Mercury in food – EFSA updates advice on risks for public health
The European Food Safety Authority (EFSA) has established Tolerable Weekly Intakes (TWIs), or ‘safe levels’, intended to protect consumers from adverse health effects posed by the possible presence of the main forms of mercury found in food: methylmercury and inorganic mercury. Methylmercury is the predominant form of mercury in fish and other seafood, and is particularly toxic to the developing nervous system including the brain. Whereas average exposure to methylmercury in food is unlikely to exceed the TWI, the likelihood of reaching such a level increases for high and frequent fish consumers. This group may include pregnant women, resulting in exposure of the fetus at a critical period in brain development. Inorganic mercury is less toxic and can also be found in fish and other seafood as well as ready-made meals. Exposure to inorganic mercury through food is unlikely to exceed the TWI for most people, unless combined with other sources of exposure.
At the request of the European Commission, EFSA’s Scientific Panel on Contaminants in the Food Chain (CONTAM Panel) considered new scientific information regarding the toxicity of these forms of mercury and evaluated provisional TWIs established in 2003 and 2010 by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). In its opinion, the CONTAM Panel has established a TWI for inorganic mercury of 4 µg/kg body weight (bw) which is in line with 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.
- Mercury is a metal that is released into the environment from both natural sources and as a result of human activity. Besides the element mercury, it can occur as inorganic mercury (mercurous (Hg22+) and mercuric (Hg2+) cations); and organic mercury. Methylmercury (MeHg) is by far the most common form of organic mercury in the food chain.
- A Tolerable Daily or Weekly Intake (TDI/TWI) is an estimate of the average quantity of a chemical contaminant that can be ingested daily or weekly over a lifetime without posing a significant risk to health. Exposure to such contaminants whilst not desirable may not be avoidable as some may be found in foods as a result of environmental pollution (e.g. lead, dioxins, etc.).
- Omega 3, or ‘n-3 long-chain polyunsaturated’ fatty acids, play an important role in the growth and development of the brain, the regulation of blood pressure, renal function, blood clotting, and inflammatory and immunological reactions. EFSA’s Panel on Dietetic Products, Nutrition and Allergies (NDA Panel) recently assessed the safety of long-chain omega-3 fatty acids .
- A call for annual collection of chemical contaminant occurrence data in food and feed, including mercury, was issued by EFSA in December 2010. In response EFSA has received 59,820 results from testing of the presence of mercury in food from 20 European countries, covering 2002 to 2011. Because of the lack of specific information on methylmercury and inorganic mercury in data collected, the exposure assessment (except for human milk) was based on the data submitted for total mercury.