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, 2015

Re: Potential impacts 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 HFO1234yf 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 generated 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 aquatic 

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 (202-862-1155) with any questions.

 

1 The analysis—Assessment 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.
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Atmospheric Degradation of Relevant Refrigerants

Hydroflurocarbons (e.g., HFC-32, HFC-125, and HFC-134a) as well as hydrochlorofluorocarbons (e.g., HCFC-22)

undergo atmospheric degradation reactions 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 HCFC-22 (CHClF2) is carbonyl fluoride (COF2) and is the only carbon 

containing product formed (Tuazon and Atkinson 1993). COF2 is rapidly hydrolyzed in the presence of water to 

form HF (hydrogen fluoride) and CO2 (carbon dioxide). The only other degradation product found in studies of 

transformation products was HCl (hydrogen chloride). 

Atmospheric Breakdown of HFC-134a

The major atmospheric oxidation products of HFC-134a are carbonyl fluoride (COF2), CF3COF, formyl fluoride 

(HCOF), and HCOOH (Kotamarthi et al., 1998). COF2 is rapidly hydrolyzed in the presence of water to form HF

(hydrogen fluoride) and CO2 (carbon dioxide). In addition, HCOF decomposes at room temperature to form HF 

and CO. 

Atmospheric Breakdown of HFC-125

The major atmospheric oxidation product for HFC- 125 is through interaction with the hydroxyl (OH) radical to 

form COF2 and CF3OH (trifluoromethanol) (O’Doherty et al., 20009). The CF3OH is hydrolyzed with ammonia or 

water, with ammonia being the much faster reaction, forming COF2. The COF2 is rapidly hydrolyzed in the 

presence of water to form HF (hydrogen fluoride) and CO2 (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 

CHF2O radical and water (Wellington and Nielsen 1999). The CHF2O radical then reacts rapidly with oxygen to 

form COF2 which is rapidly hydrolyzed in the presence of water to form HF (hydrogen fluoride) and CO2 (carbon 

dioxide). In no studies has the formation of CF3COOH (TFA) been observed. 

Generation of TFA from Refrigerants Used in Room Air Conditioners

As discussed above, literature to date 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 HFC-32

and other commonly used refrigerants in room air conditioners. The degradation products of HFO-1234yf are also 

presented for reference.
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Table 1: Comparison of Atmospheric Degradation Products initiated by OH

Compound HCFC-22 HFC-134a HFC-125 HFC-32 HFO-1234yf

Formula CHClF2 CF3CH2F C2HF5 CH2F2 CF3CF=CH2

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)

cm3/molecule. sec

3.37 x 10-15 (c)

cm3/molecule. Sec

6.05 x 10-13 exp (-1700/T)(b)

cm3/molecule. sec

1.7 x 10-12 exp (-1500/T) (b)

cm3/molecule. sec

1.05 x 10-12 exp (-35/T) (g)

cm3/molecule. sec

Major atmospheric 

oxidation products 

initiated by OH

COF2

(d) CF3COF (trifluoroacetyl 

fluoride) 

COF2 (carbonylfluoride)

HCOF (formyl fluoride)

COF2, CF3OH(e) COF2(e) CF3COF (trifluoroacetyl 

fluoride) 

HCHO (formaldehyde) 

Hydroperoxyl radical (HO2)

NO2

Further conversion 

of major 

atmospheric 

oxidation products

COF2 converted into CO2

and HF within 1-2 weeks 

COF2 converted into CO2

and HF within 1-2 weeks.

CF3COF further hydrolyzed 

to CF3COOH 

(trifluoroacetic acid).

HCOF decomposes to HF 

and CO

COF2 converted into CO2

and HF within 1-2 weeks.

CF3OH hydrolyzed with 

water or ammonia forming 

COF2 and HF (f)

COF2 converted into CO2

and HF within 1-2 weeks

COF2 converted into CO2

and HF within 1-2 weeks 

CF3COF further hydrolyzed 

to CF3COOH 

(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. 
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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 that 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 should 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 HFC134a or HFO-1234yf in room air conditioners would reduce the overall generation of TFA. Taking this into account 

as well as the conclusions from the 2010 assessment (i.e., the generation of TFA from the emissions of HFO1234yf will not result in a significant risk to aquatic communities, 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, Cambridge 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 

International 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, Vol. 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 CF3CFHO radicals in the atmospheric chemistry of HFC-134a. J. Phys. Chem, 1996, 

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.