At Conference of Top Cancer Researchers, EWG Presents New Analysis Showing Nitrate-Polluted Tap Water Could Cause 12,500 Cancer Cases a Year

U.S. Drinking Water Standard for Nitrate Untouched Since 1962
(202) 667-6982
For Immediate Release: 
Monday, June 24, 2019

WASHINGTON – Drinking water contaminated with nitrate could be responsible for more than 12,500 cases of cancer each year, according to a peer-reviewed study by Environmental Working Group presented today at a conference of leading cancer and environmental health experts.

EWG toxicologist Alexis Temkin, Ph.D., discussed the research findings during a meeting sponsored by the American Association for Cancer Research, entitled Environmental Carcinogenesis: Potential Pathway to Cancer Prevention.

The study, recently published in the journal Environmental Research, is the first in the U.S. to estimate the number of cancer cases from nitrate pollution in municipal drinking water systems. Nitrate contamination in drinking water often comes from agricultural runoff of fertilizer and manure from farm fields and animal factory farms into rivers, lakes and streams. EWG estimates the healthcare costs of treating those cases may be close to $1.5 billion a year, Dr. Temkin said in her remarks.

EWG’s research shows Arizona, California, Iowa and Delaware have the highest frequency of estimated cancer cases from nitrate-contaminated tap water, with greater than 10 cases per 100,000 people.

The current federal drinking water standard of 10 parts per million, or ppm, was set in 1962 during the Kennedy administration and has not been updated since. Earlier this year, the Trump EPA abandoned plans to review the health effects associated with nitrate, claiming it was a “low priority.”

Over the past decade, a number of well-regarded epidemiological studies, including research conducted by National Cancer Institute, have connected nitrate in drinking water with increased risk of colon, kidney, ovarian, thyroid and bladder cancers. Four-fifths of the estimated cancer cases reported by the EWG study were occurrences of colorectal cancer.

Nitrate contamination of drinking water is also linked with neonatal health issues. EWG estimated that nitrate pollution may be responsible for as many as 2,939 cases of very low birth weight; 1,725 cases of very preterm birth; and 41 cases of neural tube defects.

EWG scientists estimate the level at which no adverse health effects would occur from nitrate in drinking water to be 0.14 milligrams per liter – equivalent to parts per million. That level, 70 times lower than the EPA’s legal limit, represents a one-in-one-million risk of cancer.

“Our research discovered that in many communities, nitrate found in drinking water could pose real health harms,” said Dr. Temkin. “If not addressed, this problem will likely continue to get worse.”

There are federal farm programs that pay farmers to adopt conservation practices to prevent nitrate pollution from running off fields into drinking water sources. EWG’s Conservation Database provides the first-ever detailed look at what practices farmers are being paid to adopt in every county nationwide. However, the data reveal a stunning underinvestment in the practices needed to protect drinking water in the places where it is most threatened from nitrate contamination.


The Environmental Working Group is a nonprofit, non-partisan organization that empowers people to live healthier lives in a healthier environment. Through research, advocacy and unique education tools, EWG drives consumer choice and civic action.