Risk Assessment

Regional Screening Levels (RSLs)

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For assistance/questions please use the Regional Screening Levels (RSLs) contact us page.

Welcome

Welcome to the "Regional Screening Levels for Chemical Contaminants at Superfund Sites" screening level/preliminary remediation goal website. This website was developed with DOE's Oak Ridge National Laboratory (ORNL) under an Interagency Agreement as a merger of the EPA Region 3 RBC Table, Region 6 HHMSSL Table and the Region 9 PRG Table. The RSL website is now the source of screening levels for all the EPA regions. The RSL tables provide comparison values for residential and commercial/industrial exposures to soil, air, and tapwater (drinking water). The unified use of the RSLs, to screen chemicals at Superfund sites, promotes national consistency. Here you will find tables of risk-based screening levels, calculated using the latest toxicity values, default exposure assumptions and physical and chemical properties, and a calculator where default parameters can be changed to reflect site-specific risks. To ensure proper use of the screening level tables and the calculator, please review the What's NewUser's GuideFrequent Questions, and Download Area links. Below is a general description of screening levels for chemical contaminants. If the calculator is used with non-default inputs in a decision on a Superfund site, it is recommended that the inputs be clearly identified and justified by the user.

Introduction

Screening Level Calculation ChartScreening Level Calculation ChartSuperfund sites are addressed under the authority of the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) of 1980, which was amended by the 1986 Superfund Amendments and Reauthorization Act. The purpose of this website is to provide a screening level calculation tool to assist risk assessors, remedial project managers, and others involved with risk assessment and decision-making at CERCLA sites in developing or refining screening levels.

This tool is based on Risk Assessment Guidance for Superfund: Volume I, Human Health Evaluation Manual (Part B, Development of Risk-based Preliminary Remediation Goals) (RAGs Part B) and Soil Screening Guidance: User's Guide (PDF) (89 pp, 863 K)Technical Background Document (PDF) (447 pp, 4.7 MB) and Supplemental Guidance (PDF) (187 pp, 2.2 MB). RAGs Part B provides guidance on using EPA toxicity values and exposure information to calculate risk-based Screening Levels (SLs). The relationship of Preliminary Remediation Goals (PRGs) to screening levels (SLs) is discussed in more detail in the User's Guide. The Soil Screening Guidance documents expand upon RAGS Part B. Initially used at the scoping phase of a project using readily available information, risk-based screening levels generally are modified based on site-specific data gathered during the RI/FS study. Screening level development and screening should assist staff in streamlining the consideration of remedial alternatives. Chemical-specific SLs are from two general sources: (1) concentrations based on potential Applicable or Relevant and Appropriate Requirements (ARARs) and (2) concentrations based on risk assessment. ARARs include concentration limits set by other environmental regulations, such as Safe Drinking Water Act maximum contaminant levels (MCLs). The second source for SLs, and the focus of this database tool, is risk-based calculations that set concentration limits using carcinogenic or systemic toxicity values under specific exposure conditions.

The recommended approach for developing remediation goals is to identify screening levels at scoping, modify them as needed at the end of the RI or during the FS based on site-specific information from the baseline risk assessment, and ultimately select remediation levels in the ROD.

Screening levels are also used when a potential site is initially investigated to determine if potentially significant levels of contamination are present to warrant further investigation such as an RI/FS.

In order to set chemical-specific SLs in a site-specific context, however, assessors must answer fundamental questions about the site, such as information on the chemicals that are present onsite, the specific contaminated media, land-use assumptions, and the exposure assumptions behind pathways of individual exposure.

Once this web tool is used to retrieve standard screening levels or calculate site-specific screening levels, it is important to clearly demonstrate the equation inputs used in the calculations. Discussion of the assumptions that go into the screening level calculations should be included in the document where the screening levels are presented.

This tool presents standardized risk-based screening levels and variable risk-based screening level calculation equations for chemical contaminants. Screening levels are presented in the default tables for residential soil, outdoor worker soil, residential indoor air, worker indoor air and tap water. In addition, the calculator provides a fish ingestion equation. The risk-based screening levels for chemicals are based on the carcinogenicity and systemic toxicity of the analytes. The standardized or default screening levels used in the tables on this website are based on default exposure parameters and incorporate exposure factors that present RME conditions.

Radionuclides are not addressed on this website. For radionuclide PRGs please go to EPA's PRGs for Radionuclides.

Note: No consideration is given to ecological effects in the values presented in this database tool.

For assistance/questions please use the Regional Screening Levels (RSLs) contact us page.