Why is nitrate dangerous?

Most of the nitrate that ends up in public water systems comes from agricultural runoff that contains nitrogen fertilizer and manure. Although everyone may be exposed to nitrate, it poses the greatest risk to infants and pregnant women.

The potential harm of nitrate may begin during pregnancy, and at levels far lower than the legal standard. EWG estimates that every year, it may cause up to 2,939 cases of very low birth weight, up to 1,725 cases of very preterm birth and up to 41 cases of neural tube defects.

Infants fed formula made with water contaminated by nitrate above the federal legal standard run the risk methemoglobinemia, also known as "blue baby syndrome" — a rare but serious condition that blocks the blood's ability to carry oxygen. The EPA's current limit for nitrate in drinking water — 10 parts per million, or ppm — was set to prevent blue baby syndrome. Current research suggests that the standard, set in 1962, is long past due for an update.

Research shows that even a level of nitrate less than one-tenth of the current legal limit may cause harm to a developing fetus, but earlier this year, EPA suspended its planned reevaluation of the nitrate standard.

Although nitrate can be removed with at-home water filtration technologies, options are limited and can be expensive. It's less costly to keep nitrate out of drinking water in the first place, with policies and community-based efforts to protect source water, such as installing nitrate-removal treatment at water treatment plants.

"Millions of Americans are being involuntarily exposed to nitrate, and they are also the ones paying the heavy costs of treating contaminated tap water," said Alexis Temkin, Ph.D., a toxicologist and author of EWG's new nitrate study. "But the federal government is not doing enough to protect Americans from tap water contamination."

What can you do?

EWG has tools you can use to protect your family from nitrate contamination to your drinking water.

First, use EWG's Tap Water Database to find out whether you may be exposed to nitrate. If you have your own well, a state-certified facility can test for nitrate and other contaminants. Your local county cooperative extension program may provide well testing, maybe even at reduced or even no cost. It is especially important to get your well water tested if you live in farm country, where nitrate pollution is often worse.

If your water contains nitrate levels close to the EPA limit of 10 ppm, switch immediately to a different source of drinking water and install a water filtration system designed to remove nitrate. Even if your nitrate level is lower, you may want to install a water filter. Just be aware that carbon filters won't suffice to reduce nitrate. The EPA recommends reverse osmosis or ion exchange systems. Consult EWG's Water Filter Guide for filters that can protect against ntirate and other contaminants.

If you have a formula-fed baby, instead of using unfiltered tap water to mix formula, follow EWG guidelines to find a water filter system that will remove nitrate. Or use water that's been filtered by distillation or reverse osmosis, as indicated on the label.