Cumulative Risk Adjustment

• Cumulative risk for exposure to multiple chemicals (TNRCC)

• Cancer target risk = 10-4

• Non-cancer hazard index = 10

• If needed on a site specific basis the PCL values must be adjusted down to meet the cumulative targets

• Adjustments are made to any, or all of the COC

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There is not one solution to this issue. The TNRCC rationale is explained in Appendix I Section 3.

In the back calculation the cumulative effects are not as easily handled, but it is possible