Health Risk Assessments Prepared per the Risk Assessment Reforms under Consideration in the U.S. Congress Cambridge Environmental Inc. 58 Charles Street Cambridge, MA 02141 1. Summary The Commission on Risk Assessment and Risk Management retained Cambridge Environmental Inc. to conduct case studies of health risk assessment that conform with proposed regulatory reform legislation 1 and to comment, as risk assessors, on the required methods. To illustrate the techniques required to satisfy such a mandate, we studied four cases. We then prepared a distribution of risk estimates by choosing parameter values for each variable from the distribution defined for that variable and combining these choices in the risk equation. The results of the four case studies are summarized in the following table.
Several comparisons are noteworthy.
Although such an upper-bound point estimate is typically assumed by many to be at about the 95 th percentile of the risk estimate distribution, it corresponded here to the 99.8th percentile of such a distribution. Risks as high as the former often require extensive remediation, whereas risks as low as the latter usually do not. Such a minor difference belies the substantial differences in the quality and quantity of data surrounding the carcinogenicity of these two chemicals. Under certain circumstances, such as relatively high exposures, the deterministic and probabilistic methods may thus yield reasonably similar upper-bound estimates of risk. Working through these case studies, we have reached certain conclusions about the proposed risk assessment reforms.