Smarter Living: Chemical Index

Exposure to mercury, even at low levels, can cause neurological damage, memory and learning problems, and delays in speech and reading ability in children. Most people are exposed to mercury by eating contaminated fish.

Health Concerns

Elemental (metallic) mercury and all of its compounds are toxic, exposure to excessive levels can permanently damage or fatally injure the brain and kidneys. Elemental mercury can also be absorbed through the skin and cause allergic reactions. Ingestion of inorganic mercury compounds can cause severe renal and gastrointestinal damage. Organic compounds of mercury such as methyl mercury are considered the most toxic forms of the element. Exposures to very small amounts of these compounds can result in devastating neurological damage and death.

For fetuses, infants and children, the primary health effects of mercury are on neurological development. Even low levels of mercury exposure such as result from mother's consumption methylmercury in dietary sources can adversely affect the brain and nervous system. Impacts on memory, attention, language and other skills have been found in children exposed to moderate levels in the womb.


Air borne mercury is highly toxic when inhaled. How does it get in the air? Metallic mercury slowly evaporates when exposed to the air. The air in a room can reach unhealthy levels just from the mercury in a broken thermometer;

Most people are exposed to mercury by eating contaminated fish. How does mercury get in fish? It's released into the air when coal, oil, or wood are burned as fuel or when mercury-containing wastes are incinerated. The resulting mercury concentrations in outdoor air are usually low and of little direct concern. However, mercury in the air can fall to the ground with rain and snow, landing on soil or in bodies of water, causing contamination. Lakes and rivers are also contaminated when there is a direct discharge of mercury-laden industrial or munici pal waste into the water.

When mercury enters bodies of water, biological processes transform it to methylmercury, a highly toxic and bioaccumulative form. Fish can absorb methylmercury from their food and directly from water as it passes over their gills. The largest predatory fish at the top of the food chain, such as swordfish, bigeye tuna and ahi tuna, tend to have higher amounts of methylmercury in their bodies--enough to be a health concern for young children and pregnant women in particular.

Mercury can also be found in silver amalgam dental fillings, button batteries (the kind used in watches, calculators, pacemakers, etc.), thermostats, swtiches, compact fluorescent lighting and in some cosmetic skin-lightening and acne creams sold outside the United States. Mercury is used to manufacture chlorine for bleach and other industrial products, and to make hard plastics in China. It is widely used in small-scale gold mining throughout the developing world. Mercury pollution travels great distances in the air, making it a global environmental problem.

Stay Safe

Eat fish low in mercury. Use NRDC's Consumer Guide to Mercury in Fish to find out what's safe to eat.

Avoid silver dental fillings. If you already have them, do not rush to remove them--drilling vaporizes mercury, increasing your risk of exposure.

Don't use skin-lightening or acne creams purchased abroad, as they may contain mercury.

Most routine childhood immunizations do not contain mercury. Thimerosal, a preservative containing mercury, was removed from children's vaccines in the early 1990s. Some flu vaccines may still contain thimerosal, but parents can request a thimerosal-free version.

Compact fluorescent light (CFL) bulbs contain a small amount of mercury. Broken bulbs may release this mercury, so follow the disposal instructions listed in Compact Fluorescent Lights: The Mercury Matter. Note: Although CFLs contain some mercury, they consume less power than inefficient incandescent bulbs, and thus help to reduce the demand on power plants that emit airborne mercury pollution.

Take action

You can take precautions to limit your mercury exposure, but stopping mercury pollution at its source is the best way to protect our health. NRDC and other groups are fighting to clean up power plant pollution and pushing for clean, green energy. Our health team is working to clean up or shut down the last mercury chlor-alkali plants in the country, and pushing the EPA to set tough standards on pollution from cement kilns.

We also need to get mercury out of consumer product--NRDC has already helped eliminate the mercury fever thermometer, and mercury is being phased out of many batteries manufactured in the United States. In 2008, the United States banned the export of mercury, reducing the amount of this dangerous metal on the world market. But other countries still use mercury in their industries, tainting the air and waters across the planet. NRDC is helping lead the way in forging an international treaty to slash mercury pollution worldwide.

Learn More

Agency for Toxic Substances and Disease Registration, ToxFAQs for Mercury, August 1999,

Consumer Guide to Mercury in Fish

Compact Fluorescent Lights: The Mercury Matter

last revised 12/28/2011

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