A new study out of York University has found that the amount of atmospheric trifluoroacetic acid (TFA), the tiniest forever chemical, significantly declined in Toronto during COVID in 2020, which researchers say is good news for the world's ability to mitigate it in the future.
"When we turned off the tap, so to speak, and we all went home and stopped normal activities, we saw a really quick response, a dramatic reduction of TFA. But the real surprise is that the results point to TFA being formed from short-lived chemical precursors emitted into the atmosphere," says York University atmospheric chemist Professor Cora Young, senior author of the paper published today. "I was so surprised when we saw that it had decreased during the pandemic, but I had to double and triple check the data because I didn't believe it at first."
The reason it is such good news, says Young is "that when there is an immediate response after emissions reduction, it tells us that we should be able to figure out how to minimize the emissions and control the formation of TFA in the future. We could have a lot more control over this than we previously thought and that's very exciting. If we don't know where it's coming from, it's very difficult for us to regulate."
Unfortunately, as people returned to work and daily life, these levels have crept back up and they peak in the summer when there is more light, which is needed for its creation. A short-chain per- and polyfluoroalkyl substance (PFAS), TFA forms in the atmosphere when various chemical emissions come together.
"TFA is something that we haven't known a lot about before, but we're learning more now that we can measure it," says York University PhD Candidate Daniel Persaud, the paper's lead author. "With levels of TFA dropping during the pandemic, it now gives us a lot more information about its thousands of sources, such as industrial and vehicle air conditioner emissions."
The researchers collected and analyzed monthly measurements of both wet (rain and snow) and dry deposition – gases and particles that land on surfaces and form a layer of dust, for example, on windows and car windshields – from the Air Quality Research Station on roof of York's Petrie Science and Engineering Building between 2018 to 2024.
What is still unknown, is the effect of long-term exposure on people and wildlife. Young says TFAs are already orders of magnitude higher in the environment than some of the other PFAS, such as perfluorooctanoic acid, known as PFOA. PFOA was the subject of successful lawsuits with hundreds of millions in payouts, including from DuPont, which is also the focus of the 2019 documentary Dark Waters.
"The short-chain PFAS precursors were supposed to be more benign, and many are, but not all and so that created more unknowns about their effect. There is preliminary evidence that is behaving in ways we didn't expect. We're finding it at high concentrations in food, for example," says Young of York Faculty of Science.
"We didn't think that PFASs like TFA could bioaccumulate, but they've been found to accumulate in plants, and can be found in the food people and wildlife eat. It has even been found in human blood. Our exposure could still be quite high, even if it's not bioaccumulating. If TFA levels in the environment are driven by short-lived emissions, then that's something we can actually address now."
A little history
The main precursor chemicals that form short-chain PFASs are the second generation of chemicals designed to replace the ozone-depleting chlorofluorocarbons (CFCs), phased out globally starting with the 1987 Montreal Protocol. These first-generation replacement chemicals remain for years to decades in the atmosphere and can slowly react to form short-chain, persistent PFAS, like TFA, thought to be better than CFCs at the time, but these forever chemicals are now found everywhere from the Arctic to the Antarctic and there is no way to turn back the clock on them.
"The change from long-lived to short-lived precursors was made for climate reasons because the long-lived ones are also really potent greenhouse gases," says Persaud of the Faculty of Science. "We previously though the biggest source of TFA was first-generation CFC replacements, but our results show the important role of short-lived, next-generation replacements."
An example of that change is that in North America all car air conditioners from 2019 onwards now use a short-lived TFA precursor rather than the long-lived PFAS precursors. However, if these performance chemicals for air conditioners are finding their way into the atmosphere, it's expensive for car manufacturers and consumers for alike.
The paper, Atmospheric removal of TFA by dry and wet deposition: a multi year analysis in Toronto , was published in journal Environmental Science & Technology Letters.
