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Arsenic in Drinking Water - Information for Consumers

Questions and Answers About Arsenic

What is arsenic and where does it come from?

  • Arsenic is an element that occurs naturally in air, water, soil, rocks and minerals, food and living organisms in low concentrations.
  • It has no odor or taste.
  • Other sources of arsenic are from human activities, which exceeds natural sources by about three-fold. These include urban runoff, pesticides, fossil fuel combustion, treated lumber, smelting and mining wastes. It is also used in paints, dyes, and semiconductors.

What are the health concerns from arsenic exposure?

  • Human exposure to arsenic can cause both short-term (acute) and long-term (chronic) health effects.
  • The minimum lethal dose for acute (short term) arsenic poisoning is in the range of 50,000 to 300,000 parts per billion (ppb).
  • Long-term arsenic ingestion from drinking water is strongly associated with increased risk of skin cancer, and there is substantial evidence that it increases the risk for cancers of the bladder, lung, kidney, liver, colon, and prostate.
  • Non-cancer effects can include thickening and discoloration of the skin, stomach pain, nausea, vomiting, diarrhea, numbness in hands and feet, partial paralysis, and blindness.

What is the public drinking water standard?

  • Arsenic is regulated in public drinking water systems by the Environmental Protection Agency (EPA) and a maximum allowable limit-known as a maximum contaminant level (MCL)-has been established for it to protect against long-term exposure.
  • For many years, the MCL for total arsenic was 50 ppb. During the 1990s, however, new studies, advances in the technologies for detecting minute concentrations of contaminiants, and affordable treatments allowed regulators to lower the MCL and provide improved public health protection from chronic health effects.
  • A new standard of 10 ppb became effective on January 23, 2006.

How do I know if arsenic is in my public water supply?

  • If the arsenic MCL is exceeded, the public water system must issue a public notice to customers, in writing, within 30 days of the violation.
  • Customers would be notified immediately through broadcast media in the very unlikely event contamination levels were high enough to cause acute health effects.

What if I have my own well and I live near a public system that found high arsenic levels?

  • If you live in an area where a public water system has exceeded the arsenic MCL, you should consider having your private well tested. A listing of laboratories can be found below.
  • Even though private wells are not regulated by the Department, if the level in your private well exceeds the public drinking water standard of 10 ppb, you are urged to consider taking steps to reduce your long-term exposure to those levels of arsenic. Long-term measures usually involve treatment devices, such as those found at the link to NSF below, and should be used for any water that will be consumed by you and your family members (drinking, making beverages, preparing food, etc.). Bathing & hand washing, washing laundry, and flushing toilets are examples of water uses that do not require treatment.
  • You cannot remove arsenic by boiling the water. In fact, you will increase the concentration of arsenic in the water that remains after boiling.
  • If you still have questions, you can use the "Contact DEP" email address:

For More Information on Arsenic

  • DEP Laboratory Accreditation Program
  • Arsenic in Drinking Water -- U.S. Environmental Protection Agency
  • Arsenic from Other Routes of Exposure -- Agency for Toxic Substance and Disease Registry
  • Arsenic Quick Reference Guide (for public water suppliers) (PDF)

For a list of certified home products for arsenic removal: