The public depends on competent risk assessment from the federal government and the scientific community to grapple with the threat of pollution. When risk reports turn out to be overblown--or when risks are overlooked--public skepticism abounds.

This comprehensive and readable book explores how the U.S. Environmental Protection Agency (EPA) can improve its risk assessment practices, with a focus on implementation of the 1990 Clean Air Act Amendments.

With a wealth of detailed information, pertinent examples, and revealing analysis, the volume explores the "default option" and other basic concepts. It offers two views of EPA operations: The first examines how EPA currently assesses exposure to hazardous air pollutants, evaluates the toxicity of a substance, and characterizes the risk to the public.

The second, more holistic, view explores how EPA can improve in several critical areas of risk assessment by focusing on cross-cutting themes and incorporating more scientific judgment.

This comprehensive volume will be important to the EPA and other agencies, risk managers, environmental advocates, scientists, faculty, students, and concerned individuals.

Contents

• Committee On Risk Assessment Of Hazardous Air Pollutants
• Board On Environmental Studies And Toxicology
• Commission On Life Sciences
• [The National Academies]
• Other Recent Reports Of The Board On Environmental Studies And Toxicology
• Preface
• Executive Summary
• 1. Introduction
  • Charge To The Committee
  • Conceptual Framework Of The Report
• Part I. Current Approaches to Risk Assessment
  • 2. Risk Assessment and Its Social and Regulatory Contexts
    • General Concepts
    • Historical Roots
    • NRC Study Of Risk Assessment In The Federal Government
    • Events After Release Of The 1983 NRC Report
    • Uses Of Risk Assessment In The Regulation Of Hazardous Air Pollutants
    • Noncancer Risk Associated With Hazardous Air Pollutants
    • Public Criticism Of Conduct And Uses Of Risk Assessment
  • 3. Exposure Assessment
    • Introduction
    • Emission Characterization
    • Modeling Used In Exposure Assessment
  • 4. Assessment of Toxicity
    • Introduction
    • Principles Of Toxicity Assessment
    • New Trends In Toxicity Assessment
  • 5. Risk Characterization
    • Introduction
    • Elements Of Risk Characterization
• Part II. Strategies for Improving Risk Assessment
  • The Need For Risk-Assessment Principles
  • Reporting Risk Assessments
  • The Iterative Approach
  • 6. Default Options
    • Adoption Of Guidelines
    • Departures From Default Options
    • Current Epa Practice In Departing From Default options
    • Findings And Recommendations
    • Process For Departures
  • 7. Models, Methods, and Data
    • Introduction
    • Emission Characterization
    • Exposure Assessment
    • Assessment Of Toxicity
    • Findings And Recommendations
  • 8. Data Needs
    • Context Of Data Needs
    • Implications For Priority-Setting
    • Data Needed For Risk Assessment
    • Data Management
    • Findings And Recommendations
  • 9. Uncertainty
    • Context Of Uncertainty Analysis
    • Nature Of Uncertainty
    • Problems With EPA's Current Approach To Uncertainty
    • Some Alternatives To EPA's Approach
    • Specific Guidance On Uncertainty Analysis
    • Risk Management And Uncertainty Analysis
    • Comparison, Ranking, And Harmonization Of Risk Assessments
    • Findings And Recommendations
  • 10. Variability
    • Introduction And Background
    • Exposure Variability
    • Variability In Human Susceptibility
    • Conclusions
    • Findings And Recommendations
  • 11. Aggregation
    • Introduction
    • Exposure Routes
    • Risk-Inducing Agents
    • Types of Nonthreshold Risk
    • Measures And Characteristics Of Risk
    • Findings And Recommendations
• Part III. Implementation of Findings
  • 12. Implementation
    • Priority-Setting And Section 112
    • Iterative Risk Assessment
    • Epa Practices: Points To Consider
    • Institutional Issues In Risk Assessment And Management
    • Summary
    • Findings And Recommendations
• References
• Appendixes
  • Appendix A Risk Assessment Methodologies: EPA's Responses to Questions from the National Academy of Sciences
  • Appendix B EPA Memorandum from Henry Habicht
  • Appendix C Calculation and Modeling of Exposure
  • Appendix D Working Paper for Considering Draft Revisions to the U.S. EPA Guidelines for Cancer Risk Assessment
  • Appendix E Use of Pharmacokinetics to Extrapolate From Animal Data to Humans
  • Appendix F Uncertainty Analysis of Health Risk Estimates
  • Appendix G Improvement in Human Health Risk Assessment Utilizing Site- and Chemical- Specific Information: A Case Study
  • Appendix H-1 Some Definitional Concerns About Variability
  • Appendix H-2 Individual Susceptibility Factors
  • Appendix I
  • Appendix J A Tiered Modeling Approach for Assessing the Risks Due to Sources of Hazardous Air Pollutants
  • Appendix K Science Advisory Board Memorandum on the Integrated Risk Information System and EPA Response
  • Appendix L Development of Data Used in Risk Assessment
  • Appendix M Charge to the Committee
  • Appendix N-1 The Case for "Plausible Conservatism" in Choosing and Altering Defaults
  • Appendix N-2 Making Full Use of Scientific Information in Risk Assessment

The project was supported by the U.S. Environmental Protection Agency under contract CR818293-01-0.

NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competencies and with regard for appropriate balance.

This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine.