Mercury in tuna has intrigued scientists for decades – 02/25/2024 – Environment
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A new study reveals that mercury levels in tuna remain the same, decades after measures were introduced to limit its emissions.
This toxic element is released by mining and burning coal – and ends up in the oceans, where it accumulates in fish.
Its levels have fallen dramatically in the atmosphere – but have remained stable in tuna since 1971.
According to experts, the oldest mercury hides in the depths of the ocean and reaches the waters where tuna swim.
Mercury that enters marine ecosystems is converted to methylmercury, the most dangerous form of the chemical.
It accumulates in tuna when it consumes contaminated prey.
And human beings end up exposed to the toxic element when they eat fish, one of the most consumed in the world.
Mercury poses a threat especially to unborn babies and young children, but it has also been linked to cardiovascular disease in adults.
Concerns about exposure to mercury have prompted governments around the world to try to reduce activities that release the chemical into the atmosphere.
Main sources include:
- Coal and gold mining;
- Coal burning;
- Industry;
- Waste processing.
Even the cremation of human bodies with amalgam fillings contributes to the total in the air.
Restrictions on many of these activities have caused atmospheric emissions levels to fall by around 90% since 1990.
And to see if these actions had had an impact on mercury levels in tuna, researchers analyzed data from nearly 3,000 tuna muscle samples from fish caught in the Pacific, Atlantic and Indian oceans, including skipjack/bonito, bigeye and albacore, which together represent 94% of global tuna fisheries.
The new study contrasts with other research showing declining mercury levels in some tuna species.
“We have much more data, more years of sampling and also a wider range of fish sizes,” explains the study’s lead author, Anaïs Médieu, from the French National Research Institute for Sustainable Development.
“This is very important because mercury bioaccumulates during [vida] of the animal. So having a wide range of fish sizes is very important.”
Mercury levels in tuna remained constant between 1971 and 2022, scientists reported, except for an increase in the Pacific Northwest in the late 1990s linked to rising mercury emissions in Asia driven by increased coal consumption for food. energy.
According to researchers, the constant levels could be caused by emissions from many decades or centuries ago.
“There is a huge legacy of mercury that is in the depths of the ocean”, explains Médieu.
“This mixes with the surface of the ocean, where tuna swim when they feed. That’s why we have a continuous supply of this historic mercury that was emitted decades or centuries ago.”
Stabilize slowly
Co-author of the study, Anne Lorrain, also from the French National Research Institute for Sustainable Development, says that efforts must be redoubled – but we must be patient.
“Our study suggests we will need massive reductions in mercury emissions to see a drop in mercury levels in tuna,” she tells BBC News.
“Even with a massive reduction in mercury emissions, our results show that we will have to be patient until we see a change in mercury levels in tuna,” she adds.
“Overall, it is similar to CO2 emissions [dióxido de carbono] – if we drastically stop emitting, the CO2 in the atmosphere will slowly stabilize and, finally, it will start to decrease”, he explains.
The study was published in the academic journal Environmental Science & Technology Letters.
This text was originally published here
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