Consumption of fish and exposure to methylmercury

Definition and recommendations for consumption

At high doses, methylmercury is toxic for the human central nervous system, particularly duringin utero development and early childhood. The consumption of fish is the main source of food exposure to methylmercury for humans. Regarding the nutritional benefits of fish consumption, the Agency assessed the risks associated with this substance to determine the frequency at which fish could be consumed without any health risks in this respect.

Mercury, methylmercury, what are they?

Mercury is a metal present naturally in trace amountsin the environment. It is mainly released by the earth’s crust into the air and is then dispersed into the soil, water and sediments. It is also diffused into the environmentbecause of waste from human activities: mining, metallurgy, conversion of wood pulp to paper, and the combustion of waste and fossil fuels in particular. Mercury is very volatile in its elemental form, but after chemical transformation it becomes toxic and is easily absorbed by the body (bioaccumulative). It is present at low concentrations in water or sediments in its methylated form, known as methylmercury. It can be highly concentrated in aquatic organisms and its content tends to rise throughout the food chain whenever one species eats another.

Why does the Agency work on this substance?

At high doses, methylmercury is toxic for the human central nervous system, particularly duringin utero development and early childhood. This substance can therefore cause slight behavioural disorders or retarded development in children exposed in utero or after birth, even in when there are no signs of maternal toxicity.

The consumption of fish is the main source of methylmercury food exposure for humans

The contamination level of fish varies according to the species. It tends to be higher in those at the top of the food chain (large predators).

What does the Agency recommend?

Since 2002, the Agency has issued three Opinions assessing health risks associated with the consumption of fish contaminated by methylmercury. Over the course of these Opinions, the Agency has refined and clarified its recommendations in view of the changes in international guideline values and the available data on mercury, on food consumption of different categories of the population, and on the contamination of different types of fish.

For the whole population, ANSES considers that fish consumption does not involve a health risk associated with methylmercury. The population’s intake of methylmercury is below the tolerable daily intake "(1) defined by the World Health Organization.

In terms of nutritional benefits associated with fish consumption (essential fatty acids, proteins, vitamins, minerals and trace elements) the Agency recommends:

  • eating fish twice a week, including fatty fish (salmon, mackerel, sardines, anchovies, smoked trout, herring, etc.);
  • diversifying the species of fish consumed.

For pregnant and breastfeeding women and young children (under 30 months), the Agency recommends taking special precautions:

  • as a precaution, avoid consuming the most contaminated fish: shark, lamprey, swordfish, marlin (similar to swordfish) and siki (a type of shark);
  • limiting the consumption of fish likely to be heavily contaminated (2) to 150 g per week for pregnant and lactating women, and 60 g per week for children under 30 months.

(1) The tolerable daily intake is the amount of a substance that the consumer can eat on a daily basis without any adverse effects on health.

(2) monkfish or angler fish, Atlantic wolf-fish, bonito, eels and elvers, emperor, orange roughy,rosy soldierfish (Hoplostethussp), grenadier, Atlantic halibut, megrim, mullet, pike, plain bonito (Orcynopsisunicolor), poor cod, Portuguese dogfish, rays (skate), redfish, Atlantic sailfish, silver and black scabbardfish, seabream, pandora, black or striped escolar, oilfish, snake mackerel, sturgeon, tuna, etc.