Mercury Levels in Tuna Haven’t Budged in the Past Five Decades

The popular canned fish and sushi staple has the same level of mercury despite efforts to reduce pollution.

It’s not easy to drain toxins from our food supply. An analysis of nearly 3,000 tuna samples caught in the Pacific, Atlantic and Indian Oceans between 1971 and 2022 revealed stable mercury concentrations in tuna during those five decades. The research team from The National Centre for Scientific Research in France specifically looked at the tuna species of skipjack, bigeye and yellowfin, which account for 94% of global tuna catches. Environmental policies have helped reduce mercury pollution from human activities like burning coal and mining, but in the paper published in Environmental Science & Toxicology Letters the study authors believe the unchanging mercury levels in tuna might be caused by “legacy” mercury; that which was emitted decades earlier, rising up from deeper regions of ocean water, mixing in with the shallower depths where tropical tuna swim and feed. Another couple of decades might need to pass before reduced levels finally manifest in this fish species. Methylmercury is a particularly toxic chemical that affects the nervous and cardiovascular system and is the primary form of mercury in tuna contamination. Children and pregnant women are strongly encouraged to reduce exposure, but we can also lower our intake by consuming a wider variety of fish including those tested to be lower in the contaminant, including salmon and sardines.