A recent study by a French NGO has found that canned tuna sold in five European countries contains excessive amounts of mercury which pose a risk to public health.

Tuna sold in Germany has a high mercury content

A study by the French NGO Bloom, which analysed 148 cans of tuna sold in Germany, England, Spain, France and Italy, has found that all of the analysed products contained mercury.

Cans of tuna sold in Germany were collected in Berlin, Hamburg and Munich. 17 cans contained 0 to 0,3 milligrams of mercury per kilogramme of tuna (mg / kg), three contained 0,3 to 0,5 mg / kg, eight contained 0,5 to 1 mg / kg and two contained more than 1 mg / kg. Mercury becomes two to three times more concentrated when tuna is cooked and canned.

The mercury limit for tuna sold in the European Union is 2 mg per fresh weight of tuna. The EU also has a stricter, general mercury limit for other fish species, set at 0,3 mg / kg. 57 percent of the 148 cans analysed exceeded this limit.

Why is more mercury permitted in tuna?

Tuna is the best-selling fish in Europe and the average European consumes over 2,8 kg of tuna per year.  According to Bloom, the maximum limit of mercury allowed in tuna sold in the EU is not based on public health concerns but on protecting profits.

“Because the mercury levels measured are generally less than 0,5 mg / kg, the standard is set at 0,5 mg / kg,” the report said, "which is almost impossible to exceed”. “European public authorities have chosen an approach that is completely at odds with their duty to protect public health.”

Bloom claims that if the EU were to apply the lowest maximum mercury concentration permitted for seafood products generally, 0,3 mg / kg, to tuna, “more than half of all canned tuna would be banned from sale”. 

In a response to Euronews Health, the European Commission said that "maximum levels for mercury in food are established on the basis of the data we have on the actual, real-life occurrence of mercury in food. We do this by monitoring products that are placed on the market, taking into account the principle of ‘As low as reasonably achievable’ when producers use good practices."

Why is it dangerous to eat tuna containing mercury?

Volcanic eruptions and forest fires make mercury a natural part of our ecosystem, but fossil fuel burning and waste incineration means two-thirds of mercury is a result of human activities.

When tuna eat other fish, they accumulate the mercury found in their prey, which builds up in tuna flesh over time. Ocean bacteria means that this mercury develops into methylmercury.

Methylmercury is a neurotoxin which, according to the International Agency for Research on Cancer (IARC), is potentially carcinogenic. When we eat high-mercury foods the small doses begin to accumulate. When accumulated, mercury passes into the bloodstream and can affect the neurological development of foetuses and children. Adults may face problems affecting their nervous, cardiovascular and immune systems.

Following their findings, Bloom has now launched an international petition which demands Europe’s 10 largest supermarkets, including Edeka, Rewe, Aldi and Lidl, remove tuna products containing over 0,3 milligrammes of mercury per kilogramme of tuna.

Thumb image credit: artemisphoto / Shutterstock.com