Mercury toxicity occurs when a person is exposed to mercury. Mercury is a naturally occurring metal. Short- or long-term exposure to mercury can cause serious health problems. If you think you have been exposed to mercury, contact your doctor right away.

Mercury has several forms, including:

  • Metallic mercury—a shiny, silver-white, odorless liquid that becomes a colorless, odorless gas when heated
  • Methylmercury—a chemical made up of mercury combined with carbon; mainly produced by microscopic organisms in the water and soil
  • Mercury salts—white powders or crystals formed when mercury combines with elements such as chlorine, sulfur, or oxygen

Metallic mercury and methylmercury easily reach the brain and are more harmful than mercury salts.

Mercury toxicity may occur when you are exposed to toxic amounts of mercury due to:

  • Breathing airborne mercury vapors
  • Eating contaminated food, especially fish or shellfish—Larger and older fish tend to have the highest levels of mercury.
  • Drinking water contaminated with mercury (rare)
  • Practicing religious or folk medicine rituals that include mercury

Metallic mercury can be found in consumer products, such as fluorescent light bulbs, batteries, thermostats, and old thermometers. Mercury, combined with other elements, is also found in some types of dental fillings. Research has not shown that this type of filling is harmful to people. Although thimerosol is no longer used in vaccines in the United States, the mercury-containing compound is still used in some countries. Research has not shown that it is harmful to people.