Metallic Mercury and Mercury Compounds
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 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.
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.
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