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Review
. 2018 Jul 23;15(7):1557.
doi: 10.3390/ijerph15071557.

Drinking Water Nitrate and Human Health: An Updated Review

Mary H Ward  1 , Rena R Jones  2 , Jean D Brender  3 , Theo M de Kok  4 , Peter J Weyer  5 , Bernard T Nolan  6 , Cristina M Villanueva  7   8   9   10 , Simone G van Breda  11
Affiliations
Review

Drinking Water Nitrate and Human Health: An Updated Review

Mary H Ward et al. Int J Environ Res Public Health. .

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.

Keywords: N-nitroso compounds; adverse reproductive outcomes; cancer; drinking water; endogenous nitrosation; methemoglobinemia; nitrate; thyroid disease.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Boxplots of nitrate concentrations in shallow groundwater beneath agricultural and urban land uses, and at depths of private and public drinking water supplies beneath mixed land use. The number of sampled wells were 1573 (agricultural land), 1054 (urban), and 3417 (mixed). The agricultural and urban wells were sampled to assess land use effects, whereas the mixed category wells were sampled at depths of private and public supplies. Median depths of wells in the agricultural, urban, and mixed categories were 34, 32, and 200 feet, respectively. The height of the upper bar is 1.5 times the length of the box, and the lower bound was truncated at the nitrate detection limit of 0.05 mg/L NO3-N.
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