Review of the National Ambient Air Quality Standards for Particulate Matter: Policy Assessment of Scientific and Technical Information OAQPS Staff Paper – First Draft EPA-452/D-03-001 August 2003 First Draft Review of the National Ambient Air Quality Standards for Particulate Matter: Policy Assessment of Scientific and Technical Information OAQPS Staff Paper – First Draft Office of Air Quality Planning and Standards U.S. Environmental Protection Agency Research Triangle Park, NC 27711 August 2003 Draft – Do Not Quote or Cite DISCLAIMER This document has been reviewed by the Office of Air Quality Planning and Standards (OAQPS), U.S. Environmental Protection Agency (EPA), and approved for release. This draft OAQPS Staff Paper contains the preliminary conclusions and recommendations of the staff of the OAQPS and does not necessarily represent those of the EPA. Mention of trade names or commercial products is not intended to constitute endorsement or recommendation for use. August 2003 Draft – Do Not Quote or Cite Table of Contents List of Tables................................................................ vi List of Figures .............................................................. viii Abbreviations and Acronyms .................................................. xiii 1. INTRODUCTION ........................................................ 1-1 1.1 PURPOSE ..................................................... 1-1 1.2 BACKGROUND ................................................ 1-2 1.2.1 Legislative Requirements ................................... 1-2 1.2.2 History of PM NAAQS Reviews .............................. 1-4 1.2.3 Litigation Related to 1997 PM Standards ....................... 1-5 1.2.4 Current PM NAAQS Review ................................. 1-7 1.3 APPROACH ................................................... 1-8 REFERENCES ...................................................... 1-10 2. AIR QUALITY CHARACTERIZATION .................................... 2-1 2.1 INTRODUCTION ............................................... 2-1 2.2 CHARACTERIZATION OF AMBIENT PARTICULATE MATTER ...... 2-1 2.2.1 Particle Size Distributions ................................... 2-2 2.2.1.1 Modes ............................................. 2-2 2.2.1.2 Sampler Cut Points .................................. 2-6 2.2.2 Sources and Formation Processes ............................. 2-8 2.2.3 Chemical Composition ...................................... 2-9 2.2.4 Fate and Transport ........................................ 2-10 2.3 SOURCE EMISSIONS.......................................... 2-12 2.3.1 Primary PM Emissions .................................... 2-12 2.3.2 Secondary PM Precursor Emissions .......................... 2-14 2.4 AMBIENT PM MEASUREMENT METHODS ....................... 2-15 2.4.1 Particle Mass Measurement Methods ......................... 2-15 2.4.2 Size-Differentiated Particle Number Concentration Measurement Methods ....................................................... 2-17 2.4.3 Chemical Composition Measurement Methods .................. 2-17 2.4.4 Measurement Issues. 2-18 2.5 PM CONCENTRATIONS, TRENDS, AND SPATIAL PATTERNS IN THE U.S. ............................................................. 2-19 2.5.1 PM2.5 ................................................... 2-19 2.5.2 PM10 ................................................... 2-29 2.5.3 PM10-2.5 ................................................. 2-29 2.5.4 Ultrafine Particles ........................................ 2-37 2.5.5 Components of PM ....................................... 2-38 August 2003i Draft – Do Not Quote or Cite 2.5.6 Relationships Among PM2.5, PM10, and PM10-2.5 ................. 2-41 2.6 TEMPORAL PATTERNS IN PM CONCENTRATIONS ............... 2-42 2.6.1 PM2.5 and PM10-2.5 Patterns.................................. 2-42 2.6.2 Ultrafine Patterns ......................................... 2-48 2.7 PM BACKGROUND LEVELS .................................... 2-51 2.8 RELATIONSHIP BETWEEN HUMAN EXPOSURE TO AMBIENT PM AND CENTRAL MONITOR MEASUREMENTS OF PM................... 2-54 2.8.1 Definitions .............................................. 2-55 2.8.2 Centrally Monitored PM Concentration as a Surrogate for Particle Exposure ............................................... 2-56 2.9 OPTICAL AND RADIATIVE PROPERTIES OF PARTICLES .......... 2-61 2.9.1 PM Properties Affecting Visibility ........................... 2-61 2.9.2 PM Properties Affecting Climate ............................ 2-62 2.9.2 PM Properties Affecting Transmission of Ultraviolet Radiation .... 2-64 REFERENCES ...................................................... 2-65 3. CHARACTERIZATION OF PM-RELATED HEALTH EFFECTS .............. 3-1 3.1 INTRODUCTION ............................................... 3-1 3.2 MECHANISMS ................................................. 3-3 3.3 NATURE OF EFFECTS.......................................... 3-9 3.3.1 Premature Mortality ........................................ 3-12 3.3.1.1 Mortality and Short-term PM Exposure ................. 3-13 3.3.1.1.1 Multi-city Studies of Total Daily Mortality ....... 3-16 3.3.1.1.2 Other Studies of Total Daily Mortality .......... 3-23 3.3.1.1.3 Cause-specific Daily Mortality ................ 3-29 3.3.1.2 Mortality and Long-term PM Exposure .................. 3-31 3.3.1.3 Infant Mortality .................................... 3-40 3.3.1.4 Mortality Displacement and Life-Shortening ............. 3-41 3.3.2 Indices of Morbidity ...................................... 3-43 3.3.2.1 Hospital Admissions and Emergency Room Visits ......... 3-44 3.3.2.2 Effects on the Respiratory System ...................... 3-53 3.3.2.2.1 Acute Respiratory Effects .................... 3-53 3.3.2.2.2 Chronic Respiratory Effects ................... 3-58 3.3.2.3 Effects on the Cardiovascular System ................... 3-62 3.3.2.4 Developmental Effects ............................... 3-65 3.4 SENSITIVE GROUPS FOR PM-RELATED HEALTH EFFECTS........ 3-65 3.4.1Preexisting disease as a risk factor . 3-65 3.4.2Age-related risk factors . 3-67 3.5 EVALUATION OF PM-RELATED HEALTH EFFECTS EVIDENCE.... 3-68 3.5.1 Role of Gaseous Co-pollutants .............................. 3-69 3.5.2 Issues Related to Epidemiological Modeling ................... 3-74 3.5.2.1 Model Specification ................................. 3-75 3.5.2.2 Lag Periods ....................................... 3-78 3.5.2.3 Measurement Error ................................. 3-80 August 2003ii Draft – Do Not Quote or Cite 3.5.3 Consideration of Evidence on PM Size and Composition .......... 3-82 3.5.3.1 Ultrafine particles .................................. 3-82 3.5.3.2 PM Components and Source-Related Particles ............ 3-83 3.5.4 Consistency and Coherence of Health Effects Evidence ........... 3-89 3.5.4.1 Consistency ....................................... 3-89 3.5.4.2 Coherence ........................................ 3-98 REFERENCES ..................................................... 3-102 4. CHARACTERIZATION OF HEALTH RISKS ............................... 4-1 4.1 INTRODUCTION ............................................... 4-1 4.1.1 Goals for Updated PM Risk Assessment ........................ 4-3 4.1.2 Summary of Risk Assessment Conducted During Prior PM NAAQS Review.................................................. 4-3 4.2 GENERAL SCOPE OF PM RISK ASSESSMENT ..................... 4-5 4.2.1 Overview of Components of the Risk Model .................... 4-9 4.2.2 Criteria for Selection of Health Endpoints and Urban Study Areas . 4-10 4.2.2.1 Selection of Health Endpoint Categories ................. 4-12 4.2.2.2 Selection of Study Areas ............................. 4-13 4.2.3 Air Quality Considerations ................................. 4-17 4.2.3.1 Estimating PM Background Levels ..................... 4-24 4.2.3.2 Simulating PM Levels That Just Meet Specified Standards . 4-24 4.2.4 Approach to Estimating PM-Related Health Effects Incidence ..... 4-27 4.2.5 Baseline Health Effects Incidence Rates and Population Estimates . 4-29 4.2.6 Concentration-Response Functions Used in Risk Assessment ...... 4-30 4.2.6.1 Hypothetical Thresholds ............................. 4-31 4.2.6.2 Single and Multi-Pollutant Models ..................... 4-33 4.2.6.3 Single, Multiple, and Distributed Lag Functions ........... 4-34 4.2.6.4 Long-term Exposure Mortality PM2.5 Concentration-Response Functions......................................... 4-35 4.2.7 Characterizing Uncertainty and Variability ..................... 4-36 4.3 PM2.5, PM10-2.5, and PM10 RISK ESTIMATES FOR CURRENT (“AS IS”) AIR QUALITY .................................................... 4-40 4.3.1 Summary of Risk Estimates ................................. 4-40 4.3.2 Sensitivity Analyses ....................................... 4-58 4.3.3 Key Observations ......................................... 4-64 4.4 RISK ESTIMATES ASSOCIATED WITH JUST MEETING THE CURRENT PM2.5 STANDARDS ............................................ 4-67 4.4.1 Summary of Risk Estimates ................................. 4-67 4.4.2 Sensitivity Analyses ....................................... 4-71 4.4.3 Key Observations ......................................... 4-73 4.5 RISK ESTIMATES ASSOCIATED WITH JUST MEETING ALTERNATIVE PM2.5 AND PM10-2.5 STANDARDS ................................. 4-73 REFERENCES ...................................................... 4-74 August 2003iii Draft – Do Not Quote or Cite 5. CHARACTERIZATION OF PM-RELATED WELFARE EFFECTS ............. 5-1 5.1