[Methodology of toxicity evaluation to establish the drinking water quality standards]

Revision of Japanese "Drinking Water Quality Standards" in water supply was proposed in December, 1992. The strategy for settings of standard values was basically according to that of "WHO Drinking Water Quality Guideline". In this communication, the principal procedure for setting of WHO guideline values based on the data of animal toxicity studies is described, especially with regard to how to evaluate the toxicity data and use the uncertainty factors for extrapolation to humans.