Drinking Water Nitrate and Human Health: An Updated Review

Abstract

Nitrate levels in our water resources have increased in many areas of the world largely due to applications of inorganic fertilizer and animal manure in agricultural areas. The regulatory limit for nitrate in public drinking water supplies was set to protect against infant methemoglobinemia, but other health effects were not considered. Risk of specific cancers and birth defects may be increased when nitrate is ingested under conditions that increase formation of N-nitroso compounds. We previously reviewed epidemiologic studies before 2005 of nitrate intake from drinking water and cancer, adverse reproductive outcomes and other health effects. Since that review, more than 30 epidemiologic studies have evaluated drinking water nitrate and these outcomes. The most common endpoints studied were colorectal cancer, bladder, and breast cancer (three studies each), and thyroid disease (four studies). Considering all studies, the strongest evidence for a relationship between drinking water nitrate ingestion and adverse health outcomes (besides methemoglobinemia) is for colorectal cancer, thyroid disease, and neural tube defects. Many studies observed increased risk with ingestion of water nitrate levels that were below regulatory limits. Future studies of these and other health outcomes should include improved exposure assessment and accurate characterization of individual factors that affect endogenous nitrosation.

Nitrate acts at the Arabidopsis thaliana shoot apical meristem to regulate flowering time

“…Many natural water basins and aquifers around the world are currently steering towards severe nitrate pollution through long and continued application of organic and synthetic fertilizers. The maximum contaminant level for public water supply of 50 mg nitrate l −1 determined by the World Health Organization (or 10 mg l −1 nitrate‐N, stipulated by the US Environmental Protection Agency) is being well exceeded (Ward et al ., ). Reducing the application of fertilizers is a general aim of modern agriculture.…”

A Review of Potential Public Health Impacts Associated With the Global Dairy Sector

“…Specifically, elevated nitrate levels in water lead to the formation of potentially carcinogenic N-nitrosamines (van Maanen et al, 1996). In some studies, the long-term consumption of nitrate in drinking water has been positively associated with a higher risk for non-Hodgkin's lymphoma, stomach, colorectal, bladder, breast, and ovarian cancers, and thyroid disease (Espejo-Herrera et al, 2016;Fachiroh et al, 2017;Gulis et al, 2002;Inoue-Choi et al, 2013;Jones et al, 2016;Schullehner et al, 2018;Ward et al, 2018;Weyer et al, 2001), although findings over time have not been consistent. Phosphorus is not directly toxic to human beings, but it is often the limiting nutrient in aquatic ecosystems (FAO et al, 2006) and changes in concentration can severely alter ecosystem functions.…”

Limnology and Oceanography Bulletin Volume 28 Number 4 November 2019 117–152

“…The consequences of water quality degradation include higher sewage treatment costs when tertiary treatment is called for to remove nitrate; high nitrate levels in water wells do not receive such treatment. Nitrate in drinking water is implicated in birth defects (Brender et al 2013) and cancer (Ward et al 2018).…”