Eating just one serving of freshwater fish each year could have the same effect as drinking water heavily contaminated with “forever chemicals” for an entire month, according to a new study.
The equivalent amount of water for a month would be contaminated at levels 2,400 times greater than those recommended by the Environmental Protection Agency (EPA) drinking water health advisories, according to the study, published Tuesday in Environmental Research.
The research added that locally caught freshwater fish are much more contaminated than commercial catches with perfluorinated and polyfluorinated substances (PFAS), so-called “forever chemicals” that are known to persist in the body and environment.
PFAS are key ingredients in jet fuel firefighting foam, industrial discharges, and many household products, including certain types of food packaging. For decades, they have seeped into drinking water supplies while contaminating irrigated crops and the fish that inhabit local waterways.
Fish consumption has long been identified as a route of exposure to PFAS, according to the study. Researchers first identified such contamination in catfish that inhabited the Tennessee River in 1979.
“Food has always been kind of a hypothesis for how most people are exposed to PFAS compounds,” corresponding author David Andrews, a senior scientist at the Environmental Working Group, told The Hill.
But Tuesday’s study is the first analysis to link US fish consumption to PFAS blood levels, while also comparing PFAS levels in freshwater fish to commercial shellfish samples. , the authors explained.
To draw their conclusions, the researchers evaluated the presence of different types of PFAS in 501 fish fillet samples collected in the US between 2013 and 2015.
These samples were acquired through two EPA programs: the 2013-2014 National River and Stream Assessment and the 2015 Great Lakes Human Health Fish Fillet Tissue Study.
According to the study, the mean level of total target PFAS in fish from rivers and streams was 9,500 nanograms per kilogram, while the mean level in the Great Lakes was 11,800 nanograms per kilogram. These levels indicate that consumption of such fish “is potentially a significant source of exposure” to PFAS, the authors determined.
While the samples included many types of chemicals forever, of which there are thousands, the largest contributor to total PFAS levels was the compound known as PFOS, responsible for about 74 percent of the total, the researchers found.
Although PFOS has been largely eliminated from manufacturing, it used to be the main ingredient in Scotchgard fabric protectant and remains in the environment.
PFOS is so potent that eating just one serving of freshwater fish would be equivalent to drinking a month of water contaminated with PFOS at levels of 48 parts per billion, according to the study.
“The extent to which PFAS has contaminated fish is staggering,” first author Nadia Barbo, a Duke University graduate student, said in a statement. “There should be a single health protective fish advisory for freshwater fish across the country.”
Although scientists may not know precisely how people are exposed to PFAS, the study “clearly indicates that for people who consume freshwater fish, even very infrequently, it is likely to be a significant source of their exposure.” Andrews said.
Of the 349 samples tested in the National River and Stream Assessment, only one sample did not contain detectable PFAS, the authors determined.
All 152 fish samples tested in the Great Lakes study had detectable PFAS and had “higher overall levels of PFOS” compared to those in the national assessment.
“PFAS contamination may be of particular concern to the Great Lakes ecosystem and the health of people who depend on fisheries in the Great Lakes for their livelihoods and cultural practices,” the authors noted.
Contamination in the Great Lakes, as well as other lakes and ponds, can be comparatively greater than PFAS contamination in rivers and streams because these basins do not circulate as frequently, according to Andrews.
“The water doesn’t come out that fast,” he said.
Mean levels of total PFAS detected in freshwater fish were 278 times higher than those in commercially relevant fish tested between 2019 and 2022.
“It’s amazing how different they are,” Andrews said.
Retail fish data comes from the 2019-2021 Food and Drug Administration Total Diet Study data sets, as well as specific sampling of shellfish conducted in 2022.
Some commercially caught fish may be less contaminated because they are grown in controlled aquaculture environments, Andrews explained. Meanwhile, large-scale ocean fishing often occurs further offshore, where PFAS contamination would be more dilute, he added.
Andrews acknowledged, however, that data on commercially caught fish is much more recent than figures for freshwater contamination.
He also acknowledged that with the industrial phase-out of PFOS production, “contamination levels in rivers and streams appear to be decreasing, which is important.”
“At the same time, levels are still so high that any consumption of fish is likely to affect serum levels,” Andrews said. “But they are moving in the right direction, which I think is good news, at least in terms of rivers and streams.”
While this study did not test whether PFAS uptake is worse in some fish compared to others, Andrews pointed to recent evidence showing that even small fish with a short lifespan can accumulate dangerous amounts of these compounds.
Last week, the Michigan Department of Health and Human Services updated its “Eat Safe Fish” guidelines to limit the amount of rainbow smelt that should be eaten, based on elevated PFOS levels.
Rainbow smelt, a small, silvery fish with short life cycles, is “low on the food chain and generally does not bioaccumulate chemicals,” Michigan Live reported.
The Hill has contacted the Michigan PFAS Action Response Team, a group at the Department of Health and Human Services that works on the issue of Great Lakes pollution and oversees the Eat Safe Fish program, for comment on the study.
Compared to commercially caught fish, local consumption of freshwater fish can be difficult to quantify, as “significant variability exists with respect to dietary fish intake,” the study authors acknowledged.
But the Centers for Disease Control and Prevention has determined that the general population eats about 18 grams per day of fish, with the highest consumption among men and adults ages 31 to 50, according to the study.
High fish consumption (eating one or more meals of fish per week) is typical among fishermen, people living along shorelines or lakes, communities for whom fishing is culturally important, and immigrants who they come from countries where fish is a staple food, the authors noted.
Therefore, the researchers characterized PFAS exposure in freshwater fish as “a textbook case of environmental injustice” in which certain communities are “harmed excessively.”
Contamination of this particular food source “threatens those who cannot afford to buy commercial seafood,” the authors emphasized in a statement accompanying the study.
Andrews stressed the need for both guidance for fishermen and action on “this environmental justice issue” from a federal level.
Attention to this issue, he added, must address “this contamination of a protein source for many communities that depend on it for both subsistence and cultural reasons.”
