New Research Maps How Trifluoroacetic Acid Accumulates in Water Systems Across Europe

From the air into the rain and into the water: The PFAS molecule TFA is highly mobile and extremely persistent. Image: Adobe Stock

(IN BRIEF) Empa researchers, working with the Swiss Federal Office for the Environment and the University of Bern, have investigated how trifluoroacetic acid forms in the atmosphere and accumulates in water systems. Using long-term measurements and advanced modeling, the study shows that TFA concentrations in precipitation and surface waters have increased sharply in recent decades, driven largely by the growing use of hydrofluoroolefins in refrigeration and propellants. The research also identifies pesticide degradation as an additional source and highlights that significant knowledge gaps remain regarding unknown precursors. Given TFA’s extreme persistence and potential health risks, the researchers call for precautionary action to limit further environmental accumulation.

(PRESS RELEASE) DÜBENDORF, 6-Jan-2026 — /EuropaWire/ — Researchers at Empa have completed a comprehensive study examining how trifluoroacetic acid (TFA), one of the smallest and most persistent PFAS compounds, forms in the atmosphere and ultimately enters surface and groundwater systems through precipitation. The research was carried out in collaboration with the Swiss Federal Office for the Environment and the University of Bern, combining long-term environmental measurements with advanced atmospheric modeling.

The study draws on three years of precipitation and surface water measurements, supplemented by archived water samples dating back to 1984. These data were paired with a detailed atmospheric model capable of simulating the formation, transport, and deposition of TFA across Europe. The findings show that releases of TFA into the environment have increased significantly over recent decades and are expected to continue rising in the future.

TFA belongs to the broader class of per- and polyfluoroalkyl substances (PFAS), often referred to as “forever chemicals” due to their extreme persistence in the environment. Once formed, TFA is barely degraded and moves easily through air and water. After entering precipitation, it migrates into surface waters and groundwater, where it can remain for extended periods and ultimately accumulate in the oceans.

TFA is the smallest molecule in the PFAS family. (black: carbon, red: oxygen, white: hydrogen, blue: fluorine) Graphic: Adobe Stock.

A key driver behind the growing presence of TFA is the increased use of hydrofluoroolefins (HFOs). These fluorinated compounds are widely used as refrigerants and propellants to replace climate-warming hydrofluorocarbons (HFCs). While HFOs break down more quickly in the atmosphere than their predecessors, they degrade into byproducts including TFA. As the use of HFOs continues to expand in cooling and air-conditioning systems, researchers expect atmospheric deposition of TFA to rise accordingly.

The study also identifies pesticide degradation as another important source of TFA, although in this case the compound enters water bodies more directly through soil rather than via atmospheric pathways. Once present in aquatic systems, TFA is highly resistant to removal, reinforcing concerns about long-term accumulation.

Despite its detailed scope, the research highlights remaining knowledge gaps. The atmospheric model accounts for roughly two-thirds of the measured TFA input, suggesting that additional precursor substances or formation pathways may exist. This conclusion is supported by the detection of TFA in historic precipitation samples collected before many known precursors were introduced. Future research will focus on identifying these unknown sources and refining the model.

While the full health impacts of TFA are not yet conclusively established, emerging studies indicate potential long-term toxicity. Given its persistence and increasing concentration in water systems, the researchers emphasize the importance of precautionary measures, including limiting the use of substances that contribute to TFA formation.

The findings were published in the peer-reviewed journal Atmospheric Chemistry and Physics.

PFAS, the forever chemicals

The PFAS class of substances comprises thousands of chemical compounds. They contain fluorocarbon bonds, and many of them are known to be extremely stable, meaning that they hardly decompose in the environment. The health effects of PFAS are not yet fully understood, but they are associated with a variety of diseases, from organ damage to cancer. In the new Pocket Facts, Empa, Eawag, and the Ecotox Center provide information about these forever chemicals and how they can be avoided.

Further information

Dr. Stephan Henne
Empa, Air Pollution / Environmental Technology
Phone +41 58 765 46 28
stephan.henne@empa.ch

Dr. Stefan Reimann
Empa, Air Pollution / Environmental Technology
Phone +41 58 765 46 38
stefan.reimann@empa.ch

Prof. em. Dr. Markus Leuenberger
Universität Bern
markus.leuenberger@unibe.ch

Editor / Media Contact

Andrea Six
Empa, Communications
Phone +41 58 765 61 33
redaktion@empa.ch

SOURCE: EMPA