Mercury levels in tuna have failed to decrease in half a century

[New Sancai Compilation First] Researchers report that mercury levels in tuna have remained unchanged for more than half a century since 1971, despite efforts to reduce the release of toxic metals into the environment.

They analyzed nearly 3,000 tuna samples caught in the Pacific, Atlantic and Indian oceans between 1971 and 2022 and found that mercury concentrations in tuna remained stable over the five years.

The team looked specifically at tropical tuna species such as bonito, bigeye tuna and yellowfin tuna, which account for 94% of the global tuna catch.

Researchers say environmental policies can help reduce mercury pollution from human activities such as coal burning and mining.

The researchers noted that during the same five-year period, global air mercury pollution decreased.

The reason for the unchanged mercury levels in tuna may be that "legacy" mercury rises from deeper areas of the water and mixes with the shallower depths where tropical tuna swim and feed.

The team, led by marine ecologist Anne Lorrain, director of research at IRD Quest in France, speculates that this legacy mercury may have been emitted years or even decades ago, so it would not reflect efforts to remove mercury emissions from the air.

Researchers say methylmercury is a particularly toxic chemical that can affect the nervous system and is the main form of mercury in tuna pollution. Unborn babies and young children are at the highest risk of harm from exposure.

The researchers used a mathematical model to test three increasingly stringent environmental policies that might reduce mercury levels in tuna.

The models predict that even the most stringent measures will take 10 to 25 years to affect ocean mercury levels, and that mercury levels in tuna will decline over several decades.

The researchers believe their findings demonstrate the need for global efforts to more aggressively address mercury emissions and to continuously monitor mercury levels in marine life.

The new research was published February 21 in the journal Environmental Science and Technology Letters.

(Compiled by: Wang Jimin)

(Editor: Jiang Qiming)

(Source of the article: Compiled and published by New Sancai)