Health Effects of Exposures to Mercury

Mercury is a neurotoxinHelpneurotoxinA substance that is known or suspected to be poisonous to nerve tissue..  How someone's health may be affected by an exposure to mercury depends on a number of factors:

  • the form of mercury (for example, methylmercury or elemental (metallic) mercury)
  • the amount of mercury in the exposure;
  • the age of the person exposed (the fetus is the most vulnerable)
  • how long the exposure lasts
  • how the person is exposed -- breathing, eating, skin contact, etc.
  • the health of the person exposed.

The effects of mercury exposure can be very severe, subtle, or may not occur at all, depending on the factors above. Anyone with concerns about mercury exposure can consult:

  • Their physician, and/or
  • Their poison control center at 1-800-222-1222.

On this page, you can learn more about health effects associated with the most common exposures to:

Note on Mercury and Cancer
No human data currently ties mercury exposure to cancer, but the data available are limited. In very high doses, some forms of mercury have caused increases in several types of tumors in rats and mice. When EPA published its Cancer Guidelines in 2005, the Agency concluded that environmental exposures to inorganic mercury and methylmercury are not likely to cause cancer in humans. Technical information about mercury and cancer is available in Volume V of the 1997 Mercury Study Report to Congress and in the IRIS Chemical Assessment Summaries for elemental mercury (PDF) (28 pp, 177 K, About PDF; discussion starts on page 15) and methylmercury (PDF) (44 pp, 258 K, About PDF; discussion starts on page 20)

Methylmercury Effects

Effects on People of All Ages

Exposure to methylmercury most commonly occurs when people eat kinds of fish and shellfish that have high levels of methylmercury in their tissues.  Almost all people have at least small amounts of methylmercury in their bodies, reflecting the widespread presence of methylmercury in the environment.  U.S. Centers for Disease Control and Prevention (CDC) data show that most people have blood mercury levels below levels associated with possible health effects. Methylmercury, however, is a powerful neurotoxin, and people exposed to high levels may experience adverse health effects.  If you are concerned about your exposure to methylmercury, you should consult your physician. 

Possible symptoms of methylmercury poisoning may include:

  • loss of peripheral vision
  • "pins and needles" feelings, usually in the hands, feet, and around the mouth
  • lack of coordination of movements
  • impairment of speech, hearing, walking
  • muscle weakness

Effects on Infants and Children

Infants in the womb can be exposed to methylmercury when their mothers eat fish and shellfish that contain methylmercury. This exposure can adversely affect unborn infants' growing brains and nervous systems.  These systems may be more vulnerable to methylmercury than the brains and nervous systems of adults are.

Children exposed to methylmercury while they are in the womb can have impacts to their:

  • cognitive thinking,
  • memory,
  • attention,
  • language,
  • fine motor skills, and
  • visual spatial skills.

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Elemental (Metallic) Mercury Effects

Exposures to metallic mercury most often occur when metallic mercury is spilled, or when products that contain metallic mercury break, so that mercury is exposed to the air. If you are concerned about your exposure to metallic mercury, you should consult your physician.

Metallic mercury mainly causes health effects when inhaled as a vapor where it can be absorbed through the lungs.  Symptoms of prolonged and/or acute exposures include:

  • tremors
  • emotional changes (such as mood swings, irritability, nervousness, excessive shyness)
  • insomnia
  • neuromuscular changes (such as weakness, muscle atrophy, twitching)
  • headaches
  • disturbances in sensations
  • changes in nerve responses
  • poor performance on tests of mental function

Higher exposures may also cause kidney effects, respiratory failure and death.

Note that metallic mercury vapor is not the same as methylmercury.

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Effects of Other Mercury Compounds

High exposure to inorganic mercury may result in damage to the gastrointestinal tract, the nervous system, and the kidneys.  Both inorganic and organic mercury are absorbed through the gastrointestinal tract and affect other systems through this route. 

Symptoms of high exposures to inorganic mercury include:

  • skin rashes and dermatitis
  • mood swings
  • memory loss
  • mental disturbances
  • muscle weakness

Some people who drink water containing inorganic mercury well in excess of the maximum contaminant level (MCL)Helpmaximum contaminant levelThe highest level of a contaminant that EPA allows in drinking water. MCLs ensure that drinking water does not pose either a short-term or long-term health risk. EPA sets MCLs at levels that are economically and technologically feasible. Some states set MCLs which are more strict than EPA's. for many years could experience kidney damage.  People concerned about their exposure to inorganic mercury should consult their physician.

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