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Study: Forever chemicals abundant in fish from contaminated rivers, lakes

A fisherman stands on a dock with a fishing pole.
Will Atwater/NC Health News
Daryl Mouring reels in a puffer fish on the Newport River Pier, Morehead City, N.C. When he's not out at the coast, sometimes he drops his line into a freshwater lake or stream near home.

When Raleigh resident Daryl Mouring isn’t making his semi-annual southward trek to Beaufort to enjoy saltwater fishing, he can still be found casting his line closer to home — at Lake Wheeler or Falls Lake.

Never at nearby Lake Crabtree, though.

“They tell you not to eat the fish in Lake Crabtree because something leaked into the water,” Mouring said. “I heard there are big fish in the lake, but I’m not fishing there because I can’t eat them.”

Maybe anglers such as Mouring should reconsider eating any freshwater fish they catch — if their favorite spot is near or downriver from an industrial site currently or historically contaminated by per- and polyfluoralkyl substances (PFAS).

New research estimates that anglers who eat fish from waters contaminated by PFAS, also called “forever chemicals,” may be ingesting large doses of the chemicals. It suggests that local authorities notify fishers of contamination in the state’s waterways to help them make better decisions about where to cast their lines.

Researcher David Andrews from the Environmental Working Group, an advocacy organization, worked with a researcher from Duke University to look at hundreds of samples of freshwater fish caught from around the United States, including North Carolina. They found fish with detectable levels of PFAS in all states of the continental U.S.

Out of the 353 samples collected across the lower 48 states during the federal National Rivers and Streams Assessment, performed in 2013 and 2014 by the Environmental Protection Agency, only one fish sample did not have a measurable amount of PFAS in its flesh. A separate study of Great Lakes fish found that each of the 152 fish samples contained PFAS.

This has implications for people who fish to eat, whether for subsistence or because they enjoy a plate of fresh-caught bass or catfish.

“We calculate out that even for the median concentration of PFAS-contaminated fish, that eating a single serving is equivalent to [drinking] a month of contaminated drinking water,” Andrews said.

Eating those fish could dramatically increase the amount of PFAS people have circulating in their bloodstreams.

Persistent, toxic

Recent years have seen significant growth in the knowledge and understanding about how the thousands of per- and polyfluoroalkyl substances used in industry affect human health. Because of their strong carbon-flourine bonds, PFAS can be tough to break down and have taken on a reputation as forever chemicals. Increasingly, studies show their presence in fish and people.

Researchers have found evidence that suggests a link between PFAS exposure and weaker antibody responses against infections in adults and children, elevated cholesterol levels, decreased fetal and infant growth, and kidney cancer in adults, among other problems.

There’s also an increasing amount of data showing that people who drink water tainted with PFAS have higher levels of the chemicals in their blood. There’s so much data about how diet can increase blood levels of PFAS that the European Food Safety Authority has concluded that diet is the “primary source of PFAS exposure for most people, with fish, meat, fruit and eggs as significant contributors.”

A map of where samples were taken from fish in North Carolina waterways. Credit: Environmental Working Group
A map of where samples were taken from fish in North Carolina waterways. Credit: Environmental Working Group

Earlier research has shown that PFAS can accumulate in fish, especially those swimming in bodies of water polluted by industrial runoff and emissions. One study done in 1979 found that catfish near a Tennessee River 3M manufacturing plant had eye-popping quantities of organic fluoride in their flesh, and a more recent study found that sport fish caught in the Great Lakes and/or near PFAS contaminated areas had higher levels of PFAS than ocean-caught fish found in grocery stories.

Another study examining anglers who fished in Syracuse’s Onondaga Lake found PFAS levels in their blood that were as much as 26 times higher than the U.S. median.

To do their study, Andrews, his Duke University colleague Nadia Barbo and their co-authors combed through a database of fish flesh assembled during two federal fish sampling studies. They went looking for other researchers who used those fish samples and found that they were the first to really look for PFAS in them.

Andrews said they were trying to understand how levels of PFAS in freshwater fish across the United States compared with those in farmed fish that people can buy in grocery stores.

“How big of an impact could consumption of freshwater fish have on blood serum levels [of PFAS], with the understanding that across this country, everyone is overexposed to these compounds?” Andrews asked. “Finding ways to reduce exposure is important.”

Catfish, bass, perch

Millions of people across the U.S. fish for fun, relaxation and food. In North Carolina alone, data from the state Department of Environmental Quality shows that more than 350,000 people were issued inland fishing licenses from July 2021 to June 2022. Those licenses don’t specify where a person is going to fish, only that they’re cleared to fish in freshwater ponds, creeks, lakes and rivers. Some of those might have high levels of PFAS, but right now there’s no advisories on any of the state’s waterways warning anglers about PFAS contamination.

Adding advisories is one of the recommendations the study’s authors are making.

Jordan Lake, part of the Cape Fear River basin that has documented PFAS contamination, is one of North Carolina’s most popular fishing locales; it’s known for its channel catfish.

Signs warn fishers at Lake Crabtree of potential PCB contamination. Researchers say state environmental officials should also warn anglers about freshwater lakes and streams that have high levels of PFAS. Photo credit: Catherine Clabby

Channel catfish, largemouth and smallmouth bass, walleye and perch were among the types of fish sampled. Researchers found that levels of PFAS were as much as 2.7 times higher in fish caught in urban areas than in rural ones, especially those caught near industrial sites.

Andrews said that bass species — one of the most common in the sample database — had some of the highest levels, on average.

“There are some locations that likely have much higher concentrations,” Andrews said.

Eating fish from one of those highly contaminated locations could end up being the equivalent of drinking “months of contaminated drinking water in just a single serving,” Andrews added.

Even though PFAS are becoming more ubiquitous in the environment, only a quarter of U.S. states have advisories for anglers with warnings about consumption. North Carolina is not one of those states.

The group calculated that eating contaminated freshwater fish once a month could more than triple the serum levels of PFOS (perfluorooctanesulfonic acid, a type of PFAS that used to be the main ingredient in Scotchgard) in a person’s blood.

Farmed, saltwater fish safer

The good news is that saltwater catch, such as tuna and shrimp, had almost no detectable PFAS — likely a function of the greater dilution of chemicals in ocean waters.

Andrews noted that PFAS were largely undetectable in farmed catfish when compared with wild-caught fish.

“Freshwater fish farms actually use pumped groundwater and aren’t relying on contaminated surface water to raise those fish,” Andrews said. He also believed that “greater control in the water quality and the feeds that are given to those fish” contributed to the near-absence of PFAS in the farmed fish.

The study authors noted that the Centers for Disease Control and Prevention found that the general population consumes about 14 pounds of fish per year, with men and adults aged 31 to 50 eating the most fish.

The researchers also noted that there are potential health disparities for people who go fishing because they can’t afford grocery store fish or who fish because it’s part of their cultural heritage.

“I’m not aware of any other activity or foods that someone could consume that would expose them to anywhere near this amount of PFAS,” Andrews said. “Based on what we know about the health concerns, that’s alarming, even if it’s not in the majority of the population.”

North Carolina Health News is an independent, non-partisan, not-for-profit, statewide news organization dedicated to covering all things health care in North Carolina. Visit NCHN at northcarolinahealthnews.org.