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Risk Assessment Guidance for Superfund (RAGS) Volume III - Part A: Process for Conducting Probabilistic Risk Assessment (2001)

Risk Assessment Guidance for Superfund Volume III: Part A (RAGS: Volume 3A) provides policies and guiding principles on the application of probabilistic risk assessment (PRA) methods to human health and ecological risk assessment in the U.S. Environmental Protection Agency (EPA) Superfund program. Volume 3A supplements existing human health and ecological assessment guidance provided in the RAGS series. Volume 3A builds upon basic concepts of risk assessment outlined in RAGS Volume I (U.S. EPA, 1989a; 2001), recent guidance for Ecological Risk Assessment (U.S. EPA, 1992, 1994, 1997a, 1998a; 1999), and the Agency Probabilistic Analysis Policy document (U.S. EPA, 1997b). Volume 3A focuses on Monte Carlo analysis as a method of quantifying variability and uncertainty in risk. This guidance was developed by the Superfund Probabilistic Risk Assessment Workgroup and the Ecological Risk Assessment Forum; both are intra-Agency workgroups that have focused on improving the Risk Assessment Guidance for Superfund and implementing Superfund Reform activities. Volume 3A is intended to be most accessible to those readers who are familiar with risk assessment and basic statistical concepts. This guidance introduces a tiered approach to PRA, beginning with a point estimate analysis and progressing to increasing levels of complexity until the scope of the analysis satisfies decision-making needs. Potential users of this guidance include risk assessors, risk managers, and other decision makers responsible for conducting and reviewing PRA, or communicating PRA concepts and results.

Federal Register Notice regarding RAGS Volume. III Part A.

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Risk Assessment Guidance for Superfund: Volume III - Part A, Process for Conducting Probabilistic Risk Assessment (PDF) (385 pp, 8 MB). If you need help accessing the content of this PDF document, please use our online contact form to request assistance.

The link above is a large PDF for the entire guidance document.

The below links are for viewing/downloading one section at a time.


  • Cover (PDF) (19 pp, 82K) includes Table of Contents, Accronyms and Abbreviations, Acknowlegdements, Work Group Members
  • Chapter 1 (PDF) (34 pp, 483K) Overview of Probabilistic Approach to Risk Assessment
  • Chapter 2 (PDF) (19 pp, 349K) Workplan and the Tiered Approach
  • Chapter 3 (PDF) (27 pp, 1.5MB) Using Probabilistic Analysis in Human Health Assessment
  • Chapter 4 (PDF) (49 pp, 2MB) Probabilistic Analysis in Ecological Risk Assessment
  • Chapter 5 (PDF) (25 pp, 536K) Probabilistic Analysis Risk Assessment and Preliminary Remediation Goals
  • Chapter 6 (PDF) (25 pp, 364K) Communicating Risks and Uncertainties in Probabilistic Risk Assessments
  • Chapter 7 (PDF) (16 pp, 383K) Role of the PRA in Decision Making
  • Appendix A (PDF) (37 pp, 959K) Sensitivity Analysis: How Do We Know What's Important?
  • Appendix B (PDF) (52 pp, 461K) Selection and Fitting of Distributions
  • Appendix C (PDF) (16 pp, 171K) Characterizing Variability and Uncertainty in the Concentration Term
  • Appendix D (PDF) (27 pp, 384K) Advanced Modeling Approaches for Characterizing Variability and Uncertainty
  • Appendix E (PDF) (19 pp, 153K) Definitions of Terms Relevant to PRA and References for Further Reading
  • Appendix F (PDF) (6 pp, 29K) Workplan and Checklist for PRA
  • Appendix G (PDF) (6 pp, 23K) Frequently Asked Questions for PRA
  • Appendix H (PDF) (3 pp, 37K) Index

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