Use of Risk to Resolve Conflicts in Accessing Hazards at Mixed-Waste Sites

Two main issues contribute to the assessment of health hazard from mixed waste: the scientific methods to assess these materials and the legislative and regulatory control of these materials. This paper is primarily concerned with the scientific method of assessing hazards from mixed waste (i.e., carcinogenic chemicals, noncarcinogenic chemicals, and radioactive material). This paper discusses SRS, a Site Ranking System, and its use of risk concepts to avoid introducing new inconsistencies when ranking mixed-waste sites. SRS ranks each site by scoring factors that influence the human health risk. The factors are (1) the potentially exposed population, (2) the average amount of exposure to the waste, and (3) the toxicity of the waste. The relative risk of a release is measured as the product of these three factors. The third factor, toxicity, is indexed with a single score, but because methods of measuring toxicity differ for carcinogenic chemicals, noncarcinogenic chemicals, and radionuclides, comparison can be difficult; hence, this paper also summarizes the logic and assumptions used to make toxicity comparisons in SRS. As may be expected, results from a ranking scheme based on risk are different from results generated by the original Hazard Ranking System (HRS), used by the Environmental Protection Agency. This paper briefly discusses these differences for five Superfund sites (no mixed waste). The legislative and regulatory control of these materials to protect human health is also discussed.