Mercury is a naturally occurring metal that exists in several forms. The main way that people are exposed to mercury is by eating fish and shellfish that contain high levels of methylmercury. A less common way people are exposed is by breathing metallic (elemental) mercury vapor. Mercury salts can be absorbed through the skin and have been found in some imported skin-lightening creams, soaps, and dietary supplements. People who work in certain industries or laboratories may be exposed at work. Each form of mercury has different sources of exposure and health risks. The best way to prevent mercury-related health effects is to avoid exposure to mercury.

Sources of Mercury Exposure


Eating fish or shellfish contaminated with methylmercury. Methylmercury accumulates in lakes, rivers and oceans, and can build up in the bodies of fish and shellfish. The amount of mercury you are exposed to depends on the amount and types of fish you eat. Usually, greater amounts of mercury are found in larger fish that eat other fish.


Metallic (elemental) mercury+

  • Breathing vapors in air when items containing metallic mercury break or spill: Metallic mercury is used in older thermometers and blood pressure cuffs, fluorescent light bulbs and some electrical switches. All mercury spills should be cleaned up quickly. See Cleaning Up Mercury Spills in the Home (PDF)
  • Release of mercury from dental work: Elemental mercury is used in dental amalgam, also known as “silver filling”. When amalgam fillings are placed in or removed from teeth, they can release a small amount of mercury vapor. See Mercury in Dental Amalgam.
  • Breathing mercury vapors in the workplace: Mercury compounds are used in some industries and laboratories.
  • Engaging in cultural or religious practices that include metallic mercury (also known as azogue or vidajan): There is no safe way to use mercury for cultural or religious purposes.


Mercury salts +

Certain dietary supplements, skin-lightening creams and soaps contain mercury salts: People are exposed to mercury in these products if they swallow or apply them to their skin.


Health Risks of Mercury Exposure

Exposure to mercury can be harmful to health—including damage to the brain, nervous system, lungs and kidneys. Whether or not mercury causes problems depends on the form of mercury, how it enters the body and the amount of time you are exposed.

  • Methylmercury: Developing babies (in utero) and young children are at special risk because their brains are developing. Mercury exposure at these ages can cause learning problems.
  • Metallic (elemental) mercury: Breathing in high levels of mercury vapors can cause coughing, chest pain, trouble breathing and skin rashes. Symptoms of nerve damage, such as memory loss, irritability and shaking, may also occur. Breathing in lower levels over a long period of time can also cause nerve damage. Swallowing small amounts or having minor skin contact with metallic mercury does not pose a serious health concern.
  • Mercury salts: If repeatedly eaten or applied to the skin, some mercury salts can cause memory problems, skin rash and damage to the nervous system and kidneys.

How to Avoid Exposure to Mercury

Ask your doctor if you need to be tested for mercury exposure. Metallic (elemental) mercury and mercury salts can be measured in urine. Exposure to methylmercury is usually measured by a blood test. Call 311 for more information on the health effects, clean-up and disposal of mercury.

Additional Resources

For consumers +

More on Mercury