Mercury toxicity occurs when a person is exposed to mercury. Mercury is a naturally occurring metal. Either short- or long-term exposure to mercury can cause serious health problems. If you think you have been exposed to mercury, contact your doctor immediately.
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 are better able to reach the brain and more harmful than mercury salts.
Metallic mercury is the liquid metal that was once used in most thermometers. Most new thermometers are being manufactured with less toxic indicators. Mercury is also used in other common consumer products, including:
- Fluorescent light bulbs
- Dental fillings
- Medical equipment (eg, blood pressure measurement instruments)
- Mercury switches in thermostats and even sneakers that light up
Mercury gas is released into the atmosphere by certain natural processes (fires, volcanic explosions). It is released in much greater amounts by the burning of fossil fuels, especially coal. Once in the atmosphere, mercury can travel for thousands of miles before finding its way into the ocean or fresh water bodies. Once in or near the water, mercury is transformed by bacteria into the chemical methylmercury. The methylmercury formed in the water and soil by bacteria may build up in the tissues of fish. Larger and older fish tend to have the highest levels of mercury.
Mercury toxicity may occur when a person is exposed to toxic amounts of mercury due to:
- Breathing airborne mercury vapors
- Eating food (usually fish or shellfish) contaminated with methylmercury
- Drinking water contaminated with mercury (a relatively rare cause of poisoning)
- Release of mercury from dental work and medical treatments
- Many dental fillings contain mercury, and under certain conditions these might release mercury vapor that could enter the bloodstream through the lungs. Removing mercury amalgam fillings during pregnancy might prove harmful because of the fetus’ special risk from elevated mercury levels in mother’s blood.
- Practicing religious or folk medicine rituals that include mercury
A risk factor is something that increases your chance of getting a disease or condition. 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:
- Dental services
- Health services
- Chemical industry
- Other industries that use mercury
- Practicing rituals that include mercury
- Eating more than three 6-8 ounce servings per week of common fish (including tuna, halibut, and salmon)
- Eating significant quantities of fish known to have particularly high mercury levels. These include king mackerel, tilefish, shark, and swordfish.
In addition, pregnant women, their unborn fetuses, and young children are especially vulnerable to the harmful effects of mercury exposure.
Widespread Toxicity in Infant
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The nervous system is very sensitive to the effects of mercury. Exposure to mercury can result in:
- Brain damage
- Kidney damage
- Lung damage
- Digestive system problems
Mercury can cause harmful effects before symptoms develop. It is important to contact your physician immediately if you think you have been exposed to mercury, regardless of your symptoms. When symptoms do develop, they may include:
- Changes in vision or hearing
- Memory problems
- Increases in blood pressure or heart rate
- Eye irritation
- Breathing problems
- Painful mouth
- Abdominal pain
- Fever and/or chills
- Acrodynia (symptoms include itching, swelling, and flushing; pink-colored palms and soles of feet; excessive perspiration; rashes; irritability; fretfulness; sleeplessness; joint pain; and weakness)
- Trouble learning in school for children
Damage from mercury passed from a mother to her unborn fetus may include:
- Brain damage
- Mental retardation
- Lack of coordination
- Inability to speak
Your doctor will ask about your symptoms and medical history, and perform a physical exam.
Tests may include the following:
- Blood tests
- Urine tests
- Scalp hair analysis
Talk with your doctor about the best treatment plan for you. Treatment options include:
Chelation therapy involves putting a chemical, or chelating agent , into the bloodstream. The chelating agent combines with mercury to help remove it from the body. Chelating agents may be given by pill or by injection.
For recent ingestion, the doctor may induce vomiting, pump out the stomach (gastric lavage), or give polythiol resins to bind with the mercury.
To help reduce your chances of getting mercury toxicity, take the following steps:
- 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 (eg, 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 (eg, thermometers, fluorescent light bulbs)
- Do not vacuum or heat spilled mercury
- Teach children not to play with silver liquids
- Properly dispose of old medications containing 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 especially contaminated by methylmercury
If you spill a small amount of metallic mercury (eg, a broken thermometer):
- 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 eye dropper.
- 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 one hour.
If you find a larger amount of metallic mercury (eg, a jar of metallic mercury), call your local health department for professional assistance in safe and appropriate disposal. If any amount of mercury greater than that found in a fever thermometer spills, call for help and immediately leave the area of the spill until responsible and prepared authorities arrive to assist in cleanup. If your health department is unavailable, your fire department may be able to provide emergency assistance or connect you with the local “Hazmat” team.
Agency for Toxic Substances and Disease Registry
Office of Hazardous Materials Safety
US Environmental Protection Agency
US Food and Drug Administration
BC Health Guide
Harrison’s Principles of Internal Medicine . 16th ed. McGraw Hill; 2005.
National alert: a warning about continuing patterns of metallic mercury exposure. Agency for Toxic Substances and Disease Registry website. Available at: http://www.atsdr.cdc.gov/alerts/970626.html . Accessed March 12, 2007.
National alert: a warning about continuing patterns of metallic mercury exposure. Agency for Toxic Substances and Disease Registry website. Available at: http://www.atsdr.cdc.gov/alerts/970626.html . Accessed February 15, 2006.
ToxFAQs for mercury. Agency for Toxic Substances and Disease Registry website. Available at: http://www.atsdr.cdc.gov/tfacts46.html . Accessed March 12, 2007.
ToxFAQs for mercury. Agency for Toxic Substances and Disease Registry website. Available at: http://www.atsdr.cdc.gov/tfacts46.html . Accessed February 15, 2006.
What you need to know about mercury in fish and shellfish. Food and Drug Administration website. Available at: http://www.cfsan.fda.gov/~dms/admehg3.html . Accessed March 12, 2007.
What you need to know about mercury in fish and shellfish. Food and Drug Administration website. Available at: http://www.cfsan.fda.gov/~dms/admehg3.html . Accessed February 15, 2006.
Last reviewed March 2008 by Mark A. Best, MD, MPH, MBA
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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