A toxicologically based drinking water guideline value of 60 µg/L currently applies to TFA in drinking water. However, further toxicological data presented in 2024 could lead to a reassessment. As part of the “TFA-Trink” project, the following was conducted: an assessment of the impact on the German drinking water supply of introducing a limit value or reducing the currently applicable guideline value for TFA based on toxicological considerations; an evaluation of the technical treatment options for controlling the risk; and recommendations for water supply companies on handling TFA technically and for discussions with authorities and consumers.
The chemical trifluoroacetic acid (or its anion trifluoroacetate, TFA, used synonymously for both chemical species) cannot be eliminated by natural or technical drinking water treatment processes and thus poses a potential risk to drinking water and human health. Due to the persistence of the substance, continuous emissions lead to an accumulation of TFA in drinking water resources. According to the current definition, TFA and TFA precursor compounds (i. e., substances that degrade into TFA) are classified as part of the chemical group of per- and polyfluorinated alkyl substances (PFAS), which are currently under intense scrutiny by the public and authorities.
TFA enters the aquatic environment from a variety of anthropogenic sources, with a distinction made between primary sources (i. e., direct emission of the substance itself) and secondary sources (i. e., TFA contamination resulting from the degradation of emitted precursors). An important primary source of TFA in the aquatic environment is industrial discharges from facilities that produce and/or process the substance. Secondary sources are diverse, as any compound containing at least one carbon-bound trifluoromethyl group in its chemical structure is a potential TFA precursor. TFA precursors are used, among other things, as active ingredients in plant protection products (PPP) and pharmaceuticals, as well as in propellants and refrigerants. TFA can therefore be classified as a "Substance from Multiple Sources" (SMS). It is assumed that drinking water resources in Central Europe are already contaminated via atmospheric deposition (i. e., due to the degradation of propellants and refrigerants) with more than 0.3 µg/L TFA on average.
The current drinking water guideline value for TFA in Germany, based on comprehensive toxicological data, is 60 µg/L. One reason for the present assessment was concerns that newly submitted toxicological data might lead to a lowering of the drinking water guideline value or possibly the application of the general limit value for relevant PPP metabolites to TFA. However, a clear attribution of contamination to a specific source (in this case: PPP application) is hardly possible for an SMS like TFA.
A literature review was conducted on the current contamination of German drinking water resources with TFA. In most samples considered in this study, concentrations significantly exceeding 0.1 µg/L TFA were detected. Removal of TFA during drinking water treatment is only possible through reverse osmosis, whose widespread implementation in drinking water supply is inadvisable for many reasons. Other risk management measures such as ozonation, activated carbon treatment, or chlorination are practically ineffective.
The study shows that only the protection of drinking water resources provides an effective basis for ensuring drinking water quality. Due to strong indications of increasing TFA emissions and thus rising contamination of drinking water resources with TFA, a general reduction of TFA emissions – regardless of the emission pathway – is essential for precautionary and minimization purposes.
