When updated RBCs are used, they should be used for all chemicals of interest for a facility.Typically approved screenings and risk assessments do not require reassessment unless a new decision is requested or required, and that decision needs the support of a current screening evaluation or risk assessment. For completed and approved evaluations, reassessment may be performed on a case-by-case basis.For screenings and risk assessments currently underway, the updated RBCs and EPA regional screening values apply on a case-by-case basis.New screenings and risk assessments should use the updated RBC tables, unless DEQ and parties agree to use of alternative approaches.In general, the updated RBCs should be implemented as follows: Parties should use the updated tables for new screenings and risk assessments, unless DEQ and parties agree to use of alternative approaches. The May 2018 spreadsheet contain the correct values. In preparing the 2015 table, an error occurred that result in these values being listed incorrectly. Updated to show the correct soil leaching to groundwater (RBCsw).Note that RBC calculations for TCE are contained in the March 2018 Calculation of Trichloroethene RBCs using Early-Life Exposure Memorandum. Changes to standard exposure assumptions will not be automatically incorporated into early-life exposure assumptions. The update allows parties to modify related assumption parameters. Unlocked spreadsheet cells for early-life exposure assumptions.The update allows parties to modify assumption parameters. Unlocked spreadsheet cells and other formatting errors that prevented site-specific calculations for new chemicals.Updated the site-specific table of Risk-Based Concentrations for Individual Chemicals:. ![]() The May 2018 table accurately shows the lowest cancer or noncancer RBCs. In preparing the 2015 table, the lowest of the cancer or noncancer RBCs were not always selected. Updated to show the lowest cancer or noncancer RBCs are provided.Updated the generic table of Risk-Based Concentrations for Individual Chemicals:.RBCs for 1,2,4-trimethylbenzene are now generally about 2 to 4 times higher than previous RBCs, and RBCs for 1,3,5-trimethylbenzene are now generally about half the previous RBCs. New noncancer RBCs for DDD are generally lower than previous RBCs. Updated toxicity factors for dichlorodiphenyldichloroethane (DDD), 1,2,4-trimethylbenzene, and 1,3,5-trimethylbenzene.In addition, no cancer effects (including developmental effects) can now be quantitatively evaluated for benzopyrene. This update generally results in risk-based screening levels that are higher by about a factor of 7. ![]() Environmental Protection Agency’s 2017 update.
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