MARINE CONTAMINANTS

Methyl Mercury

Methylmercury is present throughout the world in seafood and freshwater fish. Environmental methylmercury derives almost solely from methylation of inorganic mercury. The major natural source of atmospheric mercury is degassing from the earth's crust. Global anthropogenic releases of mercury to the atmosphere are estimated to be about similar in magnitude to natural emissions, and local releases may cause serious contamination and be more readily bioavailable than more distant ones, e.g., releases from deep-sea volcanic sources. Methylated mercury is absorbed by fish and shellfish from food and sediments, and possibly also as dissolved species directly from water. Thus, the concentration of methylmercury in finfish tends to be proportional to the mercury concentration in water and also accumulates with time. As a result of biomagnification in food chains, the highest concentrations are found in predatory fish with longer life spans, including freshwater trout, pike, bass, and, in marine species, particularly tuna and swordfish, as well as shark, seals and cetaceans. Mercury also accumulates in a variety of molluscs, crustaceans, and echinoderms, including species that contribute to the human diet. Accumulation of methylmercury in such species results in increased exposures in many fishing communities.

Faroes characteristics

• Traditional food includes pilot whale meat (MeHg) and blubber (POPs)
• Individual reliance on traditional foods varies, depends on seasonal availability
• Traditional diet only weakly associated with confounders
• Otherwise homogeneous, western culture
• Methylmercury and lipophilic POPs originate from different food items (whale meat / blubber)
• Highest exposure about 1,000-fold higher than lowest