Published on 9 January 2026

TFA in rivers and lakes

Swiss rivers and lakes contain trifluoroacetic acid, known as TFA. In rivers, concentrations tend to be higher downstream as substances accumulate. Peak concentrations in lakes are often lower than in rivers, as the large volume of water has a diluting effect and many lakes are located further upstream. According to studies of selected Swiss surface waters conducted between 2020 and 2023, over 30 tonnes of TFA flow out of Switzerland every year, carried in rivers on their way out to sea. Comparisons with archive samples also show that TFA concentrations have risen by a factor of six compared to the 1980s and 1990s.

Selected watercourses were analysed for TFA from 2020 to 2023 as part of the National Monitoring Programme for substance load in Swiss watercourses (NAWA FRACHT). Water samples were taken from watercourses at nine locations. In addition, random samples were taken from six lakes at cantonal monitoring sites and analysed for TFA in a laboratory.

TFA concentrations in rivers and lakes, 2020–2023

Measurements were carried out in rivers and lakes in the catchment areas of the Rhine, Rhone and Inn, including several tributaries such as the Aare. These are the most important river catchment areas in Switzerland (see figure). Lakes including Lake Geneva, Lake Constance and Lake Zurich were also sampled.

Mean TFA concentrations in rivers and lakes

The TFA concentrations in the rivers were between 0.21 μg/L and 2.8 μg/L, with an increase in TFA concentrations being observed downstream in each case. This increase reflects the discharge of industrial and household wastewater. The Rhone, the Thur and the Rhine downstream of Basel had high TFA concentrations (mean: 0.8 to 0.88 μg/L), while the lowest values were found in the Inn at S-chanf (mean: 0.33 μg/L).

TFA concentrations in lakes were between 0.22 and 0.54 μg/L. Significantly higher concentrations were found only in Lake Geneva (around 1 μg/L), but this value is heavily influenced by past inputs due to the lake's long water residence time of more than ten years.

TFA concentrations in archive samples since 1987

Archive samples of river water taken from individual sites between 1987 and 2011 were also analysed for TFA. Compared to the TFA concentrations seen in samples from the 1980s and 1990s, more recent samples show sharp rises. Concentrations have increased more quickly in rivers and lakes (a factor of six) than in precipitation (a factor of four), which may be due to the fact that rivers and lakes also contain TFA from industrial and other sources.

TFA concentrations in rivers (1987-2025)

• What are concentrations and loads?

  The measured TFA concentrations (mass per volume, e.g. micrograms per litre) can be used with discharge data (volume per time, e.g. cubic metres per second) to calculate TFA loads.

  The annual load is the total mass of a substance that has been carried in water through the measuring point over the course of a year. In contrast, the concentration is only a snapshot that does not take into account how much water is currently flowing – in other words, the same concentration results in a low load at low discharge and a higher load at high discharge (see figure). Annual loads can be compared with the annual use of chemicals that can form TFA, e.g. fluoride pesticides and coolants. Essentially, if the annual load measured in rivers is greater than annual use, this indicates that there are as-yet unknown sources of TFA.

  The longer-term development of annual load data can indicate whether pollution in rivers is decreasing or increasing. Comparing individual rivers' respective loads shows which of them are driving the overall load and where major sources of TFA can be found. This information is important for identifying the causes of TFA pollution and recognising processes and dispersion paths in the environment, which in turn allows for a more targeted approach to regulation and enforcement.

  Concentration alone does not indicate the amount of a substance in the environment that pollutes the water over the course of a year.

  

  

  

  

TFA loads in rivers

Similar to concentrations, load levels also increase along the path of a river, with the highest loads found at the outlets of the catchment areas. Every year, more than 30 tonnes of TFA flow out of Switzerland in its rivers on their way out to sea. The highest loads are carried by the Rhine (20 tonnes) and the Rhone (8 tonnes).

Here are a few more figures to compare with these loads in rivers:

• TFA from the air is deposited onto the ground via precipitation. The annual amount of TFA deposited across Switzerland has been estimated at around 25 tonnes, based on measurements.
• A further three to ten tonnes per year may be released into the Swiss environment through the degradation of plant protection products. There are also other possible sources of TFA that cannot be quantified in more detail yet.

TFA has also been detected in groundwater:

TFA in groundwater

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Further information

• Links

  EMPA: Press release, 06.01.2026: Modeling the formation and distribution of trifluoroacetic acid (TFA) in the atmosphere - How a persistent chemical enters our surface waters.

  PFAS in watercourses

  PFAS in groundwater

  PFAS – was ist das?

  National Monitoring Programme for substance load in Swiss watercourses (NAWA FRACHT)

• Documents

  • Umweltbundesamt (D): Chemikalieneintrag in Gewässer vermindern - Trifluoracetat (TFA) als persistente und mobile Substanz mit vielen Quellen

    Quellen, Eintragspfade, Umweltkonzentrationen von TFA und regulatorische Ansätze. Hintergrund - November 2021

    PDF5.25 MB2 December 2025