Fact Sheet – Mercury

Estimated Population At Risk At Identified Sites: 8.6 Million People*

Estimated Global Impact: 15 to 19 Million People*


What Is Mercury?

Mercury is a naturally occurring heavy metal and a powerful neurotoxin. Mercury comes in three forms – metallic, inorganic, and organic – each with its own degree of toxicity and particular exposure pathways. Metallic mercury is the pure elemental form of the metal, and is extracted from cinnabar ore. After being heated to above 1,000 degrees Fahrenheit, mercury is refined into its liquid form, which people typically find in thermometers.


What Is Mercury Used For?

In addition to thermometers, mercury can be used in electrical switches and dental fillings, and in the production of caustic soda and chlorine gas. Mercury is also used to separate gold from ore, and is often found at mining sites.


How Is Mercury Released Into The Environment?

Although mercury can be released through natural cycles, anthropogenic releases of mercury account for up to two-thirds of the total mercury in the environment. Common sources of mercury include mining, chemical manufacturing, solid waste disposal, and metals smelting. Many of these activities involve the heating of mercury, which releases the metal into the air in the form of a vapor. Once in the air, mercury is transported in dust by wind. Mercury can then settle into soil or surface waters through precipitation, and often moves far from its source sites.


How Does Mercury Reach Humans?

Mercury is a frequent transboundary pollutant that can migrate through air, water, and organisms to locations far from its original source. People working in or near the industries listed above are most commonly exposed to mercury through the inhalation of vapors produced through the heating of mercury. Others are exposed to mercury through food, water, and soil. If mercury enters a water ecosystem, elemental mercury can be transformed into methylmercury by bacteria. Methylmercury can then bioaccumulate in organisms and eventually end up in species near the top of the food chain. Mercury is well known to accumulate in fish species such as tuna, but can also be found in birds, reptiles, and mammals.


What Health Risks Can Mercury Cause?

The health effects of mercury depend on the amount of exposure, the form of the metal, and the route of exposure. Inhalation of mercury can cause permanent damage to the brain, kidneys, the central nervous system, and the development of a fetus. Exposure to methylmercury can cause arthritis, miscarriages, psychotic reactions, respiratory failure, neurological damage, and at high doses, death.


*Population estimates are preliminary and based on an ongoing global assessment of polluted sites.

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