Careful With That Wild-Caught Tuna

It started with the cats. In the seaside town of Minamata, on the west coast of the most southerly of Japan’s main islands, Kyushu, the cats seemed to have gone mad — convulsing, twirling, drooling, and even jumping into the ocean in what looked like suicides. Locals started referring to “dancing cat fever.” Then the symptoms began to appear in their newborns and children.

Now, nearly 70 years later, Minimata is a cautionary tale of industrial greed and its consequences. Dancing cat fever and “Minamata disease” were both the outward effects of severe mercury poisoning, caused by a local chemical company dumping methylmercury waste into the local bay. Between the first recognized case in 1956 and 2001, more than 2,200 people were recognized as victims of the pollution, which entered the population through their seafood-heavy diets. Mercury is a bioaccumulator, meaning it builds up in the tissues of organisms as it moves up the food chain from contaminated water to shellfish to small fish to apex predators: Tuna. Cats. People.

In 2013, 140 countries, including the U.S., joined the Minamata Convention, pledging to learn from the mistakes of the past and to control the release of mercury into the environment. That included, explicitly, mercury in emissions from “coal-fired power plants.” Last month, however, the U.S. Environmental Protection Agency retreated from the convention by abandoning the 2024 Mercury and Air Toxics Standards, which had reduced allowable mercury pollution from coal-fired plants by as much as 90%. Nearly all of the 219 operating coal-fired plants in the U.S. already meet the previous, looser standard, set in 2012; Trump’s EPA has argued that returning to the older rules will save Americans $670 million in regulatory compliance costs by 2037.

The rollback — while not a surprise from an administration that has long fetishized coal — came as a source of immense frustration to scientists, biologists, and activists who’ve dedicated their careers to highlighting the dangers of environmental contaminants. Nearly all human exposure to methylmercury in the United States comes from eating seafood, according to the EPA, and it’s well-documented that adding more mercury to the atmosphere will increase levels in fish, even those caught far from fenceline communities.

“Mercury is an extremely toxic metal,” Nicholas Fisher, an expert in marine pollution at Stony Brook University, told me. “It’s probably among the most toxic of all the metals, and it’s been known for centuries.” In his opinion, it’s unthinkable that there is still any question of mercury regulations making Americans safer.

Gabriel Filippelli, the executive director of the Indiana University Environmental Resilience Institute, concurred. “Mercury is not a trivial pollutant,” he told me. “Elevated mercury levels cost millions of IQ points across the country.” The EPA rollback “actually costs people brain power.”

When coal burns in a power plant, it releases mercury into the air, where it can travel great distances and eventually end up in the water. “There is no such thing as a local mercury problem,” Filippelli said. He recalled a 2011 study that looked at Indianapolis Power & Light, a former coal plant that has since transitioned to natural gas, in which his team found “a huge plume of mercury in solids downwind” of the plant, as well as in nearby rivers that were “transporting it tens of kilometers away into places where people fish and eat what they catch.”

Earthworms and small aquatic organisms convert mercury in soils and runoff into methylmercury, a highly toxic form that presents the most danger to people, children, and the fetuses of pregnant women as it moves up the food chain. Though about 70% of mercury deposited in the United States comes from outside the country — China, for example, is the second-greatest source of mercury in the Great Lakes Basin after the U.S., per the National Oceanic and Atmospheric Administration — that still leaves a significant chunk of pollution under the EPA’s control.

There is, in theory, another line of defense beyond the EPA. For recreational fishers, of whom there are nearly 60 million in the country each year, state-level advisories on which waterways are safe to fish in based on tests of methylmercury concentrations in the fish help guide decisions about what is safe to eat. Oregon, for example, advises that people not eat more than one “resident fish,” such as bass, walleye, and carp, caught from the Columbia River per week — and not eat any other seafood during that time, either. Forty-nine states have some such advisories in place; the only state that doesn’t, coal-friendly Wyoming, has refused to test its fish. One also imagines that safe waterways will start to become more limited if the coal-powered plants the Trump administration is propping up forgo the expensive equipment necessary to scrub their emissions of heavy metals.

“It’s not something where you’re going to see a dramatic change overnight,” Tasha Stoiber, a senior scientist with the Environmental Working Group, a research and advocacy nonprofit that focuses on toxic chemicals, told me. “But depending on the water body that you’re fishing in, you want to seek out state advisories.”

For people who prefer to buy their fish at the store, the Food and Drug Administration sets limits on the amount of mercury allowed in commercial seafood. But Kevin McCay, the chief operations officer at the seafood company Safe Catch, told me the FDA’s limit of 1 part per million for methylmercury is outrageously high compared with limits in the European Union and Japan. “It has to be glowing red before the FDA is actually going to do anything,” he said. (Watchdog groups have likewise warned that the hemorrhaging of civil servants from the FDA will have downstream consequences for food safety.)

McCay also told me that he “certainly” expects mercury levels in the fish to rise due to the EPA’s decision. Unlike other canned tuna companies that test batches of fish, Safe Catch drills a small test hole in every fish it buys to ensure the mercury content is well below the FDA’s limits. (Fish that are lower on the food chain, like salmon, are the safest choices, while fish at the top of the food chain, like tuna, sharks, and swordfish, are the worst.)

The obsessive oversight gives the company a front-seat view of where and how methylmercury is working its way up the food chain, and McCay worries his company could face more limited sourcing options in the coming years if policies remain friendly to coal. (An independent investigation by Consumer Reports in 2023 found that even fish sourced by an ultra-cautious company like Safe Catch contain some level of mercury. “There’s probably no actual safe amount,” McCay told me, recommending that customers should eat a diverse range of seafood to limit exposure.)

Even people who don’t eat fish should be concerned, though. That’s because, as Filippelli told me, “a lot of [contaminated] fish meal is being incorporated into pet food.”

There are no regulatory standards for mercury in pet foods. But avoiding mercury is not as simple as bypassing the tuna-flavored kibble, Sarrah M. Dunham-Cheatham, who authored a 2019 study on mercury in pet food, told me. Even many brands that don’t list fish among their ingredients contain fish meal that is high in mercury, she said.

Different species also have different sensitivities to mercury, with chimpanzees and cats being among the most sensitive. “I don’t want to be alarmist or scare people,” Dunham-Cheatham said. But because of the issues with labeling pet food, there isn’t much to be done to limit mercury intake in your pets — that is, short of dealing with the emissions on local and planetary scales. “We’re expecting there to be more emissions to the atmosphere, more deposition to aquatic environments, and therefore more mercury accumulated into proteins that will go into making the pet foods,” she said.

To Fisher, the Stony Brook professor, the Trump administration’s decision to walk back mercury restrictions makes no sense at all. The Ancient Romans understood the dangers of mercury; the dancing cats of Minamata are now seven decades behind us. “Why should we make the underlying assumption that the mercury is innocent until proven guilty?” he said.