Researchers found that one in five Americans served by more than 6,000 community water systems received drinking water that tested at concerning nitrate levels at least once. The current federal legal limit for nitrate is 10 mg/L, set in 1962, but studies have linked nitrate exposure at far lower levels to multiple cancers, preterm birth, low birth weight, and birth defects, according to researchers. The Environmental Working Group uses 3 mg/L as a modern benchmark for nitrate pollution.
55 mg/L last June, according to reports. 20 mg/L in groundwater serving more than 20,500 people, while in San Francisco nearly 80% of tests showed nitrate at or above 5 mg/L, experts said. Infants under six months old are especially vulnerable because their bodies cannot properly process nitrate, and pregnant women may also be at increased risk, according to researchers.
People who rely on private wells face additional danger because their water is not routinely monitored or regulated by federal agencies, experts say. Researchers say three major trends are making the nitrate problem worse, the first of which is climate change causing heavier rainfall.