Heavy Metal Pollutants

According to an article published by Imperial College's Department of Epidemiology and Public Health, the largest risk to human health from heavy metals is derived from lead, mercury, and arsenic. Exposure to heavy metals continues despite the known dangers to the environment, animals and humans. In parts of the world, heavy metal exposure is actually increasing.

Lead

• This metal is a naturally occurring blue-gray metal found in the earth's crust in small amounts. Most lead comes from manufacturing, burning fossil fuels and mining. Lead is used to make batteries, ammunition, x-ray shields and metal solder and pipes. Lead-based paint, ceramics, caulk and pipe solder are less common as of 2010 because of health concerns. The metal damages the nervous system, reproductive system and kidneys.

  When lead enters the environment, its compounds are changed by sunlight, air and water. It has the capability of traveling long distances in the air before settling and sticks to soil particles when it falls onto earth. Lead may move into groundwater, depending on its chemical makeup and the soil type.

  Air, dust, food and water can be contaminated with lead. Children may be exposed by playing in contaminated soil or eating lead paint chips. Water pipes in older homes sometimes contain lead solder, which leaks into the water. Deteriorating lead paint can also lead to lead dust, which also may be present in older structures. Certain jobs and hobbies also increase exposure to lead, like making stained glass or using certain health care products.

Arsenic

• Arsenic is a natural metal found in soil and minerals. It's distributed widely in the earth's crust. When introduced into the environment, arsenic mixes with oxygen, chlorine and sulfur to make inorganic compounds. It mixes with carbon and hydrogen in plants and animals, creating organic compounds.

  Arsenic compounds are typically used to protect wood, in pesticides (organic compounds) and for other industrial uses. Arsenic can enter the air, water and land from wind-blown dust. It gets into groundwater from runoff. You cannot destroy arsenic in the environment, only change its form, though rain and snow will remove arsenic particles from the air. Since many arsenic compounds dissolve in water, most end up in soil. Fish and shellfish accumulate an organic arsenic compound that's not as harmful.

  People risk exposure to arsenic by ingesting contaminated food and water or breathing contaminated air, sawdust or burning smoke from arsenic-treated wood. Living in an area where high natural levels occur or working in a job where arsenic is used also increases risk.

  Breathing high levels of arsenic causes irritated lungs and throat. Ingesting high levels may result in death. Lower levels cause nausea, vomiting, arrhythmia (abnormal heart beat), blood vessel damage, decreased red and white blood cell production and a feeling of "pins and needles" in the hands and feet. Skin contact may cause irritation. Long-term arsenic exposure may also increase the risk of cancer and contribute to lower IQ scores in children.

Mercury

• This natural metal has several forms. Metallic mercury is a shiny, silver, odorless liquid. It turns into a colorless, odorless gas when heated. Metallic mercury enters the air from mining ore deposits, burning coal and waste and manufacturing plants. It can enter water and soil from natural deposits, waste disposal and volcanic activity.

  Exposure to mercury occurs by eating contaminated fish or shellfish or breathing vapors from mercury-containing spills, incinerators and other industry-related substances. Mercury is also released during dental work and medical treatments. Some jobs, like dental, health services and chemical industries, also increase risk of exposure.

  Mercury affects the nervous system, especially metallic mercury. High levels can damage the brain, kidneys and developing fetus in pregnant women. Short-term exposure to high levels can result in lung damage, nausea, vomiting, diarrhea, high blood pressure and heart rate, rashes and eye irritation.