Research co-led by York University and Environment and Climate Change Canada has unearthed new evidence about the impacts of hydrofluoroolefins (HFOs) on the environment.
HFOs have been positioned by some as the future of synthetic refrigerants. They have zero ozone-depleting potential and break down very quickly in the atmosphere, resulting in very low global warming potential.
This makes them the natural successor to hydrofluorocarbons (HFCs), which are now being phased down globally under the Kigali Amendment.
But concerns have been raised about the toxicity of pure HFOs breaking down in the environment and producing trifluoroacetic acid or TFA. It is thought that TFA finds its way into water bodies such as rivers and lakes through precipitation, where it may build up and pose an environmental threat.
The new research adds credence to these concerns.
Using Arctic ice cores, the team studied changes in the presence of short-chain perfluoroalkyl carboxylic acids (scPFCAs) such as TFA. They found a tenfold increase in these chemicals since 1990. This coincides with phasing down of ozone-depleting clorofluorocarbons (CFCs) via the Montreal Protocol and the uptake of CFC replacements – including some HFCs – that are sources of TFA.
“We saw a really strong relationship between the deposition of these chemicals and changes that had been made due to the Montreal Protocol,” says Assistant Professor Cora Young.
“The chemicals that we found, these PFAS chemicals, are extremely persistent in the environment – they have no known degradation pathway. What we’re now getting is the deposition of these persistent chemicals and it seems to be happening globally.”
The Environmental Investigation Agency (EIA) has also highlighted the findings of the study. It notes that the accumulation of TFA could be exacerbated in the future by the increased use of HFOs such as 1234yf, which creates far more TFA than the refrigerant it replaces, HFC-134a.
“Since 2017, almost all new cars in the USA and the EU have replaced HFC-134a with HFO-1234yf in air conditioning,” says the EIA. “HFO-1234yf is also mixed with HFCs and other HFOs to create a range of refrigerant blends with lower global warming potential, which are being promoted for use in commercial, industrial and transport refrigeration.”