In December 2012, EFSA received a request from the European Commission to carry out a risk benefit analysis as regards the risks and benefits to human health of fish/seafood consumption related to methylmercury. As the EFSA Panel on Contaminants in the Food Chain (CONTAM) had adopted a scientific opinion on the risk for public health related to the presence of mercury and methylmercury in food (EFSA CONTAM Panel, 2012) the month before, the mandate was given to the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) who evaluated the beneficial effects of fish/seafood consumption in relation to health outcomes (effect of fish/seafood consumption during pregnancy on functional outcomes of children’s neurodevelopment and the effects of fish/seafood consumption on cardiovascular diseases in adults) (EFSA NDA Panel, 2014). Having reviewed the conclusions of these two opinions during the 68th Plenary meeting of the Scientific Committee (8–9 July 2014), a decision was made that the Scientific Committee would produce a scientific statement, using the CONTAM and NDA Panels’ work as a starting point, to answer the mandate received from the European Commission. As requested by the European Commission, this statement addresses the benefits of fish/seafood consumption, using n-3 long-chain polyunsaturated fatty acids (LCPUFA) as an example of related beneficial substance, compared to the risks of methylmercury in fish/seafood. Exposure to other possible contaminants (e.g. inorganic mercury and dioxin-like compounds) is not specifically addressed. In this respect, the Scientific Committee refers to the CONTAM opinion on the safety assessment of wild and farmed fish (EFSA CONTAM Panel, 2005). In that opinion the CONTAM Panel identified the following factors as having a major impact on both the nutrient and contaminant levels of fish: species, season, location, diet, life stage and age and, for some contaminants, regional differences.
In its opinion in 2012 on mercury, the CONTAM Panel assessed the data on mercury in food received from 20 European countries, of which about 22000 results were for the food group ‘Fish and other seafood’. The mercury content varied widely among different fish species, and was highest in predatory fish. In order to assess dietary exposure to methylmercury it was assumed that the mercury was 100 % methylmercury in fish meat, fish products, fish offal and unspecified fish and seafood, and 80 % methylmercury in crustaceans, molluscs and amphibians, whereas other foods were assumed to contain inorganic mercury only. There is a wide variation in fish/seafood species consumed in different countries in the EU. Different fish/seafood species vary greatly in their content of n-3 LCPUFA as well as in their content of mercury. The fraction of fish consumers and the amount of fish/seafood consumed also vary substantially between countries.
Based on several epidemiological studies, the NDA Panel (EFSA, 2014) concluded that an intake of from 1–2 up to 3–4 servings per week of fish/seafood during pregnancy was associated with beneficial effects on functional neurodevelopment in children and on adults with coronary heart disease. This means that in the range of 1–4 servings per week, the benefits of fish consumption (as compared to no fish) outweigh the risks, whatever the respective contribution to this net effect of beneficial and harmful fish components may be. It is however noted that there are a number of uncertainties in these epidemiological studies about actual serving sizes and actual contents of the potentially active positive and negative components in fish/seafood consumed. In addition, fish and seafood provide many nutrients, in particular n-3 LCPUFA. Contrasting with the wealth of evidence reporting on the net beneficial balance of fish/seafood consumption, the availability of data allowing estimation/calculation of the net true effect of each fish component (especially n-3 LCPUFA and methylmercury) for each side of the balance is limited.
With regard to methylmercury the CONTAM Panel considered several adverse outcomes and established a tolerable weekly intake (TWI) of 1.3 µg/kg bw/week for methylmercury based on prenatal neurodevelopmental toxicity.
The CONTAM Panel took account of the negative confounding effect of n-3 LCPUFA on the neurotoxicity of methylmercury. Conversely, one would expect methylmercury to negatively confound the positive impact of fish consumption on neurodevelopment and cardiovascular outcomes, but very few data are available on this issue.
Due to inadequate data, a full characterisation of the benefit of fish consumption was not performed. There is a large variation in the average amount of fish intake among the consumers of different age groups across Europe and not all consumers meet the recommended intake of fish of 1–2 servings (equivalent to 150–300 g) per week or the dietary reference value (DRV) for n-3 LCPUFA.
Estimated mean dietary exposures to methylmercury across age groups did not exceed the TWI, with the exception of toddlers and other children in some surveys. The medians of 95th percentile dietary exposures across surveys were close to or above the TWI for all age groups. Fish meat was the dominating contributor to methylmercury dietary exposure for all age classes, followed by fish products. In particular tuna, swordfish, cod, whiting and pike were major contributors to methylmercury dietary exposure in the adult age groups, while the same species, with the addition of hake, were the most important contributors in the child age groups. Dietary exposure in women of child-bearing age was not different from adults in general.
The methodology by which several of the dietary surveys available from 17 EU countries were conducted (i.e. 2-day dietary recalls or 3-day dietary records) overestimate the high ends of the distribution of fish/seafood intake and methylmercury exposure, particularly when transforming the intake data from daily to weekly intake. Therefore, scenarios were created to calculate, based on the composition of the main contributing fish/seafood species and serving sizes reported, the exposure to methylmercury and n-3 LCPUFA intake resulting from consumption of various fish/seafood items typical for different population groups. It was then estimated how many servings of fish/seafood per week a given population group would need to reach the TWI for methylmercury and the DRV for LCPUFA.
The age groups exceeding the TWI for methylmercury at the fewest number of servings per week were toddlers (1–<3 years) and other children (3–<10 years). In a few cases of other children, adolescents, women of childbearing age, adults and elderly, the TWI was reached after less than and around 1 serving per week. In most other cases for toddlers and other children the TWI was reached when the number of servings per week was between 2 and 3. In most cases the TWI for mercury was reached with between 2 and 4 servings per week. For the same groups the intake of n-3 LCPUFA met the DRV at higher than or equal to the number of servings per week that they reached the TWI for methylmercury.
Consuming species with a high content of methylmercury influences the number of servings that can be eaten before the TWI for methylmercury is reached. In the majority of cases the reported serving sizes were below 100g. For toddlers, children and women of childbearing age, the benefits of eating fish should be met by increasing the consumption of species low in mercury. In order to protect the foetus against adverse neurodevelopmental effects of methylmercury, women of childbearing age should not exceed the TWI. As the brain is developing also after birth, toddlers and children exposed to methylmercury above the TWI on a regular basis should also be considered at risk for neurotoxic effects of methylmercury. Besides limiting the intake of fish/seafood species with a high content of mercury in the daily diet to avoid regular exposure above the TWI, it is not possible to make general recommendations on fish consumption across Europe. The Scientific Committee therefore recommends that each country needs to consider its own pattern of fish consumption, especially the species of fish consumed, and carefully assess the risk of exceeding the TWI of methylmercury while obtaining the health benefits resulting from consumption of fish/seafood.