Mercury Levels in Tuna Remain Nearly Unchanged Since 1971, Study Says


Tuna is one of the most popular seafoods worldwide. 

Tuna is one of the most popular seafoods worldwide. But this protein-rich fish can build up high levels of methylmercury from feeding on contaminated prey, like smaller fish or crustaceans. Despite efforts to reduce mercury emissions into the environment, researchers report in ACS’ Environmental Science & Technology Letters that levels in tuna appear to be unchanged since 1971. They warn that more aggressive emission reduction targets are needed to start nudging down tuna mercury levels.

Environmental protection policies have helped reduce mercury pollution from human activities like burning coal and mining worldwide. However, people can still be exposed to methylmercury, and unborn babies and young children are at highest risk of harm. Methylmercury is a particularly toxic chemical that affects the nervous system and is expected to be the primary form of mercury in reference to tuna contamination. So, researchers set out to determine whether lower atmospheric emissions resulted in lower concentrations of mercury in the oceans, specifically the methylmercury found in food sources that sit at the top of the food chain like tuna. Anne Lorrain, Anaïs Médieu and David Point worked with an international team of researchers to investigate trends of mercury in tuna over the past 50 years. They also wanted to simulate the impact of different environmental policies on oceanic and tuna mercury levels in the future.

The researchers compiled previously published data and their own data on total mercury levels from nearly 3,000 tuna muscle samples of fish caught in the Pacific, Atlantic and Indian Oceans from 1971 to 2022. They specifically looked at tropical tuna — skipjack, bigeye and yellowfin. These three species account for 94% of global tuna catches. Because they don’t undergo transoceanic migrations, any contamination found in the animals’ muscles likely reflects the waters they swim in.

Read more at American Chemical Society

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