Definition

Mercury toxicity occurs when a person is exposed to mercury. Mercury is a naturally occurring heavy metal. Short- or long-term exposure to mercury can cause serious health problems.

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.

Causes

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. Thimerosol is a preservative in some vaccines. It contains a very small amount of a type of mercury but many studies showed it was not harmful to people.

Risk Factors

Anyone can develop mercury toxicity as a result of mercury exposure. Certain people are more likely to be exposed to mercury. The following factors increase your chances of being exposed to mercury. If you have any of these risk factors, tell your doctor:

• Working in:
  • Dental services
  • Health services
  • The chemical industry
  • Other industries that use mercury
  • Electric meter repair
• Eating over 6 ounces of white albacore tuna per week
• Eating over 12 ounces a week of fish and shellfish that is considered lower in mercury, such as shrimp, canned light tuna, salmon, pollock, and catfish
• Practicing rituals that include mercury

In addition, pregnant women, their unborn fetuses, and young children are especially vulnerable to the harmful effects of mercury exposure.

Symptoms

Mercury can cause harmful effects before symptoms develop. It is important to contact your doctor right away if you think you have been exposed to mercury, regardless of your symptoms. When symptoms do develop, they may include:

• Redness of the extremities, chest, and nose (dusky pink hands and feet)
• Nausea, vomiting, or diarrhea
• Abdominal pain
• Coughing and chest pain
• Peeling of the hands and feet
• Painful extremities
• Tremors
• Changes in vision or hearing
• Insomnia
• Weakness
• Memory problems
• Headache
• Rapid heart beat
• Eye irritation
• Irritability
• Breathing problems
• Painful mouth
• Fever and/or chills
• Difficulty concentrating

Diagnosis

You will be asked about your symptoms and medical history. A physical exam will be done.

Tests may include:

• Blood tests
• Urine tests
• Scalp hair analysis

Treatment

The most important thing is to stop mercury exposure. Talk with your doctor about other treatments for you. Treatment options include:

Prevention

To help reduce the chances of mercury toxicity:

• Avoid using metallic mercury for any purpose.
• If you must use metallic mercury, keep it safely stored in a leak-proof container in a secure space, such as a locking closet.
• Trade in old thermometers or barometers containing mercury for new ones that do not.
• Carefully handle and dispose of items containing mercury, such as thermometers and fluorescent light bulbs.
• Do not vacuum or heat spilled mercury.
• Teach children not to play with silver liquids.
• Properly dispose of old medications that contain mercury.
• Keep mercury-containing medications away from children.
• Learn about wildlife and fish advisories in your area from your local public health or natural resources department.
• Limit fish intake to recommended quantities and avoid fish known to be contaminated by mercury:
  • Do not eat shark, swordfish, king mackerel, or tilefish.
  • Eat up to 12 ounces of fish and shellfish considered lower in mercury per week. These fish include shrimp, canned light tuna, salmon, pollock, and catfish.
  • Eat up to 6 ounces of white albacore tuna per week.
  • If you want to eat local fish, check to make sure the water is not contaminated. In general, limit your intake of local fish to 6 ounces.

If you spill a small amount of metallic mercury:

• Remove children from the area.
• DO NOT use a vacuum cleaner.
• Carefully roll the bead of mercury onto a sheet of paper or suck it up with an eyedropper.
• Place the bead in a bag or airtight container.
• Contact your local health department to find out how to dispose of the mercury and paper or eye dropper.
• Ventilate the room to the outside.
• Use fans to speed ventilation for at least 1 hour.