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Drinking Water Quality - Arsenic

Arsenic is a toxic chemical that occurs naturally in the Earth's crust in soil, rocks, and minerals. Arsenic is also a byproduct of some agricultural and industrial activities. It is used with other chemicals to preserve wood as a pesticide for certain agricultural crops. Arsenic can enter the drinking water supply from natural sources in the Earth. It can also enter drinking water through discharge from industries where it is manufactured or used. Once it enters the environment, arsenic remains for a long time. There is wide variation in the levels of arsenic found in drinking water systems and private water supplies across the country.

Some people who drink water containing arsenic in excess of the U.S. Environmental Protection Agency's (U.S. EPA) Maximum Contaminant Level (MCL) over many years could experience skin damage or problems with their circulatory system, and may have an increased risk of getting cancer.

The MCL for arsenic is 10ug/L.

Did You Know?
Naturally high concentrations of arsenic in the Earth’s crust occur in parts of the U.S. including areas of central Massachusetts.

Specific health effects of arsenic exposure may include:

  • Thickening and discoloration of the skin, stomach pain, nausea, vomiting, diarrhea, and liver effects
  • Cardiovascular, pulmonary, immunological, neurological (e.g., numbness and partial paralysis), and reproductive and endocrine (e.g., diabetes) effects
  • Cancer of the bladder, lung, skin, kidney, nasal passages, liver, and prostate

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

Data Considerations

When reviewing and interpreting drinking water arsenic data, it is important to take into consideration the following:

  • The data presented are for public water systems only. Residents may have exposure to arsenic from private well water.
  • Exposure to arsenic in drinking water depends upon the concentration of arsenic in the drinking water and the amount of water consumed by the individual. Water consumption varies by such factors as climate and level of physical activity.
  • Many factors can affect whether exposure can lead to a health problem, including level of contamination, amount of water consumed, and the length of time water was contaminated. Some populations may be more susceptible to health problems following exposure, such as pregnant woman, children, and immune suppressed individuals.
  • This website provides a summary of drinking water violations by community. Consumer Confidence Reports on public drinking water quality are required to be provided annually to consumers. Your Community Water System should be contacted for this report, which will provide more detailed information on any specific water system violations.
  • Community Water Systems (CWSs) can serve areas substantially beyond the boundaries of the principal city/town. served
  • Multiple CWSs can serve the same city/town and multiple cities/towns can be served by a single.
  • For a list of all Massachusetts Community Water Systems and communities serverd, with attributes, click here (pdf).

For additional information, please read the FAQ.

Available Data on Water Quality Measures for Arsenic

Click the Explore Maps & Tables link button on this page to access the following measures for arsenic in your community. The most current available data will be shown. Be sure to check the site periodically as new data are added each year.

To protect privacy, no information is shown that could identify an individual home or family.

  • Maximum arsenic concentration by number of Community Water Systems and year of testing
  • Mean arsenic concentration by number of Community Water Systems and year of testing
  • Maximum arsenic concentration by number of people served by the Community Water Systems and year of testing
  • Mean arsenic concentration by number of people served by the Community Water Systems and year of testing
  • Mean arsenic concentration by individual Community Water System or county and year of testing
  • Drinking water violations by Community Water System or community and year of violation
More About the Data
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