Sources of elemental mercury (Hg0) include old natural gas regulators, manometers, sphygmomanometers, thermometers, and thermostats. Causes of mercury spills include improper storage, container breakage, children playing with mercury, the breakage of devices containing mercury, and ritualistic use of mercury. Inhalation is the primary exposure route for Hg.
Elemental mercury is a heavy, silvery metal element that is a liquid at room temperature. Liquid mercury evaporates at room temperature and these vapors are invisible, odorless, and, at high levels, they are very toxic. Mercury is unique among the toxic metals since more information is available concerning the toxic effects of mercury on humans than is available from animal studies. The ancients realized mercury was toxic and assigned the task of mining quicksilver to slaves and prisoners. The average life span of miners was 3 years. In 1665 the workday was reduced to 6 hours in the Adriatic quicksilver mines. By the 1800s mercuric nitrate was widely used to soften fur for hats. The resulting exposure of workers lead to a classic syndrome and the phrase "mad as a hatter." In Danbury, Connecticut, a center of hat making, the effects of exposure were characterized as "Danbury Shakes." It was not until 1941 that the use of mercury nitrate in hat making was banned in most states. Mercury is used today in barometers, mercury switches, and fungicide resistant paint, the manufacturing of mirrors, batteries, mercury vapor lamps, and fluorescent light bulbs, in analytical chemistry, and in some pharmaceuticals. Elemental mercury is a silver colored, highly mobile liquid at room temperature. It is toxic by ingestion, inhalation and skin absorption. Inhalation is the primary route of occupational exposure. About 80% of inhaled mercury vapor passes into the blood stream. Soluble mercury salts such as mercuric chloride and mercuric oxides are highly toxic. Service products containing mercury include mercury switches, mercury vapor lamps, mercury containing paint and fluorescent light bulbs. Mercury is regulated as a hazardous waste and each of these products must be disposed of in a accordance with state environmental regulations. In most states both fluorescent light bulbs and mercury vapor lamps can be stored on site (provided certain procedures are followed) and recycled. Broken lamps and bulbs can result in exposure.