Mercury Facts

What is mercury?

Mercury is a persistent bioaccumulative neurotoxin. This means that 1) it does not break down naturally, 2) it concentrates in animals higher on the food chain, and 3) it can cause permanent brain damage to developing children. Mercury is so toxic that even a single drop deposited annually from the atmosphere into a 20 acre lake is enough to contaminate all of the fish in the lake. Scientists estimate that if all man made mercury emissions stopped today, it would take at least 15 years to eliminate mercury in the environment.

Products that Contain Mercury

Mercury is found in numerous consumer products including thermometers, fluorescent lamps, thermostats, some lighted athletic shoes, fungicides for seeds and turf, dental fillings (amalgams), some oil-based paints, old latex paints (pre-August 1990), chemistry sets, flame sensors and safety valves, residential furnaces/boilers and boiler controls, cathode ray tubes, batteries (some button batteries), calculators and small appliances, medical laboratory chemicals, mercury vapor lamps, hearing aides, pilot lights, some medicines (such as mercurochrome) and some common household cleaners.

Alternatives exist for almost every mercury-containing product.

View a Mercury in Common Household Products fact sheet from the Rhode Island Department of Environmental Management

The health effects of mercury

Mercury is a powerful neurotoxin - it is highly damaging to the brain and nervous system.Humans are most commonly exposed to mercury by eating contaminated fish (see fish warnings). Mercury exposure can hurt the ability of children to pay attention, remember, talk, draw, run see, and play. Even exposure to low levels can permanently damage the brain and nervous system and cause behavior changes.

The effects of mercury exposure can be most severe for young children and for the developing fetus. In pregnant women, mercury can readily pass through the placenta to the fetus, where it harms fetal development by preventing the brain and nervous systems from developing normally. So the people that need to be the most cautious about what fish to eat are pregnant women, women who may become pregnant (because mercury stays in your body for a long time), nursing mothers (who can pass the mercury to the child through breast milk), and young children.

A growing number of studies have demonstrated the pervasiveness and severity of mercury contamination. The National Academy of Sciences July 2000 report showed the risk of mercury exposure to fetal development is so great that at least 60,000 newborns each year could be at risk for learning and developmental problems from mercury exposure.

A March 2001 Centers for Disease Control study found that one in ten women of childbearing age in the U.S. have more mercury in their bodies than the Environmental Protection Agency considers safe for a fetus's development.

In November 2002, the National Institutes of Health released a report showing that anyone who eats a lot of fish may experience health problems from mercury exposure.

Adults can also be affected by mercury exposure. Adults who are particularly sensitive to mercury or who consume a lot of fish may experience memory loss, tingling of the hands or feet, reduced muscle control, and other similar problems. Mercury exposure may also be linked to heart disease, infertility, lung damage, and other health problems in adults.

Sources of mercury pollution

Mercury is emitted into the air from man-made sources such as trash incinerators, medical waste incinerators , and coal fired power plants.

Trash and medical waste incinerators: When products that contain mercury (see above) are thrown away they are often burned in incinerators. Mercury changes easily from a liquid to a gas, so when the product is burned, the mercury vaporizes and goes up the smoke stack of the incinerator to the air.

Fossil fuel burning power plants: Fossil fuels, especially coal, naturally contain mercury. As in incinerators, the mercury in the coal vaporizes easily and goes up the smoke stack of the power plant and into the air. Although some power plants have devices on their stacks to collect the mercury, these devices don’t collect all the mercury and some still is emitted into the air.

Mercury emitted into the air then falls with the rain onto land and into lakes, rivers, ponds, and the ocean. Airborne mercury can travel long distances over state and national boundaries.

Mercury also enters water bodies when it leaches from landfills and when it is released into municipal sewers through discharges from health care facilities, dental offices, businesses, and households.

Landfills: When mercury products that are thrown in the trash aren’t burned in incinerators they go into landfills. The ash from incinerators and power plants is also disposed of in landfills. Mercury gets in to the water when it leaches out of landfills.

Dental offices: Most dentists use amalgam (or “silver”) fillings for tooth restoration that are about 50% mercury. When a dentist discards excess material after installing a filling or removes a filling from a patient’s mouth, the mercury-containing amalgam is usually rinsed down the drain, into the sewers, and into a river, a lake, or the ocean.

Mercury and fish

Once elemental mercury gets into lakes, streams, rivers, or the ocean, bacteria convert it to methyl mercury, its organic and most toxic form. Methyl mercury is easily absorbed by the human body, and by other animals, and it once it enters the body it can stay for a long time. For this reason, mercury “bioaccumulates” up the food chain, meaning that it concentrates in greater amounts in fish higher on the food chain. Older fish and/or bigger predatory fish will have greater amounts of mercury than smaller fish, younger fish.

Humans are at the top of the food chain. The most common way humans are exposed to mercury is by eating mercury contaminated fish. For information about which fish to avoid and which are safe to eat, visit the fish warnings page.