Consuming Fish May Increase Risk of Exposure to Multiple Chemicals.

Consuming Fish May Increase Risk of Exposure to Multiple Chemicals
A new study found that toxic chemicals, including those that were banned in the 1970s, were still present in freshwater fish in US water bodies, posing health risks to consumers.
Fish is generally considered to be a healthy addition to a balanced diet, particularly when it is substituted for red meat. Despite being good sources of protein and omega-3 fatty acids, some fish pose a risk to human health, according to a new study coauthored by School of Public Health researchers.
Published in the journal Environmental Research, the study found that freshwater fish in the United States—which include trout, catfish, and various types of bass, among other species—contain multiple toxic chemicals at levels high enough to be harmful to human health. Several of these observed contaminants, including polychlorinated biphenyls (PCBs) and certain pesticides, were banned in the US decades ago.
The study results also indicated there is a widespread presence of mercury and per- and polyfluoroalkyl substances (PFAS) in freshwater fish tissue in US waters. Both of these chemicals posed health risks to fish consumers, even at low levels.
These findings underscore the importance of pollution prevention and the need for continued and expanded monitoring of contaminants in the US at the state and federal levels—the opposite of what is expected to occur under the second Trump administration, which has begun to roll back federal environmental protections and air and quality standards that occurred under the first Trump administration.
“We are in a deep hole with respect to the chemical contamination of our food chain and our broader environment, and we desperately need to stop digging,” says second author and alum Caredwen Foley (SPH’21), who completed the MPH program studying environmental health. “Pollution prevention can help us turn off the tap and stop making a bad problem worse.”
For the study, Foley, lead author Pianpian Wu of Dartmouth College, and additional researchers from BUSPH and Dartmouth utilized national data from three freshwater fish monitoring programs led by the US Environmental Protection Agency (EPA) to examine the co-occurrence of chemicals in fish in lakes, ponds, streams, and rivers across the country, using an EPA screening framework to gauge potential human health risks from exposure to these chemicals. Most research—and regulatory standards for safe levels of fish consumption—are determined based on exposure to only one chemical at a time, rather than multiple chemicals simultaneously. For example, many states set fish consumption advisories based primarily on mercury levels.
But the findings showed the presence of both emerging and long-term contaminants in freshwater fish, independent of mercury levels. Whole fish, in particular, had greater concentrations of chemicals.
“Our analysis shows that organic contaminants co-occur in environmental media, so you’re generally not being exposed to one at a time,” says Foley, emphasizing the need for risk-based government standards for air, water, soil, and food that account for this co-occurrence. “National monitoring programs have expanded the list of chemicals they test for over the years, which is fantastic. But those programs are going to require continued investment, and robust academic and public sectors where researchers can count on the continuity of institutional priorities and funding.”
Monitoring chemicals at the state level is also crucial. The Toxics Use Reduction Act (TURA) Program in Massachusetts has proven effective at gathering data about industrial chemical use in the Commonwealth. TURA requires manufacturers using large volumes of toxic substances to report on the use of specific listed toxic chemicals and to make plans to reduce their use of these chemicals. The program also provides free and confidential pollution prevention technical assistance to manufacturers and businesses throughout the Commonwealth that use toxic or hazardous chemicals and substances.
Many of the chemicals found in fish persist in the environment for years. Even though PCBs and other “legacy” chemicals were banned in the 1970s, they continue to cycle through the environment in water and in equipment. They are linked to cancer and respiratory issues in humans, and may also heighten the risk of complications with the immune, nervous, and reproductive systems. Exposure to emerging chemicals such as PFAS are also concerning because they are present at lower levels and require more robust detection efforts.
When providing guidance on fish consumption, health officials should not only take nutritional benefits into account, but also consider the cultural significance of fish, the researchers note. In addition to sources of food, fish are also religious and artistic symbols in many cultures, as well as crucial drivers of economies in coastal communities.
“Fish is important nutritionally, ecologically, economically, and culturally—abandoning our waterways and those who rely on them isn’t an option,” Foley says. “Communities living with contamination deserve remediation so they have access to safe air, water, and food. We need to prevent further contamination by reducing and, wherever possible, eliminating the use of toxics, particularly in large-scale industrial applications.
“Consumers can’t fix this alone—it’s going to have to be driven by the behavior of major institutions and economic actors, and that means we need policy that sets and enforces meaningful, health-protective standards.”
At SPH, the study was also coauthored by Wendy Heiger-Bernays, emeritus clinical professor of environmental health. The study’s senior author is Celia Chen of Dartmouth College.
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