Mercury

Uses of Mercury

Consumer items that contain mercury include fluorescent lamps and thermometers. Mercury is also used in dental amalgam and in switches, thermostats, relays, laboratory solutions, and some specialized batteries. Mercury was used in latex paint in the U.S. until 1991, and as a fungicide on grains until that use was also banned. It is used in refining and some industrial processes, especially chlorine production.

Health Effects

Mercury exists in three forms: elemental mercury, inorganic mercury compounds (primarily mercuric chloride), and organic mercury (primarily methyl mercury). All forms of mercury are quite toxic, and each form has different health effects. Exposure to elemental or methyl mercury can result in central nervous system effects. Exposure to inorganic mercury can result in kidney damage. Methyl mercury is the form that is of concern for bioaccumulation. Exposure to methyl mercury, via eating fish, can cause developmental effects. Children born to women who have high levels of methyl mercury have exhibited mental retardation, blindness, and cerebral palsy.

The most well documented cases of severe methylmercury poisoning are from Minamata Bay, Japan in 1956 (industrial release) and in Iraq in 1971 (wheat treated with a fungicide). In each case, hundreds of people died, and thousands were affected, many with permanent damage. Most cases of harmful methylmercury effects occur due to much lower prenatal exposure, and result in developmental effects to children. An analysis of dietary surveys led the U.S. EPA to conclude that between 1 and 3 percent of women of child-bearing age eat enough fish to be at risk from methylmercury exposure

In the Environment

Mercury both bioaccumulates and biomagnifies (increases in concentration in animal tissue as you go up the food chain) in aquatic ecosystems. It has been known since the 1950s that human releases of mercury can cause fish and other wildlife to build up levels of concern. Mercury is the most frequent contaminant necessitating fish advisories, with advisories in 39 states. Mercury contamination has been documented in the endangered Florida panther and the wood stork, as well as other species that eat fish or eat predators that eat fish.

Mercury goes through complex, poorly understood cycles in the environment, in which the mercury is often converted from one form into another and transferred from air to water or vice versa. Aside from some known point sources, the route of most mercury into aquatic ecosystems is deposition from the atmosphere, mostly associated with rainfall. Most of the mercury in the atmosphere is in the form of elemental mercury, which can remain in the air for up to a year, and therefore be transported thousands of miles from where it was originally released. Certain bacteria that process sulfate in the environment take up mercury in its inorganic form and convert it to methylmercury.

Sources

There are many sources of mercury to the environment, both natural and human (anthropogenic). Natural sources include volcanoes, natural mercury deposits, and volatilization from the ocean. The primary human-related sources include coal combustion, chlorine alkali processing, waste incineration, and metal processing. Best estimates to date suggest that human activities have doubled or tripled the amount of mercury in the atmosphere, with the atmospheric burden increasing by about 1.5 percent per year. Water and land releases are thought to be much smaller than air releases.

The most prominent kinds of emitters of mercury to the air include coal burning electric utilities (33 %), municipal waste combustors (19 %), commercial and industrial boilers (18%), medical waste incinerators (10%), chlor-alkali plants (4.5%), hazardous waste combustors (4.4%), and Portland cement manufacturers (3.1%). Of the total air releases, 87 percent are from combustion sources, with a third of the total from coal-fired utilities. Mercury is the air pollutant of greatest concern from these utilities. Industrial use of mercury has declined by 75 % from 1988 to 1996, mostly because of its elimination as a paint additive and in most batteries.

Numeric estimates of mercury use, waste generation, and release are uncertain, but numbers for 1995 will be provided since data from multiple sources exists for that year.

• U.S. production of mercury is as a byproduct of gold mining and from secondary sources (recycling), with 588 tons produced in 1995. World production was 3,100 tons. These quantities include mercury produced for sale, not mercury released through processes such as coal burning.

• U.S. consumption (use) of mercury in 1995 was 480 tons, with 35% used to manufacture chlorine and caustic soda, 19% for wiring devices and switches, and 7% for dental supplies.

• The best estimate of 1995 anthropogenic air emissions of mercury for the U.S. is 158 tons. Water and land emissions were probably much less, with Ohio, for example, estimating 96 percent air emissions and 4 percent water releases.

• Environmental releases from manufacturers reported in the 1995 TRI database were about 8 tons to air and less than a ton to water, land, and underground combined. TRI transfers of mercury in waste were about 142 tons.

• The RCRA Biennial Reporting System database reported about 13.5 million tons of hazardous waste generated in 1995 containing mercury. A large but unknown percentage of this amount was inert substances such as water.

References

* Environmental Protection Agency. Mercury Study: Report to Congress. Office of Air Planning Quality and Standards and Office of Research and Development. EPA-452/R-97-003. December 1997.

* Environmental Protection Agency. Study of Hazardous Air Pollutant Emissions from Electric Utility Steam Generating Units -- Final Report to Congress. Office of Air Planning Quality and Standards. EPA-453/R-98-004a. February 1998.

* U.S. Department of the Interior. Mercury Contamination of Aquatic Ecosystems Fact Sheet. U.S. Geological Survey. USGS FS-216-95. April 1997.

* Environmental Protection Agency. Health Effects Notebook for Hazardous Air Pollutant -- Mercury and Compounds Factsheet. Office of Air Quality Planning and Standards. May 1998.

* Environmental Protection Agency. Mercury in the Environment -- Pollution Prevention Factsheet. Great Lakes National Program Office. March 1997.

* Environmental Protection Agency. Great Lakes Binational Toxics Strategy Implementation Meeting, Mercury Meeting Minutes. Great Lakes National Program Office. March 1998.

* U.S. Department of the Interior. Minerals Yearbook Volume 1. U.S. Geological Survey. 1994-1997.

* Environmental Protection Agency. Toxic Release Inventory Database (1996 "frozen" version).

* Environmental Protection Agency. Biennial Reporting System Database (1995 final version).

Detailed Sources of Mercury Emissions

(The following table is for sources of U.S. air emissions, as reported in Table ES-3 of Volume 2 of the U.S. EPA Mercury Study. Water and land releases are poorly characterized, although Canada reported unexpectedly large water releases from municipal water pollution control plants. Estimates are of 1994-1995 national emission rates.)