For many years, scientists were aware that there was a significant amount of per- and polyfluoroalkyl substances (PFAS) in the air that remained undetected, commonly referred to as PFAS dark matter. However, the magnitude of this absence and the method for measuring it were largely unknown. A research team specializing in atmospheric chemistry at York University has now developed a technique to evaluate one of the most common components of these powerful greenhouse gases.
For many years, scientists were aware that there was a significant amount of per- and polyfluoroalkyl substances (PFAS) in the air that remained undetected, commonly referred to as PFAS dark matter. However, the magnitude of this absence and the method for measuring it were largely unknown. Now, a York University atmospheric chemistry research team has created a method to test for one of the most common components of these potent greenhouse gases.
By analyzing gaseous fluorine, a prevalent yet often overlooked contaminant, scientists can gain insights into the extent of the previously unrecognized PFAS, which include thousands of organofluorine compounds. These compounds, found in various products ranging from food and paint to dental floss and agrochemicals, can release fluorine into the atmosphere.
The team measured the amount of fluorine emitted into the air in controlled laboratory conditions and outdoor settings using chemicals like fluorosurfactant liquids. They discovered that 65 to 99 percent of the fluorine in the laboratory air was unaccounted for, while outdoors, approximately 50 percent remained undetected.
“While I anticipated there would be missing fluorine, I did not expect the quantity to be so substantial. This new method can detect all fluorinated compounds in the atmosphere, a feat never accomplished before, revealing that much of it cannot be accounted for with our standard measurements,” states Professor Cora Young, the study’s senior author and an atmospheric chemist holding the Guy Warwick Rogers Chair at York’s Faculty of Science.
“This revelation is crucial as the missing gaseous fluorine represents a large fraction of airborne PFAS that our current measurements fail to capture,” she explains.
Most PFAS, often termed as forever chemicals, consist of fluorine linked to carbon—a bond that is resistant to natural breakdown. Testing for fluorine provides a simpler way to estimate the presence of PFAS in the air compared to assessing each of the approximately 4,700 individual PFAS contaminants.
The significant presence of previously undetected PFAS highlights a critical gap not just in measurement but also in comprehending their origins and environmental effects. Gaseous fluorine is associated with a wide range of products, from food and paint to dental floss and agricultural chemicals.
“Our previous lack of attention on this topic stemmed mainly from not having the right techniques to investigate it adequately. It isn’t that this was overlooked; it’s that we didn’t know how to approach it, but now we do,” says lead author RenXi Ye, a PhD student in Young’s lab.
While existing methods measure total fluorine in soil and water, there was previously no technique to capture it in its gaseous form in the atmosphere. The researchers adapted a previously developed method for measuring total gaseous chlorine to facilitate the detection of gaseous fluorine.
“Research on PFAS predominantly centered around their effects in soil and water rather than in the air, despite the fact that these fluorinated compounds are likely to enter the atmosphere due to their chemical properties and prevalence in commercial products,” Young points out.
The inquiry into how much gaseous fluorine goes undetected captured the attention of York researchers last year during their Toronto Halogens, Emissions, Contaminants and Inorganics Experiment (THE CIX).
Should we be concerned?
While public concern regarding PFAS exposure is high, Young cautions that it is premature to draw conclusions about the effects of fluorine off-gassing into the environment, whether on human health or ecological systems.
“Any fluorinated gas is a strong greenhouse gas, but the overall impact varies based on its atmospheric longevity, and we still lack information on the effects of inhalation. Our understanding of outdoor air quality and human exposure is limited,” she remarks, emphasizing that while there is no cause for alarm, further research is essential, as it may have significant implications.
The research entitled “A Method to Measure Total Gaseous Fluorine,” published in the journal Environmental Science & Technology Letters, notes that unidentified fluorinated chemicals released into the atmosphere could not only facilitate the global spread of PFAS but also have repercussions on climate change.
PFAS levels in the Arctic: surprising findings from 50-year-old ice cores
PFAS particles are infiltrating even the most untouched areas of the world, including the Arctic. A recent study led by York PhD student Daniel Persaud, along with Young and the research team, analyzed perfluoroalkyl acids (PFAAs) found in ice cores from Ellesmere Island in Nunavut, covering the years from 1967 to 2016.
“This measurement spans the longest time frame, revealing that accumulation has been occurring over a significant period,” remarks Young. Interestingly, she adds, “In the earlier segments of the ice core, the levels exceeded my expectations. I had anticipated accumulation would start around the 1990s, or perhaps the late 1980s, but the earlier sections of the core indicated higher concentrations than I had thought.”
The ice core serves as an extensive record for perfluoroalkylcarboxylic acids (PFCAs) in the Arctic and also provides the longest global record for perfluoroalkylsulfonic acids (PFSAs), enabling insights that weren’t available before.
Before the 1990s, the ice core indicated some fluctuating accumulation, which initially perplexed the researchers, but they now suspect it could be linked to military activities in the Arctic during that period. Conversely, from the 1990s onward, the record depicts a steady increase in these chemicals up to the present day.
The study illustrates that most PFAAs detected in the ice at Mount Oxford’s icefield on Ellesmere Island have shown a consistent rise in PFCA deposits over the past 50 years. It also emphasizes the value of ice cores in understanding the long-range transport of PFAS.
“We confirmed that the PFCAs identified in the ice cores primarily result from long-range atmospheric transport and oxidation of volatile precursors present in the atmosphere,” says Persaud.
Looking ahead, Young stresses that as permafrost continues to melt, this critical resource is at risk of disappearing, underscoring the urgent necessity to gather more ice cores for a better understanding of temporal trends and potential sources of PFAAs.
