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Arsenic and Your Health

RocksArsenic is a toxic chemical element that is found naturally in the Earth's crust in soil, rocks, and minerals. The levels of arsenic found in drinking water systems and private water supplies across the United States vary widely.

In addition to occurring naturally in the environment, arsenic is a by-product of some agricultural and industrial activities. It can enter drinking water through the ground or as runoff into surface water sources.

Some people could experience skin damage or problems with their circulatory system and may have an increased risk of getting cancer if over many years they drink water that contains arsenic in excess of the U.S. Environmental Protection Agency (EPA)'s standard.

In 2001 EPA reduced the regulatory drinking water standard known as the maximum contaminant level from 50 micrograms per liter (µg/L) to 10 µg/L. This decision was based on bladder and lung cancer risks. Lowering the MCL results in avoiding of 16 to 26 non-fatal bladder and lung cancers and 21 to 30 fatal bladder and lung cancers per year in the United States.

Exposure and Risk

The majority of health risks from arsenic exposure in the United States are long term. Although short-term exposures to high doses may cause adverse effects in people, such exposures do not occur from EPA-regulated public water supplies in the United States that comply with the arsenic MCL. A high dose is about a thousand times higher than the drinking water standard.

A young woman crunched over the side of her bed holding her stomach.Some people who drink water containing arsenic in excess of EPA's standard over many years could experience health effects, including:

  • thickening and discoloration of the skin;
  • stomach pain;
  • nausea;
  • vomiting;
  • diarrhea;
  • liver effects;
  • cardiovascular effects;
  • pulmonary effects;
  • immunological effects;
  • neurological effects, such as numbness and partial paralysis;
  • reproductive effects;
  • endocrine effects, such as diabetes; and
  • cancer
    • bladder,
    • lungs,
    • skin,
    • kidney,
    • nasal passages,
    • liver, and
    • prostate.


Water from a municipal or privately owned water company that meets the definition of a community water system is already being tested for arsenic.

However, people who have their own household water supply are responsible for maintaining and testing it. Well owners should contact their local health department to find out whether arsenic is a contaminant of concern in their area. Also, state drinking water agencies can provide names of laboratories certified to test drinking water.

Certified home treatment units may be found on the following Web sites:


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