| Based on the issues identified in the Safe Drinking Water Program of the U.S. Environmental Protection Agency (EPA), an alternative risk assessment model for setting drinking water standards is proposed. The model is applied to a set of water systems to verify its utility compared to the current approach of the EPA. Considering the number of water systems that have violated the drinking water standard, it is questioned whether there may be water systems that did not violate the drinking water standard but still gave significant health risks under the current approach. This phenomenon of giving substantial health risk in a compliance concentration is observed from the case study and is termed a ‘false negative’. On the other hand, the ‘false positive’ of water system performance that violates the drinking water standard, even though the resulting health risk is negligible, is observed in the case study as well. Based on the observed issues in the Safe Drinking Water Program and the implications from the case study, the study concludes that it will be desirable to extend the EPA's 3-category approach for carcinogens to include noncancer effect and to consider combining consequences of multiple contaminants. |
