Workgroup Report: Drinking-Water Nitrate and Health—Recent Findings and Research Needs

Abstract

Human alteration of the nitrogen cycle has resulted in steadily accumulating nitrate in our water resources. The U.S. maximum contaminant level and World Health Organization guidelines for nitrate in drinking water were promulgated to protect infants from developing methemoglobinemia, an acute condition. Some scientists have recently suggested that the regulatory limit for nitrate is overly conservative; however, they have not thoroughly considered chronic health outcomes. In August 2004, a symposium on drinking-water nitrate and health was held at the International Society for Environmental Epidemiology meeting to evaluate nitrate exposures and associated health effects in relation to the current regulatory limit. The contribution of drinking-water nitrate toward endogenous formation of N-nitroso compounds was evaluated with a focus toward identifying subpopulations with increased rates of nitrosation. Adverse health effects may be the result of a complex interaction of the amount of nitrate ingested, the concomitant ingestion of nitrosation cofactors and precursors, and specific medical conditions that increase nitrosation. Workshop participants concluded that more experimental studies are needed and that a particularly fruitful approach may be to conduct epidemiologic studies among susceptible subgroups with increased endogenous nitrosation. The few epidemiologic studies that have evaluated intake of nitrosation precursors and/or nitrosation inhibitors have observed elevated risks for colon cancer and neural tube defects associated with drinking-water nitrate concentrations below the regulatory limit. The role of drinking-water nitrate exposure as a risk factor for specific cancers, reproductive outcomes, and other chronic health effects must be studied more thoroughly before changes to the regulatory level for nitrate in drinking water can be considered.

An evaluation of semi-quantitative test strips for the measurement of nitrate in drinking water in epidemiologic studies

“…Estimates of dietary nitrate and nitrite intake may also be useful. And, finally, for studies in which nitroso compound exposure is of particular interest, collection of a variety of other measures, such as measures of endogenous exposure to these compounds in saliva, urine or feces; biomarkers of genotoxicity; CYP2E1 genotype; and dietary intake of nitrosatable amines and amides, and vitamin C and other nitrosation inhibitors may be useful or necessary (Ward et al, 2005).…”

Effective Removal of Nitrates Ions from Aqueous Solution Using New Clay as Potential Low-Cost Adsorbent

“…Thus, the problem occurs very quickly and often the cattle are observed to be normal one day and dead the next day [8]. Ward et al [9] reviewed the epidemiologic evidence for the linkages between drinking water 3 …”

Pharmacology and therapeutic role of inorganic nitrite and nitrate in vasodilatation

“…Most cases of methemoglobinemia were reported in the 1940s where methemoglobinemia or "baby blue syndrome" was seen in infants fed formula with nitrate contaminated well-water (Powlson et al, 2008). It was later suggested that methemoglobinemia was not caused by nitrate but by fecal bacteria contamination in the well-water or bacterial nitrate reduction in vivo that may have caused the intestinal infection, and this may have been responsible for the nitrate-induced methemoglobinemia in the infants (Hanukoglu & Danon, 1996;Ward et al, 2005). Of interest, nitrate was used in very high doses (often for weeks) at the beginning of the last century as a diuretic (Butler & Feelisch, 2008).…”