Farmed fish now accounts for more than half of the seafood eaten worldwide, and most farmed species are fed fishmeal or fish oil. That means additives used to stabilize fishmeal can enter the food chain. One such additive is ethoxyquin, an antioxidant that Cargill promoted in the late 1960s as a way to stop fishmeal from catching fire in ship holds. The problem was real: fishmeal had been tied to at least 90 ship and plant fires from the 1950s through the 1970s, according to historical coverage collected by The Outlaw Ocean Project.
The chemical was effective, and pressure to treat fishmeal grew. By 1976, the U.S. Coast Guard required it on fishmeal shipments, and the U.N. body that oversees maritime activity later recommended treatment. But evidence of harm accumulated. A 1969 U.N. paper noted toxic effects in lab animals, and a 1987 study reported severe damage and a possible carcinogenic effect in rats. In 2015, the European Food Safety Authority said an impurity in ethoxyquin, p-phenetidine, could cause mutations in genetic material.
In 2017, the European Commission suspended authorization of ethoxyquin in animal feed, and it is now banned in the U.K. and European Economic Area countries. It remains allowed within limits in Australia, Japan, South Korea, and the U.S. There is no scientific consensus on its safety in farmed seafood, and critics point to risks to aquatic life. In the U.S., lawsuits have challenged 'sustainable' seafood claims for salmon and tilapia sold by Aldi and Gorton's; both cases were settled out of court. In Canada, regulators require labels on feed containing ethoxyquin but do not test whether it ends up in seafood, and a 2024 EU audit found Canada completed only about 40 percent of its planned seafood inspections.