Hard, brittle, and gray–white in color, manganese is a component of various types of rock and occurs naturally in our air, soil, and water. It is the twelfth most common element and the fifth most common metal (Int J Occup Environ Health. 2003 Apr–Jun; 9(2): 153–63). Manganese rarely occurs in its pure form, and instead combines with oxygen, sulfur, chlorine, carbon or other substances to form compounds.
A normal component of food, manganese in trace amounts is essential for good health. However, exposure to excess amounts of manganese may cause manganese poisoning or manganism and increase the risk of developing Parkinson’s disease. Welders, manganese miners, and pesticide workers are particularly at risk for developing these diseases because they come into contact with manganese on the job (see Groups Exposed to Manganese).
About 800 million tons of manganese ore were extracted in 2003 worldwide, with about 85% to 90% used in the production of steel (U.S. Geological Survey, Manganese Statistics; Manganese Data). The metal is used in pesticides, plant fertilizers, animal feed, fireworks, matches, alkaline batteries, and colorants for bricks. Manganese may also be introduced into the environment through emissions from steel plants, mining operations, and the burning of fuel containing MMT or methylcyclopentadienyl manganese tricarbonyl, a fuel additive and octane enhancer in some gasoline mixtures. Gasoline containing MMT is sold in 25 countries, including Canada and some parts of the United States.
The U.S. Environmental Protection Agency (EPA) has identified 603 hazardous waste sites on the National Priorities List that contain large amounts of manganese. They will require long–term clean–up efforts (Public Health Statement for Manganese, Agency for Toxic Substances and Disease Registry, September 2000). The agency is studying the health risks posed by manganese–containing MMT in order to reconsider the current limits for the fuel additive in gasoline (Comments on Gasoline Additive MMT, EPA).