Large amounts of mercury become airborne when coal, oil, wood, or natural gas are burned as fuel or when mercury-containing garbage is incinerated. Once on the air, mercury can fall to the ground with rain and snow, landing on soil or in bodies of water, causing contamination.

Lakes and rivers are also contaminated when there is a direct discharge of mercury-laden industrial and municipal waste into these water bodies. Once present, mercury accumulates in the tissue of fish and other organisms and may ultimately reach the dinner table.

Although mercury is a very useful element with many unique properties and applications, it poses a very real health risk. We can minimize this risk by reducing our use of mercury-containing products and properly disposing of mercury-containing waste.

Mercury in the Environment

Mercury has become an environmental pollutant because agricultural, industrial, commercial and household products and wastes containing mercury are not properly managed, allowing the mercury to escape into the atmosphere and waterways.

Mercury has long been known to be toxic; the phrase "mad as a hatter" refers to the 19th-century occupational disease that resulted from prolonged contact with the mercury used in the manufacture of felt hats. Some workers today, especially laboratory technicians, nurses, and machine operators, continue to be exposed to mercury on the job. Elemental mercury (the silver liquid familiar from thermometers) is the most common occupational source of exposure.

Exposure typically comes from inhaling mercury vapors. For most us, fluorescent lamps present the single greatest risk of mercury exposure in the work place. A recent study of exposure to broken "low mercury" lamps by the New Jersey Department of Environmental Protection entitled "Release of Mercury from Broken Fluorescent Bulbs" demonstrated that "elevated airborne levels of mercury could exist in the vicinity of recently broken lamps, and "could exceed occupational exposure limits."

Elemental mercury and mercury salts, although fairly inert when deposited on the bottom of waterways, are converted into organic mercury, typically methylmercury, by microorganisms. Organic mercury compounds, especially methylmercury, are more toxic than other forms because they easily cross cell membranes. Methylmercury then enters the food chain where it is biomagnified up to 100,000 times in predacious fish. Eagles, osprey, loons,turtles, mink, otters, and other fish eating creatures are at risk from eating mercury-contaminated fish. Mercury in their diets can cause early death, weight loss, and problems with their ability to reproduce. Unfortunately, wildlife cannot read fish advisories or change their eating habits in order to avoid mercury contamination.

The most common human exposure to methylmercury is through consumption of contaminated fish or animals that eat fish. Minamata disease was named after the occurrence, in the 1950s and 1960s in Minamata, Japan, of many cases of severe mercury poisoning. It was found that a chemicals factory was discharging mercury-containing wastes into the local waters, contaminating fish that residents caught for food.