Drinking water standards and risk assessment

The role and use of risk assessment methods in the establishment of drinking water standards are described with emphasis on recent applications. The process essentially includes an attempt to quantify human exposure from all routes including drinking water, animal toxicology, and human epidemiology, when available, to arrive at drinking water concentrations at which exposure would result in "no known or anticipated adverse effects on health, with a margin of safety." The process itself is straightforward; however, the application to decision making for substances that are considered to be potentially nonthreshold acting in their toxicity (e.g., carcinogenic) requires many policy choices beyond the scientific data and is subject to considerable controversy.