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.

EFCTC Summary of latest information about TFA set out below: All the information below is taken from published sources and, in particular, from the UNEP Environmental Effects Assessment Panel and the Scientific Assessment Panel for the Montreal Protocol. From these objective assessments, it is clear that the low dispersed levels of TFA that are forecast in the future, from the use of HFCs and HFOs, even with published worst case scenarios, are orders of magnitude below the levels that would have an adverse effect.

In its Summary Update 2020 for Policymakers, the UNEP Environmental Effects Assessment Panel has summarised these scientific conclusions for TFA: The current low concentration of trifluoroacetic acid (TFA) produced by the degradation of several hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs), is currently judged not to pose a risk to human health or to the environment. Trifluoroacetic acid continues to be found in the environment, including in remote regions, although concentrations are currently very unlikely to have adverse toxicological consequences for humans and ecosystems [33,34]. While TFA is formed from the HFCs and HFOs regulated under the Montreal Protocol, a large amount of TFA was naturally formed over millions of years and has accumulated in the oceans. An unknown amount originates from fugitive emissions from chemical manufacture, waste disposal sites, laboratory use, and degradation of pharmaceuticals, pesticides, and industrial chemicals containing the trifluoromethyl group.

The 2021 scientific assessment by the Environmental Effects Assessment Panel (EEAP) of the United Nations Environment Programme (UNEP) provides the latest update on a wide range of issues since their most recent comprehensive assessment (2018). It includes a comprehensive summary for Trifluoroacetic acid (TFA) and points out that most PFAS have different properties from TFA. Some HFCs and some HFOs breakdown produce TFA in the atmosphere. The summary has these important findings, but read the complete summary as it covers these issues in much greater detail:

  • Trifluoroacetic acid continues to be found in the environment, including in remote regions, although not at concentrations likely to have adverse toxicological consequences.
    • Trifluoroacetic acid (TFA) is found in the environment as a salt, with a no-observed-effect-concentration (NOEC) for aquatic species, which is typically > 10,000 μg/L. TFA is produced by the environmental degradation of several hydrofluorocarbons (HFCs) and hydrofluoro-olefins (HFOs). Analysis of 1187 samples of rainwater collected in eight locations across Germany in 2018–2019 showed median and a precipitation-weighted mean concentration of TFA of 0.210 μg/L and 0.335 μg/L, respectively.
  • Other sources of TFA, besides from refrigerants and propellants that fall under the purview of the Montreal Protocol, may be more important but less understood.
    • Fugitive emissions of TFA have been reported from landfills, transfer stations, and incinerators in locations where manufacturing facilities produce fluorinated chemicals.
  • Current concentrations of TFA salts and related compounds in soil and surface waters do not present risks of adverse effects in aquatic and terrestrial plants and animals.
    • Historical and current measurements of TFA in soil and surface-water indicate de minimis risks when compared to no-effect-concentrations (NOECs) in laboratory and field-based testing.
  • Humans could be exposed to TFA via drinking water and food but there is no evidence to date of adverse effects on health
    • TFA salts are of low acute toxicity to mammals under conditions relevant to environmental exposure.

TFA Drinking water guidance value in Germany: The Environmental effects assessment panel comprehensive summary of Trifluoroacetic acid (TFA) effects [1] states that humans could be exposed to TFA via drinking water and food but there is no evidence to date of adverse effects on health. Recently the Federal Environment Agency UBA issued a revised guidance value for TFA in drinking water, based on improved toxicological studies availability for trifluoroacetate salts. This sets a drinking water health guidance value of 60 μg/L and a target value of 10 μg/L. The UBA was able to set a toxicologically justified LWTW for drinking water. The LWTW of 60 µg/L is based on the life-long tolerable daily intake of TFA via the drinking water (assumption: 2 L per day), in which no harm to human health is to be expected. This guideline replaces the health orientation value (GOW) of 3 µg/l (maximum values that apply if the toxicological data is incomplete). Relevant background information: From the 2021 EEAP scientific assessment, analysis of 1187 samples of rainwater collected in eight locations across Germany in 2018–2019 showed median and a precipitation-weighted mean concentration of TFA of 0.210 μg/L and 0.335 μg/L, respectively. The maximum measured concentration was 57 μg/L. The study on Future emissions and atmospheric fate of HFC-1234yf from mobile air conditioners in Europe assessed the future emissions of HFO-1234yf after a complete conversion of the European vehicle fleet and calculated that the use of HFO-1234yf would result in expected average values of 0.6 – 0.8 µg/L of TFA in European rainwater.

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.

Page 6.14

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

Environmental effects assessment panel issues comprehensive summary of TFA effects EFCTC Newsletter item from March 2021 ENVIRONMENTAL EFFECTS ASSESSMENT PANEL ISSUES COMPREHENSIVE SUMMARY OF TFA EFFECTS – Fluorocarbons

Neale, R. E., Barnes, P. W., Robson, T. M., Neale, P. J., Williamson, C. E., Zepp, R. G., et al. (2021). Environmental effects of stratospheric ozone depletion, UV radiation, and interactions with climate change: UNEP Environmental Effects Assessment Panel, Update 2020. Photochemical & Photobiological Sciences. https://doi.org/10.1007/s43630-020-00001-x. See sections 7.8 to 7.11 for Trifluoroacetic acid (TFA).

UNEP Environmental Effects Assessment Panel Summary Update 2020 for Policymakers available at Environmental Effects Assessment Panel (EEAP) | Ozone Secretariat (unep.org)

TFA Drinking water guidance value in Germany EFCTC Newsletter item from March 2021 IN BRIEF: TFA DRINKING WATER GUIDANCE VALUE IN GERMANY – Fluorocarbons

Trifluoressigsäure (TFA)–Gewässerschutz im Spannungsfeld von toxikologischem Leitwert, Trinkwasserhygiene und Eintragsminimierung. Erläuterungen zur Einordnung des neuen Trinkwasserleitwerts von 60 μg/L.
20. Oktober 2020. Umweltbundesamt www.umweltbundesamt.de

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

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