Exposure of Arctic populations to methylmercury from consumption of marine food: an updated risk-benefit assessment

Abstract

Recent and powerful epidemiological studies have been used as a basis for revising international and domestic guidelines for human exposure to mercury. Long-range transport of mercury into the Arctic makes some Arctic peoples consuming traditional marine foods, especially newborns, children and pregnant women, very vulnerable to harmful exposures. The WHO, the USEPA and Health Canada have all recently revised their mercury intake guidelines as a result of neurological effects reported in children exposed in utero and adults. Guidance values are equivalent to 0.23 microg/kg-bw/d, 0.1 microg/kg-bw/d and 0.2 microg/kg-bw/d respectively. Differences between the numbers represent slight differences in the uncertainty factors applied, rather than in toxicological interpretation. More recent findings suggest that mercury may also be a factor in ischemic heart disease, which could lower guidance values in the future. Considering the benefits of marine fatty acids (n-3 fatty acids) and guidance that populations consume 300-400g fish/week, consumers face a reality that most open ocean and relatively 'unpolluted' fish species contain levels of mercury that would lead to exposures at current guidance levels. Clearly, there is no more room for further mercury pollution and there is an urgent need for international action to reduce mercury emissions. Concomitantly, while there may be a need for public health authorities to provide consumption advisories to some highly exposed populations, such as in the Arctic, there remains a need to better understand the interactions and benefits associated with marine foods that may reduce health risks associated with low-level mercury exposure.