The 1ppb dioxin soil concentration should not be used as a comparison value for defining public health hazards in public health assessments and consultations. The 1ppb action level can be cited by health assessors as the Superfund Dioxin Cleanup policy criteria (EPA 1989, 1998).

Retention of the 0.05 ppb Screening Level

The minimal risk level (MRL)based environmental media evaluation guide (EMEG) of 0.05 ppb for dioxin TEQ in soil is retained as the basis for screening soil concentrations. Levels exceeding this screening level should be evaluated as described in the ATSDR Public Health Assessment Guidance Manual (PHAGM) (ATSDR 2005). This clarification will ensure that evaluation of dioxins and dioxinlike compounds in soil will be done in the same manner as all other soil contaminants.
Recommendation To Conduct Exposure Pathways Analyses for Dioxins and DioxinLike Compounds

The focus of the guideline is the assessment of direct exposure to soil contamination, particularly soil ingestion. However, health assessors should be aware of the potential impact of indirect exposure pathways on exposed populations in sitespecific health assessments. This document does not provide specific guidance on how these indirect pathways should be assessed. However, the PHAGM document does provide assistance in evaluating indirect exposure pathways such as food chain contamination (ATSDR 2005).

Updated TEFs

The 2006 World Health Organization Toxicity Equivalency Factors (TEFs) for dioxins and dioxinlike compounds have been included in the updated document.

Background Information

In 1998, the Agency for Toxic Substances and Disease Registry (ATSDR) adopted a Final Policy Guideline for Dioxin and DioxinLike Compounds (De Rosa et al. 1999a). The 1998 policy guideline was accompanied by a Technical Support Document for ATSDR Policy Guideline (De Rosa et al. 1999b). The initiative to develop this policy guideline was based on a request from the U.S. Environmental Protection Agency (EPA) to evaluate the protectiveness of the EPA Superfund Policy for Dioxins in Residential Soils, which established 1 part per billion (ppb) (1,000 parts per trillion [ppt]) total dioxin toxicity equivalents (TEQ) as the starting point for making cleanup decisions. In addition, the 1998 policy guideline was to provide guidance to health assessors in evaluating the public health implications of dioxin and dioxinlike compounds (e.g., 2,3,7,8tetrachlorodibenzopdioxin [TCDD], chlorinated dibenzodioxins [CDDs], chlorinated dibenzofurans [CDFs], and other structurally related groups of chemicals from the family of halogenated aromatic hydrocarbons) in residential soils near or on hazardous waste sites. As stated in the 1998 document, ``these guidelines and procedures apply to human exposure for direct ingestion of soils contaminated with dioxin and dioxinlike compounds in residential areas and may not be appropriate for other exposure scenarios.'' The 1998 Policy Guideline established a screening level of 0.05 ppb TEQ (50 ppt), an evaluation level (>0.05 ppb TEQ, <1 ppb), and an action level of 1 ppb TEQ (1,000 ppt) for dioxins in residential soil and made recommendations for specific considerations or public health actions.

ATSDR has established environmental screening values for chemicals to be used by health assessors to assess exposures. No other chemical has an action level as was established for dioxins in soil in the 1998 policy guideline. This inconsistency alone has led to confusion regarding the appropriate screening value for soil dioxin levels.

The primary objectives of the updated Policy Guidelines are to provide greater consistency in ATSDR Health Assessments and to bring dioxin assessments in line with how all other chemicals are evaluated by the agency.

Summary of Peer Review for Document

The public comment draft of the revised policy has undergone internal review and clearance within ATSDR. In addition, the revised draft was reviewed by the National Center for Environmental Health/ Agency for Toxic Substances and Disease Registry (NCEH/ATSDR) Board of Scientific Counselors (BSC). Public testimony was received during the meeting of the NCEH/ATSDR BSC. ATSDR also received peer review comments from health assessors in several state health departments.

Information about the ``Update to ATSDR Policy Guideline for Dioxins and DioxinLike Compounds in Residential Soil'', including the draft document, fact sheet, peer review
[[Page 78442]]
comments and ATSDR responses, is available on the ATSDR Web site at: http://www.atsdr.cdc.gov/substances/dioxin/policy/index.html.

SUMMARY: Dioxins and dioxin-like compounds in residential soil; policy guideline update,

FOR FURTHER INFORMATION CONTACT Ms. Athena Gemella, Office of Science, telephone (404) 4980621.

Dated: December 22, 2006.
Kenneth Rose,
Acting Director, Office of Policy, Planning and Evaluation, National Center for Environmental Health/Agency for Toxic Substances and Disease Registry.
[FR Doc. E622388 Filed 122806; 8:45 am]
BILLING CODE 416370P