Much of the mercury in the environment originates from natural geological processes, such as the degassing of the earth’s crust. As with other metals, toxicity may result from elemental mercury, nonorganic mercury salts, and organic mercury compounds. There are differences in the absorption of the various forms of mercury, with higher gastrointestinal absorption for organic mercury. Also, different effects on target organs for each form of mercury are evident, with nonorganic salts concentrating in the kidneys and organic mercury showing a preference for the brain. Elimination, again form dependent, is through urine or feces. Animal studies show that all forms of mercury cross the placental barrier, and it is most likely that since organic mercury crosses the bloodbrain barrier in humans, it also moves across the human placenta. The tragic consequences of mercury toxicity were well illustrated in Minamata Bay, Japan, during the 1950s, where mercury released from a chemical factory entered the bay and contaminated the food supply. Toxicities resulting from exposure to methylmercury include neuropathies, nephropathies, teratogenesis, and mutagenesis.