Forever chemical TFA has tripled due to ozone-preserving refrigerants

Trifluoroacetic acid (TFA), a potentially toxic “forever chemical,” has more than tripled in the global environment in two decades due to refrigerants helping to fill the hole in the ozone layer.

The amount of TFA falling from the atmosphere through wind and rain has increased from 6,800 tonnes per year in 2000 to 21,800 tonnes in 2022. Although this figure is below known safety thresholds, the effects of TFA on human health have not been studied in detail and their accumulation in the environment is expected to accelerate.

TFA caused eye deformities in most rabbit fetuses exposed to it in a test. The European Union has classified it as harmful to aquatic life and is considering whether it is toxic to human reproduction.

“It’s shocking that we’re emitting large amounts of a chemical into the environment and we have very little understanding of its impacts, and it’s basically irreversible,” says Lucy Hart of Lancaster University, UK, who led the new research.

Humans and animals will be exposed to TFAs in soil and surface waters until they flow to the sea and become trapped in ocean sediments after decades or centuries.

Chlorofluorocarbons (CFCs) were once found in refrigerators, aerosols, fire extinguishers and other items. But they were banned in 1989 after they were found to create a hole in the Earth’s protective ozone layer. They have been largely replaced by hydrofluorocarbons (HFCs), which react with hydroxyl radicals in the atmosphere to form compounds including TFA.

While HFCs are now being phased out, they are often replaced by hydrofluoroolefins (HFOs), which break down into TFA at a much higher rate. HFO-1234yf, which is now found in the air conditioners of hundreds of millions of cars, produces 10 times more TFA than the HFC it is gradually replacing. Pesticides, pharmaceuticals, and industrial chemicals are also sources of TFA.

Cores from the ice sheets of northern Canada and Svalbard revealed that TFA concentrations there have increased since the 1970s. Based on long-term atmospheric measurements of nine CFC replacement gases, Hart and colleagues modeled the rate at which TFA was being produced and deposited around the world, revealing a 3.5-fold global increase.

This rate could double by 2050 based on HFCs alone, which can persist for several decades in the atmosphere. Other research found that HFO-1234yf could increase AGT production more than 20-fold by 2050.

Although the world cannot return to CFCs and should continue to move away from HFCs, which have a significant effect on global warming, alternatives to these chemicals require further examination, says Lucy Carpenter of the University of York, UK.

Ammonia already cools many food warehouses and industrial processes, and could also be used in household refrigerators and air conditioners. Carbon dioxide is another natural refrigerant.

“We need to seriously consider whether there are better alternatives to HFO-1234yf,” says Carpenter. “TFAs have increased and will continue to increase… They are now found in all kinds of food products where they were never found before. They are found everywhere.”

A 2020 study found high concentrations of TFA in the blood of 90% of Chinese people, which is a hot spot for the chemical due to industrial pollution and hot, humid weather in many places.

The EU, which is developing proposals to permanently ban the chemicals, has predicted that TFA concentrations in fresh water will eventually reach toxic levels. But he was criticized for hiring a consulting firm that also lobbied for chemical manufacturers and disputed this expected increase in TFA.

The new findings provide a call to action to study both HFOs and their possible substitutes, so countries can break the cycle of adopting chemicals with unintended consequences, says Hart. Unlike HFCs, HFOs break down within a few days, giving us better control. “If we stop emitting it, you will very quickly stop the production of TFA,” she said.