Scientists with the N.C. Per- and Polyfluoroalkyl Substances Testing Network racked up a lot of miles last year. From April through October 2019, researchers from Duke University and N.C. State University visited all of the state’s 191 municipal drinking water systems to collect raw water samples, which they then analyzed for dozens of so-called “forever chemicals.”
What made those scientists spend so much time on the road, and what made the N.C. General Assembly allocate over $5 million to fund their work in 2018? According to Detlef Knappe, co-lead of the N.C. PFAST Network’s testing team and a professor at N.C. State, it all goes back to Wilmington.
Measurements in 2013-15 by the federal Environmental Protection Agency, Knappe explains, detected PFAS concentrations of just 27 parts per trillion near the intake for the coastal North Carolina city’s drinking water. But a 2019 analysis of preserved water samples from that period using better methods found total PFAS levels exceeding 100,000 ppt, with the contamination tied to a Chemours Co. chemical manufacturing plant in Fayetteville 80 miles upstream of the intake. The EPA regards combined PFAS chemicals at 70 ppt or greater as potentially hazardous to human health.
His team’s widespread testing, Knappe says, is meant “to provide greater confidence about the water quality that enters drinking water systems around the state — and to avoid surprises like we had in Wilmington.”
The N.C. PFAST Network’s most recent results, publicly released in July, suggest that no such surprises are lurking in Western North Carolina’s water supplies. None of the systems that serve readers in the Mountain Xpress coverage area exceeded the EPA’s advisory limit for PFAS chemicals. Nor did any system have more than 10 ppt of any individual PFAS, the level at which a 2019 consent order between Chemours, the N.C. Department of Environmental Quality and Cape Fear River Water required the company to provide filtration in the communities surrounding the plant.
However, the researchers found that even WNC’s most pristine mountain waters weren’t completely devoid of contamination. Five area systems, respectively serving Asheville, Black Mountain, Mars Hill, Old Fort and Sylva, all had detectable levels of at least one PFAS compound.
In the wild
Lee Ferguson, Knappe’s collaborator on the testing effort and a professor at Duke, emphasizes caution in interpreting WNC’s PFAS results. “There’s a huge difference between detectable and adverse to health,” he explains. “It is absolutely clear from the mapping data that the sites in Western North Carolina are considerably lower than the sites in Central and in some of Eastern North Carolina.”
The team’s analytical methods are also extremely sensitive, capable of detecting 1 nanogram of a given chemical in a liter of water — the equivalent of one penny in a stack of coins nearly 944,000 miles high. While researchers take great care to validate their results, Ferguson says, false positives are certainly possible when measuring such tiny quantities.
Nevertheless, Knappe says the results show how potentially toxic human-made chemicals have become omnipresent in the environment. The substances discharged by a manufacturing plant in Fayetteville can be carried away on the wind, then deposited hundreds of miles away in protected watersheds through rain. “I don’t know if there’s a place on the globe that doesn’t have any PFAS,” he says.
And because PFAS compounds contain many bonds between carbon and fluorine, one of the strongest linkages in chemistry, they don’t break down easily. The federal National Institute of Environmental Health Sciences says researchers have been “unable to estimate” how long PFAS chemicals can persist.
But Knappe suggests that Western North Carolina residents should likely be more concerned about sources of PFAS within their own homes than about contamination of water supplies. Carpets, microwave popcorn bags and furniture stain repellents, he points out, all often make use of PFAS compounds for their nonstick qualities. People can then ingest the chemicals through eating food packaged with PFAS or inhale them as part of indoor dust.
“I can measure cocaine in Raleigh drinking water at picograms per liter [a thousand times less concentrated than the PFAS detection limit], and I don’t know whether that’s exciting or not,” Knappe says. “If you have a method that’s supersensitive, you can find just about anything, but the question is if it’s relevant from a health perspective.”
The local officials responsible for overseeing WNC’s municipal drinking water systems take a similar view of the N.C. PFAST Network’s results. All of those contacted by Xpress said the low PFAS levels detected in their raw water supplies were not a cause for concern.
“There’s nothing but trees and mountainsides around our watershed,” says Nathan Bennett, town manager for Mars Hill, in a representative response. At a total PFAS concentration of 2.7 ppt — less than 4% of the EPA’s 70 ppt advisory level — he says “there’s no reason to pursue it with the results they’ve given us.”
Leslie Carreiro, who manages water production and quality for the city of Asheville, notes that the only PFAS compounds detected in the city’s raw water sources were from the Mills River, not the protected North Fork Reservoir northeast of the city near Black Mountain that provides about 70% of Asheville’s water. The Mills River is primarily fed from the Pisgah National Forest, she adds, with no known local sources of PFAS.
And Sylva’s Tuckaseigee Water & Sewer Authority questions the validity of testing at its water intake, which found 1.2 ppt of GenX, a chemical with many of the same properties as PFAS. Executive Director Daniel Manring notes that the authority shares its water source with Western Carolina University’s water treatment plant, for which researchers found no PFAS compounds.
“It does not make any sense that WCU would be absent while we have a ‘reportable’ result,” Manring argues. “The other question is whether 1.2 ppt is actually reportable.”
Ferguson acknowledges that the PFAST team’s results to date are limited, based as they are on just one round of sampling. He says the researchers intend to take further measurements to better understand how PFAS levels fluctuate over time, particularly in water systems where the team previously detected the chemicals: “A single snapshot, or even two snapshots, isn’t necessarily sufficient.”
Updated at 9:53 a.m. on Aug. 25 to provide additional clarification around the 10 ppt threshold named in the consent order between Chemours Co., NCDEQ and Cape Fear River Water.