A recent article submitted to the Western Pacific Regional Fishery Management Council provided scientific backing to help dispel fears surrounding mercury levels in tuna.
In a guest article submitted to the management council, John Kaneko, a seafood safety specialist based in Honolulu, Hawaii, highlighted where the origins of mercury fears surrounding tuna first emerged.
Fears of mercury in seafood, according to Kaneko, began in Minamata, Japan, in the 1950s, when high mercury levels in contaminated seafood caused birth defects and other health issues. This was due to severe industrial pollution from mercury-tainted wastewater – not naturally occurring mercury concentrations.
Kaneko explained that tuna became a scapegoat in efforts to distance human industrial activities, such as coal and gold mining, coal burning, and waste processing, from mercury issues.
“Repeat a story enough times, it becomes true. The intent is to engage the public in support of controlling mercury pollution, especially from coal fired power plants,” Kaneko said in the article.
In the present day, Kaneko acknowledged that while people are primarily exposed to mercury through seafood consumption and that mercury is a neurotoxin, it is not accurate to say that mercury concentrations typically found in tuna are harmful, especially to fetuses and young children.
He also outlined that there has never been an outbreak of mercury poisoning from tuna consumption and that mercury levels have not shifted significantly over time.
To the latter point, Kaneko pointed to a study published in 2021 in ScienceDirect that explained while tuna shows interannual variability in mercury content, there has been no overall trend in one direction or the other over the past 18 years. Kaneko himself has collected samples of Hawaii yellowfin tuna, compared them to a sample set from 1971, and found no change in mercury levels.
“These more recent studies have evolved from those that focused on mercury alone and treated fish, including tuna, simplistically as a mercury delivery system. But, tuna (and other seafood) contains beneficial nutrients, not only mercury,” Kaneko said.
Wild-caught fish from the ocean provides protein; omega-3 fatty acids; vitamins B12, B6, and D; iodine; selenium; and other essential nutrients that support healthy body and brain development, according to Kaneko.
To that end, in 2024, the National Academy of Science, Engineering, and Medicine (NASEM) completed a systematic consensus study, finding that higher fish consumption in children is associated with a lower risk of adverse health outcomes or no association at all. The evidence of increased risk was insufficient to draw a conclusion.
Further, Kaneko pointed to another 2024 study in Neurotoxicology that found seafood benefits the health of children when consumed by the mother during pregnancy, even with some mercury levels present in commercially available fish. It showed that children born to mothers who ate seafood during pregnancy had improved neurodevelopment, with two to five higher IQ points.
Kaneko even argues that eating tuna can help protect against mercury toxicity in some instances, so long as the tuna being eaten has high selenium content, a nutrient commonly found in fish. Kaneko said that selenium can protect against mercury toxicity by binding with mercury and rendering it inert, thus preventing harm.
As for how the tuna-fishing industry can help avoid high mercury levels in their products, Kaneko suggests more transparency in where fishing is occurring, which would help lessen instances of fish being sourced in areas of high industrial mercury waste. He also calls for further research into the amount of selenium and mercury in popularly consumed fish, and from that, the industry can push the public to consume fish high in selenium and low in mercury
