Exposure-based assessment of potential health and economic impacts due to nitrate pollution of drinking water in the United States

Abstract

OPS 33: Health impact of interventions 2, Room 411, Floor 4, August 28, 2019, 10:30 AM - 12:00 PM Background: Nitrate ingestion from drinking water has been associated with an increased risk of several cancers as well as adverse birth outcomes such as neural tube defects and low birth weight. Within this overall body of research, colorectal cancer has the largest number of high-quality studies which report increased risk at the lowest exposure levels. 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 U.S. population, which serves as the basis for our analysis of the annual nitrate-attributable cancer cases and adverse reproductive outcomes in the U.S. 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: Combining nitrate-specific cancer risk estimates for colorectal, ovarian, thyroid, and bladder cancers results in an average of 5910 estimated annual nitrate-attributable cancer cases (1884 to 11,718 cancer cases) in the U.S. of which 66-85% are colorectal cancer cases. For medical costs alone, this results in an overall loss of 200 million to 1.4 billion dollars, and a potential 1 to 6 billion dollar loss from 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 cancer slope factor for nitrate in drinking water at 0.04 per mg/L. Conclusion: Health and economic analyses presented here suggest lowering exposure to nitrate in drinking water can help address colorectal cancer risk in the U.S. population and may alleviate the impacts of nitrate-associated diseases.