by North Carolina State University
edited by Sadie Harley, reviewed by Robert Egan
In a new study appearing in Environmental Science and Technology, researchers found high levels of ultrashort-chain per- and polyfluoroalkyl substances (PFAS) in blood samples taken from Wilmington, N.C. residents between 2010 and 2016. Two ultrashort-chain PFAS—perfluoromethoxyacetic acid (PFMOAA) and trifluoroacetic acid (TFA)—were detected at high levels in almost every sample.
In contrast, GenX—the chemical that jumpstarted public concern about PFAS in the Cape Fear River Basin—was detected in 20% of the samples. The work adds to the body of evidence that short-chain PFAS can accumulate in the human body.
Ultrashort-chain PFAS such as PFMOAA and TFA have not been well-studied in people for two reasons: they were not thought to bioaccumulate due to their chemical structure, and until recently there were no analytical methods that allowed scientists to reliably detect them in blood.
"With the development of analytical methods targeting ultrashort-chain PFAS, researchers have found these compounds to be the dominant PFAS in environmental matrices including water and human blood," says Detlef Knappe, professor of civil, construction, and environmental engineering at NC State and co-corresponding author of the study.
"Given the long history of PFAS exposure in Wilmington, we wanted to look for these compounds in historical water and blood samples of residents."
In 2016, NC State and U.S. Environmental Protection Agency researchers published findings highlighting high concentrations of several PFAS, including GenX, in Wilmington residents' drinking water.
The Fayetteville Works plant, an upstream chemical facility, had been releasing PFAS into the Cape Fear River, the city's primary drinking water source, since 1980. After 2017, the chemical manufacturer was required to control PFAS discharges into the river and air.
For the current study, the researchers looked for 56 different PFAS in water samples from the Cape Fear River taken in 2017, as well as in 119 adult blood serum samples from a UNC biobank that were collected between 2010 and 2016. The serum samples were anonymized, but all were taken from residents in and around the Wilmington area.
The findings were surprising. In the blood serum, 34 of the 56 PFAS were detected in at least one serum sample. Five PFAS accounted for 85% of the total found in the samples. PFMOAA had the highest median concentration at 42 nanograms per milliliter (ng/mL), comprising 42% of the summed total, followed by TFA (17 ng/mL), PFOS (14 ng/mL), PFOA (6.2 ng/mL), and PFPrA (5.4 ng/mL).
Additionally, they found that TFA comprised 70% of the total PFAS in the 2017 water sample, with a concentration of 110,000 nanograms per liter (ng/L). PFMOAA had a concentration of 38,000 ng/L. While TFA has a variety of sources, including fluorinated refrigerants, the publication highlights that Fayetteville Works was the dominant source of both TFA and PFMOAA in the lower Cape Fear River.
"For reference, one European guideline recommends a drinking water level of 2,200 ng/L for TFA," Knappe says. "Our sample contained over 50 times that concentration."
"These data gave us a 'timestamp' of exposure before people knew their drinking water was contaminated," says Jane Hoppin, professor of biological sciences, principal investigator of the GenX Exposure Study, member of NC State's Center for Human Health and the Environment (CHHE), and co-corresponding author of the paper describing the work.
"The conventional wisdom is that short-chain PFAS are of lesser concern because they don't bioaccumulate, but what we're seeing is that they can occur at high levels in people," Hoppin adds. "These results point out the need to start thinking about how to study the human health effects of these PFAS, particularly TFA and PFMOAA.
"The other issue is how limited the human health data are for any of these chemicals. Most chemicals in the PFAS class affect the liver and immune system, but this work is still in its infancy in many cases."
Next steps include analyzing samples from the GenX Exposure Study for TFA and PFMOAA levels.
"The sample set gives us a glimpse into the past," Hoppin says. "Seeing what the levels are now will help us determine how these chemicals accumulate in the body and what their health effects might be."
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