The “forever chemicals” found in the Cape Fear River were detected through a non-targeted testing method developed at UNC-Chapel Hill that broadens researchers’ abilities to identify the hazardous compounds.
The Environmental Protection Agency (EPA) keeps a list of more than 14,000 known or potential per-and polyfluoroalkyl substances (PFAS). Called “forever chemicals” for how long the molecules take to break down, PFAS can be found just about everywhere, and have been linked to health issues like cancer and infertility.
PFAS are potentially hazardous to people and animals, so detecting them is vital. That’s why Erin Baker, associate professor of chemistry within the UNC College of Arts and Sciences, and her lab are expanding testing methods to find them — efforts that were recently published in Science Advances.
Researchers collaborating with Baker’s lab collected samples from North Carolina’s Cape Fear River in 2016. Using this new detection method, they tested the samples and found 47 different PFAS. Of those, 11 had not been previously detected in the river, and eight had not been detected anywhere outside of a lab.
“Eight of them weren’t on the EPA’s list of PFAS, which makes us think there are many more PFAS than we previously thought,” Baker says.
Expanding the search
For years, PFAS contaminants like GenX have been found in drinking water originating from the Cape Fear River, making it an ideal testing site for Baker and her team. Some of this pollution has been directly linked to production at the Chemours Fayetteville Works site, where chemicals are manufactured. Surrounding residents rely on testing conducted by scientists to understand what types of compounds they are being exposed to.
“Current testing methods used by the EPA can only find the PFAS that we already know exist,” Baker says. “That means we have to rely on chemical companies to provide a list of what they manufacture and hope those samples are comprehensive.”
PFAS are commonly detected using liquid chromatography-mass spectrometry, a method that looks at the mass, charge, and polarity of ions — positively or negatively charged molecules. The EPA uses targeted mass spectrometry, which requires matching PFAS found in people or the environment with “standards” — PFAS chemicals created in a lab for testing purposes. It’s like combing through a word search puzzle and only being able to search for a specific set of words. Baker’s lab has developed a non-targeted approach, which allows them to search for any word in a puzzle.
“There are so many known PFAS that standards don’t exist for many of them,” says Kaylie Kirkwood-Donelson, who led the study when she was an NC State University PhD student in Baker’s lab. “Having a non-targeted approach lets us have an open-ended search for known and unknown compounds.”
The non-targeted approach uses ion mobility spectrometry (IMS) to look at how ions move. To do this, ions are placed in gas and an electric field is added. The electric field causes the ions to move differently based on their individual charges. An ion’s size and shape affect the speed at which it moves through the gas, with larger ions moving slower than smaller ones. Information on an ion’s size and shape provides more insight into the structure of the molecule. And in this case, can help researchers determine if a molecule could be considered PFAS.
Sharing the results
As researchers investigate PFAS in the Cape Fear River, the number of known chemicals present in the water continues to grow. More testing is needed to understand the quantities and how toxic they are to people and animals.
“It’s also very important to expand non-targeted testing for PFAS,” says Kirkwood-Donelson, who is now a chemist for the National Institute of Environmental Health Sciences. “Even in this study, there were still some molecules that we could not figure out the chemical structures for, so we believe there are more PFAS in the Cape Fear River to be discovered.”
Baker’s lab is working to streamline their non-targeted testing process to make it more efficient. The technology and equipment needed to conduct ion mobility spectrometry is expensive, but more PFAS-focused labs are getting the special tools needed.
In the meantime, Baker’s lab will keep testing samples from the Cape Fear River. They are currently comparing some collected before and after environmental regulations were enacted by the state in 2019.
Their work is getting attention from news and science outlets, and the United Nations has even weighed in on the issue, issuing letters to Chemours, the U.S. government, and other involved parties stating “serious concern regarding human rights and environmental impacts.” Baker hopes this attention will inspire more investigation by scientists and regulation from government agencies.
“If industries create molecules that they don’t tell the public about, and we only test for the molecules they do tell us about, we could be missing things,” says Baker. “We need to use non-targeted testing to have more information on what our communities are being exposed to.”
Erin Baker is an associate professor in the Department of Chemistry within the UNC College of Arts and Sciences.
Kaylie Kirkwood-Donelson is a former PhD student in Erin Baker’s lab who recently graduated from NC State University. She is now a chemist for the National Institute of Environmental Health Sciences.