Scientists have warned about a new kind of acid rain that is everywhere, is almost impossible to clean up, and could be a threat to every living thing on planet Earth.
Trifluoroacetic acid (TFA) – a type of persistent 'forever chemical' – is now present in every rain shower and snowfall on the planet, in concentrations far higher than decades ago
We don’t yet know exactly what TFA might mean for human health and the environment, but some researchers have now said that the chemical could be an existential threat.
“There is emerging evidence that TFA can disrupt vital earth system processes, such as mammal embryo development and decreasing soil respiration,” Prof Hans Peter Arp, a chemist at the Norwegian University of Science and Technology, told BBC Science Focus.
Arp's most recent research classified TFA as a planetary threat similar to global warming or the depletion of ozone.
“We do not know the long-term consequences of this,” Arp continued. “But, if a long-term consequence occurs, it will occur on a global scale, as TFA is accumulating globally.
“And, once the impacts occur, it will be too late to do anything because TFA does not degrade naturally, and any technology to remove TFA is extremely costly and can only be used in small amounts.”
Arp's paper argued that action needed to be taken now to prevent the rapid accumulation of TFA, before it is identified as an urgent threat.
“In the heating and cooling sector, this means not using gases that lead to TFA formation,” said Arp.
“Another step is to transition away from pesticides and pharmaceuticals that create TFA when they degrade.”
Some countries have already taken action. Leading the way is Denmark, which banned 23 pesticides in July 2025 because of their links to TFA pollution.
TFA is a type of ‘forever chemical’ – a group of substances so named because they are very difficult to destroy, more formally known as per- and poly-fluoroalkyl substances (PFAS).
Out of all the forever chemicals, TFA is one of the smallest. It can leak into the environment from refrigerants, aerosols, pesticides, air conditioning units, landfills and sewage. And, when larger PFAS break down, they often become TFA.
Because it’s so small, TFA dissolves easily in water. That’s why it has become one of the most ubiquitous forever chemicals, with rapidly rising levels found in rain – as well as rivers, lakes, groundwater, oceans, leaves, food, and human blood and urine.
Arp said he became interested in the chemical once it was found in “otherwise pristine water resources” – which was especially concerning because TFA is considered almost impossible to remove from drinking water.
Some scientists have argued that TFA may not be particularly dangerous to humans because – unlike many other forever chemicals – it passes through the body quickly in urine, rather than lingering and accumulating inside us.
However, Arp said that the most recent evidence was clear: TFA levels were increasing inside humans, as well as in other animals and in the environment.
“We can see that TFA can enter cells and become building blocks in lipids, proteins and cell walls, which may account for other observations of changes in microbial activity in soils,” said Arp.
Scientists like Arp are trying to develop methods of removing TFA from the environment, such as by planting crops that absorb TFA, and then burning these crops in extremely hot conditions, to destroy the chemical.
But Arp said that further research was needed to determine the true threat level of TFA – and, in the meantime, “the first priority is to lower emissions now before the irreversible, global impacts occur.”
Read more:
- ’Forever chemicals’ are now in half of your fruits and vegetables. Here’s what that means
- This is the most powerful acid on planet Earth
- Is there acid snow (like acid rain)?
About our expert
Prof Hans Peter Arp is a chemist at the Norwegian Geotechnical Institute, and a professor at the Norwegian University of Science and Technology. His research focuses on how pollutants behave in the environment, including microplastics, forever chemicals, metals and more.
