MERCURY
 

CAS # 7439-97-6 

Agency for Toxic Substances and Disease Registry ToxFAQs April 1999 

This fact sheet answers the most frequently asked health questions (FAQs) about mercury. For more information, 

call the ATSDR Information Center at 1-888-422-8737. This fact sheet is one in a series of summaries about 

hazardous substances and their health effects. It’s important you understand this information because this 

substance may harm you. The effects of exposure to any hazardous substance depend on the dose, the duration, 

how you are exposed, personal traits and habits, and whether other chemicals are present. 

HIGHLIGHTS: Exposure to mercury occurs from breathing contaminated air, 

ingesting contaminated water and food, and having dental and medical treatments. 

Mercury, at high levels, may damage the brain, kidneys, and developing fetus. This 

chemical has been found in at least 714 of 1,467 National Priorities List sites identified 

by the Environmental Protection Agency. 

What is mercury? 

(Pronounced mÎr kyí-r≤) 

Mercury is a naturally occurring metal which has several 

forms. The metallic mercury is a shiny, silver-white, odorless 

liquid. If heated, it is 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. The most common one, methylmercury, is produced 

mainly by microscopic organisms in the water and soil. More 

mercury in the environment can increase the amounts of 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 sometimes used in skin lightening creams and as antiseptic creams and ointments. 

What happens to mercury when it enters the 

environment? 

o Inorganic mercury (metallic mercury and inorganic mercury compounds) enters the air from mining ore deposits, 

burning coal and waste, and from manufacturing plants. 

o It enters the water or soil from natural deposits, disposal of 

wastes, and volcanic activity. 

o Methylmercury may be formed in water and soil by small 

organisms called bacteria. 

o Methylmercury builds up in the tissues of fish. Larger and 

older fish tend to have the highest levels of mercury. 

How might I be exposed to mercury? 

o Eating fish or shellfish contaminated with methylmercury. 

o Breathing vapors in air from spills, incinerators, and industries that burn mercury-containing fuels. 

o Release of mercury from dental work and medical treatments. 

o Breathing contaminated workplace air or skin contact during use in the workplace (dental, health services, chemical, 

and other industries that use mercury). 

o Practicing rituals that include mercury. 

How can mercury affect my health? 

The nervous system is very sensitive to all forms of mercury. Methylmercury and metallic mercury vapors are more 

harmful than other forms, because more mercury in these forms 

reaches the brain. Exposure to high levels of metallic, inorganic, or organic mercury can permanently damage the brain, 

kidneys, and developing fetus. Effects 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, 

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES, Public Health Service 

Agency for Toxic Substances and Disease Registry 
 

Page 2 

Federal Recycling Program Printed on Recycled Paper 

ToxFAQs Internet address via WWW is http://www.atsdr.cdc.gov/toxfaq.html 

Where can I get more information? For more information, contact the Agency for Toxic Substances and Disease 

Registry, Division of Toxicology, 1600 Clifton Road NE, Mailstop F-32, Atlanta, GA 30333. Phone: 1-888-422-8737, 

FAX: 770-488-4178. ToxFAQs Internet address via WWW is http://www.atsdr.cdc.gov/toxfaq.html ATSDR can tell you 

where to find occupational and environmental health clinics. Their specialists can recognize, evaluate, and treat illnesses 

resulting from exposure to hazardous substances. You can also contact your community or state health or environmental 

quality department if you have any more questions or concerns. 

MERCURY 

CAS # 7439-97-6 

vomiting, diarrhea, increases in blood pressure or heart rate, 

skin rashes, and eye irritation. 

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 EPA has determined that mercuric chloride and methylmercury are possible 

human carcinogens. 

How can mercury affect children? 

Very young children are more sensitive to mercury than 

adults. Mercury in the mother’s body passes to the fetus and 

may accumulate there. It can also can pass 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. 

Mercury’s harmful effects that may be passed from the 

mother to the fetus include brain damage, mental retardation, 

incoordination, blindness, seizures, and inability to speak. 

Children poisoned by mercury may develop problems of their 

nervous and digestive systems, and kidney damage. 

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 exposure. If a large amount of mercury has been 

spilled, contact your health department. 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 women and children should keep away from 

rooms where liquid mercury has been used. 

Learn about wildlife and 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 to inorganic forms of mercury. Mercury in whole 

blood or in scalp hair is measured to determine exposure to 

methylmercury. Your doctor can take samples and send them to 

a testing laboratory. 

Has the federal government made 

recommendations to protect human health? 

The EPA has set a limit of 2 parts of mercury per billion 

parts of drinking water (2 ppb). 

The Food and Drug Administration (FDA) has set a maximum permissible level of 1 part of methylmercury in a million 

parts of seafood (1 ppm). 

The Occupational Safety and Health Administration 

(OSHA) has set limits of 0.1 milligram of organic mercury per 

cubic meter of workplace air (0.1 mg/m3) and 0.05 mg/m3 of 

metallic mercury vapor for 8-hour shifts and 40-hour work 

weeks. 

References 

Agency for Toxic Substances and Disease Registry 

(ATSDR). 1999. Toxicological profile for mercury. Atlanta, 

GA: U.S. Department of Health and Human Services, Public 

Health Service.