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7 Review of Risk Characterization
Pages 175-187

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From page 175...
... 7 Review of Risk Characterization The Reassessment1 (Part III, Chapter 6) considers risk characterization under a series of headings, many of which represent summaries of the inputs to risk characterization instead of the output of risk characterization and its formulation of advice to risk managers.
From page 176...
... 176 HEALTH RISKS FROM DIOXIN AND RELATED COMPOUNDS Clearly adverse effects, including, perhaps, cancer, may not be detectable until exposures contribute to body burdens that exceed current back grounds by one or two orders of magnitude (10 to 100 times)
From page 177...
... REVIEW OF RISK CHARACTERIZATION 177 will be used in future risk assessments of TCDD, other dioxins and DLCs. The committee's recommendations related to TEFs appear in Chapter 3.
From page 178...
... 178 HEALTH RISKS FROM DIOXIN AND RELATED COMPOUNDS ods used by EPA to detect a departure from linearity, were one to exist; or of the indications of nonlinearity in the dose-response relationships for many noncancer effects also considered to be mediated via an interaction with the AHR. The Reassessment attempts to explain the decision to use a linear approach (Part III, p.
From page 179...
... REVIEW OF RISK CHARACTERIZATION 179 this approach for the U.S. population.
From page 180...
... 180 HEALTH RISKS FROM DIOXIN AND RELATED COMPOUNDS appropriate because of the relatively high background levels of exposure compared with effect levels (Reassessment, Part III, p.
From page 181...
... REVIEW OF RISK CHARACTERIZATION 181 be above any RfD, it would have been useful for EPA to define the nature and magnitude of the risks at different levels of intake, the groups of the population most at risk, and the major sources of exposure for any at-risk groups. Alternatively, if MOEs were calculated for noncancer effects, then the risk characterization should describe the nature of the adverse effect and the uncertainties and variability inherent in both the BMD (ED)
From page 182...
... 182 HEALTH RISKS FROM DIOXIN AND RELATED COMPOUNDS ment, Part III, p. 6-17, lines 21-23)
From page 183...
... REVIEW OF RISK CHARACTERIZATION 183 uncertainty factors. The Reassessment does not give the rationale for EPA's decision not to replace the default uncertainty factors by chemical-specific data, despite the enormity of the TCDD database.
From page 184...
... 184 HEALTH RISKS FROM DIOXIN AND RELATED COMPOUNDS Background Exposures to TCDD, Other Dioxins, and DLCs Need To Be Considered When Evaluating Hazard and Risk Reassessment (Part III, pp.
From page 185...
... REVIEW OF RISK CHARACTERIZATION 185 animal studies (that is, on those involving in utero exposure and subsequent assessment of developmental parameters in early life)
From page 186...
... 186 HEALTH RISKS FROM DIOXIN AND RELATED COMPOUNDS CONCLUSIONS AND RECOMMENDATIONS The committee considered Chapter 6 of Part III of the Reassessment to be the most important section, but in many ways it was the weakest and least scientifically rigorous in its support of the decisions made. EPA used linear extrapolation from the POD, the ED01, derived from the cancer epidemiological studies to calculate a CSF.
From page 187...
... REVIEW OF RISK CHARACTERIZATION 187 als with high intakes. The lack of such a focus in the Reassessment results in a diffuse risk characterization that is difficult to follow and that does not provide clear guidance to risk managers.

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