In the 1960s and 1970s, the horrors of mercury poisoning in Japan and elsewhere shocked the world into curbing releases of the toxic metal. Since then, mercury pollution from human activities, like burning coal and mining, has declined in many parts of the world.
But when a team of French researchers analyzed thousands of tuna samples from 1971 to 2022, they found that mercury levels in the fish remained virtually unchanged.
That’s most likely because “legacy” mercury that has accumulated deep in the ocean is circulating into shallower depths where tuna swim and feed, the researchers posit in a study published this month in the journal Environmental Science & Technology Letters.
Using modeling, they predicted that, even with the most stringent mercury regulations, it would take an additional 10 to 25 years for mercury concentrations to start falling in the ocean. Drops in mercury in tuna would follow only decades after that.
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