Researchers develop new technique to measure previously undetected airborne PFAS

By measuring for gaseous fluorine, one of the most prevalent and overlooked contaminants, scientists can better understand the extent of previously unaccounted for PFAS, comprised of thousands of organofluorine compounds. These compounds, used in a wide range of products from food, paint, paper packaging and dental floss to cosmetics and agrochemicals, can off gas fluorine.

The researchers measured how much fluorine was released into the air both in the lab and outside using chemicals, such as fluorosurfactant liquids, and found 65 to 99 per cent of the fluorine in the air inside the lab was not normally unaccounted for, while outside that number was about 50 per cent.

"I expected missing fluorine, but I didn't expect it to be so much. This new technique can measure all fluorinated things in the atmosphere, which has never been done before and shows the majority cannot be accounted for using our usual measurements," says senior author of the study Professor Cora Young, an atmospheric chemist and Guy Warwick Rogers Chair in York's Faculty of Science.

"It's important as missing gaseous fluorine accounts for a huge part of airborne PFAS compared to what we actually measure at the moment, which means a lot of the PFAS aren't being detected."

Most PFAS, known as forever chemicals, include fluorine bonded with carbon, a bond that doesn't naturally break down in the environment. Testing for fluorine is an easier way to assess how many PFAS are present in the air rather than measuring all 4,700 or so PFAS contaminants individually.

The high quantities of previously unknown PFAS points to a gap, not only in measuring them, but also in understanding their sources and the impact on the environment. Gaseous fluorine is a byproduct of chemicals used in a wide range of products from food, paint, paper packaging and dental floss to cosmetics and agrichemicals.

"Our lack of focus on this has been mostly because we didn't have the techniques to look at it properly. It's not that people hadn't thought that this might be important, it's that we didn't know how to do it, but now we do," says lead author RenXi Ye, a PhD student in Young's lab.

While there are techniques to measure total fluorine in soil and water, there wasn't one to capture it in its gas state in the atmosphere. The researchers used a method that they previously developed to test for total gaseous chlorine and adapted it to measure gaseous fluorine.

"Much of the focus of research on PFAS was on what's happening in the water in the soil, not as much on what happens in the air, despite the fact that these fluorinated compounds, by the nature of their chemical properties and that they are in so many commercial products, are more likely to go into the air," says Young.

The question of how much gaseous fluorine is going unaccounted for piqued the interest of York researchers last year while they were working on their Toronto Halogens, Emissions, Contaminants and Inorganics Experiment (THE CIX).

Should we worry?

Most people are highly concerned about PFAS exposure, but Young says it's too early to know what the effects are of from the off gassing of fluorine into the environment, either human or on the environment.

"Any fluorinated gas is a potent greenhouse gas, but the impact of that depends on how long it lasts in the atmosphere, but what is the impact of breathing this? When it comes to outdoor air and human exposure, we don't know a lot about how much we breath in," she says, adding she doesn't think anyone should panic, but it is an area that needs more research and could certainly have important implications.

The research -- A Method to Measure Total Gaseous Fluorine -- published in the journal Environmental Science & Technology Letters points out that unknown fluorinated chemicals emitted into the atmospherecould not only contribute to the transport of PFAS around the globe but also impact climate change.

PFAS in the Arctic in sometimes surprising quantities found in 50-year-old ice cores

PFAS is the atmosphere are even finding their way into pristine environments like the Arctic. In a recent study led by York PhD student Daniel Persaud with Young and team looked at perfluoroalkyl acids (PFAAs) in ice cores in the Arctic, from 1967 to 2016, on Ellesmere Island in Nunavut.

"The measurement covers the longest time period and so you're seeing that it has been accumulating for a very long time," says Young. The surprising part? "In the early part of the ice core, there was more than I thought there would be. I expected it to be accumulating since the 1990s, maybe the 1980s, but in the early part of the core, I thought there would be less"

As the longest deposition record in the Arctic for perfluoroalkylcarboxylic acids (PFCAs) and the longest record globally for perfluoroalkylsulfonic acids (PFSAs), it allowed for observations not previously possible.

Before the 1990s, the ice core showed some variable pulses of accumulation, which the researchers at first weren't sure about, but now think it may be linked to Arctic military activities of the time. Starting in the 1990s, however, the ice core shows a steadier accumulation of the chemicals up to the present.

The study shows that most PFAAs are present in the ice at Mt. Oxford icefield on Ellesmere Island and that over 50 years, there is a steady increase of PFCA deposits, but it also highlighted how ice cores are helpful in understanding how PFAS are transported long-range.

"We were able to confirm that the PFCAs we found in the ice cores are formed primarily through long-range atmospheric transport and oxidation of volatile precursors in the atmosphere," says Persaud.

The issue now, says Young, is that as the permafrost melts, this resource is disappearing which creates an urgent need to collect more ice cores to further illuminate temporal trends and possible sources of PFAAs.