Example Calculations of the Risk Index

This Section provides example calculations of the composite risk index for a simple, hypothetical waste that contains a mixture of substances that cause stochastic or deterministic effects. Application of the risk index in classifying real wastes is considered in Section 7.1. 

For the purpose of illustrating how the composite risk index in Equation 6.6 would be used to classify a hypothetical waste, it is helpful to simplify Equations 6.4 and 6.5. This is done by assuming that the summation over all responses (index r) has been calculated, that only one waste classification boundary represented by the index j is being considered (i.e., the boundary between exempt and low-hazard waste, based on a negligible risk, or the boundary between low-hazard and high-hazard waste, based on an acceptable risk), and that the modifying factor (F) is unity. Further, the calculated dose in the numerator of the risk index is denoted by D and the allowable dose in the denominator is denoted by L. Then, the composite risk index for all hazardous substances in the waste, expressed in the form of Equation 6.6, can be written as  

Calculation of the composite risk index for the purpose of waste classification based on the simplified Equation 6.8 is illustrated using the hypothetical data given in Table 6.1. Consistent with the form of the risk index in Equations 6.3 and 6.8, risk indexes for individual hazardous substances in Table 6.1 are expressed as the ratio of a 

Based on the information given above, the composite risk index for the waste can be calculated and the resulting waste classification obtained. Substituting the values in Table 6.1 into Equation 6.8 results in the following  

Substances that cause deterministic responses (the first term in Equation 6.8) contribute a value of one to the composite risk index of 1.8, and substances that cause stochastic responses account for the remaining 0.8. Thus, the presence of the substances that cause deterministic responses alone would be sufficient to place this waste in Class 2. This result also would be indicated if the alternative form of the composite risk index in Equation 6.7 were used. 

---