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Human Health Risk Assessments

Oregon's state superfund law emphasizes risk-based decision making. For human health risk assessments, both statute and rules provide the option of performing either a deterministic risk assessment or a probabilistic risk assessment. The Department of Environmental Quality (DEQ) has developed a guidance document for each of these options.

Copies of the Department's Human Health Risk Assessment Guidance Documents can be downloaded below.

Screening Values

Risk-Based Decision Making Screening Values

Site data can be screened using Risk-Based Concentrations (RBCs) from DEQ’s guidance document, Risk-Based Decision Making (RBDM) for the Remediation of Petroleum-Contaminated Sites. The document was originally developed in September 1999 for the tank program, and has been updated periodically. Significant updates expanded the original RBDM guidance document in September 2003 to cover hazardous substance cleanups as well as petroleum-contaminated sites. In September 2006 and March 2007, the spreadsheets associated with the guidance document were expanded to include generic RBCs for most of the hazardous substances of interest to DEQ’s Cleanup Program. Additional updates to the spreadsheets in March 2007 included changes to some exposure factors to account for early-life exposure to certain carcinogenic hazardous substances, including some petroleum constituents. The latest updates in October 2008 include revised toxicity values. The RBDM guidance document and RBC spreadsheets are available at:

The 2003 guidance document and the 2008 revised spreadsheets can be used for both

  1. cleanup of petroleum releases from regulated underground storage tanks (USTs) under the Cleanup Rules for Leaking Petroleum UST Systems (OAR 340-122-0205 through 340-122-0260); and
  2. releases of hazardous substances including petroleum under the Hazardous Substance Remedial Action Rules (OAR 340-122-0100 through 340-122-0115).

The purpose of the guidance is to provide a consistent, streamlined decision-making process for evaluating risk posed to human health and the environment. Use of the guidance is optional; other models or approaches to evaluating site risk that meet the standards in OAR 340-122-0040 may be used by responsible parties and the Department and may be more appropriate for sites where conditions vary significantly from the assumptions made when developing the RBCs.

EPA Regional Screening Values

For chemicals where RBCs are not available, DEQ uses EPA screening values. Prior to 2007, DEQ human health risk assessment guidance allowed the use of EPA Region 9 preliminary remediation goals (PRGs) as screening values for site investigations. In 2007, DEQ began using screening values developed by EPA Region 6. DEQ now uses the comprehensive table of regional screening levels developed in mid-2008 by EPA Regions 3, 6, and 9. The EPA regional screening values are available at:

Screening values are tools for evaluating and cleaning up contaminated sites. They are risk-based concentrations that are intended to assist risk assessors and others in initial screening-level evaluations of environmental measurements. The screening values developed by EPA are generic; they are calculated without site specific information.

Screening values should be viewed as guidelines, not legally enforceable standards. They are used for site screening and as initial cleanup goals if applicable. Screening values are not de facto cleanup standards and should not be applied as such. However, they are helpful in providing long-term targets to use during the analysis of different remedial alternatives.

Implementation Schedule

The revised DEQ and EPA RBCs should be implemented according the following guidelines:

  1. For all newly initiated screening evaluations at a site, the recently revised RBCs and EPA regional screening values will be used from this point forward;
  2. For screening evaluations currently being performed, the revised RBCs and EPA regional screening values will be used on a case-by-case basis; and
  3. For completed screening evaluations submitted before October 9, 2008, reassessments may be performed on a case-by-case basis when a new decision is required that needs to be supported by a screening evaluation or updated risk assessment. Until that time, the current completed and approved screening evaluation will continue to be considered valid based on the guidance used when the assessment was completed.

EPA intends to update their screening table biannually. DEQ will evaluate updates to EPA screening values, and update RBCs in January of each year. Under special circumstances, DEQ may at any time require a revised screening value for a chemical based on new toxicity information.

Other Important Risk-Related Web Sites

Comments regarding the implementation or technical content of Deterministic Human Health Risk Assessments and Guidance for Use of Probabilistic Analysis in Human Health Risk Assessments should be directed to:

Mike Poulsen
Oregon Department of Environmental Quality
2020 SW 4th Ave., Suite 400
Portland, OR 97201
503 229-6773
In Oregon, call toll-free 1-800-452-4011

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For more information about DEQ's Land Quality programs, visit the DEQ contact page.

Oregon Department of Environmental Quality
Headquarters: 811 SW Sixth Ave., Portland, OR 97204-1390
Phone: 503-229-5696 or toll free in Oregon 1-800-452-4011
Oregon Telecommunications Relay Service: 1-800-735-2900  FAX: 503-229-6124

The Oregon Department of Environmental Quality is a regulatory agency authorized to protect Oregon's environment by
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