Nitrate

DescriptionNitrate is commonly found in drinking water sources especially in agricultural areas where nitrogen fertilizer is used, and where unregulated shallow private wells are more at the risk of contamination. The World Health Organization (WHO) guideline of 50 ppm and the US maximum contaminant level (MCL) of 45 ppm for nitrate in drinking water have been established for protecting infants from methemoglobinemia, commonly known as blue baby syndrome. The health protective value continues to be a subject of public health interest for many years, with varying opinion on whether it is too high or too low. Evaluation of nitrate will need to include consideration of nitrite because both are closely related in the nitrogen cycle in the environment and the body, and nitrite plays a major role in inducing toxicity after its formation from nitrate. More recently, reports of nitrate in drinking water, especially at levels higher than 50 ppm, have been associated with other health effects other than methemoglobinemia. This toxicological review provides an update on the health effects of nitrate with a focus on methemoglobinemia, reproductive and developmental effects, potential carcinogenicity, and especially endocrine/thyroid effects.