air conditioning units. The remainder of this memorandum discusses the atmospheric breakdown of HFC

- 32 in the atmosphere and the estimated amount of TFA to be generat ed by the breakdown of HFC

- 32 as well as other refrigerants used in room air conditioners (i.e., HCFC

- 22, HFC

- 134a, and R

- 410A (a blend of 50% HFC

- 32 and 50% HFC

- 125 ) ) , and concludes that the resulting level of TFA is not expected to be harmful to a quatic communities, soil and plants, or local air quality . This discussion takes into account the analysis conducted in 2010 on the potential impact TFA generated from emissions of HFO

- 1234yf on aquatic life. Please contact Mark Wagner (202

- 862

- 1 155 ) with any questions.

1 The analysis

— Asses sment of the Potential Impacts of HFO

- 1234yf and the Associated Production of TFA on Aquatic Communities, Soil and Plants, and Local Air Quality

— was conducted in support of the Significant New Alternatives Policy (SNAP) Program rule on the use of HFO

- 1234yf as a new substitute for motor vehicle air conditioning.1 

## Atmospheric Degradation of Relevant Refrigerants Hydroflurocarbons (e.g., HFC

- 32 , HFC

- 125 , and HFC

- 134a) as well as h ydro chloro fluorocarbons (e.g., H C FC

- 22 ) undergo atmospheric degradation reac tions via numerous pathways including oxidation with chlorine atoms and hydroxyl (OH) radicals; however interaction with OH radicals is the predominant degradation reaction. The chemical degradation pathway is complex and includes numerous radical species and short

- lived intermediates. The most prevalent, stable, and toxicologically relevant to human health end

- products are summarized below. 

### Atmospheric Breakdown of HCFC
- 22 The major atmospheric oxidation product of H C F C

- 2 2 ( CHClF2) is carbonyl fluoride (COF2) and is the only carbon containing product formed (Tuazon and Atkinson 1993). COF 2 is rapidly hydrolyzed in the presence of water to form HF (hydrogen fluoride) and CO 2 (carbon dioxide). The only other degradation product found in s tudies of transformation products was HCl (hydrogen chloride)

. 

### Atmospheric Breakdown of HFC
- 134a The major atmospheric oxidation products of HF C

- 134a are carbonyl fluoride ( COF 2 ) , CF 3 CO F , formyl fluoride ( HCOF), and HCOOH (Kotamarthi et al., 1998). C O F 2 is rap idly hydrolyzed in the presence of water to form HF (hydrogen fluoride) and CO 2 (carbon dioxide). In addition, HCOF decomposes at room temperature to form HF and CO

. 

### Atmospheric Breakdown of H FC - 125 The major atmospheric oxidation product for HFC

- 125 is through interaction with the hydroxyl (OH) radical to form COF 2 and CF 3 OH (trifluoromethanol) (O’Doherty et al., 20009). The CF 3 OH is hydrolyzed with ammonia or water, with ammonia being the much faster reaction, forming COF 2 . The COF 2 is rapidly hydro lyzed in the presence of water to form HF (hydrogen fluoride) and CO 2 (carbon dioxide). 

### Atmospheric Breakdown of HFC
- 32 The major atmospheric oxidation product for HFC

- 32 is through interaction with the hydroxyl (OH) radical to form CHF 2 O radical and water (Wellington and Nielsen 1999) . The CHF 2 O radical then reacts rapidly with oxygen to form COF 2 which is rapidly hydrolyzed in the presence of water to form HF (hydrogen fluoride) and CO 2 (carbon dioxide). In no studies has the formation of CF 3 COOH (TF A) been observed. 

## Generation of TFA from Refrigerants Used in Room Air Conditioners
As discussed above , literature to dat e has not shown an atmospheric pathway in which HFC

- 32 degrades into TFA

. Error! Reference source not found. below summarizes the degradation products formed from the use of H FC

- 32 and other commonly used refrigerants in room air conditioners

. The degradation products of HFO

- 1234yf are also presented for r eference.2 Table 1 : Comparison of Atmospheric Degradation Products initiated by OH Compound HCFC - 22 HFC - 134a HFC - 125 HFC - 32 HFO - 1234yf Formula CHClF 2 CF 3 CH 2 F C 2 HF 5 CH 2 F 2 CF 3 CF=CH 2 IUPAC name chlorodifluoromethane 1,1,1,2

- tetrafluoroethane 1,1,1,2,2

- pentafluoroethane difluoromethane 2,3,3,3

- tetrafluoropropene Atmospheric lifetime 12 years (a) 14.4 years 29 years (a) 4.9 years (a) 11 days k (OH + HFC or HFO) 1.05 x 10 - 12 exp (

- 1600/T) (b)

cm 3 /molecule
. sec 3.37 x 10 - 15 (c)
cm 3 /molecule
. Sec 6.05 x 10 - 13 exp (

- 1700/T) (b)
cm 3 /molecule
. sec 1.7 x 10 - 12 exp (

- 1500/T) (b)
cm 3 /molecule
. sec 1.05 x 10 - 12 exp (

- 35/T) (g)
cm 3 /molecule
. sec Major atmospheric oxidation products initiated by OH COF 2 ( d ) CF 3 COF ( trifluoroacetyl fluoride) COF 2 (carbonyl fluoride) HCOF (formyl fluoride) COF2, CF3OH ( e ) COF2 ( e ) CF 3 COF (trifluoroacetyl fluoride) HCHO (formaldehyde) Hydroperoxyl radical (HO 2 ) NO 2 Further conversion of major atmospheric oxidation products COF 2 converted into CO 2

and HF within 1

- 2 weeks COF 2 converted into CO 2 and HF within 1

- 2 weeks. CF 3 COF further hydrolyzed to CF 3 COOH (trifluoroacetic acid). HCOF decomposes to HF and CO COF 2 converted into CO 2 and HF within 1

- 2 weeks. CF 3 OH hydrolyzed with water or ammonia forming COF 2 and HF ( f ) COF 2 converted into CO 2 and HF within 1

- 2 weeks COF2 converted into CO 2 and HF within 1

- 2 weeks CF 3 COF further hydrolyzed to CF 3 COOH (trifluoroacetic acid).

Percentage of refrigerant converted to TFA 0% 7 to 21% (h) 0% 0% 100% (i)

Sources: (a) Forester, et al. (2007), (b) Sander et al. (2006), (c) Franklin (1993); (d) Tuazon and Atkinson (1993), ( e ) Wallington and Nielsen (1999), ( f ) Long et al., 2011 , (g) Papadimitriou, et al. (2008) , (h) Wallington et al., 1996, (i) Luecken et al., 2010

.3 

## Impact of TFA on Aquatic Life The 2010 analysis on the generation of TFA associated with emissions of HFO

- 1234yf conservatively assumed that HFO

- 1234yf will be used in the United States as a new car refrigerant in all new MVAC systems, refrigeration, and stationary air conditioning systems by 2020. The analysis further assumed that HFO

- 1234yf replaces other refrigerants on a one - to

- one basis

. Even considering t hat 100% of HFO

- 1234yf is converted to TFA when released into the atmosphere (Luecken et al., 2010) , the analysis concluded that the generation of TFA sh ould not result in a significant risk to aquatic communities, soil and plants, or local air quality

. In contrast to HFO

- 1234yf, HFC

- 32 is not converted to TFA when released into the atmosphere (Wellington and Nielsen 1999)

. In fact, since HFC

- 134a is also converted to TFA in the atmosphere, using HFC

- 32 instead of HFC

134a or HFO

- 1234yf in room air conditioners w ould reduce the overall generation of TFA. Taking this into account as well as the conclusion s from the 2010 assessment (i.e., the generation of TFA from the emissions of HFO

1234yf will not result in a significant risk to aquatic communitie s, soil and plants, or local air quality ) , it can reasonably be concluded that the generation of TFA from the potential use of HFC

- 32 in room air conditioners will not result in a significant risk to aquatic life.4 

## References Forster, P., et al. (2007), Changes in atmospheric constituents and in radiative forcing, in Climate Change 2007: The Physical Science Basis, contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Chap. 2, pp. 129

– 234, Camb ridge Univ. Press, Cambridge, U. K.
ICF International. 2010. Assessment of the Potential Impacts of HFO

- 1234yf and the Associated Production of Trifluoroacetic Acid (TFA) on Aquatic Communities, Soil and Plants, and Local Air Quality . Prepared by ICF Inte rnational for U.S. EPA. May 25, 2010. Kotamarthi, V.R., Rodriguez, J.M., Ko, M.K.W., Tromp, T.K., Sze, N.D., and Prather, M.J. Trifluoracetic acid from degradation of HCFCs and HFXs: A three

- dimensional modeling study. Journal of Geophysical Research, V ol. 103, No. D5, 5747

- 5758

- March 20, 1998. Long, Bo, Tan. X., Long, Z., Ren, D. and Zhang, W., Theoretical Study on Decomposition of CF3OH Catalyzed by Water Dimer and Ammonia, Chin. J. Chem. Phys . 24 16. doi:10.1088/1674

- 0068/24/01/16

- 21., 2011 Luecken , D.J., Waterland, R.L., Papasavva, S., Taddonio, K.N., Hutzell, W.T., Rugh, J.P., and Anderson, S.O. Ozone and TFA Impacts in North America from Degradration of 2,3,3,3

- Tetrafluoropropene (HFO

- 1234yf). A Potential Greenhouse Gas Replacement. Environ. Sci. Technol. , 2010 , 44 (1), pp 343

– 348

. O’Doherty, S. Cunnold, D.M., Miller, B.R., Mühle, McCulloch, J. A., Simmonds, P. G, and Manning, A. J. (2009) “Global and Regional Emissions of HFC

- 125 (CHF2CF3 ) from in Situ and Air Archive Atmospheric Observations at AGAGE and SOGE Observatories ” JGR, Research 114, No. D23304

- D2331, doi:10.1029/2009JD012184. Sander, S. P., et al. (2006), Chemical kinetics and photochemical data for use in atmospheric studies: Evaluation 15, JPL Publ. 06

- 2, pp. 101
– 153, Jet Propul. Lab., Pasadena, Calif. Tuazon, E. and Atkinson, R., Tropospheric Transformation Products of a Series of Hydrofluorocarbons and Hydrochlorofluorocarbons, Journal of Atmospheric Chemistry 17: 179

- 199, 1993. ROGER ATKINSON Wallington, T.J., Hurley, M.D., Fracheboud, J.M., Orlando, J.J., Tyndall, G.S., Sehested, J., Mogelberg, T.E., and Nielsen, O.J. Role of excited CF 3 CFHO radicals in the atmospheric chemistry of HFC

- 134a. J. Phys. Chem, 1 996, 100(46) 18116

- 18112

. Wallington, T.J. and Nielsen, O.J. Environmental Photochemistry , Chapter 3 Atmospheric Degradation of Anthropogenic Molecules, page 92. Published by Springer

- Verlag Berlin Heidelber 1999, ISSN 1433

- 6839.