The European Food Safety Authority (EFSA) has established Tolerable Weekly Intakes (TWIs) to protect consumers from the possible presence of the main forms of mercury found in food. Although the average exposure to the main types of mercury does not reach the maximum levels, some consumer groups might be especially concerned and therefore new scientific information regarding its toxicity needed to be established.

The two main types of mercury found in food are the methylmercury and the inorganic mercury. Both can be found in fish and seafood, but while inorganic mercury is less harmful methylmercury is particularly toxic to the developing nervous system including the brain. Given the potential harm for health and the presence in certain types of food such as ready-made meals, the EFSA’s Scientific Panel on Contaminants in the Food Chain (CONTAM Panel) considered that new scientific information regarding the toxicity of these forms of mercury needed to be established.

The EFSA Panel has established a Tolerable Daily or Weekly Intake (TWI) for inorganic mercury of 4 µg/kg body weight (bw) which is in line with Joint FAO/WHO Expert Committee on Food Additives (JECFA). For methylmercury, new studies indicate that beneficial effects related to long chain omega 3 fatty acids present in fish may have previously led to an underestimation of the potential adverse effects of methylmercury in fish. The Panel has therefore proposed a TWI for methylmercury of 1.3 µg/kg bw, which is lower than JECFA’s 1.6 µg/kg bw.

More precise data on food consumption and on mercury levels in food have allowed the Panel to more accurately assess human exposure to methylmercury through the diet. Fish meat, particularly tuna, swordfish, cod, whiting and pike were identified as the most important contributors of methylmercury exposure in Europe for all age groups, with the addition of hake for children. Exposure in women of child-bearing age was especially considered and found not to be different from adults in general. Exposure through food in high and frequent fish consumers was in general some two-fold higher than for the total population.

This opinion focuses only on the risks related to inorganic mercury and methylmercury exposure through the diet and does not assess the nutritional benefits linked to certain foods (e.g. fish and other seafood). However, the CONTAM Panel added that if measures to reduce methylmercury exposure are considered by risk managers, the potential beneficial effects of fish consumption should also be taken into account.