Mercury levels in tuna have remained unchanged decades after pollution controls were introduced to limit emissions, BTA reported, citing French scientists.

The toxic element is released during the mining and burning of coal and enters the ocean, where it is deposited in fish. 

Mercury levels in tuna remained constant between 1971 and 2022, the scientists found, except for an increase in the Pacific Northwest in the late 1990s that was linked to rising mercury emissions in Asia, driven by the growing consumption of coal for energy production.

A tuna was sold for more than 250,000 euros at the New Year's auction in Tokyo

Experts say old mercury is hiding deep in the ocean and rising in the waters where tuna fish swim. 

Mercury that enters marine ecosystems turns into its most dangerous form - methylmercury.

It accumulates in tuna when it ingests infected prey.

Humans are then exposed to the element when they eat the fish, which is one of the most consumed in the world.

Mercury poses a particular threat to unborn babies and young children, but is also linked to cardiovascular disease in adults.

Governments around the world are trying to reduce activities that cause this chemical to be released into the atmosphere.

Major sources include coal and gold mining, coal combustion, industry and waste processing.

Even the cremation of human bodies with amalgam fillings contributes to the release of its total amount into the air.

To test whether these actions had an impact on mercury levels in tuna, the researchers examined data from nearly 3,000 muscle samples from tuna caught in the Pacific, Atlantic and Indian oceans, which together account for 94% of the world's tuna catch .

Among other studies, mercury levels in some types of tuna have been found to be decreasing. 

"We have a lot more data, more samples and a wider range of fish sizes," said study lead author Anais Medeau of the French National Research Institute for Sustainable Development.

Scientists say the persistent levels may be due to emissions from many decades or centuries ago. 

"Our study shows that huge reductions in mercury emissions would be needed to reduce mercury levels in tuna," said study co-author Ann Loren.

"Even with significant reductions in emissions, our results suggest that we will have to be patient before we see a change in mercury levels in tuna."

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