Mercury FAQs -
Frequently Asked Questions
- What is mercury?
- How does mercury occur in the environment?
- How do people and wildlife become exposed to mercury?
- How does mercury affect human health?
- Is any exposure to mercury harmful to people?
- How are people exposed to methylmercury and what are the health effects?
- What are the sources of exposure to other forms of mercury and what are their health effects?
- How should I handle mercury?
- What should I do if I spill mercury?
- What should I do to dispose of mercury?
- What should I do if I have elemental mercury in my home?
- What can I do to reduce the amount of mercury in the environment?
- What are the biggest sources of mercury air emissions in the U.S.?
Mercury is a naturally occurring element that is found in air, water and soil. It exists in several forms: elemental or metallic mercury, inorganic mercury compounds, and organic mercury compounds. Elemental or metallic mercury is a shiny, silver-white metal and is liquid at room temperature. It is used in thermometers, fluorescent light bulbs and some electrical switches. When dropped, elemental mercury breaks into smaller droplets which can go through small cracks or become strongly attached to certain materials. At room temperature, exposed elemental mercury can evaporate to become an invisible, odorless toxic vapor. People can be exposed to elemental mercury vapor when products that contain mercury break and expose mercury to the air, particularly in poorly-ventilated spaces.
Inorganic mercury compounds take the form of mercury salts and are generally white powder or crystals, with the exception of mercuric sulfide (cinnabar) which is red. Inorganic mercury compounds have been included in products such as fungicides, antiseptics or disinfectants. Some skin lightening and freckle creams, as well as some traditional medicines, can contain mercury compounds.
Organic mercury compounds, such as methylmercury, are formed when mercury combines with carbon. Microscopic organisms convert inorganic mercury into methylmercury, which is the most common organic mercury compound found in the environment. Methylmercury accumulates up the food chain.
Mercury is a naturally occurring element that can be found throughout the environment. Human activities, such as burning coal and using mercury to manufacture certain products, have increased the amount of mercury in many parts of the environment including the atmosphere, lakes and streams. People and animals are exposed to mercury by eating organisms that live in places where microbes have converted some of the natural and human mercury to a more toxic form, methylmercury.
The primary way people in the U.S. are exposed to mercury is by eating fish containing methylmercury.
Mercury in the atmosphere is eventually deposited to the earth's surface, either through dry or wet deposition (rain or snow). When mercury falls from the air or runs off the ground into the water, certain microorganisms in soils and sediments convert some part of it into methylmercury, a highly toxic form of mercury.
Small organisms take up methylmercury as they feed. When animals higher up the food chain eat the smaller ones, they also take in the methylmercury. As this process, (known as bioaccumulation), continues, levels of methylmercury increase up the food chain. Fish that are higher in the food chain, such as sharks and swordfish, have much greater methylmercury concentrations than fish that are lower on the food chain. This is true for both saltwater and freshwater fish. People and fish-eating wildlife become exposed when they eat fish and shellfish that contain methylmercury. There are ways in which people are exposed to other forms of mercury as well.
How Does Mercury Affect Human Health
High levels of mercury in the bloodstream of unborn babies and young children may harm the developing nervous system. Whether an exposure to mercury will harm a person's health depends on a number of factors. Almost all people have at least trace amounts of mercury in their tissues, reflecting mercury’s widespread presence in the environment. People may be exposed to mercury in any of its forms under different situations. The factors that determine how severe the health effects are from mercury exposure include:
- the chemical form of mercury - elemental (metallic), inorganic compounds, or organic compounds
- the dose -- how much
- the duration of exposure -- how long
- the route of exposure -- eating, breathing, injecting, touching other chemical exposures
- the specific characteristics of the person - age, health
The effects of mercury exposure can be very severe, subtle, or may not occur at all, depending on the factors above. Mercury can affect the nervous system. Because fetuses, infants, and children are still developing, they are particularly sensitive to the effects of methylmercury on the nervous system. People are mainly exposed to methylmercury, an organic compound, when they eat fish and shellfish that contain methylmercury.
Nearly all methylmercury exposures occur through eating fish and shellfish. Microscopic organisms convert inorganic mercury into methylmercury, which accumulates up the food chain in fish, other fish-eating animals, and people.
Some fish contain more methylmercury than others. Big fish that eat smaller fish tend to contain more methylmercury. Both EPA and the Food and Drug Administration have issued advice to pregnant women about how often they should eat certain types of fish. States issue fish advisories that tell consumers about how often they should eat certain types and quantities of locally caught fish. Certain species of commercially available saltwater fish, such as shark, swordfish, kingfish and tilefish, can contain high levels of methylmercury. Outbreaks of methylmercury poisonings have made it clear that adults, children, and developing fetuses are at risk from ingestion exposure to mercury. During these poisoning outbreaks some mothers with no symptoms of nervous system damage gave birth to infants with severe disabilities, it became clear that the developing nervous system of the fetus may be more vulnerable to methylmercury than is the adult nervous system. Mothers who are exposed to methylmercury and breast-feed their babies may also expose their infant children through their milk. Research shows that most people's fish consumption does not cause a health concern. However, high levels of methylmercury in unborn babies and young children may harm the developing nervous system. With this in mind, FDA and EPA designed an advisory that if followed should keep an individual's mercury consumption below levels that have been shown to cause harm. By following the advisory, parents can reduce their unborn or young child's exposure to the harmful effects of methylmercury, while at the same time maintaining a healthy diet that includes the nutritional benefits of fish and shellfish.
Elemental or metallic mercury is the liquid metal used in thermometers, button cell batteries (standard household batteries do not contain mercury), electrical switches, and some folk remedies and religious practices. In household products, where elemental mercury generally is contained in glass or metal, it does not pose a risk unless the product is damaged or broken and mercury vapors are released. At room temperature, some uncontained mercury can evaporate and become an invisible, odorless toxic vapor. At higher temperatures, these concentrations increase. Very small amounts of elemental mercury (even a few drops) can raise air concentrations of mercury to harmful levels particularly in poorly-ventilated spaces. The longer people breathe the contaminated air, the greater the risk to their health. At high exposures, through inhalation, elemental mercury vapors can produce severe lung, gastrointestinal, and nervous system damage.
Inorganic mercury compounds take the form of mercury salts. They are generally white powders or crystals, with the exception of mercuric sulfide (cinnabar) which is red. Inorganic compounds, and organic compounds, such as phenylmercury acetate and ethylmercury, have been commonly used as fungicides, antiseptics or disinfectants. They also have been used in a variety of products. Most of these uses have been discontinued, but small amounts of these compounds can still be found as preservatives in some medicines.
Excessive exposure to inorganic and organic mercury compounds can result from misuse or overuse of mercury-containing products. Exposure to mercury compounds is primarily through ingestion, but can occur through other pathways. Organic mercury compounds are more readily absorbed through the gastrointestinal tract and skin than are inorganic compounds. High exposures to mercury compounds can damage the gastrointestinal tract, the nervous system, and the kidneys.
How Should I Handle Mercury
It is important to clean up mercury spills properly and promptly and to report them to the proper authorities when necessary. There are three different procedures to address mercury spills.
Never use a vacuum cleaner to clean up mercury. The vacuum will put mercury into the air and increase exposure. The vacuum appliance will be contaminated and have to be thrown away.
Never use a broom to clean up mercury. It will break the mercury into smaller droplets and spread them.
Never pour mercury down a drain. It may lodge in the plumbing and cause future problems during plumbing repairs. If discharged, it can cause pollution of the septic tank or sewage treatment plant.
Never wash mercury-contaminated items in a washing machine. Mercury may contaminate the machine and/or pollute sewage.
Never walk around if your shoes might be contaminated with mercury. Contaminated clothing can also spread mercury around.
Remove everyone from the area where cleanup will take place. Shut door of impacted area. Turn off ventilation system. DO NOT allow or gain assistance from children. Remember to remove all pets as well. Mercury can be cleaned up easily from the following surfaces: wood, linoleum, tile and any other like surfaces. If a spill occurs on carpet, curtains, upholstery or other like surfaces, these contaminated items should be thrown away in accordance with the disposal means outlined below. Only cut and remove the affected portion of the contaminated carpet for disposal.
Many people have containers of elemental mercury in their homes left over from science projects or other sources. Elemental mercury is a shiny, silver-gray metal that is liquid at room temperature. If you have elemental mercury in your home, you should exercise extreme caution with it and package and dispose of mercury to prevent any leaks or spills.
You can buy and use products that are mercury- free. You can make sure that you properly dispose of any mercury-containing items that you have. U.S. demand for mercury in products dropped 75 percent from 1988 to 1997 for several reasons, including: federal bans on mercury additives in paint and pesticides, industry efforts to reduce mercury in batteries, increasing state regulation of mercury emissions and mercury in products, and state recycling programs. Both the business community and the public can further contribute to reduce mercury releases to the environment by making or purchasing mercury-free products. They can also participate in state/local collection programs rather than throwing away mercury-containing products.
According to EPA's 1999 National Emissions Inventory, coal-fired electric power plants are the largest source of human-caused mercury air emissions in the U.S. These power plants account for about 40% of total U.S. manmade mercury emissions. Other large sources are industrial boilers (about 10% of U.S. mercury emissions), burning hazardous waste (about 5%), and chlorine production (also about 5%). Burning municipal waste and medical waste was once a larger source of emissions. Today, in response to EPA and state regulations and reductions in mercury use, emissions from these sources have declined 85-90 percent.
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