Ozone-Saving Gases Are Raining PFAS 'Forever Chemicals' Back Onto Earth — 335,500 Tonnes of TFA Deposited (2000–2022)

Gases introduced to protect the ozone layer are breaking down in the atmosphere and returning to Earth as trifluoroacetic acid (TFA), a persistent PFAS compound. A Lancaster University modelling study estimates roughly 335,500 tonnes of TFA were deposited globally between 2000 and 2022, raising new concerns about unintended pollution from chemical substitutes.

What the Study Found

Researchers modelled the atmospheric fate of HCFCs, HFCs and certain inhaled anesthetics, tracking how these replacement substances move through the air, react with other chemicals, and ultimately deposit onto land and water. Although many F-gases are being phased out under international agreements, atmospheric concentrations of several replacement compounds are still rising and some persist for decades.

The modelling suggests that in remote regions such as the Arctic — far from local emissions — replacement gases could account for nearly all measured TFA. Outside polar regions, the refrigerant HFO-1234yf, increasingly used in vehicle air conditioning, is flagged as an emerging and growing source of atmospheric TFA.

Why TFA Matters

TFA is part of the broader PFAS family, often called "forever chemicals" because they resist degradation and can accumulate in water, soil, and living organisms. The European Chemicals Agency has classified TFA as harmful to aquatic life, and monitoring studies have detected traces in human blood and urine.

Some regulatory bodies currently assess environmental concentrations as below levels expected to cause direct human harm. However, the study authors warn that TFA is accumulating globally and will be difficult to remove once widespread in water bodies and ecosystems.

“Our study shows that CFC replacements are likely to be the dominant atmospheric source of TFA,” said lead author Lucy Hart. Professor Ryan Hossaini added, “There is a need to address environmental TFA pollution because it is widespread, highly persistent, and levels are increasing.” Co-author Dr. Stefan Reimann noted a consistent picture of rising atmospheric concentrations wherever measurements exist.

Policy and Practical Implications

The findings, published in Geophysical Research Letters, underscore the trade-offs involved in chemical substitution: a compound can be less harmful to the ozone layer or climate yet still produce long-term environmental problems. The study highlights the need for regulators to consider downstream breakdown products and persistence when approving or phasing in replacement chemicals.

Addressing this issue may require updated risk assessments, expanded monitoring of TFA in remote and populated regions, and consideration of alternatives that minimize formation of persistent degradation products.

Bottom line: Replacing ozone-depleting gases reduced one environmental risk but has created a different, persistent pollution pathway that now demands attention from scientists, regulators, and industry.