What are nitrates and nitrites?
Nitrate and nitrite are two nitrogen compounds needed by plants and animals to live and grow. They occur naturally in soil, water, and air and are also made in the body.
In agriculture, nitrate is used as fertilizer for crops and lawns. Nitrate and nitrite are also used as food preservatives.
How can I be exposed to nitrates and nitrites?
People can be exposed to nitrates and nitrites by drinking contaminated water. Nitrate and nitrite move quickly through soil into surface water and groundwater. Common sources are fertilizers, septic tanks, livestock manure, and decaying plants.
Nitrate and nitrite occur in vegetables, especially celery, lettuce, and spinach. They can also be in fruits, cured meats, fish, dairy products, beers, and cereals.
How can nitrates and nitrites affect my health?
Most people are not exposed to levels of nitrates and nitrites that cause health effects.
Nitrates are not normally dangerous to health unless they are converted to nitrites. This can happen inside the body. Infants are more susceptible to the effects of nitrate exposure. The risk of harm increases if an infant is fed formula made with water that has high levels of nitrates and/or nitrites. This can interfere with the oxygen-carrying capacity of the child's blood and cause a health condition called methemoglobinemia. This condition can worsen rapidly over a period of days. Symptoms include shortness of breath and blueness of the skin.
There is limited evidence that long-term exposure to nitrate and nitrite can cause some cancers. Because the data are inconclusive, health standards focus on protecting infants.
What is the drinking water standard for nitrates and nitrites?
The U.S. Environmental Protection Agency (EPA) and Massachusetts Department of Environmental Protection (MassDEP) Maximum Contaminant Level (MCL) is 10 milligrams per liter (mg/L) for total nitrate and nitrite. For transient non-community systems, the MCL is 10 mg/L for nitrate and 1 mg/L for nitrite.
In Massachusetts, local Boards of Health and Health Departments have the authority to regulate private wells. They 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 nitrates and nitrites?
All public water systems are required to test for nitrate and nitrite 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 quarterly (every three months). Groundwater systems are required to test every year. MassDEP reviews the testing plan for each public water system. Plans may be adjusted depending on past sample results or other considerations.
Available data
Because nitrate is converted to nitrite in the body, MA EPHT focuses on tracking nitrate in drinking water. Use the Explore drinking water data link on this page to access following measures for nitrates 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
- Quarterly average concentration by number of Community Water Systems and people served
- 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 presented for public water systems only. The most current available data will be shown. Be sure to check the site periodically as new data are added.
Additional resources
Massachusetts
- 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 for nitrate and nitrite: Frequently asked health questions about nitrates and nitrites