Waste classification system INDEX

Risk Index for Mixtures of Hazardous Substances. For the purpose of developing a comprehensive and risk-based hazardous waste classification system, a simple method of calculating the risk posed by mixtures of radionuclides and hazardous chemicals is needed. The method should account for the linear, nonthreshold dose-response relationships for radionuclides and chemical carcinogens (stochastic effects) and the threshold dose-response relationships for noncarcinogenic hazardous chemicals (deterministic effects). 

A risk index for waste classification to be used in conjunction with the framework is then developed, the combination of these constituting the recommended risk-based waste classification system and... 

Limits on amounts of hazardous substances in each waste class would be calculated based on values of the so-called risk index for each hazardous substance in the waste and the composite risk index for mixtures of hazardous substances. For the purpose of describing the recommended framework for a risk-based hazardous waste classification system, the risk index is generally defined as ... 

The risk index in Equation 6.2 is expressed in terms of risk (i.e., the probability that an adverse response will occur during an individual s lifetime). This definition is consistent with the fundamental objective of developing a risk-based hazardous waste classification system. However, the use of health risk per se in calculating the risk index presents some difficulties because risk is not proportional to dose for substances that cause deterministic effects. For this type of substance, the risk is presumed to be zero at any dose below a nominal threshold. Since the allowable dose should always be less than the threshold in order to prevent the occurrence of adverse responses, expressing the risk index in terms of risk would result in an indeterminate value and, more importantly, a lack of distinction between doses near the nominal thresholds and lower doses of much less concern. For any hazardous substance, including carcinogens for which risk is assumed to be proportional to dose without threshold, it is generally useful to express the risk index as the ratio of a calculated dose [e.g., sieverts, mg (kg d)-1] to an allowable dose that corresponds to an allowable risk ... 

The risk index defined in Equation 6.1 (see Section 6.2.1) is intended to provide a measure of the potential risk that arises from disposal of any waste that contains hazardous substances. In Section 6.3, the general definition of the risk index is elaborated and recommendations on suitable approaches to calculating the risk index for individual hazardous substances are presented. For purposes of developing a comprehensive and risk-based waste classification system, a simple method of calculating the risk from disposal of mixtures of hazardous substances is needed. The method must take into account that the allowable concentrations of particular hazardous substances in waste of a given class generally will be lower when multiple substances are present than when only a single substance is present. Such a method is presented and discussed in this Section. 

Establishing a Waste Classification System Based on the Framework and Risk Index... 

Process of Implementing the Waste Classification System. Taken together, the framework for waste classification discussed in Section 6.2 and the risk index developed in Section 6.3 and this Section constitute the foundations of a comprehensive and risk-based hazardous waste classification system. Such a waste classification system could be established by regulatory authorities using the following general process ... 

An important issue in developing a risk-based hazardous waste classification system is the degree of conservatism in protecting public health that should be embodied in the foundations and framework of the system and its implementation. The specific issues are, first, the extent to which calculations of risk in the numerator of the risk index should deliberately overestimate expected risks that arise from disposal of hazardous waste and, second, the extent to which the... 

In many respects, the foundations and framework of the proposed risk-based hazardous waste classification system and the recommended approaches to implementation are intended to be neutral in regard to the degree of conservatism in protecting public health. With respect to calculations of risk or dose in the numerator of the risk index, important examples include (1) the recommendation that best estimates (MLEs) of probability coefficients for stochastic responses should be used for all substances that cause stochastic responses in classifying waste, rather than upper bounds (UCLs) as normally used in risk assessments for chemicals that induce stochastic effects, and (2) the recommended approach to estimating threshold doses of substances that induce deterministic effects in humans based on lower confidence limits of benchmark doses obtained from studies in humans or animals. Similarly, NCRP believes that the allowable (negligible or acceptable) risks or doses in the denominator of the risk index should be consistent with values used in health protection of the public in other routine exposure situations. NCRP does not believe that the allowable risks or doses assumed for purposes of waste classification should include margins of safety that are not applied in other situations. 

Expressing the decision rule for waste classification in terms of a risk index less than unity conforms to the approach used by NRC in its classification system for near-surface disposal of radioactive waste in 10 CFR Part 61 (NRC, 1982a). 

When sourcing/developing a chemical inventory management system, you should look for a program that offers Information indexed directly from the MSDS Interpretive storage, transportation and/or waste classifications... 

Classification of a given waste is based on an evaluation of the risk index specified in Equations 6.4, 6.5 and 6.6 for assumed types of disposal systems. If the risk index is less than unity, the waste is acceptable for inclusion in the associated waste class otherwise, the waste generally requires a more protective disposal system and would be placed in a class for more hazardous wastes. The appropriate classification depends on the level of protection required which, in turn, depends on the characteristics of the waste relative to the capabilities of assumed disposal technologies. This concept is a fundamental part of the risk index. General assumptions about... 

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