By Greg Barnes
While sampling the Yadkin-Pee Dee River’s food chain for perfluorinated compounds known as PFAS, N.C. State University researchers managed to capture a robust redhorse that was about to spawn.
Capturing the fish, a member of the sucker family, was no easy task. According to N.C. Wildlife Commission, an estimated 62 reproductive adult robust redhorse are in North Carolina waters, almost exclusively in the Yadkin-Pee Dee River. The state lists the fish as endangered.
N.C. State researchers think that PFAS — scientifically known as per- and poly-fluoroalkyl substances — could be at least partly behind the fish’s demise.
They also think that PFAS could be threatening human health and the ecosystem of the Yadkin-Pee Dee, even though there are no known sources of the man-made compounds along the river.
PFAS in the food chain
During a study that began in 2015, the researchers found PFAS in every step of the food chain, from water and sediment to algae, plants, insects, crayfish, mollusks and fish.
The researchers also found that the higher up the food chain they looked, the greater the concentration of PFAS. Sampling was conducted at five sites along the river, three in North Carolina and two in South Carolina.
The findings have significant implications for the health of the river’s ecosystem and humans who eat the fish that come from it, said Greg Cope, a distinguished professor at N.C. State and co-principal investigator of the study, which was published June 2 in Environmental Science & Technology.
“I think the implications are these things (PFAS) are widespread in the system and they are throughout the food web, and they have both environmental health and human health implications,” said Cope, who shared lead investigator duties with researcher Tom Kwak of N.C. State.
PFAS and health effects
Little is known about the human health effects of the many types of PFAS. But research has found that two of the oldest and most widely studied PFAS — called PFOA and PFOS — can cause immunological disorders and liver, testicular and kidney cancer in laboratory animals. Some studies have linked PFOA to cancer and other diseases in humans
The use of PFOA and PFOS has been all but phased out in the U.S. in favor of shorter carbon-chain perfluorinated compounds that are thought by some to be more environmentally friendly. But during Cope’s research, the two legacy compounds were detected at the highest concentrations of all 14 types of PFAS the team had measured.
The researchers sampled biofilm, which Cope described as “the soupy mixture of algae and bacteria that sticks to your boat,” and found the largest concentrations of 10 of the 14 PFAS measured. Biofilm is the base resource for all life further up the food chain.
According to the study, aquatic insects, which primarily eat biofilm, had the greatest accumulation of all 14 PFAS.
“This confirms a strong trophic link, or step in the food chain, showing how PFAS transfers from biofilm to insects, which are then eaten by freshwater fish,” Cope wrote in a news release announcing the study’s release.
PFAS are used in many common household products, including Teflon pans, stain-resistant carpets, weather gear and food packages — virtually everything that keeps food from sticking or repels liquid. They are known as “forever chemicals” because they accumulate in the environment and don’t break down easily. At this point, since they started to be widely produced in the 1940s, virtually everyone in America has some level of PFAS in their system.
No known PFAS sources
What is perhaps most surprising about the study is that PFAS were found in a river that, unlike the Cape Fear, has no known sources for it. In the lower Cape Fear, enormous concentrations of GenX and other PFAS were detected below the Chemours chemical plant in Bladen County.
Chemours, previously DuPont, has been found responsible for polluting the river and private wells surrounding the plant. DuPont had made PFOA at the plant before switching to the shorter chain GenX in 2009. Chemours spun off from DuPont and took over the plant’s operations in 2015.
High concentrations of PFAS have also been found in the Cape Fear River near Greensboro and in the Haw River, which flows into Jordan Lake. Greensboro, Pittsboro, Sanford, Fayetteville and Wilmington are among cities that have detected high concentrations of PFAS in their drinking water at certain times.
Yet the Yadkin-Pee Dee River is relatively free of PFAS compounds. The study did find two “hot spots” downstream of the Rocky River, which drains part of the watershed from Charlotte, and farther downstream in South Carolina.
While those two sampling sites found high accumulations of PFAS in insects and other aquatic life, the highest concentration of PFOA in the river itself measured only 8.07 parts per trillion — far below the U.S. Environmental Protection Agency’s health guideline for drinking water of 70 parts per trillion. Samples taken elsewhere were below limits of quantitation.
Cope said researchers aren’t sure where the PFAS detected in the river’s food chain is coming from. It could be emerging from a combination of wastewater treatment plant effluent, so-called land farms where sewer sludge is placed, landfills and other sources, Cope said. It could also be airborne, he said.
Cope said the N.C. State study, written by then-graduate student Tiffany Penland, is believed to be the first to examine PFAS in the food chain of a river with no known industrial sources of the compounds.
Cope said he hopes it will be used by other researchers and state and federal agencies to take a closer look at the environmental and human health effects of PFAS’ accumulation in the food chain.
The robust redhorse
All of which brings us back to the endangered robust redhorse and an N.C. State report dated June 13. The report is titled “How PFAS may be threatening the conservation of an imperiled fish.”
“There are several possible explanations for their decline, including man-made structures that cut off access to breeding areas, poor water quality, and pollution,” the new report says, referring to PFAS and the study by Cope’s team.
Because the robust redhorse is in such peril, Cope’s team collected tissue samples of a close cousin, the common notchlip redhorse, which has a similar diet and occupies the same areas. The researchers found that those fish were also contaminated with PFAS.
The robust redhorse that Cope’s team did manage to capture — and later release — contained 10 types of PFAS in its eggs, indicating the maternal transfer of the contamination to the eggs and “potentially impacting their fertility, fecundity, and the early development of young redhorse,” the new report says.
“The robust redhorse is the most critically endangered of the several imperiled species present in the Yadkin-Pee Dee, and this study highlights how pollutants like PFAS may be affecting their decline and need to be considered in future management strategies for this, and other, imperiled aquatic species,” the report concludes.