National Drinking Water Database
National Drinking Water Database - Chemical Contaminants
Status: Regulated - EPA has established a maximum legal limit in tapwater for this contaminant.
Nitrite is a chemical that enters water from fertilizer runoff, leaching septic tanks, and erosion of natural deposits.
Nitrite (measured as Nitrogen)
Nitrite is a naturally occurring chemical. Sodium nitrite is often used to preserve food, especially cured meats. Nitrite is also formed in the gut by bacteria that convert nitrate to nitrite, which is mostly responsible for any toxic effects observed. Most human exposure comes from the diet, but drinking water is an important source of exposure in contaminated areas. Nitrate ends up in drinking water due to agricultural runoff from fertilizer use, erosion of natural deposits, or from animal and human waste via septic tanks and sewage systems. Rural water supplies of mid-western farming states, whose sources are often untreated groundwater, are most susceptible to high levels of nitrate. Drinking water is a more important source of exposure in bottle-fed infants (California Environmental Protection Agency 1997g).
Nitrite in water can be formed by microbial reduction of nitrate. Nitrite is produced in tap water distribution pipes by certain species of bacteria during stagnation of nitrate-containing and oxygen-poor drinking water in galvanized steel pipes, or if chloramination is used as a secondary disinfection (WHO 2004a; Zhang 2009).
One of the most well known signs of nitrate/nitrite poisoning is oxygen deprivation due to methemoglobinemia. In the blood, nitrite changes hemoglobin (which carries oxygen), to methemoglobin (which is unable to carry oxygen). This causes blood to carry less oxygen and can be fatal if too much methemoglobin is produced. Symptoms include rapid breathing, muscle tremors, lack of coordination, weakness, diarrhea, and frequent urination.
Infants are especially susceptible to methemoglobinemia, which can cause "blue baby syndrome." Pound for pound, infants drink more water than adults resulting in higher nitrate exposure. Infants also tend to have higher levels of bacteria in the gut that can convert nitrate to nitrite. In addition, hemoglobin is converted more easily to methemoglobin in infants. Finally, infants are less capable of metabolizing methemoglobin. Over 2,000 causes of "blue baby syndrome" have been reported from around the world since the mid-1950s, mostly from contaminated drinking water used to make infant formula (California Environmental Protection Agency 1997g). Several studies have reported an association between high maternal drinking water nitrate levels and risk of birth defects, including incomplete brain development (Arbuckle 1988, Croen 2001, Cedergren 2002).
Inside the body, nitrite can react with amines to form N-nitroso compounds, many of which are known animal carcinogens (California Environmental Protection Agency 1997g, National Toxicology Program (NTP) 2002a). Some, but not all, human cancer studies have found associations between high drinking water levels of nitrate and cancer, such as non-Hodgkin's lymphoma and cancers of the bladder and stomach (California Environmental Protection Agency 1997g, Ward 1996). Exposure to nitrate, nitrite and N-nitroso compounds have been associated with increased risk of type 1 diabetes in approximately half of the studies that have looked at this issue (Longnecker and Daniels 2001). Other possible health effects in people include low blood pressure (California Environmental Protection Agency 1997g) and altered immune function (Ustyugova 2002).
Nitrite Exposure by State
Water utilities in 40 states have reported detecting Nitrite in treated tap water since 2004, according to EWG's analysis of water quality data supplied by state water agencies.
|State||Water Suppliers with Nitrite contamination||Water suppliers reporting Nitrite above health-based limits|
The Most Polluted Communities
2,719 water utilities reported detecting Nitrite in tap water since 2004, according to EWG's analysis of water quality data supplied by state water agencies
Ranked by highest average Nitrite level
|Rank||System||Population Served||Positive test results of total reported tests||Average Level|
|859||1 of 1||2.78 ppm|
|2||Hoke Co Regional Water System|
|22,617||1 of 1||2.66 ppm|
|3||Macgregor Downs S/D|
|25||1 of 1||2.2 ppm|
|4||Eklutna Utilities Twin Peaks|
Eagle River, AK
|35||1 of 1||2.18 ppm|
|5||Churdan Water Supply|
|418||4 of 4||2.09 ppm|
(1.45 to 2.75 ppm)
|6||Pt. Mackenzie Correctional Farm|
|178||1 of 1||1.83 ppm|
|7||City of Hamilton|
|2,937||1 of 1||1.67 ppm|
|8||Multi County Wsc|
|2,235||1 of 1||1.63 ppm|
|9||Town of Owego - RT 38|
|200||1 of 1||1.6 ppm|
|200||1 of 1||1.5 ppm|
Health Based Limits for Nitrite
|Maximum Contaminant Limit (MCL)||The enforceable standard which defines the highest level of a contaminant that is allowed in drinking water. MCLs are set as close to health-based limits (Maximum Contaminant Level Goals, or MCLGs) as feasible using the best available analytical and treatment technologies and taking cost into consideration. Source: U.S. Environmental Protection Agency.||1 ppm|
|Maximum Contaminant Limit Goal (MCLG)||A non-enforceable health goal that is set at a level at which no known or anticipated adverse effect on the health of persons occurs and which allows an adequate margin of safety. Source: U.S. Environmental Protection Agency.||1 ppm|
|California Public Health Goals||Defined by the State of California Office of Environmental Health Hazard Assessment (OEHHA) as the level of contaminant that is allowed in drinking water. For acutely toxic substances, levels are set at which scientific evidence indicates that no known or anticipated adverse effects on health will occur, plus an adequate margin-of safety. PHGs for carcinogens or other substances which can cause chronic disease shall be based solely on health effects without regard to cost impacts and shall be set at levels which OEHHA has determined do not pose any significant risk to health.||1 ppm|
|Children's health-based limit for 1-day exposure||Concentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic health effects for up to one day of exposure. The One-Day health-based limit (or Health Advisory, HA) is typically set to protect a 10-kg child consuming 1 liter of water per day. Source: U.S. Environmental Protection Agency.||1 ppm|
|Children's health-based limit for 10-day exposure||Concentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic effects for up to ten days of exposure. The Ten-Day health-based limit (or Health Advisory, HA) is typically set to protect a 10-kg child consuming 1 liter of water per day. Source: U.S. Environmental Protection Agency.||1 ppm|
Testing Summary for Nitrite
|Are tests routinely required for Nitrite by federal law?||Yes|
|Water suppliers reporting tests for Nitrite (2004-2009):||23,738 of 47,576|
|Average testing rate for water supplier reporting tests (2004-2009):||0.6 per year|
Violation Summary for Nitrite
Data from the U.S. Environmental Protection Agency includes the following violations of federal standards for Nitrite since 2004
|Maximum Contaminant Level Exceedance Violations||36|