EWG: Over 60M Americans Exposed To Elevated Levels Of Contaminant Nitrate In Tap Water

Nitrate, linked to cancer and birth defects, regulated by a woefully outdated EPA standard

Minneapolis – One in five Americans, or more than 60 million people, rely on drinking water systems with elevated levels of nitrate, a contaminant increasingly linked to cancer, birth defects and other serious health harms, a new Environmental Working Group analysis finds.

“These findings underscore that millions of Americans are exposed to a dangerous contaminant that federal regulations fail to adequately control,” said Anne Schechinger, EWG’s senior director for agriculture and climate research and lead author of the analysis. 

Drawing on federal drinking water data from 2021 through 2023, the EWG analysis shows that 6,114 community water systems across the country detected nitrate at levels at or above 3 milligrams per liter, or mg/L, in at least one test.

This level is below the current federal legal limit set by the Environmental Protection Agency of 10 mg/L, based on a 1962 U.S. Public Health Service recommendation. But a growing body of scientific evidence indicates that long-term exposure to nitrate even at much lower concentrations can increase the risk of colorectal cancer, thyroid disease, and adverse birth outcomes, including low birth weight and neural tube birth defects like spina bifida. 

EWG’s recommended health-based nitrate benchmark that would reduce colorectal cancer risks to one-in-one million is 0.14 mg/L, far lower than the EPA’s limit.

“The EPA’s current nitrate standard is decades old and does not reflect modern science on the health risks of nitrate pollution,” Schechinger said.

Key findings of EWG's analysis

• 62.1 million people were served by community water systems that tested for nitrate at or above 3 mg/L at least once.
• 38 million people received water at or above 5 mg/L, a level health research increasingly links nitrates to cancer and reproductive harms.
• More than 3 million people received water at or above the woefully outdated federal legal limit of 10 mg/L — a threshold set based on science from over 60 years ago solely to prevent blue baby syndrome, a condition that reduces the blood’s ability to carry oxygen in infants.

Widespread and preventable threat

Nitrate contamination is one of the most pervasive forms of U.S. drinking water pollution, particularly in agricultural states. 

The primary contamination sources are fertilizer runoff from crop farming and manure from livestock operations. Once in groundwater and surface water, nitrate is difficult and costly to remove, leaving many communities — especially rural ones — vulnerable to chronic exposure.

EWG’s analysis underscores the scale of the problem. Elevated nitrate levels were found in water systems serving communities in nearly every state, affecting both small towns and major metropolitan areas, including Las Vegas, Los Angeles, Philadelphia and Phoenix.

Because nitrate is colorless, odorless and tasteless, people often have no indication that their water is contaminated.

Infants and pregnant people are especially at risk. Nitrate exposure has long been associated with blue baby syndrome and other developmental harms. This raises concerns that current nitrate tap water limits fall far short of what’s needed to safeguard public health.

EPA tap water standards lag behind science

Public health experts and scientists are increasingly calling for stronger protections than the federal legal limit in drinking water, known as a maximum contaminant level, or MCL. 

Studies suggest that nitrate levels well below the current legal limit may still pose significant risks over time, particularly for vulnerable populations.

“The science on the threats of nitrate exposure has advanced, but our public health protective standards have not,” said Schechinger. “We now know that even low-level exposure can have serious health consequences, yet federal policy continues to rely on an outdated threshold that fails to protect millions of people.”

Communities bear the financial burden

Consumers can enter their ZIP code in EWG’s Tap Water Database to check for nitrates and other contaminants in their public drinking water. The database also offers guidance on water filters that can reduce nitrates and other pollutants in your tap water.

For many communities, addressing nitrate contamination is not just a public health issue but a financial one.