What is arsenic?
Arsenic is a naturally occurring element found in soil, rocks, water, air, and food. Arsenic is also a byproduct of some agricultural and industrial activities. In the past, arsenic was a common ingredient in some pesticides and herbicides. It could end up in soil from apple orchard spraying, coal ash disposal, and use of some pressure-treated wood. Arsenic can still be present in soil from these past activities.
Arsenic occurs in two different forms: organic and inorganic. The inorganic forms of arsenic are generally found in groundwater. These pose a greater health concern than the organic forms that are present in some foods (such as rice and seafood).
How can I be exposed to arsenic?
We normally take in small amounts of arsenic from air, food, and water. In some situations, exposure to arsenic may be higher.
Arsenic can get into water supplies through natural processes and human activities. It can enter groundwater as it leaches from soil and bedrock. In Massachusetts, arsenic naturally occurs in the bedrock in the central part of the state. This area is referred to as an “arsenic belt.” Arsenic can also enter surface water from runoff from agriculture or mining.
People near industrial or agricultural sources of arsenic may breathe higher levels of arsenic in dust.
Food, such as rice and seafood, can contain arsenic - but usually in the less dangerous, organic form.
How can arsenic affect my health?
Short-term exposure to drinking water with higher levels of inorganic arsenic (0.3 milligrams per liter [mg/L] or more) may lead to:
- Nausea, vomiting, and diarrhea
- Cardiovascular effects (e.g., abnormal heart rhythm, damage to blood vessels)
- Brain effects (i.e., encephalopathy)
- Decreased production of red and white blood cells
- Impaired nerve function (e.g., sensation of “pins and needles” in hands and feet)
Long-term ingestion of drinking water with low levels of inorganic arsenic (less than 0.3 mg/L) may lead to:
- Thickening and discoloration of skin
- Damage to the nervous system (e.g., weakness and numbing in the hands and feet)
- Increased risk of certain cancers, including bladder, lung, skin, kidney, liver, and prostate
What is the drinking water standard for arsenic?
The U.S. Environmental Protection Agency (EPA) and Massachusetts Department of Environmental Protection (MassDEP) Maximum Contaminant Level (MCL) for arsenic in public water supplies is 0.1 mg/L.
In Massachusetts, local Boards of Health and Health Departments have the authority to regulate private wells. This may include setting criteria for their location, construction, water quality, and quantity. More information for residents who use private wells is available from MassDEP.
What are the testing requirements for arsenic?
Arsenic has no smell, taste, or color when dissolved in water, even at high levels. Testing is the only way to know if arsenic is present in drinking water.
All public water systems are required to test for arsenic at each entry point to the distribution system. This is after water is treated and before it enters the pipes that bring water to customers. Surface water systems are required to test for arsenic every year. Groundwater systems are required to test for arsenic every three years. MassDEP reviews the testing plan for each public water system. Plans may be adjusted depending on past sample results or other considerations.
Available data
Use the Explore drinking water data link on this page to access the following measures for arsenic in drinking water:
- Annual maximum concentration by number of Community Water Systems and people served
- Annual average concentration by number of Community Water Systems and people served
- Annual average concentration by Community Water System
- Drinking water violations by Community Water System
MA EPHT presents data for the following geographies: city/town, county, EP region, or EOHHS region. Data are provided for public water systems only. The most current available data is shown. Be sure to check the site periodically as new data are added.
Related links
Additional resources
Massachusetts
- Arsenic and uranium bedrock well study: Information from a 2009 study by the U.S. Geological Survey (USGS) on the presence of arsenic and uranium in drinking water wells in Eastern Massachusetts. Includes maps of arsenic and uranium probability zones.
- MassDEP guide to water quality testing for private wells: Recommended water quality testing for private wells
National
- Agency for Toxic Substances and Disease Registry (ATSDR) ToxFAQs on arsenic: Frequently asked health questions about arsenic