TFA as an atmospheric breakdown product

TRIFLUOROACETIC ACID

(TFA)

TFA is a naturally occurring substance but can also be produced by the breakdown of some HFCs or some HFOs and some HCFCs in the atmosphere.

WHERE IS TFA FOUND?

HOW DOES TFA MAKE IT ASHORE?

TFAs on land are believed to have been transported by the mechanical action of wind on the sea, just like sea salt aerosol.

The aerosol is then deposited when it rains

After potentially travelling several hundred kilometres because the atmospheric life of TFA is two weeks.

POTENTIAL IMPACT OF TFA

TFA deposited on land and in water has the potential to accumulate in terminal water bodies (eg lakes) and in plants. However, based on the relative insensitivity of aquatic organisms to TFA, they are not expected to be impaired significantly. Its toxicity to algae, plants, fish, crustaceans animals and humans was found to be very low.

THE EFFECTS OF F-GASES

Some HFCs, HCFCs and HFOs, containing the CF3-C group, can break down to TFA, the amount depending on the specific molecule. By 2050 the total additional contribution of TFA to the oceans was estimated at less 7.5%. With the 2016 Kigali Amendment, the TFA due to global HFC use, is projected to be lower but partially offset by increased use of HFOs.

The TFA yields and other breakdown products for HFCs, HFOs and HCFOs can be found here.

Important Conclusions from the 2018 Scientific Assessment of Ozone Depletion

There is increased confidence that trifluoroacetic acid (TFA) produced from degradation of HFCs, HCFCs, and HFOs will not harm the environment over the next few decades. This assessment is based on the current estimates of future use of hydrofluorocarbons, HCFCs, and HFOs. It is noteworthy that HFCs and HCFCs have atmospheric lifetimes long enough to globally distribute any TFA emissions, while HFOs have atmospheric lifetimes so short that TFA emissions are deposited near the point of emission. Periodic re-evaluation is prudent, given the uncertainties in the sources and sinks of TFA and because of its persistence in the environment.

Page ES.50

The large body of published field measurements, toxicological studies, modelling studies, and environmental assessments point to a clear conclusion: The current and estimated future concentrations of TFA and its salts resulting from degradation of HCFCs, HFCs, and HFOs do not pose any known significant risk to human or ecosystem health.

More conclusions bat the Assessment Panels are here

About TFA

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What is TFA

TFA (trifluoroacetic acid and its salts). TFA is very stable in the environment as the trifluoroacetate ion (CF3COO) which will be combined with counter-ions such as sodium, in seawater, or calcium or ammonium (NH4+) inland, to form neutral salts. “TFA” is used as shorthand for trifluoroacetic acid and its salts.

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Naturally Occurring TFA

Over 200 million tonnes are present in the oceans, both coastal and deep-ocean seawater, having apparently accumulated over many million years from chemical reactions in or around sub-sea volcanic vents. More than 95% of TFA found in the oceans is naturally formed. The concentration in the oceans is small (about ~200 ng L−1 or ~ 2 x 10-10 g of TFA /g of sea water). 

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The evidence is that TFA occurs naturally

The evidence is clear and irrefutable that TFA occurs naturally in large quantities in the environment. The occurrence of other fluorinated organic substances that occur naturally is also well established, for example CF4 is naturally present in granites and fluorites in the continental crust.

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Transport of naturally occurring trifluoroacetic acid (TFA) by sea salt aerosol

The concentrations of trifluoroacetic acid and its salts (TFA) observed in air and rain at a time (1990s) when the introduction of TFA into the atmosphere, either directly or through decomposition of fluorocarbons was insignificant, were about two orders of magnitude larger than expected from fluorocarbon decomposition. Additional sources, substantially larger than the known anthropogenic sources, are needed to explain the historically observed environmental concentrations of trifluoroacetate in rain and surface waters. The world’s oceans constitute a significant TFA reservoir (estimated at over 200 Tg) and the generation of sea salt aerosol by mechanical action of wind on the sea surface is well known. It is postulated that this provides a mechanism for transportation of significant quantities of TFA over considerable distances, further even than sea salt aerosol. This represents a variable background concentration of TFA in the environment that supplements any generated by decomposition of fluorocarbons.

 

The EFCTC paper ‘Transport of naturally occurring trifluoroacetic acid (TFA) by sea salt aerosol’ can be downloaded here.

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Where is TFA Found

TFA is found in the oceans.  It was also found in samples of fog, rain, river and lake water analysed during the 1990s. TFA is also found in soil samples, including in an archived soil sample from 1865. Generally, soil retention of TFA is poor and the TFA will ultimately enter the aqueous environment.

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TFA and Organisms

The salts of TFA are inert and not of toxicological or environmental concern in the small concentrations (~200 ng L−1) that are present in the ocean. The current and estimated future concentrations of TFA and its salts resulting from degradation of HCFCs, HFCs, and HFOs do not pose any known significant risk to human or ecosystem health.

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TFA from HFCs and HFOs

TFA is produced as a breakdown product of some HFCs, including HFC-134a, and from HFO -1234yf.  No TFA is formed from HFO-1234ze(E). No TFA was found experimentally for the breakdown of  HCFO-1233zd(E), but recent modelling suggests up to 2% could theoretically be formed. Some HCFCs (HCFC-123 and -124) also breakdown to produce TFA.  

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Effect of TFA from HFCs and HFOs

For an upper range scenario of global HFC use by 2050 it was estimated that the total additional contribution of TFA to the oceans would be less 7.5% of the TFA present at the start of the millennium. With the 2016 Kigali Amendment to the Montreal Protocol, the TFA due to global HFC use, and hence TFA formation as a breakdown product, is projected to be lower but partially offset by increased use of HFOs.

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TFA from other sources

TFA is produced as a breakdown product of a number of other chemicals and is produced synthetically by the chemical industry.

The evidence is that TFA occurs naturally

The evidence is clear and irrefutable that TFA occurs naturally in large quantities in the environment. The occurrence of other fluorinated organic substances that occur naturally is also well established, for example CF4 is naturally present in granites and fluorites in the continental crust.

A summary of the evidence that TFA occurs naturally can be downloaded here.

TFA from HFCs and HFOs

TFA is produced as a breakdown product of some HFCs and some HFOs. The yield of TFA from each substance is shown in this table.  This table also shows other breakdown products and provides references for the data sources. Some HCFCs (HCFC-123 and -124) also breakdown to produce TFA but these are no longer used in the EU and have essentially been phased out by the Montreal Protocol.

TFA UPDATES

Important Conclusions from the 2018 Scientific Assessment of Ozone Depletion

There is increased confidence that trifluoroacetic acid (TFA) produced from degradation of HFCs, HCFCs, and HFOs will not harm the environment over the next few decades. This assessment is based on the current estimates of future use of hydrofluorocarbons, HCFCs, and HFOs. It is noteworthy that HFCs and HCFCs have atmospheric lifetimes long enough to globally distribute any TFA emissions, while HFOs have atmospheric lifetimes so short that TFA emissions are deposited near the point of emission. Periodic re-evaluation is prudent, given the uncertainties in the sources and sinks of TFA and because of its persistence in the environment.

Page ES.50

The large body of published field measurements, toxicological studies, modelling studies, and environmental assessments point to a clear conclusion: The current and estimated future concentrations of TFA and its salts resulting from degradation of HCFCs, HFCs, and HFOs do not pose any known significant risk to human or ecosystem health.

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Important Conclusions from the 2018 Environmental Effects Assessment

Estimates of production of TFA in China, the USA, and Europe, from the degradation of HFO-1234yf from Its application in automobile air conditioners, and assuming no dilution, would be several orders of magnitude less than the chronic “no observable effect concentration” (NOEC) of 10,000,000 ng L–1 for TFA-Na salt from an  aquatic microcosms study.

Overall, there is no new evidence that contradicts the conclusion of our previous Assessments that exposure to current and projected concentrations of salts of TFA in surface waters present a minimal risk to the health of humans and the environment. A recent review of this topic reached a similar conclusion. [see Norwegian Environment Agency, 2017, Study on Environmental and Health Effects of HFO Refrigerants, Norwegian Environment Agency Report No. No. M-917|2017, Oslo, Norway, p. 349]

Executive Summary page 16

 TFA in European river water

A recent comprehensive study investigated the quantities of trifluoroacetate (TFA) found in major rivers across Germany. Following this study, it had been claimed that HFO-1234yf has possible negative consequences for the production of drinking water. However, currently HFO-1234yf is at most an insignificant contributor to the quantities of TFA found. Furthermore, based on a recent study on Future emissions and atmospheric fate of HFC-1234yf from mobile air conditioners in Europe, the projected growth in use of HFO-1234yf and resulting emissions of TFA is expected to have only a small contribution to the quantities of TFA found in German rivers. This is consistent with the conclusions from the 2018 Environmental Effects Assessment

Further information is available here.

More Resources

UNEP Ozone Secretariat, Ecological Issues on the feasibility of managing HFCs: Focus on TFA Inter-sessional informal meeting, 12-13 June 2015 Informal Brief on Ecological Issues on HFCs June 2015 see EFCTC Learn about TFA from HFCs HFOs.pdf

IPCC/TEAP Special Report: Safeguarding the Ozone Layer and the Global Climate System Chapter 2

World Meteorological Organisation (2010): Global Ozone Research and Monitoring Project—Report No. 52. Chapter 1

Available at: https://www.wmo.int/pages/prog/arep/gaw/ozone_2010/documents/Ozone-Assessment-2010-complete.pdf

Environmental Risk Assessment of Trifluoroacetic Acid, Jean Charles Boutonnet et al; Human and Ecological Risk Assessment 5(1):59-124 · February 1999, available at https://www.researchgate.net/publication/254217782_Environmental_Risk_Assessment_of_Trifluoroacetic_Acid

Norwegian Environment Agency, 2017, Study on Environmental and Health Effects of HFO Refrigerants, Norwegian Environment Agency Report No. No. M-917|2017, Oslo, Norway,

[1] EFCTC Learn about environment & breakdown products: Fluoride in the Atmosphere: A very small contribution from HFCs, https://www.fluorocarbons.org/wp-content/uploads/2020/07/EFCTC_Learn_about_Fluoride_in_atm_small_HFC_contribution.pdf.

Papers on use of HFO-1234yf and its degradation products

Stephan Henne, Dudley E. Shallcross, Stefan Reimann, Ping Xiao, Dominik Brunner, Simon O’Doherty, and Brigitte Buchmann, Future Emissions and Atmospheric Fate of HFC-1234yf from Mobile Air Conditioners in Europe, Environ. Sci. Technol., 2012, 46 (3), pp 1650–1658 DOI: 10.1021/es2034608.

Kajihara, H., Inoue, K., Yoshida, K., Nagaosa, R. 2010. Estimation of environmental concentrations and deposition fluxes of R-1234yf and its decomposition products emitted from air conditioning equipment to atmosphere. Proc. 2010 Int. Symposium on Next-Generation Air Conditioning and Refrigeration Technology, paper no NS24, Tokyo, Japan

Luecken, D. J., Waterland, R. L., Taddonio, N., Hutzell, W. T., Rugh, J. P., Andersen, S. O.,2010. Ozone and TFA Impacts in North America from Degradation of 2,3,3,3-Tetrafluoropropene (HFO-1234yf), A Potential Greenhouse Gas Replacement. Environmental Science and Technology, 44(1): 44,343–348

Papasavva, S., Luecken, D. J., Waterland, R. L., Taddonio, K. N., Andersen, S. O., 2009. Estimated 2017 Refrigerant Emissions of 2,3,3,3-tetrafluoropropene (HFC-1234yf) in the United States Resulting from Automobile Air Conditioning. Environmental Science and

Technology, 43(24):9252–9259