Nitrate contamination of drinking water: evaluation of genotoxic risk in human populations.

Nitrate contamination of drinking water implies a genotoxic risk to man due to the endogenous formation of carcinogenic N-nitroso compounds from nitrate-derived nitrite. Thus far, epidemiological studies have presented conflicting results on the relation of drinking water nitrate levels with gastric cancer incidence. This uncertainty becomes of relevance in view of the steadily increasing nitrate levels in regular drinking water supplies. In an attempt to apply genetic biomarker analysis to improve the basis for risk assessment with respect to drinking water nitrate contamination, this study evaluates peripheral lymphocyte chromosomal damage in human populations exposed to low, medium, and high drinking water nitrate levels, the latter being present in private water wells. It is shown that nitrate contamination of drinking water causes dose-dependent increases in nitrate body load as monitored by 24-hr urinary nitrate excretion in female volunteers, but this appears not to be associated with peripheral lymphocyte sister chromatid exchange frequencies.