The chemicals that helped save the ozone layer may be quietly seeding the planet with an indestructible pollutant.
Chemicals introduced to protect the ozone layer are now linked to the worldwide spread of a long-lasting and potentially harmful substance, according to new research. Scientists report that these replacements have unintentionally contributed to large-scale pollution by a so-called forever chemical that does not easily break down once released into the environment.
A team of atmospheric scientists led by researchers at Lancaster University has, for the first time, calculated the global impact of these chemicals. Their findings show that replacements for ozone-damaging CFCs, along with certain anesthetic gases, were responsible for depositing about a third of a million tonnes (335,500 tonnes) of trifluoroacetic acid (TFA) across Earth’s surface between 2000 and 2022.
Pollution That Continues to Build Over Time
The researchers warn that the problem is not slowing down. Many CFC replacement chemicals remain in the atmosphere for decades, allowing TFA pollution to keep increasing long after the gases are released. The study estimates that annual TFA production from these sources could reach its highest levels at some point between 2025 and 2100.
The research was published today (February 4) in the journal Geophysical Research Letters and relied on advanced chemical transport modeling. This approach simulates how gases move through the atmosphere, react with other chemicals, and eventually settle back onto the planet’s surface.
How Refrigerants and Anesthetics Produce TFA
Using this model, the team measured how TFA forms when certain gases break down in the atmosphere. These include hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs), which are widely used in refrigeration, as well as chemicals used in inhalation anesthetics.
Although these substances, known collectively as F-gases, are being phased out (following the Montreal Protocol and the later Kigali Amendment), their concentrations in the atmosphere continue to rise.
TFA is part of a broader group of man-made compounds called per- and polyfluorinated alkyl substances (PFAS). These chemicals are often referred to as forever chemicals because they persist in the environment for extremely long periods.
Growing Concerns About Environmental and Health Effects
Scientists are still working to fully understand the risks associated with TFA. The European Chemicals Agency classifies it as harmful to aquatic life. Studies have detected TFA in human blood and urine, and the German Federal Office for Chemicals has recently proposed that TFA be classified as potentially toxic to human reproduction.
While some agencies believe current TFA levels remain below thresholds that pose a direct risk to human health, concerns are growing about its steady and potentially irreversible buildup. This has led to calls for TFA to be recognized as a planetary boundary threat.
“Our study shows that CFC replacements are likely to be the dominant atmospheric source of TFA,” said Lucy Hart, PhD researcher at Lancaster University and lead author of the study. “This really highlights the broader risks that need to be considered by regulation when substituting harmful chemicals such as ozone-depleting CFCs.”
Tracking a Chemical That Travels the Globe
To test their findings, the researchers compared their model’s estimates of TFA production and deposition with real-world observations, including measurements from Arctic ice-cores and rainwater samples.
The model was informed by data from a global monitoring network that tracks how much of each source gas is present in the atmosphere and where it is located. These gases react with other atmospheric components, breaking down and forming TFA in the process.
Weather patterns were also built into the model to calculate how TFA moves and settles. The chemical can be washed out of clouds by rainfall or deposited directly from the air onto land and water surfaces.
Why the Arctic Is a Key Warning Sign
The modeling revealed that nearly all TFA detected in the Arctic originates from CFC replacement chemicals, despite the region being far from major emission sources. This finding highlights how widely TFA pollution spreads across the planet.
“CFC replacements have long lifetimes and are able to be transported in the atmosphere from their point of emission to remote regions such as the Arctic where they can breakdown to form TFA,” said Lucy Hart. “Studies have found increasing TFA levels in remote Arctic ice-cores, and our results provide the first conclusive evidence that virtually all of these deposits can be explained by these gases.”
New Refrigerants Add Future Uncertainty
Beyond polar regions, the researchers found additional concerns at midlatitudes. Their modeling supports growing evidence that HFO-1234yf, commonly used in car air conditioning systems, is becoming an important and likely expanding source of atmospheric TFA.
“HFOs are the latest class of synthetic refrigerants marketed as climate-friendly alternatives to HFCs,” said Professor Ryan Hossaini of Lancaster University and co-author of the study. “A number of HFOs are known to be TFA-forming, and the growing use of these chemicals for car air conditioning in Europe and elsewhere adds uncertainty to future levels of TFA in our environment.”
“There is a need to address environmental TFA pollution because it is widespread, highly persistent, and levels are increasing,” Professor Hossaini said.
Calls for Long-Term Monitoring and Global Action
“The rising levels of TFA from F-gases is striking. Although HFC use is gradually being phased down, this TFA source will remain with us for decades. There’s an urgent need to understand other TFA sources and to assess TFA’s environmental impacts. This requires a concerted international effort, including more extensive TFA monitoring in the UK and elsewhere,” he said.
Professor Cris Halsall, Director of the Lancaster Environment Centre and co-author, emphasized that the origins of TFA are broader than once thought.
“We’ve generally viewed TFA as a breakdown product from the use of a few fluorinated pesticides, but it’s clear that TFA (a very persistent chemical in the environment) arises from the use and breakdown of a very wide group of organofluorine chemicals including refrigerants, solvents, pharmaceuticals, and the PFAS group in general.”
Co-author Dr Stefan Reimann, whose team in Switzerland closely monitors TFA-forming gases in the atmosphere, said global measurements are painting a consistent picture.
“In all regions where TFA measurements are available, a consistent picture of increasing atmospheric concentrations and deposition to Earth’s surface is emerging,” he said.
“This study is outstanding, as it combines for the first time all the important sources of atmospheric TFA and has a global focus. With increasing use of HFOs, accumulation of TFA in water bodies will potentially grow, and this makes long-term monitoring a necessity.”
Reference: “Growth in Production and Environmental Deposition of Trifluoroacetic Acid Due To Long-Lived CFC Replacements and Anesthetics” by Lucy Hart, Ryan Hossaini, Oliver Wild, Andrea Mazzeo, Crispin Halsall, Xuewei Hou, Zihao Wang, Martyn P. Chipperfield, Jgor Arduini, Paul B. Krummel, Chris R. Lunder, Jens Mühle, Simon O’Doherty, Sunyoung Park, Stefan Reimann, Kieran M. Stanley, Ray F. Weiss and Dickon Young, 4 February 2026, Geophysical Research Letters.
DOI: 10.1029/2025GL119216
The study involved researchers from: Lancaster University; the University of Leeds; the University of Urbino; the Commonwealth Scientific and Industrial Research Organisation, Australia; the Norwegian Institute for Air Research; the University of California San Diego; the University of Bristol; the Kyungpook National University, Korea; the Swiss Federal Laboratories for Materials Science and Technology; and the Goethe University Frankfurt.
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3 Comments
So, they replaced CFCs with a close chemical cousin. How did that make sense?
“Never” is a long time.
There was a time when refrigerators used ammonia or sulfur dioxide, both very toxic. People died as a result of leaks. Chemists looked for non-toxic refrigerants. Chemically inert CFCs looked like a good choice. Nobody anticipated that the heavy CFC molecules would rise into the stratosphere, be decomposed by UVC and release chlorine, subsequently attach to ice crystals when it got very cold, and act as a photo-catalyst to destroy ozone.
This is another case of where the public is only being told a part of the story. The role played by CFCs is overstated and the occasional story about the so-called ‘Ozone Hole’ healing is not supported by much more than wishful thinking. Don’t take my word for it, go to the NASA Goddard website at https://ozonewatch.gsfc.nasa.gov/SH.html If you look at the bar charts at the bottom left of the page, you will see that the ‘depth’ of the holes and the extent aren’t much different in recent years than they were in the 1990s, shortly after the Montreal Protocol. Temperature, controlling the circumpolar vortex, seems to play a much more important role than the concentration of CFCs. Besides that, the sun is NEVER directly above the ‘Hole,’ and the maximum ozone destruction takes place when the sun is on the horizon, as weak as the sun always is at dawn, plus the rays of the sun have a long slant-range that scatter and absorb the UV more strongly than when the sun is higher in the sky. Lastly, the Brewer-Dobson circulation brings stratospheric ozone from the tropics, but it can’t get past the circumpolar vortex, and builds up outside to the highest levels observed anywhere on Earth. The sunlight has to go through those anomalously high ozone levels, with the UV being significantly reduced in intensity while doing so. Lastly, the Media focus on the potential for UV damage, using ozone as a proxy for the risk, thus the concern. However, ask yourself if you have EVER seen a report about penguins getting cataracts or sunburn from high levels of surface UV. By the time that the sun gets high enough in the sky to be a potential risk to life, the ozone levels are usually back to the levels that extant life forms evolved to tolerate.