Health risks from mixtures of radionuclides and chemicals in drinking water

The Food and Drug Administration (FDA) has pioneered a ''generally recognized as safe,'' or GRAS, concept. In this study, we propose to build on that infrastructure somewhat differently but in a way consistent with the general intent of the FDA. As three examples of potential GRAS-equivalent indexes, we explore: hypothetically pure utility drinking water containing fluoride (1 ppM) and chlorination residue products consumed at a personal ingestion rate of 2 L/d; consumption of one reference metal and 2 L/d and the 40-mrem annual natural terrestrial radiation background as described by the US National Academy of Sciences (NAS 1980). On the basis of conventional QRA models and the proposed relative method scaled to the described GRAS-equivalent indexes, we demonstrate techniques of relative comparisons to enhance absolute or QRA models and simultaneously to implement a ''reality check.'' Comparisons permit the decision maker to draw meaningful conclusions to better allocate resources. We demonstrate this evaluation for two hypothetical wells in a waste area. For purposes of illustration, two hypothetical water samples from a reference solid waste storage area (SWSA) were assumed. Concentrations were taken from representative measurements, but the example is hypothetical because only an abbreviated inventory of actual pollutants made up ofmore » chemicals and radionuclides was used. 28 refs., 8 tabs.« less