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.

The Reassessment should describe clearly the following aspects:

  1. The effects seen at the lowest body burdens that are the primary focus for any risk assessment—the “critical effects.”

  2. The modeling strategy used for each noncancer effect, paying particular attention to the critical effects, and the selection of a point of comparison based on the biological significance of the effect; if the ED01 is retained, then the biological significance of the response should be defined and the precision of the estimate given.

  3. The precision and uncertainties associated with the body burden estimates for the critical effects at the point of comparison, including the use of total body burden rather than modeling steady-state concentrations for the relevant tissue.

  4. The committee encourages EPA to calculate RfDs as part of its effort to develop appropriate margins of exposure for different end points and risk scenarios, including the proportions of the general population and of any identified groups that might be at increased risk (See Table A-1 in the Reassessment, Part III Appendix, for the different effects; appropriate exposure information would need to be generated.) Interpretation of the calculated values should take into consideration the uncertainties in the POD values and intake estimates.

  5. Consideration of individuals in susceptible life stages or groups (e.g., children, women of childbearing age, and nursing infants) who might require an estimation of a separate MOE using specific exposure data.

  6. Distributions that provide clear insights about the uncertainty in the risk assessments, along with discussion about the key contributors to the uncertainty.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement