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"action" levels set forth in Appendix D of the proposed Subpart S <br /> Corrective Action rule. In the July 27, 1990 RCRA proposal (55 <br /> Federal Register 30798) , EPA introduced the concept of "action <br /> levels" as trigger levels for further study and subsequent <br /> remediation at RCRA facilities. In this respect, the current <br /> directive's "screening levels" are analogous to the proposed <br /> rule's "action levels. " In the proposal, where data were <br /> available, action levels were developed for three pathways of <br /> human exposure to contaminants.: soil ingestion, water ingestion <br /> and inhalation of contaminated air. Exposure assumptions used in <br /> the calculations were set out in Appendix D of the proposal. For <br /> the soil pathway, action levels were calculated two different <br /> ways depending on whether the contaminant in the soil was a <br /> carcinogen or a systemic toxicant. Although lead was listed in <br /> Appendix A of the preamble to the rule as a class B2 carcinogen, <br /> no action level had been calculated because neither a <br /> carcinogenic slope factor (SF) nor a reference dose (RfD) had <br /> been developed by the Agency. Although the guidance in Appendix <br /> D of the proposed Corrective Action rule remains in effect with <br /> respect to other hazardous constituents, this directive now <br /> allows for the development of the lead screening ("action") level <br /> using the IEUBK model. <br /> Recent developments (1992-Present) . Following discussions among <br /> senior Regional and OSWER management, the OSWER Soil Lead <br /> Directive Workgroup (composed of Headquarters, Regional and other <br /> Federal agency representatives) recommended in the spring of 1992 <br /> that a "two step" decision framework be developed for <br /> establishing cleanup le✓els at sites with lead-contaminated <br /> soils. This framework would identify a single level of lead in <br /> soils that could be used as either the PRG for CERCLA site <br /> cleanups or the action level for RCRA Corrective Action sites, <br /> but would also allow site managers to establish site-specific <br /> cleanup levels (where appropriate) based on site-specific <br /> circumstances. The IEUBK model would be an integral part of this <br /> framework. OSWER then developed a draft of this directive which <br /> it circulated for review on June 4, 1992. The draft set 500 ppm <br /> as a PRG and an action level for RCRA facilities in residential <br /> settings. <br /> Following development of this draft, OSWER held a meeting on <br /> July 31, 1992 to solicit a broad range of views and expertise. A <br /> wide range of interests, including environmental groups, citizens <br /> and representatives from the lead industry attended. This <br /> meeting encouraged OSWER to think more broadly about how the <br /> directive would affect urban areas, how lead paint and dust <br /> contribute to overall risk, and how blood lead data could be used <br /> to assess risk. In subsequent meetings with the Agency for Toxic <br /> Substances and Disease Control (ATSDR) and the Centers for <br /> Disease Control (CDC) , options were discussed on how to use blood <br /> lead data and the need to evaluate the contribution of paint. In <br /> addition, during these meetings, a "decision tree" approach was <br /> -7- <br />