Mercury in the Environment: Natural and Human Factors

Poisoning due to the consumption of mercury in food is a well-documented but poorly understood medical phenomenon. Metallic mercury and inorganic mercury compounds usually attack the liver and kidney, but in ordinary exposures they do not remain in the body long enough to accumulate to serious levels. Methylmercury and other alkyl mercury compounds are more dangerous since they attack the central nervous system and remain in the body for longer periods of time. Symptoms of methylmercury poisoning in man may include loss of vision, hearing, coordination, and intellectual ability. There is still some uncertainty as to what constitutes lethal concentrations of methylmercury in man; there is variability in individual tolerance. Although mercury is a scarce element, it occurs widely in nature and readily forms a variety of compounds; the most commonly occurring is cinnabar, the mercuric sulfide. Consumption of the metal in the USA since 1900 has been about 10/sup 5/ metric tons, with world consumption probably several times as great. Reliable estimates of how much of this has been lost to the environment are hard to come by, but it may be as much as a third.