New Study Suggests Nitrate in U.S. Drinking Water May Cause Thousands of Cancer Cases Per Year

The Environmental Protection Agency (EPA) defines nitrates as essential plant nutrients which can, in excess amounts, cause significant water quality problems. The nitrate contamination issues in the U.S., according to the new study, are largely caused by farm runoff containing fertilizer and manure. If the study’s estimate about new cancer cases is accurate, authors say the cost of treating all the people who develop these cancers could be up to $1.5 billion.

However, the statistics presented in this particular study are meant to warn us of cancer cases that develop in the future. The study focused on nitrate occurrence data in drinking water only from 2010 to 2017. Study authors note that “cancer is a disease with long latency, the findings presented in this study are most relevant for future cancer prevention efforts.” The meta-analyses show that exposure to nitrates in drinking water could account for 1 to 8% of total colorectal cancer cases annually in the U.S. — since colorectal cancer is relatively common in the United States (it’s the fourth most common cancer in the country) that translates to about 1,233 to 10,379 cases a year.

On a state-by-state basis, researchers found that four states — Delaware, Arizona, California, and Iowa — had population-weighted nitrate contamination levels that, at the high end of EWG’s estimates — could cause more than 10 cases of cancer per 100,000 people a year. These numbers may not seen large, but the size of a state like California’s population (39.6 million people, according to the 2018 Census) must be considered when thinking about risk. Five additional states — Pennsylvania, Maryland, Nebraska, New Jersey and Idaho — had average contamination levels that could cause more than five new cases of cancer per 100,000 people, according to a blog entry by study author and Toxicologist Alexis Tempkin, Ph.D.

Study authors called for the government to make changes to the current nitrate standard, claiming this research illustrates just how many Americans are at risk. The current EPA standard, which was set in 1962, is 10 parts per million (or 10 mg/L) when it comes to nitrate in drinking water. However, study authors point out that there have been epidemiological studies that link nitrate in drinking water with cancer and other serious health issues at levels that are about one tenth of that legal limit.

“Nitrate contamination of drinking water is a serious problem, and especially severe in the nation’s farm country,” said Olga Naidenko, Ph.D., senior science advisor at EWG and one of the study authors. “Now, for the first time, we can see the staggering consequences of this pollution.”

In the past few years, several studies have come out in Europe that report statistically significant increase in colorectal cancer risk associated with nitrate in drinking water at levels of just .7 to 2 mg/L. The highest risk was observed in men who consumed a lot of red meat. Another recent study conducted in Iowa, a region of the U.S. with a history of high levels of nitrate in drinking water, found that higher risk for colorectal cancer was observed among people who consumed water with nitrate levels of 5 mg/L — however, this study also linked the higher risk to those who consumed a lot of red meat. It’s also worth noting that not all epidemiological studies report an elevated colorectal cancer risk with nitrate exposure. Study authors did point out that a study in Iowa that looked at only females observed no association between drinking water nitrate and colorectal cancer risk (if risk factors such as meat intake and antioxidant levels were also considered).

Despite the new study, the EPA gave a statement to CBS News declaring that drinking water standards are tightly regulated for contaminants like nitrates and bacteria. “In EPA’s most recent statutorily mandated review of drinking water standards, published in 2017, the agency determined not to revise the existing nitrate/nitrite standards. EPA will continue to monitor research on nitrates and other drinking water contaminants and will determine the next steps as appropriate in future reviews of drinking water standards,” the agency said.

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