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Skip Navigation LinksPennsylvania Department of Health > My Health > Environmental Health > Environmental Fact Sheets > Mercury



What is Mercury?
Mercury is a naturally occurring metal that has several forms.  The metallic mercury is a shiny, silver-white, odorless liquid that is also called quicksilver.  When heated, it becomes a colorless, odorless gas. 
Mercury combines with other elements, such as chlorine, sulfur, or oxygen, to form inorganic mercury compounds or �salts,� which are usually white powders or crystals.  Mercury also combines with carbon to make organic mercury compounds (methylmercury).  Microscopic organisms in water and soil produce the most common type of mercury, methylmercury.  The more mercury there is in the environment, the more methylmercury that these small organisms make.
Metallic mercury is used to produce chlorine gas and caustic soda, and is also used in thermometers, dental fillings, and batteries. Mercury salts are occasionally used in skin lightening creams and as antiseptic creams and ointments.
What happens to mercury when it enters the environment?  
Inorganic mercury occurs naturally in very small amounts in oceans, rocks, and soils.  It becomes airborne when rocks erode, volcanoes erupt, and soil decomposes. Then the mercury circulates in the atmosphere and is redistributed throughout the environment.  Large amounts of mercury become airborne when coal, oil or natural gases are burned as fuel or mercury-containing garbage is incinerated.  Once in the air, mercury can fall to the ground with rain & snow, landing on soils or water bodies, causing contamination. There could also be direct discharge of mercury-laden industrial waste or municipal sewage into the environment.  
How might I be exposed to mercury?


Today, mercury is released into the environment from many sources.  It is used in household and commercial products, as well as industrial processes.  Coal-fired power plants, incinerators, some manufacturing plants, hospitals, dental offices, schools (science and chemistry classrooms, the nurse�s office and electrical systems), and even homes (fluorescent lights, thermostats, thermometers, and some children�s toys), can release mercury. 
The more toxic form of mercury, methylmercury, builds up in the tissues of animals all the way up the food chain to man.  Mercury that deposits in water bodies accumulates as methylmercury in fish and may ultimately reach the dinner table.  Larger and older fish tend to have the highest levels of mercury.  Once the methylmercury is in the body it can have long lasting health effects, especially on fetal development during pregnancy.  Excess mercury has been linked to nervous system, kidney, and liver damage, and impaired childhood development.  The nervous system disorders that may occur with excess mercury include impaired vision, speech, hearing, and coordination.  Another way to be exposed to mercury is to breathe in vapors in the air from spills of metallic mercury.  You can breathe mercury contaminated air at the workplace or have skin contact with mercury while at work (dental, health services, chemical and other industries that use mercury).  It is possible to breathe in mercury vapors in the air around spills, incinerators, and industries that burn mercury-containing fuels.
How can mercury affect my health?


The nervous system is very sensitive to all forms of mercury. However, methylmercury and metallic mercury vapors are the most harmful forms because their mercury reaches the brain.  Exposures to high levels of metallic, inorganic, or organic mercury can permanently damage the brain, the kidneys, or the developing fetus.  The effects of mercury on brain functioning may result in irritability, shyness, tremors, changes in vision or hearing, and memory problems.  
Short-term exposure to high levels of metallic mercury vapors may cause effects including lung damage, nausea, vomiting, diarrhea, increases in blood pressure or heart rate, skin rashes, and eye irritation.  Exposure to organic mercury is more dangerous for young children than for adults, because more of it passes into children�s brains where it interferes with normal development.
How likely is mercury to cause cancer?


There are inadequate human cancer data available for all forms of mercury. Mercuric chloride has caused increases in several types of tumors in rats and mice, and methylmercury has caused kidney tumors in male mice. The Environmental Protection Agency (EPA) has determined that both mercuric chloride and methylmercury are possible human carcinogens.
How can mercury affect children?


Very young children are more sensitive to mercury than are adults.  Mercury in the mother�s body passes to the fetus (before birth) where it may accumulate. The harmful effects of mercury that may be passed from the mother to the fetus include brain damage, mental retardation, incoordination, blindness, seizures, and the inability to speak.  Mercury can also pass from the mother to a nursing infant through breast milk.  However, the benefits of breast-feeding may be greater than the possible adverse effects of mercury in breast milk.  
How can families reduce the risk of exposure to mercury?
Carefully handle and dispose of products that contain mercury, such as thermometers or fluorescent light bulbs.  Do not vacuum up spilled mercury, because it will vaporize and increase your exposure.  If a large amount of mercury has been spilled, contact your local fire department and the emergency response program in your regional office of the Pennsylvania Department of Environmental Protection (DEP). Teach children not to play with shiny, silver liquids.  Properly dispose of older medicines that contain mercury.  Keep all mercury-containing medicines away from children.
Pregnant woman should keep away from the room where liquid mercury has been used.

Learn about wildlife and any fish advisories in your area, from your public health or natural resources department.
Is there a medical test to show whether I�ve been exposed to mercury?


Tests are available to measure mercury levels in the body.  Blood or urine samples are used to test for exposure to metallic mercury and for exposure to inorganic forms of mercury.  Mercury in whole blood or in scalp hair is measured to determine your exposure to methylmercury.  Your doctor can take samples and send them to a testing laboratory.
Regulatory and advisory standards


� The EPA has set a limit of two (2) parts of mercury per billion parts (2 ppb) of drinking water.
� The Food and Drug Administration (FDA) has set a maximum permissible level of one (1) part of methylmercury per million parts (1 ppm) of seafood.
� The Occupational Safety and Health Administration (OSHA) has set limits of 0.01 milligram of organic mercury per cubic meter (mg/m3) of workplace air for 8-hour shifts and 40-hour work weeks.  The OSHA has set a ceiling concentration of 0.1 mg/m3 for metallic mercury that must not be exceeded during any part of the workday.  If instantaneous monitoring is not feasible, the ceiling must be assessed as a 15-minute time-weighted-average (TWA) exposure.


Reference:  ToxFAQs for Mercury, U.S. Agency for Toxic Substances and Disease Registry.