Skip directly to search Skip directly to A to Z list Skip directly to site content Skip directly to page options
CDC Home




Mercury is an element that is found in air, water, and soil. It exists in three forms that have different properties and sources of exposure. The three forms are

A set of high efficiency light bulbs.
  • elemental mercury,
  • inorganic mercury compounds, and
  • organic mercury compounds.

Elemental mercury, also called metallic mercury, is liquid at room temperature. It is used in mining and some industrial processes, and to make fluorescent light bulbs and certain types of dental fillings and electrical switches. It is released into the air when coal and other fossil fuels are burned. In the past, it was used in thermometers and thermostat switches.

Inorganic mercury compounds are formed when mercury combines with other elements, such as sulfur or oxygen, to form compounds. Inorganic mercury compounds can occur naturally in the environment. Some inorganic mercury compounds are used in industrial processes and to make other chemicals. They may be found in skin lightening creams and some folk medicines. In the past, inorganic mercury compounds were used as fungicides and in hat-making.

Organic mercury compounds are formed when mercury combines with carbon. Microorganisms in water and soil can convert elemental and inorganic mercury into the organic mercury compound methylmercury. Methylmercury builds up in the food chain, most importantly in ocean fish that eat other fish, like shark, swordfish, and king mackerel. In the past, methylmercury was used as a fungicide but it is no longer used this way.

The Tracking Network includes biomonitoring data on the concentration of mercury in blood and urine in NHANES participants ages 1 year and older (blood) and ages 6 years and older (urine). Total blood mercury is mainly a measure of methylmercury exposure. Mercury in the urine mainly consists of inorganic mercury. It is also a measure of elemental mercury exposure. Finding a measurable amount of mercury in blood or urine does not mean that the level of mercury causes a health effect.

Exposure and Risk

Cuts of fish lying on a table.

Exposure and health risks depend on the form of mercury. For most people, eating fish and seafood is the main source of methylmercury exposure. There are few sources for most people to be exposed to elemental mercury, other than dental fillings. However, workers in dental offices, health services, mining, or other occupations using elemental mercury may be exposed.

The nervous system, especially in unborn babies, is very sensitive to all forms of mercury. Exposure to high levels of any form of mercury can permanently damage the brain, and kidneys. Many inorganic mercury compounds are also very harmful to the stomach and intestines. At high levels, mercury can affect brain function and cause irritability, shyness, tremors, changes in vision or hearing, and memory problems. Methylmercury can pass from a pregnant woman to her developing baby.

Read about prevention tips to reduce your and your family's exposure to environmental chemicals.

More Information


Top of Page


External Web Site Policy This symbol means you are leaving the Web site. For more information, please see CDC's Exit Notification and Disclaimer policy.

Copyrighted images: Images on this website which are copyrighted were used with permission of the copyright holder and are not in the public domain. CDC has licensed these images for use in the materials provided on this website, and the materials in the form presented on this website may be used without seeking further permission. Any other use of copyrighted images requires permission from the copyright holder. The U.S. Government's Official Web PortalDepartment of Health and Human Services
Centers for Disease Control and Prevention   1600 Clifton Rd. Atlanta, GA 30333, USA
800-CDC-INFO (800-232-4636) TTY: (888) 232-6348 -

Tracking A-Z Index

  1. A
  2. B
  3. C
  4. D
  5. E
  6. F
  7. G
  8. H
  9. I
  10. J
  11. K
  12. L
  13. M
  14. N
  15. O
  16. P
  17. Q
  18. R
  19. S
  20. T
  21. U
  22. V
  23. W
  24. X
  25. Y
  26. Z
  27. #
Tracking A-Z
Glossary A-Z