Trifluoroacetic Acid Rain: A Milder PFAS-Like Concern as Environmental Concentrations Grow

      Trifluoroacetic acid (TFA) is now found all over the world. It is present in lakes, rivers, bottled water, beverages, food, and in animal and human livers, blood, and urine. Nature reports that:

“Over the past four decades, TFA levels have risen five- to ten-fold in the leaves and needles of tree species in Germany. Researchers have also documented rising levels of TFA in Canadian Arctic ice cores4 and in groundwater in Denmark.”

     TFA has strong carbon-fluorine bonds that are hard for natural processes to break down. That is why it is sometimes classed as a PFAS “forever chemical.” If classified as a PFAS, it would be the smallest molecule of them, and luckily, it is considered magnitudes less harmful than other PFAS chemicals.

     Whether it will ultimately be harmful or not depends on a better understanding of its health impacts and whether its concentration continues to grow. Nature notes that:

“…in June 2024, two German federal agencies petitioned the European Chemicals Agency (ECHA) to label TFA as a reproductive toxin and a very persistent and very mobile substance. The ECHA has opened this petition for public comment, which closes on 25 July.”

     However, other regulatory agencies do not consider TFA to be a PFAS and are not as concerned with its increasing presence in the environment.

“But other scientists say that TFA shouldn’t be counted in the definition of PFASs, partly because it doesn’t build up in humans and animals as other PFASs do. The US Environmental Protection Agency, for instance, doesn’t currently consider TFA to be a PFAS.”

     TFA is produced as a byproduct in the refrigeration, agrochemical, and pharmaceutical sectors. They typically use TFA as an ingredient to make larger fluorine-containing molecules, and it can escape from industrial facilities. Other chemicals can break down to form TFA, acting as precursors, but these do not occur in the rain.

“The TFA in rain comes from different sources — mainly some fluorinated gases (F-gases), including those used as refrigerants and in building insulation. These gases leak from air-conditioner units and insulation foam, mostly when products are in use or being discarded.”

     Since there was more TFA calculated to be present than could be produced from industry and chemical breakdowns, research began to explore whether it existed in nature. Some researchers think that TF is a naturally occurring salt in the oceans, but others disagree. Levels of TFA in ice cores have risen sharply since the 1980s.

“David O’Hagan, a fluorine chemist at the University of St Andrews, UK, who studies naturally occurring fluorinated compounds, says that he remains “truly unsure” about whether TFA could occur naturally. A few microorganisms do make fluorinated molecules, but because these have only one fluorine atom — not three — O’Hagan doesn’t think microbial processes would create TFA. Scientists have yet to identify possible geological mechanisms, he adds.”

“In the 1990s, AFEAS researchers concluded that TFA is not acutely toxic, by referring to earlier studies that had fed or injected TFA into mice and rats7. Huge quantities were needed to kill the animals, and by that metric, TFA was found to be “about as toxic as table salt”, says Thomas Cahill, an environmental toxicologist at Arizona State University in Tempe.”

     Some animal studies have shown that TFA could have significant reproductive toxicity, but those experiments utilized levels of TFA hundreds of thousands of times more concentrated than levels found in drinking water.

“In 1976, to check whether TFA is a harmful metabolite of the anaesthetic halothane, researchers injected two volunteers with TFA, and recovered all of it in urine within three days. Many scientists think that TFA does not build up in organs and tissues, but instead behaves like a salt.”

     Since TFA does not bioaccumulate like PFAS and since it has not been found to be toxic at current concentrations, I would argue that it is not a chemical of great concern.

 

 

     

References:

 

There’s a new acid in our rain — should we be worried? Scientists and regulators are divided over the threat posed by rising levels of a chemical called TFA. XiaoZhi Lim. Nature. July 23, 2025. There’s a new acid in our rain — should we be worried?