Trifluoroacetic acid or trifluoroacetate (TFA) is a short-chain perfluorocarboxylic acid and the final degradation product of many fluorinated compounds such as perfluorinated and polyfluorinated alkyl substances (PFAS), pesticides, refrigerants and pharmaceuticals. TFA is very stable, difficult to degrade and long-lasting. Its good water solubility means that it is very mobile in the soil and can easily enter the groundwater. TFA stands for both trifluoroacetic acid and trifluoroacetate. In the environment, TFA is present as acetate.

Due to the widespread use of fluorinated compounds and its longevity, TFA is now present everywhere in the environment. It can be detected in groundwater, rainwater, rivers, oceans, soil and plants, with concentrations being highest in summer due to photochemical activity in the atmosphere(Bavarian State Office for the Environment).

The German Federal Environment Agency reports TFA values in precipitation of 0.335 μg/L on average(Umweltbundesamt 2023).

TFA is rapidly absorbed with food, partly fed into the enterohepatic circulation (the circulation of certain substances in the body of mammals between the intestine, liver and gall bladder), distributed in the body (including the placenta) and excreted via urine and faeces.

The acute toxicity of TFA is very low. Studies with repeated oral administration in rats have identified the liver as the target organ, with a slight enlargement of the liver being observed.

In 2017, the European Food Safety Authority (EFSA) evaluated TFA as a metabolite of the fluorinated pesticide active ingredient flurtamone. The accepted daily intake (ADI) for TFA was derived as 0.05 mg/kg body weight (bw) per day based on a 90-day rat study and an uncertainty factor (UF) of 200 for the extrapolation from subchronic to chronic. Based on the available toxicological studies, it was not necessary to derive an acute reference dose (ARfD) (EFSA 2017: https://www.efsa.europa.eu/en/efsajournal/pub/4976).

In Austria, TFA was analysed in groundwater as part of water status monitoring (GZÜV). TFA is widely detectable in groundwater in Austria. TFA was found in all samples from risk-based selected groundwater monitoring sites. The average TFA concentration is 0.71 µg/l, the maximum value is 7.0 µg/l. 75% of all samples showed concentrations below 0.81 µg/l TFA(Water Quality in Austria - Annual Report 2018-2020).

There is currently no EU-wide harmonised limit value (parameter value) for TFA in drinking water.

The German Federal Environment Agency (2020) has derived a health guideline value of 60 µg/l for TFA and points out that a concentration of 10 µg/l or less TFA in drinking water should be aimed for. The Dutch Institute for Public Health and the Environment (RIVM 2023) has derived an indicative drinking water value of 2.2 µg/l. In Denmark, a limit value of 9 µg/l has been set for TFA in drinking water (Drikkevandsbekendtgørelsen (retsinformation.dk)).

The guideline "Handling of unregulated contaminants in drinking water, BMG-75210/0023-II/B/13/2014" stipulates that maximum levels from other countries can be used to set derived tolerance values. As soon as a new EFSA risk assessment is available, a new tolerance value should be derived.

Risk assessment

The human toxicological relevance of TFA is currently being re-evaluated in several plant protection product active substance renewal procedures. According to the Plant Protection Products Regulation (Regulation (EC) 1107/2009), a plant protection product metabolite is of human toxicological relevance if there is reason to assume that it has certain toxicological properties that are considered unacceptable.

Due to the ongoing procedure for the human toxicological reclassification of TFA at the European Chemicals Agency (ECHA), AGES has published a report entitled "Metabolites in groundwater and drinking water. Reassessment of the biological and human toxicological relevance of plant protection product active substance metabolites", AGES refrained from a preliminary human toxicological assessment. It recommends that TFA be considered to be of human toxicological relevance as a precautionary measure until an EU-wide harmonised classification in accordance with the CLP Regulation (Regulation (EC) 1272/2008) as defined in the Plant Protection Products Regulation is available. This must be taken into particular account in a risk assessment of TFA in drinking water in accordance with the Drinking Water Ordinance. The sub-commission for drinking water of the Austrian Food Codex will deal with a corresponding tolerance value for TFA in drinking water.

Hazard classification and labelling of the European Chemicals Agency (ECHA)

The hazard classification and labelling of TFA is carried out by the European Chemicals Agency (ECHA). The evaluation of the ECHA's Committee for Risk Assessment (RAC) is based solely on the hazardous properties of the substance and the question of whether the substance can cause harmful effects. The risk or the extent to which people and the environment are exposed to the substance is not taken into account.

Germany submitted a CLH report (REACH programme) on TFA to the ECHA on 11 June 2024. In this report, a classification as acutely toxic (Acute Tox. 3 - H331) and toxic for reproduction (Repr. 1B, H360Df) is proposed for TFA, among other things. The current classification of TFA by ECHA and the proposal for classification by Germany can be found at the following link: https://echa.europa.eu/de/registry-of-clh-intentions-until-outcome/-/dislist/details/0b0236e188e6e587

Definition of PFAS by the OECD

PFAS are defined by the Organisation for Economic Co-operation and Development (OECD) as fluorinated substances containing at least one fully fluorinated methyl or methylene carbon atom (without an H/Cl/Br/I atom attached), i.e. with a few exceptions, any chemical with at least one perfluorinated methyl group (-CF3) or one perfluorinated methylene group (-CF2-) is a PFAS(https://one.oecd.org/document/ENV/CBC/MONO(2021)25/En/pdf.