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, such as mining and smelting (separating metal from rock). In the past, arsenic was a common ingredient in some pesticides and herbicides. Arsenic can still be present in soil from past activities, including apple orchard spraying, coal ash disposal, and use of some pressure treated wood.
Arsenic occurs in two different forms: organic and inorganic. The inorganic forms of arsenic are generally found in groundwater and 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, several communities in the central part of the state are within an “arsenic belt” where arsenic naturally occurs in bedrock.
Arsenic can also enter surface water from runoff from agriculture or mining. People near current or former industrial or agricultural sources of arsenic may breathe in higher levels of arsenic in dust.
Foods, 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, diarrhea, cardiovascular effects, and brain effects (i.e., encephalopathy), as well as decreased production of red and white blood cells and impaired nerve function.
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 the skin and damage to the nervous system (such as weakness and numbing in the hands and feet). Several studies have also shown that long-term exposure to inorganic arsenic can increase the 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 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 and may establish criteria for their location, construction, water quality, and quantity. Additional information for residents who use private wells is available from the Massachusetts Department of Environmental Protection (MassDEP).
What are the testing requirements for arsenic?
Arsenic has no smell, taste, or color when dissolved in water even at high levels, so 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 the entry point to the distribution system (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 and ground water systems are required to test for arsenic every three years. The Massachusetts Department of Environmental Protection (MassDEP) reviews the testing plan for each public water system and adjusts it according to past sample results and other considerations.