Mercury Poisoning


Mercury poisoning is exposure to harmful amounts of the toxic element, usually by breathing mercury vapors or ingesting compounds containing mercury. Mercury poisoning can permanently damage the nervous system and immune system, as well as the brain, lungs, kidneys, heart, and liver. High-level exposure can be fatal. Developing fetuses are particularly sensitive to mercury poisoning.


Mercury levels in fish

Least mercury

Cod (Alaskan)


Croaker (White Pacific)


Halibut (Atlantic)


Halibut (Pacific)



Crab (Domestic)




Croaker (Atlantic)

Mahi Mahi



Haddock (Atlantic)

Perch (Freshwater)





Mackerel (N. Atlantic, Chub)



Tuna (Canned chunk light)


Tuna (Skipjack)

Perch (Ocean)

Weakfish (Sea Trout)



High mercury

Salmon (Canned)


Salmon (Fresh)



Mackerel (Spanish, Gulf)


Sea bass (Chilean)

Shad (American)

Tuna (Canned Albacore)


Tuna (Yellowfin)

Sole (Pacific)

Highest mercury

Squid (Calamari)

Mackerel (King)



Trout (Freshwater)

Orange roughy






Moderate mercury

Bass (Striped, Black)

Tuna (Bigeye, Ahi)


Least mercury: Less than 0.09 parts per million (ppm)

Moderate mercury: 0.09-0.29 ppm; safe to eat six or less servings each month

High mercury: 0.3-0.49 ppm, safe to eat three or less servings each month

Highest mercury: More than 0.5 ppm; avoid eating

SOURCE: Menon, Shanti. “Mercury Guide.” National Resources Defense Council. (accessed April 5, 2018).


Mercury (Hg) is a naturally occurring element in air, water, and soil. There are three forms of mercury that pose different potential health hazards:

Because the body cannot easily rid itself of mercury, repeated exposure result in its build up in tissues. Elemental mercury vapor and methylmercury are the most dangerous forms because they readily reach the brain. Most humans have trace amounts of methylmercury in their bodies. Methylmercury crosses the placenta to the developing fetus, whose red blood cells can have mercury concentrations that are 30% higher than those of the mother. It also passes to the newborn child through breast milk. Fetuses, infants, and young children are significantly more sensitive to the effects of mercury than adults. During the 1950s, large amounts of organic mercury were dumped in Japan's Minamata Bay, killing some 1,000 people and causing severe nervous system damage in unborn children. Thus mercury poisoning is sometimes called fetal Minamata Bay disease. Mercury poisonings have also occurred from eating meat from animals fed contaminated grain.

Risk factors

Causes and symptoms

The most common cause of mercury poisoning is eating fish and shellfish contaminated with high levels of methylmercury. Less common causes of mercury poisoning include:

The same level of mercury vapor can result in higher mercury concentrations in children than in adults, because children have larger lung surface areas for their body weight. Furthermore, since mercury vapors are more dense than air, there are higher levels closer to the ground where children breathe in the vapors. Although elemental mercury vapor is only slowly absorbed through the skin, it can irritate the skin and eyes and cause contact dermatitis. Touching or swallowing elemental liquid mercury is usually not harmful because it rolls off the skin and very little is absorbed by the gastrointestinal tract.

The effects of mercury exposure depend on a variety of factors including the:

Symptoms of elemental mercury poisoning appear within a few hours of exposure to high levels of vapor. Smaller amounts inhaled daily cause symptoms that develop over time. Symptoms can include:

Unlike elemental mercury, inorganic and organic mercury are absorbed through the intestinal tract, although a swallowed battery may pass harmlessly through a child. Symptoms of inorganic mercury poisoning include:

Methylmercury can interfere with the neurological development of fetuses, infants, and children, causing:

Symptoms of organic mercury poisoning most often develop over years or decades and include:



The child's vital signs—including temperature, pulse, breathing rate, and blood pressure—will be monitored. Important diagnostic information includes:


Blood or urine samples can be tested for exposure to elemental and inorganic mercury. Exposure to methylmercury is measured in whole blood or scalp hair. Mercury levels are often expressed as parts per million (ppm). For example, 1 ppm mercury in hair is equal to 1 milligram (mg) per kilogram (kg) of hair. The average mercury level in the hair of unaffected people is 2 ppm. Blood and urine tests may also be used to detect kidney damage from mercury poisoning.




Although inhaled elemental mercury poisoning can be difficult to treat, possibilities include:

Inorganic mercury poisoning is treated with supportive measures, including possibly intravenous fluids and electrolytes.

Treatment for methylmercury poisoning depends on the severity and is similar to treatments for cerebral palsy. It may include fluids and electrolytes and kidney dialysis.


Chelators—drugs that bind mercury and other heavy metals—may be required for weeks or months to remove mercury from the blood and protect the kidneys and brain. Other medications to treat mercury poisoning include:


There are various alternative types of chelation therapy. These include bentonite clay baths and combinations of herbs, amino acids, and other nutritional supplements.

Home remedies

Mercury poisoning should be treated by immediately removing the child from the source of exposure, if possible.



The U.S. Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) recommend that young children and women who are pregnant, may become pregnant, or are nursing:

Button batteries—
Tiny, round batteries containing mercuric chloride that power items such as watches, hearing aids, calculators, cameras, and penlights.
Cerebral palsy—
Brain damage before, during, or just after birth that results in lack of muscle coordination and problems with speech.
Various compounds that bind to metals such as mercury.
Contact dermatitis—
Skin inflammation from contact with an allergen or other irritating substance.
Elemental mercury (Hg)—
Metallic mercury; quicksilver; a heavy, silvery, poisonous metallic element that is a liquid at room temperature but vaporizes readily.
Inorganic mercury—
Inorganic compounds such as mercuric oxide (HgO) and mercuric chloride (HgCl2).
Mercuric chloride; mercury(II) chloride (HgCl2)—
A poisonous crystalline form of inorganic mercury that is used as a disinfectant and fungicide.
Any of various toxic compounds containing the organic grouping CH3Hg. These compounds occur as industrial by-products and pesticide residues, accumulate in fish and other organisms, especially those high on the food chain, and are rapidly absorbed through the human intestine to cause neurological disorders such as Minamata disease.
Organic mercury—
Poisonous compounds containing mercury and carbon, such as methylmercury, ethylmercury, and phenylmercury.
A crystalline organic mercury compound used as an antifungal and antibacterial agent and present in very small amounts in some vaccines.

Other preventions for mercury poisoning include:




Groth, Edward. Over the Limit: Eating Too Much High-Mercury Fish. Montpelier, VT: Mercury Policy Project, 2008.


Brennan, Richard J., “Nightmare of Mercury Poisoning Returns,” Toronto Star, April 6, 2010, A1.

Daley, Beth, “Mercury Leaks Found as New Bulbs Break; Energy Benefits of Fluorescents May Outweigh Risk,” Boston Globe, February 26, 2008, B2.

Haggart, Kelly. “Mercury Research Bears Fruit in the Amazon.” Women & Environments International no. 76/77 (fall/winter 2008): 5–8.

Philibert, Aline, Maryse Bouchard, and Donna Mergler. “Neuropsychiatric Symptoms, Omega-3, and Mercury Exposure in Freshwater Fish-Eaters.” Archives of Environmental & Occupational Health 63, no. 3 (fall 2008): 143–53.


Agency for Toxic Substances and Disease Registry, Centers for Disease Control and Prevention. “Mercury and Your Health.” (accessed April 9, 2018).

Agency for Toxic Substances and Disease Registry, Centers for Disease Control and Prevention. “Mercury Quick Facts: Health Effects of Mercury Exposure.” ToxFAQs. (accessed April 9, 2018).

Besser, Richard E. “Children's Exposure to Elemental Mercury: A National Review of Exposure Events.” Agency for Toxic Substances and Disease Registry, Centers for Disease Control and Prevention, Mercury Workgroup, February 2009. (accessed April 9, 2018).

MedlinePlus. “Mercury.” U.S. National Library of Medicine, National Institutes of Health. (accessed April 9, 2018).

U.S. Environmental Protection Agency. “Mercury in Your Environment.” (accessed April 9, 2018).

U.S. Environmental Protection Agency. “What You Need to Know about Mercury in Fish and Shellfish.” (accessed April 9, 2018).


Agency for Toxic Substances and Disease Registry (ATSDR), 4770 Buford Hwy. NE, Atlanta, GA, 30341, (888) 422-8737; (800) 232-4636, Fax: (770) 488-4178,, .

National Institute of Neurological Disorders and Stroke (NINDS), NIH Neurological Institute, PO Box 5801, Bethesda, MD, 20824, (301) 496-5751, (800) 352-9424, .

U.S. Environmental Protection Agency (EPA), Ariel Rios Building, 1200 Pennsylvania Ave. NW, Washington, DC, 20460, .

U.S. Food and Drug Administration (FDA), 10903 New Hampshire Ave., Silver Spring, MD, 20993-0002, (888) INFO-FDA, .

Margaret Alic, PhD

  This information is not a tool for self-diagnosis or a substitute for professional care.