An environmental NGO has issued a warning about high mercury levels in tinned tuna sold in the UK and EU countries.

Research conducted by the BLOOM Association and Foodwatch France over 18 months found that all of the 148 tinned tuna samples they analysed from five European countries were contaminated with mercury.

The five countries that were included in the study were the UK, France, Italy, Spain and Germany.

Currently, EU and UK regulations set the mercury limit in tuna at 1 mg/kg and 0.3 mg/kg for other fish like cod. 

Results from the research showed that 57 per cent of the cans tested exceeded the 0.3 mg/kg threshold standard used for other fish with one tin from a Paris Carrefour City store showing a record 3.9 mg/kg level of mercury, The Mirror reports.

In response to their findings, Bloom and Foodwatch are urging European countries to "activate a safeguard clause" to halt the sale and promotion of products surpassing the 0.3mg/kg level.

They claim that allowing the mercury threshold to be higher in tuna allows producers to legally sell contaminated fish.

Karine Jacquemart, CEO of Foodwatch France, stated: "What we end up with on our dinner plates is a colossal risk to public health that's not considered seriously. We won't give up until we have a more protective European standard."

Campaigners have also urged governments to ban "all products" containing tuna from school canteens, nurseries, maternity wards, hospitals, and care homes due to health concerns.

Europeans on average consume more than 2.8 kilos of tuna annually, equating to around 25 cans.

How has mercury got into tuna?

A significant portion of mercury released into the atmosphere, both naturally and through human activities like coal burning, eventually finds its way into the oceans.

Here, it is transformed by microorganisms into a toxic form known as methylmercury.

This substance then climbs the food chain, accumulating in large quantities within apex predators.

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Tuna, along with other predatory or long-lived species such as sharks and swordfish, are particularly susceptible to mercury build-up due to their diet of smaller fish and longer lifespans.

Methylmercury exposure can harm the kidneys and nervous system, cause vision problems, and increase the risk of heart disease.

The World Health Organisation (WHO) has highlighted that pregnant women and children are especially at risk from high levels of methylmercury.