Are Nitrates in Water A Cancer Risk?

A peer reviewed study published by the Environmental Working Group proposes that nitrate pollution of U.S. drinking water may cause from 2300 to 12,594 cases of cancer per year.  Most of these cases are in the rural farmland area where agronomic inputs, septic systems and home lawns becomes the source of this contamination.  Currently, the EPA acceptable level is 10ppm, but the EWG wants to see a lower level, about 0.14 ppm.

These statistical studies make a lot of inferences based on diverse data, so it is important to recognize the limit of this.

Jeff Stoltzfus, Penn State's Farm Food Safety Educator, was kind enough to provide some facts.  First, the baseline level, or background level, found in undisturbed aquifers is 1ppm and as high as 3ppm.  Vegetables and meat also contribute significant amounts of nitrates to our diet.  Finally, there are many, many activities we engage in each day that represent a higher risk than this.

Environmental Research, online 11 June 2019, https://doi.org/10.1016/j.envres.2019.04.009

https://www.sciencedirect.com/science/article/pii/S001393511930218X?via%3Dihub
Exposure-based assessment and economic valuation of adverse birth outcomes and cancer risk due to nitrate in United States drinking water.
 Alexis Temkin a, Sydney Evans a, Tatiana Manidis b, Chris Campbell a, Olga V. Naidenko a
https://doi.org/10.1016/j.envres.2019.04.009

Highlights

• First of its kind national analysis assessing nitrate exposure from drinking water for the entire U.S. population.
• 2,300 to 12,594 nitrate-attributable cancer cases annually in the U.S., of which 54-82% are colorectal cancer (CRC) cases.
• Up to $1.5 and $6.5 billion in medical and indirect costs may be associated with annual nitrate-attributable cancer cases.
• Meta-analysis of eight studies assessing nitrate in drinking water and CRC supports a health benchmark of 0.14 mg/L

Abstract

Background
Nitrate ingestion from drinking water has been associated with an increased risk of adverse birth outcomes as well as elevated risk of colorectal cancer and several other cancers. Yet, to date, no studies have attempted to quantify the health and economic impacts due to nitrate in drinking water in the United States.

Methods
This study presents a first-of-its-kind comprehensive assessment of nitrate exposure from drinking water for the entire United States population. This exposure assessment serves as the basis for our analysis of the annual nitrate-attributable disease cases in the United States and the associated economic losses due to medical costs and lost productivity. Additionally, through a meta-analysis of studies on drinking water nitrate and colorectal cancer, we examine the exposure-response relationship for nitrate and cancer risk.

Results
On the basis of national nitrate occurrence data and relative risk ratios reported in the epidemiology literature, we calculated that annually, 2939 cases of very low birth weight, 1725 cases of very preterm birth, and 41 cases of neural tube defects could be related to nitrate exposure from drinking water. For cancer risk, combining nitrate-specific risk estimates for colorectal, ovarian, thyroid, kidney, and bladder cancers results in a range of 2300 to 12,594 annual nitrate-attributable cancer cases (mean: 6537 estimated cases). For medical expenditures alone, this burden of cancer corresponds to an annual economic cost of 250 million to 1.5 billion U.S. dollars, together with a potential 1.3 to 6.5 billion dollar impact due to lost productivity. With the meta-analysis of eight studies of drinking water nitrate and colorectal cancer, we observed a statistically significant positive association for nitrate exposure and colorectal cancer risk and calculated a one-in-one million cancer risk level of 0.14 mg/L nitrate in drinking water.

Conclusion
Health and economic analyses presented here suggest that lowering exposure to nitrate in drinking water could bring economic benefits by alleviating the impacts of nitrate-associated diseases.