People can be exposed to mercury by breathing in air, eating food, or drinking water contaminated with mercury compounds. Mercury can also enter the body through contact with the skin.

Mercury is released into the air from natural sources like volcanoes and off-gassing from the earth's crust and bodies of water. Mercury can also be released into the air through the incineration of waste, the burning of coal by power plants, and by industries that use mercury to manufacture products. Mercury in the air eventually falls back to earth and accumulates in bodies of water. Fish absorb mercury through their gills and by eating contaminated food sources. Mercury becomes most concentrated in fish that eat smaller fish.

Exposure to mercury is also possible through dental amalgams (fillings), which contain 50 percent mercury. Occasional exposure to mercury can also occur from broken thermometers. Lastly, practitioners of certain religions, such as Esperitismo, Santeria, or Voodoo have been known to use mercury in rituals.

According to ATSDR, "Tests are available to measure mercury levels in the body. Blood or urine samples are used to test for exposure to metallic mercury and to inorganic forms of mercury. Measurement of mercury in whole blood or in scalp hair is used to measure exposure to methylmercury. Your doctor can take samples and send them to a testing laboratory" (ATSDR ToxFAQ April 1999).

Body levels of mercury are often expressed in terms of parts per million (ppm), 1 part of mercury per million parts of body tissue. As an example, a hair concentration of 1 ppm mercury is equal to 1 milligram of mercury per kilogram of hair. In people who have not been exposed to high levels of mercury, the average level of mercury in the hair is 2 ppm (FDA Consumer, September 1994).

If mercury escapes into the environment, evacuate children and pregnant women. Remove all jewelry, especially gold. Handle the mercury carefully. Wear rubber gloves and scoop it onto a sheet of paper or suck it up with an eyedropper. Place the mercury in a medicine vial or similar airtight container. The scoop, paper or eyedropper should also be bagged and disposed properly according to guidance provided by environmental officials or your local health department. Ventilate the room to the outside and close off the rest of the home. Use fans for a minimum of one hour to speed the ventilation. Do not simply throw the mercury away. Seek professional guidance from local recycling, solid waste or hazardous waste agencies. Large retailers and building centers may accept glass-encapsulated mercury, as in thermostats, for recycling.

Keep any objects containing mercury out of the reach of children. Children found to be playing with liquid mercury or broken fluorescent lamps should be referred to a physician or poison control center immediately.

Mercury contaminated gold jewelry must be taken to a jeweler to have them professionally cleaned.

While handling mercury, or any other hazardous substance, one should always wear protective gloves. If mercury contacts with the skin, wash the area(s) thoroughly and immediately with soap and warm water. If you believe that you have absorbed mercury though your skin or inhaled mercury vapors, you should contact your physician or poison control center immediately.

A vacuum cleaner should never be used to clean mercury spills. According to ATSDR (ATSDR National Alert: A Warning About Continuing Patterns of Metallic Mercury Exposure), "Using a vacuum cleaner causes metallic mercury to vaporize in the air, creating greater health risks. It also ruins the vacuum cleaner."

Persons who use metallic mercury in ethnic folk medicine and for religious practices are at risk. Metallic mercury is sold under the name "azogue" in stores (sometimes called botanicas), which specialize in religious items used in Esperitismo (a spiritual belief system native to Puerto Rico), Santeria (a Cuban-based religion that venerates both African deities and Catholic saints), and voodoo.

The use of azogue in religious practices is recommended in some Hispanic communities by family members, spiritualists, card readers, and santeros. Typically, azogue is carried on one's person in a sealed pouch prepared by a spiritual leader or sprinkled in the home or automobile. Some botanica owners suggest mixing it in bath water or perfume and placing it in devotional candles.

According to ATSDR, "Exposure to high levels of metallic, inorganic, or organic mercury can permanently damage the brain, kidneys, and developing fetus" (ATSDR ToxFAQ April 1999). FDA toxicologist, Dr. Mike Bolger, stated that "Methyl mercury easily crosses the placenta, and the mercury concentration rises to 30 percent higher in fetal red blood cells than in those of the mother"(FDA Consumer, September 1994). The adverse health effects of mercury on unborn children were observed in cases of accidental poisonings and in studies of individuals who ate large amounts of seafood, a common source of mercury.

In the 1950's, large of amounts of organic mercury were released into the Minamata Bay in Kyushu, Japan (Environmental Health Perspectives, Volume 104, April 1996). Many individuals who ate mercury-contaminated fish and shellfish from the bay developed severe damage to the nervous system and many eventually died. Symptoms caused by the mercury poisoning were referred to as Minamata Disease. Fetal Minamata Disease developed in about 7% of children whose mothers ate contaminated fish while pregnant. Symptoms of Fetal Minamata Disease include uncoordinated movements, abnormal reflexes, speech problems, and seizures. Fetuses were found to be much more sensitive to mercury than were their mothers. The nervous systems of some mothers of children with Fetal Minamata Disease were only mildly affected; a common symptom was a narrowing of the visual field. The level of mercury in the mothers who gave birth to affected children after eating mercury-contaminated fish is not certain, but generally, nerve damage was seen in adults with mercury levels in hair of 50 ppm or higher (EHP, Volume 104(8), August 1996).

The following excerpt describes a case of accidental mercury poisoning in Iraq (FDA Consumer, September 1994):

Studies of the poisoning incident in Iraq have provided limited data about what effects low levels of methyl mercury exposures to the fetus have on the infant. One possible effect, for example, is lateness in walking. In the fall and winter of 1971-72, wheat seed intended for planting--and which had therefore been treated with an alkyl mercury fungicide--was mistakenly used to prepare bread; more than 6,500 Iraqis were hospitalized with neurological symptoms and 459 died. The vast majority of the mothers experienced exposures that resulted in hair levels greater than the lowest levels associated with effects in adults. But there was no clear evidence that the fetus was more sensitive than the adult to methyl mercury.

From an analysis of the Iraqi poisoning case, it was estimated that there is about a 5% chance that fetuses could be affected if their mothers have a hair level of 10-20 ppm mercury (EHP, Volume 104(8), August 1996)

The U.S. National Institute of Environmental Health Sciences (NIEHS) and the European Commission sponsored a mercury health study in the Faroe Islands in the North Atlantic. People on these islands are exposed to mercury mainly by eating whale meat (NIEHS PR #24-97, November 1997). Pregnant women in the study had hair mercury levels of 10-20 ppm (EHP, Volume 107(1), January 1999). To determine the effects of mercury intake by pregnant women, 7-year-old children were tested for brain function by measuring their attention span, memory, and speaking ability. Children born to mothers who had higher concentrations of mercury in their hair and umbilical cords scored lower on the brain function tests. Professor Roberta F. White of Boston University looked at the study results and concluded that "Several domains of brain function may be affected by prenatal methylmercury exposure. Most of the results remained within normal ranges, but any developmental delay in young children may be a concern.

The NIEHS also sponsored a study to examine the effects of mercury on unborn children from the Seychelles Islands in the Indian Ocean (NIEHS, February 7, 1996). The residents of the islands eat fish about 12 times a week and the average concentration of mercury in the hair of women is 10 ppm. However, some woman had hair levels of mercury as high as 36 ppm. Children were tested for mental and physical ability from the ages of 6 months to five years. The researchers concluded that "Cognitive developmental outcomes up to 2 years of age appear essentially normal following intrauterine exposure to a maternal hair mercury level of about 6 ppm through maternal fish consumption." They went on to say that "although data at older ages is [sic] needed, the results available so far indicate that low-level mercury exposure from eating fish during pregnancy shows no harmful effect." Philip Davidson of the University of Rochester stated, "If somebody who eats fish twice a day does not show effects from mercury exposure, it's unlikely that somebody who eats fish twice a week will be affected, and the fish they eat in the Seychelles contains the same amount of mercury as fish sold at supermarkets and eaten in the United States" (NIEHS Center Program, September 1998).

Reviews of the Faroe Islands and Seychelles Islands studies are continuing as scientists try to determine why different results were obtained. One scientific panel concluded that discrepancies may have resulted from dietary differences or ethnic variability (EHP Volume 107(1), January 1999). The whale meat eaten by residents of the Faroe Islands also contained PCBs, which may have affected study results. However, scientists did take this into account when evaluating the Faroe Islands study results (NIEHS PR #24-97, November 1997).