Mercury/Methylmercury Risk

Abstract Mercury in the environment originates from both natural and anthropogenic sources, especially owing to energy production from fossil fuels. In sediments, inorganic mercury is converted into methylmercury, which is accumulated by fish, shellfish, and marine mammals, and attains its highest concentrations in large predatory species at the top of the food chain, e.g., pike, swordfish, and tuna, as well as shark, seals, and toothed whales. While the toxicity of mercury vapor and mercury salts has been known since ancient times, the risks due to environmental contamination with methylmercury came to the forefront when, about 1960, Minamata disease in Japan was found to be caused by methylmercury due to pollution from a local factory. The methylmercury poisoning in adults is characterized by paresthesias of the extremities, the tongue, and the face, followed by problems in motor coordination. Later, tunnel vision and hearing problems occur. In Minamata, Japan, it was noted that the pregnant mother could appear in good health, while her child would be born with a serious spastic paresis syndrome. Recent evidence from epidemiological studies has shown that subtle cognitive and motor function deficits have already begun to appear at exposure levels prevalent in some fishing communities. No effective antidote is available. Governmental agencies have issued advisories regarding consumption of freshwater fish and seafood, and an international agreement has been reached to limit mercury releases to the environment.