Mercury

Mercury is a highly toxic metal. Methylmercury and elemental mercury are the two forms of mercury of greatest importance for children's environmental health. Methylmercury is especially toxic to the developing human brain. Methylmercury is formed when particles of metallic mercury emitted to the atmosphere by coal-fired power plants and other industries precipitate into rivers, lakes, and oceans. It can accumulate in fish and shellfish to reach very high levels in predatory species at the top of the aquatic food chain. Consumption of contaminated seafood is the principal route of human exposure. The developing brain is particularly vulnerable to methylmercury. If exposure to methylmercury occurs during prenatal development, the mother may be completely unscathed, while the child can suffer permanent brain injury. The consequences can include mental retardation with blindness, deafness, microcephaly, and spastic paresis in the most severe cases, but much more commonly consists of subtle cognitive deficits with loss of IQ. Elemental mercury vapor also causes toxicity to brain function. Tremor is a common symptom. Diagnosis of methylmercury toxicity requires analysis of mercury levels in hair or whole-blood. Diagnosis of elemental mercury toxicity requires analysis of mercury levels in urine. Analyses must be performed in properly accredited laboratories.