IV.

Mercury Poisoning

Mercury is acutely hazardous as a vapor and in the form of its water-soluble salts, which corrode membranes of the body. Mercury vapor is a more toxic form than liquid mercury because the fumes easily enter and poison the body through inhalation. The fine gray mercury powder, which is easily produced when liquid mercury is agitated with substances such as grease and chalk, is potentially more dangerous than the liquid metal because it is less readily recognized.

Short-term, limited contact with mercury can cause acute symptoms such as bleeding gums, vomiting, and stomach pain. Mercury poisoning is potentially fatal and can cause irreversible brain, liver, and kidney damage. Because it is difficult for the body to eliminate, mercury acts as a cumulative poison; it can eventually accumulate in the body to dangerous levels. Chronic mercury poisoning occurs when small amounts of the metal or its fat-soluble salts, particularly methylmercury, are repeatedly ingested, either orally or by absorption through the skin, over a long period of time. Ingestion can occur through contamination of the food chain. Because organic mercury compounds such as dimethylmercury were once widely used, significant quantities of mercury have been found in whales and some species of fish. Concern regarding uncontrolled industrial discharge of mercury into the environment, particularly from coal-fired power plants, has led to stricter environmental regulations in many countries. See Environmental and Occupational Diseases.

Concern over the potential health hazards of mercury levels in fish led the United States Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) to issue consumption guidelines in March 2004. The two agencies said pregnant women, children, nursing mothers, and women who may become pregnant should not eat shark, swordfish, king mackerel, or tilefish. The agencies also recommended that this group reduce its consumption of tuna, especially albacore tuna, which is often sold as white tuna. The recommended levels were 6 oz (170 g) of albacore tuna per week and 12 oz (340 g) of light tuna per week. The European Union’s food safety authority also recommended that pregnant women limit their consumption of fish, particularly swordfish and tuna. Scientific studies have shown that unsafe levels of mercury can cause neurological damage, particularly in young children and fetuses. Some consumer and environmental groups recommended even lower consumption of tuna.