Mercury is toxic to human health, posing a particular threat to the development of the child in utero and early in life. Mercury exists in various forms: elemental (or metallic); inorganic (e.g. mercuric chloride); and organic (e.g., methyl- and ethylmercury), which all have different toxic effects, including on the nervous, digestive and immune systems, and on lungs, kidneys, skin and eyes.

It has been estimated that among selected subsistence fishing populations, between 1.5/1000 and 17/1000 children showed cognitive impacts caused by the consumption of fish containing mercury. Mercury releases in the environment result mainly from human activity, particularly from coal-fired power stations, residential heating systems, waste incinerators and as a result of mining for mercury, gold and other metals. Once in the environment, elemental mercury is naturally transformed into methylmercury that bioaccumulates in fish and shellfish. 

Human exposure occurs mainly through inhalation of elemental mercury vapors during industrial processes and through consumption of contaminated fish and shellfish. Interventions to prevent environmental releases and human exposure include:

• eliminating mercury production and use in mining and industry;
• promoting use of clean energy sources that do not rely on burning of coal;
• switching to non-mercury thermometers and sphygmomanometers in health care; and
• implementing safe handling, use and disposal of mercury-containing products and waste.