Metallic Mercury and Mercury Compounds

Mercury Toxicity has the latest information on the toxicity of mercury.

Historic Uses for Mercury in Washington contains an account of past uses of mercury including mining and use in gauges, switches and gadgets for which substitutes are now available.

Three Types of Mercury

Elemental (metallic) mercury and mercury vapors

At room temperature, metallic mercury is a dense liquid that vaporizes easily.  Metallic mercury is not easily absorbed into unbroken skin.  However, it vaporizes, even at room temperature.  The higher the temperature, the more vapors are released. Mercury vapors are colorless and odorless, though they can be seen with the aid of an ultraviolet light.

In this form, the mercury collects in brain tissue and can cause damage. Some people who have breathed mercury vapors report a metallic taste in their mouths.

Inorganic mercury

Inorganic mercury compounds occur when mercury combines with non-carbon elements such as chlorine, sulfur, or oxygen.  Poisoning by these "salts of mercury" affects the gastrointestinal tract and kidneys. 

Organic mercury

Mercury combined with carbon forms organic mercury compounds, sometimes called organomercurials.  These compounds are especially hazardous to people and other carbon-based life.  One form of organic mercury, dimethylmercury, is so toxic that two drops on the outside of a latex glove killed a Dartmouth researcher. 

By far the most common organic mercury compound in the environment is methylmercury.   Microorganisms (bacteria and fungi) and natural processes can change the mercury in the environment, from metallic mercury to methylmercury. Methylmercury can build up in certain edible freshwater and saltwater fish and marine mammals to levels that are many times greater than levels in the surrounding water.  People who eat these fish may be exposed to unsafe levels of this very toxic form of mercury.  Exposure to methylmercury can cause subtle and not-so-subtle neurological deficits, especially in fetuses (when the mother is exposed) and children.

Related information

Fish Advisories at the Washington State Department of Health
Fish Advisories at the United States Environmental Protection Agency
Mercury Vapor Video at Michigan Department of Community Health
Mercury Research Team at the United States Geological Survey
Mercury at Theodore Gray’s
United Nations Mercury Programme from the United Nations Environment Programme