Heavy Metals
Where does mercury come from?
In the U.S., coal-fired power plants are the biggest source of mercury emissions to the air. Alkali and metal processing, incineration of coal, and medical and other waste, and mining of gold and mercury contribute greatly to mercury concentrations in some areas, but atmospheric deposition is the dominant source of mercury over most of the landscape. Once in the atmosphere, mercury is widely disseminated and can circulate for years, accounting for its widespread distribution. Natural sources of atmospheric mercury include volcanoes, geologic deposits of mercury, and volatilization from the ocean. Although all rocks, sediments, water, and soils naturally contain small but varying amounts of mercury, scientists have found some local mineral occurrences and thermal springs that are naturally high in mercury. Small aquatic organisms eat compounds containing mercury, and the mercury moves up the food chain to larger fish and aquatic mammals.
www.usgs.gov/themes/factsheet/146-00/#toxic*http://www.epa.gov/mercury/
What are the toxic effects of mercury in our environment?
HUMAN HEALTH
The toxic effects of mercury depend on its chemical form and the route of exposure. Mercury may cause cancer, damage the stomach and large intestine, permanently damage the brain and kidneys, and permanently harm unborn children. Mercury can cause lung damage, and increase blood pressure and heart rate. Methylmercury [CH3Hg] is the most toxic form of mercury. It affects the immune system, alters genetic and enzyme systems, and damages the nervous system, including coordination and the senses of touch, taste, and sight. Methylmercury is particularly damaging to developing embryos, which are five to ten times more sensitive than adults. Children of women exposed to relatively high levels of methylmercury during pregnancy have exhibited a variety of abnormalities, including delayed onset of walking and talking, reduced neurological test scores, and delays and deficits in learning ability. Eight percent of the women of childbearing age have levels of mercury in their blood that exceeds the level EPA considers safe. In addition, there is growing evidence that methylmercury exposure can have adverse cardiovascular effects for adults, resulting in elevated blood pressure and incidence of heart attack.-Elemental mercury, Hg(0), the form released from broken thermometers, causes tremors, gingivitis, and excitability when vapors are inhaled over a long period of time.WILDLIFE HEALTH
In several areas of the United States, concentrations of mercury in fish and wildlife are high enough to be a risk to wildlife health. Fish-eating birds in certain parts of the United States may ingest large amounts of methylmercury in their diet, causing deformities in developing offspring.
www.usgs.gov/themes/factsheet/146-00/#toxic www.epa.gov/mercury/information1.htm www.epa.gov/opptintr/pbt/mercury.htm
How are humans exposed to mercury?
Humans can be exposed to mercury through eating contaminated fish and shellfish, accidental mercury spills, incinerators and facilities burning Hg-containing fuels (i.e. coal or other fossil fuels, mercury-containing wastes), and mother's blood (unborn children) and breast milk (infants)
Exposure to methylmercury is usually by ingestion, and it is absorbed more readily and excreted more slowly than other forms of mercury. People are most often exposed to methylmercury through eating contaminated fish and wildlife that are at the top of aquatic food chains. Although it is less toxic than methylmercury, elemental mercury may be found in higher concentrations in environments such as gold mine sites, where it has been used to extract gold. Ingestion of other common forms of mercury, such as the salt HgCl2, which damages the gastrointestinal tract and causes kidney failure, is unlikely from environmental sources.
www.usgs.gov/themes/factsheet/146-00/#toxic*http://www.epa.gov/opptintr/pbt/mercury.htm
How do I avoid mercury exposure?
Living in areas away from coal burning plants is a good start to limiting mercury exposure. Eating a diet that limits exposure to mercury containing fish is one of the most important ways to limit exposure in the diet. Younger fish tend to have lower concentrations of mercury than older, larger fish within the same body of water. Mercury concentrates in the muscle tissue of fish so, unlike PCBs, dioxins and other organic contaminants that concentrate in the skin and fat, mercury cannot be filleted or cooked out of consumable game fish. Predator fish - big fish that eat smaller fish - tend to have higher methylmercury concentrations than other fish. Farmed salmon tend to have more toxins in them than wild ones because their feed is composed of concentrations of other fish that have mercury in their tissues. It is best to limit intake of farmed fish.
http://www.usgs.gov/themes/factsheet/146-00/#toxic www.epa.gov/mercury/information1.htm
What are the standard guidelines to eating fish?
Although health benefits of the nutrients in fish are great, fish also contain environmental toxins. The EPA recommends the following guidelines (follow these same recommendations when feeding fish and shellfish to your young child, but serve smaller portions):
- Do not eat Shark, Swordfish, King Mackerel, or Tilefish because they contain high levels of mercury.
- Eat up to 12 ounces (2 average meals) a week of a variety of fish and shellfish that are lower in mercury. Five of the most commonly eaten fish that are lower in mercury are shrimp, canned light tuna, salmon, pollock, and catfish. Another commonly eaten fish, albacore ("white") tuna has more mercury than canned light tuna. So, when choosing your two meals of fish and shellfish, you may eat up to 6 ounces (one average meal) of albacore tuna per week.
- Check local advisories about the safety of fish caught by family and friends in your local lakes, rivers, and coastal areas. If no advice is available, eat up to 6 ounces (one average meal) per week of fish you catch from local waters, but don't consume any other fish during that week.
- Eat farmed salmon no more than once a month to limit exposure to PCBs, dioxins, and other cancer causing toxins they contain.
For more information concerning consumption of mercury in the diet, please visit:
www.epa.gov/waterscience/fishadvice/advice.html#notp www.cfsan.fda.gov/~frf/sea-mehg.html
What is the United States government doing to minimize mercury pollution?
In short, not quite enough. In 1990, the current Clean Air Act amendment required the EPA to study whether regulating hazardous air pollution from power plants was necessary to protect public health. Ten years later, in December 2000, EPA concluded that it is necessary to regulate hazardous power plant air pollutants, including mercury. Under the law, the agency is required to set emissions limits for these hazardous power plant air pollutants, and those limits must take into account the maximum amount of reduction that is technologically achievable. However, agency experts have been unable to analyze emissions. The Natural Resources Defense Council (NRDC) believes the EPA's new mercury proposal would violate the law under the 1990 Clean Air Act.
www.nrdc.org/media/pressreleases/031205.asp
If you wish to contact the EPA with concerns about mercury and/or other toxins in our environment, please visit the EPA website at: www.epa.gov.
For a more complete assessment of mercury in our environment please visit the sites listed above and the United Nations global report on mercury at: www.chem.unep.ch/mercury/Report/Summary%20of%20the%20report.htm
Where is lead found in the environment?
Homes:
- Paint: Many homes built before 1978 have lead-based paint. The federal government banned lead-based paint from housing in 1978. Some states stopped its use even earlier. Generally, the older the home, the more likely it contains lead paint. Lead can be found in homes in the city, country, or suburbs; in apartments, single-family homes, both private and public housing; and inside and outside of the house.
- Mini-blinds: In the U.S., health departments in numerous states have now linked children's lead poisoning to plastic mini-blinds imported from China, Taiwan, and Mexico. Most homes today have these mini-blinds and can be bought easily at most discount stores, and home improvement stores. The child comes in contact with the lead when he or she looks out the window, maybe touching the blinds. Afterwards, the child may eat something without washing their hands and still be contaminated.
- Plastic toys painted in China, Taiwan, and other developing nations: The federal government recently recalled 150 million vending machine toys - rings and necklaces that sell for fifty cents or a dollar apiece.
- In soil around a home. (Soil can pick up lead from exterior paint, or other sources such as past use of leaded gas in cars.)
- Household dust. (Dust can pick up lead from deteriorating lead-based paint or from soil tracked into a home.)
- Drinking water. Your home might have plumbing with lead or lead solder. Call your local health department or water supplier to find out about testing your water. You cannot see, smell, or taste lead, and boiling your water will not get rid of lead. If you think your plumbing might have lead in it: Use only cold water for drinking and cooking, and run water for 15 to 30 seconds before drinking it, especially if you have not used your water for a few hours.
- Food and liquids stored in lead crystal or lead-glazed pottery or porcelain.
- Old painted toys and furniture.
- Hobbies that use lead, such as making pottery or stained glass, or refinishing furniture.
- Folk remedies that contain lead, such as "greta" and "azarcon" used to treat an upset stomach.
The job:
-
If you work with lead, you could bring it home on your hands
or clothes. Shower and change clothes before coming home.
Launder your work clothes separately from the rest of your
family's clothes.
http://www.epa.gov/lead/leadinfo.htm#facts www.kidsindanger.org/04v1/publications/reports/2004_playingwithpoison.pdf
What are some health effects of human exposure to lead?
With constant exposure, lead accumulates gradually in the body. It is absorbed by the red blood cells and circulated through the body where it becomes concentrated in soft tissues, especially the liver and kidneys. Lead can cause lesions in the central nervous system and apparently can damage the cells making up the blood-brain barrier that protects the brain from many harmful chemicals.
Lead is even more dangerous to children than adults because babies and young children often put their hands and other objects in their mouths. These objects can have lead dust on them. Children's growing bodies absorb more lead, and their brains and nervous systems are more sensitive to the damaging effects of lead. If not detected early, children with high levels of lead in their bodies can suffer from damage to the brain and nervous system, behavioral and learning problems (such as hyperactivity), slowed growth, hearing problems, and headaches. Adults can suffer from difficulties during pregnancy and other reproductive problems (in both men and women), high blood pressure, digestive problems, nerve disorders, memory and concentration problems, and muscle and joint pain.
www.epa.gov/lead/leadinfo.htm#facts
How do I protect my family from lead poisoning?
If you suspect that your house has lead hazards, you can take some immediate steps to reduce your family's risk. If you rent, notify your landlord of peeling or chipping paint. Clean up paint chips immediately. Clean floors, window frames, windowsills, and other surfaces weekly. Use a mop, sponge, or paper towel with warm water and a general all-purpose cleaner or a cleaner made specifically for lead. Thoroughly rinse sponges and mop heads after cleaning dirty or dusty areas. Wash children's hands often, especially before they eat and before nap time and bedtime. Keep play areas clean. Wash bottles, pacifiers, toys, and stuffed animals regularly. Keep children from chewing windowsills, blinds, or other painted surfaces. Clean or remove shoes before entering your home to avoid tracking in lead from soil. Make sure children eat nutritious, low-fat meals high in iron, calcium, and vitamin C such as spinach and dairy products, as children with good diets absorb less lead.
In addition to day-to-day cleaning and good nutrition, you can temporarily reduce lead hazards by repairing damaged painted surfaces and planting grass to cover soil with high lead levels. These actions (called "interim controls") are not permanent solutions and will need ongoing attention. To permanently remove lead hazards, you must hire a certified lead "abatement" contractor. Abatement (or permanent hazard elimination) methods include removing, sealing, or enclosing lead-based paint with special materials. Just painting over the hazard with regular paint is not enough. Always hire a person with special training for correcting lead problems; someone who knows how to do this work safely and has the proper equipment to clean up thoroughly. Certified contractors will employ qualified workers and follow strict safety rules set by their state or the federal government. Contact the National Lead Information Center (NLIC) for help with locating certified contractors in your area and to see if financial assistance is available.
www.epa.gov/lead/leadinfo.htm#protect
What do I do if I’m planning to rent or buy a home built before 1978?
Familiarize yourself with the Residential Lead-Based Paint Disclosure Program. Landlords have to disclose known information on lead-based paint and lead-based paint hazards before leases take effect. Leases must include a disclosure form about lead-based paint. Sellers have to disclose known information on lead-based paint and lead-based paint hazards before selling a house. Sales contracts must include a disclosure form about lead-based paint. Buyers have up to 10 days to check for lead hazards.
www.epa.gov/lead/leadinfo.htm#protect
