Regulatory Impact Analysis for the Proposed 

Revisions to the National Ambient Air Quality 

Standards for Particulate Matter
EPA-452/R-12-003

June 2012

Regulatory Impact Analysis for the Proposed Revisions to the National Ambient Air Quality 

Standards for Particulate Matter

Contract No. EP-W-11-029

Work Assignment Number: 0-03

U.S. Environmental Protection Agency

Office of Air Quality Planning and Standards

Health and Environmental Impacts Division

Research Triangle Park, NC 27711
iii

CONTENTS

Section Page

Executive Summary.............................................................................................................. ES-1

ES.1 Overview ......................................................................................................... ES-1

ES.2 Existing and Alternative PM Air Quality Standards ........................................ ES-1

ES.2.1 Establishing the Baseline .................................................................... ES-3

ES.2.2 Emission Reduction Estimates by Alternative Standards (2020)........ ES-5

ES.2.3 Health and Welfare Benefits Analysis Approach................................ ES-5

ES.2.4 Cost Analysis Approach....................................................................... ES-7

ES.2.5 Comparison of Benefits and Costs...................................................... ES-7

ES.2.6 Conclusions of the Analysis................................................................. ES-8

ES.3 Caveats and Limitations................................................................................ ES-11

ES.3.1 Benefits Caveats................................................................................ ES-11

ES.3.2 Control Strategy and Cost Analysis Caveats and Limitations ........... ES-12

ES.3.3 Limitations of the Secondary Standard Analysis .............................. ES-13

ES.4 Discussion...................................................................................................... ES-13

ES.5 References .................................................................................................... ES-15

Chapter 1 Introduction and Background ............................................................................... 1-1

1.1 Synopsis............................................................................................................. 1-1

1.2 Background ....................................................................................................... 1-1

1.2.1 NAAQS................................................................................................... 1-1

1.2.2 2006 PM NAAQS ................................................................................... 1-2

1.3 Role of this RIA in the Process of Setting the NAAQS....................................... 1-2

1.3.1 Legislative Roles.................................................................................... 1-2

1.3.2 Role of Statutory and Executive Orders................................................ 1-3

1.3.3 The Need for National Ambient Air Quality Standards ........................ 1-3

1.3.4 Illustrative Nature of the Analysis ........................................................ 1-4
iv

1.4 Overview and Design of the RIA ....................................................................... 1-4

1.4.1 Modeling PM2.5 Levels in the Future (Analysis Year = 2020)................ 1-4

1.4.2 Existing and Alternative PM Air Quality Standards .............................. 1-5

1.4.3 Benefits Analysis Approach................................................................... 1-6

1.4.4 Costs Analysis Approach ....................................................................... 1-6

1.5 Organization of this Regulatory Impact Analysis.............................................. 1-7

Chapter 2 Defining the PM Air Quality Problem.................................................................... 2-1

2.1 Synopsis............................................................................................................. 2-1

2.2 Particulate Matter (PM) Properties.................................................................. 2-1

2.2.1 PM2.5...................................................................................................... 2-4

2.2.2 Visibility............................................................................................... 2-10

2.3 References ...................................................................................................... 2-14

Chapter 3 Air Quality Modeling and Analysis........................................................................ 3-1

3.1 Synopsis............................................................................................................. 3-1

3.2 Modeling PM2.5 Levels in the Future................................................................. 3-1

3.2.1 Air Quality Modeling Platform.............................................................. 3-1

3.2.2 Emissions Inventory .............................................................................. 3-4

3.3 Modeling Results and Analyses ...................................................................... 3-11

3.3.1 PM2.5.................................................................................................... 3-12

3.3.2 Visibility............................................................................................... 3-19

3.4 References ...................................................................................................... 3-22

Chapter 4 Control Strategies.................................................................................................. 4-1

4.1 Synopsis............................................................................................................. 4-1

4.2 PM2.5 Control Strategy Analysis........................................................................ 4-2

4.2.1 Establishing the Baseline ...................................................................... 4-2

4.2.2 Alternative Standard Control Strategies............................................... 4-8

4.2.3 Emission Reductions Needed Beyond Identified Controls................. 4-14

4.3 Limitations and Uncertainties......................................................................... 4-16

4.4 References ...................................................................................................... 4-18
v

4.A Additional Control Strategy Information.......................................................4.A-1

Chapter 5 Human Health Benefits Analysis Approach and Results....................................... 5-1

5.1 Synopsis............................................................................................................. 5-1

5.2 Overview ........................................................................................................... 5-2

5.3 Updated Methodology Presented in this RIA................................................... 5-6

5.4 Human Health Benefits Analysis Methods....................................................... 5-8

5.4.1 Health Impact Assessment.................................................................... 5-9

5.4.2 Economic Valuation of Health Impacts............................................... 5-10

5.5 Uncertainty Characterization.......................................................................... 5-12

5.5.1 Monte Carlo Assessment.................................................................... 5-13

5.5.2 Concentration Benchmark Analysis for PM2.5..................................... 5-13

5.5.3 Alternative Concentration-Response Functions for PM2.5 –

Related Mortality ................................................................................ 5-14

5.5.4 Sensitivity Analyses............................................................................. 5-15

5.5.5 Distributional Assessment .................................................................. 5-16

5.5.6 Influence Analysis—Quantitative Assessment of Uncertainty........... 5-16

5.5.7 Qualitative Assessment of Uncertainty and Other Analysis 

Limitations........................................................................................... 5-17

5.6 Benefits Analysis Data Inputs.......................................................................... 5-19

5.6.1 Demographic Data .............................................................................. 5-19

5.6.2 Baseline Incidence and Prevalence Estimates.................................... 5-20

5.6.3 Effect Coefficients............................................................................... 5-24

5.6.4 Unquantified Human Health Benefits................................................. 5-42

5.6.5 Economic Valuation Estimates............................................................ 5-44

5.6.6 Hospital Admissions and Emergency Department Valuation............. 5-57

5.6.7 Minor Restricted Activity Days Valuation........................................... 5-58

5.6.8 Growth in WTP Reflecting National Income Growth Over Time........ 5-59

5.7 Benefits Results............................................................................................... 5-62

5.7.1 Benefits of Attaining Alternative Combinations of Primary PM2.5

Standards............................................................................................ 5-62

5.7.2 Uncertainty in Benefits Results........................................................... 5-63

5.7.3 Estimated Life Years Gained Attributable to Reduced PM2.5 

Exposure and Percent of Total Mortality............................................ 5-74
vi

5.7.4 Analysis of Mortality Impacts at Various Concentration 

Benchmarks......................................................................................... 5-79

5.7.5 Additional Sensitivity Analyses........................................................... 5-85

5.8 Discussion........................................................................................................ 5-86

5.9 References ...................................................................................................... 5-87

5.A Distribution of the PM2.5-Related Benefits....................................................5.A-1

5.B Additional Sensitivity Analyses Related to the Health Benefits Analysis ...... 5.B-1

5.C Qualitative Assessment of Uncertainty ......................................................... 5.C-1

Chapter 6 Welfare Benefits Analysis Approach..................................................................... 6-1

6.1 Important Caveats Regarding this Chapter ...................................................... 6-1

6.2 Synopsis............................................................................................................. 6-1

6.3 Introduction to Welfare Benefits Analysis........................................................ 6-1

6.4 Visibility Benefits............................................................................................... 6-6

6.4.1 Visibility and Light Extinction................................................................ 6-6

6.4.2 Visibility Valuation Overview.............................................................. 6-12

6.4.3 Recreational Visibility ......................................................................... 6-14

6.4.4 Residential Visibility............................................................................ 6-22

6.4.5 Discussion of Visibility Benefits........................................................... 6-29

6.5 Materials Damage Benefits............................................................................. 6-30

6.6 Climate Benefits.............................................................................................. 6-33

6.6.1 Climate Effects of Short Lived Climate Forcers................................... 6-34

6.6.2 Climate Effects of Long-Lived Greenhouse Gases .............................. 6-37

6.7 Ecosystem Benefits and Services.................................................................... 6-37

6.7.1 Ecosystem Benefits for Metallic and Organic Constituents of PM..... 6-40

6.7.2 Ecosystem Benefits from Reductions in Nitrogen and Sulfur 

Emissions............................................................................................. 6-43

6.7.3 Ecosystem Benefits from Reductions in Mercury Emissions.............. 6-61

6.7.4 Vegetation Benefits from Reductions in Ambient Ozone................... 6-64

6.8 References ...................................................................................................... 6-71

6.A Additional Details Regarding the Visibility Benefits Methodology................6.A-1
vii

Chapter 7 Engineering Cost Analysis ..................................................................................... 7-1

7.1 Synopsis............................................................................................................. 7-1

7.2 PM2.5 Engineering Costs.................................................................................... 7-2

7.2.1 Data and Methods—Identified Control Costs (non-EGU Point 

and Area Sources)................................................................................. 7-2

7.2.2 Identified Control Costs........................................................................ 7-3

7.2.3 Extrapolated Costs................................................................................ 7-6

7.2.4 Total Cost Estimates............................................................................ 7-10

7.3 Changes in Regulatory Cost Estimates over Time .......................................... 7-12

7.3.1 Examples of Technological Advances in Pollution Control................. 7-14

7.3.2 Influence on Regulatory Cost Estimates............................................. 7-16

7.3.3 Influence of Regulation on Technological Change ............................. 7-20

7.4 Uncertainties and Limitations......................................................................... 7-21

7.5 References ...................................................................................................... 7-22

7.A Other Extrapolated Cost Approaches............................................................7.A-1

Chapter 8 Comparison of Benefits and Costs........................................................................ 8-1

8.1 Synopsis............................................................................................................. 8-1

8.2 Analysis ............................................................................................................. 8-1

8.3 Conclusions of the Analysis............................................................................... 8-2

8.4 Caveats and Limitations.................................................................................... 8-3

8.4.1 Benefits Caveats.................................................................................... 8-3

8.4.2 Control Strategy and Cost Analysis Caveats and Limitations ............... 8-4

Chapter 9 Statutory and Executive Order Reviews ............................................................... 9-1

9.1 Synopsis............................................................................................................. 9-1

9.2 Executive Order 12866: Regulatory Planning and Review ............................... 9-1

9.3 Paperwork Reduction Act................................................................................. 9-1

9.4 Regulatory Flexibility Act .................................................................................. 9-1

9.5 Unfunded Mandates Reform Act...................................................................... 9-2

9.6 Executive Order 13132: Federalism.................................................................. 9-2
viii

9.7 Executive Order 13175: Consultation and Coordination with Indian 

Tribal Governments.......................................................................................... 9-3

9.8 Executive Order 13045: Protection of Children from Environmental 

Health and Safety Risks..................................................................................... 9-3

9.9 Executive Order 13211: Actions that Significantly Affect Energy Supply, 

Distribution or Use............................................................................................ 9-4

9.10 National Technology Transfer and Advancement Act...................................... 9-4

9.11 Executive Order 12898: Federal Actions to Address Environmental 

Justice in Minority Populations and Low-Income Populations ........................ 9-6

Chapter 10 Secondary Standards Analysis........................................................................... 10-1

10.1 Introduction .................................................................................................... 10-1

10.2 The Secondary NAAQS Standard .................................................................... 10-1

10.3 Visibility Benefits from PM Reduction............................................................ 10-2

10.4 Baseline Modeling Projection Data (2020)..................................................... 10-3

10.5 Impacts of Attaining a Distinct Secondary Standard ...................................... 10-5

10.6 Limitations of Analysis.................................................................................... 10-5

10.7 References ...................................................................................................... 10-6

10.A 2017 Modeled Design Values by State, County, and Site............................10.A-1

Chapter 11 Qualitative Discussion of Employment Impacts of Air Quality Regulations..... 11-1

11.1 Introduction .................................................................................................... 11-1

11.2 Influence of NAAQS Controls on Employment............................................... 11-1

11.3 The Current State of Knowledge Based on the Peer-Reviewed Literature .... 11-3

11.3.1 Immediate and Short-Run Employment Impacts............................... 11-3

11.3.2 Long-Term Employment Impacts on the Regulated Industry............. 11-4

11.4 Conclusion....................................................................................................... 11-7

11.5 References ...................................................................................................... 11-7
ix

LIST OF FIGURES

Number Page

2-1. Detailed Source Categorization of Anthropogenic Emissions of Primary PM2.5, 

PM10 and Gaseous Precursor Species SO2, NOx, NH3 and VOCs for 2002 in Units of 

Million Metric Tons (MMT). EGUs = Electricity Generating Units................................... 2-3

2-2. Regional and Local Contributions to Annual Average PM2.5 by Particulate SO4

2–

, 

Nitrate and Total Carbon (i.e., organic plus EC) for Select Urban Areas Based on 

Paired 2000-2004 IMPROVE and CSN Monitoring Sites.................................................. 2-5

2-3. Regional and Seasonal Trends in Annual PM2.5 Composition from 2002 to 2007 

Derived Using the SANDWICH Method. Data from the 42 monitoring locations 

shown on the map were stratified by region and season including cool months 

(October–April) and warm months (May–September)................................................... 2-6

2-4. RCFM (left) versus SANDWICH (right) Pie Charts Comparing the Ambient and 

PM2.5 FRM Reconstructed Mass Protocols on an Annual Average Basis......................... 2-8

2-5. Maximum County-level PM2.5 Annual Design Values Calculated Using 2003–2007 

FRM 24-hr Average PM2.5 Measurements....................................................................... 2-9

2-6. Maximum County-level PM2.5 24-hour Design Values Calculated Using 2003–2007 

FRM 24-hr Average PM2.5 Measurements..................................................................... 2-10

2-7. Important Factors Involved in Seeing a Scenic Vista ..................................................... 2-11

2-8. Visibility in Selected National Parks and Wilderness Areas in the U.S., 1992–2008..... 2-13

2-9. Maximum County-level Visibility Design Values Calculated Using 2004–2006 24-

hr Average Speciated PM2.5 Measured Concentrations................................................ 2-14

3-1. Map of the CMAQ Modeling Domains Used for PM NAAQS RIA .................................... 3-2

3-2. Diagram of Rollback Method ......................................................................................... 3-19

4-1. Counties Projected to Exceed the Baseline and Analysis Levels of the PM2.5

Annual Standard Alternatives in 2020............................................................................. 4-5

4-2. Counties Projected to Exceed the Baseline and Analysis Levels of the PM2.5 

24-hour Standard Alternatives in 2020 ........................................................................... 4-6

4-3. Counties Projected to Exceed the 12/35 ug/m3 Alternative Standard After 

Meeting the Baseline (Current Standard) in 2020........................................................... 4-9

4-4. Counties Projected to Exceed the 11/35 ug/m3 Alternative Standard After 

Meeting the Baseline (Current Standard) in 2020......................................................... 4-10

4-5. Counties Projected to Exceed the 11/30 ug/m3 Alternative Standard After 

Meeting the Baseline (Current Standard) in 2020......................................................... 4-11

5-1. Illustration of BenMAP Approach .................................................................................. 5-10

5-2. Data Inputs and Outputs for the BenMAP Model ......................................................... 5-11

5-3. Estimated PM2.5-Related Premature Mortalities Avoided According to 

Epidemiology or Expert-Derived PM2.5 Mortality Risk Estimate for 12/35 and 

13/35.............................................................................................................................. 5-72
x

5-4. Total Monetized Benefits Using 2 Epidemiology-Derived and 12-Expert Derived 

Relationships Between PM2.5 and Premature Mortality for 12/35 and 13/35 ............. 5-73

5-5a. Distribution of Estimated Avoided Premature Deaths by the Age at which these 

Populations were Exposed in 2020 for 12/35 ............................................................... 5-78

5-5b. Distribution of Estimated Life Years Gained by the Age at which these 

Populations were Exposed in 2020 for 12/35 ............................................................... 5-78

5-6. Number of Premature PM2.5-related Deaths Avoided for 12/35 and 13/35 

According to the Baseline Level of PM2.5 and the Lowest Measured Air Quality 

Levels of Each Mortality Study....................................................................................... 5-84

5-7. Number of Premature PM2.5-related Deaths Avoided for 12/35 According to the 

Baseline Level of PM2.5 and the Lowest Measured Air Quality Levels of Each 

Mortality Study .............................................................................................................. 5-85

5.A-1. PM2.5 Mortality Risk Modified by Educational Attainment in Counties Projected 

to Exceed 12/35 ............................................................................................................5.A-5

5.A-2. PM2.5 Mortality Risk by Race in Counties Projected to Exceed 12/35..........................5.A-6

5.B-1. Alternate Lag Structures for PM2.5 Premature Mortality (Cumulative)........................5.B-8

5.B-2. Exponential Lag Structures for PM2.5 Premature Mortality (Cumulative)....................5.B-8

6-1. Important Factors Involved in Seeing a Scenic Vista (Malm, 1999) ................................ 6-7

6-2. Visibility in Selected National Parks and Wilderness Areas in the U.S., 1992–2008....... 6-9

6-3. Estimated Improvement in Annual Average Visibility Levels Associated with the 

CAAA Provisions in 2020................................................................................................ 6-10

6-4. Mandatory Class I Areas in the U.S................................................................................ 6-15

6-5. Visitation Rates and Park Regions for Class I Areas*..................................................... 6-20

6-6. Residential Visibility Study City Assignment.................................................................. 6-27

6-7. Linkages between Categories of Ecosystem Services and Components of Human 

Well-Being from Millennium Ecosystem Assessment (MEA, 2005) .............................. 6-38

6-8. Schematic of the Benefits Assessment Process (U.S. EPA, 2006c)................................ 6-39

6-9. Schematics of Ecological Effects of Nitrogen and Sulfur Deposition............................. 6-44

6-10. Nitrogen and Sulfur Cycling, and Interactions in the Environment............................... 6-45

6-11. Areas Potentially Sensitive to Aquatic Acidification...................................................... 6-48

6-12. Areas Potentially Sensitive to Terrestrial Acidification.................................................. 6-50

6-13. Distribution of Red Spruce (pink) and Sugar Maple (green) in the Eastern U.S............ 6-51

6-14. Spatial and Biogeochemical Factors Influencing MeHg Production.............................. 6-59

6-15. Preliminary USGS Map of Mercury Methylation–Sensitive Watersheds...................... 6-60

6-16. Visible Foliar Injury to Forest Plants from Ozone in U.S. by EPA Regions..................... 6-68

6-17. Presence and Absence of Visible Foliar Injury, as Measured by U.S. Forest 

Service, 2002.................................................................................................................. 6-69

7-1. Technological Innovation Reflected by Marginal Cost Shift.......................................... 7-13

10-1. Counties with Monitors Included in Analysis ................................................................ 10-4

10-2. Design Values in 2020, Prior to Full Attainment of a Primary Standard of 15/35......... 10-5
xi

LIST OF TABLES

Number Page

ES-1. Emission Reduction Estimates by Standard in 2020 (annual tons/year)....................... ES-5

ES-2. Total Monetized Benefits, Total Costs, and Net Benefits in 2020 (millions of 

2006$)—Full Attainment ............................................................................................... ES-9

ES-3. Regional Breakdown of Total Costs and Monetized Benefits Results......................... ES-10

ES-4. Estimated Number of Avoided PM2.5 Health Impacts for Standard Alternatives—

Full Attainment ............................................................................................................ ES-10

2-1. Annual Average FRM and CSN PM2.5 NO3

– and NH4NO3 Concentrations at Six Sites 

during 2003...................................................................................................................... 2-8

3-1. Geographic Specifications of Modeling Domains............................................................ 3-3

3-2. Control Strategies and Growth Assumptions for Creating 2020 Base Case 

Emissions Inventories from the 2005 Base Case ............................................................. 3-6

3-3. Area Definitions and PM2.5 Air Quality Ratios................................................................ 3-16

4-1. Controls Applied in the Baseline for the Current PM2.5 Standard ................................... 4-8

4-2. Number of Counties with Exceedances and Number of Additional Counties 

Where Reductions were Applied................................................................................... 4-12

4-3. Emission Reductions from Known Controls for Alternative Standards ........................ 4-13

4-4. Emission Reductions Needed Beyond Known Control to Reach Alternative 

Standards in 2020 (annual tons/year) ........................................................................... 4-16

4-5. Summary of Qualitative Uncertainty for Elements of Control Strategies..................... 4-17

4.A-1. Example PM Control Measures for NonEGU Point Source Categories ........................4.A-3

4.A-2. Example PM Control Measures for Area Sources.........................................................4.A-4

4.A-3. Example SO2 Control Measures for NonEGU Point ......................................................4.A-5

4.A-4. Example NOx Control Measures for NonEGU Source Categories.................................4.A-7

4.A-5. Area County Definitions for SO2 and NOx Emissions Reductions for Control 

Strategy Analysis...........................................................................................................4.A-7

4.A-6. Air Quality Ratios for Monitors in Counties with at Least One Monitor with an 

Annual Design Value (DV) Above 15 or 24-hr Design Value (DV) Above 35 in 2020 

Base Case ....................................................................................................................4.A-14

4.A-7. Air Quality Ratios for Monitors in Counties With at Least One Monitor With an 

Annual Design Value (DV) Above 13 in 2020 Baseline (15/35) ..................................4.A-18

4.A-8. Air Quality Ratios for Monitors in Counties with at Least One Monitor With an 

Annual Design Value (DV) Above 12 in 2020 Baseline (15/35) ..................................4.A-19

4.A-9. Air Quality Ratios for Monitors in Counties With at Least One Monitor With an 

Annual Design Value (DV) Above 11 in 2020 Baseline (15/35) ..................................4.A-21

4.A-10.Air Quality Ratios for Monitors in Counties with at Least One Monitor with an 

Annual Design Value (DV) Above 11 or 24-hr Design Value (DV) Above 30 in 2020 

Baseline (15/35)..........................................................................................................4.A-23
xii

4.A-11.Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35), 

2020 12/35 and 2020 11/35 .......................................................................................4.A-27

4.A-12.24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30...........................................................................................................4.A-71

5-1. Estimated Monetized Benefits of the Proposed and Alternative Combinations of 

PM2.5 Standards in 2020, Incremental to Attainment of 15/35 (millions of 2006$)....... 5-1

5-2. Human Health Effects of Pollutants Potentially Affected by Attainment of the 

Primary PM2.5 Standards.................................................................................................. 5-4

5-3. Baseline Incidence Rates and Population Prevalence Rates for Use in Impact 

Functions, General Population ...................................................................................... 5-22

5-4. Asthma Prevalence Rates .............................................................................................. 5-23

5-5. Criteria Used When Selecting C-R Functions................................................................. 5-26

5-6. Health Endpoints and Epidemiological Studies Used to Quantify Health Impacts 

in the Main Analysis....................................................................................................... 5-27

5-7. Health Endpoints and Epidemiological Studies Used to Quantify Health Impacts 

in the Sensitivity Analysis .............................................................................................. 5-28

5-8. Summary of Effect estimates from Associated With Change in Long-Term 

Exposure to PM2.5 in Recent Cohort Studies in North America ..................................... 5-34

5-9. Unit Values for Economic Valuation of Health Endpoints (2006$)................................ 5-46

5-10. Influence of Applied VSL Attributes on the Size of the Economic Benefits of 

Reductions in the Risk of Premature Death (U.S. EPA, 2006a)...................................... 5-52

5-11. Alternative Direct Medical Cost of Illness Estimates for Nonfatal Heart Attacks ......... 5-56

5-12. Estimated Costs Over a 5-Year Period of a Nonfatal Myocardial Infarction (in 

2006$) ............................................................................................................................ 5-57

5-13. Unit Values for Hospital Admissions.............................................................................. 5-58

5-14. Elasticity Values Used to Account for Projected Real Income Growth ......................... 5-60

5-15. Adjustment Factors Used to Account for Projected Real Income Growth.................... 5-62

5-16. Population-Weighted Air Quality Change for Adults (30+) for Alternative 

Standards Relative to 15/35 .......................................................................................... 5-63

5-17. Estimated number of Avoided PM2.5 Health Impacts for Alternative Combinations 

of Primary PM2.5 Standards (Incremental to Attaining Current Suite of Primary 

PM2.5 Standards)............................................................................................................. 5-65

5-18. Estimated Number of Avoided PM2.5-Related Deaths for Alternative 

Combinations of Primary PM2.5 Standards (Incremental to Attaining Current Suite 

of Primary PM2.5 Standards)........................................................................................... 5-66

5-19. Estimated Monetized PM2.5 Health Impacts for Alternative Combinations of 

Primary PM2.5 Standards (Incremental to Attaining Current Suite of Primary PM2.5 

Standards) (Millions of 2006$, 3% discount rate) ......................................................... 5-67

5-20. Estimated Monetized PM2.5 Health Impacts for Alternative Combinations of 

Primary PM2.5 Standards (Incremental to Attaining Current Suite of Primary PM2.5 

Standards) (Millions of 2006$, 7% discount rate) ......................................................... 5-68
xiii

5-21. Estimated Monetized PM2.5-Related Deaths for Alternative Combinations of 

Primary PM2.5 Standards (Incremental to Attaining Current Suite of Primary PM2.5 

Standards)(Millions of 2006$, 3% discount rate) .......................................................... 5-69

5-22. Estimated Monetized PM2.5-Related Deaths for Alternative Combinations of 

Primary PM2.5 Standards (Incremental to Attaining Current Suite of Primary PM2.5 

Standards) (Millions of 2006$, 7% discount rate) ......................................................... 5-70

5-23. Total Estimated Monetized Benefits of the for Alternative Combinations of 

Primary PM2.5 Standards (Incremental to Attaining Current Suite of Primary PM2.5 

Standards) (millions of 2006$)....................................................................................... 5-71

5-24. Regional Breakdown of Monetized Benefits Results..................................................... 5-71

5-25. Sum of Life Years Gained by Age Range from Changes in PM2.5 Exposure in 2020 

for 12/35 ........................................................................................................................ 5-77

5-26. Estimated Reduction the Percentage of All-Cause Mortality Attributable to PM2.5 

for 12/35 from Changes in PM2.5 Exposure in 2020....................................................... 5-79

5-27. Estimated Reduction in Incidence of Adult Premature Mortality Occurring Above 

and Below the Lowest Measured Levels in the Underlying Epidemiology Studies 

for 12/35 and 13/35....................................................................................................... 5-82

5-28. Percentage of Avoided Premature Deaths Occurring At or Above the Lowest 

Measured Levels in the Underlying Epidemiology Studies for each Alternative 

Combination of Primary PM2.5 Standards...................................................................... 5-83

5.A-1. Key Attributes of the Distributional Analyses in this Appendix....................................5.A-3

5.A-2. Numerical Values Used for Figures 5.A-1 and 5.A-2 Above..........................................5.A-6

5.B-1. Values of the Time Constant (k) for the Exponential Decay Lag Function ...................5.B-6

5.B-2. Sensitivity of Monetized PM2.5-Related Premature Mortality Benefits to 

Alternative Cessation Lag Structures, Using Effect Estimate from Krewski et al. 

(2009)............................................................................................................................5.B-7

5.B-3. Ranges of Elasticity Values Used to Account for Projected Real Income Growth........5.B-9

5.B-4. Ranges of Adjustment Factors Used to Account for Projected Real Income 

Growth ..........................................................................................................................5.B-9

5.B-5. Sensitivity of Monetized Benefits to Alternative Income Elasticities...........................5.B-9

5.B-6. Avoided Cases of Cardiovascular Emergency Department Visits, Stroke and 

Chronic Bronchitis in 2020 (95th percentile confidence intervals) .............................5.B-11

5.B-7. Unit Values for Hospital Admissions in BenMAP 4.0.51 (Abt Associates, 2011)........5.B-12

5.B-8. Unit Values for Hospital Admissions in BenMAP 4.0.43 (Abt Associates, 2010)........5.B-12

5.B-9. Change in Monetized Hospitalization Benefits for 12/35 ..........................................5.B-12

5.B-10. Summary of Effect Estimates From Associated With Change in Long-Term 

Exposure to PM2.5 in Recent Cohort Studies in California ..........................................5.B-14

5.C-1. Summary of Qualitative Uncertainty for Key Modeling Elements in PM2.5 Benefits....5.C-4

6-1. Welfare Effects by Pollutants Potentially Affected by Attainment of the PM 

NAAQS.............................................................................................................................. 6-3

6-2. Quantified and Unquantified Welfare Benefits............................................................... 6-4

6-3. Key Assumptions in the Light Extinction Estimates Affecting the Visibility Benefits 

Analysis .......................................................................................................................... 6-12

6-4. WTP for Visibility Improvements in Class I Areas in Non-Studied Park Regions........... 6-20
xiv

6-5. Summary of Key Assumptions in the Recreational Visibility Benefits........................... 6-21

6-6. Summary of Residential Visibility Valuation Estimates................................................. 6-25

6-7. Summary of Key Assumptions in the Residential Visibility Benefits ............................. 6-28

6-8. Materials Damaged by Pollutants Affected by this Rule (U.S. EPA, 2011b).................. 6-33

6-9. Aquatic Status Categories.............................................................................................. 6-47

6.A-1. Available Information on WTP for Visibility Improvements in National Parks.............6.A-8

6.A-2. Summary of Region-Specific Recreational Visibility Parameters to be Estimated in 

Household Utility Functions..........................................................................................6.A-9

6.A-3. Mean Annual Household WTP for Changes in Visual Range for Recreational 

Visibility (1990$) .........................................................................................................6.A-21

6.A-4. Region-Specific Parameters for Recreational Visibility Benefits................................6.A-21

6.A-5. Mean Annual Household WTP for Changes in Visual Range for Residential 

Visibility.......................................................................................................................6.A-22

6.A-6. Parameters for Income Growth Adjustment for Visibility Benefits............................6.A-23

7-1. Summary of Sectors, Control Costs, and Discount Rates for Known Control Costs 

(millions of 2006$) ........................................................................................................... 7-4

7-2. Partial Attainment Known Control Costs in 2020 for Alternative Standards 

Analyzed (millions of 2006$)............................................................................................ 7-5

7-3. Fixed Costs by Alternative Standard Analyzed (millions of 2006$)............................... 7-10

7-4. Total Costs by Alternative Standard Analyzed (millions of 2006$) ............................... 7-12

7-5. Phase 2 Cost Estimates.................................................................................................. 7-18

7-6. Comparison of Inflation-Adjusted Estimated Costs and Actual Price Changes of 

EPA Fuel Control Rules................................................................................................... 7-19

7-7. Summary of Qualitative Uncertainty for Modeling Elements of PM Engineering 

Costs............................................................................................................................... 7-21

7.A-1. Extrapolated Costs by Alternative Standard Analyzed (millions of 2006$)..................7.A-3

7.A-2. Sensitivity Analysis of Fixed-Cost Approach for Unknown Controls by Alternative 

Standard Analyzed (millions of 2006$).........................................................................7.A-7

7.A-3. Sensitivity Analysis of Alternative Hybrid Approach for Unknown Controls by 

Alternative Standard Analyzed (millions of 2006$)......................................................7.A-8

8-1. Total Monetized Benefits, Total Costs, and Net Benefits in 2020 (millions of 

2006$)—Full Attainment ................................................................................................. 8-2

8-2. Estimated Number of Avoided PM2.5 Health Impacts for Standard Alternatives—

Full Attainment ................................................................................................................ 8-3

10-1. Percentage of Monitors Projected to Exceed Alternative Secondary Standards in 

2020, Prior to Attainment of Primary Standard of 15/35.............................................. 10-4

10.A-1.2017 Modeled Design Values by State, County, and Site...........................................10.A-1
ES-1

EXECUTIVE SUMMARY

ES.1 Overview

Based on its review of the air quality criteria and the national ambient air quality 

standards (NAAQS) for particulate matter (PM), the U.S. Environmental Protection Agency (EPA) 

is proposing to revise the primary (health-based) and secondary (welfare-based) NAAQS for fine 

particles (generally referring to particles less than or equal to 2.5 micrometers [μm] in 

diameter—PM2.5) to provide requisite protection of public health and welfare, respectively. As 

has traditionally been done in NAAQS rulemakings, the EPA has conducted a Regulatory Impact 

Analysis (RIA) to provide the public with illustrative estimates of the potential costs and health 

and welfare benefits of attaining several alternative PM2.5 standards based on one possible set 

of selected control strategies for reducing direct PM and PM precursor emissions.

In NAAQS rulemakings, the RIA is prepared for informational purposes only, and the 

proposed decisions on the PM NAAQS discussed in the proposed rulemaking are not in any way 

based on consideration of the information or analyses in the RIA. The RIA fulfills the 

requirements of Executive Orders 12866 and 13563 and guidelines of the Office of 

Management and Budget’s (OMB) Circular A-4.1 Benefit and cost estimates provided in the RIA 

are not additive to benefits and costs from other regulations, and the costs and benefits 

identified in this RIA will not be realized until specific controls are mandated by State 

Implementation Plans (SIPs) or other federal regulations.

ES.2 Existing and Alternative PM Air Quality Standards

Currently, two primary PM2.5 standards provide public health protection from effects 

associated with fine particle exposures: the annual standard and the 24-hour standard. The 

annual standard is set at a level of 15.0 μg/m3, based on the 3-year average of annual 

arithmetic mean PM2.5 concentrations. The 24-hour standard is set at a level of 35 μg/m3

, based 

on the 3-year average of the 98th percentile of 24-hour PM2.5 concentration. In the RIA, the 

current primary PM2.5 standard, including both annual and 24-hour averaging times is denoted 

as 15/35.

In the current PM NAAQS review, the EPA is proposing to revise the level of the primary 

annual PM2.5 standard within the range of 12 to 13 μg/m3 in conjunction with retaining the level 

of the 24-hour standard at 35 μg/m3. In order to characterize the costs and benefits, it was 

 1 U.S. Office of Management and Budget. Circular A-4, September 17, 2003. Available at 

http://www.whitehouse.gov/omb/circulars/a004/a-4.pdf.
ES-2

necessary to identify discrete levels along this continuum. For purposes of this analysis, we 

identified an annual standard of 12 μg/m3 in conjunction with retaining the level of the 24-hour 

standard at 35 μg/m3 (denoted 12/35) and an annual standard of 13 μg/m3 in conjunction with 

retaining the level of the 24-hour standard at 35 μg/m3 (denoted as and 13/35).

In addition to 12/35 and 13/35, the RIA also analyzes the benefits and costs of 

incremental control strategies for two other alternative standards (11/35 and 11/30). The four 

alternative standards analyzed are as follows:

 A revised annual standard level of 13 μg/m3 in conjunction with retaining the 

24-hour standard level at 35 μg/m3 (13/35)

 A revised annual standard level of 12 μg/m3 in conjunction with retaining the 

24-hour standard level at 35 μg/m3 (12/35)

 A revised annual standard level of 11 μg/m3 in conjunction with retaining the 

24-hour standard level at 35 μg/m3 (11/35 )

 A revised annual standard level of 11 μg/m3 in conjunction with a revised 24-hour 

standard level at 30 μg/m3 (11/30 )

In analyzing the current 15/35 standard (baseline), the EPA determined that all counties 

would meet the 14/35 standard concurrently with meeting the existing 15/35 standard at no 

additional cost. Consequently, no incremental costs or benefits are associated with 14/35 and 

therefore, no need to present an analysis of 14/35 in this RIA.

Currently, the existing secondary PM2.5 standards are identical in all respects to the 

primary standards. In the current PM NAAQS review, the EPA is proposing to add a distinct 

standard for PM2.5 to provide protection from PM-related visibility impairment. Specifically, the 

EPA is proposing to establish a separate secondary standard defined in terms of a PM2.5

visibility index, which would use speciated PM2.5 mass concentrations and relative humidity 

data to calculate PM2.5 light extinction, similar to the Regional Haze Program; a 24-hour 

averaging time; a 90th percentile form; and a level of either 30 deciviews (dv) or 28 dv. Based 

on the air quality analysis conducted for the primary PM2.5 standard, all monitored areas are 

estimated to be in attainment with both proposed secondary standard levels in 2020, assuming 

full attainment of the primary PM2.5 standard. For the two optional levels proposed for the 

secondary standard, no additional costs or benefits will be realized beyond those quantified for 

meeting the primary PM2.5 standard in this RIA.
ES-3

With regard to the primary and secondary standards for particles less than or equal to 

10 μm in diameter (PM10), the EPA is proposing to retain the current primary and secondary 

24-hour PM10 standards. Both standards are the same. The current primary and secondary 24-

hour standards are set at a level of 150 μg/m3, not to be exceeded more than once per year on 

average over 3 years (EPA, 1997)2. Since the benefit-cost analysis of the alternative PM10 

standards was conducted when the standard was selected, this RIA does not repeat that 

analysis here.

ES.2.1 Establishing the Baseline

The RIA is intended to evaluate the costs and benefits of reaching attainment with 

potential alternative PM2.5 standards. In order to develop and evaluate control strategies for 

attaining a more stringent primary standard, it is important to first estimate PM2.5 levels in 2020 

given the current NAAQS standards (15/35) and air quality trends. Estimating the 2020 levels is 

known as the baseline. Establishing this baseline allows us to estimate the incremental costs 

and benefits of attaining any alternative primary standard.

The baseline includes reductions already achieved as a result of national regulations, 

reductions expected prior to 2020 from recently promulgated national regulations3 (i.e., 

reductions that were not realized before 2005 but are expected prior to attainment of the 

current PM standard), and reductions from additional controls which the EPA estimates need to 

be included to attain the current standard (15/35). Reductions achieved as a result of state and 

local agency regulations and voluntary programs are reflected to the extent that they are 

represented in emission inventory information submitted to the EPA by state and local 

agencies4. Two steps were used to develop the baseline. First, the reductions expected in 

national PM2.5 concentrations from national rules promulgated prior to this analysis were 

considered (referred to as the base case). Below is a list of some of the major national rules 

reflected in the base case. Refer to Chapter 3, Section 3.2.2 for a more detailed discussion of 

the rules reflected in the base case emissions inventory.

 Light-Duty Vehicle Tier 2 Rule (U.S. EPA, 1999)

 2 U.S. Environmental Protection Agency. 1997. Regulatory Impact Analyses for the Particulate Matter and Ozone 

National Ambient Air Quality Standards and Proposed Regional Haze Rule. Available at: 

http://www.epa.gov/ttn/oarpg/naaqsfin/ria.html. 3 The recently proposed Boiler MACT and CISWI reconsiderations are not included in the base case. These rules 

were not yet proposed at the time of this analysis. It is not clear how the geographic scope of this rule will 

match with the counties analyzed for this RIA—the costs may decrease but the magnitude is uncertain. 4 The amendments to the Low Emissions Vehicle Program (LEV-III) in California are not included in the base case. 

This program requires an approval of U.S. EPA via a waiver. At the time of this analysis the waiver had not been 

submitted.
ES-4

 Heavy Duty Diesel Rule (U.S. EPA, 2000)

 Clean Air Nonroad Diesel Rule (U.S. EPA, 2004)

 Regional Haze Regulations and Guidelines for Best Available Retrofit Technology 

Determinations (U.S. EPA, 2005b)

 NOx Emissions Standard for New Commercial Aircraft Engines (U.S. EPA, 2005)

 Emissions Standards for Locomotives and Marine Compression-Ignition Engines (U.S. 

EPA, 2008)

 Control of Emissions for Nonroad Spark Ignition Engines and Equipment (U.S. EPA, 

2008)

 C3 Oceangoing Vessels (U.S. EPA, 2010)

 Hospital/Medical/Infectious Waste Incinerators: New Source Performance Standards 

and Emission Guidelines: Final Rule Amendments (U.S. EPA, 2009)

 Cross-State Air Pollution Rule (U.S. EPA, 2011a)

 Mercury and Air Toxics Standards (U.S. EPA, 2011b)

 Reciprocating Internal Combustion Engines (RICE) NESHAPs (U.S. EPA, 2010)

We did not conduct this analysis incremental to controls applied as part of previous 

NAAQS analyses (e.g., O3, NOx, or SO2) because the data and modeling on which these previous 

analyses were based are now considered outdated and are not compatible with the current 

PM2.5 NAAQS analysis. In addition, all control strategies analyzed in NAAQS RIAs are 

hypothetical. This analysis presents one scenario that states may employ but does not prescribe 

how attainment must be achieved.

Second, because the base case reductions alone were not predicted to bring all areas 

into attainment with the current standard (15/35), please see Figures 4-1 and 4-2 in Chapter 4 

of this RIA, the EPA used a hypothetical control strategy to apply additional known controls to 

illustrate attainment with that standard. To establish the baseline, additional control measures 

were used in two sectors:5 Non-Electricity Generating Unit Point Sources (Non-EGUs) and NonPoint Area Sources (Area).

 5 In establishing the baseline, the EPA selected a set of cost-effective controls to simulate attainment of the current 

PM2.5 standard. These control sets are hypothetical because states will ultimately determine controls as part of 

the SIP process.
ES-5

For addition details on the baseline, refer to Chapter 4 of this RIA.

ES.2.2 Emission Reduction Estimates by Alternative Standards (2020)

Emission reductions were calculated for the four alternative standards (13/35, 12/35, 

11/35, and 11/30) from a baseline of attaining the current standard of 15/35. Emission 

reductions were calculated for the known control strategy analysis and the extrapolated cost 

analysis for each alternative standard being analyzed. The EPA estimates the national-scale 

emission reductions for each of the alternative standards as shown in Table ES-1.

Table ES-1. Emission Reduction Estimates by Standard in 2020 (annual tons/year)a

Alternative Standard PM2.5 SO2 NOx

13/35 190 0 0

12/35 4,300 970 0

11/35 14,000 19,000 1,500

11/30 22,000 23,000 8,200

a Estimates are rounded to two significant figures.

ES.2.3 Health and Welfare Benefits Analysis Approach

The EPA estimated human health (e.g., mortality and morbidity effects) under full 

attainment of the three alternative combinations of primary PM2.5 standards. We considered an 

array of health impacts attributable to changes in PM2.5 exposure. The EPA has incorporated an 

array of policy and technical updates to the benefits analysis approach applied in this RIA, 

including incorporation of the most recent follow-up to the American Cancer Society (ACS) 

cohort (Krewski et al., 2009), updated health endpoints, new morbidity studies, updated 

hospital cost-of-illness estimates, and an expanded uncertainty assessment. Each of these 

updates is fully described in the benefits chapter. Even though the alternative primary 

standards are designed to protect against adverse effects to human health, the emission 

reductions have welfare co-benefits in addition to the direct human health benefits. The term 

welfare co-benefits covers both environmental and societal benefits of reducing pollution, such 

as reductions in visibility impairment, materials damage, and ecosystem damage. Despite our 

attempts to quantify and monetize as many of the benefits as possible, welfare benefits are not 

quantified or monetized in this analysis. Unquantified health benefits are discussed in Chapter 

5, and unquantified welfare benefits are discussed in Chapter 6.

It is important to note that estimates of the health benefits from reduced PM2.5 

exposure reported here contain uncertainty, including from the following key assumptions:
ES-6

1. We assumed that all fine particles, regardless of their chemical composition, are 

equally potent in causing premature mortality. This assumption is an important 

assumption, because PM2.5 varies considerably in composition across sources, but 

the scientific evidence is not yet sufficient to allow differentiation of effects 

estimates by particle type.

2. We assumed that the health impact function for fine particles is linear within the 

range of ambient concentrations under consideration. Thus, the estimates include 

health benefits from reducing fine particles in areas with varied concentrations of 

PM2.5, including both regions that are in attainment with the fine particle standard 

and those that do not meet the standard down to the lowest modeled 

concentrations.

As noted in the preamble to the proposed rule, the Policy Assessment (U.S. EPA, 2011c) 

concludes that the range from the 25th to 10th percentiles of the air quality data used the 

epidemiology studies is a reasonable range below which we have appreciably less confidence in 

the associations observed in the epidemiological studies. In the RIA accompanying the 

promulgated PM NAAQS, EPA will characterize the distribution of estimated PM-related health 

benefits attributable to PM reductions occurring above and below the selected standard. For 

12/35, we estimate that 51% and 92% of the estimated avoided premature deaths occur at or 

above an annual mean PM2.5 level of 10 μg/m3 (the lowest measured level (LML) of the Laden et 

al. 2006 study) and 5.8 μg/m3 (the LML of the Krewski et al. 2009 study), respectively. For 13/35, 

these estimates are 62% and 89%. These are the two source studies for the concentrationresponse functions used to estimate mortality benefits. The EPA briefly describes the 

uncertainties in the concentration-response functions below and in considerably more detail in 

the benefits chapter of this RIA.

Although these concentration benchmark analyses (e.g., 25th percentile, 10th percentile, 

and LML) provide some insight into the level of uncertainty in the estimated PM2.5 mortality 

benefits, EPA does not view these concentration benchmarks as a concentration threshold. The 

best estimate of benefits includes estimates below and above these concentration benchmarks, 

but uncertainty is higher in health benefits estimated at lower concentrations, with the lowest 

confidence below the LML. Estimated health impacts reflecting air quality improvements both 

below and above these concentration benchmarks are appropriately included in the total 

benefits estimate. In other words, our increased confidence in the estimated benefits above 

these concentration benchmarks should not imply an absence of confidence in the benefits 

estimated below these concentration benchmarks.
ES-7

It is important to note that these estimated benefits reflect specific control measures 

and emission reductions that are needed to lower PM2.5 concentrations for monitors projected 

to exceed the alternative standard analyzed. The result is that air quality will improve in 

counties that exceed the alternative standards as well as surrounding areas that do not exceed 

the alternative standards. It is not possible to apply controls that only reduce PM2.5 at the 

monitor without affecting surrounding areas. In order to make a direct comparison between 

the benefits and costs of these control strategies, it is appropriate to include all the benefits 

occurring as a result of the control strategies applied.

We estimate benefits using modeled air quality data with 12km grid cells, which is 

important because the grid cells are smaller than counties and PM2.5 concentrations vary 

spatially within a county. Some grid cells in a county can be below the level of the alternative 

standard even though the highest monitor value is above the alternative standard. Thus, 

emission reductions lead to benefits in grid cells that are below the alternative standards even 

within a county with a monitor that exceeds the alternative standard. We have not estimated 

the fraction of benefits that occur only in counties that exceed the alternative standards.

ES.2.4 Cost Analysis Approach

The EPA estimated total costs under partial and full attainment of the alternative PM2.5

standards. The engineering costs generally include the costs of purchasing, installing, and 

operating the referenced control technologies. The technologies and control strategies selected 

for analysis are illustrative of one way in which nonattainment areas could meet a revised 

standard. There are numerous ways to construct and evaluate potential control programs that 

would bring areas into attainment with alternative standards, and the EPA anticipates that 

state and local governments will consider programs that are best suited for local conditions.

The partial-attainment cost analysis reflects the costs associated with applying known 

controls. Costs for full attainment include estimates for the engineering costs of the additional 

tons of emissions reductions that are needed beyond identified controls, referred to as 

extrapolated costs. The EPA recognizes that the extrapolated portion of the engineering cost 

estimates reflects substantial uncertainty about which sectors and which technologies might 

become available for cost-effective application in the future.

ES.2.5 Comparison of Benefits and Costs

In the analysis, we estimate the net benefits of the proposed range of annual PM2.5

standards of 12/35 to 13/35. For 12/35, net benefits are estimated to be $2.3 billion to $5.9 

billion at a 3% discount rate and $2.0 billion to $5.3 billion at a 7% discount rate in 2020 (2006 
ES-8

dollars).6 For 13/35, net benefits are estimated to be $85 million to $220 million at the 3% 

discount rate and $76 million to $200 million at the 7% discount rate.

The EPA estimated the net benefits of the alternative annual PM2.5 standard of 11/35 to 

be $8.9 billion to $23 billion at a 3% discount rate and $8.0 billion to $21 billion at a 7% 

discount rate in 2020. The EPA estimated the net benefits of the alternative annual PM2.5

standard of 11/30 to be $14 billion to $36 billion at a 3% discount rate and $13 billion to $33 

billion at a 7% discount rate in 2020. All estimates are in 2006$.7

In analyzing the current 15/35 standard (baseline), the EPA determined that all counties 

would meet the 14/35 standard concurrently with meeting the existing 15/35 standard at no 

additional cost. No incremental costs or benefits are associated with 14/35 and consequently, 

there is no analysis 14/35 in this RIA.

We provide these results in Table ES-2 and a regional percentage breakdown of costs 

and benefits in Table ES-3. In Table ES-4, we provide the avoided health incidences associated 

with these standard levels.

ES.2.6 Conclusions of the Analysis

The EPA’s illustrative analysis has estimated the health and welfare benefits and costs 

associated with the proposed revised PM NAAQS. The results for 2020 suggest there will be 

significant health and welfare benefits and these benefits will outweigh the costs associated 

with the illustrative control strategies in 2020.

 6 Using a 2010$ year increases estimated costs and benefits by approximately 8%. Because of data limitations, we 

were unable to discount compliance costs for all sectors at 3%. As a result, the net benefit calculations at 3% 

were computed by subtracting the costs at 7% from the monetized benefits at 3%. 7 Using a 2010 $ year increases estimated costs and benefits by approximately 8%. Because of data limitations, we 

were unable to discount compliance costs for all sectors at 3%. As a result, the net benefit calculations at 3% 

were computed by subtracting the costs at 7% from monetized benefits at 3%.
ES-9

Table ES-2. Total Monetized Benefits, Total Costs, and Net Benefits in 2020 (millions of 

2006$a)—Full Attainment

Alternative 

Standard

Total Costs Monetized Benefitsb Net Benefitsb

3% Discount 

Ratec

7% Discount 

Rate

3% Discount 

Rate

7% Discount 

Rate

3% Discount 

Ratec

7% Discount 

Rate

13/35 $2.9 $2.9 $88 to $220 $79 to $200 $85 to $220 $76 to $200

12/35 $69 $69 $2,300 to 

$5,900

$2,100 to 

$5,400

$2,300 to 

$5,900

$2,000 to 

$5,300

11/35 $270 $270 $9,200 to 

$23,000

$8,300 to 

$21,000

$8,900 to 

$23,000

$8,000 to 

$21,000

11/30 $390 $390 $14,000 to 

$36,000

$13,000 to 

$33,000

$14,000 to 

$36,000

$13,000 to 

$33,000

a Rounded to two significant figures. Using a 2010$ year increases estimated costs and benefits by approximately 

8%.

b The reduction in premature deaths each year accounts for over 98% of total monetized benefits. Mortality risk

valuation assumes discounting over the Science Advisory Board-recommended 20-year segmented lag structure. 

Not all possible benefits or disbenefits are quantified and monetized in this analysis. B is the sum of all 

unquantified benefits. Data limitations prevented us from quantifying these endpoints, and as such, these 

benefits are inherently more uncertain than those benefits that we were able to quantify.

c Due to data limitations, we were unable to discount compliance costs for all sectors at 3%. As a result, the net 

benefit calculations at 3% were computed by subtracting the costs at 7% from monetized benefits at 3%.

For the lower end of the proposed standard range of 12/35, the EPA estimates that the 

benefits of full attainment exceed the costs of full attainment by 34 to 86 times at a 3% 

discount rate and 30 to 78 times at a 7% discount rate. For the upper end of the proposed 

standard range of 13/35, the EPA estimates that the benefits of full attainment exceed the 

costs of full attainment by 30 to 77 times at a 3% discount rate and 27 to 69 times at a 7% 

discount rate. For the alternative standards, 11/35 and 11/30, the EPA estimates that the 

benefits of full attainment exceed the costs of full attainment by 34 to 94 times at a 3% 

discount rate and 30 to 85 times at a 7% discount rate.
ES-10

Table ES-3. Regional Breakdown of Total Costs and Monetized Benefits Results

Alternative Combination of Standards

13 μg/m3 annual

&

35 μg/m3 24-hour

12 μg/m3 Annual

& 

35 μg/m3 24-hr

11 μg/m3 Annual

&

35 μg/m3 24-hr

11 μg/m3 Annual

&

30 μg/m3 24-hr

Region

Total 

Costsa

Monetized 

Benefits

Total 

Costs

Monetized 

Benefits

Total 

Costs

Monetized 

Benefits

Total 

Costs

Monetized 

Benefits

Eastb

0% 0% <1% 27% 18% 53% 18% 43%

California 100% 98% 94% 70% 67% 44% 54% 47%

Rest of West 0% 2% 5% 3% 15% 3% 28% 10%

a Costs are discounted at 7%.

b Includes Texas and those states to the north and east. Several recent rules such as MATS and CSAPR will have 

substantially reduced PM2.5 levels by 2020 in the East, thus few additional controls would be needed to reach 

12/35 or 13/35.

Table ES-4. Estimated Number of Avoided PM2.5 Health Impacts for Standard Alternatives—

Full Attainmenta

Health Effect

Alternative Combination of Primary PM2.5 Standards

13/35 12/35 11/35 11/30

Adult Mortality 

Krewski et al. (2009) 11 280 1,100 1,700

Laden et al. (2006) (adult) 27 730 2,900 4,500

Woodruff et al. (1997) (infant) 0 1 3 4

Non-fatal heart attacks (age > 18)

Peters et al. (2001) 11 320 1,300 1,900

Pooled estimate of 4 studies 1 35 140 210

Hospital admissions—respiratory (all ages) 3 98 430 620

Hospital admissions—cardiovascular (age > 18) 3 95 400 580

Emergency department visits for asthma (age < 18) 6 160 730 1,000

Acute bronchitis (age 8–12) 22 540 2,000 3,100

Lower respiratory symptoms (age 7–14) 290 6,900 25,000 39,000

Upper respiratory symptoms (asthmatics age 9–11) 410 9,800 37,000 56,000

Asthma exacerbation (age 6–18) 410 24,000 89,000 140,000

Lost work days (age 18–65) 1,800 44,000 170,000 260,000

Minor restricted-activity days (age 18–65) 11,000 260,000 1,000,000 1,500,000

a Incidence estimates are rounded to whole numbers with no more than two significant figures.
ES-11

ES.3 Caveats and Limitations

EPA acknowledges several important limitations of the primary and secondary analysis. 

These include:

ES.3.1 Benefits Caveats

 PM2.5 mortality co-benefits represent a substantial proportion of total monetized 

benefits (over 98%). To characterize the uncertainty in the relationship between 

PM2.5 and premature mortality, we include a set of twelve estimates of the 

concentration-response function based on results of the PM2.5 mortality expert 

elicitation study in addition to our core estimates. Even these multiple 

characterizations omit the uncertainty in air quality estimates, baseline incidence 

rates, populations exposed, and transferability of the effect estimate to diverse 

locations. As a result, the reported confidence intervals and range of estimates give 

an incomplete picture about the overall uncertainty in the PM2.5 estimates. This 

information should be interpreted within the context of the larger uncertainty 

surrounding the entire analysis.

 Most of the estimated avoided premature deaths occur at or above the lowest 

measured PM2.5 concentration in the two studies used to estimate mortality 

benefits. In general, we have greater confidence in risk estimates based on PM2.5 

concentrations where the bulk of the data reside and somewhat less confidence 

where data density is lower.

 We analyzed full attainment in 2020, and projecting key variables introduces 

uncertainty. Inherent in any analysis of future regulatory programs are uncertainties 

in projecting atmospheric conditions and source-level emissions, as well as 

population, health baselines, incomes, technology, and other factors.

 There are uncertainties related to the health impact functions used in the analysis. 

These include within-study variability; pooling across studies; the application of C-R 

functions nationwide and for all particle species; extrapolation of impact functions 

across populations; and various uncertainties in the C-R function, including causality 

and shape of the function at low concentrations. Therefore, benefits may be underor over-estimates.

 This analysis omits certain unquantified effects due to lack of data, time, and 

resources. These unquantified endpoints include other health and ecosystem 

effects. The EPA will continue to evaluate new methods and models and select those 

most appropriate for estimating the benefits of reductions in air pollution.
ES-12

ES.3.2 Control Strategy and Cost Analysis Caveats and Limitations

Control Technology Data

 Technologies applied may not reflect emerging devices that may be available in 

future years.

 Control efficiency data depend on equipment being well maintained.

 Area source controls assume a constant estimate of emission reductions, despite 

variability in extent and scale of application.

Control Strategy Development

 States may develop different control strategies than the ones illustrated.

 Data on baseline controls from current SIPs are lacking.

 Timing of control strategies may be different than envisioned in the RIA.

 Controls are applied within the county with the violating monitor. It is possible that 

additional known controls could be available in a wider geographical area.

 Unknown controls were needed to reach attainment in several counties. Costs 

associated with these unknown controls were estimated using a fixed-cost per ton 

methodology as well as an extrapolated cost methodology.

 Emissions reductions from mobile sources, EGUs, other PM2.5 precursors (i.e., 

ammonia and VOC), and voluntary programs are not reflected in the analyses.

Technological Change

 Emission reductions do not reflect potential effects of technological change that may 

be available in future years.

 Effects of “learning by doing” are not accounted for in the emission reduction 

estimates.

 Future technology developments in sectors not analyzed here (e.g., EGUs) may be 

transferrable to non-EGU and area sources, making these sources more viable for 

achieving future attainment at a lower cost than the cost presented in this analysis.

Engineering Cost Estimates

 Because of data limitations, we were unable to discount compliance costs for all 

sectors at 3%.

 Estimates of private compliance cost are used as a proxy for social cost.

Unquantified Costs

 A number of costs remain unquantified, including administration costs of federal and 

state SIP programs, and transactional costs.
ES-13

ES.3.3 Limitations of the Secondary Standard Analysis

Visibility design values for 2020 were calculated using the CMAQ modeling information 

and 2004-2006 ambient measurements. To determine the design values for meeting the 

current primary PM2.5 standard and proposed alternative primary standards, we used a 

methodology, described in Chapter 3, to estimate the small emissions reductions needed from 

control measures to show attainment and to estimate the costs and benefits of attaining the 

proposed alternative primary standards. It is not possible to apply this methodology to the 

visibility design values.8 As a result, the only analysis available for the proposed alternative 

secondary standards in 2020 is prior to full attainment of the current primary standard. All 

monitors analyzed are projected to attain a secondary standard of 30 dv in the 2020 base case. 

Given the 24-hr design value reductions that were included in simulating attainment of 15/35 in 

the 2020 base case, we are confident in our conclusion that all monitors will also attain a 

secondary standard of 28 dv when they attain the current primary standards.9

ES.4 Discussion

An extensive body of scientific evidence documented in the Integrated Science 

Assessment for Particulate Matter (PM ISA) indicates that PM2.5 can penetrate deep into the 

lungs and cause serious health effects, including premature death and other non-fatal illnesses 

(U.S. EPA, 2009). As described in the preamble to the proposed regulation, the proposed 

changes to the standards are based on an integrative assessment of an extensive body of new 

scientific evidence (U.S. EPA, 2009). Health studies published since the PM ISA(e.g., Pope et al. 

[2009]) confirm that recent levels of PM2.5 have had a significant impact on public health. Based 

on the air quality analysis in this RIA, the EPA projects that nearly all counties with PM2.5 

monitors in the U.S. would meet an annual standard of 12 μg/m3 by 2020 without additional 

 8

As described in Chapter 3, we apply a methodology of air quality ratios to estimate the emissions reductions 

needed to meet the current and proposed alternative levels for the primary standard. While this methodology 

can estimate how these emissions reductions will affect changes in the future-year annual design value and the 

corresponding response of the future-year 24-hr design value to changes in the annual design value, it is unable 

to estimate how each of the PM2.5 species will change with these emission reductions. Given that estimating 

changes in future-year visibility is dependent on the IMPROVE equation and how the PM2.5 species are 

projected to change in time, we are unable to estimate visibility design values for meeting the current and 

proposed alternative levels for the primary standard. 9 The projected 2020 base case design values for the secondary standard for the following monitors with id 

numbers 60658001 (located in Riverside, CA), 60290014 (located in Kern, CA), and 60990005 (located in 

Stanislaus, CA) are 29 dv, 30 dv, and 29 dv, respectively. The emissions reductions selected for simulating 

attainment of 15/35 in the 2020 base case resulted in the following reductions in the 24-hr design values for 

these three monitors: 11.1 μg/m3

, 21.9 μg/m3 and 5.3 μg/m3, respectively. We believe that these emissions 

reductions and 24-hr design value changes for simulating the current primary standard levels of 15/35 will be 

enough to lower the projected 2020 secondary standard design values for these three monitors to 28 dv or 

lower.
ES-14

federal, state, or local PM control programs. This demonstrates the substantial progress that 

the U.S. has made in reducing air pollution emissions over the last several decades. Regulations 

such as the EPA’s recent Mercury and Air Toxics Standards (MATS), the Cross-State Air Pollution 

Rule (CSAPR), and other federal programs such as diesel standards will provide substantial 

improvements in regional concentrations of PM2.5. Our analysis shows a few areas would still 

need additional emissions reductions to address local sources of air pollution, including ports 

and uncontrolled industrial emissions. For this reason, we have designed the RIA analysis to 

focus on local controls in these few areas. We estimate that these additional local controls 

would yield benefits well in excess of costs, by a ratio of at least 30 to 1.

The setting of a NAAQS does not compel specific pollution reductions, and as such does 

not directly result in costs or benefits. For this reason, NAAQS RIAs are merely illustrative. The 

NAAQS RIAs illustrate the potential costs and benefits of additional steps States could take to 

attain a revised air quality standard nationwide beyond rules already on the books. We base 

our illustrative estimates on an array of emission control strategies for different sources. The 

costs and benefits identified in this RIA will not be realized until specific controls are mandated 

by State Implementation Plans (SIPs) or other federal regulations. In short, NAAQS RIAs 

hypothesize, but do not prescribe, the control strategies that States may choose to enact when 

implementing a revised NAAQS.

It is important to emphasize that the EPA does not “double count” the costs or the 

benefits of our rules. Emission reductions achieved under rules that require specific actions 

from sources—such as MATS—are in the baseline of this NAAQS analysis, as are emission 

reductions needed to meet the current NAAQS. For this reason, the cost and benefits estimates 

provided in this RIA and all other NAAQS RIAs should not be added to the estimates for 

implementation rules.

Furthermore, the monetized benefits estimates do not paint a complete picture of the 

burden of PM to public health. For example, modeling by Fann et al. (2012) estimated that 2005 

levels of air pollution were responsible for between 130,000 and 320,000 PM2.5-related deaths, 

or between 6.1% and 15% of total deaths from all causes in the continental United States. The 

monetized benefits associated with attaining the proposed range of standards appear modest 

when viewed within the context of the potential overall public health burden of PM2.5 and 

ozone air pollution estimated by Fann et al. (2012), but this is primarily because regulations 

already on the books will make great strides toward reducing future levels of PM. One 

important distinction between the total public health burden estimated for 2005 air pollution 

levels and the estimated benefits in this RIA is that ambient levels of PM2.5 will have improved 
ES-15

substantially by 2020. For example, we estimate that SO2 emissions in the U.S. would fall from 

14 million tons in 2005 to less than 5 million tons by 2020 (a reduction of 66%). For this reason, 

States will only need to achieve small air quality improvements to reach the proposed PM 

standards. As shown in recent RIAs for the CSAPR (U.S. EPA, 2011a) and MATS (U.S. EPA, 

2011b), implementing other federal and state air quality actions will address a substantial

fraction of the total public health burden of PM2.5 and ozone air pollution.

The NAAQS are not set at levels that eliminate the risk of air pollution. Instead, the 

Administrator sets the NAAQS at a level requisite to protect public health with an adequate

margin of safety, taking into consideration effects on susceptible populations based on the 

scientific literature. The risk analysis prepared in support of this PM NAAQS reported risks 

below these levels, while acknowledging that the confidence in those effect estimates is higher 

at levels closer to the standard (U.S. EPA, 2010). While benefits occurring below the standard 

are assumed to be more uncertain than those occurring above the standard, the EPA considers 

these to be legitimate components of the total benefits estimate. Though there are greater 

uncertainties at lower PM2.5 concentrations, there is no evidence of a population-level 

threshold in PM2.5-related health effects in the epidemiology literature.

Lastly, the EPA was unable to monetize fully all of the benefits associated with reaching 

these standards in this RIA, including other health effects of PM, visibility effects, ecosystem 

effects, and climate effects. If the EPA were able to monetize all of the benefits, the benefits 

would exceed the costs by an even greater margin. Even when considered in light of the 

quantified and unquantified uncertainties identified in this RIA, we believe that implementing 

the proposed range of standards would have substantial public health benefits that outweigh 

the costs.

ES.5 References

Fann, N., A. Lamson, K. Wesson, D. Risley, S.C. Anenberg, and B.J. Hubbell. 2012. “Estimating 

the National Public Health Burden Associated with Exposure to Ambient PM2.5 and 

Ozone. Risk Analysis.” Risk Analysis 32(1): 81-95.

Krewski D, et al. 2009. “Extended follow-up and spatial analysis of the American Cancer Society 

study linking particulate air pollution and mortality.” HEI Research Report, 140, Health 

Effects Institute, Boston, MA. Pope, C.A., III, E. Majid, and D. Dockery. 2009. “Fine 

Particle Air Pollution and Life Expectancy in the United States.” New England Journal of 

Medicine 360: 376-386.
ES-16

U.S. Environmental Protection Agency (U.S. EPA). 2009. Integrated Science Assessment for 

Particulate Matter (Final Report). EPA-600-R-08-139F. National Center for 

Environmental Assessment—RTP Division. December. Available on the Internet at 

<http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=216546>.

U.S. Environmental Protection Agency (U.S. EPA). 2010. Risk and Exposure Assessment for 

Review of Particulate Matter. EPA-452/R-10-005. Office of Air Quality Planning and 

Standards, Research Triangle Park, NC. September. Available on the Internet at 

<http://www.epa.gov/ttnnaaqs/standards/pm/data/PM_RA_FINAL_June_2010.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2011a. Regulatory Impact Analysis for the 

Federal Implementation Plans to Reduce Interstate Transport of Fine Particulate Matter 

and Ozone in 27 States; Correction of SIP Approvals for 22 States. June. Available on the 

Internet at <http://www.epa.gov/airtransport/pdfs/FinalRIA.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2011b. Regulatory Impact Analysis for the 

Final Mercury and Air Toxics Standards. EPA-452/R-11-011. December. Available on the 

Internet at <http://www.epa.gov/ttn/ecas/regdata/RIAs/matsriafinal.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2011c. Policy Assessment for the Review of 

the Particulate Matter National Ambient Air Quality Standards. EPA-452/D-11-003. April. 

Available on the Internet at 

<http://www.epa.gov/ttnnaaqs/standards/pm/s_pm_2007_pa.html>.
1-1

CHAPTER 1

INTRODUCTION AND BACKGROUND

1.1 Synopsis

This chapter summarizes the purpose and results of this Regulatory Impact Analysis 

(RIA). This RIA estimates the human health and welfare benefits and costs of attaining several 

particulate matter (PM) National Ambient Air Quality Standards (NAAQS) nationwide. According 

to the Clean Air Act (“Act”), the EPA must use health-based criteria in setting the NAAQS and 

cannot consider estimates of compliance cost. The EPA is producing this RIA both to provide the 

public a sense of the benefits and costs of meeting a new NAAQS and to meet the requirements 

of Executive Orders 12866 and 13563.

1.2 Background

1.2.1 NAAQS

Two sections of the Clean Air Act (“the Act”) govern the establishment and revision of 

NAAQS. Section 108 (42 U.S.C. 7408) directs the Administrator to identify pollutants that “may 

reasonably be anticipated to endanger public health or welfare” and to issue air quality criteria 

for them. These air quality criteria are intended to “accurately reflect the latest scientific 

knowledge useful in indicating the kind and extent of all identifiable effects on public health or 

welfare which may be expected from the presence of [a] pollutant in the ambient air.” PM is 

one of six pollutants for which the EPA has developed air quality criteria.

Section 109 (42 U.S.C. 7409) directs the Administrator to propose and promulgate 

“primary” and “secondary” NAAQS for pollutants identified under section 108. Section 

109(b)(1) defines a primary standard as “the attainment and maintenance of which in the 

judgment of the Administrator, based on [the] criteria and allowing an adequate margin of 

safety, [are] requisite to protect the public health.” A secondary standard, as defined in section 

109(b)(2), must “specify a level of air quality the attainment and maintenance of which in the

judgment of the Administrator, based on [the] criteria, [are] requisite to protect the public 

welfare from any known or anticipated adverse effects associated with the presence of [the] 

pollutant in the ambient air.” Welfare effects as defined in section 302(h) [42 U.S.C. 7602(h)] 

include but are not limited to “effects on soils, water, crops, vegetation, manmade materials, 

animals, wildlife, weather, visibility and climate, damage to and deterioration of property, and 

hazards to transportation, as well as effects on economic values and on personal comfort and 

well-being.”
1-2

Section 109(d) of the Act directs the Administrator to review existing criteria and 

standards at 5-year intervals. When warranted by such review, the Administrator is to retain or 

revise the NAAQS. After promulgation or revision of the NAAQS, the standards are 

implemented by the states.

1.2.2 2006 PM NAAQS

In 2006, the EPA’s final PM rule established a 24-hour standard of 35 μg/m3 and 

retained the annual standard of 15 μg/m3. The EPA revised the secondary standards for fine 

particles by making them identical in all respects to the primary standards. Following 

promulgation of the final rule in 2006, several parties filed petitions for its review. On February 

24, 2009, the U.S. Court of Appeals for the District of Columbia Circuit remanded the primary 

annual PM2.5 NAAQS to the EPA citing that the EPA failed to adequately explain why the 

standard provided the requisite protection from both short- and long-term exposures to fine 

particles, including protection for at-risk populations. The court remanded the secondary 

standards to the EPA citing that the Agency failed to adequately explain why setting the 

secondary PM standards identical to the primary standards provided the required protection 

for public welfare, including protection from visibility impairment.

1.3 Role of this RIA in the Process of Setting the NAAQS

1.3.1 Legislative Roles

In setting primary ambient air quality standards, the EPA’s responsibility under the law 

is to establish standards that protect public health, regardless of the costs of implementing a 

new standard. The Act requires the EPA, for each criteria pollutant, to set a standard that 

protects public health with “an adequate margin of safety.” As interpreted by the Agency and 

the courts, the Act requires the EPA to create standards based on health considerations only.

The prohibition against the consideration of cost in the setting of the primary air quality 

standard, however, does not mean that costs or other economic considerations are 

unimportant or should be ignored. The Agency believes that consideration of costs and benefits 

is essential to making efficient, cost-effective decisions for implementing these standards. The 

impact of cost and efficiency is considered by states during this process, as they decide what 

timelines, strategies, and policies make the most sense. This RIA is intended to inform the 

public about the potential costs and benefits that may result when new standards are 

implemented, but it is not relevant to establishing the standards themselves.
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1.3.2 Role of Statutory and Executive Orders

This RIA is separate from the NAAQS decision-making process, but several statutes and 

executive orders still apply to any public documentation. The analysis required by these 

statutes and executive orders is presented in Chapter 9.

The EPA presents this RIA pursuant to Executive Orders 12866 and 13563 and the 

guidelines of Office of Management and Budget (OMB) Circular A-4.1 These documents present 

guidelines for the EPA to assess the benefits and costs of the selected regulatory option as well 

as more and less stringent options than those proposed or selected. In concordance with these 

guidelines, the RIA also analyzes the benefits and costs of alternative combinations of primary 

PM2.5 standards, one combination that is more stringent than the existing standards, but less 

stringent than the proposed standards and another combination that is more stringent than the 

proposed standards (see Section 1.4.2).

In the current PM NAAQS review, the EPA is proposing to revise the level of the primary 

annual PM2.5 standard within the range of 12 to 13 μg/m3 in conjunction with retaining the level 

of the 24-hour standard at 35 μg/m3 (denoted 12/35 and 13/35). In addition to the range of 

12/35 to 13/35, the RIA also analyzes the benefits and costs of incremental control strategies 

for two other alternative standards (11/35 and 11/30). In analyzing the current 15/35 standard 

(baseline), the EPA determined that all counties would meet the 14/35 standard concurrently 

with meeting the existing 15/35 standard at no additional cost. Consequently, no incremental 

costs or benefits are associated with 14/35; thus, no analysis of 14/35 is presented.

Benefit and cost estimates provided in the RIA are not additive to benefits and costs 

from other regulations, and, further, the costs and benefits identified in this RIA will not be 

realized until specific controls are mandated by State Implementation Plans (SIPs) or other 

federal regulations.

1.3.3 The Need for National Ambient Air Quality Standards

OMB Circular A-4 indicates that one of the reasons a regulation such as the NAAQS may 

be issued is to address existing “externalities.” An externality occurs when one party’s actions 

impose uncompensated benefits or costs on another party. Environmental problems are a 

classic case of an externality. Setting primary and secondary air quality standards is one way the 

 1 U.S. Office of Management and Budget. Circular A-4, September 17, 2003, available at 

<http://www.whitehouse.gov/omb/circulars/a004/a-4.pdf>.
1-4

government can address an externality and thereby increase air quality and improve overall 

public health and welfare.

1.3.4 Illustrative Nature of the Analysis

This NAAQS RIA is an illustrative analysis that provides useful insights into a limited 

number of emissions control scenarios that states might implement to achieve revised NAAQS. 

Because states are ultimately responsible for implementing strategies to meet any revised 

standard, the control scenarios in this RIA are necessarily hypothetical in nature. Important 

uncertainties and limitations are documented in the relevant portions of the analysis.

The illustrative goals of this RIA are somewhat different from other EPA analyses of 

national rules, or the implementation plans states develop, and the distinctions are worth brief 

mention. This RIA does not assess the regulatory impact of an EPA-prescribed national rule, nor 

does it attempt to model the specific actions that any state would take to implement a revised 

standard. This analysis attempts to estimate the costs and human and welfare benefits of costeffective implementation strategies that might be undertaken to achieve national attainment of 

new standards. These hypothetical strategies represent a scenario where states use one set of 

cost-effective controls to attain a revised NAAQS. Because states—not the EPA—will implement 

any revised NAAQS, they will ultimately determine appropriate emissions control scenarios. 

SIPs would likely vary from the EPA’s estimates due to differences in the data and assumptions 

that states use to develop these plans.

The illustrative attainment scenarios presented in this RIA were constructed with the 

understanding that there are inherent uncertainties in projecting emissions and controls.

1.4 Overview and Design of the RIA

The RIA evaluates the costs and benefits of hypothetical national strategies to attain 

several alternative PM standards.

1.4.1 Modeling PM2.5 Levels in the Future (Analysis Year = 2020)

A national-scale air quality modeling analysis was performed to estimate future-year 

annual and 24-hour PM2.5 concentrations and light extinction for the future year of 2020. Air 

quality ratios were then developed using model responsiveness to emissions changes between 

a recent year of air quality, 2005, and a future year of air quality, 2020. The air quality ratios 

were used to determine potential control scenarios designed to attain the proposed alternative 

NAAQS, as well as the costs of attaining these levels. These data were then used to estimate 
1-5

how air quality would change under each set of potential control scenarios, and as inputs to the 

calculation of expected benefits from the alternative NAAQS considered in this assessment.

1.4.2 Existing and Alternative PM Air Quality Standards

Currently two primary PM2.5 standards provide public health protection from effects 

associated with fine particle exposures. The annual standard is set at a level of 15.0 μg/m3, 

based on the 3-year average of annual arithmetic mean PM2.5 concentrations. The 24-hour 

standard is set at a level of 35 μg/m3, based on the 3-year average of the 98th percentile of 

24-hour PM2.5 concentrations. In the RIA, the current suite of primary PM2.5 standards, 

including both annual and 24-hour averaging times, is denoted as 15/35.

In the current PM NAAQS review, the EPA is proposing to revise the level of the primary 

annual PM2.5 standard within the range of 12 to 13 μg/m3 in conjunction with retaining the level 

of the 24-hour standard at 35 μg/m3 (denoted 12/35 and 13/35).

In addition to the range of 12/35 to 13/35, the RIA also analyzes the benefits and costs 

of incremental control strategies for two other alternative standards (11/35 and 11/30). The 

four alternative standards analyzed are as follows:

 A revised annual standard level of 13 μg/m3 in conjunction with retaining the 

24-hour standard level at 35 μg/m3 (13/35)

 A revised annual standard level of 12 μg/m3 in conjunction with retaining the 

24-hour standard level at 35 μg/m3 (12/35)

 A revised annual standard level of 11 μg/m3 in conjunction with retaining the 

24-hour standard level at 35 μg/m3 (11/35 )

 A revised annual standard level of 11 μg/m3 in conjunction with a revised 24-hour 

standard level at 30 μg/m3 (11/30 )

In analyzing the current 15/35 standard (baseline), the EPA determined that all counties 

would meet the 14/35 standard concurrently with meeting the existing 15/35 standard at no 

additional cost. Consequently, no incremental costs or benefits are associated with 14/35; thus, 

no analysis of 14/35 is presented in this RIA.

Currently, the existing secondary PM2.5 standards are identical in all respects to the 

primary standards. In the current PM NAAQS review, the EPA is proposing to add a distinct 

standard for PM2.5 to provide protection from PM-related visibility impairment. Specifically, the 

EPA is proposing to establish a separate secondary standard defined in terms of a PM2.5
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visibility index, which would use speciated PM2.5 mass concentrations and relative humidity 

data to calculate PM2.5 light extinction, similar to the Regional Haze Program; a 24-hour 

averaging time; a 90th percentile form; and a level of either 30 deciviews (dv) or 28 dv. Based 

on the air quality analysis conducted for the primary PM2.5 standard, all monitored areas are 

estimated to be in attainment with both proposed secondary standard levels in 2020, assuming 

full attainment of the primary PM2.5 standard. For the two optional levels proposed for the 

secondary standard, no additional costs or benefits will be realized beyond those quantified for 

meeting the primary PM2.5 standard in this RIA.

With regard to the primary and secondary standards for particles less than or equal to 

10 μm in diameter (PM10), the EPA is proposing to retain the current primary and secondary 

24-hour PM10 standards. Both standards are the same. The current primary and secondary 

24-hour standards are set at a level of 150 μg/m3

, not to be exceeded more than once per year 

on average over 3 years (EPA, 1997)2. Since the benefit cost analysis of the alternative PM10 

standards was conducted when the standard was selected, this RIA does not repeat that 

analysis here.

1.4.3 Benefits Analysis Approach

The EPA estimated human health (e.g., mortality and morbidity effects) under full 

attainment of several alternative PM standards. We considered an array of health impacts 

attributable to changes in PM2.5. Even though the alternative primary standards are designed to 

protect against adverse effects to human health, the emission reductions have welfare 

co-benefits in addition to the direct human health benefits. The term welfare co-benefits covers 

both environmental and societal benefits of reducing pollution, such as reductions in visibility 

impairment, materials damage, and ecosystem damage. Despite our attempts to quantify and 

monetize as many of the benefits as possible, many welfare benefits are not quantified or 

monetized.

1.4.4 Costs Analysis Approach

The EPA estimated total costs under partial and full attainment of several alternative 

PM standards. The engineering costs generally include the costs of purchasing, installing, and 

operating the referenced control technologies. The technologies and control strategies selected 

for analysis are illustrative of one way in which nonattainment areas could meet a revised 

 2 U.S. Environmental Protection Agency. 1997. Regulatory Impact Analyses for the Particulate Matter and Ozone 

National Ambient Air Quality Standards and Proposed Regional Haze Rule. Available at: 

http://www.epa.gov/ttn/oarpg/naaqsfin/ria.html.
1-7

standard. There are numerous ways to construct and evaluate potential control programs that 

would bring areas into attainment with alternative standards, and the EPA anticipates that 

state and local governments will consider programs that are best suited for local conditions. 

The partial attainment cost analysis reflects the costs associated with known controls. Costs for 

full attainment include estimates for the engineering costs of the additional tons of emissions 

reductions that are needed beyond identified controls, referred to as extrapolated costs. The 

EPA recognizes that the extrapolated portion of the engineering cost estimates reflects 

substantial uncertainty about which sectors, and which technologies, might become available 

for cost-effective application in the future.

1.5 Organization of this Regulatory Impact Analysis

This RIA includes the following 11 chapters:

 Chapter 1: Introduction and Background. This chapter introduces the purpose of the 

RIA.

 Chapter 2: Defining the PM2.5 Air Quality Problem. This chapter characterizes the 

nature, scope, and magnitude of the current-year PM2.5 problem.

 Chapter 3: Air Quality Modeling and Analysis. The data, tools, and methodology used 

for the air quality modeling are described in this chapter, as well as the postprocessing techniques used to produce a number of air quality metrics for input into 

the analysis of costs and benefits.

 Chapter 4: Control Strategies. This chapter presents the hypothetical control 

strategies, the geographic areas where controls were applied, and the results of the 

modeling that predicted PM2.5 concentrations in 2020 after applying the control 

strategies.

 Chapter 5: Health Benefits Analysis Approach and Results. This chapter quantifies the 

health-related benefits of the PM2.5-related air quality improvements associated 

with several alternative standards.

 Chapter 6: Welfare Benefits Analysis Approach. This chapter quantifies and 

monetizes selected other welfare effects, including changes in visibility, materials 

damage, ecological effects from PM deposition, ecological effects from nitrogen and 

sulfur emissions, vegetation effects from ozone exposure, ecological effects from 

mercury deposition, and climate effects.

 Chapter 7: Engineering Cost Analysis. This chapter summarizes the data sources and 

methodology used to estimate the engineering costs of partial and full attainment of 

several alternative standards.
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 Chapter 8: Comparison of Benefits and Costs. This chapter compares estimates of the 

total benefits with total costs and summarizes the net benefits of several alternative 

standards.

 Chapter 9: Statutory and Executive Order Impact Analyses. This chapter summarizes 

the Statutory and Executive Order impact analyses.

 Chapter 10: Secondary Standards Analysis. This chapter contains an evaluation of the 

regulatory impacts associated with a distinct secondary NAAQS for PM2.5.

 Chapter 11: Economic Impacts—Employment. This chapter provides a qualitative 

discussion of employment impacts of air quality regulations.
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CHAPTER 2

DEFINING THE PM AIR QUALITY PROBLEM

2.1 Synopsis

This chapter characterizes the nature, scope and magnitude of the current year PM 

problem. It includes 1) a summary of the spatial and temporal distribution of PM2.5 and the 

likely origin from direct emissions or atmospheric transformations of gaseous precursors; 

2) discussion of what visibility is and how it is calculated from measured concentrations and 

meteorological values; and 3) current year design values for PM2.5 and visibility.

2.2 Particulate Matter (PM) Properties

Particulate matter (PM) is a highly complex mixture of solid particles and liquid droplets 

distributed among numerous atmospheric gases which interact with solid and liquid phases. 

Particles range in size from those smaller than 1 nanometer (10-9 meter) to over 100 

micrometer (μm, or 10-6 meter) in diameter (for reference, a typical strand of human hair is 70 

μm in diameter and a grain of salt is about 100 μm). Atmospheric particles can be grouped into 

several classes according to their aerodynamic and physical sizes, including ultrafine particles 

(<0.1 μm), accumulation mode or ‘fine’ particles (0.1 to ~3 μm), and coarse particles (>1 μm). 

For regulatory purposes, fine particles are measured as PM2.5 and inhalable or thoracic coarse 

particles are measured as PM10-2.5, corresponding to their size (diameter) range in micrometers 

and referring to total particle mass under 2.5 and between 2.5 and 10 micrometers, 

respectively. The EPA currently has standards that measure PM2.5 and PM10.

Particles span many sizes and shapes and consist of hundreds of different chemicals. 

Particles are emitted directly from sources and are also formed through atmospheric chemical 

reactions; the former are often referred to as “primary” particles, and the latter as “secondary” 

particles. Particle pollution also varies by time of year and location and is affected by several 

weather-related factors, such as temperature, clouds, humidity, and wind. A further layer of 

complexity comes from particles’ ability to shift between solid/liquid and gaseous phases, 

which is influenced by concentration and meteorology, especially temperature.

Particles are made up of different chemical components. The major chemical 

components include carbonaceous materials (carbon soot and organic compounds), and 

inorganic compounds including, sulfate and nitrate compounds that usually include ammonium, 

and a mix of substances often apportioned to crustal materials such as soil and ash. As 

mentioned above, particulate matter includes both “primary” PM, which is directly emitted into 

the air, and “secondary” PM, which forms indirectly from emissions from fuel combustion and 
2-2

other sources. Primary PM consists of carbonaceous materials (soot and accompanying 

organics) and includes:

 Elemental carbon, organic carbon, and crustal material directly emitted from cars, 

trucks, heavy equipment, forest fires, some industrial processes and burning waste.

 Both combustion and process related fine metals and larger crustal material from 

unpaved roads, stone crushing, construction sites, and metallurgical operations.

Secondary PM forms in the atmosphere from gases. Some of these reactions require 

sunlight and/or water vapor. Secondary PM includes:

 Sulfates formed from sulfur dioxide (SO2) emissions from power plants and industrial 

facilities;

 Nitrates formed from nitrogen oxide (NOx) emissions from cars, trucks, industrial 

facilities, and power plants; and

 Ammonium formed from ammonia (NH3) emissions from gas-powered vehicles and 

fertilizer and animal feed operations. These contribute to the formation of sulfates 

and nitrates that exist in the atmosphere as ammonium sulfate and ammonium 

nitrate.

1

 Organic carbon (OC) formed from reactive organic gas emissions, including volatile 

organic compounds (VOCs), from cars, trucks, industrial facilities, forest fires, and 

biogenic sources such as trees.

1

As described above, organic carbon has both primary and secondary components. The 

percentage contribution to total OC from directly emitted OC versus secondarily formed OC 

varies based on location. In an urban area, near direct sources of OC such as cars, trucks, and 

industrial sources, the percentage of primary OC may dominate, whereas, in a rural area with 

more biogenic sources, OC may be mostly secondarily formed. In addition, emissions from 

sources such as power plants and industrial facilities may have small amounts of directly 

emitted PM2.5 speciated into sulfate. Figure 2-1 (EPA, 2006) shows, in detail, the sources 

contributing to directly emitted PM2.5 and PM10, as well as PM precursors: SO2, NOx, NH3, and 

VOC.

 1 Direct NH3 and VOC emissions are not controlled as part of the control strategy analysis. Emissions of PM2.5, NOx, 

and SO2 are controlled in the control strategies, for a complete discussion please refer to Chapter 4. 
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Figure 2-1. Detailed Source Categorization of Anthropogenic Emissions of Primary PM2.5, 

PM10 and Gaseous Precursor Species SO2, NOx, NH3 and VOCs for 2002 in Units of Million 

Metric Tons (MMT). EGUs = Electricity Generating Units

Source: U.S. EPA (2006)
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2.2.1 PM2.5

“Fine particles” or PM2.5 are particles with diameters that are less than 2.5 micrometers. 

As discussed above, these particles are composed of both primary (derived directly from 

emissions) and secondary (derived from atmospheric reactions involving gaseous precursors) 

components.

2.2.1.1 Geographical Scale and Transport

Both local and regional sources contribute to particle pollution. Fine particles can be 

transported long distances by wind and weather and can be found in the air thousands of miles 

from where they formed. Nitrates and sulfates formed from NOx and SO2 are generally 

transported over wide areas leading to substantial background contributions in urban areas. 

Organic carbon, which has both a primary and secondary component, can also be transported 

but to a far lesser degree. In general, higher concentrations of elemental carbon and crustal 

matter are found closest to the sources of these emissions.

Figure 2-2 shows how much of the PM2.5 mass can be attributed to local versus regional 

sources for 13 selected urban areas (EPA, 2004).2 In each of these urban areas, monitoring sites 

were paired with nearby rural sites. When the average rural concentration is subtracted from 

the measured urban concentration, the estimated local and regional contributions become 

apparent. We observe a large urban excess across the U.S. for most PM2.5 species but especially 

for total carbon mass with Fresno, CA having the highest observed measure. Larger urban 

excess of nitrates is seen in the western U.S. with Fresno, CA and Salt Lake City, UT significantly 

higher than all other areas. These results indicate that local sources of these pollutants are 

indeed contributing to the PM2.5 air quality problem in these areas. As expected for a 

predominately regional pollutant, only a modest urban excess is observed for sulfates.

In the East, regional pollution contributes to more than half of total PM2.5

concentrations. Rural background PM2.5 concentrations are high in the East and are somewhat 

uniform over large geographic areas. These regional concentrations come from emission 

sources such as power plants, natural sources, and urban pollution and can be transported 

hundreds of miles and reflect to some extent the denser clustering of urban areas in the East as 

compared to the West. In the West, much of the measured PM2.5 concentrations tend to be 

local in nature. These concentrations come from emission sources such as wood combustion 

and mobile sources. In general, these data indicate that reducing regional SO2 and local sources 

 2 The measured PM2.5 concentration is not necessarily the maximum for each urban area.
2-5 

of carbon in the East, and local sources of nitrate and carbon in the West will be most effective 

in reducing PM2.5 concentrations.

Figure 2-2. Regional and Local Contributions to Annual Average PM2.5 by Particulate SO4

2–, 

Nitrate and Total Carbon (i.e., organic plus EC) for Select Urban Areas Based on Paired 2000-

2004 IMPROVEa and CSNb Monitoring Sites

a Interagency Monitoring of Protected Visual Environments (IMPROVE) http://vista.cira.colostate.edu/improve

b Chemical Speciation Network (CSN)
2-6 

2.2.1.2 Regional and Seasonal Patterns

The chemical makeup of particles varies across the United States, as illustrated in 

Figure 2-3. For example, the higher regional emissions of SO2 in the East result in higher 

absolute and relative amounts of sulfates as compared to the western U.S. Fine particles in 

southern California generally contain more nitrates than other areas of the country. Carbon is a 

substantial component of fine particles everywhere.

Figure 2-3. Regional and Seasonal Trends in Annual PM2.5 Composition from 2002 to 2007 

Derived Using the SANDWICH Method. Data from the 42 monitoring locations shown on the 

map were stratified by region and season including cool months (October–April) and warm 

months (May–September)

Fine particles can also have a seasonal pattern. As shown in Figure 2-3, PM2.5 values in 

the eastern half of the United States are typically higher in warmer weather when 
2-7

meteorological conditions are more favorable for the formation and build up of sulfates from 

higher sulfur dioxide (SO2) emissions from power plants in that region. Fine particle 

concentrations tend to be higher in the cooler calendar months in urban areas in the West, in 

part because fine particle nitrates and carbonaceous particles are more readily formed in cooler 

weather, and wood stove and fireplace use increases direct emissions of carbon.

2.2.1.3 Composition of PM2.5 as Measured by the Federal Reference Method

The speciation measurements in the preceding analyses represented data from EPA’s 

Speciation Trends Network, along with adjustments to reflect the fine particle mass associated 

with these ambient measurements. In order to more accurately predict the change in PM2.5

design values for particular emission control scenarios, EPA characterizes the composition of 

PM2.5 as measured by the Federal Reference Method (FRM). The current PM2.5 FRM does not 

capture all ambient particles measured by speciation samplers as presented in the previous 

sections. The FRM-measured fine particle mass reflects losses of ammonium nitrate (NH4NO3) 

and other semi-volatile organic compounds (SVOCs; negative artifacts). It also includes particlebound water (PBW) associated with hygroscopic species (positive artifacts) (Frank, 2006).

Comparison of FRM and collocated speciation sampler NO3

-

values in Table 2-1 show that 

annual average NO3 retention in FRM samples for six cities varies from 15% in Birmingham to 

76% in Chicago, with an annual average loss of 1 μg/m3. The volatilization is a function of 

temperature and relative humidity (RH), with more loss at higher temperatures and lower RH. 

Accordingly, nitrate is mostly retained during the cold winter days, while little may be retained 

during the hot summer days.

PM2.5 FRM measurements also include water associated with hygroscopic aerosol. This 

is because the method derives fine particle concentrations from sampled mass equilibrated at 

20–23 °C and 30–40% RH. At these conditions, the hygroscopic aerosol collected at more humid 

environments will retain their particle-bound water. The water content is higher for more acidic 

and sulfate-dominated aerosols. Combining the effects of reduced nitrate and hydrated aerosol 

causes the estimated nitrate and sulfate FRM mass to differ from the measured ions simply 

expressed as dry ammonium nitrate and ammonium sulfate. The composition of FRM mass is 

denoted as SANDWICH based on the Sulfate, Adjusted Nitrate Derived Water and Inferred 

Carbon approach from which they are derived. The PM2.5 mass estimated from speciated 

measurements of fine particles is termed ReConstructed Fine Mass (RCFM). The application of 

SANDWICH adjustments to speciation measurements at six sites is illustrated in Table 2-1 and 

Figure 2-4. EPAs modeling incorporates these SANDWICH adjustments in the Model Attainment 

Test Software (MATS) (Abt, 2010).
2-8

Table 2-1. Annual Average FRM and CSN PM2.5 NO3

– and NH4NO3 Concentrations at Six Sites 

during 2003

NO3

– (μg/m3

) NH4NO3 (μg/m3)

Percent of 

NH4NO3 in PM2.5

FRM Mass

Sampling Site 

Location

No. of 

Observations

FRM 

Mass CSNa FRMb

Difference 

(CSN − FRM) CSN FRM CSN FRM

Mayville, WI 100 9.8 2.5 1.5 1.0 3.2 1.9 33% 19%

Chicago, IL 76 14.4 2.8 2.1 0.7 3.7 2.8 25% 19%

Indianapolis, IN 92 14.8 2.5 1.3 1.3 3.2 1.6 22% 11%

Cleveland, OH 90 16.8 2.9 1.7 1.2 3.7 2.2 22% 13%

Bronx, NY 108 15.0 2.4 1.1 1.3 3.1 1.4 21% 9%

Birmingham, AL 113 17.0 1.1 0.2 0.9 1.4 0.2 8% 1%

a On denuded nylon-membrane filters for al sites except for Chicago, where denuded Teflon-membrane followed 

by nylon filters were used.

b On undenuded Teflon-membrane filters.

Figure 2-4. RCFM (left) versus SANDWICH (right) Pie Charts Comparing the Ambient and 

PM2.5 FRM Reconstructed Mass Protocols on an Annual Average Basisa

a Estimated NH4* and PBW for SANDWICH are included with their respective sulfate and nitrate mass slices. 

Circles are scaled in proportion to PM2.5 FRM mass.
2-9

2.2.1.4 2004–2006 Design Values

The annual and 24-hour PM2.5 design values were calculated using 2003–2007 FRM 

24-hour average PM2.5 concentration measurements and consistent with CFR Part 50.3

Figures 2-5 and 2-6 show the county-level maximum values for both the annual and 24-hour 

standards, respectively. For the most part, counties in the center of the U.S. have PM2.5 design 

values that are above both 11 μg/m3 for the annual standard and 30 μg/m3 for the 24-hour 

standard. In the East, the counties above the current NAAQS (i.e., 15 μg/m3 annual and 35 

μg/m3 24-hour standards) are similar. In the West, there are fewer counties above the annual 

level of 15 μg/m3 than exceed the 24-hour standard of 35 μg/m3.

Figure 2-5. Maximum County-level PM2.5 Annual Design Values Calculated Using 2003–2007 

FRM 24-hr Average PM2.5 Measurements

 3 These years of ambient measurements were selected since they frame the air quality model year of 2005. As 

discussed in Chapter 3, it is most appropriate to select ambient measurement years that include the model year 

to allow for a more true projection of future year air quality using the air quality model.
2-10

Figure 2-6. Maximum County-level PM2.5 24-hour Design Values Calculated Using 2003–2007 

FRM 24-hr Average PM2.5 Measurements

2.2.2 Visibility

Air pollution can affect light extinction, a measure of how much the components of the 

atmosphere scatter and absorb light. More light extinction means that the clarity of visual 

images and visual range is reduced, all else held constant. Light extinction is the optical 

characteristic of the atmosphere that occurs when light is either scattered or absorbed, which 

converts the light to heat. Particulate matter and gases can both scatter and absorb light. Fine 

particles with significant light-extinction efficiencies include sulfates, nitrates, organic carbon, 

elemental carbon, and soil (Sisler, 1996). The extent to which any amount of light extinction 

affects a person’s ability to view a scene depends on both scene and light characteristics. For 

example, the appearance of a nearby object (e.g., a building) is generally less sensitive to a 

change in light extinction than the appearance of a similar object at a greater distance. See 

Figure 2-7 for an illustration of the important factors affecting visibility.
2-11

Figure 2-7. Important Factors Involved in Seeing a Scenic Vista

Source: Malm, 1999.

2.2.2.1 Calculating Visibility

Visibility degradation is often directly proportional to decreases in light transmittal in 

the atmosphere. Scattering and absorption by both gases and particles decrease light 

transmittance. To quantify changes in visibility, our analysis computes a light-extinction 

coefficient, based on the work of Sisler (1996), which shows the total fraction of light that is 

decreased per unit distance. This coefficient accounts for the scattering and absorption of light 

by both particles and gases, and accounts for the higher extinction efficiency of fine particles 

compared to coarse particles. Fine particles with significant light-extinction efficiencies include 

sulfates, nitrates, organic carbon, elemental carbon (soot), and soil (Sisler, 1996).

As described in the Policy Assessment Document (EPA, 2011), the formula for total light 

extinction (bext) in units of Mm-1 using the original IMPROVE equation is:

bext = 3 x f(RH) x [Sulfate] + 3 x f(RH) x [Nitrate] + 4 x [Organic Mass] +

10 x [Elemental Carbon] + 1 x [Fine Soil] + 0.6 x [Coarse Mass] + 10 (2.1)
2-12

where the mass concentrations of the components indicated in brackets are in units of μg/m3

, 

and f(RH) is the unitless water growth term that depends on relative humidity. The final term in 

the equation is known as the Rayleigh scattering term and accounts for light scattering by the 

natural gases in unpolluted air. Since IMPROVE does not include ammonium ion monitoring, the 

assumption is made that all sulfate is fully neutralized ammonium sulfate and all nitrate is 

assumed to be ammonium nitrate.

Based upon the light-extinction coefficient, a unitless visibility index, called a “deciview,” 

can also be calculated using Equation (2.2):

Deciviews = 10 ∗ ln �

391

VR � = 10 ∗ ln �

βext

10 � (2.2)

where VR denotes visual range (in kilometers) and βext denotes light extinction (in Mm-1

). The 

deciview metric provides a scale for perceived visual changes over the entire range of 

conditions, from clear to hazy. Under many scenic conditions, the average person can generally 

perceive a change of one deciview. The higher the deciview value, the worse the visibility. Thus, 

an improvement in visibility is a decrease in deciview value.

2.2.2.2 Geographical Scale and Variability

Annual average visibility conditions (reflecting light extinction due to both 

anthropogenic and non-anthropogenic sources) vary regionally across the U.S. and by season 

(U.S. EPA, 2009). Particulate sulfate is the dominant source of regional haze in the eastern U.S. 

(>50% of the particulate light extinction) and an important contributor to haze elsewhere in the 

country (>20% of particulate light extinction) (U.S. EPA, 2009). Particulate nitrate is an 

important contributor to light extinction in California and the upper Midwestern U.S., 

particularly during winter (U.S. EPA, 2009). Smoke plumes from large wildfires dominate many 

of the worst haze periods in the western U.S., while Asian dust only caused a few of the worst 

haze episodes, primarily in the more northerly regions of the west (U.S. EPA, 2009). Higher 

visibility impairment levels in the East are due to generally higher concentrations of fine 

particles, particularly sulfates, and higher average relative humidity levels (U.S. EPA, 2009). 

Humidity increases visibility impairment because some particles such as ammonium sulfate and 

ammonium nitrate absorb water and form droplets that become larger when relative humidity 

increases, thus resulting in increased light scattering (U.S. EPA, 2009).

Figure 2-8 shows the average trends in visual ranges at select monitors in the eastern 

and western areas of the U.S. since 1992 using data from the IMPROVE monitoring network 

(U.S. EPA (2008); IMPROVE (2010)). Because trends in haze are closely associated with trends in 
2-13

particulate sulfate and nitrate due to the simple relationship between their concentration and 

light extinction, visibility trends have improved as emissions of SO2 and NOx have decreased 

overtime due to air pollution regulations such as the Acid Rain Program (U.S. EPA, 2009). For 

example, Figure 2-8 shows that visual range increased nearly 50% in the eastern U.S. since 

19924. While visibility trends have improved in most Class 1 areas5, the recent data show that 

these areas continue to suffer from visibility impairment (U.S. EPA, 2009). Calculated from light 

extinction efficiencies from Trijonis et al. (1987, 1988), annual average visual range under 

natural conditions in the East is estimated to be 150 km ± 45 km (i.e., 65 to 120 miles) and 230 

km ± 35 km (i.e., 120 to 165 miles) in the West (Irving, 1991).

Figure 2-8. Visibility in Selected National Parks and Wilderness Areas in the U.S.,

1992–2008a,b

Source: U.S. EPA (2008) updated, IMPROVE (2010).

2.2.2.3 2004–2006 Design Values

The secondary PM2.5 NAAQS standard consists of three parts: a level, averaging period, 

and form. EPA proposes using a 3-year average, 90th percentile form for the standard, 

calculated using 24-hr speciated PM2.5 measurements. EPA analyzed two proposed levels of 30 

 4 In Figure 2-8, the “best days” are defined as the best 20% of days, the “mid-range days” are defined as the middle 

20%, and the “worst days” are defined as the worst 20% of days (IMPROVE, 2010). 5 Class I areas are areas of special national or regional natural, scenic, recreational, or historic value for which the 

Prevention of Significant Deterioration (PSD) regulations provide special protection.
2-14

dv and 28 dv, as well as a more stringent standard of 25 dv. The ambient design values analyzed 

in this RIA are based on measured 24-hour PM2.5 speciation data from 2004–20066

. These data 

were calculated as described in the Policy Assessment Document (EPA, 2011) and provided in 

Chapter 13. Figure 2-9 shows the county-level maximum design values. 20 counties were above 

30 dv and 90 counties were above 28 dv. For the more stringent proposed level, 77 additional 

counties were above 25 dv. The large majority of these counties are located in the East.

Figure 2-9. Maximum County-level Visibility Design Values Calculated Using 2004–2006 24-hr 

Average Speciated PM2.5 Measured Concentrations

2.3 References

Abt Associates, 2010. User’s Guide: Modeled Attainment Test Software. 

http://www.epa.gov/scram001/modelingapps_mats.htm

 6 These years of ambient measurements were selected since they frame the air quality model year of 2005. As 

discussed in Chapter 3, it is most appropriate to select ambient measurement years that include the model year 

to allow for a more true projection of future year air quality using the air quality model.
2-15

Frank, N.H., Retained Nitrate, Hydrated Sulfates, and Carbonaceous Mass in Federal Reference 

Method Fine Particulate Matter for Six Eastern U.S. Cities, J. Air & Waste Manage. Assoc. 

2006, 56, 500-511.

IMPROVE (Interagency Monitoring of Protected Visual Environments). 2010. 1992-2008 data 

from the IMPROVE network based on the “New IMPROVE algorithm” (updated 

November, 2008). Available on the Internet at 

<http://vista.cira.colostate.edu/improve/Data/IMPROVE/summary_data.htm.>

Irving, Patricia M., e.d., 1991. Acid Deposition: State of Science and Technology, Volume III, 

Terrestrial, Materials, Health, and Visibility Effects, The U.S. National Acid Precipitation 

Assessment Program, Chapter 24, page 24–76.

Malm, WC. 1999. Introduction to visibility. Colorado State University, Fort Collins, CO, USA, 

1983, Revised edition, 1999. Available on the Internet at 

<vista.cira.colostate.edu/improve/Education/IntroToVisinstr.htm>.

Sisler, J.F. 1996. Spatial and Seasonal Patterns and Long Term Variability of the Composition of 

the Haze in the United States: An Analysis of Data from the IMPROVE Network. Fort 

Collins, CO: Cooperative Institute for Research in the Atmosphere, Colorado State 

University.

Trijonis, J.C. et al. 1987. Preliminary extinction budget results from the RESOLVE program, pp. 

872-883. In: P.J. Bhardwaja, et al. Visibility Protection Research and Policy Aspects. Air 

Pollution Control Assoc., Pittsburgh, PA.

Trijonis, J.C. et al. 1988. RESOLVE Project Final Report: Visibility conditions and Causes of 

Visibility Degradation in the Mojave Desert of California. NWC TP #6869. Naval Weapons 

Center, China Lake, CA.

U.S. Environmental Protection Agency (EPA). 2004. Air quality criteria for particulate matter. 

U.S. Environmental Protection Agency. Research Triangle Park, NC. EPA/600/P99/002aF-bF.

U.S. Environmental Protection Agency (EPA). 2006. 2002 National Emissions Inventory Data and 

Documentation. Located online at: 

http://www.epa.gov/ttnchie1/net/2002inventory.html.

U.S. Environmental Protection Agency (EPA). 2008. National Air Quality Status and Trends 

Through 2007. U.S. Environmental Protection Agency. Research Triangle Park. EPA454/R-08-006

U.S. Environmental Protection Agency (EPA). 2009. Integrated Science Assessment for 

Particulate Matter. U.S. Environmental Protection Agency. Research Triangle Park. 

EPA/600/R-08/139F
2-16

U.S. Environmental Protection Agency (EPA). 2011. Policy Assessment for the Review of the 

Particulate Matter National Ambient Air Quality Standards. Office of Air Quality Planning 

and Standards, Research Triangle Park, NC.
3-1

CHAPTER 3

AIR QUALITY MODELING AND ANALYSIS

3.1 Synopsis

In order to evaluate the health and environmental impacts of trying to reach the 

alterative primary and secondary PM standards proposed in this RIA, it was necessary to use 

models to predict concentrations in the future. The data, tools and methodology used for 

projecting future-year air quality are described in this chapter, as well as the post-processing 

techniques used to produce a number of air quality metrics for input into the analysis of costs 

and benefits.

3.2 Modeling PM2.5 Levels in the Future

A national scale air quality modeling analysis was performed to estimate PM2.5

concentrations for the annual and 24-hour primary standards and light extinction for the future 

year of 2020.1 Air quality ratios were then developed using model responsiveness to emissions 

changes between a recent year of air quality, 2005, and a future year of air quality, 2020. The 

air quality ratios were used to determine potential control scenarios designed to attain the 

proposed alternative NAAQS, as well as the costs of attaining these levels. These data were 

then used to estimate how air quality would change under each set of potential control 

scenarios, and as inputs to the calculation of expected benefits from the alternative NAAQS 

considered in this assessment.

3.2.1 Air Quality Modeling Platform

The 2005-based Community Multi-scale Air Quality (CMAQ) modeling platform was used 

as the tool to project future-year air quality for 2020 and to estimate the costs and benefits for 

attaining the current and proposed alternative NAAQS considered in this assessment. In 

addition to the CMAQ model, the modeling platform includes the emissions, meteorology, and 

initial and boundary condition data which are inputs to this model.

The CMAQ model is a three-dimensional grid-based Eulerian air quality model designed 

to estimate the formation and fate of oxidant precursors, primary and secondary particulate 

matter concentrations and deposition over regional and urban spatial scales (e.g., over the 

contiguous U.S.) (Appel et al., 2008; Appel et al., 2007; Byun and Schere, 2006). Consideration 

 1 As described in more detail in this chapter, the future-year emissions inventory used in the air quality modeling 

analysis is a combination of emissions sectors projected to 2017 and 2020. We have chosen to label the futureyear of modeling as “2020” because the EGU sector, which is projected to 2020, is of significant importance to 

the concentrations of PM2.5 in the U.S. 
3-2

of the different processes (e.g., transport and deposition) that affect primary (directly emitted) 

and secondary (formed by atmospheric processes) PM at the regional scale in different 

locations is fundamental to understanding and assessing the effects of pollution control 

measures that affect PM, ozone and deposition of pollutants to the surface. Because it accounts 

for spatial and temporal variations as well as differences in the reactivity of emissions, CMAQ is 

useful for evaluating the impacts of the control strategies on PM2.5 concentrations. Version 

4.7.1 of CMAQ was employed for this RIA modeling, as described in the Air Quality Modeling 

Technical Support Document (EPA, 2011b).

3.2.1.1 Air Quality Modeling Domain

Figure 3-1 shows the modeling domains that were used as a part of this analysis. The 

geographic specifications for these domains are provided in Table 3-1. All three modeling 

domains contain 14 vertical layers with a top at about 16,200 meters, or 100 millibars (mb). 

Two domains with 12 km horizontal resolution were used for modeling the 2005 base year and 

2020 control strategy scenarios. These domains are labeled as the East and West 12 km 

domains in Figure 3-1. Simulations for the 36 km domain were only used to provide initial and 

boundary concentrations for the 12 km domains.

Figure 3-1. Map of the CMAQ Modeling Domains Used for PM NAAQS RIA

36km Domain Boundary

12km East Domain Boundary

12km West Domain Boundary
3-3

Table 3-1. Geographic Specifications of Modeling Domains

36 km Domain

(148 x 112 Grid Cells)

12 km East Domain

(279 x 240 Grid Cells)

12 km West Domain

(213 x 192 Grid Cells)

Longitude Latitude Longitude Latitude Longitude Latitude

SW −121.77 18.17 SW −106.79 24.99 SW −121.65 28.29

NE −58.54 52.41 NE −65.32 47.63 NE −94.94 51.91

The model produces gridded air quality concentrations on an hourly basis for the entire 

modeling domain. For this analysis, predictions from the East domain were used to provide 

data for all areas that are east of approximately 104 degrees longitude. Model predictions from 

the West domain were used for all areas west of this longitude.

3.2.1.2 Air Quality Model Inputs

CMAQ requires a variety of input files that contain information pertaining to the 

modeling domain and simulation period. These include gridded, hourly emissions estimates and 

meteorological data, and initial and boundary conditions. Separate emissions inventories were 

prepared for the 2005 base year and the future year of 2020. All other inputs were specified for 

the 2005 base year model application and remained unchanged for each future-year modeling 

scenario.

CMAQ requires detailed emissions inventories containing temporally allocated (i.e., 

hourly) emissions for each grid-cell in the modeling domain for a large number of chemical 

species that act as primary pollutants or precursors to secondary pollutants. The annual 

emission inventories, described in Section 3.2.2, were preprocessed into CMAQ-ready inputs 

using the SMOKE emissions preprocessing system. Meteorological inputs reflecting 2005 

conditions across the contiguous U.S. were derived from Version 5 of the Mesoscale Model 

(MM5). These inputs included hourly-varying horizontal wind components (i.e., speed and 

direction), temperature, moisture, vertical diffusion rates, and rainfall rates for each grid cell in 

each vertical layer. Details of the annual 2005 meteorological modeling are provided in the Air 

Quality Modeling Technical Support Document: Final EGU NESHAP (EPA, 2011d).

The lateral boundary and initial species concentrations for the CMAQ simulations using 

a 36 km domain are provided by a three dimensional global atmospheric chemistry and 

transport model (GEOS-CHEM). The lateral boundary species concentrations varied with height 

and time (every 3 hours). These data were used in CMAQ for the 36 km domain. Initial and 
3-4

boundary concentrations from the CMAQ 36 km domain were then used to provide initial and 

boundary concentrations for CMAQ simulations using the East and West 12 km domains. The 

development of model inputs is discussed in greater detail in the Air Quality Modeling Technical 

Support Document: Final EGU NESHAP (EPA, 2011d).

3.2.1.3 Air Quality Model Evaluation

An operational model performance evaluation for PM2.5 and its related speciated 

components (e.g., sulfate, nitrate, elemental carbon, organic carbon) was performed to 

estimate the ability of the CMAQ modeling system to replicate 2005 base year concentrations. 

This evaluation principally comprises statistical assessments of model predictions versus 

observations paired in time and space on an hourly, 24-hour, or weekly basis depending on the 

sampling period of measured data. Details on the evaluation methodology and the calculation 

of performance statistics are provided in the Air Quality Modeling Technical Support Document: 

Final EGU NESHAP (EPA, 2011d). Overall, the model performance statistics for sulfate, nitrate, 

organic carbon, and elemental carbon from the CMAQ 2005 simulation are within or close to 

the ranges found in other recent applications. These model performance results give us 

confidence that our applications of CMAQ using this 2005 modeling platform provide a 

scientifically credible approach for assessing PM2.5 concentrations for the purposes of the RIA.

3.2.2 Emissions Inventory

The future-year base-case inventory, projected from the 2005 Version 4.3 emissions 

modeling platform, is the starting point for the baseline and control strategy for the Proposed 

PM NAAQS emissions inventory. The Emissions Modeling for the Final Mercury and Air Toxics 

Standard (MATS) TSD (EPA, 2011c) describes in detail the development of the 2005 base year 

inventory, the projection methodology, and the controls applied to create the projected 

inventory. Note that the referenced Emissions Modeling TSD describes the use of year 2015 

emissions for EGUs and 2017 emissions for other sources, while this analysis used 2020 

emissions for EGUs.

The EGU projected inventory represents demand growth, fuel resource availability, 

generating technology cost and performance, and other economic factors affecting power 

sector behavior. It also reflects environmental rules and regulations, consent decrees and 

settlements, plant closures, and newly built units for the calendar year 2020. In this analysis, 

the projected EGU emissions include the Final MATS policy case announced on December 21, 

2011 and the Final Cross-State Air Pollution Rule (CSAPR) issued on July 6, 2011. The EGU 

emissions were developed using version 4.10 Final MATS version of the Integrated Planning 
3-5

Model (IPM) and documented in detail at http://www.epa.gov/airmarkt/progsregs/epaipm/toxics.html. The IPM is a multiregional, dynamic, deterministic linear programming model 

of the U.S. electric power sector. Note that for this analysis, no further EGU control measures 

were selected for illustrating attainment of the current and proposed alternative standard 

levels, as discussed in Chapter 4, and the EGU emissions are unchanged between the futureyear base-case and control strategies.

The mobile source emissions were projected to 2017 using activity data. These 

emissions represent the effects of the Clean Air Nonroad Diesel Rule, the Light-Duty Vehicle 

Tier 2 Rule, the Heavy Duty Diesel Rule, and other finalized rules. Table 3-2 provides a 

comprehensive list of the rules/control strategies and projection assumptions in the projected 

base-case (i.e., reference case) inventory. A full discussion of the future year base inventory is 

provided in the Emissions Modeling TSD. The 2017 onroad mobile source emissions were 

developed by using the MOtor Vehicle Emission Simulator (MOVES)2 to create emission factors 

that were then input to the Sparse Matrix Operator Kernel Emissions system (SMOKE). The 

SMOKE-MOVES Integration Tools combined the county and temperature-specific emission 

factors with the activity data to compute the actual emissions based on hourly gridded 

temperature data.

The future year scenarios include the same year 2006 Canada and year 1999 Mexico 

emissions as the 2005 base case. All 2005 and projected base case emissions inventories are 

available on the EPA’s Emissions Modeling Clearinghouse website at: 

http://www.epa.gov/ttn/chief/emch/index.html#toxics. The inventories used to support this 

analysis can be found under ftp://ftp.epa.gov/EmisInventory/2005v4_3/mats.

 2

More information is available online at: http://www.epa.gov/otaq/models/moves/index.htm
3-6

Table 3-2. Control Strategies and Growth Assumptions for Creating 2020 Base Case 

Emissions Inventories from the 2005 Base Case

Control Strategies and/or Growth Assumptions

(Grouped by Affected Pollutants or Standard and Approach Used to Apply 

to the Inventory)

Pollutants 

Affected

Approach 

or 

Reference:

Non-EGU Point (ptnonipm) Controls

MACT rules, national, VOC: national applied by SCC, MACT

Boat Manufacturing

Wood Building Products Surface Coating

Generic MACT II: Spandex Production, Ethylene manufacture

Large Appliances

Miscellaneous Organic NESHAP (MON): Alkyd Resins, Chelating Agents, 

Explosives, Phthalate Plasticizers, Polyester Resins, Polymerized Vinylidene 

Chloride

Reinforced Plastics

Asphalt Processing & Roofing

Iron & Steel Foundries

Metal: Can, Coil

Metal Furniture

Miscellaneous Metal Parts & Products

Municipal Solid Waste Landfills

Paper and Other Web

Plastic Parts

Plywood and Composite Wood Products

Carbon Black Production

Cyanide Chemical Manufacturing

Friction Products Manufacturing

Leather Finishing Operations

Miscellaneous Coating Manufacturing

Organic Liquids Distribution (Non-Gasoline)

Refractory Products Manufacturing

Sites Remediation

VOC EPA, 

2007a

Consent decrees on companies (based on information from the Office of 

Enforcement and Compliance Assurance—OECA) apportioned to plants 

owned/operated by the companies

VOC, CO, NOx, 

PM, SO2

1

DOJ Settlements: plant SCC controls for:

Alcoa, TX 

Premcor (formerly Motiva), DE 

All 2

Refinery Consent Decrees: plant/SCC controls NOx, PM, SO2 3

(continued)
3-7

Table 3-2. Control Strategies and Growth Assumptions for Creating 2020 Base Case 

Emissions Inventories from the 2005 Base Case (continued)

Control Strategies and/or Growth Assumptions

(Grouped by Affected Pollutants or Standard and Approach Used to Apply 

to the Inventory)

Pollutants 

Affected

Approach 

or 

Reference:

Non-EGU Point (ptnonipm) Controls (continued)

Hazardous Waste Combustion PM 4

Municipal Waste Combustor Reductions—plant level PM 5

Hospital/Medical/Infectious Waste Incinerator Regulations NOX, PM, SO2 EPA, 2005

Large Municipal Waste Combustors—growth applied to specific plants All (including Hg) 5

MACT rules, plant-level, VOC: Auto Plants VOC 6

MACT rules, plant-level, PM & SO2: Lime Manufacturing PM, SO2 7

MACT rules, plant-level, PM: Taconite Ore PM 8

Livestock Emissions Growth from year 2002 to year 2017 (some farms in the 

point inventory) NH3, PM 9

NESHAP: Portland Cement (09/09/10)—plant level based on Industrial Sector 

Integrated Solutions (ISIS) policy emissions in 2013. The ISIS results are from 

the ISIS-Cement model runs for the NESHAP and NSPS analysis of July 28, 

2010 and include closures.

Hg, NOX, SO2, PM, 

HCl

10; EPA, 

2010

New York ozone SIP controls VOC, NOX, HAP 

VOC 11

Additional plant and unit closures provided by state, regional, and the EPA 

agencies and additional consent decrees. Includes updates from CSAPR 

comments.

All 12

Emission reductions resulting from controls put on specific boiler units (not 

due to MACT) after 2005, identified through analysis of the control data 

gathered from the Information Collection Request (ICR) from the 

Industrial/Commercial/Institutional Boiler NESHAP.

NOX, SO2, HCl Section 

4.2.13.2

Reciprocating Internal Combustion Engines (RICE) NESHAP NOX, CO, PM, SO2 13

Ethanol plants that account for increased ethanol production due to RFS2 

mandate All 14

State fuel sulfur content rules for fuel oil—effective only in Maine, New 

Jersey, and New York SO2 15

Nonpoint (nonpt sector) Projection Approaches

Municipal Waste Landfills: projection factor of 0.25 applied All EPA, 

2007a

(continued)
3-8

Table 3-2. Control Strategies and Growth Assumptions for Creating 2020 Base Case 

Emissions Inventories from the 2005 Base Case (continued)

Control Strategies and/or Growth Assumptions

(Grouped by Affected Pollutants or Standard and Approach Used to Apply 

to the Inventory)

Pollutants 

Affected

Approach 

or 

Reference:

Nonpoint (nonpt sector) Projection Approaches (continued)

Livestock Emissions Growth from year 2002 to 2017 NH3, PM 9

New York, Connecticut, and Virginia ozone SIP controls VOC 11, 16

RICE NESHAP NOX, CO, VOC, 

PM, SO2

13

State fuel sulfur content rules for fuel oil—effective only in Maine, New 

Jersey, and New York

SO2 15

Residential Wood Combustion Growth and Change-outs from year 2005 to 

2017 

All 17

Gasoline and diesel fuel Stage II refueling via MOVES2010a month-specific 

inventories for 2017 with assumed RFS2 and LDGHG fuels

VOC, Benzene, 

Ethanol 18

Portable Fuel Container Mobile Source Air Toxics Rule 2 (MSAT2) inventory 

growth and control from year 2005 to 2017 

VOC 19

Phase II WRAP 2018 Oil and Gas VOC, SO2, NOX, 

CO

EM TSD

2008 Oklahoma and Texas Oil and Gas, and apply year 2017 projections for 

TX, and RICE NESHAP controls to Oklahoma emissions.

VOC, SO2, NOX, 

CO, PM

EM TSD

Approaches/References—Non-EGU Stationary Sources:

1. Appendix B in the MATS Proposal TSD: 

http://www.epa.gov/ttn/chief/emch/toxics/proposed_toxics_rule_appendices.pdf

2. For Alcoa consent decree, used http://cfpub.epa.gov/compliance/cases/index.cfm; for Motiva: used 

information sent by State of Delaware

3. Used data provided by the EPA, OAQPS, Sector Policies and Programs Division (SPPD).

4. Obtained from Anne Pope, the US EPA—Hazardous Waste Incinerators criteria and hazardous air pollutant 

controls carried over from 2002 Platform, v3.1.

5. Used data provided by the EPA, OAQPS SPPD expert.

6. Percent reductions and plants to receive reductions based on recommendations by rule lead engineer, and 

are consistent with the reference: EPA, 2007a

7. Percent reductions recommended are determined from the existing plant estimated baselines and 

estimated reductions as shown in the Federal Register Notice for the rule. SO2 percent reduction are 

computed by 6,147/30,783 = 20% and PM10 and PM2.5 reductions are computed by 3,786/13,588 = 28%

8. Same approach as used in the 2006 Clean Air Interstate Rule (CAIR), which estimated reductions of “PM 

emissions by 10,538 tpy, a reduction of about 62%.” Used same list of plants as were identified based on 

tonnage and SCC from CAIR: http://www.envinfo.com/caain/June04updates/tiop_fr2.pdf

(continued)
3-9

Table 3-2. Control Strategies and Growth Assumptions for Creating 2020 Base Case 

Emissions Inventories from the 2005 Base Case (continued)

Control Strategies and/or Growth Assumptions

(Grouped by Affected Pollutants or Standard and Approach Used to Apply 

to the Inventory)

Pollutants 

Affected

Approach 

or 

Reference:

Nonpoint (nonpt sector) Projection Approaches (continued)

Approaches/References—Non-EGU Stationary Sources (continued):

9. Except for dairy cows and turkeys (no growth), based on animal population growth estimates from the US 

Department of Agriculture (USDA) and the Food and Agriculture Policy and Research Institute. See 

Section 4.2.10.

10. Data files for the cement sector provided by Elineth Torres, the EPA-SPPD, from the analysis done for the 

Cement NESHAP: The ISIS documentation and analysis for the cement NESHAP/NSPS is in the docket of that 

rulemaking-docket # EPA-HQ-OAR-2002-005. The Cement NESHAP is in the Federal Register: September 9, 

2010 (Volume 75, Number 174, Page 54969-55066

11. New York NOX and VOC reductions obtained from Appendix J in NY Department of Environmental 

Conservation Implementation Plan for Ozone (February 2008): 

http://www.dec.ny.gov/docs/air_pdf/NYMASIP7final.pdf.

12. Appendix D of Cross-State Air Pollution Rule: 

ftp://ftp.epa.gov/EmisInventory/2005v4_2/transportrulefinal_eitsd_appendices_28jun2011.pdf

13. Appendix F in the Proposed (Mercury and Air) Toxics Rule TSD: 

http://www.epa.gov/ttn/chief/emch/toxics/proposed_toxics_rule_appendices.pdf

14. The 2008 data used came from Illinois’ submittal of 2008 emissions to the NEI.

15. Based on available, enforceable state sulfur rules as of November, 2010: 

http://www.ilta.org/LegislativeandRegulatory/MVNRLM/NEUSASulfur%20Rules_09.2010.pdf, 

http://www.mainelegislature.org/legis/bills/bills_124th/billpdfs/SP062701.pdf, 

http://switchboard.nrdc.org/blogs/rkassel/governor_paterson_signs_new_la.html, 

http://green.blogs.nytimes.com/2010/07/20/new-york-mandates-cleaner-heating-oil/

16. VOC reductions in Connecticut and Virginia obtained from CSAPR comments.

17. Growth and Decline in woodstove types based on industry trade group data, See Section 4.2.11.

18. MOVES (2010a) results for onroad refueling including activity growth from VMT, Stage II control programs 

at gasoline stations, and phase in of newer vehicles with onboard Stage II vehicle controls. 

http://www.epa.gov/otaq/models/moves/index.htm

19. VOC, benzene, and ethanol emissions for 2017 based on MSAT2 rule and ethanol fuel assumptions (EPA, 

2007b)

Onroad Mobile and Nonroad Mobile Controls 

(list includes all key mobile control strategies but is not exhaustive)

National Onroad Rules:

Tier 2 Rule: Signature date February, 2000

2007 Onroad Heavy-Duty Rule: February, 2009

Final Mobile Source Air Toxics Rule (MSAT2): February, 2007

Renewable Fuel Standard: March, 2010

Light Duty Greenhouse Gas Rule: May, 2010

Corporate Average Fuel Economy standards for 2008–2011

All 1

(continued)
3-10

Table 3-2. Control Strategies and Growth Assumptions for Creating 2020 Base Case 

Emissions Inventories from the 2005 Base Case (continued)

Control Strategies and/or Growth Assumptions

(Grouped by Affected Pollutants or Standard and Approach Used to Apply 

to the Inventory)

Pollutants 

Affected

Approach 

or 

Reference:

Onroad Mobile and Nonroad Mobile Controls 

(list includes all key mobile control strategies but is not exhaustive) 

(continued)

Local Onroad Programs:

National Low Emission Vehicle Program (NLEV): March, 1998

Ozone Transport Commission (OTC) LEV Program: January, 1995

VOC 2

National Nonroad Controls:

Clean Air Nonroad Diesel Final Rule—Tier 4: June, 2004

Control of Emissions from Nonroad Large-Spark Ignition Engines and 

Recreational Engines (Marine and Land Based): “Pentathalon Rule”: 

November, 2002

Clean Bus USA Program: October, 2007

Control of Emissions of Air Pollution from Locomotives and Marine 

Compression-Ignition Engines Less than 30 Liters per Cylinder: October, 2008

Locomotive and marine rule (May 6, 2008)

Marine SI rule (October 4, 1996)

Nonroad large SI and recreational engine rule (November 8, 2002)

Nonroad SI rule (October 8, 2008)

Phase 1 nonroad SI rule (July 3, 1995)

Tier 1 nonroad diesel rule (June 17, 2004)

All 3,4,5

Aircraft (emissions are in the nonEGU point inventory):

Itinerant (ITN) operations at airports to 2017 

All 6

Locomotives:

Energy Information Administration (EIA) fuel consumption projections for 

freight rail

Clean Air Nonroad Diesel Final Rule—Tier 4: June 2004

Locomotive Emissions Final Rulemaking, December 17, 1997

Locomotive rule: April 16, 2008

Control of Emissions of Air Pollution from Locomotives and Marine: May 

2008

All EPA, 2009; 

3; 4; 5

(continued)
3-11

Table 3-2. Control Strategies and Growth Assumptions for Creating 2020 Base Case 

Emissions Inventories from the 2005 Base Case (continued)

Control Strategies and/or Growth Assumptions

(Grouped by Affected Pollutants or Standard and Approach Used to Apply 

to the Inventory)

Pollutants 

Affected

Approach 

or 

Reference:

Onroad Mobile and Nonroad Mobile Controls 

(list includes all key mobile control strategies but is not exhaustive) 

(continued)

Commercial Marine:

Category 3 marine diesel engines Clean Air Act and International Maritime 

Organization standards (April, 30, 2010)—also includes CSAPR comments.

EIA fuel consumption projections for diesel-fueled vessels

Clean Air Nonroad Diesel Final Rule—Tier 4

Emissions Standards for Commercial Marine Diesel Engines, December 29, 

1999

Locomotive and marine rule (May 6, 2008)

Tier 1 Marine Diesel Engines, February 28, 2003

All 7, 3; EPA, 

2009

Approaches/References—Mobile Sources

1. http://epa.gov/otaq/hwy.htm

2. Only for states submitting these inputs: http://www.epa.gov/otaq/lev-nlev.htm

3. http://www.epa.gov/nonroad-diesel/2004fr.htm

4. http://www.epa.gov/cleanschoolbus/

5. http://www.epa.gov/otaq/marinesi.htm

6. Federal Aviation Administration (FAA) Terminal Area Forecast (TAF) System, January 2010: 

http://www.apo.data.faa.gov/main/taf.asp

7. http://www.epa.gov/otaq/oceanvessels.htm

3.3 Modeling Results and Analyses

The air quality modeling results were used in the RIA to estimate future-year PM2.5

concentrations for the 2020 base case and to calculate the air quality ratios that were used to 

determine potential control scenarios designed to attain the current and proposed alternative 

NAAQS. These data are then used to estimate the costs and benefits of attaining these current 

and proposed NAAQS levels. Consistent with EPA guidance (EPA, 2007), the air quality modeling 

results are applied in a relative sense to estimate 2020 future-year design values for PM2.5 and 

visibility for the base case as described in Sections 3.3.1.1 and 3.3.2.1. Air quality ratios are 

calculated using the changes in the 2005 and 2020 base case design values and emissions as 

described in Section 3.3.1.2. The data are then used to estimate the tons of emissions 

reductions needed to show attainment of the current and alternative NAAQS levels as 
3-12

described in Section 3.3.1.3 and in Chapter 4. Based on the tons of emissions needed in each 

county, annual standard design values are calculated for attaining the current and alternative 

standard levels for input into the benefits assessment as described in Section 3.3.1.4. 

Limitations of this approach are described in Section 3.3.1.5.

Additional data were also processed to calculate visibility design values for the 2020 

base case. Details on this post-processing are discussed in Section 3.3.2.

3.3.1 PM2.5

As discussed in Chapter 1, this RIA evaluates the costs and benefits of attaining four 

alterative combinations of standards relative to meeting the current primary PM2.5 standards 

(15/35). The five alterative combinations of standards evaluated are: an annual standard level 

of 14 μg/m3 in conjunction with retaining the current 24-hour standard level at 35 μg/m3

(14/35); an annual standard level of 13 μg/m3 in conjunction with retaining the current 24-hour 

standard level at 35 μg/m3 (13/35); an annual standard level of 12 μg/m3 in conjunction with 

retaining the current 24-hour standard level at 35 μg/m3 (12/35); an annual standard level of 11 

μg/m3 in conjunction with retaining the current 24-hour standard level at 35 μg/m3 (11/35); 

and an annual standard level of 11 μg/m3 in conjunction with a 24-hour standard level of 30 

μg/m3 (11/30). We modeled to project future-year PM2.5 concentrations for a 2020 base case 

using CMAQ and then estimated the air quality concentrations for meeting 15/35, 14/35, 

13/35, 12/35, 11/35 and 11/30 using air quality ratios.

3.3.1.1 Calculating Future-year Design Values for 2020 Base Case

To estimate costs of attaining the alternative NAAQS, we use air quality modeling results 

to predict the impact of the control strategies on future-year attainment. This is done by using 

the air quality model results in a relative sense, as recommended by the EPA modeling guidance 

(EPA, 2007), and estimating future-year PM2.5 relative reduction factors (RRFs). RRFs are ratios 

that are calculated from the changes in PM2.5 species concentrations between recent-year and 

future-year air quality modeling results. RRFs are calculated for each PM2.5 component. Futureyear estimates of the PM2.5 annual and 24-hour standard design values at monitor locations are 

then calculated by applying the species-specific RRFs to ambient PM2.5 concentrations from the 

IMPROVE Network, the Speciated Trends Network (STN), and the Federal Reference Method 

(FRM) Network.

To more easily apply this methodology, EPA has created software, called Modeled 

Attainment Test Software (MATS) (Abt, 2010), to calculate future-year PM2.5 annual and 24-

hour standard design values. For this RIA, the RRFs are based on the changes in modeled 
3-13

concentrations between the 2005 and 2020 base case. Ambient measurements used in MATS 

are from IMPROVE and STN sites for 2004–2006 and FRM sites for 2003–2007. Output from 

MATS includes the projected future-year annual and 24-hour standard design values, as well as 

percentage sulfate, nitrate, ammonium, elemental carbon, organic carbon and crustal matter 

contributing to the annual and 24-hour standard design values for each site. These data are 

useful to better understand the PM species contributing to high PM2.5 concentrations and to 

help determine what control measures might be most effective in reducing the future-year 

design values to the proposed levels. Annual and 24-hour standard design values for 2005 and 

2020 base case are discussed in Chapter 4 and shown in Appendix 4.

3.3.1.2 Calculating Future-year Design Values for Meeting the Current Standard and Proposed 

Alternative Standard Levels

To estimate the tons of emissions reductions needed to reach attainment of the current 

and proposed alternative standard levels, we calculated air quality ratios based on how 

modeled concentrations changed with changes in emissions between a recent year of air 

quality, 2005, and the future year of air quality, 2020. These air quality ratios represent an 

estimate of how the annual standard design value at a monitor would change in response to 

emissions reductions of SO2, NOx, or direct PM2.5. Below are the details of how these air quality 

ratios were estimated.

To calculate the air quality ratios for changes in response to emissions reductions of SO2

and NOx we used the following methodology.

Step 1: The speciated changes in annual standard design values between 20053 and 

2020 were obtained from the MATS (Abt, 2010) output files. For each monitor, we computed 

the percent change in the NH4SO4 and NH4NO3

4 components of the annual standard design 

value between 2005 and 2020, relative to the 2005 monitor annual standard design value.

Step 2: For NH4SO4

1 and NH4NO33 components, we computed the change in emissions of 

SO2 and NOx used in the air quality modeling for the 2005 and 2020 base case for groups of 

 3

As described previously in this section, the “2005” annual design values are based on ambient measurements 

used in MATS from IMPROVE and STN sites for 2004–2006 and FRM sites for 2003–2007. These years of 

ambient measurements were selected since they frame the air quality model year of 2005. Because the air 

quality model is used to predict the change in design values between recent and projected future year air 

quality, with the modeled RRFs being applied to the recent year measured design values, it is important to 

select ambient measurement years that include the model year to allow a more true prediction of the future 

year air quality. 4

The NH4SO4 and NH4NO3 components are computed using the SO4, NO3, NH4 and water fraction from MATS as 

described in EPA guidance (EPA, 2007).
3-14

adjacent counties. This larger grouping of counties allowed us to better represent the more 

regional nature of NH4SO4 and NH4NO3 formation and transport. These groupings of counties 

were selected by including all counties within a state that bordered a county with a monitor 

above the current or proposed alternative standard levels. For the state of California, where 

these groupings could have expanded to include most of the counties within the state if we had 

used the same selection criteria, we determined smaller groupings to more realistically 

represent the area around a monitor from which emissions reductions would most influence 

changes in the design value. This smaller grouping was also done for counties in Utah5. These 

groups are listed in Appendix 4, Table 4.A-5.

Step 3: Using the data from Steps 1 and 2, we computed the percent change in the 

NH4SO4 component of the annual standard design value at each monitor per reduction of 1000 

tons of SO2 emissions in the surrounding counties between the 2005 and 2020 base case air 

quality and emissions data. Similarly, we computed the percent change in the annual standard 

NH4NO3 component of the design value at each monitor per change in 1000 tons of NOx 

emissions in the surrounding counties.

Step 4: The data from Step 3 are then used to compute the median value for all 

monitors within the grouping of counties of the percent change in the NH4SO4 and NH4NO3

components of the annual standard design value per change in tons of SO2 and NO3 emissions, 

respectively. This gives us an estimate for each grouping of monitors that indicates the

response of the sulfate and nitrate components of the annual standard design values to 

changes in SO2 and NOx emissions, relative to the PM2.5 speciation at the monitor.

Step 5: The percent change values from Step 4 are then multiplied by the NH4SO4 and 

NH4NO3 speciation values at each monitor in the 2020 base case to produce the “air quality 

ratios.” These data give an estimate of how the annual standard design value (μg/m3

) at a 

monitor would change if 1000 tons of SO2 and/or NOx emissions were reduced in the county in 

which the monitor is located.

To calculate the air quality ratios for changes in response to emissions reductions of 

direct PM2.5 we follow the following methodology.

 5 To determine the counties for the smaller groupings in California and Utah, we simply grouped counties together 

geographically with a minimum of two counties allowed in each of the smaller groupings. 
3-15

Step 1: The speciated changes in annual standard design values between 20056 and 

2020 were obtained from the MATS (Abt, 2010) output files. For each monitor, we computed 

the percent change in the direct PM2.5

7 components of the annual standard design value 

between 2005 and 2020, relative to 2005 monitor annual standard design value.

Step 2: We computed the change in emissions of direct PM2.5 in the emissions inventory 

data used in the air quality modeling for the 2005 and 2020 base case for each county.

Step 3: Using the data from Steps 1 and 2, we computed the percent change in the 

annual standard direct PM2.5 component of the design value at each monitor per change in tons 

of direct PM2.5 emissions at the county level.

Step 4: The data from Step 3 are then used to compute the median value of the percent

change in the PM2.5 component of the annual standard design value per change in tons of direct 

PM2.5 emissions for all monitors within the grouping of counties used to compute the SO2 and 

NOx air quality ratios (see Appendix 4, Table 4.A-5) within a state. We now have an estimate for 

each grouping of monitors that indicates the response of the direct PM2.5 components of the 

annual standard design values to changes in direct PM2.5 emissions, relative to the PM2.5

speciation at each monitor.

Step 5: The percent change values from Step 4 are then multiplied by the direct PM2.5

speciation values at each monitor in the 2020 base case to produce air quality ratios.

Step 6: The responsiveness of air quality at a specific monitor location to direct PM2.5

emission reductions will depend on several factors including the specific meteorology and 

topography in an area and the nearness of the emissions source to the monitor. Because of the 

more local influence of changes in directly emitted PM2.5 emissions on air quality, a monitor 

where significant changes in direct PM2.5 emissions occurred between 2005 and 2020 due to 

sources very close to a monitor can result in large non-representative values in Step 5. A large 

change suggests the monitor is more responsive to PM2.5 emissions reductions than it actually 

 6

As described previously in this section, the “2005” annual design values are based on ambient measurements 

used in MATS from IMPROVE and STN sites for 2004–2006 and FRM sites for 2003–2007. These years of 

ambient measurements were selected since they frame the air quality model year of 2005. Because the air 

quality model is used to predict the change in design values between recent and projected future year air 

quality, with the modeled RRFs being applied to the recent year measured design values, it is important to 

select ambient measurement years that include the model year to allow a more true prediction of the future 

year air quality. 7

The direct PM2.5 design value component is computed by summing the elemental carbon, organic carbon and

crustal portions of the design value.
3-16

would be if those reductions were applied further away from the monitor. Given that the air 

quality ratios must be applicable to multiple monitors across each county and must be 

applicable for emissions reductions where we may not know the specific source location (e.g., 

extrapolated emissions reductions), the air quality ratios we employ should not be strongly 

influenced by very local emissions changes which may have a much larger, non-representative 

impact on air quality at the nearby monitor. To remedy this and obtain representative values 

for air quality ratios, we separated all the counties for which PM2.5 air quality ratios were 

computed (as shown in Table 4.A-10) into four areas of the country: East, West, Northern

California, and Southern California as shown in Table 3-38. We then computed a single 

“trimmed” median PM2.5 ratio for each of the four areas after removing the highest ten percent 

of the values in each area. That is, we calculated the median value of all the PM2.5 air quality 

ratios in each area over counties for which air quality ratios had been calculated after the 

highest ten percent of the values were removed. The resulting PM2.5 air quality ratios that are 

used for all monitors in the four areas are shown in Table 3-3. These data give an estimate of 

how the annual standard design value (μg/m3) at a monitor would change if 1000 tons of direct 

PM2.5 emissions were reduced in the county in which the monitor is located.

Table 3-3. Area Definitions and PM2.5 Air Quality Ratios

Area States and Counties Included

PM2.5 Air Quality Ratio 

(μg/m3 Change in Direct 

PM2.5 per 1,000 Tons PM)

East Alabama, Georgia, Illinois, Michigan, New York, Ohio, 

Pennsylvania, and Texas (all counties with air quality ratios)

1.238

West Arizona, Idaho, Montana, Oregon, Utah, and Washington (all 

counties with air quality ratios)

1.929

Northern California Butte, Colusa, Contra Costa, Fresno, Inyo, Kern, Kings, Merced, 

Monterey, Placer, Plumas, Sacramento, San Joaquin, San Luis 

Obispo, Santa Clara, Solano, Stanislaus, Sutter, Tulare, and Yolo, 

California

1.879

Southern California Imperial, Los Angeles, Orange, Riverside, San Bernardino, San 

Diego, and Ventura, California

0.597

To be able to estimate how the 24-hour standard design value would change in 

response to a lower annual design value, we computed the ratio of the change in the annual 

 8 California was separated into two areas because of the large number of counties analyzed and because of the 

large differences seen in the PM2.5 air quality ratios for the northern versus the southern counties of California.
3-17

design value to the change in the 24-hour standard design value between 2005 and 2020 base 

case for each monitor, and then use these data to compute the average value for all monitors 

within a state that are included within a grouping shown in Appendix 4, Table 4.A-5. The end 

result is an estimate for each state of the expected change in the 24-hour standard design value 

per 1 μg/m3 change in the annual standard design value. These values varied from state-tostate but in general, a 1 μg/m3 change in the annual standard design value corresponded to a 

2–3 μg/m3 change in the 24-hour standard design value at the same monitor. Tables of these 

values are provided with the air quality ratios in Chapter 4.

3.3.1.3 Estimating Emissions Reductions and Costs of Attaining the Current and Proposed 

Alternative PM2.5 Standards

The air quality ratios described in Section 3.3.1.2 are used to determine the most 

effective control measures for reducing the annual and 24-hour standard design values to 

meeting the current and proposed alternative standard levels. The total amount of SO2, NOx

and/or direct PM2.5 emissions reduced per county, based on the control measures selected for 

each strategy, are then used in conjunction with the air quality ratios to estimate how the 

annual and 24-hour standard design values would change in the counties with emissions 

reductions. The details of control measure selections and their associated costs are described in 

Chapter 4.

3.3.1.4 Estimating Changes in Annual Average PM2.5 for Benefits Inputs

MATS (Abt, 2010) can also provide gridded fields of changes in annual average PM2.5

concentrations for the entire CMAQ 12km domain. MATS does this by calculating RRFs at every 

grid cell within the CMAQ domain for each future-year control scenario, and applying these 

RRFs to ambient data that have been interpolated to cover all grid cells in the modeling 

domain. The basic interpolation technique, called Voronoi Neighbor Averaging (VNA), identifies 

the set of monitors that are nearest to the center of each CMAQ grid cell, and then takes an 

inverse distance squared weighted average of the monitor concentrations. A “fused” spatial 

field is then calculated by adjusting the interpolated ambient data (in each grid cell) up or down 

by a multiplicative factor calculated as the ratio of the modeled concentration at the grid cell 

divided by the modeled concentration at the nearest neighbor monitor locations (weighted by 

distance). We use the 2005 and 2020 base case CMAQ modeling outputs, in conjunction with 

the ambient measurements from the IMPROVE and STN sites for 2004–2006 and FRM sites for 

2003–2007, to create a spatial surface for the 2020 base case.
3-18

To generate spatial surfaces that represent annual average PM2.5 concentrations when 

attaining the current and proposed alternative standard levels for the benefits analysis, we 

need to adjust the 2020 base case spatial surface to reflect attainment of the current and 

alternative standard levels. Given the MATS gridded annual average PM2.5 concentrations for 

the CMAQ 12km domain and projected design values at monitors, the “monitor rollback” 

approach is used to approximate the air quality change resulting from attaining alternative 

NAAQS at each design value monitor. Figure 3-2 depicts the rollback process. This approach 

aims to estimate the change in population exposure associated with attaining an alternate 

NAAQS, relying on data from the existing monitoring network and the inverse distance variant 

of the VNA interpolation method to adjust the CMAQ-modeled concentrations such that each 

area attains the standard alternatives. Using the VNA spatial averaging technique, the annual 

average PM2.5 spatial surface is smoothed to minimize sharp gradients in PM2.5 concentrations 

in the spatial fields due to changes in the monitor concentrations.

3.3.1.5 Limitations of Using Air Quality Ratios

There are important limitations to the methodology of calculating and using air quality 

ratios to predict the response of air quality to emissions changes. The air quality ratios are 

calculated with results from only two CMAQ model runs and are based on the assumption that 

the monitor design values would decrease with additional reductions in emissions of SO2, NOx

and direct PM2.5 in the future similar to how the two CMAQ model runs predicted changes in air 

quality concentrations. The uncertainty of this assumption will increase with increasing 

emissions reductions needed to estimate attainment. In addition, the model response to 

emissions changes are analyzed at a county-level or within a small group of counties, and we 

assume that air quality concentrations at a monitor will decrease linearly with emissions 

reductions in a county (e.g., direct PM2.5 emission reductions) or a group of counties (e.g., SO2

and NOx emissions reductions). Because of the more local influence of changes in directly 

emitted PM2.5 emissions on air quality, it is also particularly difficult for the air quality ratio 

approach to estimate well how the design value at a monitor in a county would respond to 

changes in direct PM2.5 emissions in a county without knowing the location of the source (e.g.,

extrapolated emissions reductions) relative to the location of the monitor.

The exact impact of using this methodology to estimate the emissions reductions 

needed for attainment and the associated effect on the cost and benefits is uncertain and may 

vary from monitor-to-monitor. We do not believe that this methodology tends towards any 

general trend and does not always result in either an underestimation or overestimation of the 

costs and benefits of attaining the proposed alternative standards.
3-19

Figure 3-2. Diagram of Rollback Method

3.3.2 Visibility

As described in the Policy Assessment Document (EPA, 2011a) and Chapter 2 of this RIA, 

the formula for total light extinction (bext) in units of Mm-1 using the original IMPROVE equation 

is:

bext = 3 x f(RH) x [Sulfate] + 3 x f(RH) x [Nitrate] + 4 x [Organic Mass] +

10 x [Elemental Carbon] + 1 x [Fine Soil] + 0.6 x [Coarse Mass] + 10 (3.1)

where the mass concentrations of the components indicated in brackets are in units of μg/m3, 

and f(RH) is the unitless water growth term that depends on relative humidity. The final term in 

the equation is known as the Rayleigh scattering term and accounts for light scattering by the 

Step 2. Rollback monitor design 

values to attain each standard 

alternative

Use modeled air quality data 

to establish ratios between 

design value and air quality 

metric at each monitor.

Step 1. Receive 12 km 

CMAQ baseline air quality 

modeling

Step 3. Interpolate 

incremental reduction 

in design value change 

to 12 km grid using 

VNA in BenMAP

Convert interpolated 

DV change to 

equivalent change in 

metric and adjust 

model grid

Calculate

benefits for 

each 

standard 
3-20

natural gases in unpolluted air. Since IMPROVE does not include ammonium ion monitoring, the 

assumption is made that all sulfate is fully neutralized ammonium sulfate and all nitrate is 

assumed to be ammonium nitrate. Using equation (3.1), light extinction (bext) can then be 

converted into units of deciviews, a scale frequently used in the scientific and regulatory 

literature on visibility.

3.3.2.1 Calculating Future-year Visibility Design Values for 2020 Base Case

The visibility design value calculations are based on 24-hour averages and the 90th

percentile format. To estimate future-year visibility design values, we use the air quality 

modeling results in a relative sense, as recommended by the EPA modeling guidance (EPA, 

2007), and estimate future-year relative reduction factors (RRFs) for each speciated component 

of the light extinction (bext) equation. To be consistent with visibility calculations described in 

the Policy Assessment Document (EPA, 2011a), which focuses on PM2.5 visibility, we do not 

include coarse mass (PM10-2.5) in the calculation. The steps for projecting the future-year 

visibility design values are described below.

Step 1: We extract 24-hour averages of sulfate, nitrate, organic mass, elemental carbon 

and fine soil for the 2020 future-year modeled base case for each CMAQ grid cell in which a STN 

monitor is located. For the assumption that sulfate is fully neutralized and all nitrate is assumed 

to be ammonium nitrate, we multiply 24-hour average sulfate mass by 1.375 and nitrate mass 

by 1.29.

Step 2: For the Regional Haze Program, there exists a gridded file of monthly averaged 

f(RH) climatological mean values.9 Using these data, we assign a f(RH) values to each STN 

monitor for each season10 by averaging the 3 monthly f(RH) values in each season using the 

data from the closest available data point.

Step 3: Using the data from Step 1 &2, we calculate bext for every day in the 2005 

modeled base case using equation (3.1) without the coarse mass component.

Step 4: For every season, we extract the top 10% worst modeled visibility days (i.e., top 

9 days) in 2005 based on their bext values. Using the species concentrations for these nine 

 9

U.S. EPA, Interpolating Relative Humidity Weighting Factors to Calculate Visibility Impairment and the Effects of 

IMPROVE Monitor Outliers, prepared by Science Applications International Corporation, Raleigh, NC, EPA 

Contract No. 68-D-98-113, August 30, 2001. 10Each season is defined as Winter ( Dec, Jan & Feb), Spring (Mar, Apr & May), Summer (Jun, Jul & Aug) and Fall 

(Sep, Oct & Nov).
3-21

maximum bext days, we calculate the average species specific bext value for each season for each 

monitor location.

Step 5: We repeat step 3 for each of the future-year modeled scenario, and extract the 

same calendar days that were selected in step 4 for 2005.

Step 6: Using the data from steps 4 and 5, we calculate the species specific Relative 

Response Factors (RRFs) for each monitor in each season for each of the future-year modeled 

scenario. This is done by dividing the average speciated bext value for the top 10% worse 

visibility days for each season for every monitor in each future-year scenario by the average 

species specific concentration for same the season for every monitor in 2005. In this way, we 

will have an RRF for every monitor for each season for each future-year control scenario.

Step 7: The set of seasonal RRFs for each monitor for each future-year control scenario 

are applied to the corresponding 2004–2006 ambient data11 and the 90th percentile value is 

extracted. The end result is a set of visibility design values for each future-year scenario.

3.3.2.2 Calculating Future-year Visibility Design Values for Meeting the Current and Proposed 

Alternative Standard Levels

It is important to understand how changes in the PM2.5 design values to simulate full 

attainment for each proposed alternative NAAQS will affect visibility design values.

As described in Section 3.3.1.2, we apply a methodology of air quality ratios to estimate 

the emissions reductions needed to meet the current and proposed alternative levels for the 

primary standard for PM2.5. While this methodology can estimate how the emissions reductions 

in each control scenario will affect changes in the future-year annual design values, and the 

corresponding response of the future-year 24-hour design values to these changes in the 

annual design value, it is unable to estimate how each of the PM2.5 species will change with 

these emission reductions. Given that estimating changes in future-year visibility is dependent 

on the IMPROVE equation (3.1) and how the PM2.5 species are projected to change in time, we 

are unable to estimate visibility design values for meeting the current and proposed alternative 

levels for the primary PM2.5 standard.

 11 These years of ambient measurements were selected since they frame the air quality model year of 2005. 

Because the air quality model is used to predict the change in design values between recent and projected 

future year air quality, with the modeled RRFs being applied to the recent year measured design values, it is 

important to select ambient measurement years that include the model year to allow a more true prediction of 

the future year air quality.
3-22

3.3.2.3 Estimating Changes in Visibility for Analyzing Welfare Benefits

The visibility calculations for the welfare benefits assessment are based on 24-hour 

average light extinction (bext) values, averaged over the year and converted to units of 

deciviews. As described in Sections 3.3.2.1 and 3.3.2.2, we calculated the visibility design values 

for the 2020 base case but were unable to estimate how these visibility design values would 

change for meeting the current and proposed alternative levels for the primary PM2.5 standard. 

In this same way, we are unable to estimate the light extinction values for meeting the current 

and proposed alternative levels for the primary PM2.5 standard, which are needed to assess 

welfare benefits.

3.4 References

Abt Associates, 2010. User’s Guide: Modeled Attainment Test Software. 

http://www.epa.gov/scram001/modelingapps_mats.htm.

Appel, K.W., Bhave, P.V., Gilliland, A.B., Sarwar, G., Roselle, S.J., 2008. Evaluation of the 

community multiscale air quality (CMAQ) model version 4.5: Sensitivities impacting 

model performance; Part II—particulate matter. Atmospheric Environment 42, 6057-

6066.

Appel, K.W., Gilliland, A.B., Sarwar, G., Gilliam, R.C., 2007. Evaluation of the Community 

Multiscale Air Quality (CMAQ) model version 4.5: Sensitivities impacting model 

performance Part I—Ozone. Atmospheric Environment 41, 9603-9615.

Byun, D.W., and K.L. Schere. 2006. “Review of the Governing Equations, Computational 

Algorithms, and Other Components of the Models-3 Community Multiscale Air Quality 

(CMAQ) Modeling System.” J. Applied Mechanics Reviews 59(2):51-77.

Pitchford, M., and W. Malm. 1994. “Development and Application of a Standard Visual Index.” 

Atmospheric Environment 28(5): 1049-1054.

Sisler, J.F. July 1996. Spatial and Seasonal Patterns and Long Term Variability of the Composition 

of the Haze in the United States: An Analysis of Data from the IMPROVE Network. Fort 

Collins, CO: Cooperative Institute for Research in the Atmosphere, Colorado State 

University.

U.S. Environmental Protection Agency (EPA). 2007. Guidance on the Use of Models and Other 

Analyses for Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, and 

Regional Haze. Office of Air Quality Planning and Standards, Research Triangle Park, NC.

U.S. Environmental Protection Agency (EPA). 2008. Regulatory Impact Analysis of the Proposed 

Revisions to the National Ambient Air Quality Standards for Lead. Office of Air Quality 

Planning and Standards, Research Triangle Park, NC.
3-23

U.S. Environmental Projections Agency (EPA). 2010. Technical Support Document: Preparation 

of Emissions Inventories for the Version 4, 2005-based Platform, USEPA, July, 2010. Also 

available at: http://www.epa.gov/ttn/chief/emch/index.html#2005.

U.S. Environmental Protection Agency (EPA). 2011a. Policy Assessment for the Review of the 

Particulate Matter National Ambient Air Quality Standards. Office of Air Quality Planning 

and Standards, Research Triangle Park, NC.

U.S. Environmental Projections Agency (EPA). 2011b. Regulatory Impact Analysis for the Final 

Mercury and Air Toxics Standards. Office of Air Quality Planning and Standards, 

Research Triangle Park, NC. EPA-452/R-11-011.

U.S. Environmental Projections Agency (EPA). 2011c. Emissions Modeling for the Final Mercury 

and Air Toxics Standards Technical Support Document. Also available at: 

http://www.epa.gov/ttn/chief/emch/index.html#toxics.

U.S. Environmental Projections Agency (EPA). 2011d. Air Quality Modeling Technical Support 

Document: Final EGU NESHAP. Office of Air Quality Planning and Standards, Research 

Triangle Park, NC. EPA-454/R-11-009.
4-1

CHAPTER 4

CONTROL STRATEGIES

4.1 Synopsis

In order to estimate the costs and benefits of alternative PM2.5 standards, the U.S. EPA 

has analyzed hypothetical control strategies that areas across the country might employ to 

attain alternative more stringent annual standards of 13, 12, and 11 μg/m3 in conjunction with 

retaining the 24-hour standard of 35 μg/m3, as well as an alternative more stringent annual 

standard of 11 μg/m3 in conjunction with an alternative more stringent 24-hour standard of 30 

μg/m3 (referred to as 13/35, 12/35, 11/35, and 11/30). The U.S. EPA also analyzed a 14/35 

alternative standard and determined that all counties would meet such a standard concurrent 

with meeting the existing 15/35 standard at no additional costs and with no additional benefits 

because of significant air quality improvements from the Mercury and Air Toxics Standards 

(MATS), the Cross-State Air Pollution Rule (CSAPR), and other Clean Air Act rules as described in 

Chapter 3, Section 3.2.2. Thus, there is no need to present an analysis of 14/35.

For the purposes of this discussion, it will be helpful to define some terminology. These 

definitions are specific to this analysis:

 Base Case—Emissions projected to the year 2020 reflecting current state and federal 

programs, including the Cross-State Air Pollution Rule and the Mercury and Air 

Toxics Standards. This does not include control programs specifically for the purpose 

of attaining the current PM2.5 standard (15/35).

 Baseline—Emissions projections to the year 2020 reflecting the base case plus 

additional emission reductions needed to reach attainment of the current PM2.5 

Standard (15/35).

 Alternative Standard Analysis—Emission reductions and associated hypothetical 

controls needed to reach attainment of the alternative standards. These reductions 

and controls are incremental to the baseline.

 Design Value—A metric that is compared to the level of the National Ambient Air 

Quality Standard (NAAQS) to determine compliance. Design values are typically used 

to classify nonattainment areas, assess progress towards meeting the NAAQS, and 

develop control strategies. The design value for the annual PM2.5 standard is 

calculated as the 3-year average of annual means for a single monitoring site or a 

group of monitoring sites. The design value for the 24-hour standard is calculated as 

the 3-year average of annual 98th percentile 24-hour average values recorded at 

each monitoring site.
4-2

The U.S. EPA has analyzed the impact that additional emissions controls across 

numerous sectors would have on predicted ambient PM2.5 concentrations incremental to a 

baseline, which includes the current PM2.5 standard as well as other major rules such as CSAPR 

and MATS. Thus, the analysis for a revised standard focuses specifically on incremental 

improvements beyond the current standard and other existing major rules, and uses control 

options that might be available to states for application by 2020. The hypothetical control 

strategies presented in this RIA represent illustrative options for achieving emissions reductions 

to move towards a national attainment of a tighter standard. It is not a recommendation for 

how a tighter PM2.5 standard should be implemented, and states will make all final decisions 

regarding implementation strategies once a final NAAQS has been established.

In order to analyze these hypothetical control strategies incremental to attainment of

the current standard and beyond other existing major rules, the U.S. EPA employed a multistage approach. First, the U.S. EPA identified controls to be included in the base case (e.g., 

reflecting current standard of 15/35) to reflect current state and federal programs. Next 

additional controls were applied to attain the current PM2.5 standard. The current state and 

federal programs combined with the additional controls needed for attainment of the current 

PM2.5 standard make up the baseline for this analysis. Once the baseline was established, we 

applied additional known controls within counties containing a monitor predicted to exceed the 

standard alternatives of 13/35, 12/35, 11/35, and 11/30 so as to bring them into attainment 

with the various alternatives in 2020.1 This chapter presents the hypothetical control strategies 

and the results in 2020 after their application. For most of these alternative standards, 

application of known control measures did not achieve attainment. In such cases, additional 

emission reductions beyond the capability of known controls were estimated in order to reach 

full attainment.

4.2 PM2.5 Control Strategy Analysis

4.2.1 Establishing the Baseline

The RIA is intended to evaluate the costs and benefits of reaching attainment with 

alternative PM2.5 standards. In order to develop and evaluate hypothetical control strategies for 

attaining a more stringent primary standard, it is important to first estimate PM2.5 levels in 

20202 given the current NAAQS standards (15/35) and trends. This scenario is known as the 

 1 Refer to Table 4-2 for details on the number of counties with exceedances and the number of additional counties 

where reductions were applied.
4-3

baseline. Establishing this baseline allows us to estimate the incremental costs and benefits of 

attaining any alternative primary standard.

The baseline includes reductions already achieved as a result of national regulations,

reductions expected prior to 2020 from recently promulgated national regulations3 (i.e., 

reductions that were not realized before 2005 but are expected prior to attainment of the 

current PM standard), and reductions from additional controls which the U.S. EPA estimates 

need to be included to attain the current standard (15/35). Reductions achieved as a result of 

state and local agency regulations and voluntary programs are reflected to the extent that they 

are represented in emission inventory information submitted to the U.S. EPA by state and local 

agencies4. Two steps were used to develop the baseline. First, the reductions expected in 

national PM2.5 concentrations from national rules promulgated prior to this analysis were 

considered (referred to as the base case). Below is a list of some of the major national rules 

reflected in the base case. Refer to Chapter 3, Section 3.2.2 for a more detailed discussion of 

the rules reflected in the base case emissions inventory.

 Light-Duty Vehicle Tier 2 Rule (U.S. EPA, 1999)

 Heavy Duty Diesel Rule (U.S. EPA, 2000)

 Clean Air Nonroad Diesel Rule (U.S. EPA, 2004)

 Regional Haze Regulations and Guidelines for Best Available Retrofit Technology 

Determinations (U.S. EPA, 2005b)

 NOx Emission Standard for New Commercial Aircraft Engines (U.S. EPA, 2005)

 Emissions Standards for Locomotives and Marine Compression-Ignition Engines (U.S. 

EPA, 2008)

 Control of Emissions for Nonroad Spark Ignition Engines and Equipment (U.S. EPA, 

2008)

 C3 Oceangoing Vessels (U.S. EPA, 2010)

 3 The recently proposed Boiler MACT and CISWI reconsiderations are not included in the base case. These rules 

were not yet proposed at the time of this analysis. It is not clear how the geographic scope of this rule will 

match with the counties analyzed for this RIA—the costs may decrease but the magnitude is uncertain. 4 The amendments to the Low Emissions Vehicle Program (LEV-III) in California are not included in the base case. 

This program requires an approval of U.S. EPA via a waiver. At the time of this analysis the waiver had not been 

submitted.
4-4

 Hospital/Medical/Infectious Waste Incinerators: New Source Performance Standards 

and Emission Guidelines: Final Rule Amendments (U.S. EPA, 2009)

 Reciprocating Internal Combustion Engines (RICE) NESHAPs (U.S. EPA, 2010)

 Cross-State Air Pollution Rule (U.S. EPA, 2011)

 Mercury and Air Toxics Standards (U.S. EPA, 2011)

Note that we did not conduct this analysis incremental to controls applied as part of 

previous NAAQS analyses (e.g., O3, NOx, or SO2) because the data and modeling on which these 

previous analyses were based are now considered outdated and are not compatible with the 

current PM2.5 NAAQS analysis. In addition, all control strategies analyzed in NAAQS RIAs are 

hypothetical. Second, because the base case reductions alone were not predicted to bring all 

areas into attainment with the current standard (2 counties are projected to exceed an 

alternative standard of 13/35 and 18 counties are projected to exceed an alternative standard 

of 12/35—see Section 4.2.2.1 for more details), the U.S. EPA used a hypothetical control 

strategy to apply additional known controls to illustrate attainment with the current PM2.5

standard. Additional control measures were used in two sectors to establish the baseline:5 NonElectricity Generating Unit Point Sources (Non-EGUs) and Non-Point Area Sources (Area).

The 2020 baseline for this analysis presents one scenario of future year air quality based 

upon specific control measures, including federal rules such as CSAPR and MATS, years of air 

quality monitoring and emissions data. This analysis presents one illustrative strategy relying on 

the identified federal measures and other strategies that states may employ. States may 

ultimately employ other strategies and/or other federal rules may be adopted that would also 

help in achieving attainment. The U.S. EPA plans to issue the final rule no later than December 

14, 2012 and intends to complete designations two years following promulgation of the final 

rule. Under the Clean Air Act, States are required to submit State implementation plans within 3 

years of the effective date of the designations. The plans are required to show attainment as 

expeditiously as practicable but no later than 5 years following the effective date of the 

designations, with the possibility, in certain cases, of an attainment date up to 10 years from 

the effective date of the designations, considering the severity of air quality concentrations in 

the area and the availability and feasibility of emission control measures. Designations will 

likely be based on air quality data from 2011-2013, but attainment will not occur until 2020 at 

 5 In establishing the baseline, the U.S. EPA selected a set of cost-effective controls to simulate attainment of the 

current PM2.5 standard. These control sets are hypothetical as states will ultimately determine controls as part 

of the SIP process.
4-5

the earliest. Thus EPA’s projections for control costs and benefits focus on the year 2020. The 

number of counties that will be part of the designations process may be different than the 

number of counties projected to exceed as part of this analysis. Refer to Section IX of the 

proposed PM2.5 NAAQS for more details concerning implementation requirements for the 

proposed NAAQS.

Two maps of the country are presented in Figures 4-1 and 4-2, which show the 

predicted concentrations for year 2020 for the 575 counties with PM2.5 annual design values 

and 569 counties with 24-hour design values prior to applying controls to meet the current 

standard of 15/35. Control measures were applied to 14 counties in the baseline analysis to 

meet the current PM2.5 standard.

Figure 4-1. Counties Projected to Exceed the Baseline and Analysis Levels of the PM2.5 Annual 

Standard Alternatives in 2020
4-6

4.2.1.1 Controls Applied in the Baseline

The purpose of identifying and analyzing hypothetical baseline controls for PM2.5 and its 

precursors is to establish a level of emissions associated with ambient concentrations that 

would meet the current PM2.5 standard. The additional known controls included in the baseline 

to simulate attainment with current PM2.5 NAAQS are listed in Table 4-1; details regarding the 

individual controls are provided in Appendix 4.A. Controls were applied to directly emitted 

PM2.5 and the PM2.5 precursors of NOx and SO2 given that nitrate, sulfate, and primary PM2.5 

species usually dominate measured PM2.5 based on speciation data measured at the Chemical 

Speciation Network (CSN) sites. Control measures that directly reduced emissions of PM2.5 were 

determined to be most effective close to the exceeding monitors with NOx and SO2 controls 

supplemented depending upon the monitor speciation data. PM2.5 control measures were

Figure 4-2. Counties Projected to Exceed the Baseline and Analysis Levels of the PM2.5 

24-hour Standard Alternatives in 2020
4-7

applied in the county containing the exceeding monitor for the non-EGU point and area source 

emissions. If additional emission control was needed, SO2 and NOx control measures were 

applied within the county exceeding and any contiguous county.6 Additional control measures 

were not applied to electric generating units (EGUs) due to the extensive nature of controls 

resulting from the inclusion of MATS and CSAPR, and additional controls were not applied to 

mobile sources due to our inability to capture regional reductions using the air quality screening 

methodology employed for this analysis.

 6 Refer to Table 4-2 for details on the number of counties with exceedances and the number of additional counties 

where reductions were applied.
4-8

Table 4-1. Controls Applied in the Baseline for the Current PM2.5 Standard*

Pollutant Control Measure 15/35 12/35 11/35 11/30

NOx Selective Catalytic Reduction (SCR) x x

Non-selective Catalytic Reduction (NSCR) x x x

Oxy-Firing x x x

Bio-solid Injection

SCR + Steam Injection x x x

Low NOx Burners (LNB) x x x

LNB + SCR x x

LNB + Selective Non-catalytic Reduction (SNCR) x

PM2.5 Fabric Filters x x x x

Dry Electrostatic Precipitators (ESPs) x

Wet ESPs x x x

Venturi Scrubbers

SO2 Spray Dryer Absorber (SDA) x x x

Flue Gas Desulfurization (FGD) x x x

Wet FGDs x x x

NOx Water Heater + LNB Space Heaters x x x

Low-NOx Burners for Residential Natural Gas x x x

PM2.5 Fireplace Inserts for Home Heating x x x x

Basic Smoke Management Practices and 

Establishment of Smoke Management Programs for 

Prescribed Burning and other Open Burning** x x x x

Woodstove Advisory Program x x x x

ESPs for Commercial Cooking x x x

SO2 Fuel Switching for Stationary Source Fuel Combustion x x x

Low Sulfur Home Heating Fuel x x x

* As discussed elsewhere in this chapter, no known controls were applied for 14/35 or 13/35.

**Includes specific practices such as episodic bans on open burning, and substituting chipping for open burning.

4.2.2 Alternative Standard Control Strategies

After establishing the baseline of attaining the current standard of 15/35, additional 

emission reductions needed to meet four alternative standards 13/35, 12/35, 11/35, and 11/30 

were calculated.

4.2.2.1 Counties Exceeding Alternative Standards

Only two counties are projected to exceed an alternative standard of 13/35 using the 

results from the baseline analysis. These are Riverside County, CA and San Bernardino County, 

CA. Figures 4-3 through 4-5 show the counties projected to exceed the alternative standards 

12/35, 11/35, and 11/30, respectively. Six counties are projected to exceed an alternative 
4-9

standard of 12/35, eighteen counties are projected to exceed an alternative standard of 11/35, 

and thirty-five counties are projected to exceed an alternative standard of 11/30. For a 

complete list of monitor values see Appendix 4.A.

Figure 4-3. Counties Projected to Exceed the 12/35 ug/m3 Alternative Standard After 

Meeting the Baseline (Current Standard) in 2020
4-10

Figure 4-4. Counties Projected to Exceed the 11/35 ug/m3 Alternative Standard After 

Meeting the Baseline (Current Standard) in 2020
4-11

Figure 4-5. Counties Projected to Exceed the 11/30 ug/m3 Alternative Standard After 

Meeting the Baseline (Current Standard) in 2020

In developing the control strategies for this RIA, the U.S. EPA first applied known 

controls to reach attainment. For these control strategies, controls for two sectors were used in 

developing the control analysis, as discussed previously: non-EGU point and area sources. An 

approach similar to that taken for the baseline analysis was used in the analysis for the control 

strategies for the alternative standards. Due to the lack of air quality modeling for the control 

strategies, county-specific ratios of air quality response to emission reductions were applied 

based on recent air quality modeling results. A least cost framework was adapted to adjust for 

the use of the air quality to emissions ratios.

In this analysis, PM2.5 controls were applied first because they were more cost-effective 

and the air quality ratio approach is generally more accurate for PM2.5 emission changes than 

for emission changes from the precursors, SO2 and NOx. If additional control was needed SO2

and NOx controls were added.
4-12

It should be noted that while PM2.5 controls were applied only within the counties with 

monitors projected to exceed the alternative standard being analyzed, SO2 and NOx controls 

were applied in the exceeding county as well as in the surrounding counties because of the 

transport of NOx and SO2 across counties. Table 4-2 shows the number of exceeding counties 

and the number of surrounding counties to which controls were applied for the alternative 

standards analyzed. For a complete list of geographic areas for all alternative standards see 

Appendix 4.A.

Table 4-2. Number of Counties with Exceedances and Number of Additional Counties 

Where Reductions were Applied

Alternative 

Level

Number of Counties with 

exceedances

Number of Additional Counties where 

reductions were applied

13/35 2 3

12/35 6 25

11/35 18 86

11/30 35 134

There were some areas where known controls did not achieve enough emission 

reductions to attain the alternative annual standards in 2020. To complete the analysis, the U.S. 

EPA then estimated the additional emission reductions required to reach attainment. The 

methodology used to develop those estimates and those calculations are presented in Section 

4.2.3.

4.2.2.2 Non-EGU and Area Controls Applied for Alternative Standards

Non-EGU point and area control measures were identified using the U.S. EPA’s Control 

Strategy Tool7 (CoST). Many of these controls are summarized in Appendix 4.A.

Area source emissions data are generated at the county level, and therefore controls for 

this emission sector were applied to the county. Area source controls were applied to NOx, SO2, 

and PM2.5. Table 4-1 lists the major controls applied to each sector. The same controls that 

were applied in the baseline analysis were applied to additional sources and additional counties 

in the analyses for the alternative standards. Controls for area sources were applied to: home 

heating, restaurant operations, prescribed burning, and other open burning.

 7 See http://www.epa.gov/ttn/ecas/cost.htm for a description of CoST.
4-13

The analysis for non-EGUs applied NOx, SO2, and PM2.5 controls to the following source 

categories: industrial boilers, commercial and institutional boilers, sulfuric acid plants (both 

standalone and at other facilities such as copper and lead smelters), primary metal plants (iron 

and steel mills, lead smelters), mineral products (primarily cement kilns), and petroleum 

refineries. Among the control measures applied were: wet FGD scrubbers and spray dryer 

absorbers (SDA) for SO2 reductions, fabric filters for PM2.5 reductions, and SCR and low NOx

burners for NOx.

To more accurately depict available controls, the U.S. EPA employed a decision rule in 

which controls were not applied to any non-EGU or area sources with 50 tons/year of emissions 

or less. This decision rule is the same rule we employed for sources in the previous PM2.5 

NAAQS RIA completed in 2006. The reason for applying this decision rule is based on a finding 

that most point sources with emissions of this level or less had controls already in place. This 

decision rule helps fill gaps in information regarding existing controls on non-EGU sources.

4.2.2.3 Emission Reductions

Table 4-3 shows the emission reductions from known controls for the alternative 

standards analyzed.

Table 4-3. Emission Reductions from Known Controls for Alternative Standards a

Emission Reductions in 2020 (annual tons/year)

Alternative 

Standard Region PM2.5 SO2 NOx

13/35b East — — —

West — — —

CA — — —

Total — — —

12/35a East 670 — —

West 60 — —

CA — —

Total 730 — —

11/35 East 5,000 12,000 850

West 90 550 620

CA 800 — —

Total 5,900 13,000 1,500

11/30 East 4,700 12,000 850

West 1,900 3,900 7,400

CA 3,700 — —

Total 10,000 16,000 8,200

a Estimates are rounded to two significant figures.

b All known controls were applied in the baseline analysis. Thus, no additional known controls were available.
4-14

4.2.3 Emission Reductions Needed Beyond Identified Controls

For each alternative standard and geographic area that cannot reach attainment with 

known controls, we estimated the additional emission reductions needed beyond identified 

known controls for PM2.5 and for the two PM2.5 precursors (SO2 and NOx) to attain the standard. 

In Appendix 4.A, we provide estimates of the relationship between additional emission 

reductions for each pollutant and air quality improvement.

Because three different pollutants affect ambient levels of PM2.5 in this analysis there 

are many different combinations of pollutant reductions that would result in the required air 

quality improvements. To determine which pollutant reductions to include in our analysis, we 

employ a least cost approach using what we call the hybrid cost methodology. A detailed 

discussion of this methodology appears in Chapter 7. In Appendix 7.A, we show cost estimates 

for each additional emission reduction for each pollutant and geographic area. As expected, the 

unit costs increase under this methodology as more of a particular pollutant is controlled. The 

mix of pollutants controlled, however, varies by area because each area has a different 

combination of known controls applied, varying amounts of additional air quality improvement 

required, and different amounts of uncontrolled emissions remaining.

The process used to determine the emission reductions needed for each pollutant is 

described below. First, the U.S. EPA examined the emissions remaining for each geographic 

area and pollutant (NOx, PM2.5, SO2). Each pollutant has a marginal cost curve that increases 

(e.g., the third ton removed costs more than the second ton removed, and so on). Each 

pollutant has an estimated effectiveness at reducing the ambient concentration of PM2.5 per 

ton of emissions controlled (see Chapter 3 for more details) that varies by geographic area. The 

U.S. EPA used a least cost methodology to determine the optimum way to reach attainment. 

The optimization methodology used to estimate the quantity of PM2.5 and PM2.5 precursors 

needed for each geographic area is described in more detail in Chapter 7 and Appendix 7.A.

Because the marginal cost equation for each pollutant is expected to be less accurate 

for the very last portion of a pollutant in an area, and it is unlikely an area would reduce all 

anthropogenic emissions to zero on one pollutant prior to controlling others, we added the 

constraint that no more than 90% of the remaining emissions in an area for a given pollutant 

can be reduced from emission reductions beyond known control measures. This decision was 

based upon the rationale that no geographic area would be able to eliminate 100% of the 

emissions of a pollutant given current control measures. This methodology used the marginal 

cost curves for each of the three pollutants along with the air quality to emissions response 
4-15

ratios to determine the most cost-effective way to achieve the necessary levels of air quality 

improvement. A detailed discussion of the methodology, including formulas and description of 

how parameters were estimated, can be found in Chapter 7.

The emission reductions needed beyond known controls are shown in Table 4-4. For a 

listing of emission reductions needed by county for the unknown controls, see Appendix 4.A. 

For the alternative standard 13/35 there are only two counties projected to exceed—Riverside 

County, CA and San Bernardino County, CA. For Riverside County, all known controls were 

applied in the analysis to illustrate attainment of the baseline (15/35). Thus, no known controls 

remained for demonstrating attainment of more stringent standards. For the other alternative 

standards (12/35, 11/35, and 11/30), known controls accounted for over 70% of the needed 

emission reductions.

The emissions reductions estimated using the hybrid methodology together with 

reductions associated with known controls form the basis of the cost and benefit estimates. 

However, a different mix of reductions in SO2 emissions and PM2.5 emissions may have been 

identified as least cost using a fixed cost per ton approach rather than the hybrid approach.8

Using the hybrid methodology, the less expensive pollutant to reduce will be selected 

until the marginal cost to reduce the next ton exceeds the marginal cost to reduce the next ton 

of an alternate pollutant. At that point, the methodology chooses a mix of pollutants to achieve 

the least-cost solution. Since the cost per ton is held constant in the fixed-cost methodology, 

the least-cost solution would select all available direct PM2.5 emissions reductions before 

selecting SO2 emissions reductions.9 Therefore, the hybrid methodology estimates PM2.5

emissions reductions lower than or equal to the fixed-cost methodology and SO2 emission 

reductions higher than or equal to the fixed-cost methodology.

Even so, for the proposed 12/35 and 13/35 standards, direct PM2.5 reductions account 

for approximately 75%–100% of the reductions, and thus using the fixed cost per ton approach 

to select the combination of emissions reductions would not have substantially changed the 

mix of emissions reductions or the outcome of the cost and benefit analyses.

 8 NOx reduction were not selected under either approach as the least cost alternative to achieve the necessary 

PM2.5 reductions. 9 Because the marginal cost equation for each pollutant is expected to be less accurate for the very last portion of 

a pollutant in an area, and it is unlikely an area would reduce all anthropogenic emissions to zero on one 

pollutant prior to controlling others, we included the constraint that no more than 90% of the remaining 

emissions in an area for a given pollutant can be reduced from emission reductions beyond known control 

measures.
4-16

That said, the hybrid approach still has a number of important uncertainties, and the 

reliability of the method for extrapolating costs in cases where emissions reductions required 

go well beyond known controls has not been evaluated. The degree of extrapolation for 

emissions reductions in California in particular has caused us to rethink the use of the hybrid 

method in providing a range of cost estimates for the proposed standards, therefore we 

provide the hybrid approach as a sensitivity analysis in Appendix 7.A. We would like to take 

comment on analyzing an alternate compliance pathway for California.

Table 4-4. Emission Reductions Needed Beyond Known Control to Reach Alternative 

Standards in 2020 (annual tons/year)a

Alternative 

Standard Region PM2.5 SO2 NOx

13/35 East — — —

West — — —

CA 190 — —

Total 190 — —

12/35a East — — —

West 210 10 —

CA 3,400 960 —

Total 3,600 970 —

11/35 East 89 — —

West 1,100 1,400 —

CA 6,500 5,500 —

Total 7,700 6,900 —

11/30 East 1,400 — —

West 3,500 1,700 —

CA 7,200 5,500 —

Total 12,000 7,200 —

a Estimates are rounded to two significant figures.

4.3 Limitations and Uncertainties

The U.S. EPA’s analysis is based on its best judgment for various input assumptions that 

are uncertain. As a general matter, the Agency selects the best available information from 

engineering studies of air pollution controls and has set up what it believes is the most 

reasonable modeling framework for analyzing the cost, emission changes, and other impacts of 

regulatory controls. However, the estimates of emission reductions associated with our control 

strategies above are subject to important limitations and uncertainties. We outline, and 
4-17

qualitatively assess the impact of, those limitations and uncertainties that are most significant. 

EPA requests comment on the likelihood that new technologies that control direct PM2.5 and its 

precursors will become available between now and 2020.

A number of limitations and uncertainties are associated with the analysis of emission 

control measures are listed in Table 4-5. For a complete discussion of the terminology used 

below please see Chapter 5.5.7.

Table 4-5. Summary of Qualitative Uncertainty for Elements of Control Strategies

Potential Source of Uncertainty

Direction 

of 

Potential 

Bias

Magnitude 

of Impact 

on 

Monetized 

Costsa

Degree of 

Confidence 

in Our 

Analytical 

Approachb

Ability to 

Assess 

Uncertaintyc

Uncertainties Associated with PM Concentration Changes

Projections of future levels of emissions and emissions 

reductions necessary to achieve the NAAQS

Bothd Medium Medium Tier 1

Responsiveness of air quality model to changes in 

precursor emissions from control scenarios

Both MediumhighMedium Tier 1

Air quality model chemistry, particularly for formation 

of ambient nitrate concentrations

Both Medium High Tier 1

Post-processing of air quality modeled concentrations 

to estimate future-year PM2.5 design value and spatial 

fields of PM2.5 concentrations

Both High High Tier 1

Post-processing of air quality modeled concentrations 

to estimate future-year visibility design value

Both High Medium Tier 1

“Rollback” methodology for simulating full-attainment Both Medium Medium Tier 1

Uncertainties Associated with Control Strategy Development

Control Technology Data

 Technologies applied may not reflect most current 

emerging devices that may be available in future 

years

 Control efficiency data is dependent upon 

equipment being well maintained.

 Area source controls assume a constant estimate of 

emission reductions, despite variability in extent 

and scale of application.

Both MediumhighHigh Tier 2

Control Strategy Development

 States may develop different control strategies 

than the ones illustrated

 Lack of data on baseline controls from current SIPs

Both MediumhighMediumhighTier 0
4-18

 Timing of control strategies may be different than 

envisioned in RIA

 Controls are applied within the county with the 

exceeding monitor. In some cases, additional 

known controls are also applied in adjacent 

contributing counties.

 Emissions growth and control from new sources 

locating in these analysis areas is not included.

Technological Change

 Emission reductions do not reflect potential effects 

of technological change that may be available in 

future years

 Effects of “learning by doing” are no accounted for 

in the emission reduction estimates

Likely overestimateMediumhighLow Tier 0

Emission Reductions from Unidentified Controls

 emission control cut points for each pollutant

Both High Low Tier 1

a Magnitude of Impact

High—If error could influence the total costs by more than 25%

Medium—If error could influence the total costs by 5%–25%

Low—If error could influence the total costs by less than 5%

b Degree of Confidence in Our Analytic Approach

High—The current evidence is plentiful and strongly supports the selected approach

Medium—Some evidence exists to support the selected approach, but data gaps are present

Low—Limited data exists to support the selected approach

c Ability to Assess Uncertainty (using WHO Uncertainty Framework)

Tier 0—Screening level, generic qualitative characterization

Tier 1—Scenario-specific qualitative characterization

Tier 2—Scenario-specific sensitivity analysis

Tier 3—Scenario-specific probabilistic assessment of individual and combined uncertainty

d Future expected emissions are difficult to predict because they depend on many independent factors. Emission 

inventories are aggregated from many spatially and technically diverse sources of emissions, so simplifying 

assumptions are necessary to make estimating the future tractable.

4.4 References

U.S. Environmental Protection Agency (U.S. EPA).1999. Control of Air Pollution from New Motor 

Vehicles: Tier 2 Motor Vehicle Emissions Standards and Gasoline Sulfur Control 

Requirements. Office of Transportation and Air Quality. Available at 

http://www.epa.gov/tier2/frm/fr-t2reg.pdf.

U.S. Environmental Protection Agency (U.S. EPA).2000. Heavy-Duty Engine and Vehicle 

Standards and Highway Diesel Fuel Sulfur Control Requirements. Office of 

Transportation and Air Quality. Available at http://www.epa.gov/otaq/highwaydiesel/index.htm.
4-19

U.S. Environmental Protection Agency (U.S. EPA). 2004. Control of Emissions of Air Pollution 

from Nonroad Diesel Engines and Fuel. Office of Transportation and Air Quality. 

Available at 

http://www.regulations.gov/search/Regs/contentStreamer?objectId=09000064800be20

3&disposition=attachment&contentType=pdf.

U.S. Environmental Protection Agency (U.S. EPA).2005. New Emission Standards for New 

Commercial Aircraft Engines. Office of Transportation and Air Quality. Available at 

http://www.epa.gov/oms/regs/nonroad/aviation/420f05015.htm.

U.S. Environmental Protection Agency (U.S. EPA).2005b. Regional Haze regulations and 

Guidelines for Best Available Retrofit Technology Determinations. Office of Air Quality 

Planning and Standards. Available athttp://www.epa.gov/fedrgstr/EPAAIR/2005/July/Day-06/a12526.pdf and 

http://www.epa.gov/visibility/fs_2005_6_15.html.

U.S. Environmental Protection Agency (U.S. EPA). 2005. Clean Air Interstate Rule. Office of 

Atmospheric Programs. Washington, D.C. Available at 

http://edocket.access.gpo.gov/2005/pdf/05-5723.pdf.

U.S. Environmental Protection Agency (U.S. EPA). 2007. Guidance on the Use of Models and 

other Analyses for Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, 

and Regional Haze. Office of Air Quality Planning and Standards, Research Triangle Park, 

NC. Available at http://www.epa.gov/ttn/scram/guidance/guide/final-03-pm-rhguidance.pdf.

U.S. Environmental Protection Agency (U.S. EPA).2008. Control of Emissions for Nonroad Spark 

Ignition Engines and Equipment. Office of Transportation and Air Quality. Available at 

http://www.epa.gov/otaq/regs/nonroad/marinesi-equipld/bondfrm.pdf.

U.S. Environmental Protection Agency (U.S. EPA).2008. Emissions Standards for Locomotives 

and Marine Compression-Ignition Engines. Office of Transportation and Air Quality. 

Available at http://www.epa.gov/nonroad/420f08004.pdf.

U.S. Environmental Protection Agency (U.S. EPA). 2009. Standards of Performance for New 

Stationary Sources and Emission Guidelines for Existing Sources: 

Hospital/Medical/Infectious Waste Incinerators. Office of Air Quality Planning and 

Standards, Research Triangle Park, NC. Available at 

http://www.epa.gov/ttn/atw/129/hmiwi/fr06oc09.pdf.

U.S. Environmental Protection Agency (U.S. EPA).2010. Control of Emissions from New Marine 

Compression-Ignition Engines at or Above 30 Liters per Cylinder. Office of 

Transportation and Air Quality. Available at 

http://www.regulations.gov/search/Regs/contentStreamer?objectId=0900006480ae43a

6&disposition=attachment&contentType=pdf.
4-20

U.S. Environmental Protection Agency (U.S. EPA). 2011. Control Strategy Tool (CoST) 

Documentation Report. Office of Air Quality Planning and Standards, Research Triangle 

Park, NC. Available at http://www.epa.gov/ttnecas1/cost.htm.

U.S. Environmental Protection Agency (U.S. EPA). 2011. Cross-State Air Pollution Rule. Office of 

Atmospheric Programs. Washington, D.C. Available at 

http://www.gpo.gov/fdsys/pkg/FR-2011-08-08/pdf/2011-17600.pdf.

U.S. Environmental Protection Agency (U.S. EPA). 2011. Mercury and Air Toxics Standards. 

Office of Atmospheric Programs. Washington, D.C. Available at 

www.gpo.gov/fdsys/pkg/FR-2012-02-16/pdf/2012-806.pdf.
4.A-1

APPENDIX 4.A

ADDITIONAL CONTROL STRATEGY INFORMATION

4.A.1 Control Measures for Stationary Sources

This appendix describes measures that were employed in this analysis to illustrate a 

hypothetical scenario for controlling emissions of PM and precursors from non-EGU point and 

area source categories to attain alternative annual and 24-hr air quality standards for PM2.5. 

Most of the control measures available are add-on technologies but some other technologies 

and practices that are not add-on in nature can reduce emissions of PM and PM precursors.

4.A.1.1 PM Emissions Control Technologies1

This section summarizes control measures focused on reduction of PM2.5 from non-EGU 

point and area sources. However, it should be noted that PM10 will also be reduced by these

measures. The amount of PM10 reduction varies by the fraction of PM10 in the inlet stream to 

the control measure and the specific design of the measure.

4.A.1.1.1 PM Control Measures for NonEGU Point Sources

Most control measures for non-EGU point sources are add-on technologies. These 

technologies include: fabric filters (baghouses), ESPs, and wet PM scrubbers. Fabric filters 

collect particles with sizes ranging from below 1 micrometer to several hundred micrometers in 

diameter at efficiencies in excess of 99%, and this device is used where high-efficiency particle 

collection is required. A fabric filter unit consists of one or more isolated compartments 

containing rows of fabric bags in the form of round, flat, or shaped tubes, or pleated cartridges. 

Particle-laden gas passes up (usually) along the surface of the bags then radially through the 

fabric. Particles are retained on the upstream face of the bags, and the cleaned gas stream is 

vented to the atmosphere. The filter is operated cyclically, alternating between relatively long 

periods of filtering and short periods of cleaning. Dust that accumulates on the bags is removed 

from the fabric surface when cleaning and deposited in a hopper for subsequent disposal.

ESPs use electrical forces to move particles out of a flowing gas stream and onto 

collector plates. The particles are given an electrical charge by forcing them to pass through a 

corona, a region in which gaseous ions flow. The electrical field that forces the charged particles 

to the plates comes from electrodes maintained at high voltage in the center of the flow lane. 

Once particles are on the collector plates, they must be removed without re-entraining them 

 1 The descriptions of add-on technologies throughout this section are taken from the EPA Air Pollution Control Cost 

Manual, Sixth Edition. This is found on the Internet at http://epa.gov/ttn/catc/products.html#cccinfo.
4.A-2

into the gas stream. This is usually accomplished by rapping the plates mechanically which 

loosens the collected particles from the collector plates, allowing the particles to slide down 

into a hopper from which they are evacuated. This removal of collected particles is typical of a 

“dry” ESP. A “wet” ESP operates by having a water flow applied intermittently or continuously 

to wash away the collected particles for disposal. The advantage of wet ESPs is that there are 

no problems with rapping re-entrainment or with “back coronas” (unintended injection of 

positively charged ions which reduces the charge on particles and lowers the collection 

efficiency). The disadvantage is that the collected slurry must be handled more carefully than a 

dry product, adding to the expense of disposal. ESPs capture particles with sizes ranging from 

below 1 micrometer to several hundred micrometers in diameter at efficiencies from 95 to up 

to 99% and higher.

Wet PM scrubbers remove PM and acid gases from waste gas streams of stationary 

point sources. The pollutants are removed primarily through the impaction, diffusion, 

interception and/or absorption of the pollutant onto droplets of liquid. The liquid containing 

the pollutant is then collected for disposal. Collection efficiencies for wet scrubbers vary by 

scrubber type, and with the PM size distribution of the waste gas stream. In general, collection 

efficiency decreases as the PM size decreases. Collection efficiencies range from in excess of 

99% for venturi scrubbers to 40% to 60% for simple spray towers. Wet scrubbers are generally 

smaller and more compact than fabric filters or ESPs, and have lower capital cost and 

comparable operation and maintenance (O&M) costs. Wet scrubbers, however, operate with a 

higher pressure drop than either fabric filters or ESPs, thus leading to higher energy costs. In 

addition, they are limited to lower waste gas flow rates and operating temperatures than fabric 

filters or ESPs, and also generate sludge that requires additional treatment or disposal. This RIA 

only applies wet scrubbers to fluid catalytic cracking units (FCCUs) at petroleum refineries.

In addition, we also examined additional add-on control measures specifically for steel 

mills. Virtually all steel mills have some type of PM control measure, but there is additional 

equipment that in many cases could be installed to further reduce emissions. Capture hoods 

that route PM emissions from a blast furnace casthouse to a fabric filter can provide 80% to 

90% additional emission reductions from a steel mill. Other capture and control systems at 

blast oxygen furnaces (BOFs) can also provide 80% to 90% additional reductions.

Table 4.A-1 lists some of these technologies. For more information on these 

technologies, refer to the EPA Air Pollution Control Cost Manual.1
4.A-3

Table 4.A-1. Example PM Control Measures for NonEGU Point Source Categories

Control Measure

Sector(s) to which Control 

Measure Can Apply

Control 

Efficiency 

(percent)

Average 

Annualized 

Cost/Ton

Fabric Filtersa Industrial Boilers, Iron and Steel 

Mills, Pulp and Paper Mills

98 to 99.9 $2,000–$100,000

ESPs—wet or drya Industrial Boilers, Iron and Steel 

Mills, Pulp and Paper Mills

95 to 99.9 $1,000–$20,000

Wet Scrubbers Industrial Boilers, Iron and Steel 

Mills

40 to 99 $750–$2,800

Secondary Capture and Control 

Systems—Capture Hoods for Blast 

Oxygen Furnaces

Coke Ovens 80 to 90 $5,000

CEM Upgrade and Increased 

Monitoring Frequency

NonEGUs with an ESP 5 to 7 $600–$5,000

a CoST contains equations to estimate capital and annualized costs for ESP and FF installation and operation. The 

average annualized cost/ton estimates presented here for these control measures are outputs from our 

modeling, not inputs. They also reflect applications of control where there is no PM control measure currently 

operating except if the control measure is an upgrade (e.g., ESP upgrades).

4.A.1.1.2 PM Control Measures for Area Sources

Specific controls exist for a number of stationary area sources. Area source PM controls 

at stationary sources include:

 catalytic oxidizers on conveyorized charbroilers at restaurants (up to 80% reduction 

of PM),

 replacement of older woodstoves with ones compliant with the New Source 

Performance Standard (NSPS) for residential wood combustion (up to 98% reduction 

of PM2

), and

 education and advisory programs to help users to operate woodstoves more 

efficiently and with fewer emissions (up to 50% reduction of PM)

Another PM area source control measure, diesel particulate filters, can be applied to existing 

diesel-fueled compression-ignition (C-I) engines to achieve up to a 90% reduction in fine PM. 

This measure is being applied to new C-I engines as part of a NSPS that was implemented 

beginning in 2006.

 2 This control measure is largely meant to simulate the effects of a woodstove changeout program as applied to 

Libby, MT per the efforts of the U.S. EPA and several co-sponsors. For more information, refer to 

http://www.epa.gov/woodstoves/how-to-guide.html.
4.A-4

Table 4.A-2. Example PM Control Measures for Area Sourcesa

Control Measures

Sectors to which 

These Control 

Measures Can Apply

Control 

Efficiency 

(percent)

Average 

Annualized 

Cost/ton

Catalytic oxidizers for conveyorized charbroilers Restaurants 83 $1,300

Changeout of older woodstoves for new ones by a 

woodstove changeout campaign or on sale of 

property, or an education and advisory program 

for woodstove users

Residential wood 

combustion sources

46 to near 100 $1,900

Replace open burning of wood waste with 

chipping for landfill disposal

Residential waste 

sources

Near 100 $3,500

a The estimates for these control measures reflect applications of control where there is no PM area source control 

measure currently operating. Also, the control efficiency is for total PM, and thus accounts for PM10 and PM2.5. 

Data for these measures is available in the CoST Control Measures Documentation Report at 

http://www.epa.gov/ttn/ecas/models/CoST_CMDB_Document_2010-06-09.pdf.

4.A.1.2 SO2 Control Measures

4.A.1.2.1 SO2 Control Measures for NonEGU Point Sources

The SO2 emission control measures used in this analysis are similar to those used in the 

PM2.5 RIA prepared about four years ago. Flue gas desulfurization (FGD) scrubbers can achieve 

95–98% control of SO2 for nonEGU point sources and for utility boilers. Spray dryer absorbers 

(SDA) are another commonly employed technology, and SDA can achieve up to 90% or more 

control of SO2. For specific source categories, other types of control technologies are available 

that are more specific to the sources controlled. Table 4.A-3 lists some of these technologies. 

For more information on these technologies, please refer to the CoST control measures 

documentation report.3

 3 For a complete description of the control technologies used in CoST, please refer to the report at 

http://www.epa.gov/ttn/ecas/models/CoST_CMDB_Document_2010-06-09.pdf.
4.A-5

Table 4.A-3. Example SO2 Control Measures for NonEGU Pointa

Control Measure

Sectors to Which These Control 

Measures Can Be Applied

Control 

Efficiency 

(percent)

Average Annualized 

Cost/Ton (2006$)

Wet and Dry FGD 

scrubbers and SDA

ICI boilers—all fuel types, kraft pulp 

mills, Mineral Products (e.g., Portland 

cement plants (all fuel types), primary 

metal plants, petroleum refineries

95—FGD 

scrubbers,

90—for SDA

$800–$8,000—FGD

$900–$7,000—SDA

Increase percentage 

sulfur conversion to meet 

sulfuric acid NSPS (99.7% 

reduction)

Sulfur recovery plants 75–95 $4,000

Sulfur recovery and/or tail 

gas treatment 

Sulfuric Acid Plants 95–98 $1,000–$4,000

Cesium promoted catalyst Sulfuric Acid Plants with DoubleAbsorption process50% $1,000

a Sources: CoST control measures documentation report, May 2008, NESCAUM Report on Applicability of NOx, 

SO2, and PM Control Measures to Industrial Boilers, November 2008 available at 

http://www.nescaum.org/documents/ici-boilers-20081118-final.pdf, and Comprehensive Industry 

Document on Sulphuric Acid Plant, Govt. of India Central Pollution Control Board, May 2007. The estimates for 

these control measures reflect applications of control where there is no SO2 control measure currently operating 

except for the Cesium promoted catalyst.

4.A.1.2.2 SO2 Control Technology for Area Sources

Fuel switching from high to low-sulfur fuels is the predominant control measure 

available for SO2 area sources. For home heating oil users, our analyses included switching from 

a high-sulfur oil (approximately 2,500 parts per million (ppm) sulfur content) to a low-sulfur oil 

(approximately 500 ppm sulfur). A similar control measure is available for oil-fired industrial 

boilers. For more information on these measures, please refer to the CoST control measures 

documentation report.3

4.A.1.3 NOx Emissions Control Measures

4.A.1.3.1NOx Control Measures for Non-EGU Point Sources

This section describes available measures for controlling emissions of NOx from non-EGU 

point sources. In general, low-NOx burners (LNB) are often applied as a control technology for 

industrial boilers and for some other non-EGU sources because of their wide applicability and 

cost-effectiveness. While all controls presented in this analysis are considered generally 

technically feasible for each class of sources, source-specific cases may exist where a control 

technology is in fact not technically feasible.
4.A-6

Several types of NOx control technologies exist for non-EGU sources: selective catalytic 

reduction (SCR), selective noncatalytic reduction (SNCR), natural gas reburn (NGR), coal reburn, 

and low-NOx burners. The two control measures chosen most often were LNB and SCR because 

of their breadth of application. In some cases, LNB accompanied by flue gas recirculation (FGR) 

is applicable, such as when fuel-borne NOx emissions are expected to be of greater importance 

than thermal NOx emissions. When circumstances suggest that combustion controls are not 

feasible as a control technology (e.g., sintering processes, coke oven batteries, sulfur recovery 

plants), SNCR or SCR may be an appropriate choice. Finally, SCR can be applied along with a 

combustion control such as LNB with overfire air (OFA) to further reduce NOx emissions. All of 

these control measures are available for application on industrial boilers.

Besides industrial boilers, other non-EGU source categories covered in this RIA include 

petroleum refineries, kraft pulp mills, cement kilns, stationary internal combustion engines, 

glass manufacturing, combustion turbines, and incinerators. NOx control measures available for 

petroleum refineries, particularly process heaters at these plants, include LNB, SNCR, FGR, and 

SCR along with combinations of these technologies. NOx control measures available for kraft 

pulp mills include those available to industrial boilers, namely LNB, SCR, SNCR, along with water 

injection (WI). NOx control measures available for cement kilns include those available to 

industrial boilers, namely LNB, SCR, and SNCR. In addition, mid-kiln firing (MKF), ammoniabased SNCR, and biosolids injection can be used on cement kilns where appropriate. Nonselective catalytic reduction (NSCR) can be used on stationary internal combustion engines. 

OXY-Firing, a technique to modify combustion at glass manufacturing plants, can be used to 

reduce NOx emissions at such plants. LNB, SCR, and SCR combined with steam injection (SI) are 

available measures for combustion turbines. Finally, SNCR is an available control technology at 

incinerators. Table 4.A-4 lists typical examples of the control measures available for these 

categories. For more information on these measures, please refer to the CoST control measures 

documentation report.3
4.A-7

Table 4.A-4. Example NOx Control Measures for NonEGU Source Categoriesa

Control Measures

Sectors to Which These Control Measures 

Apply

Control Efficiency 

(percent)

Average Annualized 

Cost/ton

LNB Industrial boilers—all fuel types, Petroleum 

refineries, Cement manufacturing, Pulp 

and Paper mills

25 to 50% $200 to $1,000

LNB + FGR Petroleum refineries 55 $4,000

SNCR (urea-based or 

not)

Industrial boilers—all fuel types, Petroleum 

refineries, Cement manufacturing, pulp 

and paper mills, incinerators 

45 to 75 $1,000 to $2,000

SCR Industrial boilers—all fuel types, Petroleum 

refineries, Cement manufacturing, pulp 

and paper mills, Combustion turbines

80 to 90 $2,000 to 7,000

OXY-Firing Glass manufacturing 85 $2,500 to 6,000

NSCR Stationary internal combustion engines 90 500

MKF Cement manufacturing—dry 25 −$460 to 720

Biosolids Injection Cement manufacturing—dry 23 $300

SCR + SI Industrial boilers—all fuel types 95 $2,700

a Source: CoST control measures documentation report (June 2010). Note: a negative sign indicates a cost savings

from application of a control measure. The estimates for these control measures reflect applications of control 

where there is no NOx control measure currently operating except for post-combustion controls such as SCR and 

SNCR. For these measures, the costs presume that a NOx combustion control (such as LNB) is already operating 

on the unit to which the SCR or SNCR is applied.

4.A.2 Projected Monitor Design Values

Table 4.A-5. Area County Definitions for SO2 and NOx Emissions Reductions for Control 

Strategy Analysis

FIPS Code State Name County Name Area Label

1007 Alabama Bibb AL

1009 Alabama Blount AL

1073 Alabama Jefferson AL

1115 Alabama St. Clair AL

1117 Alabama Shelby AL

1125 Alabama Tuscaloosa AL

1127 Alabama Walker AL

(continued)
4.A-8

Table 4.A-5. Area County Definitions for SO2 and NOx Emissions Reductions for Control 

Strategy Analysis (continued)

FIPS Code State Name County Name Area Label

42003 Pennsylvania Allegheny all

42005 Pennsylvania Armstrong all

42007 Pennsylvania Beaver all

42019 Pennsylvania Butler all

42125 Pennsylvania Washington all

42129 Pennsylvania Westmoreland all

4003 Arizona Cochise AZ

4019 Arizona Pima AZ

4023 Arizona Santa Cruz AZ

13021 Georgia Bibb bib

13079 Georgia Crawford bib

13153 Georgia Houston bib

13169 Georgia Jones bib

13207 Georgia Monroe bib

13225 Georgia Peach bib

13289 Georgia Twiggs bib

6007 California Butte but

6011 California Colusa but

6021 California Glenn but

6063 California Plumas but

6103 California Tehama but

6115 California Yuba but

17031 Illinois Cook coo

17043 Illinois Du Page coo

17097 Illinois Lake coo

17197 Illinois Will coo

16005 Idaho Bannock fra

16007 Idaho Bear Lake fra

(continued)
4.A-9

Table 4.A-5. Area County Definitions for SO2 and NOx Emissions Reductions for Control 

Strategy Analysis (continued)

FIPS Code State Name County Name Area Label

16029 Idaho Caribou fra

16041 Idaho Franklin fra

16071 Idaho Oneida fra

13045 Georgia Carroll ful

13057 Georgia Cherokee ful

13063 Georgia Clayton ful

13067 Georgia Cobb ful

13077 Georgia Coweta ful

13089 Georgia De Kalb ful

13097 Georgia Douglas ful

13113 Georgia Fayette ful

13121 Georgia Fulton ful

13135 Georgia Gwinnett ful

13117 Georgia Forsyth ful

6025 California Imperial imp

6073 California San Diego imp

42011 Pennsylvania Berks lan

42029 Pennsylvania Chester lan

42043 Pennsylvania Dauphin lan

42071 Pennsylvania Lancaster lan

42075 Pennsylvania Lebanon lan

42133 Pennsylvania York lan

16023 Idaho Butte lem

16033 Idaho Clark lem

16037 Idaho Custer lem

16049 Idaho Idaho lem

16059 Idaho Lemhi lem

16085 Idaho Valley lem

(continued)
4.A-10

Table 4.A-5. Area County Definitions for SO2 and NOx Emissions Reductions for Control 

Strategy Analysis (continued)

FIPS Code State Name County Name Area Label

17005 Illinois Bond mad

17027 Illinois Clinton mad

17083 Illinois Jersey mad

17117 Illinois Macoupin mad

17119 Illinois Madison mad

17135 Illinois Montgomery mad

17163 Illinois St Clair mad

26099 Michigan Macomb MI

26115 Michigan Monroe MI

26125 Michigan Oakland MI

26161 Michigan Washtenaw MI

26163 Michigan Wayne MI

30001 Montana Beaverhead MT

30023 Montana Deer Lodge MT

30029 Montana Flathead MT

30039 Montana Granite MT

30047 Montana Lake MT

30053 Montana Lincoln MT

30061 Montana Mineral MT

30063 Montana Missoula MT

30077 Montana Powell MT

30081 Montana Ravalli MT

30089 Montana Sanders MT

36005 New York Bronx NY

36047 New York Kings NY

36061 New York New York NY

36081 New York Queens NY

36085 New York Richmond NY

(continued)
4.A-11

Table 4.A-5. Area County Definitions for SO2 and NOx Emissions Reductions for Control 

Strategy Analysis (continued)

FIPS Code State Name County Name Area Label

39035 Ohio Cuyahoga OH

39055 Ohio Geauga OH

39085 Ohio Lake OH

39093 Ohio Lorain OH

39103 Ohio Medina OH

39133 Ohio Portage OH

39153 Ohio Summit OH

41003 Oregon Benton OR

41019 Oregon Douglas OR

41029 Oregon Jackson OR

41035 Oregon Klamath OR

41037 Oregon Lake OR

41039 Oregon Lane OR

41041 Oregon Lincoln OR

41043 Oregon Linn OR

41017 Oregon Deschutes OR

6003 California Alpine sac

6005 California Amador sac

6013 California Contrasta sac

6017 California El Dorado sac

6061 California Placer sac

6067 California Sacramento sac

6095 California Solano sac

6101 California Sutter sac

6113 California Yolo sac

6019 California Fresno san

6027 California Inyo san

6029 California Kern san

(continued)
4.A-12

Table 4.A-5. Area County Definitions for SO2 and NOx Emissions Reductions for Control 

Strategy Analysis (continued)

FIPS Code State Name County Name Area Label

6031 California Kings san

6039 California Madera san

6043 California Mariposa san

6047 California Merced san

6051 California Mono san

6053 California Monterey san

6069 California San Benito san

6077 California San Joaquin san

6079 California San Luis Obispo san

6085 California Santa Clara san

6099 California Stanislaus san

6107 California Tulare san

6109 California Tuolumne san

16009 Idaho Benewah sho

16017 Idaho Bonner sho

16035 Idaho Clearwater sho

16055 Idaho Kootenai sho

16057 Idaho Latah sho

16079 Idaho Shoshone sho

6037 California Los Angeles sou

6059 California Orange sou

6065 California Riverside sou

6071 California San Bernardino sou

6111 California Ventura sou

48039 Texas Brazoria TX

48071 Texas Chambers TX

48157 Texas Fort Bend TX

48167 Texas Galveston TX

(continued)
4.A-13

Table 4.A-5. Area County Definitions for SO2 and NOx Emissions Reductions for Control 

Strategy Analysis (continued)

FIPS Code State Name County Name Area Label

48201 Texas Harris TX

48291 Texas Liberty TX

48339 Texas Montgomery TX

48473 Texas Waller TX

49003 Utah Box Elder Utah 1

49005 Utah Cache Utah 1

49033 Utah Rich Utah 1

49057 Utah Weber Utah 1

49007 Utah Carbon Utah 2

49011 Utah Davis Utah 2

49013 Utah Duchesne Utah 2

49023 Utah Juab Utah 2

49029 Utah Morgan Utah 2

49035 Utah Salt Lake Utah 2

49039 Utah Sanpete Utah 2

49043 Utah Summit Utah 2

49045 Utah Tooele Utah 2

49049 Utah Utah Utah 2

49051 Utah Wasatch Utah 2

53033 Washington King WA

53035 Washington Kitsap WA

53037 Washington Kittitas WA

53041 Washington Lewis WA

53045 Washington Mason WA

53053 Washington Pierce WA

53067 Washington Thurston WA

53077 Washington Yakima WA
4.A-14

Table 4.A-6. Air Quality Ratios for Monitors in Counties with at Least One Monitor with an Annual Design Value (DV) Above 15 or 

24-hr Design Value (DV) Above 35 in 2020 Base Case

FIPS 

Code High Monitor ID State Name County Name

2005 Annual 

DV

2020 Annual 

DV 2005 24-hr DV 2020 24-hr DV

24-hr to Annual 

DV 

Responsiveness

42003 420030064 Pennsylvania Allegheny 20.31 12.91 64.2 41.0 3.03

30047 300470028 Montana Lake 9.00 7.71 43.6 38.3 3.78

30063 300630031 Montana Missoula 10.52 9.13 44.6 37.4 3.78

30081 300810007 Montana Ravalli 9.01 7.89 45.1 37.3 3.78

6019 60190008 California Fresno 16.99 12.71 60.2 41.0 3.45

6029 60290010 California Kern 18.94 14.34 64.5 45.9 3.45

6031 60310004 California Kings 17.28 13.24 58.0 42.4 3.45

6099 60990005 California Stanislaus 14.21 10.85 51.4 37.0 3.45

6107 61072002 California Tulare 18.51 14.10 56.6 40.1 3.45

6037 60371301 California Los Angeles 17.66 13.14 48.7 39.7 3.45

6065 60658001 California Riverside 20.95 16.30 59.1 46.5 3.45

6071 60719004 California San Bernardino 19.01 14.96 55.5 41.5 3.45

49005 490050004 Utah Cache 11.56 9.78 56.9 42.6 4.91

49035 490353007 Utah Salt Lake 12.02 9.72 45.3 36.1 4.91

(continued)
4.A-15

Table 4.A-6. Air Quality Ratios for Monitors in Counties with at Least One Monitor with an Annual Design Value (DV) Above 15 or 

24-hr Design Value (DV) Above 35 in 2020 Base Case (continued)

FIPS 

Code

High 

Monitor ID State Name County Name

NH4SO4 

Component of 

2005 Annual DV

NH4NO3 

Component of 

2005 Annual DV

Direct PM2.5 

Component of 

2005 Annual DV

NH4SO4 

Component of 

2020 Annual DV

NH4NO3 

Component of 

2020 Annual DV

42003 420030064 Pennsylvania Allegheny 9.1830 0.7303 10.4046 4.1977 0.7669

30047 300470028 Montana Lake 0.9752 0.0936 7.9383 0.9007 0.0730

30063 300630031 Montana Missoula 1.2692 1.0152 8.2419 1.1767 0.7734

30081 300810007 Montana Ravalli 0.7614 0.2929 7.9577 0.7034 0.2380

6019 60190008 California Fresno 2.3402 4.1985 10.4583 1.9907 2.7196

6029 60290010 California Kern 3.1194 5.8850 9.9388 2.5838 3.7690

6031 60310004 California Kings 2.7393 4.7392 9.8017 2.2500 2.8483

6099 60990005 California Stanislaus 2.2879 3.8313 8.0978 1.8519 2.6903

6107 61072002 California Tulare 2.9375 5.3329 10.2433 2.4607 3.2405

6037 60371301 California Los Angeles 5.5145 3.5811 8.5679 3.7217 2.9601

6065 60658001 California Riverside 4.5070 5.2955 11.1521 3.3590 3.9822

6071 60719004 California San Bernardino 3.7956 3.8907 11.3297 2.8912 2.7994

49005 490050004 Utah Cache 1.4901 2.1042 7.9703 1.2447 1.5831

49035 490353007 Utah Salt Lake 1.7974 2.8766 7.3465 1.5642 2.2080

(continued)
4.A-16

Table 4.A-6. Air Quality Ratios for Monitors in Counties with at Least One Monitor with an Annual Design Value (DV) above 15 or 

24-hr Design Value (DV) Above 35 in 2020 Base Case (continued)

FIPS 

Code

High 

Monitor ID State Name County Name

Direct PM2.5

Component 

of 2020 

Annual DV

Area 

Label

Change in Area SO2 

Emissions Between 

2005 and 2020

Change in Area NOx

Emissions Between 

2005 and 2020

Change in County 

PM2.5 Emissions 

Between 2005 and 

2020

42003 420030064 Pennsylvania Allegheny 7.9528 all 259568 69304 804

30047 300470028 Montana Lake 6.7370 MT 853 9949 128

30063 300630031 Montana Missoula 7.1876 MT 853 9949 206

30081 300810007 Montana Ravalli 6.9574 MT 853 9949 144

6019 60190008 California Fresno 8.0008 san 5855 106130 1151

6029 60290010 California Kern 7.9904 san 5855 106130 1241

6031 60310004 California Kings 8.1443 san 5855 106130 132

6099 60990005 California Stanislaus 6.3118 san 5855 106130 571

6107 61072002 California Tulare 8.4003 san 5855 106130 592

6037 60371301 California Los Angeles 6.4628 sou 20834 230102 5223

6065 60658001 California Riverside 8.9602 sou 20834 230102 1421

6071 60719004 California San Bernardino 9.2726 sou 20834 230102 2026

49005 490050004 Utah Cache 6.9584 Utah 1 639 8192 124

49035 490353007 Utah Salt Lake 5.9562 Utah 2 8442 33871 799

(continued)
4.A-17

Table 4.A-6. Air Quality Ratios for Monitors in Counties with at Least One Monitor with an Annual Design Value (DV) above 15 or 

24-hr Design Value (DV) Above 35 in 2020 Base Case (continued)

FIPS 

Code

High 

Monitor ID State Name County Name

SO2 Air Quality 

Ratio (μg/m3

change in SO4

per 1,000 Tons 

SO2)

NOx Air Quality

Ratio (μg/m3

Change in NO3

per 1,000 Tons 

NOx)

PM2.5 Air Quality 

Ratio (μg/m3

Change in Direct 

PM2.5 per 1,000 

Tons PM)

24-hr DV 

Reduction 

Needed for 35

Annual DV 

Reduction 

Associated With 

the 24-hr DV 

Meeting 35

42003 420030064 Pennsylvania Allegheny 0.008 0.000 1.238 5.543 1.829

30047 300470028 Montana Lake 0.081 0.001 1.929 2.878 0.761

30063 300630031 Montana Missoula 0.106 0.015 1.929 1.990 0.526

30081 300810007 Montana Ravalli 0.063 0.005 1.929 1.815 0.480

6019 60190008 California Fresno 0.062 0.008 1.879 5.548 1.608

6029 60290010 California Kern 0.080 0.011 1.879 10.442 3.027

6031 60310004 California Kings 0.070 0.009 1.879 6.939 2.011

6099 60990005 California Stanislaus 0.057 0.008 1.136 1.578 0.457

6107 61072002 California Tulare 0.076 0.010 1.879 4.634 1.343

6037 60371301 California Los Angeles 0.052 0.003 0.597 4.236 1.228

6065 60658001 California Riverside 0.047 0.004 0.597 11.081 3.212

6071 60719004 California San Bernardino 0.040 0.003 0.597 6.041 1.751

49005 490050004 Utah Cache 0.321 0.040 1.929 7.168 1.460

49035 490353007 Utah Salt Lake 0.028 0.013 1.929 1.240 0.253
4.A-18

Table 4.A-7. Air Quality Ratios for Monitors in Counties With at Least One Monitor With an Annual Design Value (DV) Above 13 in 

2020 Baseline (15/35)

FIPS 

Code

High 

Monitor ID

State 

Name County Name

2005 Annual 

DV

2020 

Annual DV

2005 24-hr 

DV

2020 24-

hr DV

2020 15/35 

Annual DV

NH4SO4 Component of 

2005 Annual DV

6065 60658001 California Riverside 20.95 16.30 59.1 46.5 13.08 4.5070

6071 60710025 California San Bernardino 19.67 15.23 51.9 41.2 13.12 4.2309

(continued)

Table 4.A-7. Air Quality Ratios for Monitors in Counties With at Least One Monitor With an Annual Design Value (DV) Above 13 in 

2020 Baseline (15/35) (continued)

FIPS 

Code

High 

Monitor 

ID

State

Name County Name

NH4NO3

Component 

of 2005 

Annual DV

Direct PM2.5

Component 

of 2005 

Annual DV

NH4SO4

Component 

of 2020 

Annual DV

NH4NO3

Component 

of 2020 

Annual DV

Direct PM2.5

Component 

of 2020 

Annual DV

Area 

Label

Change in Area 

SO2 Emissions 

Between 2005 

and 2020

6065 60658001 California Riverside 5.2955 11.1521 3.3590 3.9822 8.9602 sou 20834

6071 60710025 California San Bernardino 4.0013 11.4396 3.0564 3.0890 9.0859 sou 20834

(continued)

Table 4.A-7. Air Quality Ratios for Monitors in Counties With at Least One Monitor With an Annual Design Value (DV) Above 13 in 

2020 Baseline (15/35) (continued)

FIPS 

Code

High 

Monitor 

ID

State 

Name County Name

Change in 

Area NOx

Emissions 

Between 2005 

and 2020

Change in 

County PM2.5

Emissions 

Between 2005 

and 2020

SO2 Air Quality 

Ratio (μg/m3

Change in SO4

per 1,000 Tons 

SO2)

NOx Air Quality 

Ratio (μg/m3

Change in NO3

per 1,000 Tons 

NOx)

PM2.5 Air Quality 

Ratio (μg/m3

Change in Direct 

PM2.5 per 1,000 

Tons PM)

Annual DV 

Reduction 

Needed for 

12 (μg/m3

)

6065 60658001 California Riverside 230102 1421 0.047 0.004 0.597 0.039

6071 60710025 California San Bernardino 230102 2026 0.043 0.003 0.597 0.077
4.A-19

Table 4.A-8. Air Quality Ratios for Monitors in Counties with at Least One Monitor With an Annual Design Value (DV) Above 12 in 

2020 Baseline (15/35)

FIPS 

Code

High 

Monitor ID

State 

Name County Name

2005 

Annual DV

2020 

Annual DV

2005

24-hr DV

2020

24-hr DV

2020 15/35 

Annual DV

NH4SO4 Component of 

2005 Annual DV

30053 300530018 Montana Lincoln 14.93 12.60 42.7 35.3 12.53 1.1342

6065 60658001 California Riverside 20.95 16.30 59.1 46.5 13.08 4.5070

6071 60710025 California San Bernardino 19.67 15.23 51.9 41.2 13.12 4.2309

26163 261630033 Michigan Wayne 17.50 12.35 43.9 31.3 12.35 7.2067

1073 10730023 Alabama Jefferson 18.57 12.34 44.1 27.9 12.34 7.5801

4023 40230004 Arizona Santa Cruz 12.94 12.06 36.1 33.8 12.06 1.6891

(continued)

Table 4.A-8. Air Quality Ratios for Monitors in Counties with at Least One Monitor With an Annual Design Value (DV) Above 12 in 

2020 Baseline (15/35) (continued)

FIPS 

Code

High 

Monitor ID

State 

Name County Name

NH4NO3

Component 

of 2005 

Annual DV

Direct PM2.5

Component 

of 2005 

Annual DV

NH4SO4

Component 

of 2020 

Annual DV

NH4NO3

Component 

of 2020 

Annual DV

Direct PM2.5

Component 

of 2020 

Annual DV

Area 

Label

Change in 

Area SO2

Emissions 

Between 

2005 and 

2020

30053 300530018 Montana Lincoln 0.4047 13.3936 1.0433 0.3556 11.2031 MT 853

6065 60658001 California Riverside 5.2955 11.1521 3.3590 3.9822 8.9602 sou 20,834

6071 60710025 California San Bernardino 4.0013 11.4396 3.0564 3.0890 9.0859 sou 20,834

26163 261630033 Michigan Wayne 2.2041 8.0960 4.2754 1.8639 6.2139 MI 142,340

1073 10730023 Alabama Jefferson 0.2657 10.7334 3.5837 0.2508 8.5105 AL 243,497

4023 40230004 Arizona Santa Cruz 0.0149 11.2381 1.5034 0.0121 10.5517 AZ 5,178

(continued)
4.A-20

Table 4.A-8. Air Quality Ratios for Monitors in Counties with at Least One Monitor With an Annual Design Value (DV) Above 12 in 

2020 Baseline (15/35) (continued)

FIPS 

Code

High Monitor 

ID State Name County Name

Change in 

Area NOx 

Emissions 

Between 

2005 and 

2020

Change in 

County 

PM2.5

Emissions 

Between 

2005 and 

2020

SO2 Air 

Quality 

Ratio (μg/m3

Change in 

SO4 per 

1,000 Tons 

SO2)

NOx Air 

Quality 

Ratio (μg/m3

Change in 

NO3 per 

1,000 Tons 

NOx)

PM2.5 Air 

Quality 

Ratio (μg/m3

Change in 

Direct PM2.5

per 1,000 

Tons PM)

Annual DV 

Reduction 

Needed for 

12 (μg/m3

)

30053 300530018 Montana Lincoln 9,949 107 0.094 0.007 1.929 0.494

6065 60658001 California Riverside 230,102 1,421 0.047 0.004 0.597 1.039

6071 60710025 California San Bernardino 230,102 2,026 0.043 0.003 0.597 0.857

26163 261630033 Michigan Wayne 142,522 2,846 0.013 0.002 1.238 0.301

1073 10730023 Alabama Jefferson 61,210 2,902 0.007 0.000 1.238 0.291

4023 40230004 Arizona Santa Cruz 25,105 48 0.038 0.000 1.929 0.011
4.A-21

Table 4.A-9. Air Quality Ratios for Monitors in Counties With at Least One Monitor With an Annual Design Value (DV) Above 11 in 

2020 Baseline (15/35)

FIPS 

Code

High 

Monitor ID

State 

Name County Name

Area 

Label

Change in Area SO2

Emissions Between 2005 

and 2020

Change in Area NOx

Emissions Between 2005 

and 2020

Change in County PM2.5

Emissions Between 2005 

and 2020

1073 10730023 Alabama Jefferson AL 243,497 61,210 2,902

4023 40230004 Arizona Santa Cruz AZ 5,178 25,105 48

13021 130210007 Georgia Bibb bib 57,968 23,656 276

17031 170310052 Illinois Cook coo 100,781 153,366 5,267

13121 131210039 Georgia Fulton ful 91,890 96,664 1,360

6025 60250005 California Imperial imp 5,629 51,787 295

17119 171191007 Illinois Madison mad 40,890 26,245 700

26163 261630033 Michigan Wayne MI 142,340 142,522 2,846

30053 300530018 Montana Lincoln MT 853 9,949 107

36061 360610056 New York New York NY 32,091 47,190 537

39035 390350038 Ohio Cuyahoga OH 115,275 61,836 984

6031 60310004 California Kings san 5,855 106,130 132

6107 61072002 California Tulare san 5,855 106,130 592

6071 60710025 California San Bernardino sou 20,834 230,102 2,026

6059 60590007 California Orange sou 20,834 230,102 940

6065 60658001 California Riverside sou 20,834 230,102 1,421

48201 482011035 Texas Harris TX 81,104 121,308 4,910

(continued)
4.A-22

Table 4.A-9. Air Quality Ratios for Monitors in Counties With at Least One Monitor With an Annual Design Value (DV) Above 11 in 

2020 Baseline (15/35) (continued)

FIPS 

Code

High 

Monitor ID

State 

Name County Name

SO2Air Quality Ratio 

(μg/m3 Change in SO4

per 1,000 Tons SO2)

NOx Air Quality Ratio 

(μg/m3 Change in NO3

per 1,000 Tons NOx)

PM2.5 Air Quality 

Ratio (μg/m3 Change 

in Direct PM2.5 per 

1,000 Tons PM)

Annual DV Reduction 

Needed for 11 

(μg/m3

)

1073 10730023 Alabama Jefferson 0.0072 0.0003 1.238 1.291

4023 40230004 Arizona Santa Cruz 0.0376 0.0001 1.929 1.011

13021 130210007 Georgia Bibb 0.0306 0.0000 1.238 0.171

17031 170310052 Illinois Cook 0.0119 0.0000 1.238 0.091

13121 131210039 Georgia Fulton 0.0180 0.0003 1.238 0.061

6025 60250005 California Imperial 0.1164 0.0023 0.597 0.171

17119 171191007 Illinois Madison 0.0404 0.0090 1.238 0.491

26163 261630033 Michigan Wayne 0.0128 0.0019 1.238 1.301

30053 300530018 Montana Lincoln 0.0939 0.0071 1.929 1.487

36061 360610056 New York New York 0.0529 0.0022 1.238 0.121

39035 390350038 Ohio Cuyahoga 0.0164 0.0048 1.238 0.741

6031 60310004 California Kings 0.0698 0.0085 1.879 0.180

6107 61072002 California Tulare 0.0763 0.0097 1.879 0.645

6071 60710025 California San Bernardino 0.0428 0.0031 0.597 2.077

6059 60590007 California Orange 0.0435 0.0027 0.597 0.008

6065 60658001 California Riverside 0.0470 0.0040 0.597 2.039

48201 482011035 Texas Harris 0.0164 0.0001 1.238 0.561
4.A-23

Table 4.A-10. Air Quality Ratios for Monitors in Counties with at Least One Monitor with an Annual Design Value (DV) Above 11 

or 24-hr Design Value (DV) Above 30 in 2020 Baseline (15/35)

FIPS 

Code

High 

Monitor ID State Name County Name

2005 

Annual DV

2020 

Annual DV Area Label

Change in Area 

SO2 Emissions 

Between 2005 

and 2020

Change in Area 

NOx Emissions 

Between 2005 

and 2020

Change in 

County PM2.5

Emissions 

Between 2005 

and 2020

1073 10730023 Alabama Jefferson 18.57 12.34 AL 243,497 61,210 2,902

42003 420030064 Pennsylvania Allegheny 20.31 12.91 all 259,568 69,304 804

4023 40230004 Arizona Santa Cruz 12.94 12.06 AZ 5,178 25,105 48

13021 130210007 Georgia Bibb 16.54 11.22 bib 57,968 23,656 276

6007 60070002 California Butte 12.73 9.56 but 2,320 8,494 693

17031 170310052 Illinois Cook 15.75 11.14 coo 100,781 153,366 5,267

16041 160410001 Idaho Franklin 7.7 6.68 fra 228 3,350 40

13121 131210039 Georgia Fulton 17.43 11.11 ful 91,890 96,664 1,360

6025 60250005 California Imperial 12.71 11.22 imp 5,629 51,787 295

42071 420710007 Pennsylvania Lancaster 16.55 10.73 lan 119,209 42,136 8,866

16059 160590004 Idaho Lemhi N/A N/A lem 169 577 44

17119 171191007 Illinois Madison 16.72 11.54 mad 40,890 26,245 700

26163 261630033 Michigan Wayne 17.5 12.35 MI 142,340 142,522 2,846

30047 300470028 Montana Lake 9 7.71 MT 853 9,949 128

30081 300810007 Montana Ravalli 9.01 7.89 MT 853 9,949 144

30063 300630031 Montana Missoula 10.52 9.13 MT 853 9,949 206

30053 300530018 Montana Lincoln 14.93 12.6 MT 853 9,949 107

36061 360610056 New York New York 16.18 11.17 NY 32,091 47,190 537

(continued)
4.A-24

Table 4.A-10. Air Quality Ratios for Monitors in Counties with at Least One Monitor with an Annual Design Value (DV) Above 11 

or 24-hr Design Value (DV) Above 30 in 2020 Baseline (15/35) (continued)

FIPS 

Code

High 

Monitor ID State Name County Name

2005 

Annual DV

2020 

Annual DV Area Label

Change in Area 

SO2 Emissions 

Between 2005 

and 2020

Change in Area 

NOx Emissions 

Between 2005 

and 2020

Change in 

County PM2.5

Emissions 

Between 2005 

and 2020

39035 390350038 Ohio Cuyahoga 17.37 11.79 OH 115,275 61,836 984

41035 410350004 Oregon Klamath 11.2 8.54 OR 1,489 22,686 769

41039 410392013 Oregon Lane 11.93 9.43 OR 1,489 22,686 1,666

6067 60670006 California Sacramento 11.88 8.76 sac 9,448 42,974 1,311

6099 60990005 California Stanislaus 14.21 10.85 san 5,855 106,130 571

6019 60190008 California Fresno 16.99 12.71 san 5,855 106,130 1,151

6031 60310004 California Kings 17.28 13.24 san 5,855 106,130 132

6107 61072002 California Tulare 18.51 14.1 san 5,855 106,130 592

16079 160790017 Idaho Shoshone 12.08 10.66 sho 555 5,546 43

6059 60590007 California Orange 15.75 11.93 sou 20,834 230,102 940

6065 60658001 California Riverside 20.95 16.3 sou 20,834 230,102 1,421

6071 60710025 California San Bernardino 19.67 15.23 sou 20,834 230,102 2,026

48201 482011035 Texas Harris 15.42 11.61 TX 81,104 121,308 4,910

49005 490050004 Utah Cache 11.56 9.78 Utah 1 639 8,192 124

49035 490350012 Utah Salt Lake N/A N/A Utah 2 8,442 33,,871 799

49011 490110004 Utah Davis 10.31 8.58 Utah 2 8,442 33,871 243

49049 490494001 Utah Utah 10.52 8.8 Utah 2 8,442 33,871 383

53053 530530029 Washington Pierce 10.55 8.11 WA 11,269 91,530 1,058

(continued)
4.A-25

Table 4.A-10. Air Quality Ratios for Monitors in Counties with at Least One Monitor with an Annual Design Value (DV) Above 11 

or 24-hr Design Value (DV) Above 30 in 2020 Baseline (15/35) (continued)

FIPS 

Code

High 

Monitor ID State Name County Name

SO2 Air 

Quality Ratio 

(μg/m3

Change in SO4 

per 1,000 

Tons SO2)

NOx Air 

Quality Ratio 

(μg/m3

Change in 

NO3 per 

1,000 Tons 

NOx)

PM2.5 Air 

Quality Ratio 

(ug/m3

Change in 

Direct PM2.5

per 1,000 

Tons of PM2.5)

Annual DV 

Reduction 

Needed for 

11 (ug/m3

)

24-hr DV 

Reduction 

Needed for 

30 (ug/m3

)

Annual DV 

Reduction 

Corresponding 

to the 24-hr DV 

Meeting 30 

(ug/m3

)

1073 10730023 Alabama Jefferson 0.007 0.000 1.238 1.291 0.000 0.000

42003 420030064 Pennsylvania Allegheny 0.008 0.000 1.238 0.032 5.000 1.650

4023 40230004 Arizona Santa Cruz 0.038 0.000 1.929 1.011 3.332 1.262

13021 130210007 Georgia Bibb 0.031 0.000 1.238 0.171 0.000 0.000

6007 60070002 California Butte 0.079 0.018 1.879 0.000 1.674 0.369

17031 170310052 Illinois Cook 0.012 0.000 1.238 0.091 0.000 0.000

16041 160410001 Idaho Franklin 0.609 0.087 1.929 0.000 0.010 0.002

13121 131210039 Georgia Fulton 0.018 0.000 1.238 0.061 0.000 0.000

6025 60250005 California Imperial 0.116 0.002 0.597 0.171 1.331 0.386

42071 420710007 Pennsylvania Lancaster 0.015 0.007 1.238 0.000 0.029 0.010

16059 160590004 Idaho Lemhi 0.371 0.131 1.929 0.000 0.837 0.192

17119 171191007 Illinois Madison 0.040 0.009 1.238 0.491 0.000 0.000

26163 261630033 Michigan Wayne 0.013 0.002 1.238 1.301 0.888 0.299

30047 300470028 Montana Lake 0.081 0.001 1.929 0.000 5.000 1.323

30081 300810007 Montana Ravalli 0.063 0.005 1.929 0.000 5.000 1.323

30063 300630031 Montana Missoula 0.106 0.015 1.929 0.000 3.993 1.056

30053 300530018 Montana Lincoln 0.094 0.007 1.929 1.487 4.637 1.227

36061 360610056 New York New York 0.053 0.002 1.238 0.121 0.000 0.000

(continued)
4.A-26

Table 4.A-10. Air Quality Ratios for Monitors in Counties with at Least One Monitor with an Annual Design Value (DV) Above 11 

or 24-hr Design Value (DV) Above 30 in 2020 Baseline (15/35) (continued)

FIPS 

Code

High 

Monitor ID State Name County Name

SO2 Air 

Quality Ratio 

(μg/m3

Change in SO4 

per 1,000 

Tons SO2)

NOx Air 

Quality Ratio 

(μg/m3

Change in 

NO3 per 1,000 

Tons NOx)

PM2.5 Air 

Quality Ratio 

(ug/m3

Change in 

Direct PM2.5

per 1,000 

Tons of PM2.5)

Annual DV 

Reduction 

Needed for 

11 (ug/m3

)

24-hr DV 

Reduction 

Needed for 

30 (ug/m3

)

Annual DV 

Reduction 

Corresponding 

to the 24-hr DV 

Meeting 30 

(ug/m3

)

39035 390350038 Ohio Cuyahoga 0.016 0.005 1.238 0.741 0.000 0.000

41035 410350004 Oregon Klamath 0.059 0.002 1.929 0.000 0.363 0.082

41039 410392013 Oregon Lane 0.068 0.003 1.929 0.000 3.520 0.793

6067 60670006 California Sacramento 0.033 0.007 1.879 0.000 2.438 0.707

6099 60990005 California Stanislaus 0.057 0.008 1.879 0.000 1.300 0.377

6019 60190008 California Fresno 0.062 0.008 1.879 0.000 0.402 0.117

6031 60310004 California Kings 0.070 0.009 1.879 0.180 5.000 1.449

6107 61072002 California Tulare 0.076 0.010 1.879 0.645 1.333 0.386

16079 160790017 Idaho Shoshone 0.129 0.014 1.929 0.000 1.475 0.337

6059 60590007 California Orange 0.043 0.003 0.597 0.008 0.525 0.152

6065 60658001 California Riverside 0.047 0.004 0.597 2.039 5.000 1.449

6071 60710025 California San Bernardino 0.043 0.003 0.597 2.077 3.537 1.025

48201 482011035 Texas Harris 0.016 0.000 1.238 0.561 0.000 0.000

49005 490050004 Utah Cache 0.321 0.040 1.929 0.000 5.000 1.018

49035 490350012 Utah Salt Lake 0.026 0.012 1.929 0.000 4.821 0.982

49011 490110004 Utah Davis 0.028 0.014 1.929 0.000 0.864 0.176

49049 490494001 Utah Utah 0.024 0.015 1.929 0.000 3.461 0.705

53053 530530029 Washington Pierce 0.029 0.000 1.929 0.000 0.515 0.146
4.A-27

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Alabama Baldwin 11.44 7.45 7.45 7.45 7.45 7.45 7.45

Alabama Clay 13.27 8.42 8.42 8.42 8.42 8.42 8.42

Alabama Colbert 12.75 8.21 8.21 8.21 8.21 8.21 8.21

Alabama DeKalb 14.13 8.74 8.74 8.74 8.74 8.74 8.74

Alabama Escambia 13.19 9.29 9.29 9.29 9.29 9.29 9.29

Alabama Etowah 14.87 9.38 9.38 9.38 9.38 9.38 9.38

Alabama Houston 13.22 9.32 9.32 9.32 9.32 9.32 9.32

Alabama Jefferson 18.57 12.34 12.34 12.34 12.03 11.00 11.00

Alabama Jefferson 15.46 10.33 10.33 10.33 10.02 8.99 8.99

Alabama Jefferson 13.52 8.77 8.77 8.77 8.46 7.43 7.43

Alabama Jefferson 15.89 10.03 10.03 10.03 9.729 8.69 8.69

Alabama Jefferson 17.15 11.72 11.72 11.72 11.41 10.38 10.38

Alabama Jefferson 15.1 9.98 9.98 9.98 9.67 8.64 8.64

Alabama Jefferson 14.42 9.02 9.02 9.02 8.71 7.68 7.68

Alabama Jefferson 14.53 9.3 9.3 9.3 8.99 7.96 7.96

Alabama Madison 13.83 8.54 8.54 8.54 8.54 8.54 8.54

Alabama Mobile 12.9 8.8 8.8 8.8 8.8 8.8 8.8

Alabama Mobile 12.36 8.33 8.33 8.33 8.33 8.33 8.33

Alabama Mobile 11.51 7.51 7.51 7.51 7.51 7.51 7.51

Alabama Montgomery 14.24 9.77 9.77 9.77 9.77 9.77 9.77

(continued)
4.A-28

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Alabama Morgan 13.32 8.42 8.42 8.42 8.42 8.42 8.42

Alabama Russell 15.73 10.63 10.63 10.63 10.63 10.63 10.63

Alabama Shelby 14.43 9.3 9.3 9.3 9.3 9.3 9.3

Alabama Sumter 11.92 7.75 7.75 7.75 7.75 7.75 7.75

Alabama Talladega 14.51 9.08 9.08 9.08 9.08 9.08 9.08

Alabama Tuscaloosa 13.56 8.78 8.78 8.78 8.78 8.78 8.78

Alabama Walker 13.86 8.89 8.89 8.89 8.89 8.89 8.89

Arizona Cochise 7 6.56 6.56 6.56 6.56 6.54 6.54

Arizona Coconino 6.49 6.02 6.02 6.02 6.02 6.02 6.02

Arizona Gila 8.94 8.11 8.11 8.11 8.11 8.11 8.11

Arizona Maricopa 12.17 9.64 9.64 9.64 9.64 9.64 9.64

Arizona Maricopa 12.59 10.24 10.24 10.24 10.24 10.24 10.24

Arizona Maricopa 9.97 8.02 8.02 8.02 8.02 8.02 8.02

Arizona Pima 6.04 5.12 5.12 5.12 5.12 5.09 5.10

Arizona Pima 5.85 4.95 4.95 4.95 4.95 4.92 4.93

Arizona Pinal 7.77 6.92 6.92 6.92 6.92 6.92 6.92

Arizona Pinal 5.71 5.04 5.04 5.04 5.04 5.04 5.04

Arizona Santa Cruz 12.94 12.06 12.06 12.06 12.02 11.04 10.79

Arkansas Arkansas 12.45 8.76 8.76 8.76 8.76 8.76 8.76

Arkansas Ashley 12.83 9.44 9.44 9.44 9.44 9.44 9.44

(continued)
4.A-29

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Arkansas Crittenden 13.36 8.63 8.63 8.63 8.63 8.63 8.63

Arkansas Faulkner 12.79 9.16 9.16 9.16 9.16 9.16 9.16

Arkansas Garland 12.4 8.79 8.79 8.79 8.79 8.79 8.79

Arkansas Mississippi 12.61 8.32 8.32 8.32 8.32 8.32 8.32

Arkansas Phillips 12.1 8.15 8.15 8.15 8.15 8.15 8.15

Arkansas Polk 11.65 8.35 8.35 8.35 8.35 8.35 8.35

Arkansas Pope 12.79 9.4 9.4 9.4 9.4 9.4 9.4

Arkansas Pulaski 13.17 9.11 9.11 9.11 9.11 9.11 9.11

Arkansas Pulaski 14.05 9.91 9.91 9.91 9.91 9.91 9.91

Arkansas Pulaski 13.59 9.52 9.52 9.52 9.52 9.52 9.52

Arkansas Union 12.86 9.3 9.3 9.3 9.3 9.3 9.3

Arkansas White 12.57 9.13 9.13 9.13 9.13 9.13 9.13

California Alameda 9.44 7.42 7.42 7.42 7.42 7.42 7.42

California Alameda 9.34 7.18 7.18 7.18 7.18 7.18 7.18

California Butte 12.73 9.56 9.56 9.56 9.56 9.56 9.18

California Calaveras 7.77 6.05 6.05 6.05 6.05 6.05 6.05

California Colusa 7.39 6.25 6.25 6.25 6.25 6.25 6.25

California Contra Costa 9.47 7.3 7.3 7.3 7.3 7.3 7.3

California Fresno 16.99 12.71 9.76 9.76 9.76 9.76 8.00

California Fresno 16.38 12.33 9.42 9.42 9.42 9.42 7.67

(continued)
4.A-30

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

California Fresno 17.17 12.87 9.96 9.96 9.96 9.96 8.21

California Imperial 12.71 11.22 11.22 11.22 11.22 10.80 10.80

California Imperial 8.39 7.35 7.35 7.35 7.35 6.93 6.93

California Imperial 9.2 8.12 8.12 8.12 8.12 7.70 7.70

California Inyo 5.25 4.8 4.12 4.12 4.12 4.12 3.87

California Kern 18.94 14.34 7.98 7.98 7.98 7.98 7.29

California Kern 18.68 14.18 7.84 7.84 7.84 7.84 7.16

California Kern 19.17 14.72 8.36 8.36 8.36 8.36 7.68

California Kings 17.28 13.24 11.22 11.22 11.22 11.04 9.33

California Lake 4.62 3.79 3.79 3.79 3.79 3.79 3.79

California Los Angeles 17.03 12.88 9.87 9.87 9.82 9.60 9.60

California Los Angeles 18.19 13.44 10.34 10.34 10.29 10.04 10.04

California Los Angeles 18 13.19 10.03 10.03 9.984 9.72 9.72

California Los Angeles 15.35 11.41 8.57 8.57 8.53 8.34 8.34

California Los Angeles 17.66 13.14 10.07 10.07 10.02 9.79 9.79

California Los Angeles 17.92 13.16 10.07 10.07 10.02 9.78 9.78

California Los Angeles 15.36 11.31 8.28 8.28 8.23 8.00 8.00

California Los Angeles 16.62 12.3 9.35 9.35 9.30 9.09 9.09

California Los Angeles 15.21 11.24 8.34 8.34 8.29 8.09 8.09

California Los Angeles 8.42 7.06 4.58 4.58 4.55 4.45 4.45

(continued)
4.A-31

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

California Mendocino 6.46 5.14 5.14 5.14 5.14 5.14 5.14

California Merced 14.78 11.24 10.39 10.39 10.39 10.39 10.10

California Monterey 6.96 5.39 4.75 4.75 4.75 4.75 4.52

California Nevada 5.16 3.83 3.83 3.83 3.83 3.83 3.83

California Nevada 6.71 5.31 5.31 5.31 5.31 5.31 5.31

California Orange 15.75 11.93 11.05 11.05 11.01 10.75 10.27

California Orange 11.33 9.43 8.77 8.77 8.74 8.53 8.05

California Placer 9.8 7.24 7.24 7.24 7.24 7.24 7.24

California Plumas 9.75 7.8 7.8 7.8 7.8 7.8 7.8

California Plumas 11.46 8.91 8.91 8.91 8.91 8.91 8.91

California Riverside 18.91 14.84 11.65 11.61 10.61 9.62 9.62

California Riverside 10.31 8.66 5.90 5.86 4.88 3.97 3.97

California Riverside 20.95 16.3 13.08 13.04 12.04 11.04 11.04

California Sacramento 11.88 8.76 8.76 8.76 8.76 8.76 7.07

California Sacramento 11.44 8.75 8.75 8.75 8.75 8.75 7.06

California Sacramento 10.53 8.01 8.01 8.01 8.01 8.01 6.32

California San Bernardino 19.67 15.23 13.12 13.04 12.04 11.04 11.04

California San Bernardino 10.29 8.2 6.39 6.32 5.33 4.39 4.39

California San Bernardino 19.14 14.86 12.67 12.60 11.59 10.58 10.58

California San Bernardino 10.77 9.16 7.50 7.42 6.44 5.54 5.54

(continued)
4.A-32

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

California San Bernardino 19.01 14.96 12.90 12.82 11.83 10.84 10.84

California San Diego 11.92 8.68 8.68 8.68 8.68 8.68 8.68

California San Diego 12.27 9.09 9.09 9.09 9.09 9.09 9.09

California San Diego 10.59 7.64 7.64 7.64 7.64 7.64 7.64

California San Diego 12.79 9.56 9.56 9.56 9.56 9.56 9.56

California San Diego 13.46 9.83 9.83 9.83 9.83 9.83 9.83

California San Francisco 9.62 7.05 7.05 7.05 7.05 7.05 7.05

California San Joaquin 12.94 9.96 9.07 9.07 9.07 9.07 8.78

California San Luis Obispo 6.92 5.43 4.76 4.76 4.76 4.76 4.52

California San Luis Obispo 7.94 6.24 5.47 5.47 5.47 5.47 5.21

California San Mateo 9.03 6.76 6.76 6.76 6.76 6.76 6.76

California Santa Barbara 10.37 8.04 8.04 8.04 8.04 8.04 8.04

California Santa Clara 11.38 8.66 7.75 7.75 7.75 7.75 7.42

California Santa Clara 10.32 8.03 7.13 7.13 7.13 7.13 6.81

California Shasta 7.41 5.48 5.48 5.48 5.48 5.48 5.48

California Solano 9.99 7.7 7.7 7.7 7.7 7.7 7.7

California Sonoma 8.21 6.15 6.15 6.15 6.15 6.15 6.15

California Stanislaus 14.21 10.85 9.32 9.32 9.32 9.32 8.43

California Sutter 9.85 7.53 7.53 7.53 7.53 7.53 7.53

California Tulare 18.51 14.1 11.69 11.69 11.69 11.04 10.54

(continued)
4.A-33

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

California Ventura 10.68 7.84 7.19 7.19 7.16 7.01 7.01

California Ventura 9.74 7.69 7.04 7.04 7.01 6.86 6.86

California Ventura 11.68 8.79 8.09 8.09 8.06 7.89 7.89

California Ventura 10.69 7.64 7.14 7.14 7.12 7.00 7.00

California Yolo 9.03 7.15 7.15 7.15 7.15 7.15 7.15

Colorado Adams 10.06 7.58 7.58 7.58 7.58 7.58 7.58

Colorado Arapahoe 7.96 6.02 6.02 6.02 6.02 6.02 6.02

Colorado Boulder 8.32 6.68 6.68 6.68 6.68 6.68 6.68

Colorado Boulder 6.96 5.6 5.6 5.6 5.6 5.6 5.6

Colorado Delta 7.44 5.74 5.74 5.74 5.74 5.74 5.74

Colorado Denver 9.37 7.07 7.07 7.07 7.07 7.07 7.07

Colorado Denver 9.76 7.37 7.37 7.37 7.37 7.37 7.37

Colorado Elbert 4.4 3.48 3.48 3.48 3.48 3.48 3.48

Colorado El Paso 6.73 4.85 4.85 4.85 4.85 4.85 4.85

Colorado El Paso 7.94 5.67 5.67 5.67 5.67 5.67 5.67

Colorado Larimer 7.33 5.95 5.95 5.95 5.95 5.95 5.95

Colorado Mesa 9.28 7.34 7.34 7.34 7.34 7.34 7.34

Colorado Pueblo 7.45 5.73 5.73 5.73 5.73 5.73 5.73

Colorado San Miguel 4.65 4.09 4.09 4.09 4.09 4.09 4.09

Colorado Weld 8.19 6.61 6.61 6.61 6.61 6.61 6.61

(continued)
4.A-34

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Colorado Weld 8.78 7.06 7.06 7.06 7.06 7.06 7.06

Connecticut Fairfield 13.21 8.79 8.79 8.79 8.79 8.79 8.79

Connecticut Fairfield 12.49 8.27 8.27 8.27 8.27 8.27 8.27

Connecticut Fairfield 12.43 8.15 8.15 8.15 8.15 8.15 8.15

Connecticut Fairfield 11.48 7.51 7.51 7.51 7.51 7.51 7.51

Connecticut Hartford 11.03 7.29 7.29 7.29 7.29 7.29 7.29

Connecticut Litchfield 8.01 5.03 5.03 5.03 5.03 5.03 5.03

Connecticut New Haven 12.12 7.93 7.93 7.93 7.93 7.93 7.93

Connecticut New Haven 12.45 8.1 8.1 8.1 8.1 8.1 8.1

Connecticut New Haven 13.12 8.62 8.62 8.62 8.62 8.62 8.62

Connecticut New Haven 11.17 7.24 7.24 7.24 7.24 7.24 7.24

Connecticut New Haven 12.74 8.33 8.33 8.33 8.33 8.33 8.33

Connecticut New London 10.96 7.25 7.25 7.25 7.25 7.25 7.25

Delaware Kent 12.61 7.66 7.66 7.66 7.66 7.66 7.66

Delaware Kent 12.52 7.71 7.71 7.71 7.71 7.71 7.71

Delaware New Castle 13.73 8.57 8.57 8.57 8.57 8.57 8.57

Delaware New Castle 12.92 7.93 7.93 7.93 7.93 7.93 7.93

Delaware New Castle 13.69 8.55 8.55 8.55 8.55 8.55 8.55

Delaware New Castle 14.87 9.42 9.42 9.42 9.42 9.42 9.42

Delaware Sussex 13.39 8.13 8.13 8.13 8.13 8.13 8.13

(continued)
4.A-35

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

District of Columbia District of Columbia 14.16 8.86 8.86 8.86 8.86 8.86 8.86

District of Columbia District of Columbia 14.41 8.71 8.71 8.71 8.71 8.71 8.71

District of Columbia District of Columbia 13.99 8.48 8.48 8.48 8.48 8.48 8.48

Florida Alachua 9.32 6.19 6.19 6.19 6.19 6.19 6.19

Florida Alachua 9.59 6.44 6.44 6.44 6.44 6.44 6.44

Florida Bay 11.46 7.96 7.96 7.96 7.96 7.96 7.96

Florida Brevard 8.32 5.56 5.56 5.56 5.56 5.56 5.56

Florida Broward 8.22 5.93 5.93 5.93 5.93 5.93 5.93

Florida Broward 8.18 5.78 5.78 5.78 5.78 5.78 5.78

Florida Broward 8.21 5.78 5.78 5.78 5.78 5.78 5.78

Florida Citrus 9 5.69 5.69 5.69 5.69 5.69 5.69

Florida Duval 9.9 6.88 6.88 6.88 6.88 6.88 6.88

Florida Duval 10.44 7.49 7.49 7.49 7.49 7.49 7.49

Florida Escambia 11.72 8.38 8.38 8.38 8.38 8.38 8.38

Florida Hillsborough 10.74 7.37 7.37 7.37 7.37 7.37 7.37

Florida Hillsborough 10.52 7.23 7.23 7.23 7.23 7.23 7.23

Florida Lee 8.36 5.88 5.88 5.88 5.88 5.88 5.88

Florida Leon 12.56 9 9 9 9 9 9

Florida Manatee 8.81 5.64 5.64 5.64 5.64 5.64 5.64

Florida Marion 10.11 6.93 6.93 6.93 6.93 6.93 6.93

(continued)
4.A-36

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Florida Miami-Dade 9.45 6.72 6.72 6.72 6.72 6.72 6.72

Florida Miami-Dade 8.14 6.42 6.42 6.42 6.42 6.42 6.42

Florida Orange 9.61 6.43 6.43 6.43 6.43 6.43 6.43

Florida Orange 9.5 6.28 6.28 6.28 6.28 6.28 6.28

Florida Palm Beach 7.84 5.83 5.83 5.83 5.83 5.83 5.83

Florida Palm Beach 7.7 5.69 5.69 5.69 5.69 5.69 5.69

Florida Pinellas 9.82 6.64 6.64 6.64 6.64 6.64 6.64

Florida Pinellas 9.52 6.41 6.41 6.41 6.41 6.41 6.41

Florida Polk 9.53 6.55 6.55 6.55 6.55 6.55 6.55

Florida St. Lucie 8.34 5.77 5.77 5.77 5.77 5.77 5.77

Florida Sarasota 8.77 5.77 5.77 5.77 5.77 5.77 5.77

Florida Seminole 9.51 6.33 6.33 6.33 6.33 6.33 6.33

Florida Volusia 9.27 6.08 6.08 6.08 6.08 6.08 6.08

Georgia Bibb 16.54 11.22 11.22 11.22 11.22 11.04 11.04

Georgia Bibb 13.94 9.1 9.1 9.1 9.1 8.92 8.92

Georgia Chatham 13.74 9.33 9.33 9.33 9.33 9.33 9.33

Georgia Chatham 13.93 9.56 9.56 9.56 9.56 9.56 9.56

Georgia Clarke 14.9 9.69 9.69 9.69 9.69 9.69 9.69

Georgia Clayton 16.5 10.65 10.65 10.65 10.65 10.65 10.65

Georgia Cobb 16.15 10.6 10.6 10.6 10.6 10.6 10.6

(continued)
4.A-37

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Georgia Cobb 15.42 9.88 9.88 9.88 9.88 9.88 9.88

Georgia DeKalb 15.48 9.54 9.54 9.54 9.54 9.54 9.54

Georgia DeKalb 15.37 9.55 9.55 9.55 9.55 9.55 9.55

Georgia Dougherty 14.46 10.24 10.24 10.24 10.24 10.24 10.24

Georgia Floyd 16.13 10.63 10.63 10.63 10.63 10.63 10.63

Georgia Fulton 15.84 9.82 9.82 9.82 9.82 9.82 9.82

Georgia Fulton 17.43 11.11 11.11 11.11 11.11 10.98 10.98

Georgia Glynn 12.25 8.74 8.74 8.74 8.74 8.74 8.74

Georgia Gwinnett 16.07 10.45 10.45 10.45 10.45 10.45 10.45

Georgia Hall 14.16 9.16 9.16 9.16 9.16 9.16 9.16

Georgia Houston 14.19 9.34 9.34 9.34 9.34 9.32 9.32

Georgia Lowndes 12.58 9.26 9.26 9.26 9.26 9.26 9.26

Georgia Muscogee 14.94 9.94 9.94 9.94 9.94 9.94 9.94

Georgia Muscogee 15.39 10.4 10.4 10.4 10.4 10.4 10.4

Georgia Muscogee 14.16 9.58 9.58 9.58 9.58 9.58 9.58

Georgia Paulding 14.12 8.76 8.76 8.76 8.76 8.76 8.76

Georgia Richmond 15.61 10.75 10.75 10.75 10.75 10.75 10.75

Georgia Richmond 15.68 10.84 10.84 10.84 10.84 10.84 10.84

Georgia Walker 15.49 9.86 9.86 9.86 9.86 9.86 9.86

Georgia Washington 15.14 10.42 10.42 10.42 10.42 10.42 10.42

(continued)
4.A-38

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Georgia Wilkinson 15.27 10.3 10.3 10.3 10.3 10.3 10.3

Idaho Ada 8.41 7.6 7.6 7.6 7.6 7.6 7.6

Idaho Bannock 7.66 6.97 6.97 6.97 6.97 6.97 6.97

Idaho Benewah 9.59 8.59 8.59 8.59 8.59 8.59 8.57

Idaho Canyon 8.46 7.46 7.46 7.46 7.46 7.46 7.46

Idaho Franklin 7.7 6.68 6.68 6.68 6.68 6.68 6.68

Idaho Idaho 9.58 8.8 8.8 8.8 8.8 8.8 8.75

Idaho Shoshone 12.08 10.66 10.66 10.66 10.66 10.66 10.32

Illinois Adams 12.5 8.91 8.91 8.91 8.91 8.91 8.91

Illinois Champaign 12.5 8.39 8.39 8.39 8.39 8.39 8.39

Illinois Champaign 12.53 8.4 8.4 8.4 8.4 8.4 8.4

Illinois Cook 15.21 11.11 11.11 11.11 11.11 10.97 10.97

Illinois Cook 14.81 10.69 10.69 10.69 10.69 10.55 10.55

Illinois Cook 15.75 11.14 11.14 11.14 11.14 11.00 11.00

Illinois Cook 15.03 10.54 10.54 10.54 10.54 10.40 10.40

Illinois Cook 14.89 10.5 10.5 10.5 10.5 10.36 10.36

Illinois Cook 14.77 10.77 10.77 10.77 10.77 10.63 10.63

Illinois Cook 15.24 10.78 10.78 10.78 10.78 10.64 10.64

Illinois Cook 12.78 8.9 8.9 8.9 8.9 8.76 8.76

Illinois Cook 12.76 8.87 8.87 8.87 8.87 8.73 8.73

(continued)
4.A-39

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Illinois Cook 15.48 10.86 10.86 10.86 10.86 10.72 10.72

Illinois DuPage 13.82 9.84 9.84 9.84 9.84 9.84 9.84

Illinois Jersey 12.89 8.78 8.78 8.78 8.78 8.51 8.51

Illinois Kane 13.32 9.51 9.51 9.51 9.51 9.51 9.51

Illinois Kane 14.34 10.25 10.25 10.25 10.25 10.25 10.25

Illinois Lake 11.81 8.34 8.34 8.34 8.34 8.34 8.34

Illinois McHenry 12.4 8.86 8.86 8.86 8.86 8.86 8.86

Illinois McLean 12.39 8.58 8.58 8.58 8.58 8.58 8.58

Illinois Macon 13.24 9.21 9.21 9.21 9.21 9.21 9.21

Illinois Madison 16.72 11.54 11.54 11.54 11.54 10.82 10.82

Illinois Madison 14.01 9.7 9.7 9.7 9.7 8.98 8.98

Illinois Madison 14.32 9.97 9.97 9.97 9.97 9.25 9.25

Illinois Peoria 13.34 9.41 9.41 9.41 9.41 9.41 9.41

Illinois Randolph 13.11 8.7 8.7 8.7 8.7 8.7 8.7

Illinois Rock Island 12.01 8.61 8.61 8.61 8.61 8.61 8.61

Illinois Saint Clair 15.58 10.63 10.63 10.63 10.63 10.34 10.34

Illinois Saint Clair 14.29 9.66 9.66 9.66 9.66 9.40 9.40

Illinois Sangamon 13.13 9.39 9.39 9.39 9.39 9.39 9.39

Illinois Will 13.63 9.69 9.69 9.69 9.69 9.69 9.69

Illinois Will 11.52 7.96 7.96 7.96 7.96 7.96 7.96

(continued)
4.A-40

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Illinois Winnebago 13.57 9.78 9.78 9.78 9.78 9.78 9.78

Indiana Allen 13.67 9.92 9.92 9.92 9.92 9.92 9.92

Indiana Allen 13.55 9.84 9.84 9.84 9.84 9.84 9.84

Indiana Clark 16.44 10.19 10.19 10.19 10.19 10.19 10.19

Indiana Delaware 13.69 9.11 9.11 9.11 9.11 9.11 9.11

Indiana Dubois 15.19 9.34 9.34 9.34 9.34 9.34 9.34

Indiana Floyd 14.85 9 9 9 9 9 9

Indiana Henry 13.64 9.05 9.05 9.05 9.05 9.05 9.05

Indiana Howard 13.93 9.61 9.61 9.61 9.61 9.61 9.61

Indiana Knox 14.03 8.78 8.78 8.78 8.78 8.78 8.78

Indiana Lake 14.33 10.45 10.45 10.45 10.45 10.45 10.45

Indiana Lake 13.83 10.06 10.06 10.06 10.06 10.06 10.06

Indiana Lake 14.02 10.37 10.37 10.37 10.37 10.37 10.37

Indiana Lake 14.05 10.27 10.27 10.27 10.27 10.27 10.27

Indiana Lake 13.89 10.11 10.11 10.11 10.11 10.11 10.11

Indiana LaPorte 12.49 8.9 8.9 8.9 8.9 8.9 8.9

Indiana LaPorte 12.69 9.03 9.03 9.03 9.03 9.03 9.03

Indiana Madison 13.97 9.34 9.34 9.34 9.34 9.34 9.34

Indiana Marion 14.24 9.28 9.28 9.28 9.28 9.28 9.28

Indiana Marion 15.26 10.16 10.16 10.16 10.16 10.16 10.16

(continued)
4.A-41

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Indiana Marion 14.71 9.7 9.7 9.7 9.7 9.7 9.7

Indiana Marion 16.05 10.81 10.81 10.81 10.81 10.81 10.81

Indiana Marion 15.9 10.66 10.66 10.66 10.66 10.66 10.66

Indiana Porter 12.66 8.99 8.99 8.99 8.99 8.99 8.99

Indiana Porter 13.21 9.42 9.42 9.42 9.42 9.42 9.42

Indiana St. Joseph 13.29 10.04 10.04 10.04 10.04 10.04 10.04

Indiana St. Joseph 13.69 10.36 10.36 10.36 10.36 10.36 10.36

Indiana St. Joseph 12.82 9.65 9.65 9.65 9.65 9.65 9.65

Indiana Spencer 14.32 8.55 8.55 8.55 8.55 8.55 8.55

Indiana Tippecanoe 13.7 9.4 9.4 9.4 9.4 9.4 9.4

Indiana Vanderburgh 14.69 9.82 9.82 9.82 9.82 9.82 9.82

Indiana Vanderburgh 14.82 9.9 9.9 9.9 9.9 9.9 9.9

Indiana Vanderburgh 14.99 10.06 10.06 10.06 10.06 10.06 10.06

Indiana Vigo 13.99 8.95 8.95 8.95 8.95 8.95 8.95

Indiana Vigo 13.46 8.51 8.51 8.51 8.51 8.51 8.51

Iowa Black Hawk 11.16 8.15 8.15 8.15 8.15 8.15 8.15

Iowa Clinton 12.52 9.01 9.01 9.01 9.01 9.01 9.01

Iowa Johnson 12.08 8.96 8.96 8.96 8.96 8.96 8.96

Iowa Linn 10.79 7.88 7.88 7.88 7.88 7.88 7.88

Iowa Montgomery 10.02 7.35 7.35 7.35 7.35 7.35 7.35

(continued)
4.A-42

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Iowa Muscatine 12.92 9.47 9.47 9.47 9.47 9.47 9.47

Iowa Palo Alto 9.53 7.21 7.21 7.21 7.21 7.21 7.21

Iowa Polk 10.41 7.68 7.68 7.68 7.68 7.68 7.68

Iowa Polk 9.95 7.34 7.34 7.34 7.34 7.34 7.34

Iowa Polk 10.64 7.85 7.85 7.85 7.85 7.85 7.85

Iowa Pottawattamie 11.13 8.42 8.42 8.42 8.42 8.42 8.42

Iowa Scott 11.86 8.52 8.52 8.52 8.52 8.52 8.52

Iowa Scott 11.64 8.35 8.35 8.35 8.35 8.35 8.35

Iowa Scott 14.42 10.62 10.62 10.62 10.62 10.62 10.62

Iowa Van Buren 10.84 7.98 7.98 7.98 7.98 7.98 7.98

Iowa Woodbury 10.32 7.93 7.93 7.93 7.93 7.93 7.93

Iowa Wright 10.37 7.68 7.68 7.68 7.68 7.68 7.68

Kansas Johnson 10.59 7.68 7.68 7.68 7.68 7.68 7.68

Kansas Johnson 11.1 8.04 8.04 8.04 8.04 8.04 8.04

Kansas Johnson 9.68 7 7 7 7 7 7

Kansas Linn 10.47 7.74 7.74 7.74 7.74 7.74 7.74

Kansas Sedgwick 10.26 7.55 7.55 7.55 7.55 7.55 7.55

Kansas Sedgwick 10.29 7.57 7.57 7.57 7.57 7.57 7.57

Kansas Sedgwick 10.36 7.64 7.64 7.64 7.64 7.64 7.64

Kansas Shawnee 10.79 8.07 8.07 8.07 8.07 8.07 8.07

(continued)
4.A-43

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Kansas Shawnee 10.93 8.26 8.26 8.26 8.26 8.26 8.26

Kansas Sumner 9.89 7.4 7.4 7.4 7.4 7.4 7.4

Kansas Wyandotte 12.73 9.34 9.34 9.34 9.34 9.34 9.34

Kansas Wyandotte 10.93 7.92 7.92 7.92 7.92 7.92 7.92

Kentucky Bell 14.1 8.59 8.59 8.59 8.59 8.59 8.59

Kentucky Boyd 14.49 8.77 8.77 8.77 8.77 8.77 8.77

Kentucky Bullitt 14.92 9.15 9.15 9.15 9.15 9.15 9.15

Kentucky Campbell 13.67 8.13 8.13 8.13 8.13 8.13 8.13

Kentucky Carter 12.22 7.08 7.08 7.08 7.08 7.08 7.08

Kentucky Christian 13.2 8.02 8.02 8.02 8.02 8.02 8.02

Kentucky Daviess 14.1 8.25 8.25 8.25 8.25 8.25 8.25

Kentucky Fayette 14.36 8.64 8.64 8.64 8.64 8.64 8.64

Kentucky Fayette 14.87 9.05 9.05 9.05 9.05 9.05 9.05

Kentucky Franklin 13.37 7.93 7.93 7.93 7.93 7.93 7.93

Kentucky Hardin 13.58 8.04 8.04 8.04 8.04 8.04 8.04

Kentucky Henderson 13.93 8.89 8.89 8.89 8.89 8.89 8.89

Kentucky Jefferson 15.55 9.43 9.43 9.43 9.43 9.43 9.43

Kentucky Jefferson 15.35 9.29 9.29 9.29 9.29 9.29 9.29

Kentucky Jefferson 15.31 9.26 9.26 9.26 9.26 9.26 9.26

Kentucky Jefferson 14.74 8.84 8.84 8.84 8.84 8.84 8.84

(continued)
4.A-44

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Kentucky Kenton 14.39 8.73 8.73 8.73 8.73 8.73 8.73

Kentucky Laurel 12.55 7.4 7.4 7.4 7.4 7.4 7.4

Kentucky McCracken 13.41 8.39 8.39 8.39 8.39 8.39 8.39

Kentucky Madison 13.61 8.01 8.01 8.01 8.01 8.01 8.01

Kentucky Perry 13.21 7.98 7.98 7.98 7.98 7.98 7.98

Kentucky Pike 13.49 7.94 7.94 7.94 7.94 7.94 7.94

Kentucky Warren 13.83 8.29 8.29 8.29 8.29 8.29 8.29

Louisiana Caddo 12.53 8.76 8.76 8.76 8.76 8.76 8.76

Louisiana Calcasieu 10.58 7.66 7.66 7.66 7.66 7.66 7.66

Louisiana Calcasieu 11.07 8.05 8.05 8.05 8.05 8.05 8.05

Louisiana Concordia 11.42 7.81 7.81 7.81 7.81 7.81 7.81

Louisiana East Baton Rouge 13.38 9.86 9.86 9.86 9.86 9.86 9.86

Louisiana East Baton Rouge 12.08 8.74 8.74 8.74 8.74 8.74 8.74

Louisiana Iberville 12.9 9.44 9.44 9.44 9.44 9.44 9.44

Louisiana Iberville 11.02 7.68 7.68 7.68 7.68 7.68 7.68

Louisiana Jefferson 11.52 7.53 7.53 7.53 7.53 7.53 7.53

Louisiana Lafayette 11.08 7.62 7.62 7.62 7.62 7.62 7.62

Louisiana Ouachita 11.97 8.63 8.63 8.63 8.63 8.63 8.63

Louisiana Rapides 11.03 7.64 7.64 7.64 7.64 7.64 7.64

Louisiana Tangipahoa 12.03 8.14 8.14 8.14 8.14 8.14 8.14

(continued)
4.A-45

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Louisiana Terrebonne 10.74 7.32 7.32 7.32 7.32 7.32 7.32

Louisiana West Baton Rouge 13.51 9.96 9.96 9.96 9.96 9.96 9.96

Maine Androscoggin 9.9 6.85 6.85 6.85 6.85 6.85 6.85

Maine Aroostook 9.74 8.73 8.73 8.73 8.73 8.73 8.73

Maine Aroostook 8.27 6.85 6.85 6.85 6.85 6.85 6.85

Maine Cumberland 11.06 7.51 7.51 7.51 7.51 7.51 7.51

Maine Cumberland 11.13 7.61 7.61 7.61 7.61 7.61 7.61

Maine Hancock 5.76 4.24 4.24 4.24 4.24 4.24 4.24

Maine Kennebec 9.99 7 7 7 7 7 7

Maine Oxford 10.13 7.65 7.65 7.65 7.65 7.65 7.65

Maine Penobscot 9.12 6.66 6.66 6.66 6.66 6.66 6.66

Maryland Anne Arundel 11.91 7.3 7.3 7.3 7.3 7.3 7.3

Maryland Anne Arundel 14.82 9.65 9.65 9.65 9.65 9.65 9.65

Maryland Anne Arundel 14.57 9.45 9.45 9.45 9.45 9.45 9.45

Maryland Baltimore 13.77 8.58 8.58 8.58 8.58 8.58 8.58

Maryland Baltimore 14.76 9.46 9.46 9.46 9.46 9.46 9.46

Maryland Cecil 12.68 7.81 7.81 7.81 7.81 7.81 7.81

Maryland Harford 12.51 7.62 7.62 7.62 7.62 7.62 7.62

Maryland Montgomery 12.47 7.77 7.77 7.77 7.77 7.77 7.77

Maryland Prince George’s 12.24 7.61 7.61 7.61 7.61 7.61 7.61

(continued)
4.A-46

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Maryland Prince George’s 13.03 8.06 8.06 8.06 8.06 8.06 8.06

Maryland Washington 13.7 8.64 8.64 8.64 8.64 8.64 8.64

Maryland Baltimore (City) 14.12 8.99 8.99 8.99 8.99 8.99 8.99

Maryland Baltimore (City) 14.38 9.08 9.08 9.08 9.08 9.08 9.08

Maryland Baltimore (City) 15.76 10.14 10.14 10.14 10.14 10.14 10.14

Maryland Baltimore (City) 15.63 10.13 10.13 10.13 10.13 10.13 10.13

Massachusetts Berkshire 10.65 7.34 7.34 7.34 7.34 7.34 7.34

Massachusetts Bristol 9.58 6.5 6.5 6.5 6.5 6.5 6.5

Massachusetts Essex 9.03 6.36 6.36 6.36 6.36 6.36 6.36

Massachusetts Essex 9.1 6.42 6.42 6.42 6.42 6.42 6.42

Massachusetts Essex 9.58 6.74 6.74 6.74 6.74 6.74 6.74

Massachusetts Hampden 9.85 6.73 6.73 6.73 6.73 6.73 6.73

Massachusetts Hampden 12.17 8.29 8.29 8.29 8.29 8.29 8.29

Massachusetts Hampden 11.85 8.08 8.08 8.08 8.08 8.08 8.08

Massachusetts Plymouth 9.87 6.87 6.87 6.87 6.87 6.87 6.87

Massachusetts Suffolk 12.34 8.79 8.79 8.79 8.79 8.79 8.79

Massachusetts Suffolk 11.86 8.35 8.35 8.35 8.35 8.35 8.35

Massachusetts Suffolk 10.88 7.7 7.7 7.7 7.7 7.7 7.7

Massachusetts Suffolk 13.07 9.3 9.3 9.3 9.3 9.3 9.3

Massachusetts Worcester 10.55 7.19 7.19 7.19 7.19 7.19 7.19

(continued)
4.A-47

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Massachusetts Worcester 11.29 7.69 7.69 7.69 7.69 7.69 7.69

Michigan Allegan 11.84 8.31 8.31 8.31 8.31 8.31 8.31

Michigan Bay 10.93 7.94 7.94 7.94 7.94 7.94 7.94

Michigan Berrien 11.72 8.34 8.34 8.34 8.34 8.34 8.34

Michigan Genesee 11.61 8.28 8.28 8.28 8.28 8.28 8.28

Michigan Ingham 12.23 8.64 8.64 8.64 8.64 8.64 8.64

Michigan Kalamazoo 12.84 9.19 9.19 9.19 9.19 9.19 9.19

Michigan Kent 12.89 9.17 9.17 9.17 9.17 9.17 9.17

Michigan Macomb 12.7 9.13 9.13 9.13 9.13 9.13 9.13

Michigan Missaukee 8.26 6.33 6.33 6.33 6.33 6.33 6.33

Michigan Monroe 13.92 9.46 9.46 9.46 9.46 9.46 9.46

Michigan Muskegon 11.61 8.39 8.39 8.39 8.39 8.39 8.39

Michigan Oakland 13.78 9.62 9.62 9.62 9.62 9.62 9.62

Michigan Ottawa 12.55 8.87 8.87 8.87 8.87 8.87 8.87

Michigan Saginaw 10.61 7.74 7.74 7.74 7.74 7.74 7.74

Michigan St. Clair 13.34 9.87 9.87 9.87 9.87 9.87 9.87

Michigan Washtenaw 12.3 8.58 8.58 8.58 8.58 8.58 8.58

Michigan Washtenaw 13.88 9.82 9.82 9.82 9.82 9.82 9.82

Michigan Wayne 14.52 10.33 10.33 10.33 9.802 8.92 8.92

Michigan Wayne 15.88 11.17 11.17 11.17 10.64 9.76 9.76

(continued)
4.A-48

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Michigan Wayne 14.57 10.34 10.34 10.34 9.812 8.93 8.93

Michigan Wayne 14.32 10.3 10.3 10.3 9.772 8.89 8.89

Michigan Wayne 13.39 9.28 9.28 9.28 8.75 7.87 7.87

Michigan Wayne 17.5 12.35 12.35 12.35 11.82 10.94 10.94

Michigan Wayne 14.67 10.44 10.44 10.44 9.912 9.03 9.03

Minnesota Cass 5.7 4.79 4.79 4.79 4.79 4.79 4.79

Minnesota Dakota 9.3 7.09 7.09 7.09 7.09 7.09 7.09

Minnesota Hennepin 9.76 7.39 7.39 7.39 7.39 7.39 7.39

Minnesota Hennepin 9.14 6.93 6.93 6.93 6.93 6.93 6.93

Minnesota Hennepin 9.59 7.25 7.25 7.25 7.25 7.25 7.25

Minnesota Hennepin 9.54 7.23 7.23 7.23 7.23 7.23 7.23

Minnesota Hennepin 9.56 7.26 7.26 7.26 7.26 7.26 7.26

Minnesota Hennepin 9.33 7.07 7.07 7.07 7.07 7.07 7.07

Minnesota Mille Lacs 6.54 5.3 5.3 5.3 5.3 5.3 5.3

Minnesota Olmsted 10.13 7.6 7.6 7.6 7.6 7.6 7.6

Minnesota Ramsey 11.32 8.68 8.68 8.68 8.68 8.68 8.68

Minnesota Ramsey 11.02 8.34 8.34 8.34 8.34 8.34 8.34

Minnesota Ramsey 9.63 7.36 7.36 7.36 7.36 7.36 7.36

Minnesota Saint Louis 6.1 5.04 5.04 5.04 5.04 5.04 5.04

Minnesota Saint Louis 6.19 4.97 4.97 4.97 4.97 4.97 4.97

(continued)
4.A-49

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Minnesota Saint Louis 7.51 5.99 5.99 5.99 5.99 5.99 5.99

Minnesota Scott 9 6.9 6.9 6.9 6.9 6.9 6.9

Minnesota Stearns 8.58 6.8 6.8 6.8 6.8 6.8 6.8

Mississippi Adams 11.29 7.66 7.66 7.66 7.66 7.66 7.66

Mississippi Bolivar 12.36 8.56 8.56 8.56 8.56 8.56 8.56

Mississippi DeSoto 12.43 7.95 7.95 7.95 7.95 7.95 7.95

Mississippi Forrest 13.62 9.03 9.03 9.03 9.03 9.03 9.03

Mississippi Harrison 12.2 8.16 8.16 8.16 8.16 8.16 8.16

Mississippi Hinds 12.56 8.43 8.43 8.43 8.43 8.43 8.43

Mississippi Jackson 12.04 7.9 7.9 7.9 7.9 7.9 7.9

Mississippi Jones 14.39 9.56 9.56 9.56 9.56 9.56 9.56

Mississippi Lauderdale 13.07 8.62 8.62 8.62 8.62 8.62 8.62

Mississippi Lee 12.57 8.06 8.06 8.06 8.06 8.06 8.06

Mississippi Lowndes 12.79 8.42 8.42 8.42 8.42 8.42 8.42

Mississippi Pearl River 12.14 8.25 8.25 8.25 8.25 8.25 8.25

Mississippi Warren 12.32 8.51 8.51 8.51 8.51 8.51 8.51

Missouri Boone 11.84 8.45 8.45 8.45 8.45 8.45 8.45

Missouri Buchanan 12.8 9.75 9.75 9.75 9.75 9.75 9.75

Missouri Cass 10.67 7.76 7.76 7.76 7.76 7.76 7.76

Missouri Cedar 11.12 7.89 7.89 7.89 7.89 7.89 7.89

(continued)
4.A-50

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Missouri Clay 11.03 8.1 8.1 8.1 8.1 8.1 8.1

Missouri Greene 11.75 8.32 8.32 8.32 8.32 8.32 8.32

Missouri Jackson 12.78 9.33 9.33 9.33 9.33 9.33 9.33

Missouri Jefferson 13.79 9.57 9.57 9.57 9.57 9.57 9.57

Missouri Monroe 10.87 7.59 7.59 7.59 7.59 7.59 7.59

Missouri Saint Charles 13.29 9.12 9.12 9.12 9.12 9.12 9.12

Missouri Sainte Genevieve 13.34 9.06 9.06 9.06 9.06 9.06 9.06

Missouri Saint Louis 13.04 8.9 8.9 8.9 8.9 8.9 8.9

Missouri Saint Louis 13.46 9.07 9.07 9.07 9.07 9.07 9.07

Missouri St. Louis City 14.27 9.74 9.74 9.74 9.74 9.74 9.74

Missouri St. Louis City 14.36 9.71 9.71 9.71 9.71 9.71 9.71

Missouri St. Louis City 13.44 9.03 9.03 9.03 9.03 9.03 9.03

Missouri St. Louis City 14.56 9.84 9.84 9.84 9.84 9.84 9.84

Montana Cascade 5.72 5.01 5.01 5.01 5.01 5.01 5.01

Montana Flathead 9.99 8.52 8.46 8.46 8.46 8.36 8.33

Montana Flathead 8.58 7.28 7.23 7.23 7.23 7.13 7.11

Montana Gallatin 4.38 4.13 4.13 4.13 4.13 4.13 4.13

Montana Lake 9.06 7.81 7.05 7.05 7.05 6.95 5.74

Montana Lake 9 7.71 6.94 6.94 6.94 6.83 5.62

Montana Lewis and Clark 8.2 7.19 7.19 7.19 7.19 7.19 7.19

(continued)
4.A-51

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Montana Lincoln 14.93 12.6 12.53 12.53 12.04 11.01 11.04

Montana Missoula 10.52 9.13 8.33 8.33 8.33 8.19 7.28

Montana Ravalli 9.01 7.89 7.40 7.40 7.40 7.32 6.08

Montana Rosebud 6.58 6.1 6.1 6.1 6.1 6.1 6.1

Montana Sanders 6.75 6.04 6.00 6.00 6.00 5.91 5.89

Montana Silver Bow 10.14 8.69 8.69 8.69 8.69 8.69 8.69

Montana Yellowstone 8.14 6.84 6.84 6.84 6.84 6.84 6.84

Nebraska Cass 9.99 7.48 7.48 7.48 7.48 7.48 7.48

Nebraska Douglas 9.88 7.41 7.41 7.41 7.41 7.41 7.41

Nebraska Douglas 9.85 7.4 7.4 7.4 7.4 7.4 7.4

Nebraska Hall 7.95 6.13 6.13 6.13 6.13 6.13 6.13

Nebraska Lancaster 8.9 6.53 6.53 6.53 6.53 6.53 6.53

Nebraska Lincoln 7.57 6.32 6.32 6.32 6.32 6.32 6.32

Nebraska Sarpy 9.79 7.33 7.33 7.33 7.33 7.33 7.33

Nebraska Scotts Bluff 6.04 5.17 5.17 5.17 5.17 5.17 5.17

Nebraska Washington 9.29 7.1 7.1 7.1 7.1 7.1 7.1

Nevada Clark 4.02 3.64 3.64 3.64 3.64 3.64 3.64

Nevada Clark 5.75 4.97 4.97 4.97 4.97 4.97 4.97

Nevada Clark 9.44 8.08 8.08 8.08 8.08 8.08 8.08

Nevada Clark 3.67 3.3 3.3 3.3 3.3 3.3 3.3

(continued)
4.A-52

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Nevada Clark 8.49 7.28 7.28 7.28 7.28 7.28 7.28

Nevada Washoe 8.11 6.39 6.39 6.39 6.39 6.39 6.39

New Hampshire Belknap 7.28 5.12 5.12 5.12 5.12 5.12 5.12

New Hampshire Cheshire 11.53 7.96 7.96 7.96 7.96 7.96 7.96

New Hampshire Coos 10.24 8.01 8.01 8.01 8.01 8.01 8.01

New Hampshire Grafton 8.43 6.08 6.08 6.08 6.08 6.08 6.08

New Hampshire Hillsborough 10.18 7.08 7.08 7.08 7.08 7.08 7.08

New Hampshire Hillsborough 10.01 7.01 7.01 7.01 7.01 7.01 7.01

New Hampshire Hillsborough 6.27 4.3 4.3 4.3 4.3 4.3 4.3

New Hampshire Merrimack 9.72 6.76 6.76 6.76 6.76 6.76 6.76

New Hampshire Rockingham 9 6.26 6.26 6.26 6.26 6.26 6.26

New Hampshire Sullivan 9.86 7.01 7.01 7.01 7.01 7.01 7.01

New Jersey Atlantic 11.47 6.96 6.96 6.96 6.96 6.96 6.96

New Jersey Bergen 13.09 8.9 8.9 8.9 8.9 8.9 8.9

New Jersey Camden 13.31 8.49 8.49 8.49 8.49 8.49 8.49

New Jersey Camden 13.51 8.53 8.53 8.53 8.53 8.53 8.53

New Jersey Essex 13.27 8.74 8.74 8.74 8.74 8.74 8.74

New Jersey Gloucester 13.46 8.46 8.46 8.46 8.46 8.46 8.46

New Jersey Hudson 14.24 9.65 9.65 9.65 9.65 9.65 9.65

New Jersey Mercer 12.71 8.14 8.14 8.14 8.14 8.14 8.14

(continued)
4.A-53

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

New Jersey Mercer 11.14 7 7 7 7 7 7

New Jersey Middlesex 12.15 7.91 7.91 7.91 7.91 7.91 7.91

New Jersey Morris 11.5 7.42 7.42 7.42 7.42 7.42 7.42

New Jersey Morris 10.21 6.56 6.56 6.56 6.56 6.56 6.56

New Jersey Ocean 10.92 6.85 6.85 6.85 6.85 6.85 6.85

New Jersey Passaic 12.88 8.59 8.59 8.59 8.59 8.59 8.59

New Jersey Union 14.94 9.88 9.88 9.88 9.88 9.88 9.88

New Jersey Union 13.32 8.73 8.73 8.73 8.73 8.73 8.73

New Jersey Union 13.06 8.45 8.45 8.45 8.45 8.45 8.45

New Jersey Warren 12.72 8.2 8.2 8.2 8.2 8.2 8.2

New Mexico Bernalillo 7.03 5.74 5.74 5.74 5.74 5.74 5.74

New Mexico Bernalillo 6.64 5.41 5.41 5.41 5.41 5.41 5.41

New Mexico Chaves 6.54 5.68 5.68 5.68 5.68 5.68 5.68

New Mexico Dona Ana 9.95 8.7 8.7 8.7 8.7 8.7 8.7

New Mexico Dona Ana 6.31 5.55 5.55 5.55 5.55 5.55 5.55

New Mexico Grant 5.93 5.5 5.5 5.5 5.5 5.5 5.5

New Mexico Sandoval 5 4.12 4.12 4.12 4.12 4.12 4.12

New Mexico Sandoval 7.99 7.15 7.15 7.15 7.15 7.15 7.15

New Mexico San Juan 5.92 5.23 5.23 5.23 5.23 5.23 5.23

New Mexico Santa Fe 4.76 4.22 4.22 4.22 4.22 4.22 4.22

(continued)
4.A-54

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

New York Albany 11.83 8.43 8.43 8.43 8.43 8.43 8.43

New York Bronx 15.43 10.87 10.87 10.87 10.87 10.87 10.87

New York Bronx 13.09 8.68 8.68 8.68 8.68 8.68 8.68

New York Bronx 13.45 9.41 9.41 9.41 9.41 9.41 9.41

New York Chautauqua 9.8 6.32 6.32 6.32 6.32 6.32 6.32

New York Erie 12.62 8.69 8.69 8.69 8.69 8.69 8.69

New York Erie 12.64 8.65 8.65 8.65 8.65 8.65 8.65

New York Essex 5.94 4.43 4.43 4.43 4.43 4.43 4.43

New York Kings 14.2 9.67 9.67 9.67 9.67 9.67 9.67

New York Monroe 10.64 7.63 7.63 7.63 7.63 7.63 7.63

New York Nassau 11.66 7.69 7.69 7.69 7.69 7.69 7.69

New York New York 16.18 11.17 11.17 11.17 11.17 9.88 10.20

New York New York 14.8 10.06 10.06 10.06 10.06 8.77 9.09

New York New York 13.61 9.48 9.48 9.48 9.48 8.19 8.51

New York New York 15.41 10.6 10.6 10.6 10.6 9.31 9.63

New York Niagara 11.96 8.55 8.55 8.55 8.55 8.55 8.55

New York Onondaga 10.08 6.89 6.89 6.89 6.89 6.89 6.89

New York Orange 10.99 7.28 7.28 7.28 7.28 7.28 7.28

New York Queens 12.18 8.15 8.15 8.15 8.15 8.15 8.15

New York Richmond 13.31 8.72 8.72 8.72 8.72 8.72 8.72

(continued)
4.A-55

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

New York Richmond 11.59 7.58 7.58 7.58 7.58 7.58 7.58

New York St. Lawrence 7.29 5.6 5.6 5.6 5.6 5.6 5.6

New York Steuben 9 5.83 5.83 5.83 5.83 5.83 5.83

New York Suffolk 11.52 7.51 7.51 7.51 7.51 7.51 7.51

New York Westchester 11.73 7.7 7.7 7.7 7.7 7.7 7.7

North Carolina Alamance 13.94 8.38 8.38 8.38 8.38 8.38 8.38

North Carolina Buncombe 12.6 7.71 7.71 7.71 7.71 7.71 7.71

North Carolina Caswell 13.19 7.74 7.74 7.74 7.74 7.74 7.74

North Carolina Catawba 15.31 9.17 9.17 9.17 9.17 9.17 9.17

North Carolina Chatham 11.99 7.07 7.07 7.07 7.07 7.07 7.07

North Carolina Cumberland 13.73 8.77 8.77 8.77 8.77 8.77 8.77

North Carolina Davidson 15.17 8.89 8.89 8.89 8.89 8.89 8.89

North Carolina Duplin 11.3 6.97 6.97 6.97 6.97 6.97 6.97

North Carolina Durham 13.57 8.31 8.31 8.31 8.31 8.31 8.31

North Carolina Edgecombe 12.37 7.76 7.76 7.76 7.76 7.76 7.76

North Carolina Forsyth 14.28 8.28 8.28 8.28 8.28 8.28 8.28

North Carolina Gaston 14.26 8.4 8.4 8.4 8.4 8.4 8.4

North Carolina Guilford 13.79 8.17 8.17 8.17 8.17 8.17 8.17

North Carolina Haywood 12.98 8.54 8.54 8.54 8.54 8.54 8.54

North Carolina Jackson 12.09 7.42 7.42 7.42 7.42 7.42 7.42

(continued)
4.A-56

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

North Carolina Lenoir 11.12 6.88 6.88 6.88 6.88 6.88 6.88

North Carolina McDowell 14.24 8.92 8.92 8.92 8.92 8.92 8.92

North Carolina Martin 10.86 6.71 6.71 6.71 6.71 6.71 6.71

North Carolina Mecklenburg 15.31 9.25 9.25 9.25 9.25 9.25 9.25

North Carolina Mecklenburg 14.74 8.77 8.77 8.77 8.77 8.77 8.77

North Carolina Mecklenburg 14.8 8.82 8.82 8.82 8.82 8.82 8.82

North Carolina Mitchell 12.75 7.61 7.61 7.61 7.61 7.61 7.61

North Carolina Montgomery 12.35 7.33 7.33 7.33 7.33 7.33 7.33

North Carolina New Hanover 9.96 6.14 6.14 6.14 6.14 6.14 6.14

North Carolina Onslow 10.98 6.77 6.77 6.77 6.77 6.77 6.77

North Carolina Orange 13.12 7.86 7.86 7.86 7.86 7.86 7.86

North Carolina Pitt 11.59 7.26 7.26 7.26 7.26 7.26 7.26

North Carolina Robeson 12.78 8.03 8.03 8.03 8.03 8.03 8.03

North Carolina Rowan 14.02 8.35 8.35 8.35 8.35 8.35 8.35

North Carolina Swain 12.65 7.76 7.76 7.76 7.76 7.76 7.76

North Carolina Wake 13.54 8.3 8.3 8.3 8.3 8.3 8.3

North Carolina Watauga 12.05 6.85 6.85 6.85 6.85 6.85 6.85

North Carolina Wayne 12.96 8.31 8.31 8.31 8.31 8.31 8.31

North Dakota Billings 4.61 4.18 4.18 4.18 4.18 4.18 4.18

North Dakota Burke 5.9 5.51 5.51 5.51 5.51 5.51 5.51

(continued)
4.A-57

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

North Dakota Burke 5.78 5.35 5.35 5.35 5.35 5.35 5.35

North Dakota Burleigh 6.61 5.59 5.59 5.59 5.59 5.59 5.59

North Dakota Cass 7.72 6.44 6.44 6.44 6.44 6.44 6.44

North Dakota McKenzie 5.01 4.59 4.59 4.59 4.59 4.59 4.59

North Dakota Mercer 6.04 5.38 5.38 5.38 5.38 5.38 5.38

Ohio Athens 12.39 7.12 7.12 7.12 7.12 7.12 7.12

Ohio Butler 15.74 9.9 9.9 9.9 9.9 9.9 9.9

Ohio Butler 15.36 10.08 10.08 10.08 10.08 10.08 10.08

Ohio Butler 14.9 9.63 9.63 9.63 9.63 9.63 9.63

Ohio Clark 14.64 9.55 9.55 9.55 9.55 9.55 9.55

Ohio Clermont 14.15 8.58 8.58 8.58 8.58 8.58 8.58

Ohio Cuyahoga 15.46 10.28 10.28 10.28 10.28 9.53 9.53

Ohio Cuyahoga 13.76 9.08 9.08 9.08 9.08 8.34 8.34

Ohio Cuyahoga 17.37 11.79 11.79 11.79 11.79 11.04 11.04

Ohio Cuyahoga 16.47 11.04 11.04 11.04 11.04 10.29 10.29

Ohio Cuyahoga 17.11 11.51 11.51 11.51 11.51 10.76 10.76

Ohio Cuyahoga 15.97 10.64 10.64 10.64 10.64 9.89 9.89

Ohio Cuyahoga 14.14 9.45 9.45 9.45 9.45 8.71 8.71

Ohio Franklin 15.27 9.82 9.82 9.82 9.82 9.82 9.82

Ohio Franklin 15.08 9.7 9.7 9.7 9.7 9.7 9.7

(continued)
4.A-58

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Ohio Franklin 14.33 9.18 9.18 9.18 9.18 9.18 9.18

Ohio Greene 13.36 8.34 8.34 8.34 8.34 8.34 8.34

Ohio Hamilton 14.84 9.18 9.18 9.18 9.18 9.18 9.18

Ohio Hamilton 17.29 10.81 10.81 10.81 10.81 10.81 10.81

Ohio Hamilton 15.5 9.45 9.45 9.45 9.45 9.45 9.45

Ohio Hamilton 16.85 10.63 10.63 10.63 10.63 10.63 10.63

Ohio Hamilton 15.55 9.76 9.76 9.76 9.76 9.76 9.76

Ohio Hamilton 16.17 9.99 9.99 9.99 9.99 9.99 9.99

Ohio Hamilton 17.54 11.04 11.04 11.04 11.04 11.04 11.04

Ohio Jefferson 15.41 9.33 9.33 9.33 9.33 9.33 9.33

Ohio Jefferson 16.51 9.96 9.96 9.96 9.96 9.96 9.96

Ohio Lake 13.02 8.67 8.67 8.67 8.67 8.60 8.60

Ohio Lawrence 15.14 9.51 9.51 9.51 9.51 9.51 9.51

Ohio Lorain 13.87 9.12 9.12 9.12 9.12 9.05 9.05

Ohio Lorain 12.78 8.73 8.73 8.73 8.73 8.67 8.67

Ohio Lucas 14.38 9.88 9.88 9.88 9.88 9.88 9.88

Ohio Lucas 13.95 9.52 9.52 9.52 9.52 9.52 9.52

Ohio Lucas 14.08 9.73 9.73 9.73 9.73 9.73 9.73

Ohio Mahoning 14.68 9.47 9.47 9.47 9.47 9.47 9.47

Ohio Mahoning 15.12 9.9 9.9 9.9 9.9 9.9 9.9

(continued)
4.A-59

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Ohio Montgomery 14.58 9.31 9.31 9.31 9.31 9.31 9.31

Ohio Montgomery 15.54 10 10 10 10 10 10

Ohio Portage 13.37 8.7 8.7 8.7 8.7 8.63 8.63

Ohio Preble 13.7 8.8 8.8 8.8 8.8 8.8 8.8

Ohio Scioto 14.65 8.86 8.86 8.86 8.86 8.86 8.86

Ohio Stark 16.26 10.41 10.41 10.41 10.41 10.41 10.41

Ohio Stark 15.23 10.07 10.07 10.07 10.07 10.07 10.07

Ohio Summit 15.17 10.15 10.15 10.15 10.15 10.08 10.08

Ohio Summit 14.26 9.54 9.54 9.54 9.54 9.47 9.47

Ohio Trumbull 14.53 9.53 9.53 9.53 9.53 9.53 9.53

Oklahoma Caddo 9.22 6.9 6.9 6.9 6.9 6.9 6.9

Oklahoma Cherokee 11.79 8.59 8.59 8.59 8.59 8.59 8.59

Oklahoma Kay 10.26 7.84 7.84 7.84 7.84 7.84 7.84

Oklahoma Lincoln 10.28 7.54 7.54 7.54 7.54 7.54 7.54

Oklahoma Mayes 11.7 8.64 8.64 8.64 8.64 8.64 8.64

Oklahoma Mayes 11.44 8.38 8.38 8.38 8.38 8.38 8.38

Oklahoma Muskogee 11.89 8.85 8.85 8.85 8.85 8.85 8.85

Oklahoma Oklahoma 10.07 7.25 7.25 7.25 7.25 7.25 7.25

Oklahoma Oklahoma 9.86 7.08 7.08 7.08 7.08 7.08 7.08

Oklahoma Ottawa 11.69 8.63 8.63 8.63 8.63 8.63 8.63

(continued)
4.A-60

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Oklahoma Pittsburg 11.09 8.09 8.09 8.09 8.09 8.09 8.09

Oklahoma Sequoyah 12.99 9.68 9.68 9.68 9.68 9.68 9.68

Oklahoma Tulsa 11.52 8.45 8.45 8.45 8.45 8.45 8.45

Oklahoma Tulsa 11.37 8.41 8.41 8.41 8.41 8.41 8.41

Oregon Jackson 10.32 7.68 7.68 7.68 7.68 7.68 7.68

Oregon Jackson 5.41 4.24 4.24 4.24 4.24 4.24 4.24

Oregon Klamath 11.2 8.54 8.54 8.54 8.54 8.54 8.37

Oregon Lane 8.64 6.39 6.39 6.39 6.39 6.39 5.35

Oregon Lane 6.35 4.89 4.89 4.89 4.89 4.89 3.85

Oregon Lane 7.56 5.75 5.75 5.75 5.75 5.75 4.71

Oregon Lane 11.93 9.43 9.43 9.43 9.43 9.43 8.39

Oregon Multnomah 9.13 6.23 6.23 6.23 6.23 6.23 6.23

Oregon Multnomah 8.35 5.81 5.81 5.81 5.81 5.81 5.81

Oregon Union 8.35 6.74 6.74 6.74 6.74 6.74 6.74

Pennsylvania Adams 13.05 8.16 8.16 8.16 8.16 8.16 8.16

Pennsylvania Allegheny 15.24 9.75 7.92 7.92 7.92 7.89 6.27

Pennsylvania Allegheny 14.66 9.26 7.43 7.43 7.43 7.40 5.78

Pennsylvania Allegheny 20.31 12.91 11.08 11.08 11.08 11.04 9.43

Pennsylvania Allegheny 13.07 7.8 5.98 5.98 5.98 5.95 4.33

Pennsylvania Allegheny 13.84 8.49 6.66 6.66 6.66 6.63 5.01

(continued)
4.A-61

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Pennsylvania Allegheny 15.36 9.76 7.93 7.93 7.93 7.90 6.28

Pennsylvania Allegheny 15.25 9.33 7.50 7.50 7.50 7.47 5.85

Pennsylvania Allegheny 16.26 10.06 8.23 8.23 8.23 8.20 6.58

Pennsylvania Allegheny 15.3 9.43 7.60 7.60 7.60 7.57 5.95

Pennsylvania Allegheny 14.44 8.84 7.01 7.01 7.01 6.98 5.36

Pennsylvania Beaver 16.38 10.51 10.46 10.46 10.46 10.46 10.46

Pennsylvania Berks 15.82 10.58 10.58 10.58 10.58 10.58 10.58

Pennsylvania Bucks 13.42 8.45 8.45 8.45 8.45 8.45 8.45

Pennsylvania Cambria 15.4 9.45 9.45 9.45 9.45 9.45 9.45

Pennsylvania Centre 12.78 8 8 8 8 8 8

Pennsylvania Chester 15.22 9.64 9.64 9.64 9.64 9.64 9.64

Pennsylvania Cumberland 14.45 9.32 9.32 9.32 9.32 9.32 9.32

Pennsylvania Dauphin 15.13 9.54 9.54 9.54 9.54 9.54 9.54

Pennsylvania Delaware 15.23 9.74 9.74 9.74 9.74 9.74 9.74

Pennsylvania Erie 12.54 8.39 8.39 8.39 8.39 8.39 8.39

Pennsylvania Lackawanna 11.73 7.53 7.53 7.53 7.53 7.53 7.53

Pennsylvania Lancaster 16.55 10.73 10.73 10.73 10.73 10.73 10.71

Pennsylvania Lehigh 14.5 9.67 9.67 9.67 9.67 9.67 9.67

Pennsylvania Luzerne 12.76 8.39 8.39 8.39 8.39 8.39 8.39

Pennsylvania Mercer 13.28 8.47 8.47 8.47 8.47 8.47 8.47

(continued)
4.A-62

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Pennsylvania Northampton 13.68 8.96 8.96 8.96 8.96 8.96 8.96

Pennsylvania Perry 12.81 8.22 8.22 8.22 8.22 8.22 8.22

Pennsylvania Philadelphia 15.19 9.89 9.89 9.89 9.89 9.89 9.89

Pennsylvania Washington 15.17 8.95 8.90 8.90 8.90 8.90 8.90

Pennsylvania Washington 14.92 8.75 8.70 8.70 8.70 8.70 8.70

Pennsylvania Washington 13.37 8.2 8.15 8.15 8.15 8.15 8.15

Pennsylvania Westmoreland 15.49 9.26 9.21 9.21 9.21 9.21 9.21

Pennsylvania York 16.52 10.66 10.66 10.66 10.66 10.66 10.66

Rhode Island Providence 10.07 6.99 6.99 6.99 6.99 6.99 6.99

Rhode Island Providence 12.14 8.42 8.42 8.42 8.42 8.42 8.42

Rhode Island Providence 10.82 7.56 7.56 7.56 7.56 7.56 7.56

Rhode Island Providence 9.93 6.85 6.85 6.85 6.85 6.85 6.85

South Carolina Beaufort 11.52 7.25 7.25 7.25 7.25 7.25 7.25

South Carolina Charleston 12.21 7.86 7.86 7.86 7.86 7.86 7.86

South Carolina Charleston 11.6 7.13 7.13 7.13 7.13 7.13 7.13

South Carolina Chesterfield 12.56 7.86 7.86 7.86 7.86 7.86 7.86

South Carolina Edgefield 13.17 8.5 8.5 8.5 8.5 8.5 8.5

South Carolina Florence 12.65 8.02 8.02 8.02 8.02 8.02 8.02

South Carolina Georgetown 12.85 8.38 8.38 8.38 8.38 8.38 8.38

South Carolina Greenville 15.65 9.7 9.7 9.7 9.7 9.7 9.7

(continued)
4.A-63

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

South Carolina Greenville 14.66 8.91 8.91 8.91 8.91 8.91 8.91

South Carolina Greenwood 13.53 8.41 8.41 8.41 8.41 8.41 8.41

South Carolina Horry 12.04 7.68 7.68 7.68 7.68 7.68 7.68

South Carolina Lexington 14.64 9.28 9.28 9.28 9.28 9.28 9.28

South Carolina Oconee 10.95 6.45 6.45 6.45 6.45 6.45 6.45

South Carolina Richland 13.59 8.36 8.36 8.36 8.36 8.36 8.36

South Carolina Richland 14.24 8.89 8.89 8.89 8.89 8.89 8.89

South Carolina Spartanburg 14.17 8.58 8.58 8.58 8.58 8.58 8.58

South Dakota Brookings 9.37 7.52 7.52 7.52 7.52 7.52 7.52

South Dakota Brown 8.42 7.03 7.03 7.03 7.03 7.03 7.03

South Dakota Codington 10.14 8.35 8.35 8.35 8.35 8.35 8.35

South Dakota Custer 5.64 5.01 5.01 5.01 5.01 5.01 5.01

South Dakota Jackson 5.39 4.65 4.65 4.65 4.65 4.65 4.65

South Dakota Minnehaha 10.18 7.84 7.84 7.84 7.84 7.84 7.84

South Dakota Minnehaha 9.58 7.38 7.38 7.38 7.38 7.38 7.38

South Dakota Pennington 7.48 6.56 6.56 6.56 6.56 6.56 6.56

South Dakota Pennington 8.77 7.71 7.71 7.71 7.71 7.71 7.71

South Dakota Pennington 7.32 6.44 6.44 6.44 6.44 6.44 6.44

Tennessee Blount 14.3 9.09 9.09 9.09 9.09 9.09 9.09

Tennessee Davidson 14.21 8.87 8.87 8.87 8.87 8.87 8.87

(continued)
4.A-64

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Tennessee Davidson 13.99 8.63 8.63 8.63 8.63 8.63 8.63

Tennessee Davidson 12.97 7.85 7.85 7.85 7.85 7.85 7.85

Tennessee Dyer 12.28 7.8 7.8 7.8 7.8 7.8 7.8

Tennessee Hamilton 15.67 9.91 9.91 9.91 9.91 9.91 9.91

Tennessee Hamilton 13.73 8.18 8.18 8.18 8.18 8.18 8.18

Tennessee Hamilton 15.16 9.38 9.38 9.38 9.38 9.38 9.38

Tennessee Knox 15.47 9.66 9.66 9.66 9.66 9.66 9.66

Tennessee Knox 15.64 9.77 9.77 9.77 9.77 9.77 9.77

Tennessee Knox 15.18 9.24 9.24 9.24 9.24 9.24 9.24

Tennessee Lawrence 11.69 7.39 7.39 7.39 7.39 7.39 7.39

Tennessee Loudon 15.49 10.01 10.01 10.01 10.01 10.01 10.01

Tennessee McMinn 14.29 8.93 8.93 8.93 8.93 8.93 8.93

Tennessee Maury 13.21 8.39 8.39 8.39 8.39 8.39 8.39

Tennessee Montgomery 13.8 8.65 8.65 8.65 8.65 8.65 8.65

Tennessee Putnam 13.37 8.04 8.04 8.04 8.04 8.04 8.04

Tennessee Roane 14.49 8.94 8.94 8.94 8.94 8.94 8.94

Tennessee Shelby 13.71 8.73 8.73 8.73 8.73 8.73 8.73

Tennessee Shelby 13.43 8.47 8.47 8.47 8.47 8.47 8.47

Tennessee Shelby 13.68 8.6 8.6 8.6 8.6 8.6 8.6

Tennessee Shelby 12.04 7.53 7.53 7.53 7.53 7.53 7.53

(continued)
4.A-65

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Tennessee Sullivan 14.16 9.15 9.15 9.15 9.15 9.15 9.15

Tennessee Sumner 13.68 8.04 8.04 8.04 8.04 8.04 8.04

Texas Bowie 12.85 9.21 9.21 9.21 9.21 9.21 9.21

Texas Dallas 12.77 8.98 8.98 8.98 8.98 8.98 8.98

Texas Dallas 11.8 8.16 8.16 8.16 8.16 8.16 8.16

Texas Dallas 11.15 7.54 7.54 7.54 7.54 7.54 7.54

Texas Ector 7.78 6.52 6.52 6.52 6.52 6.52 6.52

Texas El Paso 9.09 7.94 7.94 7.94 7.94 7.94 7.94

Texas Harris 11.77 8.65 8.65 8.65 8.65 7.94 7.94

Texas Harris 15.42 11.61 11.61 11.61 11.61 10.90 10.90

Texas Harrison 11.69 7.91 7.91 7.91 7.91 7.91 7.91

Texas Hidalgo 10.98 9.17 9.17 9.17 9.17 9.17 9.17

Texas Jefferson 11.56 8.26 8.26 8.26 8.26 8.26 8.26

Texas Nueces 10.42 7.69 7.69 7.69 7.69 7.69 7.69

Texas Nueces 9.63 7.04 7.04 7.04 7.04 7.04 7.04

Texas Orange 11.51 8.37 8.37 8.37 8.37 8.37 8.37

Texas Tarrant 11.41 7.77 7.77 7.77 7.77 7.77 7.77

Texas Tarrant 12.23 8.41 8.41 8.41 8.41 8.41 8.41

Utah Box Elder 8.4 7.16 7.10 7.10 7.10 7.10 7.09

Utah Cache 11.56 9.78 8.32 8.32 8.32 8.32 7.30

(continued)
4.A-66

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Utah Davis 10.31 8.58 8.58 8.58 8.58 8.58 8.21

Utah Salt Lake 11.68 9.29 9.00 9.00 9.00 9.00 8.01

Utah Salt Lake 9.21 7.75 7.46 7.46 7.46 7.46 6.47

Utah Salt Lake 11.3 9.05 8.76 8.76 8.76 8.76 7.77

Utah Salt Lake 12.02 9.72 9.43 9.43 9.43 9.43 8.43

Utah Salt Lake 8.33 6.91 6.62 6.62 6.62 6.62 5.66

Utah Utah 10 8.37 8.37 8.37 8.37 8.37 7.48

Utah Utah 10.52 8.8 8.8 8.8 8.8 8.8 7.91

Utah Utah 8.88 7.44 7.44 7.44 7.44 7.44 6.57

Utah Utah 8.78 7.37 7.37 7.37 7.37 7.37 6.50

Utah Weber 11.16 9.23 9.16 9.16 9.16 9.16 9.15

Utah Weber 9.28 7.71 7.64 7.64 7.64 7.64 7.64

Utah Weber 9.36 7.8 7.73 7.73 7.73 7.73 7.72

Vermont Addison 8.94 6.75 6.75 6.75 6.75 6.75 6.75

Vermont Addison 8.91 6.71 6.71 6.71 6.71 6.71 6.71

Vermont Bennington 8.52 6.02 6.02 6.02 6.02 6.02 6.02

Vermont Chittenden 9.27 7.16 7.16 7.16 7.16 7.16 7.16

Vermont Chittenden 10.02 7.76 7.76 7.76 7.76 7.76 7.76

Vermont Rutland 11.08 8.15 8.15 8.15 8.15 8.15 8.15

Virginia Arlington 14.27 8.87 8.87 8.87 8.87 8.87 8.87

(continued)
4.A-67

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Virginia Charles 12.37 7.45 7.45 7.45 7.45 7.45 7.45

Virginia Chesterfield 13.44 8.1 8.1 8.1 8.1 8.1 8.1

Virginia Fairfax 13.33 8.34 8.34 8.34 8.34 8.34 8.34

Virginia Fairfax 13.62 8.54 8.54 8.54 8.54 8.54 8.54

Virginia Fairfax 13.88 8.84 8.84 8.84 8.84 8.84 8.84

Virginia Henrico 13.51 8.09 8.09 8.09 8.09 8.09 8.09

Virginia Henrico 12.93 7.67 7.67 7.67 7.67 7.67 7.67

Virginia Loudoun 13.57 8.62 8.62 8.62 8.62 8.62 8.62

Virginia Page 12.79 7.49 7.49 7.49 7.49 7.49 7.49

Virginia Bristol City 13.93 8.31 8.31 8.31 8.31 8.31 8.31

Virginia Hampton City 12.17 7.46 7.46 7.46 7.46 7.46 7.46

Virginia Lynchburg City 12.84 7.5 7.5 7.5 7.5 7.5 7.5

Virginia Norfolk City 12.78 7.92 7.92 7.92 7.92 7.92 7.92

Virginia Roanoke City 14.27 8.62 8.62 8.62 8.62 8.62 8.62

Virginia Salem City 14.69 9.12 9.12 9.12 9.12 9.12 9.12

Virginia Virginia Beach City 12.4 7.55 7.55 7.55 7.55 7.55 7.55

Washington King 9.15 6.95 6.95 6.95 6.95 6.95 6.95

Washington King 11.24 8.35 8.35 8.35 8.35 8.35 8.35

Washington King 8.13 6.19 6.19 6.19 6.19 6.19 6.19

Washington Pierce 10.55 8.11 8.11 8.11 8.11 8.11 7.94

(continued)
4.A-68

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Washington Snohomish 9.91 7.79 7.79 7.79 7.79 7.79 7.79

Washington Spokane 9.97 7.19 7.19 7.19 7.19 7.19 7.19

West Virginia Berkeley 15.93 10.37 10.37 10.37 10.37 10.37 10.37

West Virginia Brooke 16.52 10.01 10.01 10.01 10.01 10.01 10.01

West Virginia Brooke 16.04 9.6 9.6 9.6 9.6 9.6 9.6

West Virginia Cabell 16.3 10.25 10.25 10.25 10.25 10.25 10.25

West Virginia Hancock 15.76 9.6 9.6 9.6 9.6 9.6 9.6

West Virginia Harrison 13.99 8.31 8.31 8.31 8.31 8.31 8.31

West Virginia Kanawha 15.15 8.89 8.89 8.89 8.89 8.89 8.89

West Virginia Kanawha 13.17 7.61 7.61 7.61 7.61 7.61 7.61

West Virginia Kanawha 16.52 9.92 9.92 9.92 9.92 9.92 9.92

West Virginia Marion 15.03 8.93 8.93 8.93 8.93 8.93 8.93

West Virginia Marshall 15.19 8.74 8.74 8.74 8.74 8.74 8.74

West Virginia Monongalia 14.35 8.09 8.09 8.09 8.09 8.09 8.09

West Virginia Ohio 14.58 8.27 8.27 8.27 8.27 8.27 8.27

West Virginia Raleigh 12.9 7.38 7.38 7.38 7.38 7.38 7.38

West Virginia Wood 15.4 9.59 9.59 9.59 9.59 9.59 9.59

Wisconsin Ashland 6.07 4.85 4.85 4.85 4.85 4.85 4.85

Wisconsin Brown 11.39 8.48 8.48 8.48 8.48 8.48 8.48

Wisconsin Dane 12.2 8.59 8.59 8.59 8.59 8.59 8.59

(continued)
4.A-69

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Wisconsin Dodge 11.04 7.95 7.95 7.95 7.95 7.95 7.95

Wisconsin Forest 7.41 5.81 5.81 5.81 5.81 5.81 5.81

Wisconsin Grant 11.79 8.5 8.5 8.5 8.5 8.5 8.5

Wisconsin Kenosha 11.98 8.47 8.47 8.47 8.47 8.47 8.47

Wisconsin Manitowoc 10.2 7.66 7.66 7.66 7.66 7.66 7.66

Wisconsin Milwaukee 13.32 9.28 9.28 9.28 9.28 9.28 9.28

Wisconsin Milwaukee 12.88 8.88 8.88 8.88 8.88 8.88 8.88

Wisconsin Milwaukee 14.08 9.8 9.8 9.8 9.8 9.8 9.8

Wisconsin Milwaukee 13.68 9.54 9.54 9.54 9.54 9.54 9.54

Wisconsin Milwaukee 13.54 9.37 9.37 9.37 9.37 9.37 9.37

Wisconsin Outagamie 10.96 8.11 8.11 8.11 8.11 8.11 8.11

Wisconsin Ozaukee 11.6 8.37 8.37 8.37 8.37 8.37 8.37

Wisconsin St. Croix 10.09 7.8 7.8 7.8 7.8 7.8 7.8

Wisconsin Sauk 10.22 7.28 7.28 7.28 7.28 7.28 7.28

Wisconsin Taylor 8.24 6.31 6.31 6.31 6.31 6.31 6.31

Wisconsin Vilas 6.78 5.35 5.35 5.35 5.35 5.35 5.35

Wisconsin Waukesha 13.91 9.84 9.84 9.84 9.84 9.84 9.84

Wyoming Campbell 6.29 5.93 5.93 5.93 5.93 5.93 5.93

Wyoming Campbell 5.11 4.8 4.8 4.8 4.8 4.8 4.8

Wyoming Campbell 5.26 4.88 4.88 4.88 4.88 4.88 4.88

(continued)
4.A-70

Table 4.A-11. Annual Design Values (DVs) for the 2005 and 2020 Base Case and after Meeting the Current and Proposed 

Alternative Standard Levels: 2020 Baseline (15/35), 2020 12/35 and 2020 11/35 (continued)

State Name County Name

2005 Annual 

DV

2020 Annual 

DV

2020 15/35 

Annual DV

2020 13/35 

Annual DV

2020 12/35 

Annual DV

2020 11/35 

Annual DV

2020 11/30 

Annual DV

Wyoming Converse 3.58 3.29 3.29 3.29 3.29 3.29 3.29

Wyoming Fremont 8.17 7.25 7.25 7.25 7.25 7.25 7.25

Wyoming Laramie 4.48 3.81 3.81 3.81 3.81 3.81 3.81

Wyoming Sheridan 9.7 8.65 8.65 8.65 8.65 8.65 8.65
4.A-71

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) and 

2020 11/30

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

1003 10030010 Alabama Baldwin 26.21 16.25 16.25 16.25

1027 10270001 Alabama Clay 31.88 17.20 17.20 17.20

1033 10331002 Alabama Colbert 30.43 15.63 15.63 15.63

1049 10491003 Alabama De Kalb 32.08 17.07 17.07 17.07

1053 10530002 Alabama Escambia 29.03 18.87 18.87 18.87

1055 10550010 Alabama Etowah 35.18 19.12 19.12 19.12

1069 10690003 Alabama Houston 28.66 18.24 18.24 18.24

1073 10730023 Alabama Jefferson 44.06 27.91 27.91 24.14

1073 10731005 Alabama Jefferson 34.83 21.49 21.49 17.73

1073 10731009 Alabama Jefferson 34.5 17.88 17.88 14.12

1073 10731010 Alabama Jefferson 34.16 18.12 18.12 14.36

1073 10732003 Alabama Jefferson 40.3 28.55 28.55 24.79

1073 10732006 Alabama Jefferson 33.17 18.34 18.34 14.58

1073 10735002 Alabama Jefferson 33.05 17.43 17.43 13.67

1073 10735003 Alabama Jefferson 35.81 19.46 19.46 15.70

1089 10890014 Alabama Madison 33.58 17.12 17.12 17.12

1097 10970002 Alabama Mobile 30.03 18.72 18.72 18.72

1097 10970003 Alabama Mobile 28.58 17.74 17.74 17.74

1101 11010007 Alabama Montgomery 32.05 18.56 18.56 18.56

1103 11030011 Alabama Morgan 31.58 15.05 15.05 15.05

1113 11130001 Alabama Russell 35.55 23.14 23.14 23.14

1117 11170006 Alabama Shelby 32.05 18.39 18.39 18.39

1119 11190002 Alabama Sumter 28.9 16.10 16.10 16.10

1121 11210002 Alabama Talladega 33.46 18.57 18.57 18.57

1125 11250004 Alabama Tuscaloosa 29.8 16.98 16.98 16.98

1127 11270002 Alabama Walker 32.82 17.34 17.34 17.34

4003 40031005 Arizona Cochise 16.62 15.73 15.73 15.69

4005 40051008 Arizona Coconino 17.11 16.21 16.21 16.21

4007 40070008 Arizona Gila 22.12 19.76 19.76 19.76

(continued)
4.A-72

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

4013 40130019 Arizona Maricopa 32.8 24.35 24.35 24.35

4013 40134003 Arizona Maricopa 31.46 24.06 24.06 24.06

4013 40139997 Arizona Maricopa 26.3 19.01 19.01 19.01

4019 40190011 Arizona Pima 12.27 9.64 9.64 9.59

4019 40191028 Arizona Pima 11.34 8.55 8.55 8.50

4021 40210001 Arizona Pinal 17.55 14.56 14.56 14.56

4021 40213002 Arizona Pinal 11.85 10.5 10.53 10.53

4023 40230004 Arizona Santa Cruz 36.08 33.82 33.82 30.49

5001 50010011 Arkansas Arkansas 29.16 18.21 18.21 18.21

5003 50030005 Arkansas Ashley 28.91 21.00 21.00 21.00

5035 50350005 Arkansas Crittenden 35.06 18.60 18.60 18.60

5045 50450002 Arkansas Faulkner 29.87 19.26 19.26 19.26

5051 50510003 Arkansas Garland 29.27 18.67 18.67 18.67

5107 51070001 Arkansas Phillips 29.18 18.10 18.10 18.10

5113 51130002 Arkansas Polk 26.13 15.71 15.71 15.71

5115 51150003 Arkansas Pope 28.32 17.96 17.96 17.96

5119 51190007 Arkansas Pulaski 31.16 19.81 19.81 19.81

5119 51191004 Arkansas Pulaski 31.93 21.88 21.88 21.88

5119 51191005 Arkansas Pulaski 31.91 21.73 21.73 21.73

5139 51390006 Arkansas Union 28.7 19.81 19.81 19.81

5145 51450001 Arkansas White 29.91 19.33 19.33 19.33

6001 60010007 California Alameda 32.58 24.22 24.22 24.22

6001 60011001 California Alameda 29.44 21.44 21.44 21.44

6007 60070002 California Butte 52.55 32.16 32.16 30.46

6009 60090001 California Calaveras 20.55 13.86 13.86 13.86

6011 60111002 California Colusa 26.16 20.47 20.47 20.47

6013 60130002 California Contra Costa 34.7 25.15 25.15 25.15

6019 60190008 California Fresno 60.22 41.03 30.89 24.80

6019 60195001 California Fresno 56.15 38.30 28.29 22.25

(continued)
4.A-73

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

6019 60195025 California Fresno 58.83 40.35 30.32 24.28

6025 60250005 California Imperial 40.21 31.82 31.82 30.40

6025 60250007 California Imperial 21.63 17.11 17.11 15.70

6025 60251003 California Imperial 23.32 18.84 18.84 17.42

6027 60271003 California Inyo 20 17.87 15.53 14.69

6029 60290010 California Kern 64.54 45.93 24.00 21.62

6029 60290014 California Kern 61.65 44.08 22.21 19.86

6029 60290016 California Kern 60.38 44.51 22.60 20.23

6031 60310004 California Kings 58.06 42.42 35.49 28.94

6033 60333001 California Lake 12.94 11.83 11.83 11.83

6037 60370002 California Los Angeles 49.85 35.54 25.18 24.24

6037 60371002 California Los Angeles 49.7 37.38 26.69 25.66

6037 60371103 California Los Angeles 50.97 38.39 27.52 26.43

6037 60371201 California Los Angeles 42.4 31.36 21.57 20.77

6037 60371301 California Los Angeles 48.71 39.72 29.16 28.17

6037 60371602 California Los Angeles 50.2 39.16 28.51 27.50

6037 60372005 California Los Angeles 42.2 28.18 17.75 16.78

6037 60374002 California Los Angeles 41.42 34.83 24.66 23.78

6037 60374004 California Los Angeles 39.38 33.49 23.49 22.66

6037 60379033 California Los Angeles 17.11 13.71 5.166 4.73

6045 60450006 California Mendocino 15.3 9.415 9.41 9.41

6047 60472510 California Merced 46.15 31.30 28.37 27.38

6053 60531003 California Monterey 14.35 10.98 8.783 7.98

6057 60570005 California Nevada 13.93 11.13 11.13 11.13

6057 60571001 California Nevada 16.55 12.65 12.65 12.65

6059 60590007 California Orange 43.76 34.02 31.01 28.31

6059 60592022 California Orange 33.85 29.68 27.43 24.94

6061 60610006 California Placer 29.88 20.31 20.31 20.31

6063 60631006 California Plumas 29.33 22.60 22.60 22.60

(continued)
4.A-74

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

6063 60631009 California Plumas 32.44 24.05 24.05 24.05

6065 60651003 California Riverside 48.88 39.75 28.75 21.74

6065 60652002 California Riverside 24.22 18.47 8.969 2.31

6065 60658001 California Riverside 59.13 46.57 35.49 28.45

6067 60670006 California Sacramento 49.22 32.92 32.92 27.12

6067 60670010 California Sacramento 41.55 30.10 30.10 24.30

6067 60674001 California Sacramento 39.55 28.08 28.08 22.27

6071 60710025 California San Bernardino 51.9 41.28 34.02 26.86

6071 60710306 California San Bernardino 23.11 16.64 10.43 3.53

6071 60712002 California San Bernardino 52.85 39.80 32.26 25.03

6071 60718001 California San Bernardino 37.56 33.65 27.93 21.16

6071 60719004 California San Bernardino 55.5 41.53 34.44 27.32

6073 60730001 California San Diego 30.58 21.96 21.96 21.96

6073 60730003 California San Diego 35.55 25.35 25.35 25.35

6073 60730006 California San Diego 24.11 17.52 17.52 17.52

6073 60731002 California San Diego 33.28 23.94 23.94 23.94

6073 60731010 California San Diego 33.17 23.49 23.49 23.49

6075 60750005 California San Francisco 30.91 22.10 22.10 22.10

6077 60771002 California San Joaquin 41.88 29.94 26.89 25.87

6079 60792006 California San Luis Obispo 15.03 11.58 9.280 8.46

6079 60798001 California San Luis Obispo 22.58 17.17 14.54 13.63

6081 60811001 California San Mateo 29.41 21.72 21.72 21.72

6083 60830011 California Santa Barbara 24.07 16.45 16.45 16.45

6085 60850005 California Santa Clara 38.61 27.62 24.48 23.36

6085 60852003 California Santa Clara 35.9 25.34 22.26 21.16

6089 60890004 California Shasta 20.42 12.79 12.79 12.79

6095 60950004 California Solano 34.76 25.26 25.26 25.26

6097 60970003 California Sonoma 29.1 18.67 18.67 18.67

6099 60990005 California Stanislaus 51.48 37.06 31.79 28.73

(continued)
4.A-75

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

6101 61010003 California Sutter 38.55 25.21 25.21 25.21

6107 61072002 California Tulare 56.63 40.12 31.82 27.84

6111 61110007 California Ventura 26.43 19.13 16.91 16.28

6111 61110009 California Ventura 21.53 16.18 13.96 13.32

6111 61112002 California Ventura 30.3 22.58 20.18 19.50

6111 61113001 California Ventura 25.4 17.38 15.67 15.19

6113 61131003 California Yolo 30.38 22.66 22.66 22.66

8001 80010006 Colorado Adams 25.35 17.94 17.94 17.94

8005 80050005 Colorado Arapahoe 21.27 15.47 15.47 15.47

8013 80130003 Colorado Boulder 21.12 16.19 16.19 16.19

8013 80130012 Colorado Boulder 18.7 14.40 14.40 14.40

8029 80290004 Colorado Delta 20.76 14.09 14.09 14.09

8031 80310002 Colorado Denver 26.44 19.47 19.47 19.47

8031 80310023 Colorado Denver 26.36 19.57 19.57 19.57

8039 80390001 Colorado Elbert 13.18 10.20 10.20 10.20

8041 80410008 Colorado El Paso 16.41 10.29 10.29 10.29

8041 80410011 Colorado El Paso 16.51 10.72 10.72 10.72

8069 80690009 Colorado Larimer 18.3 13.96 13.96 13.96

8077 80770017 Colorado Mesa 23.51 17.04 17.04 17.04

8101 81010012 Colorado Pueblo 15.42 10.93 10.93 10.93

8113 81130004 Colorado San Miguel 10.11 9.29 9.29 9.29

8123 81230006 Colorado Weld 22.9 17.47 17.47 17.47

8123 81230008 Colorado Weld 18.38 14.08 14.08 14.08

9001 90010010 Connecticut Fairfield 36.27 22.27 22.27 22.27

9001 90011123 Connecticut Fairfield 32.27 20.46 20.46 20.46

9001 90013005 Connecticut Fairfield 34.91 19.74 19.74 19.74

9001 90019003 Connecticut Fairfield 33.66 18.34 18.34 18.34

9003 90031003 Connecticut Hartford 31.83 17.84 17.84 17.84

9005 90050005 Connecticut Litchfield 27.16 13.00 13.00 13.00

(continued)
4.A-76

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

9009 90090026 Connecticut New Haven 35.65 20.29 20.29 20.29

9009 90090027 Connecticut New Haven 35.58 20.10 20.10 20.10

9009 90091123 Connecticut New Haven 38.37 21.78 21.78 21.78

9009 90092008 Connecticut New Haven 33.68 19.01 19.01 19.01

9009 90092123 Connecticut New Haven 34.45 20.00 20.00 20.00

9011 90113002 Connecticut New London 32.03 16.66 16.66 16.66

10001 100010002 Delaware Kent 32.14 18.35 18.35 18.35

10001 100010003 Delaware Kent 31.5 17.57 17.57 17.57

10003 100031003 Delaware New Castle 34.36 21.64 21.64 21.64

10003 100031007 Delaware New Castle 32.65 17.11 17.11 17.11

10003 100031012 Delaware New Castle 33.5 22.01 22.01 22.01

10003 100032004 Delaware New Castle 36.66 22.47 22.47 22.47

10005 100051002 Delaware Sussex 33.78 19.48 19.48 19.48

11001 110010041 D.C. Washington 36.35 20.93 20.93 20.93

11001 110010042 D.C. Washington 34.95 20.29 20.29 20.29

11001 110010043 D.C. Washington 34.16 20.14 20.14 20.14

12001 120010023 Florida Alachua 21.35 12.18 12.18 12.18

12001 120010024 Florida Alachua 20.98 13.56 13.56 13.56

12005 120051004 Florida Bay 28.08 18.31 18.31 18.31

12009 120090007 Florida Brevard 20.73 12.88 12.88 12.88

12011 120111002 Florida Broward 18.34 13.22 13.22 13.22

12011 120112004 Florida Broward 18.63 13.16 13.16 13.16

12011 120113002 Florida Broward 15.96 10.92 10.92 10.92

12017 120170005 Florida Citrus 21.22 11.83 11.83 11.83

12031 120310098 Florida Duval 23.72 16.13 16.13 16.13

12031 120310099 Florida Duval 24.35 17.77 17.77 17.77

12033 120330004 Florida Escambia 28.8 20.86 20.86 20.86

12057 120570030 Florida Hillsborough 23.44 15.31 15.31 15.31

12057 120573002 Florida Hillsborough 22.25 13.16 13.16 13.16

(continued)
4.A-77

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

12071 120710005 Florida Lee 17.7 12.27 12.27 12.27

12073 120730012 Florida Leon 27.03 18.52 18.52 18.52

12081 120814012 Florida Manatee 19.57 11.54 11.54 11.54

12083 120830003 Florida Marion 22.56 13.49 13.49 13.49

12086 120861016 Florida Miami-Dade 19.13 11.54 11.54 11.54

12086 120866001 Florida Miami-Dade 18.6 12.83 12.83 12.83

12095 120952002 Florida Orange 21.83 12.99 12.99 12.99

12099 120990009 Florida Palm Beach 17.73 13.63 13.63 13.63

12099 120992005 Florida Palm Beach 18.22 12.75 12.75 12.75

12103 121030018 Florida Pinellas 21.73 14.58 14.58 14.58

12103 121031009 Florida Pinellas 20.8 13.91 13.91 13.91

12105 121056006 Florida Polk 19.3 12.88 12.88 12.88

12111 121111002 Florida St Lucie 18.18 11.46 11.46 11.46

12115 121150013 Florida Sarasota 19.22 12.19 12.19 12.19

12117 121171002 Florida Seminole 22.08 12.45 12.45 12.45

12127 121275002 Florida Volusia 22 12.81 12.81 12.81

13021 130210007 Georgia Bibb 33.56 21.70 21.70 21.27

13021 130210012 Georgia Bibb 30.74 17.76 17.76 17.33

13051 130510017 Georgia Chatham 28.45 18.78 18.78 18.78

13051 130510091 Georgia Chatham 27.9 18.29 18.29 18.29

13063 130630091 Georgia Clayton 35.88 20.95 20.95 20.95

13067 130670003 Georgia Cobb 35.04 19.81 19.81 19.81

13067 130670004 Georgia Cobb 34.12 19.35 19.35 19.35

13089 130890002 Georgia De Kalb 33.44 18.19 18.19 18.19

13089 130892001 Georgia De Kalb 33.92 19.54 19.54 19.54

13095 130950007 Georgia Dougherty 34.15 23.51 23.51 23.51

13115 131150005 Georgia Floyd 35.12 21.22 21.22 21.22

13121 131210032 Georgia Fulton 34.13 19.56 19.56 19.56

13121 131210039 Georgia Fulton 37.66 22.76 22.76 22.45

(continued)
4.A-78

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

13127 131270006 Georgia Glynn 26.13 18.04 18.04 18.04

13135 131350002 Georgia Gwinnett 32.81 18.28 18.28 18.28

13139 131390003 Georgia Hall 30.11 18.95 18.95 18.95

13153 131530001 Georgia Houston 29.63 17.62 17.62 17.59

13185 131850003 Georgia Lowndes 25.68 16.90 16.90 16.90

13215 132150001 Georgia Muscogee 31.38 21.83 21.83 21.83

13215 132150008 Georgia Muscogee 34.58 22.33 22.33 22.33

13215 132150011 Georgia Muscogee 30.25 20.09 20.09 20.09

13223 132230003 Georgia Paulding 33.02 18.66 18.66 18.66

13245 132450005 Georgia Richmond 32.7 23.41 23.41 23.41

13245 132450091 Georgia Richmond 31.97 21.68 21.68 21.68

13295 132950002 Georgia Walker 30.98 18.36 18.36 18.36

13303 133030001 Georgia Washington 30.83 18.99 18.99 18.99

13319 133190001 Georgia Wilkinson 33.16 20.66 20.66 20.66

16001 160010011 Idaho Ada 28.36 25.01 25.01 25.01

16005 160050015 Idaho Bannock 27.08 24.18 24.18 24.18

16009 160090010 Idaho Benewah 32.94 28.46 28.46 28.38

16027 160270004 Idaho Canyon 31.8 26.29 26.29 26.29

16041 160410001 Idaho Franklin 36.76 30.49 30.49 30.43

16049 160490003 Idaho Idaho 28.43 26.37 26.37 26.18

16059 160590004 Idaho Lemhi 36.53 31.32 31.32 30.48

16077 160770011 Idaho Power 33.36 29.75 29.75 29.75

16079 160790017 Idaho Shoshone 38.16 31.96 31.96 30.48

17001 170010006 Illinois Adams 31.41 18.25 18.25 18.25

17019 170190004 Illinois Champaign 31.32 18.99 18.99 18.99

17019 170191001 Illinois Champaign 30.04 19.02 19.02 19.02

17031 170310022 Illinois Cook 36.61 28.61 28.61 28.25

17031 170310050 Illinois Cook 36.11 25.08 25.08 24.72

17031 170310052 Illinois Cook 40.26 26.51 26.51 26.15

(continued)
4.A-79

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

17031 170310057 Illinois Cook 37.37 25.25 25.25 24.89

17031 170310076 Illinois Cook 38.05 25.52 25.52 25.16

17031 170311016 Illinois Cook 43.03 28.93 28.93 28.56

17031 170312001 Illinois Cook 37.7 26.75 26.75 26.38

17031 170313103 Illinois Cook 39.65 27.06 27.06 26.70

17031 170313301 Illinois Cook 40.22 26.35 26.35 25.98

17031 170314007 Illinois Cook 34.31 22.60 22.60 22.23

17031 170314201 Illinois Cook 32 21.74 21.74 21.38

17031 170316005 Illinois Cook 39.17 29.02 29.02 28.65

17043 170434002 Illinois Du Page 34.64 25.32 25.32 25.32

17065 170650002 Illinois Hamilton 31.6 16.98 16.98 16.98

17083 170831001 Illinois Jersey 32.18 19.67 19.67 18.93

17089 170890003 Illinois Kane 33.85 23.48 23.48 23.48

17089 170890007 Illinois Kane 34.83 25.12 25.12 25.12

17097 170971007 Illinois Lake 33.08 21.19 21.19 21.19

17099 170990007 Illinois La Salle 28.92 19.62 19.62 19.62

17111 171110001 Illinois McHenry 31.58 20.88 20.88 20.88

17113 171132003 Illinois McLean 33.43 20.92 20.92 20.92

17115 171150013 Illinois Macon 33.25 18.70 18.70 18.70

17119 171190023 Illinois Madison 37.31 24.71 24.71 22.72

17119 171191007 Illinois Madison 39.16 25.29 25.29 23.30

17119 171192009 Illinois Madison 34.97 22.05 22.05 20.06

17119 171193007 Illinois Madison 34.03 19.78 19.78 17.80

17143 171430037 Illinois Peoria 32.76 21.05 21.05 21.05

17157 171570001 Illinois Randolph 28.96 20.19 20.19 20.19

17161 171613002 Illinois Rock Island 30.9 22.57 22.57 22.57

17163 171630010 Illinois St Clair 33.7 22.13 22.13 21.35

17163 171634001 Illinois St Clair 31.91 22.79 22.79 22.07

17167 171670012 Illinois Sangamon 33.41 21.67 21.67 21.67

(continued)
4.A-80

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

17197 171971002 Illinois Will 36.45 24.37 24.37 24.37

17197 171971011 Illinois Will 30.71 17.71 17.71 17.71

17201 172010013 Illinois Winnebago 34.73 24.49 24.49 24.49

18003 180030004 Indiana Allen 33.1 23.14 23.14 23.14

18003 180030014 Indiana Allen 30.51 20.81 20.81 20.81

18019 180190006 Indiana Clark 37.57 20.97 20.97 20.97

18035 180350006 Indiana Delaware 32.07 20.32 20.32 20.32

18037 180372001 Indiana Dubois 35.36 21.93 21.93 21.93

18039 180390003 Indiana Elkhart 34.43 25.09 25.09 25.09

18043 180431004 Indiana Floyd 33.26 17.44 17.44 17.44

18065 180650003 Indiana Henry 31.86 19.30 19.30 19.30

18067 180670003 Indiana Howard 32.21 20.20 20.20 20.20

18083 180830004 Indiana Knox 35.92 21.44 21.44 21.44

18089 180890006 Indiana Lake 34.97 26.23 26.23 26.23

18089 180890022 Indiana Lake 38.98 29.59 29.59 29.59

18089 180890026 Indiana Lake 38.42 27.13 27.13 27.13

18089 180890027 Indiana Lake 32.63 23.66 23.66 23.66

18089 180890031 Indiana Lake 34 22.52 22.52 22.52

18089 180891003 Indiana Lake 32.71 24.90 24.90 24.90

18089 180892004 Indiana Lake 32.91 26.34 26.34 26.34

18089 180892010 Indiana Lake 34.23 25.77 25.77 25.77

18091 180910011 Indiana La Porte 33 21.47 21.47 21.47

18091 180910012 Indiana La Porte 30.61 21.63 21.63 21.63

18095 180950009 Indiana Madison 32.82 20.04 20.04 20.04

18097 180970042 Indiana Marion 34.23 20.92 20.92 20.92

18097 180970043 Indiana Marion 38.47 23.70 23.70 23.70

18097 180970066 Indiana Marion 38.31 24.20 24.20 24.20

18097 180970078 Indiana Marion 36.64 22.66 22.66 22.66

18097 180970079 Indiana Marion 35.61 21.22 21.22 21.22

(continued)
4.A-81

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

18097 180970081 Indiana Marion 38.2 23.59 23.59 23.59

18097 180970083 Indiana Marion 36.63 23.85 23.85 23.85

18127 181270020 Indiana Porter 32.96 22.00 22.00 22.00

18127 181270024 Indiana Porter 31.87 23.05 23.05 23.05

18141 181410014 Indiana St Joseph 32.45 23.43 23.43 23.43

18141 181411008 Indiana St Joseph 33.16 24.73 24.73 24.73

18141 181412004 Indiana St Joseph 30.04 23.49 23.49 23.49

18147 181470009 Indiana Spencer 32.32 15.43 15.43 15.43

18157 181570008 Indiana Tippecanoe 35.68 20.81 20.81 20.81

18163 181630006 Indiana Vanderburgh 34.8 22.81 22.81 22.81

18163 181630012 Indiana Vanderburgh 33.27 22.48 22.48 22.48

18163 181630016 Indiana Vanderburgh 32.66 22.91 22.91 22.91

18167 181670018 Indiana Vigo 34.6 20.64 20.64 20.64

18167 181670023 Indiana Vigo 34.88 19.44 19.44 19.44

19013 190130008 Iowa Black Hawk 30.78 21.69 21.69 21.69

19045 190450021 Iowa Clinton 33.95 23.86 23.86 23.86

19103 191032001 Iowa Johnson 34.67 24.38 24.38 24.38

19113 191130037 Iowa Linn 30.6 20.62 20.62 20.62

19137 191370002 Iowa Montgomery 27.5 17.47 17.47 17.47

19139 191390015 Iowa Muscatine 36.03 27.11 27.11 27.11

19147 191471002 Iowa Palo Alto 25.73 18.02 18.02 18.02

19153 191530030 Iowa Polk 28.41 20.25 20.25 20.25

19153 191532510 Iowa Polk 27.26 18.56 18.56 18.56

19153 191532520 Iowa Polk 31.46 22.22 22.22 22.22

19155 191550009 Iowa Pottawattamie 28.6 21.11 21.11 21.11

19163 191630015 Iowa Scott 31.01 21.33 21.33 21.33

19163 191630018 Iowa Scott 32.34 23.19 23.19 23.19

19163 191630019 Iowa Scott 37.1 25.09 25.09 25.09

19177 191770006 Iowa Van Buren 28.36 19.89 19.89 19.89

(continued)
4.A-82

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

19193 191930017 Iowa Woodbury 26.4 19.58 19.58 19.58

19197 191970004 Iowa Wright 28.65 19.15 19.15 19.15

20091 200910007 Kansas Johnson 25.37 17.45 17.45 17.45

20091 200910009 Kansas Johnson 29.3 22.43 22.43 22.43

20091 200910010 Kansas Johnson 23.55 15.14 15.14 15.14

20107 201070002 Kansas Linn 25.38 17.91 17.91 17.91

20173 201730008 Kansas Sedgwick 23.7 16.04 16.04 16.04

20173 201730009 Kansas Sedgwick 25.01 17.07 17.07 17.07

20173 201730010 Kansas Sedgwick 25.37 18.21 18.21 18.21

20177 201770010 Kansas Shawnee 29.16 21.81 21.81 21.81

20191 201910002 Kansas Sumner 22.84 16.11 16.11 16.11

20209 202090021 Kansas Wyandotte 29.58 21.07 21.07 21.07

20209 202090022 Kansas Wyandotte 26.6 18.33 18.33 18.33

21013 210130002 Kentucky Bell 29.9 16.93 16.93 16.93

21019 210190017 Kentucky Boyd 33.15 16.09 16.09 16.09

21029 210290006 Kentucky Bullitt 34.63 17.50 17.50 17.50

21037 210370003 Kentucky Campbell 31.2 16.22 16.22 16.22

21043 210430500 Kentucky Carter 29.91 13.49 13.49 13.49

21047 210470006 Kentucky Christian 33.6 16.00 16.00 16.00

21059 210590005 Kentucky Daviess 33.86 16.90 16.90 16.90

21067 210670012 Kentucky Fayette 31.97 16.44 16.44 16.44

21067 210670014 Kentucky Fayette 32.23 17.70 17.70 17.70

21073 210730006 Kentucky Franklin 32.17 17.09 17.09 17.09

21093 210930006 Kentucky Hardin 32.81 15.86 15.86 15.86

21101 211010014 Kentucky Henderson 31.85 17.66 17.66 17.66

21111 211110043 Kentucky Jefferson 35.48 18.39 18.39 18.39

21111 211110044 Kentucky Jefferson 36.16 19.20 19.20 19.20

21111 211110048 Kentucky Jefferson 36.44 20.47 20.47 20.47

21111 211110051 Kentucky Jefferson 32.4 15.08 15.08 15.08

(continued)
4.A-83

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

21117 211170007 Kentucky Kenton 34.74 19.01 19.01 19.01

21125 211250004 Kentucky Laurel 25.16 13.86 13.86 13.86

21145 211451004 Kentucky McCracken 33.62 17.07 17.07 17.07

21151 211510003 Kentucky Madison 30.11 15.14 15.14 15.14

21193 211930003 Kentucky Perry 28.54 13.52 13.52 13.52

21195 211950002 Kentucky Pike 30.52 15.35 15.35 15.35

21227 212270007 Kentucky Warren 33.14 16.04 16.04 16.04

22017 220171002 Louisiana Caddo 27.56 18.95 18.95 18.95

22019 220190009 Louisiana Calcasieu 24.28 16.84 16.84 16.84

22019 220190010 Louisiana Calcasieu 26.38 17.48 17.48 17.48

22029 220290003 Louisiana Concordia 26.16 16.01 16.01 16.01

22033 220330009 Louisiana East Baton Rouge 29.36 21.12 21.12 21.12

22033 220331001 Louisiana East Baton Rouge 25.47 17.97 17.97 17.97

22047 220470005 Louisiana Iberville 28.62 21.52 21.52 21.52

22047 220470009 Louisiana Iberville 26.14 16.97 16.97 16.97

22051 220511001 Louisiana Jefferson 27.06 16.37 16.37 16.37

22055 220550006 Louisiana Lafayette 24.28 15.98 15.98 15.98

22073 220730004 Louisiana Ouachita 28.91 19.57 19.57 19.57

22079 220790002 Louisiana Rapides 30.26 18.76 18.76 18.76

22105 221050001 Louisiana Tangipahoa 29.61 18.23 18.23 18.23

22109 221090001 Louisiana Terrebonne 26.25 16.19 16.19 16.19

22121 221210001 Louisiana West Baton Rouge 29.08 20.94 20.94 20.94

23001 230010011 Maine Androscoggin 26.56 16.78 16.78 16.78

23003 230030013 Maine Aroostook 24.23 20.18 20.18 20.18

23003 230031011 Maine Aroostook 22.91 17.01 17.01 17.01

23005 230050015 Maine Cumberland 27.74 16.79 16.79 16.79

23005 230050027 Maine Cumberland 29.2 17.48 17.48 17.48

23009 230090103 Maine Hancock 19.43 11.79 11.79 11.79

23011 230110016 Maine Kennebec 26.21 15.86 15.86 15.86

(continued)
4.A-84

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

23017 230172011 Maine Oxford 28.36 18.96 18.96 18.96

23019 230190002 Maine Penobscot 22.03 14.30 14.30 14.30

24003 240030014 Maryland Anne Arundel 33.23 17.56 17.56 17.56

24003 240031003 Maryland Anne Arundel 35.55 22.09 22.09 22.09

24003 240032002 Maryland Anne Arundel 36.16 23.69 23.69 23.69

24005 240051007 Maryland Baltimore 33.33 20.06 20.06 20.06

24005 240053001 Maryland Baltimore 35.84 21.66 21.66 21.66

24015 240150003 Maryland Cecil 30.82 19.07 19.07 19.07

24025 240251001 Maryland Harford 31.21 17.19 17.19 17.19

24031 240313001 Maryland Montgomery 30.93 17.19 17.19 17.19

24033 240330030 Maryland Prince Georges 31.73 17.45 17.45 17.45

24033 240338003 Maryland Prince Georges 33.46 18.03 18.03 18.03

24043 240430009 Maryland Washington 33.43 20.15 20.15 20.15

24510 245100006 Maryland Baltimore City 33.38 21.16 21.16 21.16

24510 245100007 Maryland Baltimore City 34.74 22.38 22.38 22.38

24510 245100008 Maryland Baltimore City 37.21 24.33 24.33 24.33

24510 245100035 Maryland Baltimore City 37.75 24.85 24.85 24.85

24510 245100040 Maryland Baltimore City 39.01 25.23 25.23 25.23

24510 245100049 Maryland Baltimore City 38.16 26.21 26.21 26.21

25003 250035001 Massachusetts Berkshire 31.06 19.54 19.54 19.54

25005 250051004 Massachusetts Bristol 25.07 15.30 15.30 15.30

25009 250092006 Massachusetts Essex 28.72 18.00 18.00 18.00

25009 250095005 Massachusetts Essex 26.85 14.98 14.98 14.98

25009 250096001 Massachusetts Essex 27.8 17.48 17.48 17.48

25013 250130008 Massachusetts Hampden 27.26 17.08 17.08 17.08

25013 250130016 Massachusetts Hampden 32.3 20.35 20.35 20.35

25013 250132009 Massachusetts Hampden 33.13 20.80 20.80 20.80

25023 250230004 Massachusetts Plymouth 28.48 16.46 16.46 16.46

25025 250250002 Massachusetts Suffolk 29.45 19.75 19.75 19.75

(continued)
4.A-85

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

25025 250250027 Massachusetts Suffolk 29.23 19.20 19.20 19.20

25025 250250042 Massachusetts Suffolk 28.6 19.01 19.01 19.01

25025 250250043 Massachusetts Suffolk 32.17 20.80 20.80 20.80

25027 250270016 Massachusetts Worcester 30.01 17.73 17.73 17.73

25027 250270023 Massachusetts Worcester 30.66 18.47 18.47 18.47

26005 260050003 Michigan Allegan 33.82 23.99 23.99 23.99

26017 260170014 Michigan Bay 31.68 21.73 21.73 21.73

26021 260210014 Michigan Berrien 31.32 21.21 21.21 21.21

26049 260490021 Michigan Genesee 30.46 21.92 21.92 21.92

26065 260650012 Michigan Ingham 31.96 22.40 22.40 22.40

26077 260770008 Michigan Kalamazoo 31.17 21.05 21.05 21.05

26081 260810020 Michigan Kent 36.53 23.50 23.50 23.50

26099 260990009 Michigan Macomb 35.32 27.12 27.12 27.12

26113 261130001 Michigan Missaukee 24.83 15.51 15.51 15.51

26115 261150005 Michigan Monroe 38.88 23.36 23.36 23.36

26121 261210040 Michigan Muskegon 34.71 23.72 23.72 23.72

26125 261250001 Michigan Oakland 39.94 24.16 24.16 24.16

26139 261390005 Michigan Ottawa 34.24 25.06 25.06 25.06

26145 261450018 Michigan Saginaw 30.66 20.77 20.77 20.77

26147 261470005 Michigan St Clair 39.61 28.92 28.92 28.92

26161 261610005 Michigan Washtenaw 33.6 22.74 22.74 22.74

26161 261610008 Michigan Washtenaw 39.46 23.39 23.39 23.39

26163 261630001 Michigan Wayne 37.83 25.52 25.52 21.34

26163 261630015 Michigan Wayne 40.12 27.89 27.89 23.71

26163 261630016 Michigan Wayne 42.92 30.23 30.23 26.06

26163 261630019 Michigan Wayne 40.92 30.69 30.69 26.51

26163 261630025 Michigan Wayne 35.18 22.91 22.91 18.73

26163 261630033 Michigan Wayne 43.88 31.37 31.37 27.19

26163 261630036 Michigan Wayne 37.16 25.77 25.77 21.59

(continued)
4.A-86

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

26163 261630039 Michigan Wayne 37.03 26.93 26.93 22.75

27021 270210001 Minnesota Cass 18.02 13.84 13.84 13.84

27037 270370470 Minnesota Dakota 25.42 18.28 18.28 18.28

27053 270530050 Minnesota Hennepin 27.25 19.26 19.26 19.26

27053 270530961 Minnesota Hennepin 25.52 17.99 17.99 17.99

27053 270530963 Minnesota Hennepin 26.07 18.83 18.83 18.83

27053 270530965 Minnesota Hennepin 24.71 18.35 18.35 18.35

27053 270531007 Minnesota Hennepin 25.44 17.85 17.85 17.85

27053 270532006 Minnesota Hennepin 26.76 18.04 18.04 18.04

27095 270953051 Minnesota Mille Lacs 22.03 16.93 16.93 16.93

27123 271230866 Minnesota Ramsey 28.04 20.57 20.57 20.57

27123 271230868 Minnesota Ramsey 28.38 20.59 20.59 20.59

27123 271230871 Minnesota Ramsey 26.36 19.72 19.72 19.72

27137 271377001 Minnesota St Louis 20.31 15.63 15.63 15.63

27137 271377550 Minnesota St Louis 19.51 14.20 14.20 14.20

27137 271377551 Minnesota St Louis 23.53 16.56 16.56 16.56

27139 271390505 Minnesota Scott 24.98 17.93 17.93 17.93

28001 280010004 Mississippi Adams 27.48 16.79 16.79 16.79

28011 280110001 Mississippi Bolivar 28.98 19.20 19.20 19.20

28033 280330002 Mississippi De Soto 30.82 15.85 15.85 15.85

28035 280350004 Mississippi Forrest 30.48 20.78 20.78 20.78

28047 280470008 Mississippi Harrison 29 18.33 18.33 18.33

28049 280490010 Mississippi Hinds 28.83 17.03 17.03 17.03

28059 280590006 Mississippi Jackson 26.96 16.48 16.48 16.48

28067 280670002 Mississippi Jones 31.21 20.85 20.85 20.85

28081 280810005 Mississippi Lee 32.18 16.69 16.69 16.69

28087 280870001 Mississippi Lowndes 32.44 17.28 17.28 17.28

28149 281490004 Mississippi Warren 30.26 19.28 19.28 19.28

29019 290190004 Missouri Boone 30.23 19.03 19.03 19.03

(continued)
4.A-87

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

29021 290210005 Missouri Buchanan 30.1 21.61 21.61 21.61

29037 290370003 Missouri Cass 25.61 16.89 16.89 16.89

29039 290390001 Missouri Cedar 28.7 18.77 18.77 18.77

29047 290470005 Missouri Clay 28.04 20.00 20.00 20.00

29077 290770032 Missouri Greene 28.27 18.75 18.75 18.75

29095 290950034 Missouri Jackson 27.88 20.33 20.33 20.33

29099 290990012 Missouri Jefferson 33.43 21.12 21.12 21.12

29137 291370001 Missouri Monroe 27.83 17.98 17.98 17.98

29183 291831002 Missouri St Charles 33.16 20.01 20.01 20.01

29186 291860006 Missouri Ste Genevieve 31.44 18.83 18.83 18.83

29189 291890004 Missouri St Louis 32.03 20.46 20.46 20.46

29189 291892003 Missouri St Louis 33.21 23.50 23.50 23.50

29510 295100007 Missouri St Louis City 33.16 20.79 20.79 20.79

29510 295100085 Missouri St Louis City 33.24 21.03 21.03 21.03

29510 295100086 Missouri St Louis City 32.5 22.13 22.13 22.13

29510 295100087 Missouri St Louis City 34.35 22.07 22.07 22.07

30013 300131026 Montana Cascade 20.15 17.08 17.08 17.08

30029 300290009 Montana Flathead 27.14 22.76 22.56 22.05

30029 300290047 Montana Flathead 27.17 24.28 24.11 23.65

30031 300310008 Montana Gallatin 29.55 26.24 26.24 26.24

30031 300310013 Montana Gallatin 12.2 11.3 11.39 11.39

30047 300470013 Montana Lake 27.03 23.75 20.89 15.95

30047 300470028 Montana Lake 43.66 38.36 35.49 30.49

30049 300490018 Montana Lewis And Clark 33.53 28.27 28.27 28.27

30053 300530018 Montana Lincoln 42.71 35.36 35.12 29.50

30063 300630031 Montana Missoula 44.64 37.47 34.48 30.48

30081 300810007 Montana Ravalli 45.11 37.30 35.48 30.48

30087 300870307 Montana Rosebud 19.73 18.34 18.34 18.34

30089 300890007 Montana Sanders 20.42 18.25 18.10 17.71

(continued)
4.A-88

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

30093 300930005 Montana Silver Bow 35 28.15 28.15 28.15

30111 301111065 Montana Yellowstone 19.38 15.76 15.76 15.76

31025 310250002 Nebraska Cass 28.3 20.73 20.73 20.73

31055 310550019 Nebraska Douglas 25.7 19.25 19.25 19.25

31055 310550052 Nebraska Douglas 25.76 18.99 18.99 18.99

31079 310790004 Nebraska Hall 19.16 14.31 14.31 14.31

31109 311090022 Nebraska Lancaster 24.77 17.87 17.87 17.87

31157 311570003 Nebraska Scotts Bluff 16.66 13.90 13.90 13.90

31177 311770002 Nebraska Washington 24.01 17.68 17.68 17.68

32003 320030022 Nevada Clark 9.13 8.18 8.18 8.18

32003 320030298 Nevada Clark 12.43 10.10 10.10 10.10

32003 320030561 Nevada Clark 25.26 19.31 19.31 19.31

32003 320031019 Nevada Clark 8.6 7.53 7.53 7.53

32003 320032002 Nevada Clark 20.93 16.35 16.35 16.35

32031 320310016 Nevada Washoe 30.78 20.85 20.85 20.85

33001 330012004 New Hampshire Belknap 20.55 11.31 11.31 11.31

33005 330050007 New Hampshire Cheshire 30.23 18.74 18.74 18.74

33007 330070014 New Hampshire Coos 26.5 17.08 17.08 17.08

33009 330090010 New Hampshire Grafton 23 14.67 14.67 14.67

33011 330110020 New Hampshire Hillsborough 28.66 18.87 18.87 18.87

33011 330111015 New Hampshire Hillsborough 27.33 19.03 19.03 19.03

33011 330115001 New Hampshire Hillsborough 25.9 12.93 12.93 12.93

33013 330131006 New Hampshire Merrimack 25.65 15.12 15.12 15.12

33015 330150014 New Hampshire Rockingham 26.35 15.67 15.67 15.67

33019 330190003 New Hampshire Sullivan 28.92 16.49 16.49 16.49

34003 340030003 New Jersey Bergen 37.03 22.46 22.46 22.46

34007 340070003 New Jersey Camden 36.5 20.93 20.93 20.93

34007 340071007 New Jersey Camden 37.37 20.89 20.89 20.89

34013 340130015 New Jersey Essex 38.38 22.59 22.59 22.59

(continued)
4.A-89

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

34017 340171003 New Jersey Hudson 39.08 25.73 25.73 25.73

34017 340172002 New Jersey Hudson 41.43 29.62 29.62 29.62

34021 340210008 New Jersey Mercer 34.75 18.67 18.67 18.67

34023 340230006 New Jersey Middlesex 34.82 19.67 19.67 19.67

34027 340270004 New Jersey Morris 32.32 18.32 18.32 18.32

34027 340273001 New Jersey Morris 31.5 16.03 16.03 16.03

34029 340292002 New Jersey Ocean 31.56 16.14 16.14 16.14

34031 340310005 New Jersey Passaic 36.3 21.13 21.13 21.13

34039 340390004 New Jersey Union 40.47 24.64 24.64 24.64

34039 340390006 New Jersey Union 37.35 21.11 21.11 21.11

34039 340392003 New Jersey Union 36.82 21.32 21.32 21.32

34041 340410006 New Jersey Warren 34.06 20.46 20.46 20.46

35001 350010023 New Mexico Bernalillo 18.6 14.61 14.61 14.61

35001 350010024 New Mexico Bernalillo 16.43 13.12 13.12 13.12

35005 350050005 New Mexico Chaves 15.68 12.43 12.43 12.43

35013 350130017 New Mexico Dona Ana 32.95 26.90 26.90 26.90

35013 350130025 New Mexico Dona Ana 13.8 11.66 11.66 11.66

35017 350171002 New Mexico Grant 13 12.21 12.21 12.21

35043 350431003 New Mexico Sandoval 10.3 8.01 8.01 8.01

35043 350439011 New Mexico Sandoval 15.68 13.73 13.73 13.73

35045 350450006 New Mexico San Juan 12.4 10.91 10.91 10.91

35049 350490020 New Mexico Santa Fe 9.78 8.57 8.57 8.57

36001 360010005 New York Albany 34.26 22.51 22.51 22.51

36005 360050080 New York Bronx 38.87 26.00 26.00 26.00

36005 360050083 New York Bronx 34.74 21.32 21.32 21.32

36005 360050110 New York Bronx 36.11 25.41 25.41 25.41

36013 360130011 New York Chautauqua 29.15 15.82 15.82 15.82

36029 360290005 New York Erie 35.35 25.54 25.54 25.54

36029 360291007 New York Erie 33.61 23.32 23.32 23.32

(continued)
4.A-90

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

36031 360310003 New York Essex 22.45 13.77 13.77 13.77

36047 360470122 New York Kings 36.94 23.04 23.04 23.04

36055 360551007 New York Monroe 32.2 19.38 19.38 19.38

36059 360590008 New York Nassau 34.01 19.15 19.15 19.15

36061 360610056 New York New York 39.7 26.51 26.51 23.61

36061 360610062 New York New York 38.82 23.85 23.85 20.95

36061 360610079 New York New York 37.94 25.73 25.73 22.83

36061 360610128 New York New York 39.45 25.95 25.95 23.05

36063 360632008 New York Niagara 33.87 21.99 21.99 21.99

36067 360671015 New York Onondaga 27.35 16.74 16.74 16.74

36071 360710002 New York Orange 28.92 18.47 18.47 18.47

36081 360810124 New York Queens 35.56 22.44 22.44 22.44

36085 360850055 New York Richmond 34.93 21.17 21.17 21.17

36085 360850067 New York Richmond 32.41 17.57 17.57 17.57

36089 360893001 New York St Lawrence 22.05 15.22 15.22 15.22

36101 361010003 New York Steuben 27.81 14.94 14.94 14.94

36103 361030001 New York Suffolk 34.66 18.09 18.09 18.09

36119 361191002 New York Westchester 33.51 19.41 19.41 19.41

37001 370010002 North Carolina Alamance 31.72 18.09 18.09 18.09

37021 370210034 North Carolina Buncombe 30.05 15.83 15.83 15.83

37033 370330001 North Carolina Caswell 29.45 16.07 16.07 16.07

37035 370350004 North Carolina Catawba 34.53 19.24 19.24 19.24

37037 370370004 North Carolina Chatham 26.94 13.82 13.82 13.82

37051 370510009 North Carolina Cumberland 30.78 17.31 17.31 17.31

37057 370570002 North Carolina Davidson 31.35 18.28 18.28 18.28

37061 370610002 North Carolina Duplin 28.3 15.35 15.35 15.35

37063 370630001 North Carolina Durham 31.02 16.47 16.47 16.47

37065 370650004 North Carolina Edgecombe 26.78 16.60 16.60 16.60

37067 370670022 North Carolina Forsyth 31.92 18.32 18.32 18.32

(continued)
4.A-91

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

37071 370710016 North Carolina Gaston 30.86 16.10 16.10 16.10

37081 370810013 North Carolina Guilford 30.63 17.80 17.80 17.80

37087 370870010 North Carolina Haywood 27.74 16.38 16.38 16.38

37099 370990006 North Carolina Jackson 24.96 13.91 13.91 13.91

37107 371070004 North Carolina Lenoir 25.2 15.55 15.55 15.55

37111 371110004 North Carolina McDowell 31.55 17.30 17.30 17.30

37117 371170001 North Carolina Martin 24.83 14.78 14.78 14.78

37119 371190010 North Carolina Mecklenburg 32.33 18.39 18.39 18.39

37119 371190041 North Carolina Mecklenburg 31.72 16.71 16.71 16.71

37119 371190042 North Carolina Mecklenburg 30.7 16.34 16.34 16.34

37121 371210001 North Carolina Mitchell 30.25 15.29 15.29 15.29

37123 371230001 North Carolina Montgomery 28.21 15.02 15.02 15.02

37129 371290002 North Carolina New Hanover 25.4 13.75 13.75 13.75

37133 371330005 North Carolina Onslow 24.61 14.53 14.53 14.53

37135 371350007 North Carolina Orange 29.35 15.60 15.60 15.60

37147 371470005 North Carolina Pitt 26.21 16.20 16.20 16.20

37155 371550005 North Carolina Robeson 29.92 16.31 16.31 16.31

37159 371590021 North Carolina Rowan 30.23 17.71 17.71 17.71

37173 371730002 North Carolina Swain 27.34 15.03 15.03 15.03

37183 371830014 North Carolina Wake 31.63 16.96 16.96 16.96

37189 371890003 North Carolina Watauga 30.43 15.96 15.96 15.96

37191 371910005 North Carolina Wayne 29.72 17.01 17.01 17.01

38007 380070002 North Dakota Billings 13.07 11.57 11.57 11.57

38013 380130003 North Dakota Burke 16.73 15.05 15.05 15.05

38015 380150003 North Dakota Burleigh 17.62 14.39 14.39 14.39

38017 380171004 North Dakota Cass 21.22 16.05 16.05 16.05

38053 380530002 North Dakota McKenzie 11.96 10.4 10.41 10.41

38057 380570004 North Dakota Mercer 16.98 14.36 14.36 14.36

39009 390090003 Ohio Athens 32.32 15.83 15.83 15.83

(continued)
4.A-92

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30

24-hr DV

39017 390170003 Ohio Butler 39.23 23.53 23.53 23.53

39017 390170016 Ohio Butler 37.14 19.79 19.79 19.79

39017 390170017 Ohio Butler 37.93 20.19 20.19 20.19

39017 390171004 Ohio Butler 37.13 19.29 19.29 19.29

39023 390230005 Ohio Clark 35.37 19.40 19.40 19.40

39025 390250022 Ohio Clermont 34.46 17.07 17.07 17.07

39035 390350027 Ohio Cuyahoga 36.6 24.82 24.82 22.59

39035 390350034 Ohio Cuyahoga 36.58 21.66 21.66 19.46

39035 390350038 Ohio Cuyahoga 44.2 29.73 29.73 27.50

39035 390350045 Ohio Cuyahoga 38.57 23.28 23.28 21.05

39035 390350060 Ohio Cuyahoga 42.12 26.89 26.89 24.66

39035 390350065 Ohio Cuyahoga 38.67 22.85 22.85 20.62

39035 390351002 Ohio Cuyahoga 34.25 20.89 20.89 18.67

39049 390490024 Ohio Franklin 38.51 21.09 21.09 21.09

39049 390490025 Ohio Franklin 38.46 20.11 20.11 20.11

39049 390490081 Ohio Franklin 34.16 18.98 18.98 18.98

39057 390570005 Ohio Greene 32.21 16.98 16.98 16.98

39061 390610006 Ohio Hamilton 37.66 17.85 17.85 17.85

39061 390610014 Ohio Hamilton 38.24 19.50 19.50 19.50

39061 390610040 Ohio Hamilton 36.73 18.87 18.87 18.87

39061 390610042 Ohio Hamilton 37.3 20.82 20.82 20.82

39061 390610043 Ohio Hamilton 35.95 18.63 18.63 18.63

39061 390617001 Ohio Hamilton 38.81 20.11 20.11 20.11

39061 390618001 Ohio Hamilton 40.6 22.10 22.10 22.10

39081 390810017 Ohio Jefferson 40.7 24.05 24.05 24.05

39081 390811001 Ohio Jefferson 41.96 22.59 22.59 22.59

39085 390851001 Ohio Lake 37.16 21.08 21.08 20.88

39087 390870010 Ohio Lawrence 33.77 18.28 18.28 18.28

39093 390933002 Ohio Lorain 31.56 19.08 19.08 18.91

(continued)
4.A-93

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

39095 390950024 Ohio Lucas 36.34 23.56 23.56 23.56

39095 390950025 Ohio Lucas 35.14 25.95 25.95 25.95

39095 390950026 Ohio Lucas 34.9 23.59 23.59 23.59

39099 390990005 Ohio Mahoning 35.16 19.98 19.98 19.98

39099 390990014 Ohio Mahoning 36.83 21.48 21.48 21.48

39113 391130031 Ohio Montgomery 35.78 22.68 22.68 22.68

39113 391130032 Ohio Montgomery 37.8 19.27 19.27 19.27

39133 391330002 Ohio Portage 34.32 18.83 18.83 18.63

39135 391351001 Ohio Preble 32.85 17.51 17.51 17.51

39145 391450013 Ohio Scioto 34.55 18.20 18.20 18.20

39151 391510017 Ohio Stark 36.9 20.19 20.19 20.19

39153 391530017 Ohio Summit 38.06 21.46 21.46 21.26

39153 391530023 Ohio Summit 35.88 20.29 20.29 20.09

39155 391550007 Ohio Trumbull 36.23 21.39 21.39 21.39

40015 400159008 Oklahoma Caddo 23.97 16.68 16.68 16.68

40021 400219002 Oklahoma Cherokee 27.55 20.06 20.06 20.06

40071 400710602 Oklahoma Kay 31.8 25.60 25.60 25.60

40071 400719010 Oklahoma Kay 27.93 20.55 20.55 20.55

40081 400819005 Oklahoma Lincoln 27.83 19.33 19.33 19.33

40097 400970186 Oklahoma Mayes 28.71 21.86 21.86 21.86

40097 400979014 Oklahoma Mayes 26.13 18.49 18.49 18.49

40101 401010169 Oklahoma Muskogee 29.54 20.95 20.95 20.95

40109 401090035 Oklahoma Oklahoma 23.42 16.46 16.46 16.46

40109 401091037 Oklahoma Oklahoma 27.12 19.18 19.18 19.18

40115 401159004 Oklahoma Ottawa 29.14 20.58 20.58 20.58

40121 401210415 Oklahoma Pittsburg 26.37 18.75 18.75 18.75

40135 401359015 Oklahoma Sequoyah 31.43 22.98 22.98 22.98

40143 401430110 Oklahoma Tulsa 28.43 20.69 20.69 20.69

40143 401431127 Oklahoma Tulsa 30.37 21.77 21.77 21.77

(continued)
4.A-94

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30

24-hr DV

41029 410290133 Oregon Jackson 33.72 23.50 23.50 23.50

41029 410291001 Oregon Jackson 14.51 10.43 10.43 10.43

41035 410350004 Oregon Klamath 44.08 30.85 30.85 30.14

41039 410390060 Oregon Lane 32.55 21.42 21.42 16.81

41039 410391007 Oregon Lane 15.63 10.16 10.16 5.56

41039 410391009 Oregon Lane 23.96 16.59 16.59 11.98

41039 410392013 Oregon Lane 48.95 34.01 34.01 29.40

41051 410510080 Oregon Multnomah 29.88 19.10 19.10 19.10

41051 410510246 Oregon Multnomah 23.22 15.24 15.24 15.24

41061 410610119 Oregon Union 27.38 22.64 22.64 22.64

42001 420010001 Pennsylvania Adams 34.93 20.05 20.05 20.05

42003 420030008 Pennsylvania Allegheny 39.44 22.23 16.72 11.72

42003 420030021 Pennsylvania Allegheny 35.16 19.37 13.86 8.86

42003 420030064 Pennsylvania Allegheny 64.27 41.03 35.49 30.48

42003 420030067 Pennsylvania Allegheny 36.48 17.26 11.76 6.76

42003 420030093 Pennsylvania Allegheny 45.6 24.65 24.65 24.65

42003 420030095 Pennsylvania Allegheny 38.77 21.02 15.51 10.51

42003 420030116 Pennsylvania Allegheny 42.56 22.61 17.10 12.10

42003 420030133 Pennsylvania Allegheny 39.23 24.73 24.73 24.73

42003 420031008 Pennsylvania Allegheny 41.34 21.40 15.88 10.88

42003 420031301 Pennsylvania Allegheny 40.3 20.93 15.40 10.40

42003 420033007 Pennsylvania Allegheny 37.52 21.63 16.12 11.12

42003 420039002 Pennsylvania Allegheny 37.86 20.14 14.62 9.62

42007 420070014 Pennsylvania Beaver 43.42 23.46 23.32 23.32

42011 420110011 Pennsylvania Berks 37.71 27.18 27.18 27.18

42017 420170012 Pennsylvania Bucks 34.01 20.66 20.66 20.66

42021 420210011 Pennsylvania Cambria 39.04 19.60 19.60 19.60

42027 420270100 Pennsylvania Centre 36.28 21.01 21.01 21.01

42029 420290100 Pennsylvania Chester 36.7 22.40 22.40 22.40

(continued)
4.A-95

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35

24-hr DV

2020 

11/30 

24-hr DV

42041 420410101 Pennsylvania Cumberland 38 25.33 25.33 25.33

42043 420430401 Pennsylvania Dauphin 38.04 26.65 26.65 26.65

42045 420450002 Pennsylvania Delaware 35.24 21.08 21.08 21.08

42049 420490003 Pennsylvania Erie 34.46 20.16 20.16 20.16

42069 420692006 Pennsylvania Lackawanna 31.55 17.61 17.61 17.61

42071 420710007 Pennsylvania Lancaster 40.83 30.51 30.51 30.47

42077 420770004 Pennsylvania Lehigh 36.4 24.04 24.04 24.04

42079 420791101 Pennsylvania Luzerne 32.46 20.14 20.14 20.14

42085 420850100 Pennsylvania Mercer 36.3 20.84 20.84 20.84

42095 420950025 Pennsylvania Northampton 36.72 22.79 22.79 22.79

42099 420990301 Pennsylvania Perry 30.46 20.22 20.22 20.22

42101 421010004 Pennsylvania Philadelphia 36.53 21.31 21.31 21.31

42101 421010024 Pennsylvania Philadelphia 35.96 19.61 19.61 19.61

42101 421010047 Pennsylvania Philadelphia 37.3 21.84 21.84 21.84

42125 421250005 Pennsylvania Washington 35.52 19.95 19.81 19.81

42125 421250200 Pennsylvania Washington 33.5 18.59 18.44 18.44

42125 421255001 Pennsylvania Washington 38.14 17.33 17.20 17.20

42129 421290008 Pennsylvania Westmoreland 37.12 18.80 18.66 18.66

42133 421330008 Pennsylvania York 38.24 28.16 28.16 28.16

44007 440070022 Rhode Island Providence 29.46 17.18 17.18 17.18

44007 440070026 Rhode Island Providence 30.62 18.87 18.87 18.87

44007 440070028 Rhode Island Providence 28.1 17.47 17.47 17.47

44007 440071010 Rhode Island Providence 28.8 17.32 17.32 17.32

45019 450190049 South Carolina Charleston 27.93 15.52 15.52 15.52

45025 450250001 South Carolina Chesterfield 28.77 16.09 16.09 16.09

45037 450370001 South Carolina Edgefield 32.23 17.45 17.45 17.45

45041 450410002 South Carolina Florence 28.81 16.50 16.50 16.50

45045 450450008 South Carolina Greenville 31.86 18.71 18.71 18.71

45045 450450009 South Carolina Greenville 32.55 18.18 18.18 18.18

(continued)
4.A-96

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

45047 450470003 South Carolina Greenwood 30.01 16.33 16.33 16.33

45051 450510002 South Carolina Horry 28.3 16.66 16.66 16.66

45063 450630008 South Carolina Lexington 32.86 19.02 19.02 19.02

45073 450730001 South Carolina Oconee 27.98 14.56 14.56 14.56

45079 450790007 South Carolina Richland 31.38 17.08 17.08 17.08

45079 450790019 South Carolina Richland 33.2 19.00 19.00 19.00

45083 450830010 South Carolina Spartanburg 32.46 17.99 17.99 17.99

46011 460110002 South Dakota Brookings 23.54 17.21 17.21 17.21

46013 460130003 South Dakota Brown 18.73 14.31 14.31 14.31

46029 460290002 South Dakota Codington 23.67 17.81 17.81 17.81

46033 460330132 South Dakota Custer 14.36 12.03 12.03 12.03

46071 460710001 South Dakota Jackson 12.73 10.27 10.27 10.27

46099 460990006 South Dakota Minnehaha 24.17 17.48 17.48 17.48

46099 460990007 South Dakota Minnehaha 23.98 16.91 16.91 16.91

46103 461030016 South Dakota Pennington 17.2 14.48 14.48 14.48

46103 461030020 South Dakota Pennington 18.58 16.21 16.21 16.21

46103 461031001 South Dakota Pennington 15.95 13.29 13.29 13.29

47009 470090011 Tennessee Blount 32.54 18.75 18.75 18.75

47037 470370023 Tennessee Davidson 33.5 18.05 18.05 18.05

47037 470370025 Tennessee Davidson 30.93 16.82 16.82 16.82

47037 470370036 Tennessee Davidson 32.71 16.15 16.15 16.15

47045 470450004 Tennessee Dyer 31.92 17.63 17.63 17.63

47065 470650031 Tennessee Hamilton 33.25 20.49 20.49 20.49

47065 470651011 Tennessee Hamilton 29.74 14.88 14.88 14.88

47065 470654002 Tennessee Hamilton 33.53 18.24 18.24 18.24

47093 470930028 Tennessee Knox 36.66 20.46 20.46 20.46

47093 470931017 Tennessee Knox 33.46 19.45 19.45 19.45

47099 470990002 Tennessee Lawrence 28.48 14.91 14.91 14.91

47105 471050108 Tennessee Loudon 32.2 19.93 19.93 19.93

(continued)
4.A-97

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

47107 471071002 Tennessee Mc Minn 32.73 17.70 17.70 17.70

47119 471192007 Tennessee Maury 30.96 16.91 16.91 16.91

47125 471251009 Tennessee Montgomery 36.3 17.88 17.88 17.88

47141 471410001 Tennessee Putnam 32.66 16.31 16.31 16.31

47145 471450004 Tennessee Roane 30.24 15.93 15.93 15.93

47157 471570014 Tennessee Shelby 32.25 16.94 16.94 16.94

47157 471570038 Tennessee Shelby 32.52 16.25 16.25 16.25

47157 471570047 Tennessee Shelby 33.5 16.90 16.90 16.90

47157 471571004 Tennessee Shelby 29.88 15.72 15.72 15.72

47163 471631007 Tennessee Sullivan 31.13 18.99 18.99 18.99

47165 471650007 Tennessee Sumner 33.66 15.20 15.20 15.20

48037 480370004 Texas Bowie 29.42 19.29 19.29 19.29

48113 481130050 Texas Dallas 27.44 17.73 17.73 17.73

48113 481130069 Texas Dallas 25.7 16.73 16.73 16.73

48113 481130087 Texas Dallas 24.21 15.08 15.08 15.08

48135 481350003 Texas Ector 17.81 13.75 13.75 13.75

48141 481410037 Texas El Paso 22.93 19.47 19.47 19.47

48201 482011035 Texas Harris 30.81 21.23 21.23 19.46

48203 482030002 Texas Harrison 25.95 17.31 17.31 17.31

48215 482150043 Texas Hidalgo 26.42 22.24 22.24 22.24

48355 483550032 Texas Nueces 27.55 18.66 18.66 18.66

48355 483550034 Texas Nueces 20.74 12.40 12.40 12.40

48361 483611001 Texas Orange 27.78 18.57 18.57 18.57

48439 484391002 Texas Tarrant 25.34 16.26 16.26 16.26

48439 484391006 Texas Tarrant 25.76 16.82 16.82 16.82

49003 490030003 Utah Box Elder 33.2 27.74 27.46 27.44

49005 490050004 Utah Cache 56.95 42.65 35.48 30.48

49011 490110004 Utah Davis 38.95 31.35 31.35 29.56

49035 490350003 Utah Salt Lake 47.36 33.48 32.06 27.20

(continued)
4.A-98

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

49035 490350012 Utah Salt Lake 50.14 36.73 35.31 30.48

49035 490351001 Utah Salt Lake 37.73 30.29 28.87 24.04

49035 490353006 Utah Salt Lake 47.84 34.97 33.55 28.70

49035 490353007 Utah Salt Lake 45.38 36.10 34.68 29.80

49035 490353008 Utah Salt Lake 30.07 25.11 23.69 19.01

49045 490450003 Utah Tooele 30.53 26.09 26.09 25.32

49049 490490002 Utah Utah 38.18 29.25 29.25 24.92

49049 490494001 Utah Utah 44 33.95 33.95 29.61

49049 490495008 Utah Utah 35.9 27.60 27.60 23.36

49049 490495010 Utah Utah 35.93 28.13 28.13 23.86

49057 490570002 Utah Weber 38.58 30.01 29.68 29.66

49057 490570007 Utah Weber 33.6 26.35 26.03 26.01

49057 490571003 Utah Weber 36.16 28.34 28.02 27.99

50001 500010002 Vermont Addison 28.2 17.10 17.10 17.10

50001 500010003 Vermont Addison 31.73 18.53 18.53 18.53

50003 500030004 Vermont Bennington 26.47 15.89 15.89 15.89

50007 500070012 Vermont Chittenden 29.84 18.90 18.90 18.90

50007 500070014 Vermont Chittenden 30.13 21.58 21.58 21.58

50021 500210002 Vermont Rutland 30.6 22.73 22.73 22.73

51013 510130020 Virginia Arlington 34.18 18.75 18.75 18.75

51036 510360002 Virginia Charles City 31.76 16.76 16.76 16.76

51041 510410003 Virginia Chesterfield 31.25 15.30 15.30 15.30

51059 510590030 Virginia Fairfax 34.47 18.50 18.50 18.50

51059 510591005 Virginia Fairfax 33.72 18.14 18.14 18.14

51059 510595001 Virginia Fairfax 33.31 19.36 19.36 19.36

51087 510870014 Virginia Henrico 31.95 16.57 16.57 16.57

51087 510870015 Virginia Henrico 29.18 14.29 14.29 14.29

51107 511071005 Virginia Loudoun 34.45 19.24 19.24 19.24

51139 511390004 Virginia Page 30.06 16.65 16.65 16.65

(continued)
4.A-99

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35

24-hr DV

2020 

11/30 

24-hr DV

51520 515200006 Virginia Bristol City 30.24 16.20 16.20 16.20

51650 516500004 Virginia Hampton City 29.01 15.90 15.90 15.90

51680 516800015 Virginia Lynchburg City 30.71 15.77 15.77 15.77

51710 517100024 Virginia Norfolk City 29.66 16.97 16.97 16.97

51770 517700014 Virginia Roanoke City 32.7 18.00 18.00 18.00

51775 517750010 Virginia Salem City 34.06 19.37 19.37 19.37

53033 530330024 Washington King 28.78 20.60 20.60 20.60

53033 530330057 Washington King 29.16 20.74 20.74 20.74

53033 530330080 Washington King 22.03 16.10 16.10 16.10

53053 530530029 Washington Pierce 41.82 31.00 31.00 30.41

53061 530611007 Washington Snohomish 34.36 26.99 26.99 26.99

53063 530630016 Washington Spokane 29.7 19.15 19.15 19.15

53063 530630047 Washington Spokane 29.86 18.60 18.60 18.60

54003 540030003 West Virginia Berkeley 34.51 23.43 23.43 23.43

54009 540090005 West Virginia Brooke 39.43 22.36 22.36 22.36

54009 540090011 West Virginia Brooke 43.9 25.30 25.30 25.30

54011 540110006 West Virginia Cabell 35.1 18.06 18.06 18.06

54029 540291004 West Virginia Hancock 40.64 20.54 20.54 20.54

54033 540330003 West Virginia Harrison 33.53 15.75 15.75 15.75

54039 540390010 West Virginia Kanawha 34.73 16.61 16.61 16.61

54039 540390011 West Virginia Kanawha 33.1 16.24 16.24 16.24

54039 540391005 West Virginia Kanawha 36.98 18.25 18.25 18.25

54049 540490006 West Virginia Marion 33.68 15.56 15.56 15.56

54051 540511002 West Virginia Marshall 33.98 16.98 16.98 16.98

54061 540610003 West Virginia Monongalia 35.65 14.68 14.68 14.68

54069 540690010 West Virginia Ohio 32 16.50 16.50 16.50

54081 540810002 West Virginia Raleigh 30.67 14.42 14.42 14.42

54089 540890001 West Virginia Summers 31.26 14.30 14.30 14.30

54107 541071002 West Virginia Wood 35.44 17.75 17.75 17.75

(continued)
4.A-100

Table 4.A-12. 24-hr Design Values (DVs) for the 2005 and 2020 Base Case and After Meeting 

the Current and Proposed Alternative Standard Levels: 2020 Baseline (15/35) 

and 2020 11/30 (continued)

FIPS Monitor ID State Name County Name

2005

24-hr DV

2020

24-hr DV

2020 

15/35 

24-hr DV

2020 

11/30 

24-hr DV

55003 550030010 Wisconsin Ashland 18.61 12.48 12.48 12.48

55009 550090005 Wisconsin Brown 36.56 24.89 24.89 24.89

55009 550090009 Wisconsin Brown 35.86 25.53 25.53 25.53

55025 550250047 Wisconsin Dane 35.57 24.20 24.20 24.20

55027 550270007 Wisconsin Dodge 31.82 21.63 21.63 21.63

55041 550410007 Wisconsin Forest 25.26 17.13 17.13 17.13

55043 550430009 Wisconsin Grant 34.35 24.95 24.95 24.95

55059 550590019 Wisconsin Kenosha 32.78 22.88 22.88 22.88

55071 550710007 Wisconsin Manitowoc 29.7 21.11 21.11 21.11

55079 550790010 Wisconsin Milwaukee 38.67 26.12 26.12 26.12

55079 550790026 Wisconsin Milwaukee 37.38 24.90 24.90 24.90

55079 550790043 Wisconsin Milwaukee 39.92 26.08 26.08 26.08

55079 550790059 Wisconsin Milwaukee 35.56 24.18 24.18 24.18

55079 550790099 Wisconsin Milwaukee 37.78 25.75 25.75 25.75

55087 550870009 Wisconsin Outagamie 32.87 23.37 23.37 23.37

55089 550890009 Wisconsin Ozaukee 32.53 22.69 22.69 22.69

55109 551091002 Wisconsin St Croix 26.66 19.57 19.57 19.57

55111 551110007 Wisconsin Sauk 28.63 21.31 21.31 21.31

55119 551198001 Wisconsin Taylor 25.38 18.12 18.12 18.12

55125 551250001 Wisconsin Vilas 22.61 16.14 16.14 16.14

55133 551330027 Wisconsin Waukesha 35.48 24.68 24.68 24.68

56005 560050877 Wyoming Campbell 18.63 17.12 17.12 17.12

56005 560050892 Wyoming Campbell 12.55 12.19 12.19 12.19

56005 560050899 Wyoming Campbell 12.66 12.19 12.19 12.19

56009 560090819 Wyoming Converse 10 9.33 9.33 9.33

56013 560131003 Wyoming Fremont 29.8 23.81 23.81 23.81

56021 560210001 Wyoming Laramie 11.93 10.0 10.07 10.07

56033 560330002 Wyoming Sheridan 30.86 27.17 27.17 27.17
4.A-101

4.A.3 References

U.S. Environmental Protection Agency (EPA). Fugitive Dust Background Document and Technical 

Information Document and Technical Information Document for Best Available Control 

Measures (EPA-450/2-92-004). September 1992.

U.S. Environmental Protection Agency (EPA). “Chapter 13:2.1: Paved Roads,” AP-42, Fifth 

Edition, Volume I, 2003. Available at 

http://www.epa.gov/ttn/chief/ap42/ch13/index.html.

U.S. Environmental Protection Agency (EPA). “Chapter 13:2.2: Unpaved Roads,” AP-42, Fifth 

Edition, Volume I, 2003. Available at 

http://www.epa.gov/ttn/chief/ap42/ch13/index.html.

U.S. Environmental Protection Agency, Region 10 (EPA). Agricultural Burning, accessed 

November 3, 2005 from 

http://yosemite.epa.gov/R10/AIRPAGE.NSF/webpage/Agricultural+Burning.

U.S. Department of Agriculture (USDA), Agricultural Research Service. Air Quality Programs 

Action Plan, October 6, 2000. 

http://www.ars.usda.gov/research/programs/programs.htm?np_code=203&docid=317

&page=3&pf=1&cg_id=8.

Western Regional Air Partnership (WRAP). WRAP Fugitive Dust Handbook, prepared by 

Countess Environmental, November 15, 2004. Available at 

http://www.ndep.nv.gov/baqp/WRAP/INDEX.html.
5-1

CHAPTER 5

HUMAN HEALTH BENEFITS ANALYSIS APPROACH AND RESULTS

5.1 Synopsis

This chapter presents the estimated human health benefits for the proposed National 

Ambient Air Quality Standards (NAAQS) for particulate matter (PM). In this chapter, we quantify 

the health-related benefits of the fine particulate matter (PM2.5)-related air quality 

improvements resulting from the illustrative emission control scenarios that reduce emissions 

of directly emitted particles and precursor pollutants including SO2 and NOx to attain alternative

PM2.5 NAAQS levels in 2020.

These benefits are relative to a 2020 baseline reflecting attainment of the current 

primary PM2.5 standards (i.e., annual standard at 15 μg/m3 and 24-hour standard of 35 μg/m3

, 

referred to as “15/35”) that includes promulgated national regulations and illustrative emission 

controls to simulate attainment with 15/35. We project PM2.5 levels in certain areas would 

exceed 13/35, 12/35, 11/35, and 11/30 after illustrative controls to simulate attainment with 

15/35. In analyzing the current 15/35 standard (baseline), EPA determined that all counties 

would meet the 14/35 standard concurrently with meeting the existing 15/35 standard at no 

additional cost. Consequently, there are no incremental costs or benefits for 14/35, and no 

need to present an analysis of 14/35. Table 5-1 summarizes the total monetized benefits of 

these alternative PM2.5 standards in 2020. These estimates reflect the sum of the estimated 

PM2.5 mortality impacts identified and the value of all morbidity impacts.

Table 5-1. Estimated Monetized Benefits of the Proposed and Alternative Combinations of 

PM2.5 Standards in 2020, Incremental to Attainment of 15/35 (millions of 2006$)a

Benefits Estimate

13 μg/m3 Annual 

& 35 μg/m3 24-Hour

12 μg/m3 Annual

& 35 μg/m3 24-Hour

11 μg/m3 Annual

& 35 μg/m3 24-Hour

11 μg/m3 Annual

& 30 μg/m3 24-Hour

Economic value of avoided PM2.5-related morbidities and premature deaths using PM2.5 mortality estimate from 

Krewski et al. (2009)

3% discount rate $88 + B $2,300 +B $9,2000+B $14,000 +B

7% discount rate $79 + B $2,100 +B $8,3000 +B $13,000 +B

Economic value of avoided PM2.5-related morbidities and premature deaths using PM2.5 mortality estimate from 

Laden et al. (2006)

3% discount rate $220 + B $5,900 +B $23,000 +B $36,000 +B

7% discount rate $200 + B $5,400+B $21,000 +B $33,000 +B

a

Rounded to two significant figures. Avoided premature deaths account for over 98% of monetized benefits here, 

which are discounted over the SAB-recommended 20-year segmented lag. It was not all possible to quantify all 

benefits due to data limitations in this analysis. “B” is the sum of all unquantified health and welfare benefits.
5-2

For annual standards at 12 μg/m3 and 13 μg/m3, the majority of benefits (i.e., 70% and 

98%, respectively) occur in California because this highly populated area is where the most air 

quality improvement beyond 15/35 is needed to reach these levels. In addition, several recent 

rules such as the Mercury and Air Toxics Standard (MATS) and the Cross-State Air Pollution Rule 

(CSAPR) will have substantially reduced PM2.5 levels by 2020 in the East, thus few additional 

controls would be needed to reach 12/35 or 13/35 in the East.

In general, we have greater confidence in risk estimates based on PM2.5 concentrations 

where the bulk of the data reside and somewhat less confidence where data density is lower.

As noted in the preamble to the proposed rule, the range from the 25th to 10th percentiles of 

the air quality data used the epidemiology studies is a reasonable range below which we have 

appreciably less confidence in the associations observed in the epidemiological studies. Most of 

the estimated avoided premature deaths occur at or above the lowest measured PM2.5 

concentration in the two studies used to estimate mortality benefits.

In addition to PM2.5 benefits, implementation of emissions controls to attain the 

alternative PM2.5 standards would reduce other ambient pollutants, such as SO2, NO2, and 

ozone. However, because the method used in this analysis to simulate attainment does not 

simulate changes in ambient concentrations of other pollutants, we were not able to quantify 

the co-benefits of reduced exposure to other pollutants. In addition, due to data and 

methodology limitations, we were unable to estimate additional health benefits associated 

with exposure to PM2.5 or the additional benefits from improvements in welfare effects, such as 

ecosystem effects and visibility. We describe the unquantified health benefits in this chapter 

and the unquantified welfare benefits in Chapter 6.

5.2 Overview

This chapter contains a subset of the estimated health benefits of the proposed and 

alternative PM2.5 standards in 2020 that EPA was able to quantify, given the available resources 

and methods. The analysis in this chapter aims to characterize the benefits of the air quality 

changes resulting from the implementation of new PM standards by answering two key 

questions:

1. What are the health effects of changes in ambient particulate matter (PM2.5) 

resulting from reductions in directly emitted PM2.5 and precursors due to the 

attainment of a new PM2.5 standard?

2. What is the economic value of these effects?
5-3

In this analysis, we consider an array of health impacts attributable to changes in PM2.5. 

The Integrated Science Assessment for Particulate Matter (U.S. EPA, 2009b) identifies the 

human health effects associated with ambient particles, which include premature mortality and 

a variety of morbidity effects associated with acute and chronic exposures. Table 5-2

summarizes human health categories contained within the main benefits estimate as well as 

those categories that were unquantified due to limited data or resources. It is important to 

emphasize that the list of unquantified benefit categories is not exhaustive, nor is quantification 

of each effect complete. In order to identify the most meaningful human health and 

environmental co-benefits, we excluded effects not identified as having at least a causal, likely 

causal, or suggestive relationship with the affected pollutants in the most recent 

comprehensive scientific assessment, such as an Integrated Science Assessment (ISA). This does 

not imply that additional relationships between these and other human health and 

environmental co-benefits and the affected pollutants do not exist. Due to this decision 

criterion, some effects that were identified in previous lists of unquantified benefits in other 

RIAs have been dropped (e.g., UVb exposure).

The benefits analysis in this chapter relies on an array of data inputs—including air 

quality modeling, health impact functions and valuation estimates among others—which are 

themselves subject to uncertainty and may also in turn contribute to the overall uncertainty in 

this analysis. We employ several techniques to characterize this uncertainty, which are 

described in detail in section 5.4.

As described in Chapter 1, there are important differences worth noting in the design 

and analytical objectives of NAAQS RIAs compared to RIAs for implementation rules, such as 

the recent MATS rule (U.S. EPA, 2011d). The NAAQS RIAs illustrate the potential costs and 

benefits of attaining a revised air quality standard nationwide based on an array of emission 

control strategies for different sources, incremental to implementation of existing regulations 

and controls needed to attain current standards. In short, NAAQS RIAs hypothesize, but do not 

predict, the control strategies that States may choose to enact when implementing a revised 

NAAQS. The setting of a NAAQS does not directly result in costs or benefits, and as such, NAAQS 

RIAs are merely illustrative and are not intended to be added to the costs and benefits of other 

regulations that result in specific costs of control and emission reductions. By contrast, the 

emission reductions from implementation rules are generally for specific, well-characterized 

sources, such as the recent MATS rule (U.S. EPA, 2011d). In general, EPA is more confident in 

the magnitude and location of the emission reductions for implementation rules. As such, 

emission reductions achieved under promulgated implementation rules such as MATS have 
5-4

been reflected in the baseline of this NAAQS analysis. Subsequent implementation rules will be 

reflected in the baseline for the next PM NAAQS review. For this reason, the benefits estimated 

provided in this RIA and all other NAAQS RIAs should not be added to the benefits estimated for 

implementation rules.

Table 5-2. Human Health Effects of Pollutants Potentially Affected by Attainment of the 

Primary PM2.5 Standards

Benefits Category Specific Effect

Effect Has 

Been 

Quantified

Effect Has 

Been 

Monetized

More 

Information

Improved Human Health

Reduced 

incidence of 

premature 

mortality from 

exposure to PM2.5

Adult premature mortality based on cohort 

study estimates and expert elicitation 

estimates (age >25 or age >30)

  Section 5.6

Infant mortality (age <1)   Section 5.6

Reduced 

incidence of 

morbidity from 

exposure to PM2.5

Non-fatal heart attacks (age > 18)   Section 5.6

Hospital admissions—respiratory (all ages)   Section 5.6

Hospital admissions—cardiovascular (age 

>20)

  Section 5.6

Emergency department visits for asthma (all 

ages)

  Section 5.6

Acute bronchitis (age 8–12)   Section 5.6

Lower respiratory symptoms (age 7–14)   Section 5.6

Upper respiratory symptoms (asthmatics age 

9–11)

  Section 5.6

Asthma exacerbation (asthmatics age 6–18)   Section 5.6

Lost work days (age 18–65)   Section 5.6

Minor restricted-activity days (age 18–65)   Section 5.6

Chronic Bronchitis (age >26) —4 —4 Section 5.6

Emergency department visits for 

cardiovascular effects (all ages)

—4 —4 Section 5.6

Strokes and cerebrovascular disease (age 50–

79)

—4 —4 Section 5.6

Other cardiovascular effects (e.g., other ages) — — PM ISA2

Other respiratory effects (e.g., pulmonary 

function, non-asthma ER visits, non-bronchitis 

chronic diseases, other ages and populations)

— — PM ISA2

Reproductive and developmental effects 

(e.g., low birth weight, pre-term births, etc)

— — PM ISA2,3

Cancer, mutagenicity, and genotoxicity 

effects

— — PM ISA2,3

(continued)
5-5

Table 5-2. Human Health Effects of Pollutants Potentially Affected by Attainment of the 

Primary PM2.5 Standards (continued)

Benefits Category Specific Effect

Effect Has 

Been 

Quantified

Effect Has 

Been 

Monetized

More 

Information

Reduced incidence 

of mortality from 

exposure to ozone

Premature mortality based on short-term 

study estimates (all ages)

— — Ozone CD, Draft 

Ozone ISA1

Premature mortality based on long-term 

study estimates (age 30–99)

— — Ozone CD, Draft 

Ozone ISA1

Hospital admissions—respiratory causes (age 

> 65)

— — Ozone CD, Draft 

ISA1

Hospital admissions—respiratory causes (age 

<2)

— — Ozone CD, Draft 

ISA1

Emergency department visits for asthma (all 

ages)

— — Ozone CD, Draft 

ISA1

Minor restricted-activity days (age 18–65) — — Ozone CD, Draft 

ISA1

School absence days (age 5–17) — — Ozone CD, Draft 

ISA1

Decreased outdoor worker productivity (age 

18–65)

— — Ozone CD, Draft 

ISA1

Other respiratory effects (e.g., premature 

aging of lungs)

— — Ozone CD, Draft 

ISA2

Cardiovascular and nervous system effects — — Ozone CD, Draft 

ISA3

Reproductive and developmental effects — — Ozone CD, Draft 

ISA3

Reduced incidence 

of morbidity from 

exposure to NO2

Asthma hospital admissions (all ages) — — NO2 ISA1

Chronic lung disease hospital admissions 

(age > 65)

— — NO2 ISA1

Respiratory emergency department visits (all 

ages)

— — NO2 ISA1

Asthma exacerbation (asthmatics age 4–18) — — NO2 ISA1

Acute respiratory symptoms (age 7–14) — — NO2 ISA1

Premature mortality — — NO2 ISA2,3

Other respiratory effects (e.g., airway 

hyperresponsiveness and inflammation, lung 

function, other ages and populations)

— — NO2 ISA2,3

(continued)
5-6

Table 5-2. Human Health Effects of Pollutants Potentially Affected by Attainment of the 

Primary PM2.5 Standards (continued)

Benefits Category Specific Effect

Effect Has 

Been 

Quantified

Effect Has 

Been 

Monetized

More 

Information

Reduced incidence 

of morbidity from 

exposure to SO2

Respiratory hospital admissions (age > 65) — — SO2 ISA1

Asthma emergency department visits (all 

ages)

— — SO2 ISA1

Asthma exacerbation (asthmatics age 4–12) — — SO2 ISA1

Acute respiratory symptoms (age 7–14) — — SO2 ISA1

Premature mortality — — SO2 ISA2,3

Other respiratory effects (e.g., airway 

hyperresponsiveness and inflammation, lung 

function, other ages and populations)

— — SO2 ISA2,3

Reduced incidence 

of morbidity from 

exposure to 

methylmercury 

(through role of 

sulfate in 

methylation)

Neurologic effects—IQ loss — — IRIS; NRC, 20001

Other neurologic effects (e.g., 

developmental delays, memory, behavior)

— — IRIS; NRC, 20002

Cardiovascular effects — — IRIS; NRC, 

20002,3

Genotoxic, immunologic, and other toxic 

effects

— — IRIS; NRC, 

20002,3

1 We assess these benefits qualitative due to time and resource limitations for this analysis.

2 We assess these benefits qualitatively because we do not have sufficient confidence in available data or 

methods.

3 We assess these benefits qualitatively because current evidence is only suggestive of causality or there are other 

significant concerns over the strength of the association.

4 We quantify these benefits in a sensitivity analysis, but not the main analysis.

5.3 Updated Methodology Presented in this RIA

The benefits analysis presented in this chapter incorporates an array of policy and 

technical changes that the Agency has adopted since the previous review of the PM2.5 standards 

in 2006, and since publication of the most recent major benefits analysis, documented in the 

benefits chapter of the RIA accompanying the final MATS(U.S. EPA, 2011d). Below we note the 

aspects of this analysis that differ from the MATS RIA:

1. Incorporation of the newest American Cancer Society (ACS) mortality study. In 2009,

the Health Effects Institute published an extended analysis of the ACS cohort 

(Krewski et al., 2009). Compared to the study it replaces (Pope et al., 2002), this new 

analysis incorporates a number of methodological improvements that we describe in 

detail below. The all-cause PM2.5 mortality risk estimate drawn from Krewski et al. 
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(2009) is identical to the Pope et al. (2002) risk estimate applied in recent EPA 

analyses of long-term PM2.5 mortality but has narrower confidence intervals.

2. Updated health endpoints. We have moved the quantification of chronic bronchitis 

from our main analysis to a sensitivity analysis. This change is consistent with the 

findings of the Integrated Science Assessment (ISA) that the evidence for an 

association between long-term exposure to PM2.5 and respiratory effects is more 

tenuous (U.S. EPA, 2009). We also add two new sensitivity analyses, including an 

assessment of PM-related cerebrovascular disease and cardiovascular emergency 

department visits. The incorporation of these two new endpoints follows the 

findings of the PM ISA that recent studies have strengthened the relationship 

between PM2.5 exposure and cardiovascular outcomes (U.S. EPA, 2009b).

3. Incorporation of new morbidity studies. Since the publication of the 2004 Criteria 

Document for Particulate Matter (U.S. EPA, 2004) the epidemiological literature has 

produced a significant number of new studies examining the association between 

short-term PM2.5 exposure and acute myocardial infarctions, respiratory and 

cardiovascular hospitalizations, respiratory emergency department visits, acute 

respiratory symptoms and exacerbation of asthma. Upon careful evaluation of this 

new literature we have incorporated new studies into our health impact 

assessment; in many cases we have replaced older single-city time-series studies 

with newer multi-city time-series analyses.

4. Updated hospital cost-of-illness (COI), including median wage data. In previous 

versions of BenMAP, estimates of hospital charges and lengths of hospital stays 

were based on discharge statistics provided by the Agency for Healthcare Research 

and Quality’s Healthcare Utilization Project National Inpatient Sample (NIS) database 

for 2000 (AHRQ, 2000). The newest version of BenMAP (version 4.0.51) used in this 

analysis updated this information to use the 2007 database. The data source for the 

updated median annual income is the 2007 American Community Survey (ACS, 

2007).

5. Expanded uncertainty assessment. We have incorporated a more comprehensive 

assessment of the various uncertain parameters and assumptions within the 

benefits analysis.

While the list above identifies the major changes implemented since the MATS RIA, EPA 

has updated several additional components of the benefits analysis since the 2006 PM NAAQS 

RIA (U.S. EPA, 2006a). In the Portland Cement NESHAP proposal RIA (U.S. EPA, 2009a), the 

Agency removed the threshold assumption in the concentration-response function for PM2.5-

related health effects and began using the benefits derived from the two major cohort studies 

of PM2.5 and mortality as the main benefits estimates, while still including a range of sensitivity 

estimates based on EPA’s PM2.5 mortality expert elicitation. In the NO2 NAAQS proposal RIA 
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(U.S. EPA, 2009a), we revised the estimate used for the value-of-a-statistical life to be 

consistent with Agency guidance. In the proposed CSAPR (previously the “Transport Rule”) (U.S. 

EPA, 2010g), we incorporated the “lowest measured level” assessment to help characterize 

uncertainty in estimates of benefits of reductions in PM2.5 at lower baseline concentrations of 

PM2.5. In the final CSAPR (U.S. EPA, 2011c), we updated the baseline incidence rates for hospital 

admissions and emergency department visits and asthma prevalence rates. We direct the 

reader to each of these RIAs for more information on these changes.

5.4 Human Health Benefits Analysis Methods

We follow a “damage-function” approach in calculating total benefits of the modeled 

changes in environmental quality. This approach estimates changes in individual health and 

welfare endpoints (specific effects that can be associated with changes in air quality) and 

assigns values to those changes assuming independence of the values for those individual 

endpoints. Total benefits are calculated simply as the sum of the values for all non-overlapping 

health and welfare endpoints. The “damage-function” approach is the standard method for 

assessing costs and benefits of environmental quality programs and has been used in several 

recent published analyses (Levy et al., 2009; Fann et al., 2012a; Tagaris et al., 2009).

To assess economic value in a damage-function framework, the changes in 

environmental quality must be translated into effects on people or on the things that people 

value. In some cases, the changes in environmental quality can be directly valued, as is the case 

for changes in visibility. In other cases, such as for changes in ozone and PM, a health and 

welfare impact analysis must first be conducted to convert air quality changes into effects that 

can be assigned dollar values. For the purposes of this RIA, the health impacts analysis (HIA) is 

limited to those health effects that are directly linked to ambient levels of air pollution and 

specifically to those linked to PM2.5.

We note at the outset that EPA rarely has the time or resources to perform extensive 

new research to measure directly either the health outcomes or their values for regulatory 

analyses. Thus, similar to Kunzli et al. (2000) and other, more recent health impact analyses, our 

estimates are based on the best available methods of benefits transfer. Benefits transfer is the 

science and art of adapting primary research from similar contexts to obtain the most accurate 

measure of benefits for the environmental quality change under analysis. Adjustments are 

made for the level of environmental quality change, the socio-demographic and economic 

characteristics of the affected population, and other factors to improve the accuracy and 

robustness of benefits estimates.
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5.4.1 Health Impact Assessment

The Health Impact Assessment (HIA) quantifies the changes in the incidence of adverse 

health impacts resulting from changes in human exposure to PM2.5 and ozone air quality. HIAs 

are a well-established approach for estimating the retrospective or prospective change in 

adverse health impacts expected to result from population-level changes in exposure to 

pollutants (Levy et al., 2009). PC-based tools such as the environmental Benefits Mapping and 

Analysis Program (BenMAP) can systematize health impact analyses by applying a database of 

key input parameters, including health impact functions and population projections—provided 

that key input data are available, including air quality estimates and risk coefficients (Abt 

Associates, 2010). Analysts have applied the HIA approach to estimate human health impacts 

resulting from hypothetical changes in pollutant levels (Hubbell et al., 2005; Tagaris et al., 2009; 

Fann et al., 2012a). EPA and others have relied upon this method to predict future changes in 

health impacts expected to result from the implementation of regulations affecting air quality 

(e.g., U.S. EPA, 2011d). For this assessment, the HIA is limited to those health effects that are 

directly linked to ambient PM2.5 concentrations. There may be other indirect health impacts 

associated with implementing emissions controls, such as occupational health exposures.

The HIA approach used in this analysis involves three basic steps: (1) utilizing projections 

of PM2.5 air quality1 and estimating the change in the spatial distribution of the ambient air 

quality; (2) determining the subsequent change in population-level exposure; (3) calculating 

health impacts by applying concentration-response relationships drawn from the 

epidemiological literature (Hubbell et al., 2009) to this change in population exposure.

A typical health impact function might look as follows:

∆y = yo ∙ �eβ∙∆x − 1� ∙ Pop (5-1)

where y0 is the baseline incidence rate for the health endpoint being quantified (for example, a 

health impact function quantifying changes in mortality would use the baseline, or background, 

mortality rate for the given population of interest); Pop is the population affected by the 

change in air quality; ∆x is the change in air quality; and β is the effect coefficient drawn from 

the epidemiological study. Figure 5-1 provides a simplified overview of this approach.

 1 Projections of ambient PM2.5 concentrations for this analysis were generated using the Community Multiscale Air 

Quality model (CMAQ). See Chapter 3 of this RIA for more information on the air quality modeling.
 

5-10

Figure 5-1. Illustration of BenMAP Approach

5.4.2 Economic Valuation of Health Impacts

After quantifying the change in adverse health impacts, the final step is to estimate the 

economic value of these avoided impacts. The appropriate economic value for a change in a 

health effect depends on whether the health effect is viewed ex ante (before the effect has

occurred) or ex post (after the effect has occurred). Reductions in ambient concentrations of air 

pollution generally lower the risk of future adverse health effects by a small amount for a large 

population. The appropriate economic measure is therefore ex ante Willingness to Pay (WTP) 

for changes in risk. However, epidemiological studies generally provide estimates of the relative 

risks of a particular health effect avoided due to a reduction in air pollution. A convenient way 

to use these data in a consistent framework is to convert probabilities to units of avoided 

statistical incidences. This measure is calculated by dividing individual WTP for a risk reduction 

by the related observed change in risk. For example, suppose a measure is able to reduce the 

risk of premature mortality from 2 in 10,000 to 1 in 10,000 (a reduction of 1 in 10,000). If 

individual WTP for this risk reduction is $100, then the WTP for an avoided statistical premature 

mortality amounts to $1 million ($100/0.0001 change in risk). Using this approach, the size of 
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the affected population is automatically taken into account by the number of incidences 

predicted by epidemiological studies applied to the relevant population. The same type of 

calculation can produce values for statistical incidences of other health endpoints.

For some health effects, such as hospital admissions, WTP estimates are generally not 

available. In these cases, we use the cost of treating or mitigating the effect. For example, for 

the valuation of hospital admissions we use the avoided medical costs as an estimate of the 

value of avoiding the health effects causing the admission. These cost-of-illness (COI) estimates 

generally (although not in every case) understate the true value of reductions in risk of a health 

effect. They tend to reflect the direct expenditures related to treatment but not the value of 

avoided pain and suffering from the health effect.

We use the BenMAP model version 4.0.52 (Abt Associates, 2010) to estimate the health 

impacts and monetized health benefits for the proposed standard. Figure 5-2 shows the data 

inputs and outputs for the BenMAP model.

Figure 5-2. Data Inputs and Outputs for the BenMAP Model

Modeled Baseline 

and Post-Control 

Ambient PM2.5

PM2.5 Health 

Functions

Economic 

Valuation 

Functions

2020 Population 

Projections

PM2.5 Incremental Air 

Quality Change

PM2.5-Related Health 

Impacts

Woods & Poole 

Population 

Projections

Background 

Incidence and 

Prevalence Rates

Monetized PM2.5-

related Benefits

Blue identifies a user-selected input within the BenMAP model

Green identifies a data input generated outside of the BenMAP 

Census 

Population Data
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5.5 Uncertainty Characterization

In any complex analysis using estimated parameters and inputs from numerous models, 

there are likely to be many sources of uncertainty. This analysis is no exception. As outlined 

both in this and preceding chapters, this analysis includes many data sources as inputs, 

including emission inventories, air quality data from models (with their associated parameters 

and inputs), population data, population estimates, health effect estimates from epidemiology 

studies, economic data for monetizing benefits, and assumptions regarding the future state of 

the world (i.e., regulations, technology, and human behavior). Each of these inputs may be 

uncertain and would affect the benefits estimate. When the uncertainties from each stage of 

the analysis are compounded, even small uncertainties can have large effects on the total 

quantified benefits.

After reviewing EPA’s approach, the National Research Council (NRC) (2002, 2008), 

which is part of the National Academies of Science, concluded that EPA’s general methodology 

for calculating the benefits of reducing air pollution is reasonable and informative in spite of 

inherent uncertainties. The NRC also highlighted the need to conduct rigorous quantitative 

analyses of uncertainty and to present benefits estimates to decision makers in ways that foster 

an appropriate appreciation of their inherent uncertainty. Since the publication of these 

reports, EPA has continued work to improve the characterization of uncertainty in both health 

incidence and benefits estimates. In response to these recommendations, we have expanded 

our previous analyses to incorporate additional quantitative and qualitative characterizations of 

uncertainty.

To characterize uncertainty and variability, we follow an approach that combines 

elements from two recent EPA analyses (U.S. EPA, 2010b; U.S. EPA, 2011a), and uses a tiered 

approach developed by the World Health Organization (WHO) for characterizing uncertainty 

(WHO, 2008). We present this tiered assessment as well as an assessment of the potential 

impact and magnitude of each aspect of uncertainty In Appendix 5c. While data limitations 

prevent us from treating each source of uncertainty quantitatively and from reaching a fullprobabilistic simulation of our results, we were able to consider the influence of uncertainty in 

the risk coefficients and economic valuation functions by incorporating six quantitative analyses

described in more detail below:

1. A Monte Carlo assessment that accounts for random sampling error and between 

study variability in the epidemiological and economic valuation studies;
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2. A concentration benchmark assessment that characterizes the distribution of 

avoided PM2.5-related deaths relative to specific concentrations in the long-term 

epidemiological studies used to estimate PM2.5-related mortality;

3. The quantification of PM-related mortality using alternative PM2.5 mortality effect 

estimates drawn from two long-term cohort studies and an expert elicitation;

4. Sensitivity analyses of several aspects of PM-related benefits;

5. Distributional analyses of PM2.5-related benefits by location, race, income, and 

education; and

6. An analysis of the influence of various parameters on total monetized benefits.

5.5.1 Monte Carlo Assessment

Similar to other recent RIAs, we used Monte Carlo methods for characterizing random 

sampling error associated with the concentration response functions from epidemiological 

studies and random effects modeling to characterize both sampling error and variability across 

the economic valuation functions. The Monte Carlo simulation in the BenMAP software 

randomly samples from a distribution of incidence and valuation estimates to characterize the 

effects of uncertainty on output variables. Specifically, we used Monte Carlo methods to 

generate confidence intervals around the estimated health impact and monetized benefits. The 

reported standard errors in the epidemiological studies determined the distributions for 

individual effect estimates for endpoints estimated using a single study. For endpoints 

estimated using a pooled estimate of multiple studies, the confidence intervals reflect both the 

standard errors and the variance across studies. The confidence intervals around the monetized 

benefits incorporate the epidemiology standard errors as well as the distribution of the 

valuation function. These confidence intervals do not reflect other sources of uncertainty 

inherent within the estimates, such as baseline incidence rates, populations exposed and 

transferability of the effect estimate to diverse locations. As a result, the reported confidence 

intervals and range of estimates give an incomplete picture about the overall uncertainty in the 

benefits estimates.

5.5.2 Concentration Benchmark Analysis for PM2.5

We include a concentration benchmark assessment, which identifies the baseline (i.e.,

pre-rule) annual mean PM2.5 levels at which populations are exposed and specific 

concentrations in the two long-term cohort studies we use to quantify mortality impacts. This 

analysis characterize avoided PM2.5-related deaths relative the the 10th and 25th percentiles of 
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the the air quality data used the Krewski et al. (2009) study as well as the lowest measured level 

(LML) of the Krewski et al. (2009) and Laden et al. (2006) studies.

5.5.3 Alternative Concentration-Response Functions for PM2.5 –Related Mortality

We assign the greatest economic value to the reduction in PM2.5 relatedmortality risk. 

Therefore, it is particularly important to attempt to characterize the uncertainties associated 

with reductions in premature mortality. To better understand the concentration-response 

relationship between PM2.5 exposure and premature mortality, EPA conducted an expert 

elicitation in 2006 (Roman et al., 2008; IEc, 2006).2 In general, the results of the expert 

elicitation support the conclusion that the benefits of PM2.5 control are very likely to be 

substantial.

Alternative concentration-response functions are useful for assessing uncertainty 

beyond random statistical error, including uncertainty in the functional form of the model or 

alternative study design. Thus, we include the expert elicitation results as well as standard 

errors approaches to provide insights into the likelihood of different outcomes and about the 

state of knowledge regarding the benefits estimates. In this analysis, we present the results 

derived from the expert elicitation as indicative of the uncertainty associated with a major 

component of the health impact functions, and we provide the independent estimates derived 

from each of the twelve experts to better characterize the degree of variability in the expert 

responses.

In previous RIAs, EPA presented benefits estimates using concentration response 

functions derived from the PM2.5 Expert Elicitation (Roman et al., 2008) as a range from the 

lowest expert value (Expert K) to the highest expert value (Expert E). However, this approach 

did not indicate the agency’s judgment on what the best estimate of PM2.5 benefits may be, and 

EPA’s independent Science Advisory Board raised concerns about this presentation (U.S. EPASAB, 2008). Therefore, we began to present the cohort-based studies (Krewski et al., 2009; 

Laden et al., 2006) as our core estimates in the proposal RIA for the Portland Cement NESHAP 

(U.S. EPA, 2009a). Using alternate relationships between PM2.5 and premature mortality 

supplied by experts, higher and lower benefits estimates are plausible, but most of the expertbased estimates of the mean PM2.5 effect on mortality fall between the two epidemiologybased estimates (Roman et al., 2008). In addition to these studies, we have included a 

discussion or other recent multi-state cohort studies conducted in North America, but we have 

 2 Expert elicitation is a formal, highly structured and well documented process whereby expert judgments, usually 

of multiple experts, are obtained (Ayyub, 2002).
5-15

not estimated benefits using the effect coefficients from these studies. Please note that the

benefits estimates results presented are not the direct results from the studies or expert 

elicitation; rather, the estimates are based in part on the effect coefficients provided in those 

studies or by experts.

Even these multiple characterizations with confidence intervals omit the contribution to 

overall uncertainty from uncertainty in air quality changes, baseline incidence rates, and 

populations exposed. Furthermore, the approach presented here does not yet include methods 

for addressing correlation between input parameters and the identification of reasonable upper 

and lower bounds for input distributions characterizing uncertainty in additional model 

elements. As a result, the reported confidence intervals and range of estimates give an 

incomplete picture about the overall uncertainty in the estimates. This information should be 

interpreted within the context of the larger uncertainty surrounding the entire analysis.

5.5.4 Sensitivity Analyses

For some aspects of uncertainty, we have sufficient data to conduct sensitivity analyses. 

In this analysis, we performed four such analyses for the proposed standard level. In particular, 

we:

1. Assessed the sensitivity of the economic value of reductions in the risk of PM2.5-

related death according to differing assumptions regarding the lag between PM2.5

exposure and premature death. The timing of such premature deaths affects the 

magnitude of the discounted PM2.5-related mortality benefits. In this sensitivity 

assessment, we consider 6 alternative cessation lags.

2. Characterized the sensitivity of the economic value of the health endpoints valued 

using willingness-to-pay estimates to a higher and a lower assumption regarding 

income elasticity. As we discuss below, economic theory argues that individual 

willingness to pay increases as personal income grows. The relationship between 

growth in personal income and willingness-to-pay to reduce mortality and morbidity 

risk is characterized by the income growth factor.

3. Summarized the avoided cases of certain health endpoints for which we either 

lacked an appropriate economic value (cardiovascular hospital admissions and 

stroke) or in which we no longer had sufficient confidence to retain in our primary 

benefits estimate (chronic bronchitis).

4. Compared the valuation of hospitalizations and work loss days using the 2000 AHRQ 

database to the 2007 database.
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5.5.5 Distributional Assessment

In the Appendix to this chapter, we characterize the distribution of PM2.5-related 

benefits based on the geographic distribution of race and education in areas where the selected 

control strategies would reduce PM2.5 concentrations. In this assessment, we aim to answer two 

key questions:

1. What is the estimated distribution of PM2.5-related mortality risk based on the race

and education characteristics of the population living within areas projected to 

exceed alternative combinations of primary PM2.5 standards?

2. How would air quality improvements within these counties change the distribution 

of risk among populations of different races and educational attainment?3

This assessment is generally consistent with the distributional assessments performed in 

support of the CSAPR (EPA, 2011c) and the MATS (EPA, 2011c), with one key difference. The 

environmental justice analyses accompanying the CSAPR and MATS RIAs applied CMAQmodeled PM2.5 predictions that represent the change in air quality after the implementation of 

each rule. By contrast, this RIA aims to illustrate the potential benefits and costs of attaining 

alternative primary PM2.5 standards; the states will ultimately implement attainment strategies, 

which may differ greatly from the least-cost strategy EPA modeled here. Alternative attainment 

strategies—particularly those that maximize benefits to human health and provide a more 

equitable distribution of risk—are also available to the states, though not modeled here (Fann 

et al., 2012b).

5.5.6 Influence Analysis—Quantitative Assessment of Uncertainty

In the past few years, EPA has initiated several projects to improve the characterization 

of uncertainty for benefits analysis. In particular, EPA recently completed the first phase of a 

quantitative uncertainty analysis of benefits, hereafter referred to as the “Influence Analysis”

(Mansfield et al., 2009). The Influence Analysis diagramed the uncertain components of each 

step within the benefits analysis process, identified plausible ranges for a sensitivity analysis, 

and assessed the sensitivity to total benefits to changes in each component. While this analysis 

does not quite fulfill the goal of a full probabilistic assessment, it accomplished the necessary 

first steps and identified the challenges to accomplishing that goal. Below are some of the 

preliminary observations from the first phase of the project.

 3 In this analysis we assess the change in risk among populations of different race and educational attainment. As 

we discuss further in the methodology, we consider this last variable because of the availability of educationmodified PM2.5 mortality risk estimates.
5-17

 The components that contribute the most to uncertainty of the monetized benefits 

and mortality incidence (in order of importance) are the value-of-a-statistical-life 

(VSL), the concentration-response (C-R) function for mortality, and change in PM2.5 

concentration.

 The components that contribute the least to uncertainty of the monetized benefits 

and mortality incidence are population, morbidity valuation, and income elasticity.

 The choice of a C-R function for mortality affects the mortality incidence and 

monetized benefits more than other sources of uncertainty within each C-R 

function.

 Alternative cessation lag structures for mortality have a moderate effect on the 

monetized benefits.

 Because the health impact function is essentially linear, the key components show 

the same sensitivity across all mortality C-R functions even if the midpoints differ 

significantly from one expert to another.

5.5.7 Qualitative Assessment of Uncertainty and Other Analysis Limitations

Although we strive to incorporate as many quantitative assessments of uncertainty as 

possible, there are several aspects we are only able to address qualitatively. These aspects are 

important factors to consider when evaluating the relative benefits of the attainment strategies 

for each of the alternative standards:

The total monetized benefits presented in this chapter are based on our interpretation 

of the best available scientific literature and methods and supported by EPA’s independent 

Science Advisory Board (Health Effects Subcommittee) (SAB-HES) (U.S. EPA- SAB, 2010a) and 

the National Academies of Science (NAS) (NRC, 2002). The benefits estimates are subject to a 

number of assumptions and uncertainties. For example, the key assumptions underlying the 

estimates for premature mortality, which account for over 98% of the total monetized benefits

in this analysis, include the following:

1. We assume that all fine particles, regardless of their chemical composition, are 

equally potent in causing premature mortality. This is an important assumption, 

because PM2.5 varies considerably in composition across sources, but the scientific 

evidence is not yet sufficient to allow differentiation of effect estimates by particle 

type. The PM ISA, which was twice reviewed by CASAC, concluded that “many 

constituents of PM2.5 can be linked with multiple health effects, and the evidence is 

not yet sufficient to allow differentiation of those constituents or sources that are 

more closely related to specific outcomes” (U.S. EPA, 2009b).
5-18

2. We assume that the health impact function for fine particles is log-linear down to 

the lowest air quality levels modeled in this analysis. Thus, the estimates include 

health benefits from reducing fine particles in areas with varied concentrations of 

PM2.5, including both regions that are in attainment with the fine particle standard 

and those that do not meet the standard down to the lowest modeled 

concentrations.

3. To characterize the uncertainty in the relationship between PM2.5 and premature 

mortality (which account for over 98% of total monetized benefits in this analysis), 

we include a set of twelve estimates based on results of the expert elicitation study 

in addition to our core estimates. Even these multiple characterizations omit the 

uncertainty in air quality estimates, baseline incidence rates, populations exposed 

and transferability of the effect estimate to diverse locations. As a result, the 

reported confidence intervals and range of estimates give an incomplete picture 

about the overall uncertainty in the PM2.5 estimates. This information should be 

interpreted within the context of the larger uncertainty surrounding the entire 

analysis.

As previously described, we strive to monetize as many of the benefits anticipated from 

the alternative standards as possible given data and resource limitations, but the monetized 

benefits estimated in this RIA inevitably only reflect a portion of the benefits. Specifically, only 

certain benefits attributable to the health impacts associated with exposure to ambient fine 

particles have been monetized in this analysis. Data and methodological limitations prevented 

EPA from quantifying or monetizing the benefits from several important health benefit 

categories in this RIA, including benefits from reducing ozone exposure, NO2 exposure, SO2

exposure, and methylmercury exposure (see section 5.6.5 for more information). If we could 

fully monetize all of the benefit categories, the total monetized benefits would exceed the costs 

by an even greater margin than we currently estimate.

To more fully address all these uncertainties including those we cannot quantify, we 

apply a four-tiered approach using the WHO uncertainty framework (WHO, 2008), which 

provides a means for systematically linking the characterization of uncertainty to the 

sophistication of the underlying risk assessment. EPA has applied similar approaches in analyses 

(U.S. EPA, 2010b, 2011a). Using this framework, we summarize the key uncertainties in the 

health benefits analysis, including our assessment of the direction of potential bias, magnitude 

of impact on the monetized benefits, degree of confidence in our analytical approach, and our 

ability to assess the source of uncertainty. More information on this approach and the 

uncertainty characterization are available in Appendix 5C. Because this approach reflects a new 
5-19

application for regulatory benefits analysis, we request comments on this general approach to 

characterizing uncertainty as well as the specific uncertainty assessments.

5.6 Benefits Analysis Data Inputs

In Figure 5-2, we summarized the key data inputs to the health impact and economic 

valuation estimate. Below we summarize the data sources for each of these inputs, including 

demographic projections, incidence and prevalence rates, effect coefficients, and economic 

valuation. We indicate where we have updated key data inputs since the benefits analysis

conducted for the MATS (U.S. EPA, 2011d).

5.6.1 Demographic Data

Quantified and monetized human health impacts depend on the demographic 

characteristics of the population, including age, location, and income. We use projections based 

on economic forecasting models developed by Woods and Poole, Inc. (Woods and Poole, 2007). 

The Woods and Poole (WP) database contains county-level projections of population by age, 

sex, and race out to 2030. Projections in each county are determined simultaneously with every 

other county in the United States to take into account patterns of economic growth and 

migration. The sum of growth in county-level populations is constrained to equal a previously 

determined national population growth, based on Bureau of Census estimates (Hollman et al., 

2000). According to WP, linking county-level growth projections together and constraining to a 

national-level total growth avoids potential errors introduced by forecasting each county 

independently. County projections are developed in a four-stage process:

• First, national-level variables such as income, employment, and populations are 

forecasted.

• Second, employment projections are made for 179 economic areas defined by 

the Bureau of Economic Analysis (U.S. BEA, 2004), using an “export-base”

approach, which relies on linking industrial-sector production of non-locally 

consumed production items, such as outputs from mining, agriculture, and 

manufacturing with the national economy. The export-based approach requires 

estimation of demand equations or calculation of historical growth rates for 

output and employment by sector.

• Third, population is projected for each economic area based on net migration 

rates derived from employment opportunities and following a cohortcomponent method based on fertility and mortality in each area.

• Fourth, employment and population projections are repeated for counties, using 

the economic region totals as bounds. The age, sex, and race distributions for 
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each region or county are determined by aging the population by single year of 

age by sex and race for each year through 2020 based on historical rates of 

mortality, fertility, and migration.

5.6.2 Baseline Incidence and Prevalence Estimates

Epidemiological studies of the association between pollution levels and adverse health 

effects generally provide a direct estimate of the relationship of air quality changes to the 

relative risk of a health effect, rather than estimating the absolute number of avoided cases. For 

example, a typical result might be that a 10 μg/m3 decrease in daily PM2.5 levels might be 

associated with a decrease in hospital admissions of 3%. The baseline incidence of the health 

effect is necessary to convert this relative change into a number of cases. A baseline incidence 

rate is the estimate of the number of cases of the health effect per year in the assessment 

location, as it corresponds to baseline pollutant levels in that location. To derive the total 

baseline incidence per year, this rate must be multiplied by the corresponding population 

number. For example, if the baseline incidence rate is the number of cases per year per million 

people, that number must be multiplied by the millions of people in the total population.

Table 5-3 summarizes the sources of baseline incidence rates and provides average 

incidence rates for the endpoints included in the analysis. For both baseline incidence and 

prevalence data, we used age-specific rates where available. We applied concentrationresponse functions to individual age groups and then summed over the relevant age range to 

provide an estimate of total population benefits. In most cases, we used a single national 

incidence rate, due to a lack of more spatially disaggregated data. Whenever possible, the 

national rates used are national averages, because these data are most applicable to a national 

assessment of benefits. For some studies, however, the only available incidence information 

comes from the studies themselves; in these cases, incidence in the study population is 

assumed to represent typical incidence at the national level. County, state and regional 

incidence rates are available for hospital admissions, and county-level data are available for 

premature mortality. We have projected mortality rates such that future mortality rates are 

consistent with our projections of population growth (Abt Associates, 2011).

The baseline incidence rates for hospital admissions and emergency department visits 

reflect the revised rates first applied in the CSAPR RIA (U.S. EPA, 2011c). In addition, we have 

also revised the baseline incidence rates for acute myocardial infarction. These revised rates are 

more recent (AHRQ, 2007), which provides a better representation of the rates at which 

populations of different ages, and in different locations, visit the hospital and emergency 

department for air pollution-related illnesses. Also, the new baseline incidence rates are more 
5-21

spatially refined. For many locations within the U.S., these data are resolved at the county- or 

state-level, providing a better characterization of the geographic distribution of hospital and 

emergency department visits than the previous national rates. Lastly, these rates reflect 

unscheduled hospital admissions only, which represents a conservative assumption that most 

air pollution-related visits are likely to be unscheduled. If air pollution-related hospital 

admissions are scheduled, this assumption would underestimate these benefits.
5-22

Table 5-3. Baseline Incidence Rates and Population Prevalence Rates for Use in Impact 

Functions, General Population

Endpoint Parameter

Rates

Value Source

Mortality Daily or annual mortality rate 

projected to 2015a

Age-, cause-, and countyspecific rateCDC WONDER (2004–2006)

U.S. Census bureau, 2000

Hospitalizations Daily hospitalization rate Age-, region-, state-, countyand cause-specific rate2007 HCUP data files b

ER Visits Daily ER visit rate for asthma and 

cardiovascular events

Age-, region-, state-, countyand cause-specific rate2007 HCUP data files b

Cerebrovascular 

events

Incidence of new cerebrovascular 

events among populations 50–79

0.001575I Table 3 of Miller et al. (2007)

Chronic Bronchitis d Annual prevalence rate per person

• Aged 18–44

• Aged 45–64

• Aged 65 and older

• 0.0315

• 0.0549

• 0.0563

American Lung Association 

(2010a, Table 4). 

Annual incidence rate per person 0.00378 Abbey et al. (1993, Table 3)

Nonfatal Myocardial 

Infarction (heart 

attacks)

Daily nonfatal myocardial infarction 

incidence rate per person, 18+

Age-, region-, state-, and 

county-specific rate

2007 HCUP data files b

;

adjusted by 0.93 for 

probability of surviving after 

28 days (Rosamond et al., 

1999)

Asthma Exacerbations Incidence among asthmatic AfricanAmerican children

• daily wheeze

• daily cough

• daily dyspnea

• 0.076

• 0.067

• 0.037

Ostro et al. (2001) 

Acute Bronchitis Annual bronchitis incidence rate, 

children

0.043 American Lung Association 

(2002c, Table 11)

Lower Respiratory 

Symptoms

Daily lower respiratory symptom 

incidence among children c

0.0012 Schwartz et al. (1994, Table 

2)

Upper Respiratory 

Symptoms

Daily upper respiratory symptom 

incidence among asthmatic children

0.3419 Pope et al. (1991, Table 2)

Work Loss Days Daily WLD incidence rate per person 

(18–65)

• Aged 18–24

• Aged 25–44

• Aged 45–64

• 0.00540

• 0.00678

• 0.00492

1996 HIS (Adams, 

Hendershot, and Marano, 

1999, Table 41); U.S. Census 

Bureau (2000)

School Loss Days Rate per person per year, assuming 

180 school days per year

9.9 National Center for 

Education Statistics (1996) 

and 1996 HIS (Adams et al., 

1999, Table 47); 

(continued)
5-23

Table 5-3. Baseline Incidence Rates and Population Prevalence Rates for Use in Impact 

Functions, General Population (continued)

Endpoint Parameter

Rates

Value Source

Minor RestrictedActivity DaysDaily MRAD incidence rate per 

person

0.02137 Ostro and Rothschild (1989, 

p. 243)

a Mortality rates are only available at 5-year increments.

b Healthcare Cost and Utilization Program (HCUP) database contains individual level, state and regional-level 

hospital and emergency department discharges for a variety of ICD codes (AHRQ, 2007).

c Lower respiratory symptoms are defined as two or more of the following: cough, chest pain, phlegm, and 

wheeze.

d Assessed in sensitivity analysis only. The rate numbers may be slightly different from those in Table 4 because 

we received more current estimates from ALA.

For the set of endpoints affecting the asthmatic population, in addition to baseline 

incidence rates, prevalence rates of asthma in the population are needed to define the 

applicable population. Table 5-4 lists the prevalence rates used to determine the applicable 

population for asthma symptoms. Note that these reflect current asthma prevalence and 

assume no change in prevalence rates in future years. We updated these rates in the CSAPR RIA

(U.S. EPA, 2011c).

Table 5-4. Asthma Prevalence Rates 

Population Group

Asthma Prevalence Rates

Value Source

All Ages 0.0780 American Lung Association (2010b, Table 7)

< 18 0.0941

5–17 0.1070

18–44 0.0719

45–64 0.0745

65+ 0.0716

African American, 5–17 0.1776 American Lung Association (2010b, Table 9)

African American, <18 0.1553 American Lung Associationa

a Calculated by ALA for U.S. EPA, based on NHIS data (CDC, 2008).
5-24

5.6.3 Effect Coefficients

The first step in selecting effect coefficients is to identify the health endpoints to be 

quantified. We base our selection of health endpoints on consistency with EPA’s Integrated 

Science Assessments (which replace previous Criteria Documents), with input and advice from 

the EPA Science Advisory Board—Health Effects Subcommittee (SAB-HES), a scientific review 

panel specifically established to provide advice on the use of the scientific literature in 

developing benefits analyses for air pollution regulations. In general, we follow a weight of 

evidence approach, based on the biological plausibility of effects, availability of concentrationresponse functions from well conducted peer-reviewed epidemiological studies, cohesiveness 

of results across studies, and a focus on endpoints reflecting public health impacts (like hospital 

admissions) rather than physiological responses (such as changes in clinical measures like 

Forced Expiratory Volume (FEV1)).

There are several types of data that can support the determination of types and 

magnitude of health effects associated with air pollution exposures. These sources of data 

include toxicological studies (including animal and cellular studies), human clinical trials, and 

observational epidemiology studies. All of these data sources provide important contributions 

to the weight of evidence surrounding a particular health impact. However, only epidemiology 

studies provide direct concentration-response relationships that can be used to evaluate 

population-level impacts of reductions in ambient pollution levels in a health impact 

assessment.

For the data-derived estimates, we relied on the published scientific literature to 

ascertain the relationship between PM2.5 and adverse human health effects. We evaluated 

epidemiological studies using the selection criteria summarized in Table 5-5. These criteria 

include consideration of whether the study was peer-reviewed, the match between the 

pollutant studied and the pollutant of interest, the study design and location, and 

characteristics of the study population, among other considerations. In general, the use of 

concentration-response functions from more than a single study can provide a more 

representative distribution of the effect estimate. However, there are often differences 

between studies examining the same endpoint, making it difficult to pool the results in a 

consistent manner. For example, studies may examine different pollutants or different age 

groups. For this reason, we consider very carefully the set of studies available examining each 

endpoint and select a consistent subset that provides a good balance of population coverage 

and match with the pollutant of interest. In many cases, either because of a lack of multiple 
5-25

studies, consistency problems, or clear superiority in the quality or comprehensiveness of one 

study over others, a single published study is selected as the basis of the effect estimate.

When several effect estimates for a pollutant and a given health endpoint have been 

selected, they are quantitatively combined or pooled to derive a more robust estimate of the 

relationship. The BenMAP Manual Technical Appendices provides details of the procedures 

used to combine multiple impact functions (Abt Associates, 2011). In general, we used fixed or 

random effects models to pool estimates from different single city studies of the same 

endpoint. Fixed effects pooling simply weights each study’s estimate by the inverse variance, 

giving more weight to studies with greater statistical power (lower variance). Random effects 

pooling accounts for both within-study variance and between-study variability, due, for

example, to differences in population susceptibility. We used the fixed effects model as our null 

hypothesis and then determined whether the data suggest that we should reject this null 

hypothesis, in which case we would use the random effects model. Pooled impact functions are 

used to estimate hospital admissions and asthma exacerbations. When combining evidence 

across multi-city studies (e.g., cardiovascular hospital admission studies), we use equal weights 

pooling. The effect estimates drawn from each multi-city study are themselves pooled across a 

large number of urban areas. For this reason, we elected to give each study an equal weight 

rather than weighting by the inverse of the variance reported in each study. For more details on 

methods used to pool incidence estimates, see the BenMAP Manual Appendices (Abt 

Associates, 2011).

Effect estimates selected for a given health endpoint were applied consistently across all 

locations nationwide. This applies to both impact functions defined by a single effect estimate 

and those defined by a pooling of multiple effect estimates. Although the effect estimate may, 

in fact, vary from one location to another (e.g., because of differences in population 

susceptibilities or differences in the composition of PM), location-specific effect estimates are 

generally not available.

The specific studies from which effect estimates for the main analysis are drawn are 

included in Table 5-6. We highlight in blue those studies that have been added since the 

benefits analysis conducted for the MATS RIA (U.S. EPA, 2011d) and incorporated into the 

central benefits estimate. In all cases where effect estimates are drawn directly from 

epidemiological studies, standard errors are used as a partial representation of the uncertainty 

in the size of the effect estimate. Table 5-7 summarizes those health endpoints and studies we 

have included as in sensitivity analyses.
5-26

Table 5-5. Criteria Used When Selecting C-R Functions

Consideration Comments

Peer-Reviewed 

Research

Peer-reviewed research is preferred to research that has not undergone the peer-review 

process.

Study Type Among studies that consider chronic exposure (e.g., over a year or longer), prospective 

cohort studies are preferred over ecological studies because they control for important 

individual-level confounding variables that cannot be controlled for in ecological studies. 

Study Period Studies examining a relatively longer period of time (and therefore having more data) are 

preferred, because they have greater statistical power to detect effects. Studies that are 

more recent are also preferred because of possible changes in pollution mixes, medical 

care, and lifestyle over time. However, when there are only a few studies available, 

studies from all years will be included.

Population Attributes The most technically appropriate measures of benefits would be based on impact 

functions that cover the entire sensitive population but allow for heterogeneity across 

age or other relevant demographic factors. In the absence of effect estimates specific to 

age, sex, preexisting condition status, or other relevant factors, it may be appropriate to 

select effect estimates that cover the broadest population to match with the desired 

outcome of the analysis, which is total national-level health impacts. When available, 

multi-city studies are preferred to single city studies because they provide a more 

generalizable representation of the concentration-response function.

Study Size Studies examining a relatively large sample are preferred because they generally have 

more power to detect small magnitude effects. A large sample can be obtained in several 

ways, including through a large population or through repeated observations on a 

smaller population (e.g., through a symptom diary recorded for a panel of asthmatic 

children).

Study Location U.S. studies are more desirable than non-U.S. studies because of potential differences in 

pollution characteristics, exposure patterns, medical care system, population behavior, 

and lifestyle.

Pollutants Included in 

Model

When modeling the effects of ozone and PM (or other pollutant combinations) jointly, it 

is important to use properly specified impact functions that include both pollutants. 

Using single-pollutant models in cases where both pollutants are expected to affect a 

health outcome can lead to double-counting when pollutants are correlated.

Measure of PM For this analysis, impact functions based on PM2.5 are preferred to PM10 because of the 

focus on reducing emissions of PM2.5 precursors, and because air quality modeling was 

conducted for this size fraction of PM. Where PM2.5 functions are not available, PM10

functions are used as surrogates, recognizing that there will be potential downward 

(upward) biases if the fine fraction of PM10 is more (less) toxic than the coarse fraction. 

Economically Valuable 

Health Effects

Some health effects, such as forced expiratory volume and other technical 

measurements of lung function, are difficult to value in monetary terms. These health 

effects are not quantified in this analysis.

Non-overlapping 

Endpoints

Although the benefits associated with each individual health endpoint may be analyzed 

separately, care must be exercised in selecting health endpoints to include in the overall 

benefits analysis because of the possibility of double-counting of benefits. 

(continued)
5-27

Table 5-6. Health Endpoints and Epidemiological Studies Used to Quantify Health Impacts 

in the Main Analysisa

Endpoint Study Study Population

Risk Estimate

(95th Percentile Confidence 

Interval)a

Premature Mortality

Premature mortality—

cohort study, all-cause

Krewski et al. (2009) >29 years

>24 years

RR = 1.06 (1.04 – 1.06) per 

10 μg/m3

Laden et al. (2006) RR = 1.16 (1.07 – 1.26) per 

10 μg/m3

Premature mortality, 

total exposures

PM2.5 Expert Elicitation (Roman et al., 2008) >24 years Varies by expert

Premature mortality—

all-cause

Woodruff et al. (1997) Infant (<1 year) OR = 1.04 (1.02 – 1.07) per 

10 μg/m3

Chronic Illness

Nonfatal heart attacks Peters et al. (2001) Adults (>18 years) OR = 1.62 (1.13 – 2.34) per 

20 μg/m3

Pooled estimate:

Pope et al. (2006) β = 0.00481 (0.00199)

Sullivan et al. (2005) β = 0.00198 (0.00224)

Zanobetti et al. (2009) β = 0.00225 (0.000591)

Zanobetti and Schwartz (2006) β = 0.0053 (0.00221)

Hospital Admissions 

Respiratory Zanobetti et al. (2009)—ICD 460-519 (All 

respiratory)

>64 years β=0.00207 (0.00446)

Moolgavkar (2000)—ICD 490–496 (Chronic 

lung disease)

18–64 years 1.02 (1.01—1.03) per 

36 μg/m3

Babin et al. (2007)—ICD 493 (asthma) <19 β=0.002 (0.004337)

Cardiovascular Pooled estimate:

Zanobetti et al. (2009)—ICD 390-459 (all 

cardiovascular)

>64 years

β=0.00189 (0.000283)

Peng et al. (2009)—ICD 426-427; 428; 430-

438; 410-414; 429; 440-449 (Cardio-, 

cerebro- and peripheral vascular 

disease)

β=0.00068

(0.000214)

Peng et al. (2008)—ICD 426-427; 428; 430-

438; 410-414; 429; 440-449 (Cardio-, 

cerebro- and peripheral vascular 

disease)

β=0.00071

(0.00013)

Bell et al. (2008)—ICD 426-427; 428; 430-

438; 410-414; 429; 440-449 (Cardio-, 

cerebro- and peripheral vascular 

disease)

β=0.0008

(0.000107)

Moolgavkar (2000)—ICD 390–429 (all 

cardiovascular)

20–64 years RR=1.04 (t statistic: 4.1) per 

10 μg/m3

Asthma-related ER 

visits

Pooled estimate:

Mar et al. (2010)

All ages RR = 1.04 (1.01 – 1.07) per 

7 μg/m3

Slaughter et al. (2005) RR = 1.03 (0.98 – 1.09) per 

10 μg/m3

(continued)
5-28

Endpoint Study Study Population

Risk Estimate

(95th Percentile Confidence 

Interval)a

Other Health Endpoints

Acute bronchitis Dockery et al. (1996) 8–12 years OR = 1.50 (0.91 – 2.47) per 

14.9 μg/m3

Other Health Endpoints (continued)

Asthma exacerbations Pooled estimate:

Ostro et al. (2001) (cough, wheeze and 

shortness of breath) b

6–18 years b

OR = 1.03 (0.98 – 1.07) per 

30 μg/m3

OR = 1.06 (1.01 – 1.11) per 

30 μg/m3

OR = 1.08 (1.00 – 1.17) per 

30 μg/m3

Mar et al. (2004) (cough, shortness of 

breath)

RR = 1.21 (1 – 1.47) per 

10 μg/m3

RR = 1.13 (0.86 – 1.48) per 

10 μg/m3

Work loss days Ostro (1987) 18–65 years β=0.0046 (0.00036)

Acute respiratory 

symptoms

Ostro and Rothschild (1989) (Minor 

restricted activity days) 18–65 years β=0.00220 (0.000658)

a Studies highlighted in blue represent updates incorporated since the RIA for MATS (U.S. EPA, 2011d).

b The original study populations were 8 to 13 for the Ostro et al. (2001) study and 7 to 12 for the Mar et al. (2004) 

study. Based on advice from the Science Advisory Board Health Effects Subcommittee (SAB-HES), we extended 

the applied population to 6 to 18, reflecting the common biological basis for the effect in children in the broader 

age group. See: U.S. EPA-SAB (2004) and NRC (2002).

Table 5-7. Health Endpoints and Epidemiological Studies Used to Quantify Health Impacts 

in the Sensitivity Analysis a

Endpoint Study Study Population

Chronic Illness

Chronic bronchitis Abbey et al. (1995) >26 years

Stroke Miller et al. (2007) 50–79 years

Hospital Admissions 

Cardiovascular ED Visits Metzger et al. (2004) 0–99

Tolbert et al. (2007) 0–99

a Studies highlighted in blue represent updates incorporated since the RIA for MATS (U.S. EPA, 2011d).

5.6.3.1 PM2.5 Premature Mortality Effect Coefficients

Both long- and short-term exposures to ambient levels of PM2.5 air pollution have been 

associated with increased risk of premature mortality. The size of the mortality effect estimates
5-29

from epidemiological studies, the serious nature of the effect itself, and the high monetary 

value ascribed to prolonging life make mortality risk reduction the most significant health 

endpoint quantified in this analysis.

Although a number of uncertainties remain to be addressed by continued research 

(NRC, 2002), a substantial body of published scientific literature documents the correlation 

between elevated PM2.5 concentrations and increased mortality rates (U.S. EPA, 2009b). Timeseries methods have been used to relate short-term (often day-to-day) changes in PM2.5 

concentrations and changes in daily mortality rates up to several days after a period of elevated 

PM2.5 concentrations. Cohort methods have been used to examine the potential relationship 

between community-level PM2.5 exposures over multiple years (i.e., long-term exposures) and

community-level annual mortality rates. Researchers have found statistically significant 

associations between PM2.5 and premature mortality using both types of studies. In general, the 

effect estimates based on the cohort studies are larger than those derived from time-series 

studies. When choosing between using short-term studies or cohort studies for estimating 

mortality benefits, cohort analyses are thought to capture more of the public health impact of 

exposure to air pollution over time because they account for the effects of long-term exposures 

as well as some fraction of short-term exposures (Kunzli et al., 2001; NRC, 2002). This section 

discusses some of the issues surrounding the estimation of PM2.5-related premature mortality. 

To demonstrate the sensitivity of the benefits estimates to various concentration-response 

estimates in the epidemiological literature, we present benefits estimates using several relative 

risk estimates from the largest long-term epidemiological studies as well as a U.S. EPAsponsored expert elicitation (Roman et al. 2008). The epidemiological studies from which these 

estimates are drawn are described below. The PM2.5 expert elicitation and the derivation of 

effect estimates from the expert elicitation results are described in the 2006 PM2.5 NAAQS RIA 

(U.S. EPA, 2006a) and Roman et al. (2008). In the interest of brevity, we do not repeat those 

details here. 4

 4 In summary, the goal of the study was to elicit from a sample of health experts probabilistic distributions 

describing uncertainty in estimates of the reduction in mortality among the adult U.S. population resulting from 

reductions in ambient annual average PM2.5 levels. These distributions were obtained through a formal interview 

protocol using methods designed to elicit subjective expert judgments. These experts were selected through a 

peer-nomination process and included experts in epidemiology, toxicology, and medicine. The elicitation 

interview consisted of a protocol of carefully structured questions, both qualitative and quantitative, about the 

nature of the PM2.5-mortality relationship questions requiring qualitative responses probed experts’ beliefs 

concerning key evidence and critical sources of uncertainty and enabled them to establish a conceptual basis 

supporting their quantitative judgments. The results of the full-scale study consist of twelve individual 

distributions for the coefficient or slope of the C-R function relating changes in annual average PM2.5 exposures 
5-30

Over a dozen epidemiological studies demonstrate significant associations between 

various measures of long-term exposure to PM2.5 and mortality, beginning with Lave and Seskin 

(1977). Most of the published studies found positive (but not always statistically significant) 

associations with available PM indices such as total suspended particles (TSP). However, 

exploration of alternative model specifications sometimes raised questions about causal 

relationships (e.g., Lipfert et al., 1989). These early “ecological cross-sectional” studies (Lave 

and Seskin, 1977; Ozkaynak and Thurston, 1987) were criticized for a number of methodological 

limitations, particularly for inadequate control at the individual level for variables that are 

potentially important in causing mortality, such as wealth, smoking, and diet.

Over the last two decades, several studies using “prospective cohort” designs have been 

published that are consistent with the earlier body of literature. These “prospective cohort”

studies reflect a significant improvement over the earlier work because they include individual 

level information with respect to health status and residence. Two prospective cohort groups, 

often referred to as the Harvard “Six Cities Study” (Dockery et al., 1993; Laden et al., 2006) and 

the “American Cancer Society or ACS study” (Pope et al., 1995; Pope et al., 2002; Pope et al., 

2004; Krewski et al., 2009), provide the most extensive analyses of ambient PM2.5 

concentrations and mortality. These studies have found consistent relationships between fine 

particle indicators and premature mortality across multiple locations in the United States. A 

third major data set comes from the California-based 7th Day Adventist Study (e.g., Abbey 

et al., 1999), which reported associations between long-term PM2.5 exposure and mortality in 

men. Results from this cohort, however, have been inconsistent, the air quality results are not 

geographically representative of most of the United States, and the lifestyle of the population is 

not reflective of much of the U.S. population. Analysis is also available for a cohort of adult 

male veterans diagnosed with hypertension (Lipfert et al., 2000, 2003, 2006). The 

characteristics of this group also differ from the cohorts in the Six Cities and ACS studies as well 

as the 7th Day Adventist study with respect to income, race, health status, and smoking status. 

Unlike previous long-term analyses, this study found some associations between mortality and 

ozone but found inconsistent results for PM indicators.

Given their consistent results and broad geographic coverage, and importance in 

informing the NAAQS development process, the Six Cities and ACS data have been particularly 

important in benefits analyses. The credibility of these two studies is further enhanced by the 

fact that the initial published studies (Pope et al., 1995; Dockery et al., 1993) were subject to 

 

to annual, adult all-cause mortality. The results have not been combined in order to preserve the breadth and

diversity of opinion on the expert panel. Roman et al (2006).
5-31

extensive reexamination and reanalysis by an independent team of scientific experts 

commissioned by the Health Effect Institute (HEI) (Krewski et al., 2000). The final results of the 

reanalysis were then independently peer reviewed by a Special Panel of the HEI Health Review 

Committee. The results of these reanalyses confirmed and expanded the conclusions of the 

original investigators. While the HEI reexamination lends credibility to the original studies, it 

also highlights sensitivities concerning the relative impact of various pollutants, such as SO2, the 

potential role of education in mediating the association between pollution and mortality, and 

the influence of spatial correlation modeling. Further confirmation and extension of the 

findings of the 1993 Six Cities Study and the 1995 ACS study were recently completed using 

more recent air quality and a longer follow-up period for the ACS cohort was published over the 

past several years (Pope et al., 2002, 2004; Laden et al., 2006; Krewski et al., 2009). The follow 

up to the Harvard Six Cities Study both confirmed the effect size from the first analysis and 

provided additional confirmation that reductions in PM2.5 are associated with reductions in the 

risk of premature death. This additional evidence stems from the observed reductions in PM2.5

in each city during the extended follow-up period. Laden et al. (2006) found that mortality rates 

consistently went down at a rate proportional to the observed reductions in PM2.5.

A number of additional analyses have been conducted on the ACS cohort data (Pope 

et al., 2009). These studies have continued to find a strong significant relationship between 

PM2.5 and mortality outcomes and life expectancy. Specifically, much of the recent research has 

suggested a stronger relationship between cardiovascular mortality and lung cancer mortality 

with PM2.5, and a less significant relationship between respiratory-related mortality and PM2.5. 

The extended analyses of the ACS cohort data (Krewski et al., 2009) provides additional 

refinements to the analysis of PM-related mortality by (a) extending the follow-up period by 

2 years to the year 2000, for a total of 18 years; (b) incorporating almost double the number of 

urban areas (c) addressing spatial autocorrelation by incorporating ecological, or communitylevel, co-variates; (d) performing an extensive spatial analysis using land use regression 

modeling in two large urban areas. These enhancements make this analysis well-suited for the 

assessment of mortality risk from long-term PM2.5 exposures for EPA benefits analyses.

In developing and improving the methods for estimating and valuing the potential 

reductions in mortality risk over the years, EPA consulted with the Health Effects Subcommittee 

of the Science Advisory Board (SAB-HES). That panel recommended using long-term prospective 

cohort studies in estimating mortality risk reduction (U.S. EPA-SAB, 1999). This 

recommendation has been confirmed by a report from the National Research Council, which 

stated that “it is essential to use the cohort studies in benefits analysis to capture all important 
5-32

effects from air pollution exposure” (NRC, 2002, p. 108). NRC further notes that “the overall 

effect estimates may be a combination of effects from long-term exposure plus some fraction 

from short-term exposure. The amount of overlap is unknown” (NRC, 2002, p. 108-9). More 

specifically, the SAB recommended emphasis on the ACS study because it includes a much 

larger sample size and longer exposure interval and covers more locations (e.g., 50 cities 

compared to the Six Cities Study) than other studies of its kind. Because of the refinements in 

the extended follow-up analysis, the SAB-HES recommended using the Pope et al. (2002) study 

as the basis for the main mortality estimate for adults and suggests that alternate estimates of 

mortality generated using other cohort and time-series studies could be included as part of the 

sensitivity analysis (U.S. EPA-SAB, 2004a). In 2009, the SAB-HES again reviewed the choice of 

mortality risk coefficients for benefits analysis, concluding that “[t]he Krewski et al. (2009) 

findings, while informative, have not yet undergone the same degree of peer review as have 

the aforementioned studies. Thus, the HES recommends that EPA not use the Krewski et al. 

(2009) findings for generating the Primary Estimate” (U.S. EPA-SAB, 2010a). Since this time, the 

Krewski et al. (2009) has undergone additional peer review, which we believe strengthens the 

support for including this study in this RIA. For example, the PM ISA (U.S. EPA, 2009b), which 

was twice reviewed by Clean Air Scientific Review Committee (CASAC) (U.S. EPA-SAB, 2009b, 

2009c), included this study among the key mortality studies. In addition, the risk assessment 

supporting the PM NAAQS (U.S. EPA, 2010b) utilized risk coefficients drawn from the Krewski et 

al. (2009) study, the most recent reanalysis of the ACS cohort data. The risk assessment cited a 

number of advantages that informed the selection of the Krewski et al. (2009) study as the 

source of the core effect estimates, including the extended period of observation, the rigorous 

examination of model forms and effect estimates, the coverage for ecological variables, and the 

large dataset with over 1.2 million individuals and 156 MSAs (U.S. EPA, 2010b). The CASAC also 

provided extensive peer review of the risk assessment and supported the use of effect 

estimates from this study (U.S. EPA-SAB, 2009a, 2010b,c).

As both the ACS and Six Cities studies have inherent strengths and weaknesses and the 

expert elicitation results encompass within their range the estimates from both the earlier ACS 

Study (Pope et al. 2002) and from the Laden et al. (2006) study, we present benefits estimates 

using RR estimates from the Krewski et al. (2009) (RR=1.06, 95% confidence intervals 1.04–1.08 

per 10μg/m3 increase in PM2.5) and Laden et al. (2006; RR=1.16, 95% confidence intervals 1.07–

1.26 per 10 μg/m3 increase in PM2.5) studies. For the ACS Study (Krewski et al., 2009), we use

the all-cause mortality risk estimate based on the random-effects Cox proportional hazard 

model that incorporates 44 individual and 7 ecological co-variates, consistent with the 

Quantitative Health Risk Assessment for Particulate Matter (U.S. EPA, 2010b). Unlike the Pope 
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et al. (2002) study, Krewski et al. (2009) do not report a risk estimate based on an average 

between the initial monitoring period (1979–1983) and the follow-up period (1999–2000). 

When considering each time period from which we could select risk coefficients, we elected to 

use the estimate based on the 1999–2000 air quality monitoring period because it reflected 

more recent population exposures, a larger number of urban areas (116 vs. 58) and a larger 

population cohort (488,000 vs. 343,000). The relative risk estimate (1.06 per 10μg/m3 increase 

in PM2.5) is identical to the risk estimate drawn from the Pope et al. (2002) study, though the 

confidence interval around the Krewski et al. (2009) risk estimate is tighter.

Presenting results using both ACS and Six Cities is consistent with other recent RIAs (e.g.,

U.S. EPA, 2006a, 2010c, 2011c, 2011d). EPA’s independent SAB also supported using these two 

cohorts for benefits, concluding that “the selection of these cohort studies as the underlying 

basis for PM mortality benefit estimates to be a good choice. These are widely cited, well 

studied and extensively reviewed data sets” (U.S. EPA-SAB, 2010a).

In addition to the ACS and Six Cities cohorts described above, several recent cohort 

studies conducted in North America provide evidence for the relationship between long-term 

exposure to PM2.5 and the risk of premature death. Many of these additional cohort studies are 

described in the PM ISA (U.S. EPA, 2009) (and thus not summarized here). We describe the 

newer multi-state studies below.5,6 Table 5-8 provides the effect estimates from each of these 

cohort studies (new and included in the PM ISA) for all-cause, cardiovascular, cardiopulmonary, 

and ischemic heart disease (IHD) mortality as well as the lowest measured air quality level 

(LML) in the study.

Puett et al. (2009) examined the risk of all-cause mortality and fatal congestive heart 

disease among a cohort of about 66,000 female nurses in 13 northeastern and midwestern

states (i.e., the Nurses’ Health Study cohort) resulting from long-term exposure to PM2.5. 

Consistent with findings from previous cohort studies, the researchers found significant 

associations between long-term PM2.5 exposure and all-cause mortality and fatal coronary heart 

disease. Puett et al. (2011) examined the risk of all-cause and cardiovascular mortality among a 

cohort of 17,000 male health professionals with high socioeconomic status in 13 northeastern 

and midwestern states. The researchers found no association between long-term PM2.5 

 5 It is important to note that these newer studies have not been assessed in the context of an Integrated Science 

Assessment nor gone through review by the SAB. In addition, only the ACS and H6C cohort studies have been 

recommended by the SAB as appropriate for benefits analysis of national rulemakings. 6 In this chapter, we only describe multi-state cohort studies. There are additional cohorts that focus on single 

cities, such as Gan et al. (2012) that we have not included. In Appendix 5B, we provide additional information 

regarding cohort studies in California, which is the only state for which we identified single state cohorts.
5-34

exposure and mortality, concluding that additional research is needed to determine whether 

men with higher socioeconomic status are less susceptible to cardiovascular outcomes 

associated with long-term particle exposure.

Table 5-8. Summary of Effect estimates from Associated With Change in Long-Term 

Exposure to PM2.5 in Recent Cohort Studies in North America

Study Cohort (age)

LML 

(μg/m3

)

Hazard Ratios per 10 μg/m3 Change in PM2.5

(95th percentile confidence intervals)

All Causes Cardiovascular Cardiopulmonary IHD

Pope et al. 

(2002)

ACS

(age >30)

7.5 1.06

(1.02–1.11)

1.12

(1.08–1.15)

1.09

(1.03–1.16)

N/A

Laden et al. 

(2006)

Six Cities

(age > 25)

10 1.16

(1.07–1.26)

1.28

(1.13–1.44)

N/A N/A

Lipfert et al. 

(2006)a

Veterans

(age 39–63)

<14.1 1.15

(1.05–1.25)

N/A N/A N/A

Miller et al. 

(2007)b

WHI

(age 50–79)

3.4 N/A 1.76

(1.25–2.47)

N/A 2.21

(1.17–4.16)

Eftim et al. 

(2008)

Medicare

(age > 65)

6 1.21

(1.15–1.27)

N/A N/A N/A

Zeger et al. 

(2008)c

Medicare 

(age > 65)

<9.8 1.068

(1.049–1.087)

N/A N/A N/A

Krewski et al. 

(2009)d

ACS

(age >30)

5.8 1.06

(1.04–1.08)

N/A 1.13

(1.10–1.16)

1.24

(1.19–1.29)

Puett et al. 

(2009)b

NHS 

(age 30–55)

5.8 1.26

(1.02–1.54)

N/A N/A 2.02

(1.07–3.78)

Crouse et al. 

(2011)d, f

Canadian 

census

1.9 1.06

(1.01–1.10)

N/A N/A N/A

Puett et al.

(2011)

e

Health 

Professionals

(age 40–75)

<14.4 0.86

(0.70–1.00)

1.02

(0.84–1.23)

N/A N/A

Lepeule et al. 

(2012)d

Six Cities

(age > 25)

8 1.14

(1.07–1.22)

1.26

(1.14–1.40)

N/A N/A

a Used traffic proximity as a surrogate of exposure.

b Women only.

c Reflects risks in the Eastern U.S. Risks in the Central U.S. were higher, but the authors found no association in 

the Western U.S.

d Random effects Cox model with individual and ecologic covariates.

e Men with high socioeconomic status only.

f Canadian population.
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Crouse et al. (2012) found elevated risks of non-accidental and ischemic heart disease 

mortality associated with long-term exposure to PM2.5 from the period of 1991 to 2001 among 

a cohort of Canadian adults aged 25 and older. This study used a combination of monitored air 

quality data and remote-sensing (i.e., satellite) data to assign PM2.5 concentrations to the 

population cohort. Notably, the median annual mean PM2.5 levels observed, or modeled, in this 

study were 7.4 μg/m3 and the minimum value was 1.9 μg/m3. The authors note that these air 

quality values are significantly lower than those observed in either the ACS or Six Cities studies, 

which provides further evidence that PM effects may occur at very low annual mean PM2.5

levels.

Lepeule et al. (2012) evaluated the sensitivity of previous Six Cities results to model

specifications, lower exposures, and averaging time using eleven additional years of cohort 

follow-up that incorporated recent lower exposures. The authors found significant associations

between PM2.5 exposure and increased risk of all-cause, cardiovascular and lung cancer 

mortality. The authors also concluded that the concentration-response relationship was linear 

down to PM2.5 concentrations of 8 μg/m3, and that mortality rate ratios for PM2.5 fluctuated 

over time, but without clear trends, despite a substantial drop in the sulfate fraction.

As further described in the mortality valuation discussion, we assume that there is a 

“cessation” lag between PM exposures and the total realization of changes in health effects. 

While the structure of the lag is uncertain, most of the premature deaths occur within the first 

couple years after the change in exposure (U.S. EPA, 2004c; Schwartz et al, 2008). Changes in 

the cessation lag assumptions do not change the total number of estimated deaths but rather 

the timing of those deaths.

In addition to the adult mortality studies described above, several studies provide 

evidence for an association between PM exposure and respiratory inflammation and infection 

leading to premature mortality in children under 5 years of age. Specifically, the SAB-HES noted 

the release of the WHO Global Burden of Disease Study focusing on ambient air, which cites 

several recently published time-series studies relating daily PM exposure to mortality in 

children (U.S. EPA-SAB, 2004a). The SAB-HES also cites the study by Belanger et al. (2003) as 

corroborating findings linking PM exposure to increased respiratory inflammation and 

infections in children. Recently, a study by Chay and Greenstone (2003) found that reductions 

in TSP caused by the recession of 1981– 1982 were related to reductions in infant mortality at 

the county level. With regard to the cohort study conducted by Woodruff et al. (1997), the SABHES notes several strengths of the study, including the use of a larger cohort drawn from a large 

number of metropolitan areas and efforts to control for a variety of individual risk factors in 
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infants (e.g., maternal educational level, maternal ethnicity, parental marital status, and 

maternal smoking status). Based on these findings, the SAB-HES recommends that EPA 

incorporate infant mortality into the primary benefits estimate and that infant mortality be 

evaluated using an impact function developed from the Woodruff et al. (1997) study (U.S. EPASAB, 2004a). A more recent study by Woodruff et al. (2006) continues to find associations 

between PM2.5 and infant mortality. The study also found the most significant relationships with 

respiratory-related causes of death. We have not yet sought comment from the SAB on this 

more recent study and as such continue to rely on the earlier 1997 analysis.

5.6.3.2 Nonfatal Acute Myocardial Infarctions (AMI) (Heart Attacks)

Nonfatal heart attacks have been linked with short-term exposures to PM2.5 in the 

United States (Mustafić et al., 2012; Peters et al., 2001; Sullivan et al., 2005; Pope et al., 2006;

Zanobetti and Schwartz, 2006; Zanobetti et al., 2009) and other countries (Poloniecki et al., 

1997; Barnett et al., 2006; Peters et al., 2005). In previous health impact assessments, we have 

relied upon a study by Peters et al. (2001) as the basis for the impact function estimating the 

relationship between PM2.5 and nonfatal heart attacks. The Peters et al. (2001) study exhibits a 

number of strengths. In particular, it includes a robust characterization of populations 

experiencing acute myocardial infarctions (AMIs). The researchers interviewed patients within 4 

days of their AMI events and, for inclusion in the study, patients were required to meet a series 

of criteria including minimum kinase levels, an identifiable onset of pain or other symptoms and 

the ability to indicate the time, place and other characteristics of their AMI pain in an interview.

Since the publication of Peters et al. (2001), a number of other single and multi-city 

studies have appeared in the literature. These studies include Sullivan et al. (2005), which 

considered the risk of PM2.5-related hospitalization for AMIs in King County, WA; Pope et al. 

(2006), based in Wasatch Range, UT; Zanobetti and Schwartz (2006), based in Boston; and, 

Zanobetti et al. (2009), a multi-city study of 26 U.S. communities. Each of these single and 

multi-city studies, with the exception of Pope et al. (2006), measure AMIs using hospital 

discharge rates. Conversely, the Pope et al. (2006) study is based on a large registry with 

angiographically characterized patients—arguably a more precise indicator of AMI. Because the 

Pope et al. (2006) study reflected both myocardial infarctions and unstable angina, this 

produces a more comprehensive estimate of acute ischemic heart disease events than the 

other studies. However, unlike the Peters study (Peters et al., 2006), Pope and colleagues did 

not measure the time of symptom onset, and PM2.5 data were not measured on an hourly basis.
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As a means of recognizing the strengths of the Peters study while also incorporating the 

newer evidence found in the four single and multi-city studies, we present a range of AMI 

estimates. The upper end of the range is calculated using the Peters study while the lower end 

of the range is the result of an equal-weights pooling of these four newer studies. It is 

important to note that when calculating the incidence of nonfatal AMI, the fraction of fatal 

heart attacks is subtracted to ensure that there is no double-counting with premature mortality 

estimates. Specifically, based on Rosamond et al. (1999), we apply an adjustment factor of 0.93 

in the concentration-response function to reflect the probability of survival 28 days after the 

heart attack.

5.6.3.3 Hospital Admissions and Emergency Department Visits

Because of the availability of detailed hospital admission and discharge records, there is 

an extensive body of literature examining the relationship between hospital admissions and air 

pollution. For this reason, we pool together the incidence estimates using several different 

studies for many of the hospital admission endpoints. In addition, some studies have examined 

the relationship between air pollution and emergency department visits. Since most emergency 

department visits do not result in an admission to the hospital (i.e., most people going to the 

emergency department are treated and return home), we treat hospital admissions and 

emergency department visits separately, taking account of the fraction of emergency 

department visits that are admitted to the hospital. Specifically, within the baseline incidence 

rates, we parse out the scheduled hospital visits from unscheduled ones as well as the hospital 

visits that originated in the emergency department.

The two main groups of hospital admissions estimated in this analysis are respiratory 

admissions and cardiovascular admissions. There is not much evidence linking PM2.5 with other 

types of hospital admissions. Both asthma- and cardiovascular-related visits have been linked to 

PM2.5 in the United States, though as we note below, we are able to assign an economic value 

to asthma-related events only. To estimate the effects of PM2.5 air pollution reductions on 

asthma-related ER visits, we use the effect estimate from a study of children 18 and under by 

Mar et al. (2010) and Slaughter et al. (2005). Both studies examine populations 0 to 99 in 

Washington State. Mar and colleagues perform their study in Tacoma, while Slaughter and 

colleagues base their study in Spokane. We apply random/fixed effects pooling to combine 

evidence across these two studies.

To estimate avoided incidences of cardiovascular hospital admissions associated with 

PM2.5, we used studies by Moolgavkar (2000), Zanobetti et al. (2009), Peng et al. (2008, 2009) 
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and Bell et al., (2008). Only Moolgavkar (2000) provided a separate effect estimate for adults 20 

to 64, while the remainder estimate risk among adults over 64.7 Total cardiovascular hospital 

admissions are thus the sum of the pooled estimate for adults over 65 and the single study 

estimate for adults 20 to 64. Cardiovascular hospital admissions include admissions for 

myocardial infarctions. To avoid double-counting benefits from reductions in myocardial 

infarctions when applying the impact function for cardiovascular hospital admissions, we first 

adjusted the baseline cardiovascular hospital admissions to remove admissions for myocardial 

infarctions. We applied equal weights pooling to the multi-city studies assessing risk among 

adults over 64 because these studies already incorporated pooling across the city-level 

estimates. One potential limitation of our approach is that while the Zanobetti et al. (2009) 

study assesses all cardiovascular risk, Bell et al. (2008), and Peng et al., (2008, 2009) studies 

estimate a subset of cardiovascular hospitalizations as well as certain cerebro- and peripheralvascular diseases. To address the potential for the pooling of these four studies to produce a 

biased estimate, we match the pooled risk estimate with a baseline incidence rate that excludes 

cerebro- and peripheral-vascular disease. An alternative approach would be to use the 

Zanobetti et al. (2009) study alone, though this would prevent us from drawing upon the 

strengths of the three multi-city studies.

To estimate avoided incidences of respiratory hospital admissions associated with PM2.5, 

we used a number of studies examining total respiratory hospital admissions as well as asthma 

and chronic lung disease. We estimated impacts among three age groups: adults over 65, adults 

18 to 64 and children 0 to 17. For adults over 65, the multi-city study by Zanobetti et al. (2009) 

provides an effect estimate for total respiratory hospital admissions (defined as ICD codes 460–

519). Moolgavkar et al. (2003) examines PM2.5 and chronic lung disease hospital admissions 

(less asthma) in Los Angeles, CA among adults 18 to 64. For children 0 to 18, we pool two 

studies using random/fixed effects. The first is Babin et al. (2007) which assessed PM2.5 and 

asthma hospital admissions in Washington, DC among children 1 to 18; we adjusted the age 

range for this study to apply to children 0 to 18. The second is Sheppard et al. (2003) which 

assessed PM2.5 and asthma hospitalizations in Seattle, Washington, among children 0 to 18.

 7 Note that the Moolgavkar (2000) study has not been updated to reflect the more stringent GAM convergence 

criteria. However, given that no other estimates are available for this age group, we chose to use the existing 

study. Given the very small (<5%) difference in the effect estimates for people 65 and older with cardiovascular 

hospital admissions between the original and reanalyzed results, we do not expect this choice to introduce 

much bias. For a discussion of the GAM convergence criteria, and how it affected the size of effect coefficients 

reported by time series epidemiological studies using NMMAPS data, see: 

http://www.healtheffects.org/Pubs/st-timeseries.htm.
5-39

5.6.3.4 Acute Health Events and School/Work Loss Days

In addition to mortality, chronic illness, and hospital admissions, a number of acute

health effects not requiring hospitalization are associated with exposure to PM2.5. The sources 

for the effect estimates used to quantify these effects are described below.

Approximately 4% of U.S. children between the ages of 5 and 17 experience episodes of 

acute bronchitis annually (ALA, 2002). Acute bronchitis is characterized by coughing, chest 

discomfort, slight fever, and extreme tiredness, lasting for a number of days. According to the 

MedlinePlus medical encyclopedia,8 with the exception of cough, most acute bronchitis 

symptoms abate within 7 to 10 days. Incidence of episodes of acute bronchitis in children 

between the ages of 5 and 17 were estimated using an effect estimate developed from Dockery 

et al. (1996). Incidences of lower respiratory symptoms (e.g., wheezing, deep cough) in children 

aged 7 to 14 were estimated using an effect estimate from Schwartz and Neas (2000).

Because asthmatics have greater sensitivity to stimuli (including air pollution), children 

with asthma can be more susceptible to a variety of upper respiratory symptoms (e.g., runny or 

stuffy nose; wet cough; and burning, aching, or red eyes). Research on the effects of air 

pollution on upper respiratory symptoms has thus focused on effects in asthmatics. Incidences 

of upper respiratory symptoms in asthmatic children aged 9 to 11 are estimated using an effect 

estimate developed from Pope et al. (1991).

Health effects from air pollution can also result in missed days of work (either from 

personal symptoms or from caring for a sick family member). Days of work lost due to PM2.5

were estimated using an effect estimate developed from Ostro (1987). Children may also be 

absent from school because of respiratory or other diseases caused by exposure to air 

pollution, but we have not quantified these effects for this rule.

Minor restricted activity days (MRAD) result when individuals reduce most usual daily 

activities and replace them with less strenuous activities or rest, yet not to the point of missing 

work or school. For example, a mechanic who would usually be doing physical work most of the 

day will instead spend the day at a desk doing paper and phone work because of difficulty 

breathing or chest pain. The effect of PM2.5 on MRAD was estimated using an effect estimate 

derived from Ostro and Rothschild (1989).

More recently published literature examining the relationship between short-term PM2.5 

exposure and acute respiratory symptoms was available in the PM ISA (U.S. EPA, 2009), but 

 8 See http://www.nlm.nih.gov/medlineplus/ency/article/001087.htm, accessed April 2012. 
5-40

proved to be unsuitable for use in this benefits analysis. In particular, the best available study 

(Patel et al., 2010) specified a population aged 13-20, which overlaps with the population in 

which we asses asthma exacerbation. As we describe in detail below, to avoid the chance of 

double-counting impacts, we do not estimate changes in acute respiratory symptoms and 

asthma exacerbation among populations of the same age.

For this RIA, we have followed the SAB-HES recommendations regarding asthma 

exacerbations in developing the main estimate (U.S. EPA-SAB, 2004a). While certain studies of 

acute respiratory events characterize these impacts among only asthmatic populations, others 

consider the full population, including both asthmatics and non-asthmatics. For this reason, 

incidence estimates derived from studies focused only on asthmatics cannot be added to 

estimates from studies that consider the full population—to do so would double-count impacts. 

To prevent such double-counting, we estimated the exacerbation of asthma among children 

and excluded adults from the calculation. Asthma exacerbations occurring in adults are 

assumed to be captured in the general population endpoints such as work loss days and 

MRADs. Finally, note also the important distinction between the exacerbation of asthma among 

asthmatic populations, and the onset of asthma among populations not previously suffering 

from asthma; in this RIA, we quantify the exacerbation of asthma among asthmatic populations 

and not the onset of new cases of asthma.

To characterize asthma exacerbations in children, we selected two studies (Ostro et al., 

2001; Mar et al., 2004) that followed panels of asthmatic children. Ostro et al. (2001) followed a 

group of 138 African-American children in Los Angeles for 13 weeks, recording daily 

occurrences of respiratory symptoms associated with asthma exacerbations (e.g., shortness of 

breath, wheeze, and cough). This study found a statistically significant association between 

PM2.5, measured as a 12-hour average, and the daily prevalence of shortness of breath and 

wheeze endpoints. Although the association was not statistically significant for cough, the 

results were still positive and close to significance; consequently, we decided to include this 

endpoint, along with shortness of breath and wheeze, in generating incidence estimates (see 

below).

Mar et al. (2004) studied the effects of various size fractions of particulate matter on 

respiratory symptoms of adults and children with asthma, monitored over many months. The 

study was conducted in Spokane, Washington, a semiarid city with diverse sources of 

particulate matter. Data on respiratory symptoms and medication use were recorded daily by 

the study’s subjects, while air pollution data was collected by the local air agency and 

Washington State University. Subjects in the study consisted of 16 adults—the majority of 
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whom participated for over a year—and nine children, all of whom were studied for over eight 

months. Among the children, the authors found a strong association between cough symptoms 

and several metrics of particulate matter, including PM2.5. However, the authors found no 

association between respiratory symptoms and PM of any metric in adults. Mar et al. therefore 

concluded that the discrepancy in results between children and adults was due either to the 

way in which air quality was monitored, or a greater sensitivity of children than adults to 

increased levels of PM air pollution.

We employed the following pooling approach in combining estimates generated using 

effect estimates from the two studies to produce a single asthma exacerbation incidence 

estimate. First, we used random/fixed effects pooling to combine the Ostro and Mar estimates 

for shortness of breath and cough. Next, we pooled the Ostro estimate of wheeze with the 

pooled cough and shortness of breath estimates to derive an overall estimate of asthma 

exacerbation.

5.6.3.5 Effect Coefficients Selected for the Sensitivity Analyses

Chronic Bronchitis. Chronic bronchitis is characterized by mucus in the lungs and a 

persistent wet cough for at least 3 months a year for several years in a row. Chronic bronchitis

affects an estimated 5% of the U.S. population (ALA, 1999). A limited number of studies have 

estimated the impact of air pollution on new incidences of chronic bronchitis. Schwartz (1993) 

and Abbey et al. (1995) provide evidence that long-term PM2.5 exposure gives rise to the 

development of chronic bronchitis in adults in the United States; these remain the two most 

recent studies observing a relationship between long-term exposure to PM2.5 and the onset of 

chronic bronchitis in the U.S. The absence of newer studies finding a relationship between longterm PM2.5 exposure and chronic bronchitis argues for moving this endpoint from the main 

benefits analysis to a sensitivity analysis. In their review of the scientific literature on chronic 

obstructive pulmonary disease (COPD), which includes chronic bronchitis and emphysema, the 

American Thoracic Society concluded that air pollution is “associated with COPD, but sufficient 

criteria for causation were not met” (Eisner et al., 2010).

Stroke. The PM ISA (U.S. EPA, 2009) includes several new studies that have examined 

the relationship between PM2.5 exposure and cerebrovascular events (U.S. EPA, 2009). Timeseries studies have generally been inconsistent with several studies showing positive 

associations (Dominici et al., 2006; Metzger et al., 2004; Lippman et al., 2000; Lisabeth et al.,

2008). Several other studies have demonstrated null or negative associations (Anderson et al.,

2001; Barnett et al., 2006; Peel et al., 2007). In general, these studies examined cerebrovascular 
5-42

disease as a group, though a few studies partition ischemic and hemorrhagic strokes separately 

(Lisabeth et al., 2008). A key limitation of these time-series studies is that they use hospital 

discharge rates as the diagnosis and relatively short lags (0–2 days)—this is problematic, as 

discharge rates are an imperfect diagnosis and strokes may occur several days before admission 

to the hospital.

Longer-term prospective cohort studies of PM2.5 and stroke include Miller et al. (2007), 

which estimated the change in risk among post-menopausal women enrolled in the Women’s

Health Initiative (U.S. EPA, 2009b). After adjusting for age, race, smoking status, educational 

level, household income, body-mass index, diabetes, hypertension, and hypercholesterolemia, 

hazard ratios were estimated for the first cardiovascular event. Because this study considers 

first-time cardiovascular events, a key challenge to incorporating this study into a health impact 

assessment would be to match the baseline incidence rate correctly.

Three factors argue for treating this endpoint in the sensitivity analysis: (1) the 

epidemiological literature examining PM-related cerebrovascular events is still evolving; (2) 

there are special uncertainties associated with quantifying this endpoint; (3) we have not yet 

identified an appropriate method for estimating the economic value of this endpoint.

Cardiovascular Emergency Department Visits. A large number of recent U.S.-based 

studies provide support for an association between short-term increases in PM2.5 and increased 

risk of ED visits for ischemic heart diseases (U.S. EPA, 2009b). Both Metzger et al. (2004) and 

Tolbert et al. (2007) published interim results from the Study of Particles and Health in Atlanta

(SOPHIA), finding a relationship between PM2.5 exposure and cardiovascular emergency 

department visits. These cardiovascular emergency department visits are distinct from 

cardiovascular hospital admissions and non-fatal heart attacks. To ensure no double-counting, 

we excluded ICD-9-411 (ischemic heart disease) from the baseline incidence rates for 

cardiovascular emergency department visits. The principal challenge to incorporating these 

studies is the absence of readily-available economic valuation estimates for cardiovascular 

emergency department visits. Until we develop an approach for estimating the economic value 

of this endpoint, we will treat these ED visits as a sensitivity analysis.

5.6.4 Unquantified Human Health Benefits

Implementing the illustrative control strategy described in Chapter 4 would reduce 

emissions of directly emitted particles, SO2, and NOx. Although we have quantified many of the 

health benefits associated with reducing exposure to PM2.5, as shown in Table 5-2, we are 
5-43

unable to quantify the health benefits associated with reducing ozone exposure, SO2 exposure, 

NO2 exposure or methylmercury exposure due to the absence of air quality modeling data for 

these pollutants in this analysis. Although we applied the rollback method to simulate the 

impact of attaining alternative combination of standard levels on ambient levels of PM2.5, this 

method does not simulate how the illustrative emission reductions would affect ambient levels 

of ozone, SO2, or NO2. Furthermore, the air quality modeling conducted for this analysis did not 

assess mercury, so we are unable to estimate mercury deposition associated with the 

illustrative controls or subsequent bioaccumulation and exposure. Below we provide a 

qualitative description these health benefits. In general, previous analyses have shown that the 

monetized value of these additional health benefits is much smaller than PM2.5-related benefits 

(U.S. EPA, 2010a, 2010c, 2010d). The extent to which ozone, SO2, NOx, and/or methylmercury 

would be reduced would depend on the specific control strategy used to reduce PM2.5 in a given 

area.

Reducing NOx emissions also reduces ozone concentrations in most areas. Reducing 

ambient ozone concentrations is associated with significant human health benefits, including 

mortality and respiratory morbidity (U.S. EPA, 2008a, 2010d). Epidemiological researchers have 

associated ozone exposure with adverse health effects in numerous toxicological, clinical and 

epidemiological studies (U.S. EPA, 2006b). When adequate data and resources are available, 

EPA generally quantifies several health effects associated with exposure to ozone (e.g., U.S. 

EPA, 2008a, 2010d, 2011a, 2011c). These health effects include respiratory morbidity such as 

asthma attacks, hospital and emergency department visits, school loss days, as well as 

premature mortality. The scientific literature suggests that exposure to ozone is also associated 

with chronic respiratory damage and premature aging of the lungs, but EPA has not quantified 

these effects in benefits analyses previously.

Following an extensive evaluation of health evidence from epidemiologic and laboratory 

studies, the Integrated Science Assessment for Sulfur Dioxide—Health Criteria (SO2 ISA) 

concluded that there is a causal relationship between respiratory health effects and short-term 

exposure to SO2 (U.S. EPA, 2008c). The immediate effect of SO2 on the respiratory system in 

humans is bronchoconstriction. Asthmatics are more sensitive to the effects of SO2 likely 

resulting from preexisting inflammation associated with this disease. A clear concentrationresponse relationship has been demonstrated in laboratory studies following exposures to SO2

at concentrations between 20 and 100 ppb, both in terms of increasing severity of effect and 

percentage of asthmatics adversely affected. Based on our review of this information, we 

identified four short-term morbidity endpoints that the SO2 ISA identified as a “causal 
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relationship”: asthma exacerbation, respiratory-related emergency department visits, and 

respiratory-related hospitalizations. The differing evidence and associated strength of the 

evidence for these different effects is described in detail in the SO2 ISA. The SO2 ISA also 

concluded that the relationship between short-term SO2 exposure and premature mortality was 

“suggestive of a causal relationship” because it is difficult to attribute the mortality risk effects 

to SO2 alone. Although the SO2 ISA stated that studies are generally consistent in reporting a 

relationship between SO2 exposure and mortality, there was a lack of robustness of the 

observed associations to adjustment for pollutants. We did not quantify these benefits due to 

data constraints.

Epidemiological researchers have associated NO2 exposure with adverse health effects 

in numerous toxicological, clinical and epidemiological studies, as described in the Integrated 

Science Assessment for Oxides of Nitrogen—Health Criteria (NO2 ISA) (U.S. EPA, 2008b). The 

NO2 ISA provides a comprehensive review of the current evidence of health and environmental 

effects of NO2. The NO2 ISA concluded that the evidence “is sufficient to infer a likely causal 

relationship between short-term NO2 exposure and adverse effects on the respiratory system.”

These epidemiologic and experimental studies encompass a number of endpoints including 

emergency department visits and hospitalizations, respiratory symptoms, airway 

hyperresponsiveness, airway inflammation, and lung function. Effect estimates from 

epidemiologic studies conducted in the United States and Canada generally indicate a 2–20% 

increase in risks for ED visits and hospital admissions and higher risks for respiratory symptoms. 

The NO2 ISA concluded that the relationship between short-term NO2 exposure and premature 

mortality was “suggestive but not sufficient to infer a causal relationship” because it is difficult 

to attribute the mortality risk effects to NO2 alone. Although the NO2 ISA stated that studies 

consistently reported a relationship between NO2 exposure and mortality, the effect was 

generally smaller than that for other pollutants such as PM. We did not quantify these benefits 

due to data constraints.

5.6.5 Economic Valuation Estimates

Reductions in ambient concentrations of air pollution generally lower the risk of future 

adverse health effects for a large population. Therefore, the appropriate economic measure is 

WTP for changes in risk of a health effect rather than WTP for a health effect that would occur 

with certainty (Freeman, 1993). Epidemiological studies generally provide estimates of the 

relative risks of a particular health effect that is avoided because of a reduction in air pollution. 

We converted those changes in risk to units of avoided statistical incidence for ease of 
5-45

presentation. We calculated the value of avoided statistical incidences by dividing individual 

WTP for a risk reduction by the related observed change in risk.

WTP estimates generally are not available for some health effects, such as hospital 

admissions. In these cases, we instead used the cost of treating or mitigating the effect to 

estimate the economic value. These cost-of-illness (COI) estimates generally understate the 

true value of reducing the risk of a health effect, because they reflect the direct expenditures 

related to treatment, but not the value of avoided pain and suffering (Harrington and Portney, 

1987; Berger, 1987). We provide unit values for health endpoints (along with information on 

the distribution of the unit value) in Table 5-9. All values are in constant year 2006 dollars, 

adjusted for growth in real income out to 2020 using projections provided by Standard and 

Poor’s. Economic theory argues that WTP for most goods (such as environmental protection) 

will increase if real income increases. Several of the valuation studies used in this analysis were 

conducted in the late 1980s and early 1990s, and we are in the process of reviewing the 

literature to update these unit values. Because real income has grown since the studies were 

conducted, people’s willingness to pay for reductions in the risk of premature death and 

disease likely has grown as well. We do not have data to adjust the COI estimates for 

projections of medical costs in the future, which leads to an inherent though unavoidable 

inconsistency between COI- and WTP-based estimates. For these two reasons, these cost-ofillness estimates may underestimate the economic value of avoided health impacts. The 

discussion below provides additional details on valuing PM2.5-related related endpoints.
5-46

Table 5-9. Unit Values for Economic Valuation of Health Endpoints (2006$)a

Health Endpoint

Central Estimate of Value Per Statistical Incidence

1990 Income Level 2020 Income Level Derivation of Distributions of Estimates

Premature Mortality (Value of a 

Statistical Life)

$6,300,000 $8,900,000 EPA currently recommends a central VSL of $4.8m (1990$, 1990 

income) based on a Weibull distribution fitted to 26 published VSL 

estimates (5 contingent valuation and 21 labor market studies). The 

underlying studies, the distribution parameters, and other useful 

information are available in Appendix B of EPA’s Guidelines for 

Preparing Economic Analyses (U.S. EPA, 2010e).

Nonfatal Myocardial Infarction 

(heart attack)

3% discount rate

Age 0–24

Age 25–44

Age 45–54

Age 55–65

Age 66 and over

7% discount rate

Age 0–24

Age 25–44

Age 45–54

Age 55–64

Age 65 and over

$85,000

$96,000

$100,000

$180,000

$85,000

$84,000

$94,000

$98,000

$170,000

$84,000

$85,000

$96,000

$100,000

$180,000

$85,000

$84,000

$94,000

$98,000

$170,000

$84,000

No distributional information available. Age-specific cost-of-illness 

values reflect lost earnings and direct medical costs over a 5-year 

period following a nonfatal MI. Lost earnings estimates are based on 

Cropper and Krupnick (1990). Direct medical costs are based on 

simple average of estimates from Russell et al. (1998) and Wittels et 

al. (1990).

Lost earnings:

Cropper and Krupnick (1990). Present discounted value of 5 years of 

lost earnings in 2000$:

age of onset: at 3% at 7%

25–44 $9,000 $8,000

45–54 $13,000 $12,000

55–65 $77,000 $69,000

Direct medical expenses (2000$): An average of:

1. Wittels et al. (1990) ($100,000—no discounting)

2. Russell et al. (1998), 5-year period ($22,000 at 3% discount 

rate; $21,000at 7% discount rate)

Hospital Admissions

Chronic Lung Disease (18-64) $19,000 $19,000 No distributional information available. The COI estimates (lost 

earnings plus direct medical costs) are based on ICD-9 code-level 

information (e.g., average hospital care costs, average length of 

hospital stay, and weighted share of total chronic lung illnesses) 

reported in Agency for Healthcare Research and Quality (2007) 

(www.ahrq.gov). 

(continued)
5-47

Table 5-9. Unit Values for Economic Valuation of Health Endpoints (2006$)a (continued)

Health Endpoint

Central Estimate of Value Per Statistical Incidence

2000 Income Level 2020 Income Level Derivation of Distributions of Estimates

Hospital Admissions (continued)

Asthma Admissions (0-64) $14,000 $14,000 No distributional information available. The COI estimates (lost 

earnings plus direct medical costs) are based on ICD-9 code-level 

information (e.g., average hospital care costs, average length of 

hospital stay, and weighted share of total asthma category illnesses) 

reported in Agency for Healthcare Research and Quality (2007) 

(www.ahrq.gov). 

All Cardiovascular

Age 18-64

Age 65-99

$37,000

$35,000

$37,000

$35,000

No distributional information available. The COI estimates (lost 

earnings plus direct medical costs) are based on ICD-9 code-level 

information (e.g., average hospital care costs, average length of 

hospital stay, and weighted share of total cardiovascular category 

illnesses) reported in Agency for Healthcare Research and Quality 

(2007) (www.ahrq.gov). 

All respiratory (ages 65+) $32,000 $32,000 No distributions available. The COI point estimates (lost earnings plus 

direct medical costs) are based on ICD-9 code level information (e.g., 

average hospital care costs, average length of hospital stay, and 

weighted share of total respiratory category illnesses) reported in 

Agency for Healthcare Research and Quality, 2007 (www.ahrq.gov).

Emergency Department Visits 

for Asthma

$370 $370 No distributional information available. Simple average of two unit 

COI values (2000$):

(1) $310, from Smith et al. (1997) and

(2) $260, from Stanford et al. (1999).

(continued)
5-48

Table 5-9. Unit Values for Economic Valuation of Health Endpoints (2006$)a (continued)

Health Endpoint

Central Estimate of Value Per Statistical Incidence

2000 Income Level 2020 Income Level Derivation of Distributions of Estimates

Respiratory Ailments Not Requiring Hospitalization

Upper Respiratory Symptoms 

(URS)

$25 $31 Combinations of the three symptoms for which WTP estimates are 

available that closely match those listed by Pope et al. result in seven 

different “symptom clusters,” each describing a “type” of URS. A 

dollar value was derived for each type of URS, using mid-range 

estimates of WTP (IEc, 1994) to avoid each symptom in the cluster 

and assuming additivity of WTPs. In the absence of information 

surrounding the frequency with which each of the seven types of 

URS occurs within the URS symptom complex, we assumed a uniform 

distribution between $9.2 and $43 (2000$).

Lower Respiratory Symptoms 

(LRS)

$16 $19 Combinations of the four symptoms for which WTP estimates are 

available that closely match those listed by Schwartz et al. result in 

11 different “symptom clusters,” each describing a “type” of LRS. A 

dollar value was derived for each type of LRS, using mid-range 

estimates of WTP (IEc, 1994) to avoid each symptom in the cluster 

and assuming additivity of WTPs. The dollar value for LRS is the 

average of the dollar values for the 11 different types of LRS. In the 

absence of information surrounding the frequency with which each 

of the 11 types of LRS occurs within the LRS symptom complex, we 

assumed a uniform distribution between $6.9 and $25 (2000$).

Asthma Exacerbations $43 $53 Asthma exacerbations are valued at $45 per incidence, based on the 

mean of average WTP estimates for the four severity definitions of a 

“bad asthma day,” described in Rowe and Chestnut (1986). This 

study surveyed asthmatics to estimate WTP for avoidance of a “bad 

asthma day,” as defined by the subjects. For purposes of valuation, 

an asthma exacerbation is assumed to be equivalent to a day in 

which asthma is moderate or worse as reported in the Rowe and 

Chestnut (1986) study. The value is assumed have a uniform 

distribution between $16 and $71 (2000$).

(continued)
5-49

Table 5-9. Unit Values for Economic Valuation of Health Endpoints (2006$)a (continued)

Health Endpoint

Central Estimate of Value Per Statistical Incidence

2000 Income Level 2020 Income Level Derivation of Distributions of Estimates

Respiratory Ailments Not Requiring Hospitalization (continued)

Acute Bronchitis $360 $440 Assumes a 6-day episode, with the distribution of the daily value 

specified as uniform with the low and high values based on those 

recommended for related respiratory symptoms in Neumann et al. 

(1994). The low daily estimate of $10 is the sum of the mid-range 

values recommended by IEc (1994) for two symptoms believed to be 

associated with acute bronchitis: coughing and chest tightness. The 

high daily estimate was taken to be twice the value of a minor 

respiratory restricted-activity day, or $110 (2000$). 

Work Loss Days (WLDs) Variable (U.S. median = 

$140)

Variable (U.S. median = 

$140)

No distribution available. Point estimate is based on county-specific 

median annual wages divided by 52 and then by 5—to get median 

daily wage. U.S. Year 2000 Census, compiled by Geolytics, Inc.

(Geolytics, 2002)

Minor Restricted Activity Days 

(MRADs)

$51 $63 Median WTP estimate to avoid one MRAD from Tolley et al. (1986). 

Distribution is assumed to be triangular with a minimum of $22 and a 

maximum of $83, with a most likely value of $52 (2000$). Range is 

based on assumption that value should exceed WTP for a single mild 

symptom (the highest estimate for a single symptom—for eye 

irritation—is $16.00) and be less than that for a WLD. The triangular 

distribution acknowledges that the actual value is likely to be closer 

to the point estimate than either extreme.

a All estimates are rounded to two significant digits. Unrounded estimates in 2000$ are available in the Appendix J of the BenMAP user manual (Abt 

Associates, 2011).
5-50

5.6.6.1 Mortality Valuation

Following the advice of the EEAC of the SAB, EPA currently uses the value of statistical 

life (VSL) approach in calculating the main estimate of mortality benefits, because we believe 

this calculation provides the most reasonable single estimate of an individual’s willingness to 

trade off money for reductions in mortality risk (U.S. EPA-SAB, 2000). The VSL approach is a 

summary measure for the value of small changes in mortality risk experienced by a large 

number of people. For a period of time (2004–2008), the Office of Air and Radiation (OAR) 

valued mortality risk reductions using a VSL estimate derived from a limited analysis of some of 

the available studies. OAR arrived at a VSL using a range of $1 million to $10 million (2000$) 

consistent with two meta-analyses of the wage-risk literature. The $1 million value represented 

the lower end of the interquartile range from the Mrozek and Taylor (2002) meta-analysis of 33 

studies. The $10 million value represented the upper end of the interquartile range from the 

Viscusi and Aldy (2003) meta-analysis of 43 studies. The mean estimate of $5.5 million (2000$) 

was also consistent with the mean VSL of $5.4 million estimated in the Kochi et al. (2006) metaanalysis. However, the Agency neither changed its official guidance on the use of VSL in rulemakings nor subjected the interim estimate to a scientific peer-review process through the 

Science Advisory Board (SAB) or other peer-review group.

During this time, the Agency continued work to update its guidance on valuing mortality 

risk reductions, including commissioning a report from meta-analytic experts to evaluate 

methodological questions raised by EPA and the SAB on combining estimates from the various 

data sources. In addition, the Agency consulted several times with the Science Advisory Board 

Environmental Economics Advisory Committee (SAB-EEAC) on the issue. With input from the 

meta-analytic experts, the SAB-EEAC advised the Agency to update its guidance using specific, 

appropriate meta-analytic techniques to combine estimates from unique data sources and 

different studies, including those using different methodologies (i.e., wage-risk and stated 

preference) (U.S. EPA-SAB, 2007).

Until updated guidance is available, the Agency determined that a single, peer-reviewed 

estimate applied consistently best reflects the SAB-EEAC advice it has received. Therefore, the 

Agency has decided to apply the VSL that was vetted and endorsed by the SAB in the Guidelines 

for Preparing Economic Analyses (U.S. EPA, 2000)1 while the Agency continues its efforts to 

update its guidance on this issue. This approach calculates a mean value across VSL estimates 

 1 In the updated Guidelines for Preparing Economic Analyses (U.S. EPA, 2010e), EPA retained the VSL endorsed by 

the SAB with the understanding that further updates to the mortality risk valuation guidance would be 

forthcoming in the near future.
5-51

derived from 26 labor market and contingent valuation studies published between 1974 and 

1991. The mean VSL across these studies is $4.8 million (1990$) or $6.3 million (2000$).2 The 

Agency is committed to using scientifically sound, appropriately reviewed evidence in valuing 

mortality risk reductions and has made significant progress in responding to the SAB-EEAC’s 

specific recommendations. In the process, the Agency has identified a number of important 

issues to be considered in updating its mortality risk valuation estimates. These are detailed in a 

white paper on “Valuing Mortality Risk Reductions in Environmental Policy,” which recently 

underwent review by EPA’s independent Science Advisory Board). A meeting with the SAB on 

this paper was held on March 14, 2011 and formal recommendations were transmitted on 

July 29, 2011 (U.S. EPA-SAB, 2011). Draft guidance responding to SAB recommendations will be 

developed shortly.

The economics literature concerning the appropriate method for valuing reductions in 

premature mortality risk is still developing. The adoption of a value for the projected reduction 

in the risk of premature mortality is the subject of continuing discussion within the economics 

and public policy analysis community. EPA strives to use the best economic science in its 

analyses. Given the mixed theoretical finding and empirical evidence regarding adjustments to 

VSL for risk and population characteristics, we use a single VSL for all reductions in mortality 

risk.

Although there are several differences between the labor market studies EPA uses to 

derive a VSL estimate and the PM2.5 air pollution context addressed here, those differences in 

the affected populations and the nature of the risks imply both upward and downward 

adjustments. Table 5-10 lists some of these differences and the expected effect on the VSL 

estimate for air pollution-related mortality. In the absence of a comprehensive and balanced 

set of adjustment factors, EPA believes it is reasonable to continue to use the $4.8 million 

(1990$) value adjusted for inflation and income growth over time while acknowledging the 

significant limitations and uncertainties in the available literature.

The SAB-EEAC has reviewed many potential VSL adjustments and the state of the 

economics literature. The SAB-EEAC advised EPA to “continue to use a wage-risk-based VSL as 

its primary estimate, including appropriate sensitivity analyses to reflect the uncertainty of 

these estimates,” and that “the only risk characteristic for which adjustments to the VSL can be 

made is the timing of the risk” (U.S. EPA-SAB, 2000). In developing our main estimate of the 

 2 In this analysis, we adjust the VSL to account for a different currency year (2006$) and to account for income 

growth to 2020. After applying these adjustments to the $6.3 million value, the VSL is $8.9M. 
5-52

benefits of premature mortality reductions, we have followed this advice. For premature 

mortality, we assume that there is a “cessation” lag between PM exposures and the total 

realization of changes in health effects. We assumed for this analysis that some of the 

incidences of premature mortality related to PM2.5 exposures occur in a distributed fashion over 

the 20 years following exposure and discounted over the period between exposure and 

premature mortality. Although the structure of the lag is uncertain, EPA follows the advice of 

the SAB-HES to assume a segmented lag structure characterized by 30% of mortality reductions 

in the first year, 50% over years 2 to 5, and 20% over the years 6 to 20 after the reduction in 

PM2.5 (U.S. EPA-SAB, 2004c). Additional cessation lag structures are described and assessed in 

Appendix 5B of the RIA. To take this into account in the valuation of reductions in premature 

mortality, we discount the value of premature mortality occurring in future years using rates of 

3% and 7%.3 Changes in the cessation lag assumptions do not change the total number of 

estimated deaths but rather the timing of those deaths. As such, the monetized benefits using a 

7% discount rate are only approximately 10% less than the monetized benefits using a 3% 

discount rate. Further discussion of this topic appears in EPA’s Guidelines for Preparing 

Economic Analyses (U.S. EPA, 2010e).

Table 5-10. Influence of Applied VSL Attributes on the Size of the Economic Benefits of 

Reductions in the Risk of Premature Death (U.S. EPA, 2006a)

Attribute Expected Direction of Bias

Age Uncertain, perhaps overestimate

Life Expectancy/Health Status Uncertain, perhaps overestimate

Attitudes Toward Risk Underestimate

Income Uncertain

Voluntary vs. Involuntary Uncertain, perhaps underestimate

Catastrophic vs. Protracted Death Uncertain, perhaps underestimate

Uncertainties Specific to Premature Mortality Valuation. The economic benefits 

associated with reductions in the risk of premature mortality are the largest category of 

monetized benefits of the CSAPR. In addition, in prior analyses, EPA has identified valuation of 

mortality-related benefits as the largest contributor to the range of uncertainty in monetized 

 3 The choice of a discount rate, and its associated conceptual basis, is a topic of ongoing discussion within the 

federal government. To comply with Circular A-4, EPA provides monetized benefits using discount rates of 3% 

and 7% (OMB, 2003). A 3% discount reflects reliance on a “social rate of time preference” discounting concept. 

A 7% rate is consistent with an “opportunity cost of capital” concept to reflect the time value of resources 

directed to meet regulatory requirements. 
5-53

benefits (Mansfield et al., 2009).4 Because of the uncertainty in estimates of the value of 

reducing premature mortality risk, it is important to adequately characterize and understand 

the various types of economic approaches available for valuing reductions in mortality risk. 

Such an assessment also requires an understanding of how alternative valuation approaches 

reflect that some individuals may be more susceptible to air pollution-induced mortality or 

reflect differences in the nature of the risk presented by air pollution relative to the risks 

studied in the relevant economics literature.

The health science literature on air pollution indicates that several human 

characteristics affect the degree to which mortality risk affects an individual. For example, some 

age groups appear to be more susceptible to air pollution than others (e.g., the elderly and 

children). Health status prior to exposure also affects susceptibility. An ideal benefits estimate 

of mortality risk reduction would reflect these human characteristics, in addition to an 

individual’s WTP to improve one’s own chances of survival plus WTP to improve other 

individuals’ survival rates. The ideal measure would also take into account the specific nature of 

the risk reduction commodity that is provided to individuals, as well as the context in which risk 

is reduced. To measure this value, it is important to assess how reductions in air pollution 

reduce the risk of dying from the time that reductions take effect onward and how individuals 

value these changes. Each individual’s survival curve, or the probability of surviving beyond a 

given age, should shift as a result of an environmental quality improvement. For example, 

changing the current probability of survival for an individual also shifts future probabilities of 

that individual’s survival. This probability shift will differ across individuals because survival 

curves depend on such characteristics as age, health state, and the current age to which the 

individual is likely to survive.

Although a survival curve approach provides a theoretically preferred method for 

valuing the benefits of reduced risk of premature mortality associated with reducing air 

pollution, the approach requires a great deal of data to implement. The economic valuation 

literature does not yet include good estimates of the value of this risk reduction commodity. As 

a result, in this study we value reductions in premature mortality risk using the VSL approach.

 4 This conclusion was based on an assessment of uncertainty based on statistical error in epidemiological effect 

estimates and economic valuation estimates. Additional sources of model error such as those examined in the 

PM2.5 mortality expert elicitation (Roman et al., 2008) may result in different conclusions about the relative 

contribution of sources of uncertainty.
5-54

Other uncertainties specific to premature mortality valuation include the following:

 Across-study variation: There is considerable uncertainty as to whether the available 

literature on VSL provides adequate estimates of the VSL for risk reductions from air 

pollution reduction. Although there is considerable variation in the analytical designs 

and data used in the existing literature, the majority of the studies involve the value 

of risks to a middle-aged working population. Most of the studies examine 

differences in wages of risky occupations, using a hedonic wage approach. Certain 

characteristics of both the population affected and the mortality risk facing that 

population are believed to affect the average WTP to reduce the risk. The 

appropriateness of a distribution of WTP based on the current VSL literature for 

valuing the mortality-related benefits of reductions in air pollution concentrations 

therefore depends not only on the quality of the studies (i.e., how well they 

measure what they are trying to measure), but also on the extent to which the risks 

being valued are similar and the extent to which the subjects in the studies are 

similar to the population affected by changes in pollution concentrations.

 Level of risk reduction: The transferability of estimates of the VSL from the wage-risk 

studies to the context of the PM NAAQS analysis rests on the assumption that, 

within a reasonable range, WTP for reductions in mortality risk is linear in risk 

reduction. For example, suppose a study provides a result that the average WTP for 

a reduction in mortality risk of 1/100,000 is $50, but that the actual mortality risk 

reduction resulting from a given pollutant reduction is 1/10,000. If WTP for 

reductions in mortality risk is linear in risk reduction, then a WTP of $50 for a 

reduction of 1/100,000 implies a WTP of $500 for a risk reduction of 1/10,000 

(which is 10 times the risk reduction valued in the study). Under the assumption of 

linearity, the estimate of the VSL does not depend on the particular amount of risk 

reduction being valued. This assumption has been shown to be reasonable provided 

the change in the risk being valued is within the range of risks evaluated in the 

underlying studies (Rowlatt et al., 1998).

 Voluntariness of risks evaluated: Although job-related mortality risks may differ in 

several ways from air pollution-related mortality risks, the most important 

difference may be that job-related risks are incurred voluntarily, or generally 

assumed to be, whereas air pollution-related risks are incurred involuntarily. Some 

evidence suggests that people will pay more to reduce involuntarily incurred risks 

than risks incurred voluntarily. If this is the case, WTP estimates based on wage-risk 

studies may understate WTP to reduce involuntarily incurred air pollution-related 

mortality risks.

 Sudden versus protracted death: A final important difference related to the nature of 

the risk may be that some workplace mortality risks tend to involve sudden, 

catastrophic events, whereas air pollution-related risks tend to involve longer 

periods of disease and suffering prior to death. Some evidence suggests that WTP to 
5-55

avoid a risk of a protracted death involving prolonged suffering and loss of dignity 

and personal control is greater than the WTP to avoid a risk (of identical magnitude) 

of sudden death. To the extent that the mortality risks addressed in this assessment 

are associated with longer periods of illness or greater pain and suffering than are 

the risks addressed in the valuation literature, the WTP measurements employed in 

the present analysis would reflect a downward bias.

 Self-selection and skill in avoiding risk: Recent research (Shogren and Stamland, 

2002) suggests that VSL estimates based on hedonic wage studies may overstate the 

average value of a risk reduction. This is based on the fact that the risk-wage tradeoff revealed in hedonic studies reflects the preferences of the marginal worker (i.e., 

that worker who demands the highest compensation for his risk reduction). This 

worker must have either a higher workplace risk than the average worker, a lower 

risk tolerance than the average worker, or both. However, the risk estimate used in 

hedonic studies is generally based on average risk, so the VSL may be upwardly 

biased because the wage differential and risk measures do not match.

 Baseline risk and age: Recent research (Smith, Pattanayak, and Van Houtven, 2006) 

finds that because individuals reevaluate their baseline risk of death as they age, the 

marginal value of risk reductions does not decline with age as predicted by some 

lifetime consumption models. This research supports findings in recent stated 

preference studies that suggest only small reductions in the value of mortality risk 

reductions with increasing age.

5.6.6.2 Nonfatal Myocardial Infarctions Valuation

We were not able to identify a suitable WTP value for reductions in the risk of nonfatal 

heart attacks. Instead, we use a COI unit value with two components: the direct medical costs 

and the opportunity cost (lost earnings) associated with the illness event. Because the costs 

associated with a myocardial infarction extend beyond the initial event itself, we consider costs 

incurred over several years. Using age-specific annual lost earnings estimated by Cropper and 

Krupnick (1990) and a 3% discount rate, we estimated a rounded present discounted value in 

lost earnings (in 2000$) over 5 years due to a myocardial infarction of $8,800 for someone 

between the ages of 25 and 44, $13,000 for someone between the ages of 45 and 54, and 

$75,000 for someone between the ages of 55 and 65. The rounded corresponding age-specific 

estimates of lost earnings (in 2000$) using a 7% discount rate are $7,900, $12,000, and $67,000, 

respectively. Cropper and Krupnick (1990) do not provide lost earnings estimates for 

populations under 25 or over 65. As such, we do not include lost earnings in the cost estimates 

for these age groups.

We found three possible sources in the literature of estimates of the direct medical 

costs of myocardial infarction, which provide significantly different values (see Table 5-11):
5-56

Table 5-11. Alternative Direct Medical Cost of Illness Estimates for Nonfatal Heart Attacksa

Study Direct Medical Costs (2006$) Over an x-Year Period, for x =

Wittels et al. (1990) $140,000b 5

Russell et al. (1998) $30,000c 5

Eisenstein et al. (2001) $64,000c 10

Russell et al. (1998) $38,000c 10

a All estimates rounded to two significant digits. Unrounded estimates in 2000$ are available in appendix J of the 

BenMAP user manual (Abt Associates, 2011).

b Wittels et al. (1990) did not appear to discount costs incurred in future years.

c Using a 3% discount rate. Discounted values as reported in the study.

 Wittels et al. (1990) estimated expected total medical costs of myocardial infarction 

over 5 years to be $51,000 (rounded in 1986$) for people who were admitted to the 

hospital and survived hospitalization. (There does not appear to be any discounting 

used.) This estimated cost is based on a medical cost model, which incorporated 

therapeutic options, projected outcomes, and prices (using “knowledgeable 

cardiologists” as consultants). The model used medical data and medical decision 

algorithms to estimate the probabilities of certain events and/or medical procedures 

being used. The authors note that the average length of hospitalization for acute 

myocardial infarction has decreased over time (from an average of 12.9 days in 1980 

to an average of 11 days in 1983). Wittels et al. used 10 days as the average in their 

study. It is unclear how much further the length of stay for myocardial infarction 

may have decreased from 1983 to the present. The average length of stay for ICD 

code 410 (myocardial infarction) in the year-2000 Agency for Healthcare Research 

and Quality (AHRQ) HCUP database is 5.5 days (AHRQ, 2000). However, this may 

include patients who died in the hospital (not included among our nonfatal 

myocardial infarction cases), and whose length of stay was therefore substantially 

shorter than it would be if they had not died.

 Eisenstein et al. (2001) estimated 10-year costs of $45,000 in rounded 1997$ (using 

a 3% discount rate) for myocardial infarction patients, using statistical prediction 

(regression) models to estimate inpatient costs. Only inpatient costs (physician fees 

and hospital costs) were included.

 Russell et al. (1998) estimated first-year direct medical costs of treating nonfatal 

myocardial infarction of $16,000 (in rounded 1995$) and $1,100 annually thereafter

for a 10-year period.

As noted above, the estimates from these three studies are substantially different, and 

we have not adequately resolved the sources of differences in the estimates. Because the 
5-57

wage-related opportunity cost estimates from Cropper and Krupnick (1990) cover a 5-year 

period, we used estimates for medical costs that similarly cover a 5-year period (i.e., estimates 

from Wittels et al. (1990) and Russell et al. (1998). We used a simple average of the two 5-year 

estimates, or rounded to $66,000, and added it to the 5-year opportunity cost estimate. The 

resulting estimates are given in Table 5-12.

Table 5-12. Estimated Costs Over a 5-Year Period of a Nonfatal Myocardial Infarction (in 

2006$)a

Age Group Opportunity Cost Medical Cost b Total Cost

0–24 $0 $85,000 $85,000

25–44 $11,000c $85,000 $96,000

45–54 $16,000c $85,000 $100,000

55–65 $91,000c $85,000 $180,000

> 65 $0 $85,000 $85,000

a All estimates rounded to two significant digits. Unrounded estimates in 2000$ are available in appendix J of the 

BenMAP user manual (Abt Associates, 2011).

b An average of the 5-year costs estimated by Wittels et al. (1990) and Russell et al. (1998).

c From Cropper and Krupnick (1990), using a 3% discount rate.

5.6.6 Hospital Admissions and Emergency Department Valuation

In the absence of estimates of societal WTP to avoid hospital visits/admissions for 

specific illnesses, we derive COI estimates for use in the benefits analysis. The International 

Classification of Diseases (WHO, 1977) code-specific COI estimates used in this analysis consist 

of estimated hospital charges and the estimated opportunity cost of time spent in the hospital 

(based on the average length of a hospital stay for the illness). We based all estimates of 

hospital charges and length of stays on statistics provided by the Agency for Healthcare 

Research and Quality’s Healthcare Utilization Project National Inpatient Sample (NIS) database 

(AHRQ, 2007). We estimated the opportunity cost of a day spent in the hospital as the value of 

the lost daily wage, regardless of whether the hospitalized individual is in the workforce. To 

estimate the lost daily wage, we divided the median weekly wage reported by the 2007 

American Community Survey (ACS) by five and deflated the result to year 2006$ using the CPI-U 

“all items” (Abt Associates, 2011). The resulting national average lost daily wage is $134. The 

total cost-of-illness estimate for an ICD code-specific hospital stay lasting n days, then, was the 

mean hospital charge plus $134 multiplied by n. In general, the mean length of stay has 

decreased since the 2000 database used in previous version of BenMAP while the mean 
5-58

hospital charge has increased. We provide the rounded unit values in 2000$ for the COI 

functions used in this analysis in Table 5-13.

Table 5-13. Unit Values for Hospital Admissions

End Point ICD Codes

Age Range

Mean Hospital 

Charge (2000$)

Mean Length 

of Stay (days)

Total Cost of Illness 

(unit value in 

min. max. 2000$)

HA, All Cardiovascular 390–429 18 64 $27,000 4.1 $27,000

HA, All Cardiovascular 390–429 65 99 $25,000 4.9 $25,000

HA, All Respiratory 460–519 65 99 $21,000 6.1 $21,000

HA, Asthma 493 0 64 $9,700 3.0 $10,000

HA, Chronic Lung 

Disease 

490–496 18 64 $13,000 3.9 $13,000

* All estimates rounded to two significant digits. Unrounded estimates in 2000$ are available in Appendix J of the 

BenMAP user manual (Abt Associates, 2011).

To value asthma emergency department visits, we used a simple average of two 

estimates from the health economics literature. The first estimate comes from Smith et al. 

(1997), who reported approximately 1.2 million asthma-related emergency department visits in 

1987, at a total cost of $186.5 million (1987$). The average cost per visit that year was $155; in 

2006$, that cost was $401 (using the CPI-U for medical care to adjust to 2006$). The second 

estimate comes from Stanford et al. (1999), who reported the cost of an average asthmarelated emergency department visit at $335, based on 1996–1997 data. A simple average of the 

two estimates yields a unit value of $368.

5.6.7 Minor Restricted Activity Days Valuation

No studies are reported to have estimated WTP to avoid a minor restricted activity day. 

However, Neumann et al. (1994) derived an estimate of willingness to pay to avoid a minor 

respiratory restricted activity day, using estimates from Tolley et al. (1986) of WTP for avoiding 

a combination of coughing, throat congestion and sinusitis. This estimate of WTP to avoid a 

minor respiratory restricted activity day is $38 (1990$), or about $62 (2006$). Although Ostro 

and Rothschild (1989) statistically linked ozone and minor restricted activity days, it is likely that 

most MRADs associated with ozone and PM2.5 exposure are, in fact, minor respiratory restricted 

activity days. For the purpose of valuing this health endpoint, we used the estimate of mean 

WTP to avoid a minor respiratory restricted activity day.
5-59

5.6.8 Growth in WTP Reflecting National Income Growth Over Time

Our analysis accounts for expected growth in real income over time. This is a distinct 

concept from inflation and currency year. Economic theory argues that WTP for most goods 

(such as environmental protection) will increase if real incomes increase. There is substantial 

empirical evidence that the income elasticity5 of WTP for health risk reductions is positive, 

although there is uncertainty about its exact value. Thus, as real income increases, the WTP for 

environmental improvements also increases. Although many analyses assume that the income 

elasticity of WTP is unit elastic (i.e., a 10% higher real income level implies a 10% higher WTP to 

reduce risk changes), empirical evidence suggests that income elasticity is substantially less 

than one and thus relatively inelastic. As real income rises, the WTP value also rises but at a 

slower rate than real income.

The effects of real income changes on WTP estimates can influence benefits estimates 

in two different ways: through real income growth between the year a WTP study was 

conducted and the year for which benefits are estimated, and through differences in income 

between study populations and the affected populations at a particular time. Empirical 

evidence of the effect of real income on WTP gathered to date is based on studies examining 

the former. The Environmental Economics Advisory Committee (EEAC) of the Science Advisory 

Board (SAB) advised EPA to adjust WTP for increases in real income over time but not to adjust 

WTP to account for cross-sectional income differences “because of the sensitivity of making 

such distinctions, and because of insufficient evidence available at present” (U.S. EPA-SAB, 

2000). An advisory by another committee associated with the SAB, the Advisory Council on 

Clean Air Compliance Analysis, has provided conflicting advice. While agreeing with “the 

general principle that the willingness to pay to reduce mortality risks is likely to increase with 

growth in real income” and that “[t]he same increase should be assumed for the WTP for

serious nonfatal health effects,” they note that “given the limitations and uncertainties in the 

available empirical evidence, the Council does not support the use of the proposed adjustments 

for aggregate income growth as part of the primary analysis” (U.S. EPA-SAB, 2004b). Until these 

conflicting advisories have been reconciled, EPA will continue to adjust valuation estimates to 

reflect income growth using the methods described below, while providing sensitivity analyses 

for alternative income growth adjustment factors.

Based on a review of the available income elasticity literature, we adjusted the valuation 

of human health benefits upward to account for projected growth in real U.S. income. Faced 

 5 Income elasticity is a common economic measure equal to the percentage change in WTP for a 1% change in 

income.
5-60

with a dearth of estimates of income elasticities derived from time-series studies, we applied 

estimates derived from cross-sectional studies in our analysis. Details of the procedure can be 

found in Kleckner and Neumann (1999). An abbreviated description of the procedure we used 

to account for WTP for real income growth between 1990 and 2020 is presented below.

Reported income elasticities suggest that the severity of a health effect is a primary 

determinant of the strength of the relationship between changes in real income and WTP. As 

such, we use different elasticity estimates to adjust the WTP for minor health effects, severe 

and chronic health effects, and premature mortality. Note that because of the variety of 

empirical sources used in deriving the income elasticities, there may appear to be 

inconsistencies in the magnitudes of the income elasticities relative to the severity of the 

effects (a priori one might expect that more severe outcomes would show less income elasticity 

of WTP). We have not imposed any additional restrictions on the empirical estimates of income 

elasticity. One explanation for the seeming inconsistency is the difference in timing of 

conditions. WTP for minor illnesses is often expressed as a short term payment to avoid a single 

episode. WTP for major illnesses and mortality risk reductions are based on longer term 

measures of payment (such as wages or annual income). Economic theory suggests that 

relationships become more elastic as the length of time grows, reflecting the ability to adjust 

spending over a longer time period. Based on this theory, it would be expected that WTP for 

reducing long term risks would be more elastic than WTP for reducing short term risks. We also 

expect that the WTP for improved visibility in Class I areas would increase with growth in real 

income. The relative magnitude of the income elasticity of WTP for visibility compared with 

those for health effects suggests that visibility is not as much of a necessity as health, thus, WTP 

is more elastic with respect to income. The elasticity values used to adjust estimates of benefits 

in 2020 are presented in Table 5-14.

Table 5-14. Elasticity Values Used to Account for Projected Real Income Growtha

Benefit Category Central Elasticity Estimate

Minor Health Effect 0.14

Severe and Chronic Health Effects 0.45

Premature Mortality 0.40

a Derivation of estimates can be found in Kleckner and Neumann (1999). COI estimates are not adjusted for 

income growth.

In addition to elasticity estimates, projections of real gross domestic product (GDP) and 

populations from 1990 to 2020 are needed to adjust benefits to reflect real per capita income 
5-61

growth. For consistency with the emissions and benefits modeling, we used national population 

estimates for the years 1990 to 1999 based on U.S. Census Bureau estimates (Hollman, Mulder, 

and Kallan, 2000). These population estimates are based on application of a cohort-component 

model applied to 1990 U.S. Census data projections (U.S. Bureau of Census, 2000). For the years 

between 2000 and 2020, we applied growth rates based on the U.S. Census Bureau projections 

to the U.S. Census estimate of national population in 2000. We used projections of real GDP 

provided in Kleckner and Neumann (1999) for the years 1990 to 2010.6 We used projections of 

real GDP (in chained 1996 dollars) provided by Standard and Poor’s (2000) for the years 2010 to 

2020.

7

Using the method outlined in Kleckner and Neumann (1999) and the population and 

income data described above, we calculated WTP adjustment factors for each of the elasticity 

estimates listed in Table 5-15. Benefits for each of the categories (minor health effects, severe 

and chronic health effects, premature mortality, and visibility) are adjusted by multiplying the 

unadjusted benefits by the appropriate adjustment factor. Note that, for premature mortality, 

we applied the income adjustment factor to the present discounted value of the stream of 

avoided mortalities occurring over the lag period. Because of a lack of data on the dependence 

of COI and income and a lack of data on projected growth in average wages, no adjustments are 

made to benefits based on the COI approach or to work loss days and worker productivity. This 

assumption leads us to underpredict benefits in future years because it is likely that increases in 

real U.S. income would also result in increased COI (due, for example, to increases in wages 

paid to medical workers) and increased cost of work loss days and lost worker productivity 

(reflecting that if worker incomes are higher, the losses resulting from reduced worker 

production would also be higher).

 6 U.S. Bureau of Economic Analysis, Table 2A—Real Gross Domestic Product (1997) and U.S. Bureau of Economic 

Analysis, The Economic and Budget Outlook: An Update, Table 4—Economic Projections for Calendar Years 1997 

Through 2007 (1997). Note that projections for 2007 to 2010 are based on average GDP growth rates between 

1999 and 2007. 7 In previous analyses, we used the Standard and Poor’s projections of GDP directly. This led to an apparent 

discontinuity in the adjustment factors between 2010 and 2011. We refined the method by applying the 

relative growth rates for GDP derived from the Standard and Poor’s projections to the 2010 projected GDP 

based on the Bureau of Economic Analysis projections.
5-62

Table 5-15. Adjustment Factors Used to Account for Projected Real Income Growtha

Benefit Category 2020

Minor Health Effect 1.07

Severe and Chronic Health Effects 1.22

Premature Mortality 1.20

a Based on elasticity values reported in Table 5-3, U.S. Census population projections, and projections of real GDP 

per capita.

5.7 Benefits Results

5.7.1 Benefits of Attaining Alternative Combinations of Primary PM2.5 Standards

Applying the impact and valuation functions described previously in this chapter to the 

estimated changes in PM2.5 yields estimates of the changes in physical damages (e.g., 

premature mortalities, cases of acute bronchitis and hospital admissions) and the associated 

monetary values for those changes. Not all known PM health effects could be quantified or 

monetized. The monetized value of these unquantified effects is represented by adding an 

unknown “B” to the aggregate total. The estimate of total monetized health benefits is thus 

equal to the subset of monetized PM-related health benefits plus B, the sum of the nonmonetized health and welfare benefits; this B represents both uncertainty and a bias in this 

analysis, as it reflects those benefits categories that we are unable quantify in this analysis.

Table 5-16 shows the population-weighted air quality change for the alternative 

standards averaged across the continental U.S. Tables 5-17 through 5-24 present the benefits 

results for the alternative combinations of primary PM2.5 standards. In analyzing the current 

15/35 standard (baseline), EPA determined that all counties would meet the 14/35 standard 

concurrently with meeting the existing 15/35 standard at no additional cost. Consequently, 

there are no incremental costs or benefits for 14/35, and no need to present an analysis of 

14/35. Figure 5-3 graphically displays the total monetized benefits of the proposed range of 

primary standard combinations (12/35 and 13/35) using alternative concentration-response 

functions at discount rates of 3% and 7%. Figure 5-4 graphically displays the cumulative 

distribution of total monetized benefits using the 2 epidemiology-derived and the 12 expertderived relationships between PM2.5 and mortality for 12/35 and 13/35.
5-63

Table 5-16. Population-Weighted Air Quality Change for Adults (30+) for Alternative 

Standards Relative to 15/35

Standard Population-Weighted Air Quality Change

13/35 0.0008 μg/m3

12/35 0.0206 μg/m3

11/35 0.0807 μg/m3

11/30 0.1228 μg/m3

5.7.2 Uncertainty in Benefits Results

Health benefits account for between 97 and 99% of total benefits depending on the 

PM2.5 mortality estimates used, in part because we are unable to quantify most of the nonhealth benefits. The next largest benefit is for reductions in chronic illness (nonfatal heart 

attacks), although this value is more than an order of magnitude lower than for premature 

mortality. Hospital admissions for respiratory and cardiovascular causes, MRADs and work loss 

days account for the majority of the remaining benefits. The remaining categories each account 

for a small percentage of total benefit; however, they represent a large number of avoided 

incidences affecting many individuals. A comparison of the incidence table to the monetary 

benefits table reveals that there is not always a close correspondence between the number of 

incidences avoided for a given endpoint and the monetary value associated with that endpoint. 

For example, we estimate almost 100 times more work loss days would be avoided than 

premature mortalities, yet work loss days account for only a very small fraction of total 

monetized benefits. This reflects the fact that many of the less severe health effects, while 

more common, are valued at a lower level than the more severe health effects. Also, some 

effects, such as hospital admissions, are valued using a proxy measure of WTP. As such, the true 

value of these effects may be higher than that reported in the tables above.

PM2.5 mortality benefits represent a substantial proportion of total monetized benefits 

(over 98% in this analysis), and these estimates have the following key assumptions and 

uncertainties.

 Implementation of this new air quality standard is expected to reduce emissions of 

directly emitted PM2.5, SO2, and NOx. We assume that all fine particles, regardless of 

their chemical composition, are equally potent in causing premature mortality. This 

is an important assumption, because PM2.5 produced varies considerably in 
5-64

composition across sources, but the scientific evidence is not yet sufficient to allow 

differential effects estimates by particle type.

 We assume that the health impact function for fine particles is linear within the 

range of ambient concentrations under consideration. Thus, the estimates include 

health benefits from reducing fine particles in areas with varied concentrations of 

PM2.5, including both regions that are in attainment with fine particle standard and 

those that do not meet the standard down to the lowest modeled concentrations.

Given that reductions in premature mortality dominate the size of the overall monetized 

benefits, more focus on uncertainty in mortality-related benefits gives us greater confidence in 

our uncertainty characterization surrounding total benefits.
5-65

Table 5-17. Estimated number of Avoided PM2.5 Health Impacts for Alternative Combinations 

of Primary PM2.5 Standards (Incremental to Attaining Current Suite of Primary 

PM2.5 Standards)

a

Health Effect

Alterative Combination of Standards

(95th percentile confidence interval)

13 μg/m3 Annual &

35 μg/m3 24-hrb

12 μg/m3 Annual &

35 μg/m3 24-hr

11 μg/m3 Annual &

35 μg/m3 24-hr

11 μg/m3 Annual &

30 μg/m3 24-hr

Non-fatal heart 

attacks

Peters et al. (2001)

(age >18)

11 320 1,300 1,900

(6–19) (80–550) (390–2,100) (590–3,200)

Pooled estimate of 4 

studies (age >18)

1 35 140 210

(1–3) (15–92) (64–330) (98–510)

Hospital admissions—

respiratory

(all ages)

3 98 430 620

(2–5) (51–150) (240–620) (350–0,890)

Hospital admissions—

cardiovascular

(age > 18)

3 95 400 580

(2–6) (43–170) (190–0,700) (280–1,000)

Emergency 

department visits for 

asthma

(age < 18)b

6 160 730 1,000

(2–13) (-29–340) (-56–1,500) (-79–2,100)

Acute bronchitis 

(ages 8–12) b

22 540 2,000 3,100

(7–48) (-120–1,200) (-260–4,200) (-400–6,400)

Lower respiratory 

symptoms

(ages 7–14)

290 6,900 25,000 39,000

(180–450) (2,700–11,000) (11,000–40,000) (17,000–61,000)

Upper respiratory 

symptoms

(asthmatics ages

9–11)

410 9,800 37,000 56,000

(220–710) (1,800–18,000) (9,200–64,000) (14,000–98,000)

Asthma exacerbation

(asthmatics ages

6–18)

410 24,000 89,000 140,000

(150–860) (0–180,000) (1,900–570,000) (2,900–870,000)

Lost work days 

(ages 18–65)

1,800 44,000 170,000 260,000

(1700–2100) (38,000–51,000) (150,000–200,000) (220,000–290,000)

Minor restrictedactivity days

(ages 18–65)

11,000 260,000 1,000,000 1,500,000

(9,500–12,000) (210,000–310,000) (840,000–1,200,000) (1,300,000–1,800,000)

a All incidence estimates are rounded to whole numbers with a maximum of two significant digits.

b The negative estimates at the 5th percentile confidence estimates for these morbidity endpoints reflect the 

statistical power of the study used to calculate these health impacts. These results do not suggest that reducing 

air pollution results in additional health impacts.
5-66

Table 5-18. Estimated Number of Avoided PM2.5-Related Deaths for Alternative 

Combinations of Primary PM2.5 Standards (Incremental to Attaining Current Suite 

of Primary PM2.5 Standards)

a

Alterative Combination of Standards

(95th percentile confidence interval)

13 μg/m3 Annual &

35 μg/m3 24-hr

12 μg/m3 Annual &

35 μg/m3 24-hr

11 μg/m3 Annual &

35 μg/m3 24-hr

11 μg/m3 Annual &

30 μg/m3 24-hr

Mortality impact functions derived from the epidemiology literature

Krewski et al. 

(2009)

11

(9–14)

280 1,100 1,700

(190–370) (790–1,400) (1,200–2,300)

Laden et al.

(2006)

27

(19–41)

730 2,900 4,500

(330–1100) (1,400–4,300) (2,200–6,700)

Woodruff et al. 

(1997)

(infant mortality)

0

(0–0)

1 3 4

(0–1) (1–5) (2–7)

Mortality impact functions derived from the PM2.5 Expert Elicitation (Roman et al., 2006)

Expert A 28

(11–55)

740 2,900 4,500

(55–1,500) (400–5,700) (620–8,900)

Expert B 22

(4–47)

590 2,300 3,600

(27–1,300) (160–5,000) (220–7,700)

Expert C 22

(12–37)

580 2,300 3,600

(140–1000) (670–3,900) (1100–6,100)

Expert D 15

(0–26)

410 1,600 2,500

(0–700) (0–2,700) (0–4,200)

Expert E 36

(23–55)

950 3,700 5,900

(370–1,500) (1,600–5,700) (2,600–9,000)

Expert F 20

(14–28)

530 2,100 3,300

(310–770) (1,300–3,000) (2,000–4,700)

Expert G 13

(0–24)

340 1,300 2,100

(0–640) (0–2,500) (0–3,800)

Expert H 16

(0–38)

420 1,700 2,600

(0–1100) (0–4,000) (0–6,200)

Expert I 22

(0–38)

570 2,300 3,500

(0–1000) (0–3,900) (0–6,100)

Expert J 18

(6–39)

470 1,800 2,900

(17–1100) (170–4,000) (270–6,300)

Expert K 3

(0–12)

72 270 420

(0–330) (0–1,200) (0–1,900)

Expert L 16

(0–29)

400 1,600 2,400

(0–790) (0–3,000) (0–4,700)

a All incidence estimates are rounded to whole numbers with a maximum of two significant digits.
5-67

Table 5-19. Estimated Monetized PM2.5 Health Impacts for Alternative Combinations of 

Primary PM2.5 Standards (Incremental to Attaining Current Suite of Primary PM2.5 

Standards) (Millions of 2006$, 3% discount rate)a

Health Effect

Alterative Combination of Standards

(95th percentile confidence interval)

13 μg/m3 Annual &

35 μg/m3 24-hr

12 μg/m3 Annual &

35 μg/m3 24-hr

11 μg/m3 Annual &

35 μg/m3 24-hr

11 μg/m3 Annual &

30 μg/m3 24-hr

Non-fatal heart attacks 

Peters et al. (2001)

(age >18)

$1.1

($0.19–$2.9)

$33 $130

($23–$330)

$200

($5.5–$82) ($34–$500)

Pooled estimate of 4 

studies

(age >18)

$0.13

($0.029–$0.43)

$3.7 $15

($3.5–$49)

$23

($0.85–$12) ($5.3–$75)

Hospital admissions—

respiratory

(all ages)

$0.081

($0.050–$0.11)

$2.4 $10

($6–$15)

$15

($1.5–$3.3) ($9–$21)

Hospital admissions—

cardiovascular 

(age > 18)

$0.11

($0.058–$0.19)

$3.2 $13

($7–$23)

$20

($1.7–$5.4) ($10–$33)

Emergency department 

visits for asthma (age < 18)

$0.0023

($0.000065–$0.0050)

$0.058 $0.27

($0.008–$0.58)

$0.38

($0.0016–$0.13) ($0.011–$0.81)

Acute bronchitis

(ages 8–12)b

$0.010

(-$0.00045–$0.028)

$0.24 $0.89

(-$0.040–$2.4)

$1.40

(-$0.011–$0.66) (-$0.062–$3.7)

Lower respiratory 

symptoms

(ages 7–14)

$0.0055

($0.0018–$0.011)

$0.13 $0.49

($0.16–$1.0)

$0.76

($0.044–$0.27) ($0.25–$1.5)

Upper respiratory 

symptoms

(asthmatics ages 9–11)

$0.012

($0.0028–$0.030)

$0.30 $1.1

($0.25–$2.7)

$1.7

($0.067–$0.74) ($0.38–$4.2)

Asthma exacerbation

(asthmatics ages 6–18)

$0.022

($0.0019–$0.058)

$1.3 $4.7

($0.18–$34)

$7.2

($0.047–$9.0) ($0.27–$51)

Lost work days

(ages 18–65)

$0.27

($0.24–$0.31)

$6.7 $26

($22–$29)

$39

($5.8–$7.5) ($34–$44)

Minor restricted-activity 

days

(ages 18–65)

$0.67

($0.35–$1.0)

$16.0 $64

($34–$96)

$96

($8.7–$25) ($51–$140)

a All estimates are rounded to two significant digits. Estimates do not include unquantified health benefits noted 

in Table 5-2 or Section 5.6.5 or welfare benefits noted in Chapter 6.

b The negative estimates at the 5th percentile confidence estimates for this morbidity endpoint reflects the 

statistical power of the study used to calculate these health impacts. These results do not suggest that reducing 

air pollution results in additional health impacts.
5-68

Table 5-20. Estimated Monetized PM2.5 Health Impacts for Alternative Combinations of 

Primary PM2.5 Standards (Incremental to Attaining Current Suite of Primary PM2.5 

Standards) (Millions of 2006$, 7% discount rate)a

Health Effect

Alterative Combination of Standards

(95th percentile confidence interval)

13 μg/m3 Annual & 

35 μg/m3 24-hr

12 μg/m3 Annual &

35 μg/m3 24-hr

11 μg/m3 Annual 

& 35 μg/m3 24-

hr

11 μg/m3 Annual &

30 μg/m3 24-hr

Non-fatal heart attacks

Peters et al. (2001)

(age >18)

$1.1

($0.180–$2.9)

$32 $130

($21–$320)

$190

($5.1–$81) ($32–$490)

Pooled estimate of 

4 studies

(age >18)

$0.12

($0.027–$0.42)

$3.6 $14

($3.2–$48)

$22

($0.79–$12) ($4.9–$74)

Hospital admissions—

respiratory (all ages)

$0.081

($0.050–$0.11)

$2.4 $10

($6–$15)

$15

($1.5–$3.3) ($9–$21)

Hospital admissions—

cardiovascular

(age > 18)

$0.11

($0.058–$0.19)

$3.2 $13

($7.0–$23)

$20

($1.7–$5.4) ($10–$33)

Emergency department 

visits for asthma

(age < 18)

$0.0023

($0.000065–$0.0050)

$0.058 $0.27

($0.008–$0.58)

$0.38

($0.0016–$0.13) ($0.011–$0.81)

Acute bronchitis

(ages 8–12)b

$0.010

(-$0.00045–$0.028)

$0.24 $0.89

(-$0.040–$2.4)

$1.40

(-$0.011–$0.66) (-$0.062–$3.7)

Lower respiratory 

symptoms

(ages 7–14)

$0.0055

($0.0018–$0.011)

$0.13 $0.49

($0.16–$1.0)

$0.76

($0.044–$0.27) ($0.25–$1.5)

Upper respiratory 

symptoms

(asthmatics ages 9–11)

$0.012

($0.0028–$0.030)

$0.30 $1.1

($0.25–$2.7)

$1.7

($0.067–$0.74) ($0.38–$4.2)

Asthma exacerbation

(asthmatics ages 6–18)

$0.022

($0.0019–$0.058)

$1.3 $4.7

($0.18–$34)

$7.2

($0.047–$9.0) ($0.27–$51)

Lost work days

(ages 18–65)

$0.27

($0.24–$0.31)

$6.7 $26

($22–$29)

$39

($5.8–$7.5) ($34–$44)

Minor restrictedactivity days (ages 18–

65)

$0.67

($0.35–$1.0)

$16.0 $64

($34–$96)

$96

($8.7–$25) ($51–$140)

a All estimates are rounded to two significant digits. Estimates do not include unquantified health benefits noted 

in Table 5-2 or Section 5.6.5 or welfare benefits noted in Chapter 6.

b The negative estimates at the 5th percentile confidence estimates for this morbidity endpoint reflects the 

statistical power of the study used to calculate these health impacts. These results do not suggest that reducing 

air pollution results in additional health impacts.
5-69

Table 5-21. Estimated Monetized PM2.5-Related Deaths for Alternative Combinations of 

Primary PM2.5 Standards (Incremental to Attaining Current Suite of Primary PM2.5 

Standards)(Millions of 2006$, 3% discount rate)a

Health Effect

Alterative Combination of Standards

(95th percentile confidence interval)

13 μg/m3 Annual &

35 μg/m3 24-hr

12 μg/m3 Annual &

35 μg/m3 24-hr

11 μg/m3 Annual &

35 μg/m3 24-hr

11 μg/m3 Annual &

30 μg/m3 24-hr

Mortality impact functions derived from the epidemiology literature

Krewski et al. (2009) $86

($8.0–$240)

$2,300 $9,000

($840–$25,000)

$14,000

($210–$6,300) ($1,300–$39,000)

Laden et al. (2006) $220

($19–$640)

$5,900 $23,000

($2,000–$67,000)

$36,000

($520–$17,000) ($3,200–$100,000)

Woodruff et al. 

(1997) (infant 

mortality)

$0.28

($0.023–$0.82)

$6.9 $26

($2.2–$78)

$39

($0.58–$20) ($3.3–$110)

Mortality impact functions derived from the PM2.5 Expert Elicitation (Roman et al., 2008)

Expert A $220

($13–$760)

$5,900 $23,000

($1,300–$78,000)

$37,000

($330–$20,000) ($2,100–$120,000)

Expert B $180

($6.0–$700)

$4,800 $19,000

($0,560–$73,000)

$29,000

($150–$19,000) ($0,780–$110,000)

Expert C $180

($13–$540)

$4,700 $18,000

($1,400–$57,000)

$29,000

($350–$14,000) ($2,200–$88,000)

Expert D $120

($3.5–$390)

$3,300 $13,000

($370–$41,000)

$20,000

($94–$10,000) ($580–$63,000)

Expert E $290

($25–$860)

$7,700 $30,000

($2,600–$89,000)

$47,000

($650–$23,000) ($4,000–$140,000)

Expert F $160

($14.0–$460)

$4,300 $17,000

($1,600–$49,000)

$26,000

($390–$12,000) ($2,400–$76,000)

Expert G $100

($0–$370)

$2,700 $11,000

($0–$39,000)

$17,000

($0–$9,800) ($0–$61,000)

Expert H $130

($0–$510)

$3,400 $13,000

($0–$53,000)

$21,000

($0–$13,000) ($0–$82,000)

Expert I $170

($6.2–$560)

$4,600 $18,000

($650–$58,000)

$28,000

($170–$15,000) ($1,000–$90,000)

Expert J $140

($6.7–$510)

$3,800 $15,000

($700–$53,000)

$23,000

($180–$13,000) ($1100–$82,000)

Expert K $23

($0–$140)

$580 $2,200

($0–$14,000)

$3,300

($0–$3,700) ($0–$22,000)

Expert L $130

($0.63–$450)

$3,300 $13,000

($48–$47,000)

$19,000

($14–$12,000) ($53–$72,000)

a Rounded to two significant figures. Estimates do not include unquantified health benefits noted in Table 5-2 or 

Section 5.6.5 or welfare benefits noted in Chapter 6.The reduction in premature fatalities each year accounts for 

over 98% of total monetized benefits in this analysis. Mortality risk valuation assumes discounting over the SABrecommended 20-year segmented lag structure.
5-70

Table 5-22. Estimated Monetized PM2.5-Related Deaths for Alternative Combinations of 

Primary PM2.5 Standards (Incremental to Attaining Current Suite of Primary PM2.5 

Standards) (Millions of 2006$, 7% discount rate)a

Health Effect

Alterative Combination of Standards

(95th percentile confidence interval)

13 μg/m3 Annual &

35 μg/m3 24-hr

12 μg/m3 Annual &

35 μg/m3 24-hr

11 μg/m3 Annual &

35 μg/m3 24-hr

11 μg/m3 Annual &

30 μg/m3 24-hr

Mortality impact functions derived from the epidemiology literature

Krewski et al. (2009) $77

($7.2–$210)

$2,100 $8,100

($750–$22,000)

$13,000

($190–$5,600) ($1,200–$35,000)

Laden et al. (2006) $200

($18–$580)

$5,300 $21,000

($1,800–$60,000)

$32,000

($460–$15,000) ($2,900–$94,000)

Woodruff et al. (1997)

(infant mortality)

$0.28

($0.023–$0.82)

$6.9 $26

($2.2–$78)

$39

($0.58–$20) ($3.3–$110)

Mortality impact functions derived from the PM2.5 Expert Elicitation (Roman et al., 2008)

Expert A $200

($11–$680)

$5,300 $21,000

($1,200–$71,000)

$33,000

($300–$18,000) ($1,900–$110,000)

Expert B $160

($5.4–$630)

$4,300 $17,000

($500–$66,000)

$26,000

($130–$17,000) ($0,700–$100,000)

Expert C $160

($12–$490)

$4,200 $17,000

($1,300–$51,000)

$26,000

($320–$13,000) ($2,000–$80,000)

Expert D $110

($3.2–$350)

$3,000 $12,000

($330–$37,000)

$18,000

($85–$9,300) ($520–$57,000)

Expert E $260

($22–$770)

$6,900 $27,000

($2,300–$80,000)

$43,000

($590–$20,000) ($3,600–$130,000)

Expert F $140

($13–$410)

$3,900 $15,000

($1,400–$44,000)

$24,000

($350–$11,000) ($2,200–$68,000)

Expert G $93

($0–$330)

$2,500 $9,700

($0–$35,000)

$15,000

($0–$8,900) ($0–$55,000)

Expert H $120

($0–$460)

$3,100 $12,000

($0–$47,000)

$19,000

($0–$12,000) ($0–$74,000)

Expert I $160

($5.6–$500)

$4,200 $16,000

($590–$52,000)

$26,000

($150–$13,000) ($920–$81,000)

Expert J $130

($6.0–$460)

$3,400 $13,000

($630–$47,000)

$21,000

($160–$12,000) ($980–$74,000)

Expert K $20

($0–$130)

$520 $2,000

($0–$13,000)

$3,000

($0–$3,400) ($0–$20,000)

Expert L $110

($0.57–$400)

$2,900 $11,000

($43–$42,000)

$17,000

($12–$11,000) ($48–$65,000)

a Rounded to two significant figures. Estimates do not include unquantified health benefits noted in Table 5-2 or 

Section 5.6.5 or welfare benefits noted in Chapter 6.The reduction in premature fatalities each year accounts for 

over 98% of total monetized benefits in this analysis. Mortality risk valuation assumes discounting over the SABrecommended 20-year segmented lag structure.
5-71

Table 5-23. Total Estimated Monetized Benefits of the for Alternative Combinations of 

Primary PM2.5 Standards (Incremental to Attaining Current Suite of Primary PM2.5 

Standards) (millions of 2006$)

a

Benefits Estimate

13 μg/m3 annual &

35 μg/m3 24-hour

12 μg/m3 annual &

35 μg/m3 24-hour

11 μg/m3 annual &

35 μg/m3 24-hour

11 μg/m3 Annual &

30 μg/m3 24-hr

Economic value of avoided PM2.5-related morbidities and premature deaths using PM2.5 mortality estimate 

from Krewski et al. (2009)

3% discount rate $88 + B $2,300 +B $9,200+B $14,000 +B

7% discount rate $79 + B $2,100 +B $8,300 +B $13,000 +B

Economic value of avoided PM2.5-related morbidities and premature deaths using PM2.5 mortality estimate 

from Laden et al. (2006)

3% discount rate $220 + B $5,900 +B $23,000 +B $36,000 +B

7% discount rate $200 + B $5,400 +B $21,000 +B $33,000 +B

a Rounded to two significant figures. The reduction in premature fatalities each year accounts for over 98% of 

total monetized benefits in this analysis. Mortality risk valuation assumes discounting over the SABrecommended 20-year segmented lag structure. Not all possible benefits are quantified and monetized in this 

analysis. B is the sum of all unquantified health and welfare benefits. Data limitations prevented us from 

quantifying these endpoints, and as such, these benefits are inherently more uncertain than those benefits that 

we were able to quantify.

Table 5-24. Regional Breakdown of Monetized Benefits Results

Region

Alterative Combination of Standards

13 μg/m3 annual &

35 μg/m3 24-hour

12 μg/m3 Annual &

35 μg/m3 24-hr

11 μg/m3 Annual &

35 μg/m3 24-hr

11 μg/m3 Annual &

30 μg/m3 24-hr

Easta 0% 27% 53% 43%

Californiab 98% 70% 44% 47%

Rest of 

West 2% 3% 3% 10%

a Includes Texas and those states to the north and east. Several recent rules such as MATS and CSAPR will have 

substantially reduced PM2.5 levels by 2020 in the East, thus few additional controls would be needed to reach 

12/35 or 13/35.

b For 12/35 and 13/35, the majority of benefits (occur in California because this highly populated area is where the 

most air quality improvement beyond 15/35 is needed to reach these levels.
 

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Figure 5-3. Estimated PM2.5-Related Premature Mortalities Avoided According to 

Epidemiology or Expert-Derived PM2.5 Mortality Risk Estimate for 12/35 and 13/35

$0

$1,000

$2,000

$3,000

$4,000

$5,000

$6,000

$7,000

$8,000

Krewski et al.

Laden et al.

Millions (2006$)

PM2.5 mortality benefits estimates derived from 2 epidemiology functions and 12 expert functions

 

3% Discount Rate

7% Discount Rate

$0

$50

$100

$150

$200

$250

$300

Krewski et al.

Laden et al.

Millions (2006$)

PM2.5 mortality benefits estimates derived from 2 epidemiology functions and 12 expert functions

 

3% Discount Rate

7% Discount Rate
5-73

Figure 5-4. Total Monetized Benefits Using 2 Epidemiology-Derived and 12-Expert Derived 

Relationships Between PM2.5 and Premature Mortality for 12/35 and 13/35

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

$0 $1 $2 $3 $4 $5 $6 $7 $8 $9 $10 $11 $12 $13 $14 $15 $16 $17 $18 $19 $20

Cumulative Percentage of Monetized Benefits

Cumulative Percentage of Monetized Benefits (Billions of 2006$)

 

 

Krewski et al.

Laden et al.

Expert A

Expert B

Expert C

Expert D

Expert E

Expert F

Expert G

Expert H

Expert I

Expert J

Expert K

Expert L

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

$0.0 $0.1 $0.2 $0.3 $0.4 $0.5 $0.6 $0.7 $0.8 $0.9 $1.0

Cumulative Percentage of Monetized Benefits

Cumulative Percentage of Monetized Benefits (Billions of 2006$)

 

 

Krewski et al.

Laden et al.

Expert A

Expert B

Expert C

Expert D

Expert E

Expert F

Expert G

Expert H

Expert I

Expert J

Expert K

Expert L
5-74

5.7.3 Estimated Life Years Gained Attributable to Reduced PM2.5 Exposure and Percent of 

Total Mortality

In their 2008 review of EPA’s approach to estimating ozone-related mortality benefits, 

NRC indicated, “EPA should consider placing greater emphasis on reporting decreases in agespecific death rates in the relevant population and develop models for consistent calculation of 

changes in life expectancy and changes in number of deaths at all ages” (NRC, 2008). In 

addition, NRC previously noted in an earlier report that “[f]rom a public-health perspective, lifeyears lost might be more relevant than annual number of mortality cases” (NRC, 2002). This 

advice is consistent with that of the HES, which agreed that “...the interpretation of mortality 

risk results is enhanced if estimates of lost life-years can be made” (U.S. EPA-SAB, 2004a). To 

address these recommendations, we estimate the number of life years gained and the 

reduction in the percentage of all deaths attributable to PM2.5 resulting from attainment of the 

alternative combinations of primary PM2.5 standards. EPA included similar estimates of life 

years gained in a previous assessment of PM2.5 benefits (U.S. EPA, 2006a, 2011a), the latter of 

which was peer reviewed by the HES (U.S. EPA-SAB, 2010a).

Because changes in life years and changes in life expectancy at birth are frequently 

conflated, it is important to distinguish these two very different metrics. Life expectancy varies 

by age. CDC defines life expectancy as the “average number of years of life remaining for 

persons who have attained a given age” (CDC, 2011). In other words, changes in life expectancy 

refer to an average change for the entire population, and refer to the future. Over the past 50 

years, average life expectancy at birth in the U.S. has increased by 8.4 years (CDC, 2001). Life 

years, on the other hand, measure the amount of time that an individual loses if they die before 

the age of their life expectancy. Life years refer to individuals, and refer to the past, e.g., when 

the individual has already died. For example, life expectancy at birth was estimated in 2007 to 

be 77.9 years for an average person born in the U.S., but for people surviving to age 60, 

estimated life expectancy is 82.5 years (i.e., 4.6 years more than life expectancy at birth) (CDC, 

2011). If a 60-year old individual dies, we estimate about that this individual would lose about

22.5 years of life (i.e., the average population life expectancy for an individual of this age minus 

this person’s age at death).

In this analysis, we use the same general approach as Hubbell (2006) and Fann et al. 

(2012a) for estimating potential life years gained by reducing exposure to PM2.5 in adult 

populations. We have not estimated the change in average life expectancy at birth in this RIA. 

Hubbell (2006) estimated that reducing exposure to PM2.5 from air pollution regulations result 

in an average gain of 15 years of life for those adults prematurely dying from PM2.5 exposure. In
5-75

contrast, Pope et al. (2009) estimated changes in average life expectancy at birth over a twenty 

year period, finding that reducing exposure to air pollution increased average life expectancy at 

birth by approximately 7 months, which was 15% of the overall increase in life expectancy at 

birth from 1980 through 2000. These results are not inconsistent because they are reporting 

different metrics. Because life expectancy is an average of the entire population (including 

those who will not die from PM exposure as well as those who will), average life expectancy 

changes associated with PM exposure will always be significantly smaller than the average 

number of life years lost by an individual who is projected to die prematurely from PM 

exposure.

To calculate the potential distribution of life years gained for populations of different 

ages, we use standard life tables available from the CDC (2003) and the following formula:

Total Life Years = ∑ LEi × Mi n

i=1 (5-2)

where LEi is the remaining life expectancy for age interval i, Mi is the change in number of 

deaths in age interval i, and n is the number of age intervals. We binned the life year results by 

age range and calculated the average per life lost.

When we estimate the number of avoided premature deaths attributed to changes in 

PM2.5 exposure in 2020, we apply risk coefficients estimated for all adult populations in 

conjunction with age-specific mortality rates. That is, we apply risk coefficients that do not vary 

by age, but use baseline mortality rates do. Because mortality rates for younger populations are 

much lower than mortality rates for older populations, most but not all, of the avoided deaths 

tend to be in older populations. By comparing the projected age distribution of the avoided 

premature deaths with the age distribution of life years gained, we observed that about half of 

the deaths occur in populations age 75-99, but half of the life years would occur in populations 

younger than 65. This is because the younger populations have the potential to lose more life 

years per death than older populations based on changes in PM2.5 exposure in 2020. On 

average, we estimate that the average individual who would otherwise have died prematurely 

from PM exposure would gain 16 additional years of life.

When calculating changes in life years, we assume that the life expectancy at birth of 

those dying from PM2.5 exposure is the same as the general population. In reference to the 

most recent Six Cities extended analysis by Laden et al. (2006), Krewski et al. (2009) notes that 

“[w]hether PM2.5 exposure was modeled as the annual average in the year of death or as the 

average over the entire follow-up period, it had similar effects on mortality. The results from 
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the study suggest that since PM2.5 exposure may affect sensitive individuals with preexisting 

conditions and play a role in the development of chronic disease, as exposure declines so may 

the excess mortality related to it.” For this reason, we believe that this is a reasonable 

assumption.

In addition, this analysis includes an estimate of the percentage of all-cause mortality 

attributed to reduced PM2.5 exposure in 2020 as a result of the illustrative control strategies. 

The percentage of premature PM2.5-related mortality is calculated by dividing the number of 

excess deaths estimated for each alternative standard by the total number of deaths in each 

county. We have also binned these results by age range.

Tables 5-25 and 5-26 summarize the estimated number of life years gained and the 

reduction in the percentage of all-cause mortality attributable to reduced PM2.5 exposure in 

2020 by age range for 12/35. Figure 5-5 bins the potential life years gained and avoided 

premature deaths into age ranges for 12/35 for comparison. The number of life years gained 

and avoided mortalities would be similar across various combinations of standards on a relative 

basis. Because we assume that there is a “cessation” lag between PM exposures and the 

reduction in the risk of premature death, there is uncertainty regarding the specific ages that 

people die relative to the change in exposure. While the structure of the lag is uncertain, some 

studies suggest that most of the premature deaths are avoided within the first three years after 

the change in exposure, while others are unable to find a critical window of exposure (U.S. EPA, 

2004c; Schwartz, 2008; Krewski et al. 2009). These studies did not examine whether the 

cessation lag was modified by either age of exposure or cumulative lifetime exposure.
5-77

Table 5-25. Sum of Life Years Gained by Age Range from Changes in PM2.5 Exposure in 2020 

for 12/35a,b

Age Rangeb

Krewski et al. (2009) Risk 

Coefficient c

Laden et al. (2006)

Risk Coefficient

25–29 — 420

30–34 140 370

35–44 410 1,000

45–54 690 1,800

55–64 1,100 2,700

65–74 1,100 2,800

75–84 740 1,900

85–99 350 880

Total life years gained 4,500 12,000

Average life years gained per individual 16.0 16.4

a Estimates rounded to two significant figures.

b Because we assume that there is a “cessation” lag between PM exposures and the reduction in the risk of 

premature death, there is uncertainty regarding the specific ages that people die relative to the change in 

exposure.

c The youngest age in the population cohort of this study is 30.
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Figure 5-5a. Distribution of Estimated Avoided Premature Deaths by the Age at which these 

Populations were Exposed in 2020 for 12/35 a

Figure 5-5b. Distribution of Estimated Life Years Gained by the Age at which these 

Populations were Exposed in 2020 for 12/35 a

a As shown in these charts, slightly more than half of the avoided premature deaths occur in populations age 75-

99, but slightly more than half of the avoided life years occur in populations age <65 due to the fact that the 

younger populations would lose more life years per death than older populations. Results would be similar for 

other standard levels on a percentage basis. Because we assume that there is a “cessation” lag between PM 

exposures and the reduction in the risk of premature death, there is uncertainty regarding the specific ages that 

people die relative to the change in exposure.

b The youngest age in the population cohort of this study used to estimate PM2.5 mortality incidence is 30.

Age

30-34 Age

35-44 Age

45-54

Age

55-64

Age 

65-74 Age 

75-84

Age 

85-99

Avoided Premature Deaths using 

Krewski et al. (2009) b

Age

25-29

Age

30-34 Age

35-44

Age

45-54

Age

55-64

Age

65-74 Age

75-84

Age

85-99

Avoided Premature Deaths 

using Laden et al. (2006)

Age 

30-34

Age

35-44

Age

45-54

Age

55-64

Age

65-74

Age

75-84

Age

85-99

Life Years Gained using Krewski 

et al. (2009) b

Age

25-29 Age 

30-34

Age

35-44

Age

45-54

Age

55-64

Age

65-74

Age

75-84

Age

85-99

Life Years Gained using Laden 

et al. (2006)
5-79

Table 5-26. Estimated Reduction the Percentage of All-Cause Mortality Attributable to PM2.5

for 12/35 from Changes in PM2.5 Exposure in 2020a,b

Age Rangeb Krewski et al. (2009) Risk Coefficientc Laden et al. (2006) Risk Coefficient

25–29 — 0.036% 

30–34 0.014% 0.035% 

35–44 0.013% 0.033% 

45–54 0.013% 0.034% 

55–64 0.012% 0.031% 

65–74 0.011% 0.028% 

75–84 0.010% 0.026% 

85–99 0.010% 0.025% 

a Rounded to two significant figures. Results would be similar for other standard levels on a percentage basis.

b Because we assume that there is a “cessation” lag between PM exposures and the reduction in the risk of 

premature death, there is uncertainty regarding the specific ages that people die relative to the change in 

exposure.

c The youngest age in the population cohort of this study is 30.

5.7.4 Analysis of Mortality Impacts at Various Concentration Benchmarks

In this analysis, we estimate the number of avoided PM2.5-related deaths occurring 

down to various PM2.5 concentration benchmarks, including the Lowest Measured Level (LML) 

of each long-term PM2.5 mortality study. We include this sensitivity analysis because 

assessments quantifying PM2.5 related health impacts generally find that cases of avoided 

mortality represent the majority of the monetized benefits. This analysis is one of several 

sensitivities that EPA has historically performed that characterize the uncertainty associated 

with the PM-mortality relationship and the economic value of reducing the risk of premature 

death (Roman et al., 2008; U.S. EPA, 2006a, 2011a; Mansfield, 2009).

Based on our review of the current body of scientific literature, EPA estimated PMrelated mortality without applying an assumed concentration threshold. The PM ISA (U.S. EPA, 

2009b), which was reviewed by EPA’s Clean Air Scientific Advisory Committee (U.S. EPA-SAB, 

2009a; U.S. EPA-SAB, 2009b), concluded that the scientific literature consistently finds that a 

no-threshold log-linear model most adequately portrays the PM-mortality concentrationresponse relationship while also recognizing potential uncertainty about the exact shape of the 
5-80

concentration-response function.8 Consistent with this finding, we incorporated a LML 

assessment, which is a method EPA has employed in several recent RIAs (U.S. EPA, 2010g, 

2011c, 2011d). In addition, we have incorporated an assessment using specific concentration 

benchmarks identified in EPA’s Policy Assessment for Particulate Matter (U.S. EPA, 2011b).

This approach summarizes the distribution of avoided PM2.5-related mortality impacts 

according to the baseline (i.e., pre-rule) annual mean PM2.5 levels at which populations are 

exposed and the minimum observed air quality level of each long-term cohort study we use to 

quantify mortality impacts. In general, our confidence in the estimated number of premature 

deaths diminishes as we estimate these impacts in locations where PM2.5 levels are below this 

level. This interpretation is consistent with the Policy Assessment (U.S. EPA, 2011b) and advice 

from CASAC during their peer review (U.S. EPA-SAB, 2010d). In general, we have greater

confidence in risk estimates based on PM2.5 concentrations where the bulk of the data reside

and somewhat less confidence where data density is lower. However, there are uncertainties 

inherent in identifying any particular point at which our confidence in reported associations 

becomes appreciably less.

As noted in the preamble to the proposed rule, the Policy Assessment (U.S. EPA, 2011b) 

concludes that the range from the 25th to 10th percentiles of the air quality data used in the 

epidemiology studies is a reasonable range below which we have appreciably less confidence in 

the associations observed in the epidemiological studies.

Although these types of concentration benchmark analyses (e.g., 25th percentile, 10th

percentile, and LML) provide some insight into the level of uncertainty in the estimated PM2.5 

mortality benefits, EPA does not view these concentration benchmarks as a concentration 

threshold. The central benefits estimates reported in this RIA reflect a full range of modeled air 

quality concentrations. In reviewing the Policy Assessment, CASAC confirmed that “[a]lthough 

there is increasing uncertainty at lower levels, there is no evidence of a threshold (i.e., a level 

below which there is no risk for adverse health effects)” (U.S. EPA-SAB, 2010d). In addition, in 

reviewing the Costs and Benefits of the Clean Air Act (U.S. EPA, 2011a), the HES noted that 

“[t]his [no-threshold] decision is supported by the data, which are quite consistent in showing 

effects down to the lowest measured levels. Analyses of cohorts using data from more recent 

years, during which time PM concentrations have fallen, continue to report strong associations 

with mortality” (U.S. EPA-SAB, 2010a). Therefore, the best estimate of benefits includes 

 8 For a summary of the scientific review statements regarding the lack of a threshold in the PM2.5-mortality 

relationship, see the Technical Support Document (TSD) entitled Summary of Expert Opinions on the Existence 

of a Threshold in the Concentration-Response Function for PM2.5-related Mortality (U.S. EPA, 2010f).
5-81

estimates below and above these concentration benchmarks but uncertainty is higher in health 

benefits estimated at lower concentrations, with the lowest confidence below the LML. 

Estimated health impacts reflecting air quality improvements below and above these 

concentration benchmarks are appropriately included in the total benefits estimate. In other 

words, our confidence in the estimated benefits above these concentration benchmarks should 

not imply an absence of confidence in the benefits estimated below these concentration 

benchmarks.

We estimate that most of the avoided PM-related impacts we estimate in this analysis 

occur among populations exposed at or above the LML of the Laden et al. (2006) study, while a 

majority of the impacts occur at or above the LML of the Krewski et al. (2009) study. We show 

the estimated reduction in incidence of premature mortality above and below the LML of these 

studies in Tables 5-27 and 5-28, and we graphically display the distribution of PM2.5-related 

mortality impacts for 12/35 and 13/35 in Figures 5-6 and 5-7. When interpreting these LML 

graphs, it is important to understand that the plots illustrate the avoided PM2.5 deaths

estimated to occur from PM2.5 reductions in the baseline air quality simulation in which we 

assume that 15/35 is already met. When simulating attainment with alternative standards, we 

do not adjust the PM2.5 concentration in every 12km grid cell to equal the alternative standard. 

Instead, we adjust the design value at the monitor to equal the alternative standard and 

simulate how that adjustment would be reflected in the surrounding grid cells. As such, there 

may be a small number of grid cells with concentrations greater than 15 μg/m3 in the baseline 

even though all monitors meet an annual standard at 15 μg/m3. Specifically, there is one grid 

cell in San Bernardino County with a baseline concentration of 16.4 μg/m3, which falls in the 16 

to 17 μg/m3 bin. This one grid cell is highly populated and has a relatively high percentage of 

the avoided premature mortalities because this area received the most air quality improvement 

from the control strategies to reach 12/35 and 13/35. In addition, several recent rules such as 

the Mercury and Air Toxics Standard (MATS) and the Cross-State Air Pollution Rule (CSAPR) will 

have substantially reduced PM2.5 levels by 2020 in the East, thus few additional controls would 

be needed to reach 12/35 or 13/35 in the East.

It is important to note that these estimated benefits reflect specific control measures 

and emission reductions that are needed to lower PM2.5 concentrations for monitors projected 

to exceed the alternative standard analyzed. The result is that air quality will improve in 

counties that exceed the alternative standards as well as surrounding areas that do not exceed 

the alternative standards. It is not possible to apply controls that only reduce PM2.5 at the 

monitor without affecting surrounding areas. In order to make a direct comparison between 
5-82

the benefits and costs of these control strategies, it is appropriate to include all the benefits 

occurring as a result of the control strategies applied.

We estimate benefits using modeled air quality data with 12km grid cells, which is 

important because the grid cells are smaller than counties and PM2.5 concentrations vary 

spatially within a county. Some grid cells in a county can be below the level of the alternative 

standard even though the highest monitor value is above the alternative standard. Thus, 

emission reductions lead to benefits in grid cells that are below the alternative standards even 

within a county with a monitor that exceeds the alternative standard. We have not estimated 

the fraction of benefits that occur only in counties that exceed the alternative standards.

Table 5-27. Estimated Reduction in Incidence of Adult Premature Mortality Occurring Above 

and Below the Lowest Measured Levels in the Underlying Epidemiology Studies 

for 12/35 and 13/35a

Study and Lowest Measured Level (LML)

Total Reduced 

Mortality Incidence

Allocation of Reduced Mortality Incidence

Below LML At or Above LML

12/35

Krewski et al. (2009) 5.8 μg/m3 280 23 260

Laden et al. (2006) 10 μg/m3 730 360 370

13/35

Krewski et al. (2009) 5.8 μg/m3 11 1 9 

Laden et al. (2006) 10 μg/m3 27 10 17 

a Mortality incidence estimates are rounded to whole numbers and two significant digits, so estimates may not 

sum across columns. It is important to emphasize that although we have lower levels of confidence in levels 

below the LML for each study, the scientific evidence does not support the existence of a level below which 

health effects from exposure to PM2.5 do not occur.
5-83

Table 5-28. Percentage of Avoided Premature Deaths Occurring At or Above the Lowest 

Measured Levels in the Underlying Epidemiology Studies for each Alternative 

Combination of Primary PM2.5 Standardsa

Study and Lowest Measured Level (LML) 13/35 12/35 11/35 11/30

Krewski et al. (2009) 5.8 μg/m3 89% 92% 95% 93%

Laden et al. (2006) 10 μg/m3 62% 51% 46% 32%

a It is important to emphasize that although we have lower levels of confidence in levels below the LML for each 

study, the scientific evidence does not support the existence of a level below which health effects from exposure 

to PM2.5 do not occur.

While the LML of each study is important to consider when characterizing and 

interpreting the overall level PM2.5-related co-benefits, as discussed earlier in this chapter, EPA 

believes that both cohort-based mortality estimates are suitable for use in air pollution health 

impact analyses. When estimating PM-related premature deaths avoided using risk coefficients 

drawn from the Laden et al. (2006) analysis of the Harvard Six Cities and the Krewski et al.

(2009) analysis of the ACS cohorts there are innumerable other attributes that may affect the 

size of the reported effect estimates—including differences in population demographics, the 

size of the cohort, activity patterns and particle composition among others. The LML 

assessment presented here provides a limited representation of one key difference between 

the two studies.
5-84

Of total PM2.5-Related deaths avoided for 12/35:

92% occur among populations exposed to PM2.5 levels at or above the LML of the Krewski et al. (2009) study.

51% occur among populations exposed to PM2.5 levels at or above the LML of the Laden et al. (2006) study.

Of total PM2.5-Related deaths avoided for 13/35:

89% occur among populations exposed to PM2.5 levels at or above the LML of the Krewski et al. (2009) study.

62% occur among populations exposed to PM2.5 levels at or above the LML of the Laden et al. (2006) study.

Figure 5-6. Number of Premature PM2.5-related Deaths Avoided for 12/35 and 13/35 

According to the Baseline Level of PM2.5 and the Lowest Measured Air Quality Levels of Each 

Mortality Study

0%

5%

10%

15%

20%

25%

<1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12 12-13 13-14 14-15 15-16 16-17 17-18 18-19 19-20

Percentage of Avoided PM2.5Mortalities

Baseline Annual Mean PM2.5 Level (μg/m3)

 

12/35

13/35

LML of Laden et 

al. (2006) study

LML of Krewski et 

al. (2009) study
5-85

Of total PM2.5-Related deaths avoided for 12/35:

92% occur among populations exposed to PM2.5 levels at or above the LML of the Krewski et al. (2009) study.

51% occur among populations exposed to PM2.5 levels at or above the LML of the Laden et al. (2006) study.

Of total PM2.5-Related deaths avoided for 13/35:

89% occur among populations exposed to PM2.5 levels at or above the LML of the Krewski et al. (2009) study.

62% occur among populations exposed to PM2.5 levels at or above the LML of the Laden et al. (2006) study.

Figure 5-7. Number of Premature PM2.5-related Deaths Avoided for 12/35 According to the 

Baseline Level of PM2.5 and the Lowest Measured Air Quality Levels of Each Mortality Study

5.7.5 Additional Sensitivity Analyses

The details of these sensitivity analyses are provided in appendix 5B, and summarized 

here. The use of an alternate lag structure would change the PM2.5-related mortality benefits 

discounted at 3% discounted by between 10% and –27%; when discounted at 7%, these 

benefits change by between 22% and −52%. When applying higher and lower income growth 

adjustments, the monetary value of PM2.5-related premature mortality changes between 33% 

and −14%; the value of acute endpoints changes between 8% and −4%. Using the updated costof-illness functions for hospital admissions, the rounded estimates of total monetized benefits 

do not change, but the monetary value of respiratory hospital admissions increases 3.4% and 

cardiovascular hospital admissions increase 2.1%. These results on a percentage basis would be 

similar for alternative combinations of standards.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Cumulative percentage of avoided PM Mortalities

Baseline Annual Mean PM2.5 Level (μg/m3)

 

 

12/35

13/35

LML of Krewski et 

al. (2009) study

LML of Laden et al. 

(2006) study
5-86

5.8 Discussion

This analysis demonstrates the potential for significant health benefits of the illustrative 

emission controls applied to simulate attainment with the alternative combination of primary 

PM2.5 standards. We estimate that by 2020 the proposed standards would have reduced the 

number of PM2.5-related premature mortalities and produce substantial non-mortality benefits. 

This rule promises to yield significant welfare impacts as well, though the quantification of 

those endpoints in this RIA is incomplete. Even considering the quantified and unquantified 

uncertainties identified in this chapter, we believe that the implementing the proposed 

standard would have substantial public health benefits that outweigh the costs.

Inherent in any complex RIA such as this one are multiple sources of uncertainty. Some 

of these we characterized through our quantification of statistical error in the concentration 

response relationships and our use of the expert elicitation-derived PM2.5 mortality functions. 

Others, including the projection of atmospheric conditions and source-level emissions, the 

projection of baseline morbidity rates, incomes and technological development are 

unquantified. When evaluated within the context of these uncertainties, the health impact and 

monetized benefits estimates in this RIA can provide useful information regarding the public 

health benefits associated with a revised PM NAAQS.

There are important differences worth noting in the design and analytical objectives of 

NAAQS RIAs compared to RIAs for implementation rules, such as the recent MATS rule (U.S. 

EPA, 2011d). The NAAQS RIAs illustrate the potential costs and benefits of attaining a revised

air quality standard nationwide based on an array of emission control strategies for different 

sources, incremental to implementation of existing regulations and controls needed to attain 

current standards. In short, NAAQS RIAs hypothesize, but do not predict, the control strategies 

that States may choose to enact when implementing a revised NAAQS. The setting of a NAAQS 

does not directly result in costs or benefits, and as such, NAAQS RIAs are merely illustrative and 

are not intended to be added to the costs and benefits of other regulations that result in 

specific costs of control and emission reductions. By contrast, the emission reductions from

implementation rules are generally for specific, well-characterized sources, such as the recent 

MATS rule (U.S. EPA, 2011d). In general, EPA is more confident in the magnitude and location of 

the emission reductions for implementation rules. As such, emission reductions achieved under 

promulgated implementation rules such as MATS have been reflected in the baseline of this

NAAQS analysis. Subsequent implementation rules will be reflected in the baseline for the next 

PM NAAQS review. For this reason, the benefits estimated provided in this RIA and all other 

NAAQS RIAs should not be added to the benefits estimated for implementation rules.
5-87

In setting the NAAQS, EPA considers that PM2.5 concentrations vary over space and time. 

While the standard is designed to limit concentrations at the highest monitor in an area, it is 

understood that emission controls put in place to meet the standard at the highest monitor will 

simultaneously result in lower PM2.5 concentrations throughout the entire area. In fact, the 

Quantitative Risk and Exposure Assessment for Particulate Matter (U.S. EPA, 2010b) shows how 

different standard levels would affect the entire distribution of PM2.5 concentrations, and thus 

people’s exposures and risk, across urban areas. For this reason, it is inappropriate to use the 

NAAQS level as a bright line for health effects.

The NAAQS are not set at levels that eliminate the risk of air pollution completely.

Instead, the Administrator sets the NAAQS at a level requisite to protect public health with an 

adequate margin of safety, taking into consideration effects on susceptible populations based 

on the scientific literature. The risk analysis prepared in support of this PM NAAQS reported 

risks below these levels, while acknowledging that the confidence in those effect estimates is 

higher at levels closer to the standard (U.S. EPA, 2010b). While benefits occurring below the 

standard may be somewhat more uncertain than those occurring above the standard, EPA 

considers these to be legitimate components of the total benefits estimate. Though there are 

greater uncertainties at lower PM2.5 concentrations, there is no evidence of a threshold in 

PM2.5-related health effects in the epidemiology literature. Given that the epidemiological 

literature in most cases has not provided estimates based on threshold models, there would be 

additional uncertainties imposed by assuming thresholds or other non-linear concentrationresponse functions for the purposes of benefits analysis.

5.9 References

Abbey, David E et al. 1995. “Chronic Respiratory Symptoms Associated with Estimated LongTerm Ambient Concentrations of Fine Particulates less than 2.5 Microns in aerodynamic 

diameter (PM2.5) and Other Air Pollutants.” Journal of Exposure Analysis and 

Environmental Epidemiology 5(2): 137-158.

Abbey, D.E., N. Nishino, W.F. McDonnell, R.J. Burchette, S.F. Knutsen, W. Lawrence Beeson, and 

J.X. Yang. 1999. “Long-term inhalable particles and other air pollutants related to 

mortality in nonsmokers.” American Journal of Respiratory and Critical Care Medicine

159(2):373-382.

Abt Associates, Inc. 2011. BenMAP User’s Manual Appendices. Prepared for U.S. Environmental 

Protection Agency Office of Air Quality Planning and Standards. Research Triangle Park, 

NC. September. Available on the Internet at <

http://www.epa.gov/air/benmap/models/BenMAPAppendicesSeptember2011.pdf>.
5-88

Abt Associates, Inc. 2010. Environmental Benefits and Mapping Program (Version 4.0). 

Bethesda, MD. Prepared for U.S. Environmental Protection Agency Office of Air Quality 

Planning and Standards. Research Triangle Park, NC. Available on the Internet at 

<http://www.epa.gov/air/benmap>.

Adams PF, Hendershot GE, Marano MA. 1999. “Current Estimates from the National Health 

Interview Survey, 1996.” Vital Health Stat 10(200):1-212.

Agency for Healthcare Research and Quality (AHRQ). 2000. HCUPnet, Healthcare Cost and 

Utilization Project. Rockville, MD. Available on the Internet at 

<http://hcupnet.ahrq.gov>.

Agency for Healthcare Research and Quality (AHRQ). 2007. HCUPnet, Healthcare Cost and 

Utilization Project. Rockville, MD. Available on the Internet at 

<http://hcupnet.ahrq.gov>.

American Lung Association (ALA). 1999. Chronic Bronchitis. Available on the Internet at 

<http://www.lungusa.org/diseases/lungchronic.html>.

American Lung Association (ALA). 2002. Trends in Asthma Morbidity and Mortality. American 

Lung Association, Best Practices and Program Services, Epidemiology and Statistics Unit.

Available on the Internet at <http://www.lungusa.org/data/asthma/ASTHMAdt.pdf>.

American Lung Association (ALA). 2010a. Trends in COPD (Chronic Bronchitis and Emphysema): 

Morbidity and Mortality. American Lung Association Epidemiology and Statistics Unit

Research and Program Services Division. February. Table 4. Based on NHIS data (CDC,

2008). Available at http://www.lungusa.org/finding-cures/our-research/trendreports/copdtrend-report.pdf.

American Lung Association (ALA). 2010b. Trends in Asthma Morbidity and Mortality. American 

Lung Association Epidemiology and Statistics Unit Research and Program Services 

Division. February. Table 7. Based on NHIS data (CDC, 2008). Available at 

http://www.lungusa.org/finding-cures/our-research/trend-reports/asthma-trendreport.pdf.

Anderson HR, Bremner SA, Atkinson RW, Harrison RM, Walters S. 2001. “Particulate matter and 

daily mortality and hospital admissions in the west midlands conurbation of the UK: 

associations with fine and coarse particles, black smoke and sulphate.” Occup Environ 

Med 58:504–510.

Ayyub, B.M. 2002. Elicitation of Expert Opinions for Uncertainty and Risk. CRC Press, Florida.

Babin, S. M., H. S. Burkom, et al. 2007. “Pediatric patient asthma-related emergency 

department visits and admissions in Washington, DC, from 2001–2004, and associations 

with air quality, socio-economic status and age group.” Environ Health 6: 9.
5-89

Barnett, Adrian G. et al. 2006. “The Effects of Air Pollution on Hospitalizations for 

Cardiovascular Disease in Elderly People in Australian and New Zealand Cities.”

Environmental Health Perspectives 114(7): 1018-1023.

Belanger, K., W. Beckett, E. Triche, M.B. Bracken, T. Holford, P. Ren, J.E. McSharry, D.R. Gold, 

T.A. Platts-Mills, and B.P. Leaderer. 2003. “Symptoms of Wheeze and Persistent Cough 

in the First Year of Life: Associations with Indoor Allergens, Air Contaminants, and 

Maternal History of Asthma.” American Journal of Epidemiology 158:195-202.

Bell, M. L., K. Ebisu, et al. 2008. “Seasonal and Regional Short-term Effects of Fine Particles on 

Hospital Admissions in 202 US Counties, 1999–2005.” American Journal of Epidemiology

168(11): 1301-1310.

Berger, M.C., G.C. Blomquist, D. Kenkel, and G.S. Tolley. 1987. “Valuing Changes in Health Risks: 

A Comparison of Alternative Measures.” The Southern Economic Journal 53:977-984.

Centers for Disease Control and Prevention (CDC). 2003. Health, United States. Table 30. Years 

of Potential Life Lost Before Age 75 for Selected Causes of Death, According to Sex, Race 

and Hispanic Origin: United States, Selected Years 1980– 2000. Available on the Internet 

at <http://www.cdc.gov/nchs/data/hus/hus03.pdf>.

Centers for Disease Control and Prevention (CDC). 2008. National Center for Health Statistics. 

National Health Interview Survey, 1999-2008.

Centers for Disease Control and Prevention (CDC). 2011. United States Life Tables, 2007 

National Vital Statistics Reports. Volume 59, Number 9. September. Available on the 

Internet at <http://www.cdc.gov/nchs/data/nvsr/nvsr59/nvsr59_09.pdf>.

Chay, K.Y., and M. Greenstone. 2003. “The Impact of Air Pollution on Infant Mortality: Evidence 

from Geographic Variation in Pollution Shocks Induced by a Recession.” Quarterly 

Journal of Economics 118(3).

Chen L, Jennison BL, Yang W, Omaye ST. 2000. “Elementary school absenteeism and air 

pollution.” Inhal Toxicol 12(11):997-1016.

Cropper, M. L. and A. J. Krupnick. 1990. The Social Costs of Chronic Heart and Lung Disease.

Resources for the Future. Washington, DC. Discussion Paper QE 89-16-REV.

Crouse DL, Peters PA, van Donkelaar A, Goldberg MS, Villeneuve PJ, Brion O, et al. 2012. “Risk 

of Non-accidental and Cardiovascular Mortality in Relation to Long-term Exposure to 

Low Concentrations of Fine Particulate Matter: A Canadian National-level Cohort Study.”

Environ Health Perspect. In press. http://dx.doi.org/10.1289/ehp.1104049.

Dockery, D.W., C.A. Pope, X.P. Xu, J.D. Spengler, J.H. Ware, M.E. Fay, B.G. Ferris, and F.E. 

Speizer. 1993. “An Association between Air Pollution and Mortality in Six U.S. Cities.”

New England Journal of Medicine 329(24):1753-1759.
5-90

Dockery, D.W., J. Cunningham, A.I. Damokosh, L.M. Neas, J.D. Spengler, P. Koutrakis, J.H. Ware, 

M. Raizenne, and F.E. Speizer. 1996. “Health Effects of Acid Aerosols On North American 

Children-Respiratory Symptoms.” Environmental Health Perspectives 104(5):500-505.

Dominici, F., R.D. Peng, M.L. Bell, L. Pham, A. McDermott, S.L. Zeger, J.M. Samet. 2006. “Fine 

Particulate Air Pollution and Hospital Admission for Cardiovascular and Respiratory 

Diseases.” Journal of the American Medical Association 295: 1127-1134.

Eftim SE, Samet JM, Janes H, McDermott A, Dominici F. 2008. “Fine particulate matter and mortality: a comparison of the Six Cities and American Cancer Society cohorts with a 

Medicare cohort.” Epidemiology 19:209–216.

Eisenstein, E.L., L.K. Shaw, K.J. Anstrom, C.L. Nelson, Z. Hakim, V. Hasselblad and D.B. Mark. 

2001. “Assessing the Clinical and Economic Burden of Coronary Artery Disease: 1986-

1998. “Medical Care 39(8):824-35.

Eisner M, N Anthonisen, D Coultas et al. 2010. “An official American Thoracic Society public 

policy statement: novel risk factors and the global burden of chronic obstructive 

pulmonary disease,” Am J Respir Crit Care Med 182: 693–718.

Fann N, Lamson A, Wesson K, Risley D, Anenberg SC, Hubbell BJ. 2012a. “Estimating the 

National Public Health Burden Associated with Exposure to Ambient PM2.5 and Ozone. 

Risk Analysis,” Risk Analysis. 32(1): 81-95.

Fann N, Roman HR, Fulcher CF, Gentile M, Wesson K, Hubbell BJ, Levy JI. 2012b. “Maximizing 

Health Benefits and Minimizing Inequality: Incorporating Local Scale Data in the Design 

and Evaluation of Air Quality Policies.” Risk Analysis. 32(6): 908—922.

Freeman (III), AM. 1993. The Measurement of Environmental and Resource Values: Theory and 

Methods. Washington, DC: Resources for the Future.

Gan, W. Q., H. W. Davies, et al. 2012. “Association of Long-term Exposure to Community Noise 

and Traffic-related Air Pollution With Coronary Heart Disease Mortality.” American 

Journal of Epidemiology. In press. doi: 10.1093/aje/kwr424.

GeoLytics Inc. 2002. Geolytics CensusCD® 2000 Short Form Blocks. CD-ROM Release 1.0.

GeoLytics, Inc. East Brunswick, NJ. Available: http://www.geolytics.com/ [accessed 29

September 2004].

Gilliland FD, Berhane K, Rappaport EB, Thomas DC, Avol E, Gauderman WJ, et al. 2001. “The 

effects of ambient air pollution on school absenteeism due to respiratory illnesses.”

Epidemiology 12(1):43-54.

Hall JV, Brajer V, Lurmann FW. 2003. Economic Valuation of Ozone-related School Absences in 

the South Coast Air Basin of California. Contemporary Economic Policy 21(4):407-417.
5-91

Harrington, W., and P.R. Portney. 1987. “Valuing the Benefits of Health and Safety Regulation.”

Journal of Urban Economics 22:101-112.

Hollman, F.W., T.J. Mulder, and J.E. Kallan. 2000. Methodology and Assumptions for the 

Population Projections of the United States: 1999 to 2100. Population Division Working 

Paper No. 38, Population Projections Branch, Population Division, U.S. Census Bureau, 

Department of Commerce. January. Available on the Internet at 

<http://www.census.gov/population/www/documentation/twps0038/twps0038.html>.

Hubbell, B., A. Hallberg, D.R. McCubbin, and E. Post. 2005. “Health-Related Benefits of Attaining 

the 8-Hr Ozone Standard.” Environmental Health Perspectives 113:73–82. ICD, 1979

Hubbell BL. 2006. “Implementing QALYs in the analysis of air pollution regulations.”

Environmental and Resource Economics 34:365–384.

Industrial Economics, Incorporated (IEc). 2006. Expanded Expert Judgment Assessment of the 

Concentration-Response Relationship Between PM2.5 Exposure and Mortality. Prepared 

for: Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, 

Research Triangle Park, NC. September. Available on the Internet at 

<http://www.epa.gov/ttn/ecas/regdata/Uncertainty/pm_ee_tsd_expert_interview_sum

maries.pdf>.

Kleckner, N., and J. Neumann. 1999. Recommended Approach to Adjusting WTP Estimates to 

Reflect Changes in Real Income. Memorandum to Jim Democker, U.S. EPA/OPAR. June 3. 

Available on the Internet at 

<http://www.epa.gov/ttn/ecas/regdata/Benefits/background/klecknerandneumann199

9.pdf>.

Kochi, I., B. Hubbell, and R. Kramer. 2006. “An Empirical Bayes Approach to Combining 

Estimates of the Value of Statistical Life for Environmental Policy Analysis.”

Environmental and Resource Economics. 34: 385-406.

Krewski D, Jerrett M, Burnett RT, Ma R, Hughes E, Shi, Y, et al. 2009. “Extended follow-up and 

spatial analysis of the American Cancer Society study linking particulate air pollution and 

mortality.” HEI Research Report, 140, Health Effects Institute, Boston, MA.

Krewski, D., R.T. Burnett, M.S. Goldbert, K. Hoover, J. Siemiatycki, M. Jerrett, M. Abrahamowicz, 

and W.H. White. 2000. “Reanalysis of the Harvard Six Cities Study and the American 

Cancer Society Study of Particulate Air Pollution and Mortality.” Special Report to the 

Health Effects Institute. Cambridge MA. July.

Krupnick, A.J., and M.L. Cropper. 1992. “The Effect of Information on Health Risk Valuations.”

Journal of Risk and Uncertainty 5(2):29-48.
5-92

Kunzli, N., R. Kaiser, S. Medina, M. Studnicka, O. Chanel, P. Filliger, M. Herry, F. Horak Jr., V.

Puybonnieux-Texier, P. Quenel, J. Schneider, R. Seethaler, J-C Vergnaud, and H. Sommer. 

2000. “Public-Health Impact of Outdoor and Traffic-Related Air Pollution: A European 

Assessment.” The Lancet 356:795-801.

Kunzli, N., S. Medina, R. Kaiser, P. Quenel, F. Horak Jr, and M. Studnicka. 2001. “Assessment of 

Deaths Attributable to Air Pollution: Should We Use Risk Estimates Based on Time Series 

or on Cohort Studies?” American Journal of Epidemiology 153(11):1050-55.

Laden, F., J. Schwartz, F.E. Speizer, and D.W. Dockery. 2006. “Reduction in Fine Particulate Air 

Pollution and Mortality.” American Journal of Respiratory and Critical Care Medicine

173:667-672.

Lave, L.B., and E.P. Seskin. 1977. Air Pollution and Human Health. Baltimore: Johns Hopkins 

University Press for Resources for the Future.

Lepeule J, Laden F, Dockery D, Schwartz J 2012. “Chronic Exposure to Fine Particles and 

Mortality: An Extended Follow-Up of the Harvard Six Cities Study from 1974 to 2009.”

Environ Health Perspect. In press. http://dx.doi.org/10.1289/ehp.1104660

Levy JI, Baxter LK, Schwartz J. 2009. “Uncertainty and variability in health-related damages from 

coal-fired power plants in the United States.” Risk Anal. 29(7) 1000-1014.

Lipfert, F.W., H. Mitchell Perry Jr., J. Philip Miller, Jack D. Baty, Ronald E. Wyzg, and Sharon E. 

Carmody. 2000. “The Washington University-EPRI Veterans’ Cohort Mortality Study: 

Preliminary Results.” Inhalation Toxicology 12:41-74.

Lipfert, F.W., S.C. Morris, and R.E. Wyzga. 1989. “Acid Aerosols—the Next Criteria Air 

Pollutant.” Environmental Science & Technology 23(11):1316-1322.

Lipfert, F.W.; Perry, H.M., Jr.; Miller, J.P.; Baty, J.D.; Wyzga, R.E.; Carmody, S.E. 2003. “Air 

Pollution, Blood Pressure, and Their Long-Term Associations with Mortality.” Inhalation 

Toxicology. 15, 493-512.

Lipfert, F.W.; Wyzga, R.E.; Baty, J.D.; Miller, J.P. 2006. “Traffic Density as a Surrogate Measure of

Environmental Exposures in Studies of Air Pollution Health Effects: Long-Term Mortality 

in a Cohort of US Veterans.” Atmospheric Environment 40: 154-169.

Lippmann M, Ito K, Nádas A, Burnett RT. 2000. “Association of particulate matter components

with daily mortality and morbidity in urban populations.” Res Rep Health Eff Inst.

Aug;(95):5-72, discussion 73-82.

Lisabeth, L.D. et al. 2008. “Ambient air pollution and risk for ischemic stroke and transient 

ischemic attack.” Annals of Neurology. July (64): 53—59.
5-93

Mansfield, Carol; Paramita Sinha; Max Henrion. 2009. Influence Analysis in Support of 

Characterizing Uncertainty in Human Health Benefits Analysis: Final Report. Prepared 

for U.S. EPA, Office of Air Quality Planning and Standards. November. Available on the 

internet at 

<http://www.epa.gov/ttn/ecas/regdata/Benefits/influence_analysis_final_report_psg.p

df>.

Mar, T. F., J. Q. Koenig and J. Primomo. 2010. “Associations between asthma emergency visits 

and particulate matter sources, including diesel emissions from stationary generators in 

Tacoma, Washington.” Inhal Toxicol. Vol. 22 (6): 445-8.Mar, T. F., T. V. Larson, et al. 

2004. “An analysis of the association between respiratory symptoms in subjects with 

asthma and daily air pollution in Spokane, Washington.” Inhal Toxicol 16(13): 809-15.

Metzger, K. B., P. E. Tolbert, et al. 2004. “Ambient air pollution and cardiovascular emergency 

department visits.” Epidemiology 15(1): 46-56.

Miller, Kristin A., David S. Siscovick, Lianne Sheppard, Kristen Shepherd, Jeffrey H. Sullivan, 

Garnet L. Anderson, and Joel D. Kaufman. 2007. “Long-Term Exposure to Air Pollution 

and Incidence of Cardiovascular Events in Women.” New England Journal of Medicine. 

356 (5) :447-458.

Moolgavkar, S.H. 2000. “Air Pollution and Hospital Admissions for Diseases of the Circulatory 

System in Three U.S. Metropolitan Areas.” Journal of the Air and Waste Management 

Association 50:1199-1206.

Moolgavkar, S.H. 2003. “Air Pollution and Daily Deaths and Hospital Admissions in Los Angeles 

and Cook Counties.” In Revised Analyses of Time-Series Studies of Air Pollution and 

Health. Special Report. Boston, MA: Health Effects Institute.

Mrozek, J.R., and L.O. Taylor. 2002. “What Determines the Value of Life? A Meta-Analysis.” 

Journal of Policy Analysis and Management 21(2):253-270.

Mustafić H, Jabre P, Caussin C et al. 2012. “Main Air Pollutants and Myocardial Infarction: A 

Systematic Review and Meta-analysis” JAMA. 2012;307(7):713-721.

National Center for Education Statistics (NCHS). 1996. The Condition of Education 1996, 

Indicator 42: Student Absenteeism and Tardiness. U.S. Department of Education. 

Washington, DC.

National Research Council (NRC). 2002. Estimating the Public Health Benefits of Proposed Air 

Pollution Regulations. Washington, DC: The National Academies Press. Washington, DC.

National Research Council (NRC). 2008. Estimating Mortality Risk Reduction and Economic 

Benefits from Controlling Ozone Air Pollution. National Academies Press. Washington, 

DC.
5-94

Neumann, J.E., M.T. Dickie, and R.E. Unsworth. 1994. “Linkage Between Health Effects 

Estimation and Morbidity Valuation in the Section 812 Analysis—Draft Valuation 

Document.” Industrial Economics Incorporated (IEc) Memorandum to Jim DeMocker, 

U.S. Environmental Protection Agency, Office of Air and Radiation, Office of Policy 

Analysis and Review. March 31. Available on the Internet at 

<http://www.epa.gov/ttn/ecas/regdata/Benefits/background/neumannn1994.pdf>.

Office of Management and Budget (OMB). 2003. Circular A-4: Regulatory Analysis. Washington, 

DC. Available on the Internet at <http://www.whitehouse.gov/omb/circulars/a004/a4.html.>

Ostro, B., M. Lipsett, J. Mann, H. Braxton-Owens, and M. White. 2001. “Air Pollution and 

Exacerbation of Asthma in African-American Children in Los Angeles.” Epidemiology

12(2):200–208.

Ostro, B.D. 1987. “Air Pollution and Morbidity Revisited: A Specification Test.” Journal of

Environmental Economics Management 14:87-98.

Ostro, B.D. and S. Rothschild. 1989. “Air Pollution and Acute Respiratory Morbidity: An 

Observational Study of Multiple Pollutants.” Environmental Research 50:238-247.

Ozkaynak, H., and G.D. Thurston. 1987. “Associations between 1980 U.S. Mortality Rates and 

Alternative Measures of Airborne Particle Concentration.” Risk Analysis 7(4):449-461.

Patel, M. M., S. N. Chillrud, J. C. Correa, Y. Hazi, M. Feinberg, D. Kc, S. Prakash, J. M. Ross, D. 

Levy and P. L. Kinney. 2010. “Traffic-Related Particulate Matter and Acute Respiratory 

Symptoms among New York City Area Adolescents.” Environ Health Perspect. 

Sep;118(9):1338-43.

Peel JL; Metzger KB; Klein M; Flanders WD; Mulholland JA; Tolbert PE. 2007. “Ambient air 

pollution and cardiovascular emergency department visits in potentially sensitive 

groups.” Am J Epidemiol 165: 625-633.

Peng, R. D., M. L. Bell, et al. 2009. “Emergency admissions for cardiovascular and respiratory 

diseases and the chemical composition of fine particle air pollution.” Environ Health 

Perspect 117(6): 957-63.

Peng, R. D., H. H. Chang, et al. 2008. “Coarse particulate matter air pollution and hospital 

admissions for cardiovascular and respiratory diseases among Medicare patients.” JAMA

299(18): 2172-9.

Peters A. 2005. “Particulate matter and heart disease: evidence from epidemiological studies.”

Toxicol Appl Pharmacol. Sep 1;207(2 Suppl):477-82.

Peters A. 2006. “When a myocardial infarction comes out of the not-so-blue air.” Circulation. 

Dec 5;114(23):2430-1
5-95

Peters, A., D. W. Dockery, J. E. Muller and M. A. Mittleman. 2001. “Increased particulate air 

pollution and the triggering of myocardial infarction.” Circulation. Vol. 103 (23): 2810-5.

Poloniecki, J.D., R.W. Atkinson., A.P. de Leon., and H.R. Anderson. 1997. “Daily Time Series for 

Cardiovascular Hospital Admissions and Previous Day’s Air Pollution in London, UK.”

Occupational and Environmental Medicine 54(8):535-540

Pope, C.A., III, R.T. Burnett, G.D. Thurston, M.J. Thun, E.E. Calle, D. Krewski, and J.J. Godleski. 

2004. “Cardiovascular Mortality and Long-term Exposure to Particulate Air Pollution.”

Circulation 109: 71-77.

Pope, C.A., III, R.T. Burnett, M.J. Thun, E.E. Calle, D. Krewski, K. Ito, and G.D. Thurston. 2002. 

“Lung Cancer, Cardiopulmonary Mortality, and Long-term Exposure to Fine Particulate 

Air Pollution.” Journal of the American Medical Association 287:1132-1141.

Pope, C.A., III, D.W. Dockery, J.D. Spengler, and M.E. Raizenne. 1991. “Respiratory Health and 

PM10 Pollution: A Daily Time Series Analysis.” American Review of Respiratory Diseases

144:668-674.

Pope, CA III, E Majid, D Dockery. 2009. “Fine Particle Air Pollution and Life Expectancy in the 

United States.” New England Journal of Medicine 360: 376–386.

Pope, C. A., III, J. B. Muhlestein, et al. 2006. “Ischemic heart disease events triggered by shortterm exposure to fine particulate air pollution.” Circulation 114(23): 2443-8.

Pope, C.A., III, M.J. Thun, M.M. Namboodiri, D.W. Dockery, J.S. Evans, F.E. Speizer, and C.W. 

Heath, Jr. 1995. “Particulate Air Pollution as a Predictor of Mortality in a Prospective 

Study of U.S. Adults.” American Journal of Respiratory Critical Care Medicine 151:669-

674.

Puett RC, Hart JE, Suh H, Mittleman M, Laden F. 2011. “Particulate Matter Exposures, Mortality 

and Cardiovascular Disease in the Health Professionals Follow-up Study.” Environ Health 

Perspect. August; 119(8): 1130–1135.

Puett RC, Hart JE, Yanosky JD, Paciorek C, Schwartz J, Suh H, et al. 2009. “Chronic fine and 

coarse particulate exposure, mortality and coronary heart disease in the Nurses’ Health 

Study.” Environ Health Perspect 117:1697–1701.

Roman, Henry A., Katherine D. Walker, Tyra L. Walsh, Lisa Conner, Harvey M. Richmond, Bryan 

J. Hubbell, and Patrick L. Kinney. 2008. “Expert Judgment Assessment of the Mortality 

Impact of Changes in Ambient Fine Particulate Matter in the U.S.” Environ. Sci. Technol., 

42(7):2268-2274.

Rosamond, W., G. Broda, E. Kawalec, S. Rywik, A. Pajak, L. Cooper, and L. Chambless. 1999. 

“Comparison of Medical Care and Survival of Hospitalized Patients with Acute 

Myocardial Infarction in Poland and the United States.” American Journal of Cardiology

83:1180-1185
5-96

Rowe, R.D., and L.G. Chestnut. 1986. “Oxidants and Asthmatics in Los Angeles: A Benefits

Analysis—Executive Summary.” Prepared by Energy and Resource Consultants, Inc.

Report to the U.S. Environmental Protection Agency, Office of Policy Analysis. EPA- 230-

09-86-018. Washington, DC.

Rowlatt, P., Spackman, M., Jones, S., Jones-Lee, M., Loomes, G. 1998. Valuation of deaths from 

air pollution. A Report for the Department of Environment, Transport and the Regions 

and the Department of Trade and Industry. National Economic Research Associates 

(NERA), London.

Russell, M.W., D.M. Huse, S. Drowns, E.C. Hamel, and S.C. Hartz. 1998. “Direct Medical Costs of 

Coronary Artery Disease in the United States.” American Journal of Cardiology

81(9):1110-1115.

Schwartz, J. 1993. “Particulate Air Pollution and Chronic Respiratory Disease.” Environment 

Research 62:7-13.

Schwartz, J., and L.M. Neas. 2000. “Fine Particles are More Strongly Associated than Coarse 

Particles with Acute Respiratory Health Effects in Schoolchildren.” Epidemiology 11:6-

10.

Schwartz J, Dockery DW, Neas LM, Wypij D, Ware JH, Spengler JD, Koutrakis P, Speizer FE, Ferris 

BG Jr. 1994. “Acute effects of summer air pollution on respiratory symptom reporting in 

children.” American Journal of Respiratory and Critical Care Medicine 150(5 Pt 1):1234-

42.

Schwartz J, Coull B, Laden F. 2008. “The Effect of Dose and Timing of Dose on the Association 

between Airborne Particles and Survival.” Environmental Health Perspectives 116: 64-

69.

Sheppard, L. 2003. “Ambient Air Pollution and Nonelderly Asthma Hospital Admissions in

Seattle, Washington, 1987-1994.” In Revised Analyses of Time-Series Studies of Air

Pollution and Health. Special Report. Boston, MA: Health Effects Institute.

Shogren, J., and T. Stamland. 2002. “Skill and the Value of Life.” Journal of Political Economy

110:1168-1197.

Slaughter, James C et al. 2005. “Association between particulate matter and emergency room 

visits, hospital admissions and mortality in Spokane, Washington.” Journal of Exposure 

Analysis and Environmental Epidemiology (2005) 15, 153–159. 

doi:10.1038/sj.jea.7500382

Smith, D.H., D.C. Malone, K.A. Lawson, L.J. Okamoto, C. Battista, and W.B. Saunders. 1997. “A 

National Estimate of the Economic Costs of Asthma.” American Journal of Respiratory 

and Critical Care Medicine 156(3 Pt 1):787-793.
5-97

Smith, K., Pattanayak SK, Van Houtven G. 2006. “Structural benefit transfer: An example using 

VSL estimates.” Ecological Economics 60: 361-371.

Standard and Poor’s. 2000. “The U.S. Economy: The 25 Year Focus.” Winter. Available on the 

Internet at http://:www.standardandpoors.com

Stanford, R., T. McLaughlin and L. J. Okamoto. 1999. “The cost of asthma in the emergency 

department and hospital.” Am J Respir Crit Care Med.160 (1): 211-5.

Sullivan, J., L. Sheppard, et al. 2005. “Relation between short-term fine-particulate matter 

exposure and onset of myocardial infarction.” Epidemiology 16(1): 41-8.

Tagaris E, Liao KJ, Delucia AJ, et al. 2009. “Potential impact of climate change on air-pollution 

related human health effects.” Environ. Sci. Technol. 43: 4979–4988.

Tolbert, P. E., M. Klein, et al. 2007. “Multipollutant modeling issues in a study of ambient air 

quality and emergency department visits in Atlanta.” J Expo Sci Environ Epidemiol 17 

Suppl 2: S29-35.

Tolley, G.S. et al. 1986. Valuation of Reductions in Human Health Symptoms and Risks.

University of Chicago. Final Report for the U.S. Environmental Protection Agency, Office 

of Policy Analysis. January. Available at 

<http://yosemite.epa.gov/ee/epa/eerm.nsf/a7a2ee5c6158cedd852563970080ee30/eaa

2842b3d2bc2798525644d0053bf48!OpenDocument#_Section6>.

U.S. Bureau of Economic Analysis (U.S. BEA). 2004. BEA Economic Areas (EAs). U.S. Department 

of Commerce. Available on the Internet at 

<http://www.bea.gov/regional/docs/econlist.cfm>.

U.S. Bureau of Economic Analysis (U.S. BEA). 1997. Real Gross Domestic Product—Table 2A. U.S. 

Department of Commerce.

U.S. Bureau of Economic Analysis (U.S. BEA). 1997. The Economic and Budget Outlook: An 

Update, Table 4—Economic Projections for Calendar Years 1997 Through 2007. 

September. U.S. Department of Commerce.

U.S. Bureau of the Census. 2001. Statistical Abstract of the United States, 2001, Section 12: 

Labor Force, Employment, and Earnings, Table No. 521. Washington, DC.

U.S. Environmental Protection Agency (U.S. EPA). 1999a. The Benefits and Costs of the Clean Air 

Act, 1990–2010. Prepared for U.S. Congress by U.S. EPA, Office of Air and 

Radiation/Office of Policy Analysis and Review, Washington, DC, November; EPA report 

no. EPA-410-R-99-001. Available on the Internet at 

<http://www.epa.gov/air/sect812/1990-2010/fullrept.pdf>.
5-98

U.S. Environmental Protection Agency (U.S. EPA). 2000. Guidelines for Preparing Economic 

Analyses. EPA 240-R-00-003. National Center for Environmental Economics, Office of 

Policy Economics and Innovation. Washington, DC. September. Available on the Internet 

at 

<http://yosemite.epa.gov/ee/epa/eed.nsf/webpages/Guidelines.html/$file/cover.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2004. Air Quality Criteria for Particulate 

Matter. National Center for Environmental Assessment, Office of Research and 

Development, U.S. Environmental Protection Agency, Research Triangle Park, NC 

EPA/600/P-99/002bF. Available on the Internet at 

<http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=87903>.

U.S. Environmental Protection Agency (U.S. EPA). 2006a. Regulatory Impact Analysis, 2006 

National Ambient Air Quality Standards for Particulate Matter, Chapter 5. Office of Air 

Quality Planning and Standards, Research Triangle Park, NC. October. Available on the 

Internet at <http://www.epa.gov/ttn/ecas/regdata/RIAs/Chapter%205—Benefits.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2006b. Air Quality Criteria for Ozone and 

Related Photochemical Oxidants (Final). EPA/600/R-05/004aF-cF. Washington, DC: U.S. 

EPA. February. Available on the Internet at 

http://cfpub.epa.gov/ncea/CFM/recordisplay.cfm?deid=149923.U.S. Environmental 

Protection Agency (U.S. EPA). 2008. Regulatory Impact Analysis, 2008 National Ambient 

Air Quality Standards for Ground-level Ozone, Chapter 6. Office of Air Quality Planning 

and Standards, Research Triangle Park, NC. March. Available at 

<http://www.epa.gov/ttn/ecas/regdata/RIAs/6-ozoneriachapter6.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2008a. Regulatory Impact Analysis, 2008

National Ambient Air Quality Standards for Ground-level Ozone, Chapter 6. Office of Air

Quality Planning and Standards, Research Triangle Park, NC. March. Available at

<http://www.epa.gov/ttn/ecas/regdata/RIAs/6-ozoneriachapter6.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2008b. Integrated Science Assessment for 

Oxides of Nitrogen—Health Criteria (Final Report). National Center for Environmental 

Assessment, Research Triangle Park, NC. July. Available on the Internet at 

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=194645

U.S. Environmental Protection Agency (U.S. EPA). 2008c. Integrated Science Assessment for 

Sulfur Oxides—Health Criteria (Final Report). National Center for Environmental 

Assessment, Research Triangle Park, NC. September. Available on the Internet at 

<http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=198843>.
5-99

U.S. Environmental Protection Agency (U.S. EPA). 2009a. Regulatory Impact Analysis: National 

Emission Standards for Hazardous Air Pollutants from the Portland Cement 

Manufacturing Industry. Office of Air Quality Planning and Standards, Research Triangle 

Park, NC. April. Available on the Internet at 

<http://www.epa.gov/ttn/ecas/regdata/RIAs/portlandcementria_4-20-09.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2009b. Integrated Science Assessment for 

Particulate Matter (Final Report). EPA-600-R-08-139F. National Center for 

Environmental Assessment—RTP Division. December. Available on the Internet at 

<http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=216546>.

U.S. Environmental Protection Agency (U.S. EPA). 2010a. Final Regulatory Impact Analysis (RIA) 

for the NO2 National Ambient Air Quality Standards (NAAQS). Office of Air Quality 

Planning and Standards, Research Triangle Park, NC. January. Available on the Internet 

at <http://www.epa.gov/ttn/ecas/regdata/RIAs/FinalNO2RIAfulldocument.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2010b. Quantitative Health Risk Assessment 

for Particulate Matter—Final Report. EPA-452/R-10-005. Office of Air Quality Planning 

and Standards, Research Triangle Park, NC. September. Available on the Internet at 

<http://www.epa.gov/ttnnaaqs/standards/pm/data/PM_RA_FINAL_June_2010.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2010c. Final Regulatory Impact Analysis (RIA) 

for the SO2 National Ambient Air Quality Standards (NAAQS). Office of Air Quality 

Planning and Standards, Research Triangle Park, NC. June. Available on the Internet at 

<http://www.epa.gov/ttn/ecas/regdata/RIAs/fso2ria100602full.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2010d. Regulatory Impact Analysis (RIA) for 

the Proposed Reconsideration of the Ozone National Ambient Air Quality Standards 

(NAAQS). Office of Air Quality Planning and Standards, Research Triangle Park, NC.

January. Available on the Internet at <http://www.epa.gov/ttn/ecas/regdata/RIAs/s1-

supplemental_analysis_full.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2010e. Guidelines for Preparing Economic 

Analyses. EPA 240-R-10-001. National Center for Environmental Economics, Office of

Policy Economics and Innovation. Washington, DC. December. Available on the Internet 

at <http://yosemite.epa.gov/ee/epa/eerm.nsf/vwAN/EE-0568-50.pdf/$file/EE-0568-

50.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2010f. Technical Support Document: Summary 

of Expert Opinions on the Existence of a Threshold in the Concentration-Response 

Function for PM2.5-related Mortality. Research Triangle Park, NC. June. Available on the 

Internet at <www.epa.gov/ttn/ecas/regdata/Benefits/thresholdstsd.pdf>.
5-100

U.S. Environmental Protection Agency (U.S. EPA). 2010g. Proposed Regulatory Impact Analysis 

(RIA) for the Transport Rule. Office of Air Quality Planning and Standards, Research 

Triangle Park, NC. January. Available on the Internet at 

<http://www.epa.gov/ttn/ecas/regdata/RIAs/proposaltrria_final.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2011a. The Benefits and Costs of the Clean Air 

Act 1990 to 2020: EPA Report to Congress. Office of Air and Radiation, Office of Policy, 

Washington, DC. March. Available on the Internet at 

<http://www.epa.gov/oar/sect812/feb11/fullreport.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2011b. Policy Assessment for the Review of 

the Particulate Matter National Ambient Air Quality Standards. EPA-452/D-11-003. April. 

Available on the Internet at 

<http://www.epa.gov/ttnnaaqs/standards/pm/s_pm_2007_pa.html>.

U.S. Environmental Protection Agency (U.S. EPA). 2011c. Regulatory Impact Analysis for the 

Federal Implementation Plans to Reduce Interstate Transport of Fine Particulate Matter 

and Ozone in 27 States; Correction of SIP Approvals for 22 States. June. Available on the 

Internet at <http://www.epa.gov/airtransport/pdfs/FinalRIA.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2011d. Regulatory Impact Analysis for the 

Final Mercury and Air Toxics Standards. EPA-452/R-11-011. December. Available on the 

Internet at <http://www.epa.gov/ttn/ecas/regdata/RIAs/matsriafinal.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2011e. Integrated Science Assessment for 

Ozone and Related Photochemical Oxidants (Second External Review Draft). EPA/600/R10/076B. U.S. Environmental Protection Agency, National Center for Environmental 

Assessment—RTP Division. September. Available at 

<http://oaspub.epa.gov/eims/eimscomm.getfile?p_download_id=503567>.

U.S. Environmental Protection Agency—Science Advisory Board (U.S. EPA-SAB). 1999. An SAB 

Advisory on the Clean Air Act Section 812 Prospective Study Health and Ecological Initial 

Studies. Prepared by the Health and Ecological Effects Subcommittee (HEES) of the 

Advisory Council on the Clean Air Compliance Analysis, Science Advisory Board, U.S. 

Environmental Protection Agency. Washington DC. EPA-SAB-COUNCIL-ADV-99-005.

Available on the Internet at 

<http://yosemite.epa.gov/sab%5CSABPRODUCT.NSF/1AFDEBB45C57F6E585257193005

8C1A5/$File/coua9905.pdf>.

U.S. Environmental Protection Agency—Science Advisory Board (U.S. EPA-SAB). 2000. An SAB 

Report on EPA’s White Paper Valuing the Benefits of Fatal Cancer Risk Reduction. EPASAB-EEAC-00-013. July. Available on the Internet at 

<http://yosemite.epa.gov/sab%5CSABPRODUCT.NSF/41334524148BCCD6852571A7005

16498/$File/eeacf013.pdf>.
5-101

U.S. Environmental Protection Agency—Science Advisory Board (U.S. EPA-SAB). 2004a. Advisory 

on Plans for Health Effects Analysis in the Analytical Plan for EPA’s Second Prospective 

Analysis—Benefits and Costs of the Clean Air Act, 1990–2020. EPA-SAB-COUNCIL-ADV04-002. March. Available on the Internet at 

<http://yosemite.epa.gov/sab%5CSABPRODUCT.NSF/08E1155AD24F871C85256E54004

33D5D/$File/council_adv_04002.pdf>.

U.S. Environmental Protection Agency—Science Advisory Board (U.S. EPA-SAB). 2004b. Review 

of the Draft Analytical Plan for EPA’s Second Prospective Analysis—Benefits and Costs of 

the Clean Air Act, 1990-2020: An Advisory by the Advisory Council for Clean Air 

Compliance Analysis. EPA-SAB-COUNCIL-ADV-04-004. May. Available on the Internet at 

<http://yosemite.epa.gov/sab/sabproduct.nsf/7CCBBFE15CD4C8B185256F17005E3079/

$File/council_adv_04004.pdf>.

U.S. Environmental Protection Agency—Science Advisory Board (U.S. EPA-SAB). 2004c. Advisory 

Council on Clean Air Compliance Analysis Response to Agency Request on Cessation Lag.

EPA-COUNCIL-LTR-05-001. December. Available on the Internet at 

<http://yosemite.epa.gov/sab/sabproduct.nsf/0/39F44B098DB49F3C85257170005293E

0/$File/council_ltr_05_001.pdf>.

U.S. Environmental Protection Agency—Science Advisory Board (U.S. EPA-SAB). 2007. SAB 

Advisory on EPA’s Issues in Valuing Mortality Risk Reduction. EPA-SAB-08-001. October. 

Available on the Internet at 

<http://yosemite.epa.gov/sab/sabproduct.nsf/4128007E7876B8F0852573760058A978/

$File/sab-08-001.pdf>.

U.S. Environmental Protection Agency Science Advisory Board (U.S. EPA-SAB). 2008.

Characterizing Uncertainty in Particulate Matter Benefits Using Expert Elicitation. EPACOUNCIL-08-002. July. Available on the Internet at

<http://yosemite.epa.gov/sab/sabproduct.nsf/0/43B91173651AED9E85257487004EA6C

B/$File/EPA-COUNCIL-08-002-unsigned.pdf>.

U.S. Environmental Protection Agency Science Advisory Board (U.S. EPA-SAB). 2009a.

Consultation on EPA’s Particulate Matter National Ambient Air Quality Standards: Scope 

and Methods Plan for Health Risk and Exposure Assessment. EPA-COUNCIL-09-009. May. 

Available on the Internet at

<http://yosemite.epa.gov/sab/SABPRODUCT.NSF/81e39f4c09954fcb85256ead006be86

e/723FE644C5D758DF852575BD00763A32/$File/EPA-CASAC-09-009-unsigned.pdf>.

U.S. Environmental Protection Agency—Science Advisory Board (U.S. EPA-SAB). 2009b. Review 

of EPA’s Integrated Science Assessment for Particulate Matter (First External Review 

Draft, December 2008). EPA-COUNCIL-09-008. May. Available on the Internet at

<http://yosemite.epa.gov/sab/SABPRODUCT.NSF/81e39f4c09954fcb85256ead006be86

e/73ACCA834AB44A10852575BD0064346B/$File/EPA-CASAC-09-008-unsigned.pdf>.
5-102

U.S. Environmental Protection Agency—Science Advisory Board (U.S. EPA-SAB). 2009c. Review 

of Integrated Science Assessment for Particulate Matter (Second External Review Draft, 

July 2009). EPA-CASAC-10-001. November. Available on the Internet at 

<http://yosemite.epa.gov/sab/SABPRODUCT.NSF/81e39f4c09954fcb85256ead006be86

e/151B1F83B023145585257678006836B9/$File/EPA-CASAC-10-001-unsigned.pdf>.

U.S. Environmental Protection Agency Science Advisory Board (U.S. EPA-SAB). 2010a. Review of 

EPA’s DRAFT Health Benefits of the Second Section 812 Prospective Study of the Clean Air

Act. EPA-COUNCIL-10-001. June. Available on the Internet at 

<http://yosemite.epa.gov/sab/sabproduct.nsf/9288428b8eeea4c885257242006935a3/

59e06b6c5ca66597852575e7006c5d09!OpenDocument&TableRow=2.3#2.>.

U.S. Environmental Protection Agency Science Advisory Board (U.S. EPA-SAB). 2010b. Review of 

Risk Assessment to Support the Review of the Particulate Matter (PM) Primary National 

Ambient Air Quality Standards—External Review Draft (September 2009). EPA-CASAC10-003. Available on the Internet at 

<http://yosemite.epa.gov/sab/sabproduct.nsf/264cb1227d55e02c85257402007446a4/

BC1ECC5D539EF72385257678006D5754/$File/EPA-CASAC-10-003-unsigned.pdf>.

U.S. Environmental Protection Agency Science Advisory Board (U.S. EPA-SAB). 2010c. CASAC 

Review of Quantitative Health Risk Assessment for Particulate Matter—Second External 

Review Draft (February 2010). EPA-CASAC-10-008. Available on the Internet at 

<http://yosemite.epa.gov/sab/sabproduct.nsf/264cb1227d55e02c85257402007446a4/

BC4F6E77B6385155852577070002F09F/$File/EPA-CASAC-10-008-unsigned.pdf>.

U.S. Environmental Protection Agency Science Advisory Board (U.S. EPA-SAB). 2010d. CASAC 

Review of Policy Assessment for the Review of the PM NAAQS—Second External Review 

Draft (June 2010). EPA-CASAC-10-015. Available on the Internet at 

<http://yosemite.epa.gov/sab/sabproduct.nsf/264cb1227d55e02c85257402007446a4/

CCF9F4C0500C500F8525779D0073C593/$File/EPA-CASAC-10-015-unsigned.pdf>.

U.S. Environmental Protection Agency—Science Advisory Board (U.S. EPA-SAB). 2011. Review of 

Valuing Mortality Risk Reductions for Environmental Policy: A White Paper (December 

10, 2010). EPA-SAB-11-011 July. Available on the Internet at 

<http://yosemite.epa.gov/sab/sabproduct.nsf/298E1F50F844BC23852578DC0059A616/

$File/EPA-SAB-11-011-unsigned.pdf>.

Viscusi, V.K., and J.E. Aldy. 2003. “The Value of a Statistical Life: A Critical Review of Market 

Estimates throughout the World.” Journal of Risk and Uncertainty 27(1):5-76.

Viscusi, W.K., W.A. Magat, and J. Huber. 1991. “Pricing Environmental Health Risks: Survey 

Assessments of Risk-Risk and Risk-Dollar Trade-Offs for Chronic Bronchitis.” Journal of 

Environmental Economics and Management 21:32-51.
5-103

Wittels, E.H., J.W. Hay, and A.M. Gotto, Jr. 1990. “Medical Costs of Coronary Artery Disease in 

the United States.” American Journal of Cardiology 65(7):432-440.

Woodruff, T.J., J. Grillo, and K.C. Schoendorf. 1997. “The Relationship Between Selected of 

postneonatal infant mortality and particulate air pollution in the United States.”

Environmental Health Perspectives. Vol. 105 (6): 608-612.

Woodruff TJ, Parker JD, Schoendorf KC. 2006. “Fine particulate matter (PM2.5) air pollution and 

selected causes of postneonatal infant mortality in California.” Environmental Health

Perspectives 114(5):786-90.

Woods & Poole Economics Inc. 2007. Population by Single Year of Age. CD-ROM. Woods & 

Poole Economics, Inc. Washington, D.C.

World Health Organization (WHO). 1977. International Classification of Diseases, 9th Revision 

(ICD-9). Geneva: WHO.

World Health Organization (WHO). 2008. Part 1: Guidance Document on Characterizing and 

Communicating Uncertainty in Exposure Assessment, Harmonization Project Document 

No. 6. Published under joint sponsorship of the World Health Organization, the 

International Labour Organization and the United Nations Environment Programme. 

WHO Press: Geneva, Switzerland. Available on the Internet at 

<www.who.int/ipcs/methods/harmonization/areas/uncertainty%20.pdf>.

Zanobetti, A., M. Franklin, et al. 2009. “Fine particulate air pollution and its components in 

association with cause-specific emergency admissions.” Environmental Health 8: 58-

60.Zeger S; Dominici F; McDermott A; Samet J. 2008. “Mortality in the Medicare 

population and chronic exposure to fine particulate air pollution in urban centers (2000-

2005).” Environ Health Perspect 116: 1614-1619.

Zanobetti A. and Schwartz, J. 2006. “Air pollution and emergency admissions in Boston, MA.” J 

Epidemiol Community Health 60(10): 890-5.
5.A-1

APPENDIX 5.A

DISTRIBUTION OF THE PM2.5-RELATED BENEFITS

5.A.1 Overview

EPA is developing new approaches and metrics to improve its characterization of the

impacts of EPA rules on different populations. This analysis reflects one such approach, which 

attempts to answer two questions regarding the distribution of PM2.5-related benefits resulting 

from the illustrative attainment of a more stringent National Ambient Air Quality Standards 

(NAAQS) for particulate matter (PM):

1. What is the baseline distribution of PM2.5-related mortality risk according to the 

race, income and education of the population living within areas projected to exceed

alternative combinations of primary PM2.5 standards?

2. How would air quality improvements within these counties change the distribution 

of risk among populations of different races—particularly those populations at 

greatest risk in the baseline?1

There are important methodological differences between this distributional analysis and 

the Environmental Justice analyses accompanying the Regulatory Impact Analyses (RIAs) for the 

Cross-State Air Pollution Rule and the Mercury and Air Toxics Standard that are worth noting 

here. These latter two RIAs applied photochemical modeling to characterize the change in 

population exposure to PM2.5 after the implementation of well-characterized emission controls 

on Electricity Generating Units. By contrast, this RIA aims to illustrate the potential benefits and 

costs of attaining alternative primary PM2.5 standards. For this reason, similar to the main 

benefits analysis in this RIA, we performed monitor rollbacks to just attain the alternative 

combinations of primary standards following the approach described in Chapter 2 of this RIA.

A limitation of this approach to characterizing improvements in PM2.5 air quality is that 

populations in each projected nonattainment area share the exposure reductions equally; this 

is because simple rollbacks do not reflect the spatial heterogeneity in PM2.5 changes one would 

expect from a modeled attainment strategy. However, as EPA demonstrated in the Detroit 

multi-pollutant pilot project, states can design attainment strategies to maximize air quality 

improvements among those populations at greatest risk of air pollution health impacts—which 

both maximizes overall benefits while lowering the level of risk inequality (Fann et al., 2012a).

 1 In this analysis we assess the change in risk among populations of different race and educational attainment. As 

we discuss further in the methodology, we consider this last variable because of the availability of educationmodified PM2.5 mortality risk estimates.
5.A-2

In this analysis we estimated that in 2020, prior to the attainment of a more stringent 

PM standard, the level of PM2.5 mortality risk is not distributed equally among populations of 

different levels of educational attainment—though the level of mortality risk appears to be 

shared fairly equally among populations of different races. We find that attaining a more 

stringent alternative annual PM NAAQS level of 12 μg/m3 in conjunction with a 24-hour 

standard of 35 μg/m3 (as an illustrative example) would provide air quality improvements, and 

lower PM2.5-related mortality risk, by a fairly consistent margin among minority populations. 

We note that while the methods used for this analysis have been employed in recent EPA 

Regulatory Impact Assessments (U.S. EPA, 2011) and are drawn from techniques described in 

the peer reviewed literature (Fann et al., 2012b) EPA will continue to modify these approaches 

based on evaluation of the methods.

5.A.2 Methodology

As a first step, we identify the counties exceeding an annual standard of 12 μg/m3 in 

conjunction with a 24-hour standard of 35 μg/m3 in 2020, using the results of the baseline 

CMAQ air quality modeling. This air quality modeling simulation projects PM2.5 levels after the 

incorporation of all “on the books” rules (i.e., those promulgated at the time the air quality 

modeling was performed), but does not reflect the illustrative attainment strategies. We next 

identified the counties whose PM2.5 levels exceed the alternative combinations of PM2.5 

standards. We then performed a monitor rollback to adjust the annual PM2.5 levels in each 

county such that they attain the alternative combinations of PM2.5 standards. This approach 

provides us with baseline and rolled-back PM2.5 levels that attain this combination of annual 

and daily PM2.5 standards. Within each county exceeding the this combination of PM2.5 

standards, we estimate the level of all-cause PM2.5 mortality risks for adult populations as well 

as the level of PM2.5 mortality risk according to the race and educational attainment of the 

population.

Our approach to calculating PM2.5 mortality risk is generally consistent with the primary 

analysis with two exceptions: the PM mortality risk coefficients used to quantify impacts and 

the baseline mortality rates used to calculate education-modified mortality impacts (a detailed 

discussion of how both the mortality risk coefficients and baseline incidence rates are used to 

estimate the incidence of PM2.5-related deaths may be found in the benefits chapter). Within 

both this and other analyses of the ACS cohort (see: Krewski et al., 2000), educational 

attainment has been found to be inversely related to the risk of all-cause mortality. That is, 

populations with lower levels of education (in particular, < grade 12) are more vulnerable to 

PM2.5-related mortality. Krewski and colleagues note that “...the level of education attainment 
5.A-3

may likely indicate the effects of complex and multi-factorial socioeconomic processes on 

mortality...,” factors that we would like to account for in this distributional assessment. When 

estimating PM mortality impacts among populations according to level of education, we 

applied PM2.5 mortality risk coefficients modified by educational attainment: less than grade 12 

(Relative Risk (RR) = 1.082, 95% confidence intervals 1.024—1.144 per 10 μg/m3 change), grade 

12 (RR = 1.072, 95% confidence intervals 1.020—1.127 per 10 μg/m3 change), and greater than 

grade 12 (RR = 1.055, 95% confidence intervals 1.018—1.094 per 10 μg/m3 change). The Pope 

et al. (2002) study, which EPA has frequently relied upon to quantify PM-related mortality, does 

not provide education-stratified RR estimates. The principal reason we applied risk estimates 

from the Krewski study was to ensure that the risk coefficients used to estimate all-cause 

mortality risk and education-modified mortality risk were drawn from a consistent modeling 

framework and because the use of the Krewski study is consistent with the primary benefits 

analysis.

The other key difference between this distributional analysis and the main benefits

analysis for this rule relates to the baseline mortality rates. As described in Chapter 5 of this 

RIA, we calculate PM2.5-related mortality risk relative to baseline mortality rates in each county. 

Traditionally, for benefits analysis, we have applied county-level age- and sex-stratified baseline 

mortality rates when calculating mortality impacts (Abt Associates, 2010). To calculate PM2.5 

impacts by race, we incorporated race-specific (stratified by White/Black/Asian/Native 

American) baseline mortality rates. This approach improves our ability to characterize the 

relationship between race and PM2.5-related mortality however, we do not have a differential 

concentration-response function as we do for education, and as a result, we are not able to 

capture the full impacts of race in modifying the benefits associated with reductions in PM2.5. 

Table 5.A-1 summarizes the key attributes of the two distributional assessments.

Table 5.A-1. Key Attributes of the Distributional Analyses in this Appendix 

Input parameter

Distributional Analysis

Education-modified PM Mortality Risk Race-stratified PM mortality risk

Effect coefficient Stratified by education attainment (<12, 

=12, >12)

All-cause, applied to each 

population subgroup 

Baseline mortality rates Cause, age and sex stratified Cause, age, sex race and ethnicity

stratified
5.A-4

The result of this analysis is a distribution of PM2.5 mortality risk estimates by county, 

stratified by each of the two population variables (race and educational attainment). We have 

less confidence in county-level estimates of mortality than the national or even state estimates. 

However, the modeling down to the county level can be considered reasonable because the 

estimates are based on monitored air quality modeling estimates of PM2.5, county level baseline 

mortality rates, and a concentration-response function that is derived from county level data. 

We next identified the counties projected to exceed the current combination of annual and 

daily PM2.5 standards (15/35) (“baseline”) in 2020. The second step of the analysis was to repeat 

the sequence above by estimating PM2.5 mortality risk in counties projected to exceed an 

illustrative combination of PM2.5 standards (12/35) after rolling back monitor values to reach 

attainment in 2020.

5.A.3 Results

Figures 5.A-1 and 5.A-2 summarize the change in the median level of PM2.5 mortality risk 

among populations stratified by educational attainment and race in non-attaining counties. The 

percentage of deaths due to PM2.5 among populations with less than a grade 12 education is 

significantly higher than those who have either completed high school or who have attained an 

education level greater than high school. This finding is consistent with the relative levels of risk 

coefficients for each population, where we apply a much larger risk coefficient for populations 

with less than a grade 12 education. The level of risk reduction between the baseline and 12/35 

is roughly equal between the three groups.

In Figure 5.A-2, Black and Native American populations are at significantly greater PM2.5

mortality risk in the baseline, as compared to other races. White and Asian populations are at 

lower levels of PM2.5 mortality risk. The finding that black populations are at greater PM2.5

mortality risk in the baseline may be due both to the elevated baseline mortality risks or greater 

exposure to PM2.5 among this population. After attaining 12/35, populations of all races benefit, 

though the reduction in PM mortality risk among whites is within rounding error.
 

5.A-5 

Figure 5.A-1. PM2.5 Mortality Risk Modified by Educational Attainment in Counties Projected 

to Exceed 12/35
 

5.A-6 

Figure 5.A-2. PM2.5 Mortality Risk by Race in Counties Projected to Exceed 12/35

Table 5.A-2. Numerical Values Used for Figures 5.A-1 and 5.A-2 Abovea

Year

Scenario, Percent

Baseline 12/35 

Impacts by education

< Grade 12 8% 6.5%

= Grade 12 7.1% 5.7%

> Grade 12 5.5% 4.4%

Impacts by race

Asian 4.9% 4.5%

Black 5.2% 5%

Native American 5% 4.8%

White 4.9% 4.9%

a Estimates expressed with a greater number of significant digits to facilitate comparisons among values.
5.A-7

5.A.4 Discussion

This analysis is subject to certain limitations, some of which we note above but are 

worth repeating here. First, the change in the distribution of PM2.5-related mortality risk we 

estimate here depends is influenced strongly by the simulated attainment strategy. While we 

performed simple monitor rollbacks to attain a more stringent standard, we describe other 

approaches above that may maximize human health benefits while also reducing the level of 

risk inequality. The monitor rollback approach employed here simulates improvements in PM2.5

levels in proximity to monitors projected to exceed a tighter PM NAAQS; we would expect an 

attainment strategy to achieve air quality improvements over a broader geographic area, 

affecting a greater portion the population than we have reflected here.

Notwithstanding these uncertainties, these results suggest that all populations, 

irrespective of education attainment or race, living in locations projected to exceed an 

illustrative annual standard of 12 μg/m3 in conjunction with a 24-hour standard of 35 μg/m3 in 

2020 would experience a reduction in PM-related mortality risk. Certain sub-populations, 

including those with less than a grade 12 education and Native Americans, area at an elevated 

risk in the baseline. Attainment of this illustrative standard in 2020 would reduce the level of 

mortality risk among these sub-populations.

5.A.5 References

Abt Associates, Inc. 2010. Environmental Benefits and Mapping Program (Version 4.0). 

Bethesda, MD. Prepared for U.S. Environmental Protection Agency Office of Air Quality 

Planning and Standards. Research Triangle Park, NC. Available on the Internet at 

<http://www.epa.gov/air/benmap>.

Fann N, Roman HR, Fulcher CF, Gentile M, Wesson K, Hubbell BJ, Levy JI. 2012a. “Maximizing 

Health Benefits and Minimizing Inequality: Incorporating Local Scale Data in the Design 

and Evaluation of Air Quality Policies.” Risk Analysis 31(6): 908-222.

Fann N, Lamson A, Wesson K, Risley D, Anenberg SC, Hubbell BJ. 2012b. “Estimating the 

National Public Health Burden Associated with Exposure to Ambient PM2.5 and Ozone.” 

Risk Analysis 32(1): 81-95.

Krewski D, Jerrett M, Burnett RT, Ma R, Hughes E, Shi Y, Turner C, Pope CA, Thurston G, Calle 

EE, Thunt MJ. 2009. Extended follow-up and spatial analysis of the American Cancer 

Society study linking particulate air pollution and mortality. HEI Research Report, 140, 

Health Effects Institute, Boston, MA.
5.A-8

Krewski D, Burnett RT, Goldberg MS, et al. 2000. Reanalysis of the Harvard Six Cities Study and 

the American Cancer Society Study of Particulate Air Pollution and Mortality: Special 

Report. Cambridge, Mass: Health Effects Institute.

Pope CA, Burnett RT, Thun MJ, Calle EE, Krewski D, Ito K, Thurston GD. 2002. “Lung Cancer, 

Cardiopulmonary Mortality, and Long-term Exposure to Fine Particulate Air Pollution.” 

Journal of the American Medical Association, 287: 1132—1141.
5.B-1

APPENDIX 5.B

ADDITIONAL SENSITIVITY ANALYSES RELATED TO THE HEALTH BENEFITS ANALYSIS

The analysis presented in Chapter 5 of this RIA is based on our current interpretation of 

the scientific and economic literature. That interpretation requires judgments regarding the 

best available data, models, and modeling methodologies and the assumptions that are most 

appropriate to adopt in the face of important uncertainties. The majority of the analytical 

assumptions used to develop the main estimates of benefits have been reviewed and approved 

by EPA’s independent Science Advisory Board (SAB). Both EPA and the SAB recognize that data 

and modeling limitations as well as simplifying assumptions can introduce significant 

uncertainty into the benefit results and that alternative choices exist for some inputs to the 

analysis, such as the concentration-response functions for mortality.

This appendix supplements our main analysis of benefits with five additional sensitivity 

calculations. The supplemental estimates examine sensitivity to both for physical effects issues 

(i.e., the structure of the cessation lag; estimates of the number of avoided cerebrovascular 

events, cardiovascular emergency department visits and cases of chronic bronchitis; and 

alternate effect estimates for cohorts in California) and valuation issues (i.e., the appropriate 

income elasticity, updated cost-of-illness estimates). We conducted these sensitivity analyses 

for an annual standard of 12 μg/m3 in conjunction with a 24-hour standard of 35 μg/m3 as an 

illustrative example. These supplemental estimates are not meant to be comprehensive. 

Rather, they reflect some of the key issues identified by EPA or commenters as likely to have a 

significant impact on total benefits, or they are health endpoints for which the health data are 

still evolving, or for which we lack an appropriate method to estimate the economic value. The 

individual income growth and lag adjustments in the tables should not simply be added 

together because 1) there may be overlap among the alternative assumptions, and 2) the joint 

probability among certain sets of alternative assumptions may be low.

5.B.1 Cessation Lag Structure for PM2.5-Related Premature Mortality

Based in part on prior advice from the EPA’s independent Science Advisory Board (SAB), 

EPA typically assumes that there is a time lag between reductions in particulate matter (PM) 

exposures in a population and the full realization of reductions in premature mortality. Within 

the context of benefits analyses, this term is often referred to as “cessation lag.” The existence 

of such a lag is important for the valuation of reductions in premature mortality because 

economic theory suggests that dollar-based representations of health effect incidence changes 

occurring in the future should be discounted.
5.B-2

Over the last 15 years, there has been a continuing discussion and evolving advice 

regarding the timing of changes in health effects following changes in ambient air pollution. It 

has been hypothesized that some reductions in premature mortality from exposure to ambient 

PM2.5 will occur over short periods of time in individuals with compromised health status, but 

other effects are likely to occur among individuals who, at baseline, have reasonably good 

health that will deteriorate because of continued exposure. No animal models have yet been 

developed to quantify these cumulative effects, nor are there epidemiologic studies bearing on 

this question. The SAB-HES has recognized this lack of direct evidence. However, in early advice, 

they also note that “although there is substantial evidence that a portion of the mortality effect 

of PM is manifest within a short period of time, i.e., less than one year, it can be argued that, if 

no lag assumption is made, the entire mortality excess observed in the cohort studies will be 

analyzed as immediate effects, and this will result in an overestimate of the health benefits of 

improved air quality. Thus some time lag is appropriate for distributing the cumulative mortality 

effect of PM in the population” (EPA-SAB-COUNCIL-ADV-00-001, 1999, p. 9). In more recent 

advice, the SAB-HES suggests that appropriate lag structures may be developed based on the 

distribution of cause-specific deaths within the overall all-cause estimate (EPA-SAB-COUNCILADV-04-002, 2004). They suggest that diseases with longer progressions should be 

characterized by longer-term lag structures, while air pollution impacts occurring in populations 

with existing disease may be characterized by shorter-term lags.

A key question is the distribution of causes of death within the relatively broad 

categories analyzed in the long-term cohort studies. Although it may be reasonable to assume 

the cessation lag for lung cancer deaths mirrors the long latency of the disease, it is not at all 

clear what the appropriate lag structure should be for cardiopulmonary deaths, which include 

both respiratory and cardiovascular causes. Some respiratory diseases may have a long period 

of progression, while others, such as pneumonia, have a very short duration. In the case of 

cardiovascular disease, there is an important question of whether air pollution is causing the 

disease, which would imply a relatively long cessation lag, or whether air pollution is causing 

premature death in individuals with preexisting heart disease, which would imply very short 

cessation lags. The SAB-HES provides several recommendations for future research that could 

support the development of defensible lag structures, including using disease-specific lag 

models and constructing a segmented lag distribution to combine differential lags across causes 

of death (EPA-SAB-COUNCIL-ADV-04-002, 2004). The SAB-HES indicated support for using “a 

Weibull distribution or a simpler distributional form made up of several segments to cover the 

response mechanisms outlined above, given our lack of knowledge on the specific form of the 

distributions” (EPA-SAB-COUNCIL-ADV-04-002, 2004, p. 24). However, they noted that “an 
5.B-3

important question to be resolved is what the relative magnitudes of these segments should 

be, and how many of the acute effects are assumed to be included in the cohort effect 

estimate” (EPA-SAB-COUNCIL-ADV-04-002, 2004, p. 24-25). Since the publication of that report 

in March 2004, EPA has sought additional clarification from this committee. In its follow-up 

advice provided in December 2004, this SAB suggested that until additional research has been 

completed, EPA should assume a segmented lag structure characterized by 30% of mortality 

reductions occurring in the first year, 50% occurring evenly over years 2 to 5 after the reduction 

in PM2.5, and 20% occurring evenly over the years 6 to 20 after the reduction in PM2.5 (EPACOUNCIL-LTR-05-001, 2004). The distribution of deaths over the latency period is intended to 

reflect the contribution of short-term exposures in the first year, cardiopulmonary deaths in the 

2- to 5-year period, and long-term lung disease and lung cancer in the 6- to 20-year period. 

Furthermore, in their advisory letter, the SAB-HES recommended that EPA include sensitivity 

analyses on other possible lag structures. In this appendix, we investigate the sensitivity of 

premature mortality-reduction related benefits to alternative cessation lag structures, noting 

that ongoing and future research may result in changes to the lag structure used for the main 

analysis.

In previous advice from the SAB-HES, they recommended an analysis of 0-, 8-, and 15-

year lags, as well as variations on the proportions of mortality allocated to each segment in the 

segmented lag structure (EPA-SAB-COUNCIL-ADV-00-001, 1999, (EPA-COUNCIL-LTR-05-001, 

2004). The 0-year lag is representative of EPA’s assumption in previous RIAs. The 8- and 15-year 

lags are based on the study periods from the Pope et al. (1995) and Dockery et al. (1993) 

studies, respectively.1 However, neither the Pope et al. nor Dockery et al. studies assumed any 

lag structure when estimating the relative risks from PM exposure. In fact, the Pope et al. and 

Dockery et al. analyses do not supporting or refute the existence of a lag. Therefore, any lag 

structure applied to the avoided incidences estimated from either of these studies will be an 

assumed structure. The 8- and 15-year lags implicitly assume that all premature mortalities 

occur at the end of the study periods (i.e., at 8 and 15 years).

In addition to the simple 8- and 15-year lags, we have added several additional 

sensitivity analyses examining the impact of assuming different allocations of mortality to the 

segmented lag of the type suggested by the SAB-HES. The first alternate lag structure assumes 

that more of the mortality impact is associated with chronic lung diseases or lung cancer and 

 1 Although these studies were conducted for 8 and 15 years, respectively, the choice of the duration of the study 

by the authors was not likely due to observations of a lag in effects but is more likely due to the expense of 

conducting long-term exposure studies or the amount of satisfactory data that could be collected during this 

time period.
5.B-4

less with acute cardiopulmonary causes. This illustrative lag structure (“alternate segmented”) 

is characterized by 20% of mortality reductions occurring in the first year, 50% occurring evenly 

over years 2 to 5 after the reduction in PM2.5, and 30% occurring evenly over the years 6 to 20 

after the reduction in PM2.5. The second alternate lag structure (“5-year distributed”) assumes 

the 5-year distributed lag structure used in previous analyses, which is equivalent to a threesegment lag structure with 50% in the first 2-year segment, 50% in the second 3-year segment, 

and 0% in the 6- to 20-year segment. The third alternate lag structure assumes a smooth 

negative exponential relationship between the reduction in exposure and the reduction in 

mortality risk, which is described in more detail below.

In 2004, SAB-HES (U.S. EPA-SAB, 2004) urged EPA to consider using smoothed lag 

distributions, incorporating information from the smoking cessation literature. In June 2010, 

the SAB-HES provided additional advice regarding alternate cessation lags (U.S. EPA-SAB, 2010). 

For PM2.5-related benefits, the SAB-HES continued to support the previous 20-year distributed 

lag as the main estimate. while recommending that EPA further examine additional exponential 

decay functions. Specifically, the SAB-HES suggested varying the rate constant with the risk 

coefficient from in the cohort studies. EPA intends to incorporate these new alternate cessation 

lag for PM2.5-related benefits in the final PM NAAQS RIA.

In response to these suggestions, EPA identified Röösli et al. (2005) as model that 

combines empirical data on the relationship between changes in exposure and changes in 

mortality and the timing of the cessation of those effects for the smooth decay function.2

Because an exponential model is often observed in biological systems, Röösli et al. (2005) 

developed a dynamic model that assumes that mortality risks decrease exponentially after 

exposure termination. This model assumes the form risk=exp-kt, where k is the time constant 

and t is the time after t0. The relative risk from air pollution (RR) at a given time (t) can be 

calculated from the excess relative risk (ERR) attributable to air pollution from PM cohort 

studies (ERR=RR-R0), as follows:

RR(t) = ERR × exp−kt + R0 (5.B.1)

where R0 is the baseline relative risk in the absence of air pollution (R0=1). After cessation of 

exposure, mortality will start to decline and approach the baseline level. The change in 

mortality (ΔM), in units of percent-years, can be derived from Equation (5.B.1) as follows:

 2 In the 2006 PM NAAQS RIA (U.S. EPA, 2006), EPA applied equations and the time constant from a conference 

presentation by Röösli et al. (2004). We have updated this sensitivity analysis in this assessment to reflect the 

published version in Röösli et al. (2005) and generated additional time constants. 
5.B-5

∆M = ERR × t − ∫ ERR × exp−ktdt t

0 (5.B.2)

Integrating Equation (5.B.2) gives:

∆M = ERR × t − ERR

k + ERRk

× exp−kt (5.B.3)

In order to calculate values for the time constant, k, we applied the ΔM values from the 

two intervention studies that provide data on the time course of the change in mortality along 

with the ERR values from cohort studies on PM2.5-related mortality. We applied the 

intervention studies by Clancy et al. (2002), which analyzed the change in mortality following 

the ban of coal sales in Dublin, and by Pope et al. (1992), which examined the change in 

mortality resulting from the closure of a steel mill in the Utah Valley. We applied effect 

estimates from the American Cancer Society (ACS) cohort by Krewski et al. (2002)3 and the Six 

Cities cohort by Laden et al. (2006). Applying combinations of these studies to equation 5.B.3 

generates four estimates of k that range from 0.05 to 1.24. For additional context, the time 

constant calculated using on a smoking cessation study (i.e., Leksell and Rabl (2001)) is in the 

middle of this range (k=0.10). For this sensitivity analysis, we applied a time constant of k=0.45 

as a reasonable parameter for the exponential decay function, but we acknowledge the range 

of estimates that we could have chosen. This k constant is calculated as the average of the 

average k constants corresponding to each cohort study.4 Table 5.B. 1 provides the time 

constants for each of these combinations and averages, and Figure 5.B.2 illustrates the 

exponential decay lag structures.

 3 The relative risk estimate from Krewski et al. (2009) (1.06 per 10 μg/m3 change in average PM2.5 exposure for allcause mortality) is the same as the risk estimate from Pope et al. (2002). 4 The general approach for calculating the time constants based on the combination of the intervention study and 

cohort study is consistent with the 812 analysis (U.S. EPA, 2011), which was reviewed by SAB. However, in this 

analysis we have applied a single time constant (k=0.45) rather than presenting the monetized benefits results 

for every exponential lag function applying the various time constants.
5.B-6

Table 5.B-1. Values of the Time Constant (k) for the Exponential Decay Lag Function

Value of k PM2.5 Cohort Study Intervention Study

0.05 H6C—Laden et al. (2006) Dublin—Clancy et al. (2002)

0.15 ACS—Krewski et al. (2009) Dublin—Clancy et al. (2002)

0.37 H6C—Laden et al. (2006) Utah Valley—Pope et al. (1992)

1.24 ACS—Krewski et al. (2009) Utah Valley—Pope et al. (1992)

0.70 Average k for ACS—Krewski et al. (2009)

0.21 Average k for H6C—Laden et al. (2006)

0.45 Average of average k for each cohort study

The estimated impacts of alternative lag structures on the monetary benefits associated 

with reductions in PM-related premature mortality (estimated using the effect estimate from 

Krewski et al. (2009)) are presented in Table 5.B-2. These monetized estimates are calculated 

using the value of a statistical life (i.e., $6.3 million per incidence adjusted for inflation and 

income growth) and are presented for both a 3 and 7% discount rate over the lag period). The 

choice of mortality risk study and mortality valuation approach are described in detail in 

Chapter 5 of this RIA. Figure 5.B.1 illustrates the cumulative distributions of the cessation lags 

applied in this appendix.

The results of this sensitivity analyses demonstrate that because of discounting of 

delayed benefits, the lag structure may also have a large impact on monetized benefits, 

reducing benefits by 27% if an extreme assumption that no effects occur until after 15 years is 

applied at a 3% discount rate and 53% at a 7% discount rate. However, for most reasonable 

distributed lag structures, differences in the specific shape of the lag function have relatively 

small impacts on overall benefits. For example, the overall impact of moving from the previous 

5-year distributed lag to the segmented lag recommended by the SAB-HES in 2004 in the main 

estimate is relatively modest, reducing benefits by approximately 5% when a 3% discount rate 

is used and 9% when a 7% discount rate is used. If no lag is assumed, benefits are increased by 

approximately 10% relative to the segmented lag at a 3% discount rate and 22% at a 7% 

discount rate.
5.B-7

Table 5.B-2. Sensitivity of Monetized PM2.5-Related Premature Mortality Benefits to 

Alternative Cessation Lag Structures, Using Effect Estimate from Krewski et al. 

(2009)

Alternative Lag Structures for PM-Related Premature Mortality

12/35

Value

(billion 

2006$)a.b

Percent 

Difference from 

Base Estimate

SAB Segmented 

(Main estimate)

30% of incidences occur in 1st year, 50% in years 2 to 5, 

and 20% in years 6 to 20

3% discount rate $2.3 N/A

7% discount rate $2.1 N/A

No lag Incidences all occur in the first year

3% discount rate $2.5 10.4%

7% discount rate $2.5 22.5%

8-year Incidences all occur in the 8th year

3% discount rate $2.1 −10.3%

7% discount rate $1.6 −23.7%

15-year Incidences all occur in the 15th year

3% discount rate $1.7 −27.0%

7% discount rate $1.0 −52.5%

Alternative 

Segmented

20% of incidences occur in 1st year, 50% in years 2 to 5, 

and 30% in years 6 to 20

3% discount rate $2.2 −3.2%

7% discount rate $1.9 −6.6%

5-Year Distributed 50% of incidences occur in years 1 and 2 and 50% in years 

2 to 5

3% discount rate $2.4 4.9%

7% discount rate $2.3 9.4%

Exponential Decay 

(k=0.45)

Incidences occur at an exponentially declining rate 

3% discount rate $2.4 5.0%

7% discount rate $2.3 9.9%

a Dollar values rounded to two significant digits. The percent difference using effect estimates from Laden et al. 

would be identical, but the value would be approximately 2.5 times higher.
5.B-8

Figure 5.B-1. Alternate Lag Structures for PM2.5 Premature Mortality (Cumulative)

Figure 5.B-2. Exponential Lag Structures for PM2.5 Premature Mortality (Cumulative)

0%

25%

50%

75%

100%

1st 

year

2nd 

year

3rd 

year

4th 

year

5th 

year

6th 

year

7th 

year

8th 

year

9th 

year

10th 

year

11th 

year

12th 

year

13th 

year

14th 

year

15th 

year

16th 

year

17th 

year

18th 

year

19th 

year

20th 

year

% Premature Mortality Occuring Within Year (Cumulative)

Year Following Reduction in PM2.5

 

SAB segmented lag (main estimate)

Alternate Segmented Lag

Exponential decay model

5-year distributed lag

0%

25%

50%

75%

100%

1st year

2nd year

3rd year

4th year5th year6th year7th year8th year9th year

10th year11th year12th year13th year14th year15th year16th year17th year18th year19th year20th year

21st year

22nd year

23rd year

24th year25th year26th year27th year28th year29th year30th year

% Premature Mortality Occuring Within Year (Cumulative)

Year Following Reduction in PM2.5

 

k=0.05 (H6C/Dublin)

k=0.37 (H6C/Utah)

k=0.15 (ACS/Dublin)

k=1.24 (ACS/Utah)

k=0.70 (Average ACS)

k=0.21 (Average H6C)

k=0.45 (Overall Average)

SAB Lag (Main Estimate)
5.B-9

5.B.2 Income Elasticity of Willingness to Pay

As discussed in Chapter 5, our estimates of monetized benefits account for growth in 

real GDP per capita by adjusting the WTP for individual endpoints based on the central estimate 

of the adjustment factor for each of the categories (minor health effects, severe and chronic 

health effects, premature mortality, and visibility). We examined how sensitive the estimate of 

total benefits is to alternative estimates of the income elasticities. Table 5.B-3 lists the ranges of 

elasticity values used to calculate the income adjustment factors, while Table 5.B-4 lists the 

ranges of corresponding adjustment factors. The results of this sensitivity analysis, giving the 

monetized benefit subtotals for the four benefit categories, are presented in Table 5.B-5.

Table 5.B-3. Ranges of Elasticity Values Used to Account for Projected Real Income Growtha

Benefit Category Lower Sensitivity Bound Upper Sensitivity Bound

Minor Health Effect 0.04 0.30

Premature Mortality 0.08 1.00

a Derivation of these ranges can be found in Kleckner and Neumann (1999). COI estimates are assigned an 

adjustment factor of 1.0.

Table 5.B-4. Ranges of Adjustment Factors Used to Account for Projected Real Income 

Growtha

Benefit Category Lower Sensitivity Bound Upper Sensitivity Bound

Minor Health Effect 1.018 1.147

Premature Mortality 1.037 1.591

a Based on elasticity values reported in Table C-4, U.S. Census population projections, and projections of real GDP 

per capita.

Table 5.B-5. Sensitivity of Monetized Benefits to Alternative Income Elasticitiesa

Benefit Category

Benefits Incremental to 15/35 Attainment Strategy (Millions of 2006$)

12/35

Lower Sensitivity Bound Upper Sensitivity Bound

Minor Health Effect $18 $20 

Premature Mortalityb $2,200 $3,300 

a All estimates rounded to two significant digits.

b Using mortality effect estimate from Krewski et al. (2009) and 3% discount rate. Results using Laden et al. (2006)

or a 7% discount rate would show the same proportional range.
5.B-10

Consistent with the impact of mortality on total benefits, the adjustment factor for 

mortality has the largest impact on total benefits. The value of mortality in 2020 ranges from 

96% to 108% of the main estimate based on the lower and upper sensitivity bounds on the 

income adjustment factor. The effect on the value of minor health effects is much less 

pronounced, ranging from 86% to 133% of the main estimate for minor effects.

5.B.3 Analysis of Cardiovascular Emergency Department Visits, Cerebrovascular Events and 

Chronic Bronchitis

Below we summarize the results of a sensitivity analysis of three health endpoints: 

cardiovascular emergency department visits, cerebrovascular events (stroke) and chronic 

bronchitis (Table 5.B-6). While in the benefits chapter we provide a full description of the 

rationale for treating these endpoints as a sensitivity, it is worth summarizing these reasons 

here. In the case of cardiovascular emergency department visits, we lack the necessary 

economic valuation functions to quantify the monetary value of these avoided cases. We treat 

cerebrovascular events as a sensitivity for three reasons: (1) the epidemiological literature 

examining PM-related cerebrovascular events is still evolving; (2) there are special uncertainties 

associated with quantifying this endpoint; (3) we have not yet identified an appropriate means 

for estimating the economic value of this endpoint. Finally, we now quantify chronic bronchitis 

as a sensitivity because of the absence of newer studies finding a relationship between longterm PM2.5 exposure and this endpoint.

To quantify cardiovascular hospital admissions, we apply risk coefficient drawn from 

Metzger et al. (2004) (RR= 1.033, 95% confidence intervals 1.01–1.056 per 10 μg/m3 PM2.5) and 

Tolbert et al. (2007) (RR= 1.005, 95% confidence intervals 0.993–1.017 per 10 μg/m3 PM2.5). To 

estimate cerebrovascular events, we apply a risk coefficient drawn from Miller et al. (2007) 

(RR= 1.28, 95% confidence intervals 1.02–1.61 per 10 μg/m3 PM2.5). To estimate chronic 

bronchitis, we use a risk coefficient drawn from Abbey et al. (1995) (RR= 1.81, 95% confidence 

intervals 0.98–3.25 per 45 μg/m3 PM2.5). Additional information, including the rationale for 

incorporating these new endpoints into the analysis, the baseline incidence rates for these 

endpoints, and the prevalence rate for chronic bronchitis are described in Chapter 5 of this RIA.
5.B-11

Table 5.B-6. Avoided Cases of Cardiovascular Emergency Department Visits, Stroke and 

Chronic Bronchitis in 2020 (95th percentile confidence intervals)*

Endpoint 12/35

Cardiovascular hospital admissions

Metzger et al. (2004)

(ages 0–99)

300

(180–480)

Tolbert et al. (2007)

(ages 0–99)

42

(−16–130)

Stroke 

Miller et al. (2007)

(ages 50–79)

77

(36–140)

Chronic Bronchitis

Abbey et al. (1995)

(ages 27–99)

220

(99–420)

* All estimates rounded to two significant digits.

5.B.4 New Hospitalization Cost-of-Illness Functions and Median Wage Data

As described in Chapter 5 of this RIA, we updated the cost-of-illness functions for 

hospitalizations. Specifically, we updated the estimates of hospital charges and lengths of 

hospital stays were based on discharge statistics provided by the Agency for Healthcare 

Research and Quality’s Healthcare Utilization Project National Inpatient Sample (NIS) database 

for 2000 (AHRQ, 2000) to 2007 (AHRQ, 2007). In addition, we updated the county-level median 

wage data reported by the 2007 American Community Survey (ACS) (Abt Associates, 2011). 

Using cost-of-illness functions for hospital admissions, which include updated charges, length of 

stay, and median wages, the rounded estimates of total monetized benefits do not change, but 

the monetary value of respiratory hospital admissions increases 3% and cardiovascular hospital 

admissions increase 2%. Because the median wages were updated, the valuation also changed 

the valuation for work loss days. It is important to note that while the national average median 

daily wage slightly decreased (i.e., approximately 2% in 2000$), the county-level median income 

increased slightly in the locations where PM2.5 levels improved for 12/35. Tables 5.B.7 and 5.B.8 

show the previous and current unit values, respectively. Table 5.B.9 shows the sensitivity of the 

monetized hospitalization benefits to this update.
5.B-12

Table 5.B-7. Unit Values for Hospital Admissions in BenMAP 4.0.51 (Abt Associates, 2011)a

End Point ICD Codes

Age Range

Mean Hospital 

Charge (2000$)

Mean Length 

of Stay (days)

Total Cost of Illness 

(Unit value in 

min. max. 2000$)

HA, All Cardiovascular 390–429 18 64 $26,654 4.12 $27,119

HA, All Cardiovascular 390–429 65 99 $24,893 4.88 $25,444

HA, All Respiratory 460–519 65 99 $20,667 6.07 $21,351

HA, Asthma 493 0 64 $9,723 3.00 $10,051

HA, Chronic Lung Disease 490–496 18 64 $12,836 3.90 $13,276

a National average median daily wage is $112.86 (2000$).

Table 5.B-8. Unit Values for Hospital Admissions in BenMAP 4.0.43 (Abt Associates, 2010)a

End Point ICD Codes

Age Range

Mean Hospital 

Charge (2000$)

Mean Length 

of Stay (days)

Total Cost of 

Illness (Unit value 

min. max. in 2000$)

HA, All Cardiovascular 390–429 20 64 $22,300 4.15 $22,778

HA, All Cardiovascular 390–429 65 99 $20,607 5.07 $21,191

HA, All Respiratory 460–519 65 99 $17,600 6.88 $18,393

HA, Asthma 493 0 64 $7,448 2.95 $7,788

HA, Chronic Lung Disease 490–496 20 64 $10,194 $5.92 $15,375

a National average median daily wage is $115.20 (2000$).

Table 5.B-9. Change in Monetized Hospitalization Benefits for 12/35

Endpoint

2000 AHRQ

(millions of 2006$)

2007 AHRQ

(millions of 2006$) Percent Change

Respiratory hospital admissions $2.3 $2.4 3.4%

Cardiovascular hospital admissions $3.1 $3.2 2.1%

Work loss days $6.7 $6.7 0.02%

* All estimates rounded to two significant digits.

5.B.5 Long-term PM2.5 Mortality Estimates using Cohort Studies in California

In Chapter 5, we described the multi-state cohort studies we used to estimate the PM2.5-

related mortality (i.e., Krewski et al., 2009; Laden et al., 2006), as well as summarized the effect 

estimates for additional cohort studies. In this appendix, we provide additional information 
5.B-13

about cohort studies in California.1 As shown in Table 5.x in the health benefits chapter, a large 

percentage of the monetized human health benefits associated with the illustrative control 

strategy to attain the alternative combination of standards are projected to occur in California. 

Specifically, for an annual PM2.5 standard of 12 μg/m3 in conjunction with retaining the 24-hour 

standard of 35 μg/m3, 70% of the total monetized benefits were estimated to occur in California

and 98% for an annual PM2.5 standard of 13 μg/m3. For this reason, we determined that it was 

appropriate to consider the sensitivity of the benefits results using effect estimates for cohorts 

in California specifically. Although we have not calculated the benefits results using these 

cohort studies, it is possible to use the effect estimates themselves to determine how much the 

monetized benefits in California would have changed if we used effect estimates from the 

California cohorts. Each of the California cohort studies are summarized in the PM ISA (and thus 

not summarized here) with the exception of the Ostro et al. (2010, 2011) studies, which we 

describe below. Table 5.B.10 provides the effect estimates from each of these cohort studies 

for all-cause, cardiovascular, cardiopulmonary, and ischemic heart disease (IHD) mortality for 

each of the California cohort studies.

Ostro et al. (2010) characterize the risk of premature death associated with long-term 

exposure to PM2.5 in California among a cohort of about 134,000 current and former female 

public school professionals (i.e., the California Teacher’s Study (CTS)). In this prospective cohort 

study, Ostro and colleagues estimated long-term PM exposure to several PM constituents, 

including elemental carbon, organic carbon, sulfates, nitrates, iron, potassium, silicon and zinc. 

In an erratum, Ostro et al. (2011) modified their approach to assigning PM2.5 levels to the 

cohort populations, noting that they “reanalyzed the CTS data using time-dependent pollution 

metrics—in which the exposure estimates for everyone remaining alive in the risk set were 

recalculated at the time of each death—in order to compare their average exposures up to that 

time with that of the individual who had died. In this way, decedents and survivors comprising 

the risk set had similar periods of pollution exposure, without subsequent pollution trends 

influencing the surviving women’s exposure estimates.” This change in assumption attenuated 

the hazard ratios significantly, though hazard ratios remained significant for cardiovascular 

mortality and total PM2.5 mass and certain constituents, nitrate and sulfate; no association was 

observed between all-cause mortality and total PM2.5 mass or its constituents. The authors note 

that these revised results are generally consistent with other long-term PM cohort studies, 

including the ACS and H6C studies.

 1 In addition to cohorts studies conducted in California, we have also identified a cross-sectional studies (Hankey 

et al., 2012). However, we have not summarized that study here.
5.B-14

Table 5.B-10. Summary of Effect Estimates From Associated With Change in Long-Term 

Exposure to PM2.5 in Recent Cohort Studies in California

Authors Cohort

Hazard Ratios per 10 μg/m3 Change in PM2.5

(95th percentile confidence interval)

All Causes Cardiopulmonary

Ischemic 

Heart Disease

McDonnell et al. (2000)a Adventist Health Study (AHS) 

cohort (age > 27)

1.09

(.98–1.24)

N/A N/A

Jerrett et al. (2005)b Subset of the ACS cohort living 

in the Los Angeles 

metropolitan area (age > 30)

1.15 

(1.03–1.29)

1.10 

(0.94–1.28)

1.32 

(1.03–1.29)

Chen et al. (2005)c Adventist Health Study (AHS) 

cohort living in San Francisco, 

South Coast (i.e., Los Angeles 

and eastward), and San Diego 

air basins (age > 25)

N/A N/A 1.42

(1.06–1.90)

Enstrom et al. (2005)d California Prevention Study 

(age >65)

1.04

(1.01–1.07)

N/A N/A

Krewski et al. (2009)e Subset of the ACS cohort living 

in the 5-county Los Angeles 

Metropolitan Statistical Area 

(age > 30)

1.42

(1.26–1.27)

1.11 

(0.95–1.23)

1.32

(1.06–1.64)

Ostro et al. (2010)c California Teacher’s study. 

Current and former female 

public school professionals 

(age > 22)

1.84

(1.66–2.05)

2.05

(1.80–2.36)

2.89

(2.27–3.67)

Ostro et al. (2011)c,f 1.06 

(0.96–1.16)

1.19 

(1.05–1.36)

1.55 

(1.24–1.93)

a Table 3, adjusted for 10 μg/m3 change in PM2.5.

b Table 1. 44 individual-level co-variates + all social (i.e., ecologic) factors specified (principal component analysis).

c Women only.

d Represents deaths occurring from 1973–1982, but no significant associations were reported with deaths in later 

time periods. The PM ISA (U.S. EPA, 2009) concludes that the use of average values for California counties as 

exposure surrogates likely leads to significant exposure error, as many California counties are large and quite 

topographically variable.

e Table 23. 44 individual-level co-variates + all social (i.e., ecologic) factors specified.

f Erratum Table 2.
5.B-15

As shown in Table 5.B.10, most of the cohort studies conducted in California report 

central effect estimates similar to the (nation-wide) all-cause mortality risk estimate we applied 

from Krewski et al. (2009) and Laden et al. (2006) albeit with wider confidence intervals. A 

couple cohort studies conducted in California indicate higher risks than the risk estimates we 

applied.

5.B.6 References

Abbey, David E et al. 1995. “Chronic Respiratory Symptoms Associated with Estimated LongTerm Ambient Concentrations of Fine Particulates less than 2.5 Microns in aerodynamic 

diameter (PM2.5) and Other Air Pollutants.” Journal of Exposure Analysis and 

Environmental Epidemiology 5(2): 137-158.

Abt Associates, Inc. 2010. BenMAP User’s Manual Appendices. Prepared for U.S. Environmental 

Protection Agency Office of Air Quality Planning and Standards. Research Triangle Park, 

NC. Available on the Internet at 

<http://www.epa.gov/oaqps001/benmap/models/BenMAPManualAppendicesAugust20

10.pdf>.

Abt Associates, Inc. 2011. BenMAP User’s Manual Appendices. Prepared for U.S. Environmental 

Protection Agency Office of Air Quality Planning and Standards. Research Triangle Park, 

NC. September. Available on the Internet at <

http://www.epa.gov/air/benmap/models/BenMAPAppendicesSeptember2011.pdf>.

Agency for Healthcare Research and Quality (AHRQ). 2000. HCUPnet, Healthcare Cost and 

Utilization Project. Rockville, MD. Available on the Internet at 

<http://hcupnet.ahrq.gov>.

Agency for Healthcare Research and Quality (AHRQ). 2007. HCUPnet, Healthcare Cost and 

Utilization Project. Rockville, MD. Available on the Internet at 

<http://hcupnet.ahrq.gov>.

Chen LH, Knutsen SF, Shavlik D, Beeson WL, Petersen F, Ghamsary M, et al. 2005. “The association between fatal coronary heart disease and ambient particulate air pollution: are 

females at greater risk?” Environ Health Perspect 113:1723–1729.

Clancy, L., P. Goodman, H. Sinclair, and D.W. Dockery. 2002. “Effect of Air-pollution Control on 

Death Rates in Dublin, Ireland: An Intervention Study.” Lancet Oct 19;360(9341):1210-4.

Desvousges, W.H., F.R. Johnson, and H.S. Banzhaf. 1998. Environmental Policy Analysis With 

Limited Information: Principles and Applications of the Transfer Method (New Horizons 

in Environmental Economics.) Edward Elgar Pub: London.
5.B-16

Dockery, D.W., C.A. Pope, X.P. Xu, J.D. Spengler, J.H. Ware, M.E. Fay, B.G. Ferris, and F.E. 

Speizer. 1993. “An Association between Air Pollution and Mortality in Six U.S. Cities.”

New England Journal of Medicine 329(24):1753-1759.

Enstrom JE 2005. “Fine particulate air pollution and total mortality among elderly Californians, 

1973-2002.” Inhal Toxicol 17: 803-816.

Hankey, S., J. D. Marshall, et al. (2011). “Health Impacts of the Built Environment: Within-Urban 

Variability in Physical Inactivity, Air Pollution, and Ischemic Heart Disease Mortality.” 

Environ Health Perspect 120(2).

Jerrett M, Burnett RT, Ma R, Pope CA III, Krewski D, Newbold KB, et al. 2005. “Spatial analysis of 

air pollution and mortality in Los Angeles.” Epidemiology 16(6):727–736.

Kleckner, N., and J. Neumann. 1999. “Recommended Approach to Adjusting WTP Estimates to 

Reflect Changes in Real Income.” Memorandum to Jim Democker, US EPA/OPAR. June 3, 

Available on the Internet at 

<http://www.epa.gov/ttn/ecas/regdata/Benefits/background/klecknerandneumann199

9.pdf>.

Krewski D, Jerrett M, Burnett RT, Ma R, Hughes E, Shi, Y, et al. 2009. “Extended follow-up and 

spatial analysis of the American Cancer Society study linking particulate air pollution and 

mortality.” HEI Research Report, 140, Health Effects Institute, Boston, MA.

Laden F, Schwartz J, Speizer FE, Dockery DW. 2006. “Reduction in fine particulate air pollution 

and mortality: extended follow-up of the Harvard Six Cities study.” Am J Respir Crit Care 

Med 173:667–672.

McDonnell WF; Nishino-Ishikawa N; Petersen FF; Chen LH; Abbey DE. 2000. “Relationships of 

mortality with the fine and coarse fractions of long-term ambient PM10 concentrations 

in nonsmokers.” J Expo Sci Environ Epidemiol, 10: 427-436.

Metzger, K. B., P. E. Tolbert, et al. (2004). “Ambient air pollution and cardiovascular emergency 

department visits.” Epidemiology 15(1): 46-56.

Miller, Kristin A., David S. Siscovick, Lianne Sheppard, Kristen Shepherd, Jeffrey H. Sullivan, 

Garnet L. Anderson, and Joel D. Kaufman. 2007. “Long-Term Exposure to Air Pollution 

and Incidence of Cardiovascular Events in Women.” New England Journal of Medicine. 

356 (5) :447-458.

Ostro B, Lipsett M, Reynolds P, Goldberg D, Hertz A, Garcia C, et al. 2010. “Long-Term Exposure 

to Constituents of Fine Particulate Air Pollution and Mortality: Results from the 

California Teachers Study.” Environ Health Perspect 118:363-369.

Ostro B, Reynolds P, Goldberg D, Hertz A, et al. 2011. “Assessing Long-Term Exposure in the 

California Teachers Study.” Environ Health Perspect June; 119(6): A242–A243.
5.B-17

Peters, A., D. W. Dockery, J. E. Muller and M. A. Mittleman. 2001. “Increased particulate air 

pollution and the triggering of myocardial infarction.” Circulation. Vol. 103 (23): 2810-5.

Pope, C.A., III, M.J. Thun, M.M. Namboodiri, D.W. Dockery, J.S. Evans, F.E. Speizer, and C.W. 

Heath, Jr. 1995. “Particulate Air Pollution as a Predictor of Mortality in a Prospective 

Study of U.S. Adults.” American Journal of Respiratory Critical Care Medicine 151:669-

674.

Röösli M, Kunzli N, Braun-Fahrlander C. 2004. “Use of Air Pollution ‘Intervention-Type’ Studies 

in Health Risk Assessment.” 16th Conference of the International Society for 

Environmental Epidemiology, New York, August 1-4, 2004.

Röösli M, Kunzli N, Braun-Fahrlander C, Egger M. 2005. “Years of life lost attributable to air 

pollution in Switzerland: dynamic exposure-response model.” International Journal of 

Epidemiology 34(5):1029-35.

Tolbert, P. E., M. Klein, et al. 2007. “Multipollutant modeling issues in a study of ambient air 

quality and emergency department visits in Atlanta.” J Expo Sci Environ Epidemiol 17 

Suppl 2: S29-35.

U.S. Environmental Protection Agency—Science Advisory Board (EPA-SAB). 1999a. The Clean Air 

Act Amendments (CAAA) Section 812 Prospective Study of Costs and Benefits (1999): 

Advisory by the Health and Ecological Effects Subcommittee on Initial Assessments of 

Health and Ecological Effects. Part 1. EPA-SAB-COUNCIL-ADV-99-012. July. Available on 

the Internet at 

<http://yosemite.epa.gov/sab%5CSABPRODUCT.NSF/F64A21824D19766885257193005

E51CA/$File/conadv12.pdf>.

U.S. Environmental Protection Agency—Science Advisory Board (EPA-SAB). 1999b. The Clean Air 

Act Amendments (CAAA) Section 812 Prospective Study of Costs and Benefits (1999): 

Advisory by the Health and Ecological Effects Subcommittee on Initial Assessments of 

Health and Ecological Effects. Part 2. EPA-SAB-COUNCIL-ADV-00-001. October. Available 

on the Internet at 

<http://yosemite.epa.gov/sab%5CSABPRODUCT.NSF/7D54675178C12703852571B9004

4B4F8/$File/coua0001.pdf>.

U.S. Environmental Protection Agency—Science Advisory Board (EPA-SAB). 2001. Review of the 

Draft Analytical Plan for EPA’s Second Prospective Analysis—Benefits and Costs of the 

Clean Air Act 1990-2020: An Advisory by a Special Panel of the Advisory Council on Clean 

Air Compliance Analysis. EPA-SAB-COUNCIL-ADV-01-004. September. Available on the 

Internet at 

<http://yosemite.epa.gov/sab%5CSABPRODUCT.NSF/572DC1989A3986CC8525718D006

BAB8B/$File/councila01004.pdf>.
5.B-18

U.S. Environmental Protection Agency—Science Advisory Board (EPA-SAB). 2004. Advisory on 

Plans for Health Effects Analysis in the Analytical Plan for EPA’s Second Prospective 

Analysis—Benefits and Costs of the Clean Air Act, 1990-2020: Advisory by the Health 

Effects Subcommittee of the Advisory Council on Clean Air Compliance Analysis. EPASAB-COUNCIL-ADV-04-002. March. Available on the Internet at 

<http://yosemite.epa.gov/sab%5CSABPRODUCT.NSF/08E1155AD24F871C85256E54004

33D5D/$File/council_adv_04002.pdf>.

U.S. Environmental Protection Agency Science Advisory Board (U.S. EPA-SAB). 2010. Review of 

EPA’s DRAFT Health Benefits of the Second Section 812 Prospective Study of the Clean Air

Act. EPA-COUNCIL-10-001. June. Available on the Internet at 

<http://yosemite.epa.gov/sab/sabproduct.nsf/9288428b8eeea4c885257242006935a3/

59e06b6c5ca66597852575e7006c5d09!OpenDocument&TableRow=2.3#2.>.
5.C-1

APPENDIX 5.C

QUALITATIVE ASSESSMENT OF UNCERTAINTY

Although we strive to incorporate as many quantitative assessments of uncertainty as 

possible, there are several aspects we are only able to address qualitatively. These aspects are 

important factors to consider when evaluating the relative benefits of the attainment strategies 

for each of the alternative standards: 

To more fully address all these uncertainties including those we cannot quantify, we 

apply a four-tiered approach using the WHO uncertainty framework (WHO, 2008), which 

provides a means for systematically linking the characterization of uncertainty to the 

sophistication of the underlying risk assessment. EPA has applied similar approaches in peerreviewed analyses of PM2.5-related impacts (U.S. EPA, 2010b, 2011a). In addition to the WHO 

uncertainty framework, we also include an assessment of how each aspect of uncertainty could 

affect the benefits results, including the direction of potential bias, the magnitude of impact on 

results, and the degree of confidence in our approach. In Table 5.C-1, we summarize the key 

uncertainties in the health benefits analysis, including our assessment of the direction of 

potential bias, magnitude of impact on the monetized benefits, degree of confidence in our 

analytical approach, and our ability to assess the source of uncertainty. Because this approach 

reflects a new application for regulatory benefits analysis, we request comments on this 

general approach as well as the specific uncertainty assessments.

5.C.1 Description of Classifications Applied in the Uncertainty Characterization

Uncertainty Characterization Tiers

The WHO framework (2008) defines 4 tiers of uncertainty characterization, which vary 

depending on the degree of quantification. In Table 5.C-1, we apply these tiers considering the 

degree of quantification of uncertainty we have conducted in this analysis or that we plan to 

conduct for the final RIA. Ultimately, the tier decision is professional judgment based on the 

availability of information.

 Tier 0—Screening level, generic qualitative characterization

 Tier 1—Scenario-specific qualitative characterization

 Tier 2—Scenario-specific sensitivity analysis
5.C-2

 Tier 3—Scenario-specific probabilistic assessment of individual and combined 

uncertainty

Magnitude of Impact

The magnitude of impact is an assessment of how much a plausible alternative 

assumption or approach could influence the overall monetary benefits. Similar classifications 

have been included in a previous analyses (U.S. EPA, 2010b, 2011a), but we have revised the 

category names and the cut-offs here.1 We note that PM2.5-related mortality benefits comprise 

over 98% of the monetized benefits in this analysis, thus alternative assumptions affecting 

mortality have the potential to have higher impacts on the total monetized benefits. Including 

currently omitted categories of benefits would lead to a reduction in the fraction of monetized 

benefits attributable to lower mortality risk. Ultimately, the magnitude decision is professional 

judgment based on the experience with various sensitivity analyses.

 High—If this uncertainty could influence the total monetized benefits by more than 25%

 Medium—If this uncertainty could influence the total monetized benefits by 5% to 25%

 Low—If this uncertainty could influence the total monetized benefits by less than 5%

Degree of Confidence in Our Analytic Approach

The degree of confidence is an assessment based on our assessment of the available 

body of evidence. That is, based on the given available evidence, how certain we are that the 

selected assumption is the most plausible of the alternatives. Similar classifications have been 

included in a previous analyses (U.S. EPA, 2010b, 2011a).2 Ultimately, the degree of confidence 

is professional judgment based on the volume and consistence of supporting evidence, much of 

 1

In The Benefits and Costs of the Clean Air Act from 1990 to 2020 (U.S. EPA, 2011a), EPA applied a classification of 

“potentially major” if a plausible alternative assumption or approach could influence the overall monetary 

benefit estimate by 5% percent or more and “probably minor.” if an alternative assumption or approach is likely 

to change the total benefit estimate by less than five percent. In the Quantitative Health Risk Assessment for 

Particulate Matter (U.S. EPA, 2010b), EPA applied classifications of “low” if the impact would not be expected to 

impact the interpretation of risk estimates in the context of the PM NAAQS review, “medium” if the impact had 

the potential to change the interpretation; “high” if it was are likely to influence the interpretation of risk in the 

context of the PM NAAQS review. 2 We have applied the same classification as The Benefits and Costs of the Clean Air Act from 1990 to 2020 (U.S. 

EPA, 2011a) in this analysis. In the Quantitative Health Risk Assessment for Particulate Matter (U.S. EPA, 2010b), 

EPA assessed the degree of uncertainty (low, medium, or high) associated with the knowledge-base (i.e., 

assessed how well we understand each source of uncertainty), but did not provide specific criteria for the 

classification.
5.C-3

which has been evaluated in the PM ISA.

 High—The current evidence is plentiful and strongly supports the selected approach

 Medium—Some evidence exists to support the selected approach, but data gaps are 

present

 Low—Limited data exists to support the selected approach
5.C-4

Table 5.C-1. Summary of Qualitative Uncertainty for Key Modeling Elements in PM2.5 Benefits

Potential Source of Uncertainty Direction of Potential Bias

Magnitude of Impact on 

Monetized Benefits

Degree of Confidence in Our 

Analytical Approach Ability to Assess Uncertainty

Uncertainties Associated with PM2.5 Concentration Changes

Projections of future levels of 

emissions and emissions 

reductions necessary to attain 

alternative standards

Both

Future expected emissions are 

difficult to predict because they 

depend on many independent 

factors. Emission inventories are 

aggregated from many spatially 

and technically diverse sources 

of emissions, so simplifying 

assumptions are necessary to 

make estimating the future 

tractable.

Medium Medium Tier 1

See Chapter 3

Responsiveness of air quality 

model to changes in precursor 

emissions from control scenarios

Both Medium-high Medium Tier 1

See Chapter 3

Air quality model chemistry, 

particularly for formation of 

ambient nitrate concentrations

Both Medium High Tier 1

See Chapter 3

Post-processing of air quality 

modeled concentrations to 

estimate future-year PM2.5 

design value and spatial fields of 

PM2.5 concentrations.

Both High High Tier 1

See Chapter 3

Uncertainties Associated with Concentration-Response Functions

Causal relationship between 

PM2.5 exposure and premature 

mortality

Overestimate, if no causal 

relationship

High

PM-mortality effects are the 

largest contributor to the 

monetized benefits. If the 

PM2.5/mortality relationship 

were not causal, benefits would 

be significantly overestimated.

High

The PM ISA (U.S. EPA, 2009b), 

which was twice peer reviewed 

by CASAC, evaluated the entire 

body of scientific literature and 

concluded that the relationship 

between both short-term and 

long-term exposure to PM2.5 and 

mortality is causal.

Tier 3

Experts included likelihood of 

causal relationship, so causality 

addressed in results derived from 

PM2.5 expert elicitation (Roman et 

al., 2008).

(continued)
5.C-5

Table 5.C-1. Summary of Qualitative Uncertainty for Key Modeling Elements in PM2.5 Benefits (continued)

Potential Source of Uncertainty Direction of Potential Bias

Magnitude of Impact on 

Monetized Benefits

Degree of Confidence in Our 

Analytical Approach Ability to Assess Uncertainty

Uncertainties Associated with Concentration-Response Functions (continued)

Modification of Mortality C-R 

function by socio-economic 

status (SES)

Potential underestimate for ACS 

cohort (Krewski et al., 2009) 

because of the demographics of 

that study population. Unknown 

for H6C cohort (Laden et al., 

2006)

Potentially medium-high for ACS 

cohort 

Unknown for H6C cohort

Medium

We only have mortality risk 

coefficients modified by 

educational attainment (Krewski, 

2000), not other risk modifiers 

such as income or race.

Tier 2

Effect modification for educational 

attainment evaluated in 

distributional analysis in Appendix 

5A.

Exposure misclassification in 

epidemiology studies

Underestimate (generally) 

Reducing exposure error can 

result in stronger associations 

between pollutants and effect 

estimates than generally 

observed in studies having less 

exposure detail.

Medium-high

Recent analyses reported in 

Krewski et al. (2009) 

demonstrate the potentially 

significant effect that this source 

of uncertainty can have on effect 

estimates. These analyses also 

illustrate the complexity and sitespecific nature of this source of 

uncertainty. 

High

The results from Krewski et al. 

(2009) and Jerrett et al. (2005) 

suggest that exposure error 

underestimates effect estimates 

(U.S. EPA, 2009b).

Tier 1

Spatial matching of air quality 

estimates from epidemiology 

studies to air quality estimates 

from air quality modeling

Unknown

Epidemiology studies often 

create a composite air quality 

monitor that is assumed to be 

representative of an entire urban 

area to estimate health risks, 

while benefits are often 

calculated using air quality 

modeling conducted at 12 km 

spatial resolution. This spatial 

mismatch could introduce 

uncertainty. 

Medium Medium-Low Tier 1

(continued)
5.C-6

Table 5.C-1. Summary of Qualitative Uncertainty for Key Modeling Elements in PM2.5 Benefits (continued)

Potential Source of Uncertainty Direction of Potential Bias

Magnitude of Impact on 

Monetized Benefits

Degree of Confidence in Our 

Analytical Approach Ability to Assess Uncertainty

Uncertainties Associated with Concentration-Response Functions (continued)

Variation in effect estimates 

reflecting differences in PM2.5

composition (mixtures)

Both Medium- High

Epidemiology studies examining 

regional differences in PM2.5-

related health effects have found 

differences in the magnitude of 

those effects. While these may 

be the result of factors other 

than composition (e.g., different 

degrees of exposure 

misclassification), composition 

remains one potential 

explanatory factor.

Medium Tier 1

Differential toxicity of particle 

components

Unknown

We assume that all fine particles, 

regardless of their chemical 

composition, are equally potent 

in causing premature mortality. 

Depending on the toxicity of 

each PM species reduced, this

could over or underestimate 

benefits.

Medium

If the benefits are due to a 

variety of PM species reduced, 

the magnitude of this 

uncertainty is likely to be small. If 

only one PM species is reduced, 

this uncertainty may have larger 

magnitude.

Medium-Low

The PM ISA (U.S. EPA, 2009b), 

which was twice peer reviewed 

by CASAC, evaluated the entire 

body of scientific literature and 

concluded that because there is 

no clear scientific evidence that 

would support the development 

of differential effects estimates 

by particle type (U.S. EPA, 

2009b).

Tier 2

To be assessed in final RIA

Application of C-R relationships 

only to those subpopulations 

matching the original study 

population

Underestimate

The C-R functions for several 

health endpoints were applied 

only to subgroups of the U.S. 

population (e.g., adults 30+ for 

mortality, children 8-12 for acute 

bronchitis), and thus this may 

underestimate the whole 

population benefits of reductions 

in pollutant exposures. 

Low

The baseline mortality rate for 

PM-related health effects is 

significantly lower in those under 

the age of 30. Mortality 

valuation generally dominates 

monetized benefits.

High

Our approach follows 

recommendations from the NAS 

(NRC, 2002)

Tier 2

To be assessed in final RIA

(continued)
5.C-7

Table 5.C-1. Summary of Qualitative Uncertainty for Key Modeling Elements in PM2.5 Benefits (continued)

Potential Source of Uncertainty Direction of Potential Bias

Magnitude of Impact on 

Monetized Benefits

Degree of Confidence in Our 

Analytical Approach Ability to Assess Uncertainty

Uncertainties Associated with Concentration-Response Functions (continued)

Shape of the C-R functions, 

particularly at low 

concentrations

Both

If there is a threshold (i.e., a level 

of exposure below which health 

effects do not occur), then the 

relative risk (i.e., steeper slope) 

estimates would be higher within 

the range of observed effects. 

Medium 

For PM2.5-related long-term 

mortality, the PM ISA concludes 

that a log-linear non-threshold 

model is best supported in the 

scientific literature (U.S. EPA, 

2009b). Although consideration 

for alternative model forms 

(Krewski et al., 2009) does 

suggest that different models 

can impact effect estimates to a 

certain extent, generally this 

appears to be a moderate source 

of overall uncertainty. 

High

Our approach follows 

recommendations from the SAB 

(U.S. EPA-SAB, 2010a)

Tier 3

Assessed in LML assessment and 

the results derived from the expert 

elicitation

Impact of historical exposure on 

long-term effect estimates

Both

Long-term studies of mortality 

suggest that different time 

periods of PM exposure can 

produce significantly different 

effects estimates, raising the 

issue of uncertainty in relation to 

determining which exposure 

window is most strongly 

associated with mortality.

Medium

The Reanalysis II study (HEI, 

2009) which looked at exposure 

windows (1979-1983 and 1999-

2000) for long-term exposure in 

relation to mortality, did not 

draw any conclusions as to which 

window was more strongly 

associated with mortality. 

However, the study did suggest 

that moderately different effects 

estimates are associated with 

the different exposure periods 

(with the more recent period 

having larger estimates). Overall, 

the evidence for determining the 

window over which the mortality 

effects of long-term pollution 

exposures occur suggests a 

latency period of up to five years, 

with the strongest results 

observed in the first few years 

after intervention (PM ISA, 

section 7.6.4. p. 7-95). 

Medium

See PM risk assessment (U.S. 

EPA, 2010b)

Tier 2

To be assessed in final RIA

(continued)
5.C-8

Table 5.C-1. Summary of Qualitative Uncertainty for Key Modeling Elements in PM2.5 Benefits (continued)

Potential Source of Uncertainty Direction of Potential Bias

Magnitude of Impact on 

Monetized Benefits

Degree of Confidence in Our 

Analytical Approach Ability to Assess Uncertainty

Uncertainties Associated with Concentration-Response Functions (continued)

Confounding by co-pollutants Both Medium

For long-term health endpoints, 

the final ISA states, “Given 

similar sources for multiple 

pollutants (e.g., traffic), 

disentangling the health 

responses of co-pollutants is a 

challenge in the study of ambient 

air pollution.” The PM ISA also 

notes that in some instances, 

consideration of co-pollutants 

can have a significant impact on 

effect estimates. 

For morbidity, the PM ISA 

concludes that observed 

associations are fairly robust to 

the inclusion of co-pollutants in 

the predictive models (see PM 

ISA). 

Medium Tier 1

Confounding by ecologic factors, 

such as SES or smoking

Both Medium Medium-High

To minimize confounding, we 

selected the risk coefficient that 

controlled for ecologic factors 

from Krewski et al. (2009).

Tier 1

Exclusion of C-R functions from

short-term exposure studies in 

PM mortality calculations

Underestimate Medium

PM/mortality is the top 

contributor to the benefits 

estimate. If short-term functions 

contribute substantially to the 

overall PM-related mortality 

estimate, then the benefits could 

be underestimated.

Medium

Long-term PM exposure studies 

likely capture a large part of the 

impact of short-term peak 

exposure on mortality; however, 

the extent of overlap between 

the two study types is unclear.

Tier 1

(continued)
5.C-9

Table 5.C-1. Summary of Qualitative Uncertainty for Key Modeling Elements in PM2.5 Benefits (continued)

Potential Source of Uncertainty Direction of Potential Bias

Magnitude of Impact on 

Monetized Benefits

Degree of Confidence in Our 

Analytical Approach Ability to Assess Uncertainty

Uncertainties Associated with Valuation

Value-of-a-Statistical-Life (VSL) Both

Some studies suggest that EPA’s 

VSL is too high, while other 

studies suggest that it is too low. 

The VSL used by EPA is based on 

26 labor market and stated 

preference studies published 

between 1974 and 1991.

High

Mortality valuation generally 

dominates monetized benefits.

Medium 

EPA is in the process of reviewing 

this estimate and will issue 

revised guidance based on the 

most up-to-date literature and 

recommendations from the SABEEAC in the near future.

Tier 2

Assessed uncertainty in mortality 

valuation using a Weibull 

distribution. 

Cessation lag structure for long 

term PM mortality

Underestimate

Recent studies (Schwartz, 2008) 

have shown that the majority of 

the risk occurs within 2 years of 

reduced exposure. EPA’s current 

lag structure assumption was 

provided by the SAB, and it 

estimates that 30% of mortality 

reductions in the first year, 50% 

over years 2 to 5, and 20% over 

the years 6 to 20 after the 

reduction in PM2.5 (U.S. EPA-SAB, 

2004c).

Medium

Although the cessation lag does 

not affect the number of 

premature deaths attributable to 

PM2.5 exposure, it affects the 

timing of those deaths and thus 

the discounted monetized 

benefits.

Medium

The main cessation lag applied 

was recently confirmed by the 

SAB (U.S. EPA-SAB, 2010a).

Tier 2

Assessed in sensitivity analysis

(continued)
5.C-10

Table 5.C-1. Summary of Qualitative Uncertainty for Key Modeling Elements in PM2.5 Benefits (continued)

Potential Source of Uncertainty Direction of Potential Bias

Magnitude of Impact on 

Monetized Benefits

Degree of Confidence in Our 

Analytical Approach Ability to Assess Uncertainty

Uncertainties Associated with Valuation (continued)

Morbidity valuation Underestimate

Morbidity benefits such as 

hospital admissions and heart 

attacks are calculated using costof-illness (COI) estimates, which 

studies have shown (Alberini and 

Krupnick, 2000) are generally half 

as much as willingness-to-pay to 

avoid the illness. in addition, the 

quantified morbidity impacts do 

not reflect physiological 

responses or sequelae events, 

such as increased susceptibility 

for future morbidity.

Low

Mortality valuation generally 

dominates monetized benefits. 

Low

Although the COI estimates for 

hospitalizations reflect recent 

data, other COI estimates such as 

for AMI have not yet been 

updated. Nevertheless, even 

current COI valuation estimates 

do not capture the full valuation 

of these morbidity impacts.

Tier 1

Income growth adjustments Both

Income growth increases 

willingness-to-pay valuation 

estimates, including mortality, 

over time. From 1997 to 2010, 

personal income and GDP growth 

have begun to diverge If this 

trend continues, the assumption 

that per capita GDP growth is a 

reasonable proxy for income 

growth may lead to an 

overstatement of benefits. (IEc, 

2012).

Medium

Income growth from 1990 to 

2020 increases mortality 

valuation by 20%. Alternate 

estimates for this adjustment 

vary by 20%(IEc, 2012).

Medium

Adjusting for income growth is 

consistent with SAB 

recommendations (U.S. EPA,-

SAB, 2000). Difficult to forecast 

future income growth. However, 

in the absence of readily 

available income data 

projections, per capita GDP is the 

best available option.

Tier 2

To be assessed in final RIA

(continued)
5.C-11

Table 5.C-1. Summary of Qualitative Uncertainty for Key Modeling Elements in PM2.5 Benefits (continued)

Potential Source of Uncertainty Direction of Potential Bias

Magnitude of Impact on 

Monetized Benefits

Degree of Confidence in Our 

Analytical Approach Ability to Assess Uncertainty

Uncertainties Associated with Baseline Incidence and Population

Uncertainty in projecting 

baseline incidence rates for 

mortality

Both 

Baseline mortality rates are at 

the county level and projected 

for 5-year increments for 

multiple age groups. Due to data 

suppression for small numbers of 

specific 

age/gender/race/ethnicity 

combinations, many counties 

have missing baseline mortality 

rates.

Medium

Mortality valuation generally 

dominates monetized benefits. 

The county-level baseline 

mortality rates reflect recent 

databases (i.e., 2004-2006). Also, 

the mortality rates projections for 

future years are internally 

consistent with population 

projections in that they reflect 

changes in mortality patterns as 

well as population growth.

Medium-High

The mortality rate databases 

(CDC, 2008) are generally 

considered to have relatively low 

uncertainty. These projections 

account for both spatial and 

temporal changes.

Tier 1

Uncertainty in projecting 

baseline incidence rates and 

prevalence rates or morbidity

Both

Morbidity baseline incidence is 

available for year 2000 only (i.e., 

no projections available). 

Low

Mortality valuation generally 

dominates monetized benefits. 

The magnitude of uncertainty 

associated with projections of 

morbidity baseline incidence 

varies with the health endpoint. 

Some endpoints such as 

hospitalizations and ER visits have 

more recent data (i.e., 2007) 

stratified by age and geographic 

location. Other endpoints, such as 

respiratory symptoms reflect one 

national average.

Low

There is no current method for 

projecting baseline morbidity 

rates beyond 2000.

Asthma prevalence rates reflect 

recent increases in baseline 

asthma rates (i.e., 2008).

Tier 1

(continued)
5.C-12

Table 5.C-1. Summary of Qualitative Uncertainty for Key Modeling Elements in PM2.5 Benefits (continued)

Potential Source of Uncertainty Direction of Potential Bias

Magnitude of Impact on 

Monetized Benefits

Degree of Confidence in Our 

Analytical Approach Ability to Assess Uncertainty

Uncertainties Associated with Baseline Incidence and Population (continued)

Population estimates and 

projections

Both

The monetized benefits would 

change in the same direction as 

the over or underestimate in 

population projections in areas 

where exposure changes. 

Low –Medium

Monetized benefits are 

substantially affected by 

population density. Comparisons 

using historical census data show 

that population projections are 

+/- 5% nationally, but projections 

accuracy can vary by locality. 

Medium

These projections cannot account 

for future population migration 

due to possible catastrophic 

events. 

Tier 1

Uncertainties Associated with Omitted Categories

Unquantified PM health benefit 

categories, such as pulmonary 

function, cerebrovascular events 

or low birth weight

Underestimate Medium 

Mortality valuation generally 

dominates monetized benefits, 

but it is possible that some of 

these omitted categories could 

be significant, especially for 

morbidity.

Low

Current data and methods are 

insufficient to develop (and 

value) national quantitative 

estimates of the health effects of 

these pollutants.

Tier 1

Unquantified health benefit 

categories for components of 

PM, such as air toxics (organics 

and metals)

Underestimate Medium

Studies have found air toxics 

cancer risks to be orders of 

magnitude lower than overall 

risks from criteria pollutants. 

However, air toxics can also be 

associated with cardiovascular, 

reproductive, respiratory, 

developmental, and neurological 

risks with potentially synergistic 

effects. 

Low

Current data and methods are 

insufficient to develop (and 

value) national quantitative 

estimates of the health effects of 

these pollutants.

Tier 1
5.C-13

5.C.2 References

Alberini, Anna and Alan Krupnick. 2000. “Cost-of-Illness and Willingness-to-Pay Estimates of the 

Benefits of Improved Air Quality: Evidence from Taiwan. “Land Economics

Vol. 76, No. 1 (Feb), pp. 37-53.

Centers for Disease Control and Prevention (CDC). 2008. National Center for Health Statistics. 

National Health Interview Survey, 1999-2008.

Industrial Economics, Incorporated (IEc). 2012. Updating BenMAP Income Elasticity Estimates—

Literature Review. Memo to Neal Fann. March. Available on the Internet at 

<http://www.epa.gov/ttn/ecas/regdata/Benefits/Income%20Elasticity%20Update_Reco

mmendations_noAppD.pdf>

Jerrett M, Burnett RT, Ma R, et al. 2005. “Spatial analysis of air pollution and mortality in Los 

Angeles.” Epidemiology 16:727-736.

Krewski D, Jerrett M, Burnett RT, Ma R, Hughes E, Shi, Y, et al. 2009. “Extended follow-up and 

spatial analysis of the American Cancer Society study linking particulate air pollution and 

mortality.” HEI Research Report, 140, Health Effects Institute, Boston, MA.

Laden, F., J. Schwartz, F.E. Speizer, and D.W. Dockery. 2006. “Reduction in Fine Particulate Air 

Pollution and Mortality.” American Journal of Respiratory and Critical Care Medicine

173:667-672.

National Research Council (NRC). 2002. Estimating the Public Health Benefits of Proposed Air 

Pollution Regulations. Washington, DC: The National Academies Press. Washington, DC.

Roman, Henry A., Katherine D. Walker, Tyra L. Walsh, Lisa Conner, Harvey M. Richmond, Bryan 

J. Hubbell, and Patrick L. Kinney. 2008. “Expert Judgment Assessment of the Mortality 

Impact of Changes in Ambient Fine Particulate Matter in the U.S.” Environ. Sci. Technol., 

42(7):2268-2274.

Schwartz J, Coull B, Laden F. 2008. “The Effect of Dose and Timing of Dose on the Association 

between Airborne Particles and Survival.” Environmental Health Perspectives 116: 64-

69.

U.S. Environmental Protection Agency (U.S. EPA). 2009b. Integrated Science Assessment for 

Particulate Matter (Final Report). EPA-600-R-08-139F. National Center for 

Environmental Assessment—RTP Division. December. Available on the Internet at 

<http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=216546>.

U.S. Environmental Protection Agency (U.S. EPA). 2010b. Quantitative Health Risk Assessment 

for Particulate Matter—Final Report. EPA-452/R-10-005. Office of Air Quality Planning 

and Standards, Research Triangle Park, NC. September. Available on the Internet at 

<http://www.epa.gov/ttnnaaqs/standards/pm/data/PM_RA_FINAL_June_2010.pdf>.
5.C-14

U.S. Environmental Protection Agency (U.S. EPA). 2011a. The Benefits and Costs of the Clean Air 

Act 1990 to 2020: EPA Report to Congress. Office of Air and Radiation, Office of Policy, 

Washington, DC. March. Available on the Internet at 

<http://www.epa.gov/oar/sect812/feb11/fullreport.pdf>.

U.S. Environmental Protection Agency Science Advisory Board (U.S. EPA-SAB). 2010a. Review of 

EPA’s DRAFT Health Benefits of the Second Section 812 Prospective Study of the Clean Air

Act. EPA-COUNCIL-10-001. June. Available on the Internet at 

<http://yosemite.epa.gov/sab/sabproduct.nsf/9288428b8eeea4c885257242006935a3/

59e06b6c5ca66597852575e7006c5d09!OpenDocument&TableRow=2.3#2.>.

U.S. Environmental Protection Agency—Science Advisory Board (U.S. EPA-SAB). 2004c. Advisory 

Council on Clean Air Compliance Analysis Response to Agency Request on Cessation Lag.

EPA-COUNCIL-LTR-05-001. December. Available on the Internet at 

<http://yosemite.epa.gov/sab/sabproduct.nsf/0/39F44B098DB49F3C85257170005293E

0/$File/council_ltr_05_001.pdf>.

World Health Organization (WHO). 2008. Part 1: Guidance Document on Characterizing and 

Communicating Uncertainty in Exposure Assessment, Harmonization Project Document 

No. 6. Published under joint sponsorship of the World Health Organization, the 

International Labour Organization and the United Nations Environment Programme. 

WHO Press: Geneva, Switzerland. Available on the Internet at 

<www.who.int/ipcs/methods/harmonization/areas/uncertainty%20.pdf>. 
6-1

CHAPTER 6

WELFARE BENEFITS ANALYSIS APPROACH

6.1 Important Caveats Regarding this Chapter

Due to data limitations for this proposed rule, we were unable to calculate changes in 

light extinction associated with emission reductions from the illustrative control strategies, 

which are necessary for calculating the visibility benefits. Instead, this chapter and associated 

appendix describe in detail the methodology for calculating visibility benefits to encourage 

comment on the revised approach.

6.2 Synopsis

Emission reductions associated with the illustrative control strategies to attain 

alternative combinations of the PM NAAQS have numerous documented effects on 

environmental quality that affect human welfare, including changes in visibility, materials 

damage, ecological effects from PM deposition, ecological effects from nitrogen and sulfur 

emissions, vegetation effects from ozone exposure, ecological effects from mercury deposition, 

and climate effects. Even though the primary standards are designed to protect against adverse 

effects to human health, the emission reductions have welfare co-benefits in addition to the 

direct human health benefits. Due to data limitations for this proposed rule, we are unable to 

estimate the recreational visibility and residential visibility benefits associated for alternative 

standard combinations in 2020 even though we have a complete methodology for estimating 

benefits for scenarios with light extinction estimates for both the baseline and control 

scenarios. We intend to apply the approach described in this chapter in the RIA accompanying 

the final rulemaking, and as such, we solicit comment here. Despite our goal to quantify and 

monetize as many of the benefits as possible, welfare benefits remain unquantified and 

nonmonetized in this analysis due to data, methodology, and resource limitations. The 

monetized value of these unquantified effects is represented by adding an unknown “B” to the 

aggregate total benefits. These unquantified welfare benefits may be substantial, although the 

magnitude of these benefits is highly uncertain.

6.3 Introduction to Welfare Benefits Analysis

Emission reductions associated with the illustrative control strategies to attain 

alternative combinations of the PM NAAQS have numerous documented effects on 

environmental quality that affect human welfare. We define welfare effects to include any nonhealth effects, including direct damages to property, either through impacts on material 

structures or by soiling of surfaces, direct economic damages in the form of lost productivity of 
6-2

crops and trees, indirect damages through alteration of ecosystem functions, and indirect 

economic damages through the loss in value of recreational experiences or the existence value 

of important resources. EPA’s Integrated Science Assessments for PM (hereafter, “PM ISA”) 

(U.S. EPA, 2009b) and NOX/SOX—Ecological Criteria (U.S. EPA, 2008), as well as the Criteria 

Document for ozone (U.S. EPA, 2006) identify numerous physical and ecological effects known 

to be causally linked to these pollutants. This chapter describes these individual effects and 

how we would quantify and monetize them if there is enough data to do so. These welfare 

effects include changes in visibility, materials damage, ecological effects from PM deposition, 

ecological effects from nitrogen and sulfur emissions, vegetation effects from ozone exposure, 

ecological effects from mercury deposition, and climate effects.

These welfare benefits are associated with reductions in emissions of specific pollutants 

resulting from emissions controls applied to attain the suite of PM standards, not the form or 

intent of any specific standard. Even though the primary standards are designed to protect 

against adverse effects to human health, the emission reductions have welfare co-benefits in 

addition to the direct human health benefits.

The impacts of emission reductions associated with the illustrative control strategies can 

be grouped into four categories: directly emitted PM (e.g., metals, organic compounds, dust), 

reductions of PM2.5 precursors (e.g., NOx, SOx, VOCs), other ancillary reductions from 

illustrative control strategies (e.g., mercury and CO2), and secondary co-pollutant formation 

from PM precursors (e.g., ozone from NOx and VOCs). Regardless of the category, these 

emission changes are anticipated to affect ambient concentrations and deposition, and 

consequently affect public welfare. It is therefore appropriate and reasonable to include all the 

benefits associated with these emission reductions to provide a comprehensive understanding 

of the likely public impacts of attaining alternative standard level combinations. Table 6-1 

shows the welfare effects associated with the various pollutants (either directly or as a 

precursor to secondary formation of PM or ozone) that would be reduced by the illustrative 

control strategies to attain the alternative standard level combinations.

Based on previous EPA analyses, we believe the welfare benefits associated with these 

non-health benefit categories could be significant (U.S. EPA, 2011b). Despite our goal to 

quantify and monetize as many of the benefits as possible, welfare benefits remain 

unquantified and nonmonetized in this analysis due to data, methodology, and resource 

limitations. For the final rulemaking, we anticipate that visibility would be the only welfare 

benefit category with sufficient data to quantify monetized benefits. Although it is possible to 

estimate some of the acidification and ozone vegetation benefits, we are limited by the time
6-3

Table 6-1. Welfare Effects by Pollutants Potentially Affected by Attainment of the PM 

NAAQS

Pollutant

Atmospheric Effects

Atmospheric and 

Deposition Effects Deposition Effects

Visibility 

Impairment

Vegetation 

Injury 

(SO2)

Vegetation 

Injury 

(Ozone)

Materials 

Damage Climate

Ecosystem 

Effects—

(Organics 

& Metals)

Acidification 

(freshwater)

Nitrogen 

Enrichment

Mercury 

Methylation

Direct 

PM2.5

   

NOx      

SO2      

VOCs    

PM10   

Hg  

CO2 

 = Welfare category affected by this pollutant.

and resources available, and we do not anticipate being able to quantify these benefits in the 

final rulemaking. The other welfare effects have additional data and methodology limitations 

that preclude us from monetizing those benefits. Therefore, the total benefits would be larger 

than we have estimated in this analysis. The monetized value of these unquantified effects is 

represented by adding an unknown “B,” which includes both unmonetized health and welfare 

effects, to the aggregate total for the cost-benefit comparison. These unquantified benefits 

may be substantial, although the magnitude of these benefits is highly uncertain. For these 

categories of welfare benefits that we are unable to quantify in this analysis, we include a 

qualitative analysis of the anticipated effects in this chapter to characterize the type and 

potential extent of those benefits. In Table 6-2, we identify the quantified and unquantified 

welfare benefits.

The remainder of this chapter is organized as follows: Section 6.3 provides the 

methodology for the visibility benefits analysis. Sections 6.4 through 6.6 provide qualitative 

benefits for the unquantified benefits categories of materials damage, climate, and ecosystem 

benefits. References are provided in Section 6.7. Additional information regarding technical 

details of the visibility benefits analysis is provided in Appendix 6a.
6-4

Table 6-2. Quantified and Unquantified Welfare Benefits

Benefits Category Specific Effect

Effect Has 

Been 

Quantified

Effect Has 

Been 

Monetized

More 

Information

Improved Environment

Reduced visibility impairment

Visibility in Class I areas in SE, SW, 

and CA regions –

1 –1 Section 6.3

Visibility in Class I areas in other 

regions – –

4 Section 6.3

Visibility in 8 cities –

1 –1 Section 6.3

Visibility in other residential areas – –

4 Section 6.3

Reduced climate effects

Global climate impacts from CO2 – – SCC TSD1

Climate impacts from ozone and 

PM – –

Ozone CD, Draft 

Ozone ISA, PM 

ISA2

Other climate impacts (e.g., other 

GHGs, other impacts) – – IPCC2

Reduced effects on materials

Household soiling – – PM ISA2

Materials damage (e.g., corrosion, 

increased wear) – – PM ISA2

Reduced effects from PM 

deposition (metals and 

organics)

Effects on Individual organisms 

and ecosystems – – PM ISA2

Reduced vegetation and 

ecosystem effects from 

exposure to ozone

Visible foliar injury on vegetation – – Ozone CD, Draft 

Ozone ISA2

Reduced vegetation growth and 

reproduction – – Ozone CD, Draft 

Ozone ISA1

Yield and quality of commercial 

forest products and crops – – Ozone CD, Draft 

Ozone ISA1,3

Damage to urban ornamental 

plants – – Ozone CD, Draft 

Ozone ISA2

Carbon sequestration in terrestrial 

ecosystems – – Ozone CD, Draft 

Ozone ISA2

Recreational demand associated 

with forest aesthetics – – Ozone CD, Draft 

Ozone ISA2

Other non-use effects Ozone CD, Draft 

Ozone ISA2

Ecosystem functions (e.g., water 

cycling, biogeochemical cycles, net 

primary productivity, leaf-gas 

exchange, community 

composition)

– – Ozone CD, Draft 

Ozone ISA2

(continued)
6-5

Table 6-2. Quantified and Unquantified Welfare Benefits (continued)

Benefits Category Specific Effect

Effect Has 

Been 

Quantified

Effect Has 

Been 

Monetized

More 

Information

Improved Environment (continued)

Reduced effects from acid 

deposition

Recreational fishing – – NOx SOx ISA1

Tree mortality and decline – – NOx SOx ISA2

Commercial fishing and forestry 

effects – – NOx SOx ISA2

Recreational demand in terrestrial 

and aquatic ecosystems – – NOx SOx ISA2

Other non-use effects NOx SOx ISA2

Ecosystem functions (e.g., 

biogeochemical cycles) – – NOx SOx ISA2

Reduced effects from 

nutrient enrichment

Species composition and 

biodiversity in terrestrial and 

estuarine ecosystems

– – NOx SOx ISA2

Coastal eutrophication – – NOx SOx ISA2

Recreational demand in terrestrial 

and estuarine ecosystems – – NOx SOx ISA2

Other non-use effects NOx SOx ISA2

Ecosystem functions (e.g., 

biogeochemical cycles, fire 

regulation)

– – NOx SOx ISA2

Reduced vegetation effects 

from ambient exposure to 

SO2 and NOx

Injury to vegetation from SO2

exposure – – NOx SOx ISA2

Injury to vegetation from NOx

exposure – – NOx SOx ISA2

Reduced ecosystem effects 

from exposure to 

methylmercury (through the 

role of sulfate in 

methylation)

Effects on fish, birds, and 

mammals (e.g., reproductive 

effects)

– – Mercury Study 

RTC2,3

Commercial, subsistence and 

recreational fishing – – Mercury Study 

RTC2

1 We assess these benefits qualitatively due to time and resource limitations for this analysis.

2 We assess these benefits qualitatively because we do not have sufficient confidence in available data or methods.

3 We assess these benefits qualitatively because current evidence is only suggestive of causality or there are other 

significant concerns over the strength of the association.

4 We quantify these benefits in a sensitivity analysis, but not the main analysis.
6-6

6.4 Visibility Benefits

6.4.1 Visibility and Light Extinction

The illustrative strategies designed to attain alternative standard level combinations 

would reduce emissions of directly emitted PM2.5 as well as precursor emissions such as NOx

and SO2. These emission reductions would improve the level of visibility throughout the United 

States because these suspended particles and gases impair visibility by scattering and absorbing 

light (U.S. EPA, 2009b).1 Visibility is also referred to as visual air quality (VAQ),2 and it directly 

affects people’s enjoyment of a variety of daily activities (U.S. EPA, 2009b). Good visibility 

increases quality of life where individuals live and work, and where they travel for recreational 

activities, including sites of unique public value, such as the Great Smoky Mountains National 

Park (U. S. EPA, 2009b). This section discusses the economic benefits associated with improved 

visibility as a result of emission reductions associated with the alternative PM2.5 standard level 

combinations.

Air pollution affects light extinction, a measure of how much the components of the 

atmosphere scatter and absorb light. More light extinction means that the clarity of visual 

images and visual range is reduced, all else held constant. Light extinction is the optical 

characteristic of the atmosphere that occurs when light is either scattered or absorbed, which 

converts the light to heat. Particulate matter and gases can both scatter and absorb light. Fine 

particles with significant light-extinction efficiencies include sulfates, nitrates, organic carbon, 

elemental carbon, and soil (Sisler, 1996). The extent to which any amount of light extinction 

affects a person’s ability to view a scene depends on both scene and light characteristics. For 

example, the appearance of a nearby object (e.g., a building) is generally less sensitive to a 

change in light extinction than the appearance of a similar object at a greater distance. See 

Figure 6-1 for an illustration of the important factors affecting visibility.

According to the PM ISA, there is strong and consistent evidence that PM is the 

overwhelming source of visibility impairment in both urban and remote areas (U.S. EPA, 

2009b). After reviewing all of the evidence, the PM ISA concluded that the evidence was 

sufficient to conclude that a causal relationship exists between PM and visibility impairment.

 1 The visibility benefits results shown in this section only reflect the emission reductions associated with attaining 

the alternative PM2.5 primary standards. Visibility benefits results associated with attaining alternative

secondary PM NAAQS levels are provided in Chapter 13 of this RIA. 2 We use the term VAQ to refer to the visibility effects caused solely by air quality conditions, excluding fog.
 

6-7 

Figure 6-1. Important Factors Involved in Seeing a Scenic Vista (Malm, 1999)

Visibility is commonly measured as either light extinction (βext), which is defined as the 

loss of light per unit of distance in terms of inverse megameters (Mm-1), or using the deciview 

(dv) metric, which is a logarithmic function of extinction (Pitchford and Malm, 1994). Deciviews, 

a unitless measure of visibility, are standardized for a reference distance in such a way that one 

deciview corresponds to a change of about 10% in available light.3 Pitchford and Malm (1994) 

characterize a change of one deciview as “a small but perceptible scenic change under many 

circumstances.”4 Extinction and deciviews are both physical measures of the amount of 

visibility impairment (e.g., the amount of “haze”), with both extinction and deciview increasing 

as the amount of haze increases. Using the relationships derived by Pitchford and Malm (1994),

 

3 Note that deciviews are inversely related to visual range, such that a decrease in deciviews implies an increase in 

visual range (i.e., improved visibility). Conversely, an increase in deciviews implies a decrease in visual range 

(i.e., decreased visibility). Deciview, in effect, is a measure of the lack of visibility. 4 An instantaneous change of less than 1 deciview (i.e., less than 10% in the light extinction budget) represents a 

measurable improvement in visibility but may not be perceptible to the eye. The visibility benefits analysis 

described in this chapter reflects annual average changes in visibility, which are likely made up of periods with 

changes less than one deciview and periods with changes exceeding one deciview. Annual averages appear to 

more closely correspond to the economic literature relied upon for valuation of visibility changes in this 

analysis. The secondary PM NAAQS uses a different averaging time than the benefits analysis (see Chapter 13). 
6-8

Deciviews = 10 ∗ ln �

391

VR � = 10 ∗ ln �

βext

10 �

where VR denotes visual range (in kilometers) and βext denotes light extinction (in Mm-1).5

Annual average visibility conditions (reflecting light extinction due to both 

anthropogenic and non-anthropogenic sources) vary regionally across the U.S. and by season 

(U.S. EPA, 2009b). Particulate sulfate is the dominant source of regional haze in the eastern U.S. 

(>50% of the particulate light extinction) and an important contributor to haze elsewhere in the 

country (>20% of particulate light extinction) (U.S. EPA, 2009b). Particulate nitrate is an 

important contributor to light extinction in California and the upper Midwestern U.S., 

particularly during winter (U.S. EPA, 2009b). Smoke plumes from large wildfires dominate many 

of the worst haze periods in the western U.S., while Asian dust only caused a few of the worst 

haze episodes, primarily in the more northerly regions of the west (U.S. EPA, 2009b). Higher 

visibility impairment levels in the East are due to generally higher concentrations of fine 

particles, particularly sulfates, and higher average relative humidity levels (U.S. EPA, 2009b). 

Humidity increases visibility impairment because some particles such as ammonium sulfate and 

ammonium nitrate absorb water and form droplets that become larger when relative humidity 

increases, thus resulting in increased light scattering (U.S. EPA, 2009b).

Reductions in air pollution from implementation of various programs associated with 

the Clean Air Act Amendments of 1990 (CAAA) provisions have resulted in substantial 

improvements in visibility, and will continue to do so in the future. Because trends in haze are 

closely associated with trends in particulate sulfate and nitrate due to the simple relationship 

between their concentration and light extinction, visibility trends have improved as emissions 

of SO2 and NOx have decreased over time due to air pollution regulations such as the Acid Rain 

Program (U.S. EPA, 2009b). For example, Figure 6-2 shows that visual range increased nearly 

50% in the eastern U.S. since 1992.6 Recent EPA regulations such as the Cross-State Air 

Pollution Rule (U.S. EPA, 2011c) and the Mercury and Air Toxics Standard (U.S. EPA, 2011d) are 

anticipated to reduce SO2 emissions down to 2 million tons nationally, which would lead to 

substantial further improvement in visibility levels in the Eastern U.S. Calculated from light 

 5

It has been noted that, for a given deciview value, there can be many different visual ranges, depending on the 

other factors that affect visual range—such as light angle and altitude. See Appendix 6a for more detail. 6 In Figure 6-2, the “best days” are defined as the best 20% of days, the “mid-range days” are defined as the middle 

20%, and the “worst days” are defined as the worst 20% of days (IMPROVE, 2010).
6-9

Figure 6-2. Visibility in Selected National Parks and Wilderness Areas in the U.S., 1992–

2008a,b

(Source: U.S. EPA (2008) updated, IMPROVE (2010))

extinction efficiencies from Trijonis et al. (1987, 1988), annual average visual range under 

natural conditions in the East is estimated to be 150 km ± 45 km (i.e., 65 to 120 miles) and 230 

km ± 35 km (i.e., 120 to 165 miles) in the West (Irving, 1991). Figure 6-2 reflects the average

trends in visual ranges at select monitors in the eastern and western areas of the U.S. since 

1992 using data from the IMPROVE monitoring network (U.S. EPA (2008) updated; IMPROVE 

(2010)). As an illustration of the improvements in visibility attributable to the CAAA, Figure 6-3 

depicts the modeled improvements in visibility associated with all the CAAA provisions in 2020 

compared to a counterfactual scenario without the CAAA (U.S. EPA, 2011b). While visibility 

trends have improved in most National Parks, the recent data show that these areas continue 

to suffer from visibility impairment beyond natural background levels (U.S. EPA, 2009b).

For the final rulemaking, we would generate light extinction estimates using the CMAQ 

model in conjunction with the IMPROVE (Interagency Monitoring of Protected Visual 

Environments) algorithm that estimates light extinction as a function of PM concentrations and 

relative humidity levels (U.S. EPA, 2009b).7 The procedure for calculating light extinction

 7 According to the PM ISA, the algorithm performs reasonably well despite its simplicity (U.S. EPA, 2009b).
6-10

Figure 6-3. Estimated Improvement in Annual Average Visibility Levels Associated with the 

CAAA Provisions in 2020

Source: U.S. EPA, 2011b8

 8 It is important to note that visibility levels shown in these maps were modeled differently than the modeling 

conducted for this analysis, including coarser grid resolution (i.e., 36 km instead of 12 km). In addition, these 

maps present annual average visibility levels, which are different than the short-term averages being 

considered for the secondary standard.
6-11

associated with alternative standard level combinations is described in detail in Chapter 3 of 

this RIA. In addition, Appendix 6a describes how the spatial resolution of the light extinction 

estimates was then adjusted for the benefits analysis.

It is important to note that the light extinction estimates used in this benefits analysis 

represent annual averages, which is different from the averaging times currently being 

considered for the secondary PM NAAQS. While the annual averages are influenced by days 

with extremely impaired visibility, the light extinction data is not sufficient to provide higher 

temporal resolution than quarterly averages. While we suspect that the most impaired days 

would have disproportionately improved visibility from the emission reductions associated with 

attaining the alternative standard level combinations, we are not able to quantify those 

impacts. These data gaps result in an underestimate of visibility benefits associated with 

extreme days. We recognize that recent advice from EPA’s Science Advisory Board recommends 

estimating visibility benefits considering daytime visibility on days with severe impairment (U.S. 

EPA-SAB, 2010), but the available data and valuation studies do not allow such fine temporal 

resolution.

While we have made substantial improvements in estimating light extinction nationally 

in this analysis, we are still developing a method to estimate coarse particle concentrations for 

the entire continental U.S. for estimating light extinction. As an interim solution, we provide 

sensitivity analyses to show the potential impact of omitting coarse particles from the 

recreational and residential visibility benefits analysis. For this sensitivity analysis, we selected 

the levels of coarse particles to represent the full range of possible annual concentrations from 

a recent report on the IMPROVE monitoring network (Debell et al., 2006). We estimate the 

sensitivity of impacts on recreational and residential visibility benefits using four levels of 

coarse particles: no coarse particles, 5 μg/m3 nationwide, 15 μg/m3 in the Southwest with 

5 μg/m3 in the rest of the country, and 15 μg/m3 in the Southwest with 8 μg/m3 in the rest of 

the country.9

In Table 6-3, we also provide a qualitative assessment of how key assumptions in the 

estimation of light extinction affect the visibility benefits.

 9 We define “Southwest” for this sensitivity analysis to be the states of California, Nevada, Utah, Arizona, New 

Mexico, Colorado, and Texas.
6-12

Table 6-3. Key Assumptions in the Light Extinction Estimates Affecting the Visibility Benefits 

Analysisa

Key Assumption Direction of Bias Magnitude of Effect

The light extinction estimates are annual averages to 

correspond with the valuation studies. People may value large 

changes to the haziest days differently than small changes to 

many days. We assume that annual average light extinction is 

the most appropriate temporal scale for estimating visibility 

benefits.

Potential 

Underestimate Medium

Coarse particles are a component of light extinction, but we 

were unable to include coarse particles in the light extinction 

estimates. We provide sensitivity analyses with up to 15 μg/m3

in the Southwest and 8 μg/m3 in the rest of the country.

Potential 

Overestimate Very Low

a A description of the classifications for magnitude of effects can be found in Appendix 5C of this RIA.

6.4.2 Visibility Valuation Overview

In the Clean Air Act Amendments of 1977, the U.S. Government recognized visibility’s 

value to society by establishing a national goal to protect national parks and wilderness areas 

from visibility impairment caused by manmade pollution.10 Air pollution impairs visibility in 

both residential and recreational settings, and an individual’s willingness to pay (WTP) to 

improve visibility differs in these two settings. Benefits of residential visibility relate to the 

impact of visibility changes on an individual’s daily life (e.g., at home, at work, and while 

engaged in routine recreational activities). Benefits of recreational visibility relate to the impact 

of visibility changes manifested at parks and wilderness areas that are expected to be 

experienced by recreational visitors.

Both recreational and residential visibility benefits consist of use values and nonuse 

values. Use values include the aesthetic benefits of better visibility, improved road and air 

safety, and enhanced recreation in activities like hunting and birdwatching. Nonuse values are 

based on a belief that the environment ought to exist free of human-induced haze. This 

includes the value of better visibility for use by others now and in the future (bequest value). 

Nonuse values may be more important for recreational areas, particularly national parks and 

monuments.

The relationship between a household’s WTP and changes in visibility can be derived 

from a number of contingent valuation (CV) studies published in the peer-reviewed economics 

literature. The studies used to estimate the residential and recreational visibility benefits 

 10 See Section 169(a) of the Clean Air Act.
6-13

associated with alternative standard level combinations are described in the following sections. 

In addition to CV studies, hedonic valuation studies (Beron et al., 2001, 2004) also demonstrate 

that visibility has value, but we are unable to apply these valuation estimates in the context of 

estimating the visibility benefits associated with national regulations that reduce air pollution 

(Leggett and Neumann, 2004).

In this approach, we assume that individuals value visibility for aesthetic reasons rather 

than viewing visibility as a proxy for other impacts associated with air pollution, such as health 

or ecological improvements. Some studies in the literature indicate that individuals may have 

difficulty distinguishing visibility from other aspects of air pollution (e.g., McClelland et al., 

1993; Chestnut and Rowe, 1990c; Carson, Mitchell, and Rudd, 1990). Because visual air quality 

is inherently multi-attribute, it is a challenge for all visibility valuation studies to isolate the 

value of visibility from the collection of intertwined benefits. Each study used in this analysis 

attempts to isolate visibility from other effect categories, but the different studies take 

different approaches (U.S. EPA, 2009b).11 Because we believe that residual potential for doublecounting visibility and health effects is relatively minimal, we do not further adjust the benefits 

to account for potentially embedded health effects beyond what the studies have already done.

Similarly, it is important to try to distinguish residential visibility from recreational 

visibility benefits, specifically whether these can these be treated as distinct and additive 

benefit categories based on the available literature. In this analysis, we assume that residential 

and recreational visibility benefits are distinct and separable. It is conceivable that respondents 

to the recreational visibility survey may have partially included values for their own residential 

visibility when evaluating changes at national parks and wilderness areas located in their region 

of the country. However, we believe that the potential for double-counting recreational and 

residential visibility is minimal for several reasons. First, we only include a subset of areas in the 

primary estimates of recreational and residential visibility benefits, which overlap in only a few 

places.12 Second, a number of the overlapping counties are wilderness areas, which contribute 

little to the overall monetized benefits due to low visitation rates, rather than highly visited 

national parks. For example, Los Angeles County is home to the San Gabriel Wilderness Area, 

which has 10 thousand annual visitors (NPS, 2008). If we exclude the residential visibility 

benefits that accrue to 10 million residents in Los Angeles County and only include the very 

small recreational visibility benefits for the wilderness area, we would be substantially biasing 

 11 See Leggett and Neumann (2004) for a more detailed discussion of this issue. 12 As described in detail in Sections 6.3.3 and 6.3.4, we only include a subset of visibility benefits in the primary 

benefits estimates, while providing the rest of the visibility benefits in sensitivity analyses.
6-14

the overall estimates downward. For these reasons, we believe that the potential for doublecounting is minimal.

In the next sections, we describe the methodology and limitations of the recreational 

and residential visibility analysis. Consistent with the health benefits analysis, the monetized 

visibility benefits would be adjusted for inflation and income growth. These benefits would be 

specific to the analysis year, and as population and income increase over time, these benefits 

can be expected to increase each year for the same incremental change in light extinction.

6.4.3 Recreational Visibility

6.4.3.1 Methodology

The methodology for estimating recreational visibility benefits in this RIA follows a wellestablished approach that has been used in numerous EPA analyses (U.S. EPA, 2006; U.S. EPA, 

2005; U.S. EPA, 2010; U.S. EPA, 1999; U.S. EPA, 2011b). For the purposes of this analysis, 

recreational visibility benefits apply to Class I areas, such as National Parks and Wilderness 

Areas.13 Although other recreational settings such as National Forests, state parks, or even 

hiking trails or roadside areas have important scenic vistas, a lack of suitable economic 

valuation literature to identify these other areas and/or a lack of visitation data prevents us 

from generating estimates for those recreational vista areas.

Under the 1999 Regional Haze Rule (64 FR 35714), states are required to set goals 

develop long-term strategies to improve visibility in Class I areas, with the goal of achieving 

natural background visibility levels by 2064. In conjunction with the U.S. National Park Service 

(NPS), the U.S. Forest Service (USFS), other Federal land managers, and State organizations in 

the U.S., the U.S. EPA has supported visibility monitoring in national parks and wilderness areas 

since 1988. The monitoring network known as IMPROVE includes 156 sites that represent the 

Class I areas across the country (U.S. EPA, 2009b).14 The IMPROVE monitoring network 

measures fine particles, coarse particles, and key PM2.5 constituents that affect visibility, such 

as sulfate, nitrate, organic and elemental carbon, soil dust, and several other elements. 

Figure 6-4 identifies where each of these parks are located in the U.S.

 13 Hereafter referred to as Class I areas, which are defined as areas of the country such as national parks, national 

wilderness areas, and national monuments that have been set aside under Section 169(a) of the Clean Air Act 

to receive the most stringent degree of air quality protection. Mandatory Class I federal lands fall under the 

jurisdiction of three federal agencies, the National Park Service, the Fish and Wildlife Service, and the Forest 

Service. EPA has designated 156 areas as mandatory Class I federal areas for visibility protection, including 

national parks that exceed 6,000 acres and wilderness areas that exceed 5,000 acres (40 CFR §81.400). 14 The formula used to estimate light extinction from concentrations of PM constituents and relative humidity is 

referred to as the IMPROVE algorithm.
6-15

Figure 6-4. Mandatory Class I Areas in the U.S.

For recreational visibility, EPA has determined that only one existing study provides 

adequate monetary estimates of the value of changes in recreational visibility: a contingent 

valuation (CV) survey conducted by Chestnut and Rowe in 1988 (1990a; 1990b). Although there 

are several other studies in the literature on recreational visibility valuation, they are older and 

use less robust methods. In EPA’s judgment, the Chestnut and Rowe study contains many of the 

elements of a valid CV study and is sufficiently reliable to serve as the basis for monetary 

estimates of the benefits of visibility changes in recreational areas.15 This study serves as an 

essential input to our estimates of the benefits from improving recreational visibility.

In this analysis, we assume that the household WTP is higher if the Class I recreational 

area is located close to the person’s home (i.e., in the same region of the country). People 

appear to be willing to pay more for visibility improvements at parks and wilderness areas that 

 15 In 1999, EPA’s SAB stated, “many members of the Council believe that the Chestnut and Rowe study is the best 

available” study for recreational visibility valuation” (U.S. EPA-SAB, 1999). In July 2010, the SAB stated that the 

studies were dated, but EPA “used what the Council understands to be the only relevant studies.” (U.S. EPASAB, 2010)
6-16

are in the same region as their household than at those that are not in the same region as their 

household (Chestnut and Rowe, 1990a, 1990b). This is plausible, because people are more likely 

to visit, be familiar with, and care about parks and wilderness areas in their own part of the 

country. However, studies have also found many people who had never visited and never 

planned to visit the parks still had positive values for visibility improvements in those locations 

(Chestnut and Rowe, 1990b).

The Chestnut and Rowe survey measured the demand for visibility in Class I areas 

managed by the NPS in three broad regions of the country: California, the Colorado Plateau 

(Southwest), and the Southeast.16 Respondents in five states were asked about their WTP to 

protect national parks or NPS-managed wilderness areas within a particular region. The survey 

used photographs reflecting different visibility levels in the specified recreational areas. The 

authors used the survey data to estimate household WTP values for improved visibility in each 

region.

The separate regions were developed to capture differences in household WTP values 

based on proximity to recreational areas. Chestnut (1997) also concluded that, for a given 

region, a substantial proportion of the WTP is attributable to one specific park within the 

region. This so called “indicator park” is the most well-known and frequently visited park within 

a particular region. The indicator parks for the three studied park regions are Yosemite National 

Park for the California region, the Grand Canyon National Park for the Southwest region, and 

Shenandoah National Park for the Southeast region. In accordance with the methodology in 

Chestnut (1997), this analysis calculates the benefits from households for a particular region for 

a given change in visibility at a particular Class I area. In theory, summing benefits from 

households in all regions would yield the total monetary benefits associated with a given 

visibility improvement at a particular park, which could then be summed with other parks and 

regions to estimate national benefits. Because recreational visibility benefits may reflect the 

value an individual places on visibility improvements regardless of whether the person plans to 

visit the park, all households in the U.S. are assumed to derive some benefit from 

improvements to Class I areas.

To value recreational visibility improvements associated with its rulemakings, EPA 

developed a valuation WTP equation function based on the baseline of visibility, the magnitude 

 16 The Colorado Plateau (Southwest) region is defined as the states of Colorado, New Mexico, Arizona, and Utah.

The Southeast region is defined as the states of West Virginia, Virginia, North Carolina, South Carolina, Georgia, 

Florida, Alabama, Mississippi, Louisiana, Tennessee, and Kentucky. The California region includes the state of 

California and one wilderness area in Nevada.
6-17

of the visibility improvement, and household income. This function requires light extinction 

estimates measured as visual range. The behavioral parameters of this equation were taken 

from analysis of the Chestnut and Rowe survey (1990a, 1990b). These parameters were used to 

calibrate WTP for the visibility changes resulting from this rule.17 As an example, household 

WTP for a visibility improvement at a park in their region takes the following form:

WTP(∆Qik) = m − [mρ + γik ∗ �Q0ik

ρ − Q1ikρ �]

1

ρ

where:

i indexes region,

k indexes park,

m = household income,

ρ = shape parameter (0.1),

γ = parameter corresponding to the visibility at in-region parks,

Q0 = starting visibility, and

Q1 = visibility after change.

As discussed in more detail in Appendix 6a of this RIA, this approach to valuing 

recreational visibility changes is an application of the Constant Elasticity of Substitution (CES) 

utility function approach and is based on the preference calibration method developed by 

Smith, Van Houtven, and Pattanayak (2002).18 Available evidence indicates that households are 

willing to pay more for a given visibility improvement as their income increases (Chestnut, 

1997). Using the income elasticity calculated by Chestnut (1997), the visibility benefits assume a 

1% increase in income is associated with a 0.9% increase in WTP for a given change in visibility. 

WTP responses reported in Chestnut and Rowe (1990a, 1990b) were also region-specific, rather 

than park-specific. As visibility improvements are not constant across all parks in a region, we 

must infer park-specific visibility parameters in order to calculate WTP for projected visibility 

changes. As the quantity and quality of parks differs between regions, we apportion the 

regional WTP parameters based on relative visitation rates at the different parks, because this 

statistic likely captures both park quality (more people visit parks with more desirable 

attributes, so collective WTP is likely higher) and quantity (more people visit parks in a region if 

 17 The parameters for each region are available in Appendix 6a of this RIA. 18 The Constant Elasticity of Substitution utility function has been chosen for use in this analysis due to its flexibility 

when illustrating the degree of substitutability present in various economic relationships (in this case, the 

tradeoff between income and improvements in visibility).
6-18

the parks are more numerous, so collective WTP is likely higher).19 We also adjust the benefits 

for inflation and growth in real income.

Recreational visibility benefits are calculated as the sum of the household WTPs for 

changes in light extinction. We assume that each household is valuing the first or only visibility 

change that occurs in a particular area. The benefits at particular areas can be calculated by 

assuming that the subset of visibility changes of interest is the first or the only set of changes 

being valued by households. Estimating benefit components in this way will yield slightly 

upwardly biased estimates of benefits, because disposable income is not reduced by the WTPs 

for any prior visibility improvements. The upward bias should be extremely small, however, 

because all of the WTPs for visibility changes are very small relative to income.

The primary estimate for recreational visibility only includes benefits for 86 Class I areas 

in the original study regions (i.e., California, the Southwest, and the Southeast).20 These 

benefits reflect the value to households living in the same region as the Class I area as well as 

values for all households in the United States living outside the state containing the Class I area.

The Chestnut and Rowe study did not measure values for visibility improvement in Class 

I areas in the Northwest, Northern Rockies, and Rest of U.S. regions.21 Their study covered 86 of 

the 156 Class I areas in the United States. We can infer the value of visibility changes in the 70 

additional Class I areas by transferring values of visibility changes at Class I areas in the study 

regions.22 In order to obtain estimates of WTP for visibility changes for parks in these additional 

regions, we have to transfer the WTP values from the studied regions. This benefits transfer 

approach introduces additional uncertainty into the estimates. However, we have taken steps 

to adjust the WTP values to account for the possibility that a visibility improvement in parks 

within one region may not necessarily represent the same visibility improvement at parks 

within a different region in terms of environmental improvement. This may be due to 

 19 We use 2008 park visitation data from the National Park Service Statistical Abstracts (NPS, 2008), as this is the 

most current data available. Where the data for a particular park was not representative of normal visitation 

rates at that park (for example due to fire damage that occurred during that year), we substitute data from the 

prior year. We use 1997 visitation data for those wilderness areas not included in the National Park Service 

Statistical Abstracts, as more current data is not readily available. As visitation rates for Wilderness Areas are 

small compared to visitation rates in National Parks, the inaccuracies generated by using 1997 data are likely to 

also be small. 20 The 86 Class I areas in the three studied park regions represented 68% of the total visitor days to Class I areas in 

2008 (NPS, 2008). 21 The Northwest region is defined as the states of Washington and Oregon. The Northern Rockies region include 

the states of Idaho, Montana, Wyoming, North Dakota, and South Dakota. The Rest of the U.S. region includes 

all other states not included in the other 5 regions. 22 The 70 additional Class I areas represented 32% of the total visitor days to Class I areas in 2008 (NPS, 2008).
6-19

differences in the scenic vistas at different parks, uniqueness of the parks, or other factors, such 

as public familiarity with the park resource. To account for this potential difference, we 

adjusted the transferred WTP being transferred by the ratio of visitor days in the two regions.23

A complete description of the benefits transfer method used to infer values for visibility 

changes in Class I areas outside the study regions is provided in Appendix 6a of this RIA.

Table 6-4 indicates which studied park regions we used to estimate the value in the nonstudied park regions. Figure 6-5 shows how the visitation rates vary across Class I areas and 

regions and indicates whether each Class 1 area is located within one of the studied regions.

6.4.3.2 Recreational Visibility Limitations, Caveats, and Uncertainties

This analysis relies upon several data sources as inputs, including emission inventories, 

air quality data from models (with their associated parameters and inputs), relative humidity 

measurements, park information, economic data and assumptions for monetizing benefits. 

Each of these inputs may contain uncertainty that would affect the recreational visibility 

benefits estimates. Though we are unable to quantify the cumulative effect of all of these 

uncertainties in this analysis, we do provide information on uncertainty based on the available 

data, including model evaluation24 and sensitivity analyses to characterize major omissions (i.e., 

benefits from parks in non-studied park regions and inclusion of coarse particles). Although we 

strive to incorporate as many quantitative assessments of uncertainty as possible, we are 

severely limited by the available data, and there are several aspects that we are only able to 

address qualitatively. A summary of the key assumptions including direction and magnitude of 

bias is provided in Table 6-5.

One major source of uncertainty for the recreational visibility benefits estimate is the 

benefits transfer process. Choices regarding the functional form and key parameters of the 

estimating equation for WTP for the affected population could have significant effects on the 

magnitude of the estimates. Assumptions about how individuals respond to changes in visibility 

that are either very small or outside the range covered in the Chestnut and Rowe study could 

also affect the estimates.

 23 For example, if total park visitation in a transfer region was less than visitation in a study region, transferred WTP 

would be adjusted downward by the ratio of the two. 24 See Chapter 4 for more information on model evaluation.
6-20

Table 6-4. WTP for Visibility Improvements in Class I Areas in Non-Studied Park Regions

Park Region Source of WTP Estimate

1. Northwest benefits transfer from California 

2. Northern Rockies benefits transfer from Colorado Plateau

3. Rest of U.S. benefits transfer from Southeast

Figure 6-5. Visitation Rates and Park Regions for Class I Areas*

* The colors in this map correspond to the park regions used in the valuation study and the extrapolation to parks 

in other regions. Red = California, light red = Northwest (extrapolated from California), blue = Colorado Plateau, 

light blue = Northern Rockies (extrapolated from Colorado Plateau), green = Southeast, light green = Rest of U.S. 

(extrapolated from Southeast).

ys
6-21

Table 6-5. Summary of Key Assumptions in the Recreational Visibility Benefitsa

Key Assumption Direction of Bias

Potential Magnitude 

of Effect

Chestnut and Rowe study covers parks in three regions: California, 

Southwest, and Southeast. Benefits to other regions in the U.S. 

are not included in the primary benefits estimate. 

Underestimate Medium

Benefits to other recreational settings, such as National Forests 

and state parks, are not included in this analysis. Underestimate Medium-Low

Chestnut and Rowe study conducted on populations in five states. 

These results are applied to the entire U.S. population. Unclear Unclear

Individuals have a greater WTP for visibility changes in parks 

within their region. Unclear Unclear

WTP values reflect only visibility improvements and not overall air 

quality improvements. 

Potential 

Overestimate Unclear

We assume that there are 2.68 people per household. Because 

this estimate has been decreasing over time, this may 

underestimate the number of households. 

Potential 

Underestimate Medium-Low

a A description of the classifications for magnitude of effects can be found in Appendix 5C of this RIA.

Since the valuation of recreational visibility benefits relies upon one study (Chestnut and 

Rowe, 1990a; 1990b), all of the uncertainties within that study also pertain to this analysis. In 

general, the survey design and implementation reflect the period in which the Chestnut and 

Rowe study was conducted. Since that time, many improvements to the design of stated 

preference surveys have been developed (e.g., Arrow, 1993), but we are currently unaware of 

newer studies that we could incorporate into our visibility benefits methodology. Although 

Chestnut and Rowe still offers the best available WTP estimates, the study has a number of 

limitations, including:

 The vintage of the survey (late 1980s) invites questions whether the values would 

still be valid for current populations, or more importantly for this analysis, future 

populations in 2020.

 The survey focused on visibility improvements in and around specific national parks 

and wilderness areas. Given that national parks and wilderness areas exhibit unique 

characteristics, it is not clear whether the WTP estimate obtained from this survey 

can be transferred to other national parks and wilderness areas, even other parks 

within the studied park regions, without introducing additional uncertainty.
6-22

 The survey focused only on populations in five states, so the application of the 

estimated values to populations outside those states requires that preferences of 

populations in the five surveyed states be similar to those of non-surveyed states.

 There is an inherent difficulty in separating values expressed for visibility 

improvements from an overall value for improved air quality. The survey attempted 

to control for this by informing respondents that “other households are being asked 

about visibility, human health, and vegetation protections in urban areas and at 

national parks in other regions.” However, most of the respondents did not feel that 

they were able to segregate recreational visibility at national parks entirely from 

residential visibility and health effects.

 It is not clear exactly what visibility improvements the respondents to the survey 

were valuing. The WTP question asked about changes in average visibility, but the 

survey respondents were shown photographs of only daytime, summer conditions, 

when visibility is generally at its worst. It is possible that the respondents believed 

those visibility conditions held year-round, in which case they would have been 

valuing much larger overall improvements in visibility than what otherwise would be 

the case. For the purpose of the benefits analysis for this rule, EPA assumed that 

respondents provided values for changes in annual average visibility. Because most 

policies would result in a shift in the distribution of visibility (usually affecting the 

worst days more than the best days), the annual average may not be the most 

relevant metric for policy analysis.

 The survey did not include reminders of possible substitutes (e.g., visibility at other 

parks) or budget constraints. These reminders are considered to be best practice for 

stated preference surveys.

6.4.4 Residential Visibility

6.4.4.1 Methodology

Residential visibility benefits are those that occur from visibility changes in urban, 

suburban, and rural areas where people live. These benefits are important because some 

people living in certain urban areas may place a high value on unique scenic resources in or 

near these areas that are outside of Class I areas. For example, the State of Colorado 

established a local visibility standard for the Denver metropolitan area in 1990 (Ely et al., 1991). 

For the purposes of this analysis, residential visibility improvements are defined as those that 

occur specifically in Metropolitan Statistical Areas (MSAs).

In the Urban-focused Visibility Assessment (U.S. EPA, 2010b) and the Policy Assessment 

for the Review of the PM NAAQS (U.S. EPA, 2011a), several preference studies provide the 
6-23

foundation for the secondary PM NAAQS.25 The three completed survey studies (all in the west) 

included Denver, Colorado (Ely et al., 1991), one in the lower Fraser River valley near 

Vancouver, British Columbia (BC), Canada (Pryor, 1996), and one in Phoenix, Arizona (BBC 

Research & Consulting, 2003). A pilot focus group study was conducted in Washington, DC on 

behalf of EPA to inform the 2006 PM NAAQS review (Abt Associates Inc., 2001). While these 

studies indicate that visual air quality associated with ambient levels of air pollution in urban 

areas have been deemed unacceptable, they do not provide sufficient information on which to 

develop monetized benefits estimates. Specifically, the public perception studies do not 

provide preferences expressed in dollar values, even though they do provide additional 

evidence that the benefits associated with improving residential visibility are not zero.

A wide range of published, peer-reviewed literature supports a non-zero value for 

residential visibility (Brookshire et al., 1982; Rae, 1983; Tolley et al., 1984; Chestnut and Rowe, 

1990c; McClelland et al., 1993; Loehman et al., 1994). Furthermore, Chestnut and Rowe (1990c) 

conclude that residential visibility benefits are likely to be at least as high as recreational 

visibility benefits because of the quantity of time most people spend in and near their homes 

and the substantial number of people affected. In previous assessments, EPA used a study on 

residential visibility valuation conducted in 1990 (McClelland et al., 1993). Consistent with 

advice from EPA’s Science Advisory Board (SAB), EPA designated the McClelland et al. study as 

significantly less reliable for regulatory benefit-cost analysis, although it does provide useful 

estimates on the order of magnitude of residential visibility benefits (U.S. EPA-SAB, 1999).26 In 

order to estimate residential visibility benefits in this analysis, we have replaced the previous 

methodology with a new benefits transfer approach and incorporated additional valuation 

studies. This new approach was developed for The Benefits and Costs of the Clean Air Act 1990 

to 2020: EPA Report to Congress (U.S. EPA, 2011)27 and reviewed by the SAB (U. S. EPA-SAB, 

2004, 2010).

 25 For more detail about these preference studies, including information about study designs and sampling 

protocols, please see Section 2 of the Particulate Matter Urban-Focused Visibility Assessment (U.S. EPA, 2010b). 26 EPA’s Advisory Council on Clean Air Compliance Analysis noted that the McClelland et al. (1993) study may not 

incorporate two potentially important adjustments. First, their study does not account for the “warm glow”

effect, in which respondents may provide higher willingness to pay estimates simply because they favor “good 

causes” such as environmental improvement. Second, while the study accounts for non-response bias, it may 

not employ the best available methods. As a result of these concerns, the Council recommended that 

residential visibility be omitted from the overall primary benefits estimate. (U.S. EPA-SAB, 1999) 27 This report is also known as the Second Prospective 812 analysis.
6-24

To value residential visibility improvements, the new approach draws upon information 

from the Brookshire et al. (1979), Loehman et al. (1985) and Tolley et al. (1984) studies.28 Each 

of the studies provides estimates of household WTP to improve visibility conditions. While 

uncertainty exists regarding the precision of these older, stated-preference residential 

valuation studies, we believe their results support the argument that individuals have a nonzero value for residential visibility improvements. These studies provide primary visibility values 

for Atlanta, Boston, Chicago, Denver, Los Angeles, Mobile, San Francisco, and Washington 

D.C.29

In accordance with Chestnut and Rowe (1990c), we utilize the WTP estimates and the 

associated change in visual range from each study to estimate the β parameter for the eight 

study areas. The β parameter represents the WTP for a specific improvement in visibility in a 

specific location. Where studies provide multiple estimates for visual range improvements, we 

estimate β by regressing the natural log of the ratio of visual range following and prior to 

improvement against WTP. To express these value estimates in comparable terms across study 

locations, we express household WTP for a change in visual range in a specific MSA using the 

following function:

WTP (∆VR)= β* ln ( VR1

VR0

)

where:

VR0 = mean annual visual range in miles before the improvement,

VR1 = mean annual visual range in miles after the improvement, and

β = parameter.

Total residential visibility benefits within a particular MSA are driven by visibility 

improvements, population density, and the WTP value applied. Only those people living within 

 28 Loehman et al. (1985) and Brookshire et al. (1979) were subsequently published in peer-reviewed journals (see 

Loehman et al. (1994) and Brookshire et al. (1982). The specific details need to compute visibility benefits using 

Tolley et al. (1984) were not subsequently published, but the overall work including study and survey design 

was subject to peer review during study development. (see Leggett et al, 2004 and Patterson et al., 2005) In 

addition, Tolley et al. subsequently published a book based on this research, which notes in the preface that 

the methods were critiqued throughout by various external economists (Tolley et al., 1988). 29 Recognizing potential fundamental issues associated with data collected in Cincinnati and Miami (e.g., see 

Chestnut et al. (1986) and Chestnut and Rowe (1990c), we do not include values for these cities in our analysis. 

The 8 MSAs where the valuation studies were conducted represent 15% of the total US population in 2020 (U.S. 

Census).
6-25

in an MSA are assumed to receive benefits from improved residential visibility. In other words, 

unlike recreational visibility, we do not assume a non-use value by people who live outside the 

MSA for residential visibility. Table 6-6 provides a summary of these valuation estimates for 

each study location, as well as an illustrative implied WTP value for a 10% improvement in 

visual range. As shown, the implied annual per-household WTP estimates for a hypothetical 

10% improvement ranges from $21 to $220, depending on the study area. It is not surprising 

that such a range of values exists, as these study areas all feature different landscapes and 

vistas, populations and prevailing visibility conditions.

Table 6-6. Summary of Residential Visibility Valuation Estimates

City Study β Estimate

Implied WTP for 10% 

Improvement in Visual 

Range (1990$, 1990 

income)

Implied WTP for 10% 

Improvement in Visual 

Range (2006$, 2020 

income)

Atlanta Tolley et al. (1984) 321 $31 $72

Boston Tolley et al. (1984) 398 $38 $89

Chicago Tolley et al. (1984) 310 $30 $69

Denver Tolley et al. (1984) 696 $66 $155

Los Angeles Brookshire et al. (1979) 94 $9 $21

Mobile Tolley et al. (1984) 313 $30 $70

San Francisco Loehman et al. (1985) 989 $94 $220

Washington, DC Tolley et al. (1984) 614 $59 $137

a The table assumes full attainment of the alternative standard level combinations. Because these benefits occur 

within the analysis year, the monetized benefits are the same for all discount rates. These benefits reflect the 

WTP for households who live in MSAs.

Similar to recreational visibility benefits, we then incorporate preference calibration 

using the method developed by Smith, Van Houtven, and Pattanayak (2002), which is discussed 

in more detail in Appendix 6a of this RIA. To express these “preference-calibrated” value 

estimates across study locations, we express household WTP for a change in visual range in a 

specific MSA using the following function:
6-26

WTP(∆VR) = m − [mρ + θ ∗ �VR0

ρ − VR1ρ

�]

1

ρ

where:

m = household income,

ρ = shape parameter (0.1),

θ = WTP parameter corresponding to the visibility at MSA,

VR0 = starting visibility, and

VR1 = visibility after change.

While the primary estimate for residential visibility includes benefits in only the eight 

MSAs included in the valuation studies, people living in other urban areas also have non-zero 

values for residential visibility. For this reason, the sensitivity analysis for residential visibility 

includes the benefits extrapolated to the 351 additional MSAs.30 Because there is considerable 

uncertainty about the validity of this benefit transfer approach, these extrapolated benefits are 

included in a sensitivity analysis only.

There are many factors that could influence WTP for residential visibility, and these 

factors vary across urban areas. For the purpose of this analysis, we utilize the benefit transfer 

approach developed for the Second Prospective 812 analysis, but we recognize that there are 

alternative methods that we could have used. We assigned a valuation study area to each MSA 

based on two factors: geographic proximity to one of the eight study cities and elevation. Any 

MSA with a county elevation above 1,500 meters was assigned the Denver valuation instead of 

the nearest study area.31 Because residents of Denver have a dramatic view of the Rocky 

Mountains that is rarely obstructed by trees, it is plausible that they might have a greater 

interest in protecting visibility than a city without nearby mountains. The geographic proximity 

factor is constrained in two areas. The San Francisco valuation study is only assigned to the six 

counties in the San Francisco Bay area MSAs because the study is unique among the three 

regarding the temporal description of visibility conditions, landscape/vistas, and prevailing 

weather conditions. In addition, the Los Angeles valuation was assigned to the Riverside MSA 

 30 The 351 additional MSAs plus the 8 study area MSAs represent 84% of the total US population in 2020 (U.S. 

Census). 31 Elevation data represent the county-level maximum, which were calculated using the ArcGIS Spatial Analyst tool 

“Zonal Statistics” using the geographic database HYDRO1K for North America (U.S. Geological Survey, 1997).

This dataset and associated documentation are available on the Internet at 

DEMhttp://eros.usgs.gov/#/Find_Data/Products_and_Data_Available/gtopo30/hydro/namerica.
6-27

despite exceeding the elevation threshold.32 Figure 6-6 indicates the study cities as well as the 

assignment of the other MSAs to the study cities.

6.4.4.2 Residential Visibility Limitations, Caveats, and Uncertainties

Similar to recreational visibility benefits, there are many data inputs into the residential 

visibility benefits that contribute to overall uncertainty. We provide sensitivity analyses to 

characterize major omissions (i.e., benefits in other MSAs and coarse particles). A summary of 

the key assumptions including direction and magnitude of bias is provided in Table 6-7.

Figure 6-6. Residential Visibility Study City Assignment

 32 Riverside MSA is assigned to the Los Angeles study area because a significant portion of Riverside County itself is 

located in the South Coast Air Quality Management District, which can be considered by to be part of the same 

regulated airshed as Los Angeles. The geographic assignment is preserved despite exceeding the elevation 

threshold because Riverside is adjacent to one of the study cities and this region has a particular set of locationspecific characteristics that set it apart from Denver. 
6-28

Table 6-7. Summary of Key Assumptions in the Residential Visibility Benefitsa

Key Assumption Direction of Bias

Magnitude of 

Effect

Residential and recreational visibility benefits are distinct and 

separable. 

Potential 

Overestimate Medium-Low

Estimates residential visibility benefits are limited to populations 

within the boundaries of MSAs. Areas outside of an MSA are not 

included in this analysis. 

Underestimate Low

WTP values reflect only visibility improvements and not overall air 

quality improvements. 

Potential 

Overestimate Medium-Low

WTP values from studies in Atlanta, Boston, Chicago, Denver, Los 

Angeles, Mobile, San Francisco, and Washington D.C. can be 

accurately transferred to MSAs across the U.S. based on proximity 

and elevation

Unclear Unclear

We assume that there are 2.68 people per household. Because 

this estimate has been decreasing over time, this may 

underestimate the number of households. 

Potential 

Underestimate Medium-Low

a A description of the classifications for magnitude of effects can be found in Appendix 5C of this RIA.

The valuation studies relied upon for the residential visibility benefits, although 

representing the best available estimates, have a number of limitations. These include the 

following:

 The survey design and implementation reflects the period in which the surveys were 

conducted. Since that time, many improvements to the stated preference methods 

have been developed.

 The vintage of the surveys (1970s and 1980s) invites questions whether the values 

are still valid for current populations, or more importantly for this analysis, future 

populations in 2020.

 The survey focused only on populations in eight cities, so the transfer of the WTP 

estimates values to populations outside those cities requires that their preferences 

be similar to those in non-surveyed cities, as well as the visibility attributes be 

similar across study and transfer MSAs.

 There is an inherent difficulty in separating values expressed for visibility 

improvements from an overall value for improved air quality. The studies attempted 

to control for this, but most of the respondents did not feel that they were able to 

segregate residential visibility entirely from recreational visibility and health effects.
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6.4.5 Discussion of Visibility Benefits

As described in the previous sections of this chapter, the estimation of visibility benefits 

is complex and suffers from unavoidable limitations. While we are confident that the underlying 

scientific literature supports a non-zero estimate for visibility benefits attributable to emission 

reductions, we are less confident in the magnitude of those benefits outside of previously 

studied locations. While acknowledging these limitations, it is important to emphasize that 

these valuation studies have withstood intense scrutiny (U.S. EPA-SAB, 2010). To minimize 

uncertainties related to extrapolation and double counting, we only include a subset of 

monetized visibility benefits in the primary benefits estimate to correspond with our higher 

level of confidence in recreational benefits within the study regions and residential benefits 

within the study cities. Although we are confident that visibility benefits extend beyond these 

studied areas, we are less confident about the magnitude of those benefits.

In the approach described here, we have revised several aspects of the visibility benefits 

analysis since previous RIAs, including light extinction estimation methods, visitation data for 

Class I areas (used in extrapolating benefits), valuation studies for residential visibility benefits, 

and the benefit transfer technique for residential benefits. Including residential visibility 

benefits in the primary benefits estimates reflects an evolution in our understanding of the 

nature and importance of the effect on public welfare from visibility impairment to a more 

multifaceted approach that includes non-Class I areas, such as urban areas. This evolution has 

occurred in conjunction with the expansion of available PM data and information from 

associated studies of public perception, valuation and personal comfort and well-being. While 

visibility preference studies (Abt Associates Inc., 2001, Ely et al., 1991, Pryor, 1996, BBC 

Research & Consulting, 2003) also provide support for a non-zero benefits estimate, these 

surveys did not include questions that would enable monetization of those preferences.

Despite these improvements, we are limited by the available peer-reviewed studies on 

visibility benefits, which have not undergone a similar expansion as the health literature. In 

fact, to our knowledge, no peer-reviewed studies have been published in the past 10 years on 

visibility valuation that we are able to incorporate into this analysis.33 When EPA’s Scientific 

Advisory Council reviewed the visibility benefits analysis for the Second Prospective 812 

analysis, they also lamented on the need for additional research to improve methods and 

estimates (U.S. EPA-SAB, 2010). Because of time and resource constraints, performing original 

 33 While several studies using hedonic valuation techniques to value air quality have been published in the last 10 

years (Kim et al., 2010; Bayer et al., 2009; Anselin and Lozano-Gracia, 2006, 2008; Chay and Greenstone, 2005), 

these studies do not provide any mechanism to distinguish visibility from health or ecosystem effects. 
6-30

research for regulatory analyses of specific policy actions is infeasible. Therefore, we actively 

encourage and solicit new research to address many of the limitations in our analysis. Most 

importantly, we are interested in recently published national-scale visibility valuation studies 

that incorporate current CV best practices, as the existing studies are limited to specific subset 

of geographic areas. Other important research questions that remain unresolved include 

identifying factors that affect valuation preferences in order to facilitate benefits transfer from 

the original studies to transfer sites across localities, disentangling health and ecosystem 

valuation from visibility valuation, usefulness of preference calibration, and potential role of 

hedonic valuation approaches. Many of these same research needs were identified by Cropper 

(2000), but they have yet to be addressed by the research community.

For these reasons, EPA requests public comment on the approach taken here to 

quantify the monetary value of changes in recreational and residential visibility. Specifically, we 

request comment on additional valuation studies, methods for benefit transfer, and methods 

for characterizing uncertainty.

6.5 Materials Damage Benefits

Building materials including metals, stones, cements, and paints undergo natural 

weathering processes from exposure to environmental elements (e.g., wind, moisture, 

temperature fluctuations, sunlight, etc.). Pollution can worsen and accelerate these effects. 

Deposition of PM is associated with both physical damage (materials damage effects) and 

impaired aesthetic qualities (soiling effects). Wet and dry deposition of PM can physically affect 

materials, adding to the effects of natural weathering processes, by potentially promoting or 

accelerating the corrosion of metals, by degrading paints and by deteriorating building 

materials such as stone, concrete and marble (U.S. EPA, 2009b). The effects of PM are 

exacerbated by the presence of acidic gases and can be additive or synergistic due to the 

complex mixture of pollutants in the air and surface characteristics of the material. Acidic 

deposition has been shown to have an effect on materials including zinc/galvanized steel and 

other metal, carbonate stone (as monuments and building facings), and surface coatings 

(paints) (Irving, 1991). The effects on historic buildings and outdoor works of art are of 

particular concern because of the uniqueness and irreplaceability of many of these objects.

The PM ISA concludes that evidence is sufficient to support a causal relationship 

between PM and effects on materials (U.S. EPA, 2009b). Considerable research has been 

conducted on the effects of air pollutants on metal surfaces due to the economic importance of 

these materials, especially steel, zinc, aluminum, and copper. Moisture is the single greatest 
6-31

factor promoting metal corrosion; however, deposited PM can have additive, antagonistic or 

synergistic effects. In general, SO2 is more corrosive than NOx although mixtures of NOx, SO2

and other particulate matter corrode some metals at a faster rate than either pollutant alone 

(U.S. EPA, 2008). Metal structures are usually coated by alkaline corrosion product layers and 

thus are subject to increased corrosion by acidic deposition. In addition, research has 

demonstrated that iron, copper, and aluminum-based products are subject to increased 

corrosion due to pollution (Irving, 1991). Information from both the PM ISA (U.S. EPA, 2009b) 

and NOx/SOx ISA (U.S. EPA, 2008) suggest that the extent of damage to metals due to ambient 

PM is variable and dependent upon the type of metal, prevailing environmental conditions, rate 

of natural weathering and presence or absence of other pollutants

In addition, the deposition of PM can cause soiling, which is the accumulation of dirt, 

dust, and ash on exposed surfaces such as metal, glass, stone and paint. Particles consisting 

primarily of carbonaceous compounds can cause soiling of commonly used building materials 

and culturally important items such as statues and works of art. Soiling occurs when PM 

accumulates on an object and alters the optical characteristics (appearance). The reflectivity of 

a surface may be changed or presence of particulates may alter light transmission. These 

effects can reduce the aesthetic value of a structure or result in reversible or irreversible 

damage to statues, artwork and architecturally or culturally significant buildings. Due to soiling 

of building surfaces by PM, the frequency and duration of cleaning or repainting may be 

increased. In addition to natural factors, exposure to PM may give painted surfaces a dirty 

appearance. Pigments in works of art can be degraded or discolored by atmospheric pollutants, 

especially sulfates (U.S. EPA, 2008). Previous assessments estimated household soiling benefits 

based on the Manuel et al. (1982) study of consumer expenditures on cleaning and household 

maintenance. However, the data used to estimate household soiling damages in the Manuel et 

al. study is from a 1972 consumer expenditure survey and as such may not accurately represent 

consumer preferences in the future. In light of this significant limitation, we believe that this 

study cannot provide reliable estimates of the likely magnitude of the benefits of reduced PM 

household soiling.

In order to estimate the monetized benefits associated with reducing materials damage 

and household soiling, quantitative relationships are needed between particle size, 

concentration, chemical concentrations and frequency of maintenance and repair. Such an 

analysis would require three steps:

1. Develop a national inventory of sensitive materials;
6-32

2. Derive concentration-response functions that relate material damage to change in 

pollution concentration or deposition; and,

3. Estimate the value of lost materials and/or repair of damage.

Due to data limitations and uncertainties inherent in each of these steps, we have 

chosen not to include a monetized estimate of materials damage and household soiling in this 

analysis. The PM ISA concluded that there is considerable uncertainty with regard to interaction 

of co-pollutants in regards to materials damage and soiling processes (U.S. EPA, 2009b). 

Previous EPA benefits analyses have provided quantitative estimates of materials damage (U.S. 

EPA, 2011b) and household soiling damage (U.S. EPA, 1999). Consistent with SAB advice (U.S. 

EPA, 1998), we determined that the existing data are not sufficient to calculate a reliable 

estimate of future year household soiling damages (U.S. EPA, 1998). These previous analyses 

have shown that materials damage benefits are significantly smaller than the health benefits 

associated with reduced exposure to PM2.5 and ozone, or even visibility benefits. However, 

studies of materials damage to historic buildings and outdoor artwork in Sweden (Grosclaude 

and Soguel, 1994) indicate that these benefits could be an order of magnitude larger than 

household soiling benefits.

In the absence of quantified benefits, we provide a qualitative description of the 

avoided damage associated with reducing PM and PM precursor pollutants. Table 6-8 shows 

the effect of various PM2.5 precursor pollutants and other co-pollutants on various materials.
6-33

Table 6-8. Materials Damaged by Pollutants Affected by this Rule (U.S. EPA, 2011b)

Pollutant Unquantified Effects / Damage to:

Sulfur oxides Infrastructural materials—galvanized and painted carbon steel

Commercial buildings—carbonate stone, metal, and painted wood surfaces

Residential buildings—carbonate stone, metal, and painted wood surfaces

Monuments—carbonate stone and metal

Structural aesthetics

Automotive finishes—painted metal

Hydrogen ion and 

nitrogen oxides

Infrastructural materials—galvanized and painted carbon steel

Zinc-based metal products, such as galvanized steel

Commercial and residential buildings—carbonate stone, metal, and wood surfaces

Monuments—carbonate stone and metal

Structural aesthetics

Automotive finishes—painted metal

Carbon dioxide Zinc-based metal products, such as galvanized steel

Formaldehyde Zinc-based metal products, such as galvanized steel

Particulate matter Household cleanliness (i.e., household soiling)

Ozone Rubber products (e.g., tires)

6.6 Climate Benefits

Actions taken by state and local governments to implement the proposed PM2.5

standards are likely to have implications for climate change because emission controls 

ultimately implemented to meet the standard may have impacts on emissions of long-lived 

greenhouse gas (GHG) such as carbon dioxide (CO2), short-lived climate forcers such as black 

carbon (BC), and cooling aerosols like organic carbon (OC). Our ability to quantify the climate 

effects of these proposed standards is quite limited due to lack of available information on the 

co-controlled GHG emission reductions, the energy and associated climate gas implications of 

control technologies assumed in the illustrative regulatory alternatives, and remaining 

uncertainties regarding the impact of long-lived and short-lived climate forcer impacts on 

climate change. For this RIA, we discuss qualitatively the implications of potential emission 

reductions in warming and cooling aerosols and changes in long-lived GHG emissions such as 

CO2 for the regulatory alternatives. Implementation strategies undertaken by state and local 

governments to comply with the standards may differ from the illustrative control strategies in 

this RIA. It is important to note that the net climate forcing depends on the specific 
6-34

combinations of emission reductions chosen to meet the proposed standards because of the 

differences in warming and cooling potential of the difference pollutants.

6.6.1 Climate Effects of Short Lived Climate Forcers

Pollutants that affect the energy balance of the earth are referred to as climate forcers. 

A pollutant that increases the amount of energy in the Earth’s climate system is said to exert 

“positive radiative forcing,” which leads to warming and climate change. In contrast, a pollutant 

that exerts negative radiative forcing reduces the amount of energy in the Earth’s system and 

leads to cooling.

Long-lived gases such as CO2 differ from short-lived pollutants such as BC in the length 

of time they remain in the atmosphere affecting the earth’s energy balance. Long-lived gases 

remain in the atmosphere for hundreds to thousands of years. Short-lived climate forcers 

(SLCFs), in contrast, remain in the atmosphere for short periods of time ranging from days to 

weeks. The potential to affect near-term climate change and the rate of climate change with 

policies to address these emissions is gaining attention nationally and internationally (e.g., Black

Carbon Report to Congress (currently undergoing peer review), Arctic Council Task Force, 

Global Methane Initiative, and Convention on Long-Range Trans-boundary Air Pollution of the 

United Nations Economic Commission for Europe). A recent United Nations Environmental 

Programme (UNEP) study provides the most comprehensive analysis to date of the benefits of 

measures to reduce SLCFs including methane, ozone, and black carbon assessing the health, 

climate, and agricultural benefits of a suite of mitigation technologies. The report concludes 

that the climate is changing now, and these changes have the potential to “trigger abrupt 

transitions such as the release of carbon from thawing permafrost and biodiversity loss.” While 

reducing long-lived GHGs such as CO2 is necessary to protect against long-term climate change, 

reducing SLCF gases including BC and ozone is beneficial and will slow the rate of climate 

change within the first half of this century (UNEP, 2011).

6.6.1.1 Climate Effects of Black Carbon

Black carbon is the most strongly light-absorbing component of PM2.5, and is formed by 

incomplete combustion of fossil fuels, biofuels, and biomass. The short atmospheric lifetime of 

BC lasting from days to weeks and the mechanisms by which BC affects climate distinguish it 

from long-lived GHGs like CO2. This means that actions taken to reduce the BC constituents in 

direct PM2.5 will have almost immediate effects on climate change. Emissions sources and 

ambient concentrations of BC vary geographically and temporally resulting in climate effects 

that are more regionally and seasonally dependent than the effects of long-lived, well-mixed 
6-35

GHGs. Likewise, mitigation actions for BC will produce different climate impacts depending on 

the region, season, and emission source category affected.

BC influences climate in multiple ways: directly, indirectly, and through snow and ice 

albedo. Specifically, BC affects climate directly by absorbing both incoming and outgoing 

radiation of all wavelengths. In contrast, GHGs mainly trap outgoing infrared radiation from the 

earth’s surface. Per unit of mass in the atmosphere, BC can absorb a million times more energy 

than CO2 (Bond and Sun 2005). This strong absorptive capacity is the property most relevant to 

its potential to affect the Earth’s climate. BC also affects climate indirectly by altering the 

properties of clouds, affecting cloud reflectivity, precipitation, and surface dimming. These 

indirect impacts of BC are associated with all ambient particles and may lead to cooling, but are 

not associated with long-lived well mixed GHGs. Finally, when BC is deposited on snow and ice, 

it darkens the surface and decreases reflectivity, thereby increasing absorption and accelerating 

melting.

The illustrative control strategies evaluated for this proposal include reductions in BC 

emissions that will tend to have a beneficial cooling effect on the atmosphere. BC and 

elemental carbon (EC) (or particulate elemental carbon (PEC)) are used interchangeably in this 

report because EPA traditionally estimates EC emissions rather than BC and for the purpose of 

this analysis these measures are essentially equivalent. Emissions reductions discussed below 

are from the modeled scenarios for each regulatory alterative, and not from the full attainment 

scenarios. This is because speciated PM2.5 data were not available for emissions reductions 

beyond known controls.

The snow/ice albedo effects from BC deposition have been linked to accelerated snow 

and ice melting (Wiscombe and Warren, 1980). While many glaciers around the world and 

Arctic sea ice have receded in recent decades, determining whether this phenomenon is 

attributable to BC is challenging due to other contributing factors. Emissions north of the 40th 

parallel latitude are thought to be particularly important for BC’s climate related effects in the 

Arctic (Shindell, 2007; Ramanathan and Carmichael, 2008).

Snow and ice cover in the Western U.S. has also been affected by BC. Specifically, 

deposition of BC on mountain glaciers and snow packs produces a positive snow and ice albedo 

effect, contributing to the melting of snowpack earlier in the spring and reducing the amount of 

snowmelt that normally would occur later in the spring and summer (Hadley et al. 2010). This 

has implications for freshwater resources in regions of the U.S. dependent on snow-fed or 

glacier-fed water systems. In the Sierra Nevada mountain range, Hadley et al. (2010) found BC 
6-36

at different depths in the snowpack, deposited over the winter months by snowfall. In the 

spring, the continuous uncovering of the BC contributed to the early melt. A model capturing 

the effects of soot on snow in the western U.S. shows significant decreases in snowpack 

between December and May (Qian et al., 2009). Snow water equivalent (the amount of water 

that would be produced by melting all the snow) is reduced 2-50 millimeters (mm) in 

mountainous areas, particularly over the Central Rockies, Sierra Nevadas, and western Canada. 

A study found that biomass burning emissions in Alaska and the Rocky Mountain region during 

the summer can enhance snowmelt. Dust deposition on snow, at high concentrations, can have 

similar effects to BC (Koch et al., 2007). Similarly, a study done by Painter et al. (2007) in the 

San Juan Mountains in Colorado indicated a decrease in snow cover duration of 18-35 days as a 

result of dust transported from non-local desert sources. National elemental carbon and 

organic carbon deposition maps are included in Appendix 6B to this report.

6.6.1.2 Climate Effects of Nitrates, Sulfate, and Organic Carbon (excluding BC)

The composition of the total emissions mixture is also relevant as to whether emissions 

are warming or cooling to the atmosphere. Pollutants such as SO2, NOX, and most OC particles 

tend to produce a cooling influence on climate. Exceptions include OC deposition on snow and 

ice, which leads to increased melting.

In addition, it is important to account for the indirect effects of all PM constituents on 

climate: all aerosols (including BC) affect climate indirectly by changing the reflectivity and 

lifetime of clouds. The net indirect effect of all aerosols is very uncertain but is thought to be a 

net cooling influence.

6.6.1.3 Climate Effects of Ozone

Ozone changes due to this proposed regulation are not estimated for this analysis but 

may occur due to the NOx reductions estimated. Ozone is a well-known SLCF (U.S. EPA, 2006). 

Stratospheric ozone (the upper ozone layer) is beneficial because it protects life on Earth from 

the sun’s harmful ultraviolet (UV) radiation. In contrast, tropospheric ozone (ozone in the lower 

atmosphere) is a harmful air pollutant that adversely affects human health and the 

environment and contributes significantly to regional and global climate change. Due to its 

short atmospheric lifetime, tropospheric ozone concentrations exhibit large spatial and 

temporal variability (U.S. EPA, 2009). The discernable influence of ground level ozone on 

climate leads to increases in global surface temperature and changes in hydrological cycles. 

While reducing long-lived GHGs such as CO2 is necessary to protect against long-term climate 
6-37

change, reducing SLCF gases including ozone is beneficial and will slow the rate of climate 

change within the first half of this century (UNEP, 2011).

6.6.1.4 SLCFs Summary and Conclusions

Assessing the net climate impact of SLCFs for the illustrative emission control strategies 

is outside the scope of this regulatory analysis and requires climate atmospheric modeling not 

undertaken due to time and resource constraints. Information about the amount of BC relative 

to non-BC constituents emitted from a source is important. In general, these non-BC 

constituents are emitted in greater volume than BC, counteracting the warming influence of BC. 

Qualitatively, it seems likely that BC emission reductions associated with direct emitted PM2.5

controls will be beneficial for the climate in terms of reduced radiative forcing and deposition 

on snow and ice. Reductions in OC, sulfates and nitrates are likely to produce warming in the 

atmosphere. The indirect impacts of aerosols on clouds and precipitation remain the subject of 

great uncertainty making it more difficult to estimate the quantitative impact of aerosol 

reductions on climate.

6.6.2 Climate Effects of Long-Lived Greenhouse Gases

The importance of mitigating long-lived climate gases such as CO2 has been stressed by 

the Intergovernmental Panel on Climate Change (IPCC 2007). While addressing short-lived 

climate forcers may result in more immediate climate benefits in specific areas, long-term 

policies must deal with long lived GHGs to address long-term climate change. We are unable to 

quantify the impact of the illustrative control strategies for this rulemaking on long-lived 

climate gases due lack of available data. However, State and Local governments may want to 

consider human health, welfare, and climate implications of regulatory strategies undertaken 

to implement the promulgated PM standards.

6.7 Ecosystem Benefits and Services

The effects of air pollution on the health and stability of ecosystems are potentially very 

important. At present, it is difficult to measure the impact of reducing air pollution in a national 

scale analysis across different types of ecosystems and different pollutant effects. Previous EPA 

science assessments (U.S. EPA, 2006a; U.S. EPA, 2008c; U.S. EPA, 2009b) have determined that 

air pollution can be directly linked to aquatic and terrestrial acidification, nutrient enrichment, 

vegetation injury, and metal bioaccumulation in animals. Ecosystem services are a useful 

conceptual framework for analyzing the impact of ecosystem changes on public welfare.
 

6-38

Ecosystem services can be generally defined as the benefits that individuals and 

organizations obtain from ecosystems. EPA has defined ecological goods and services as the 

“outputs of ecological functions or processes that directly or indirectly contribute to social 

welfare or have the potential to do so in the future. Some outputs may be bought and sold, but 

most are not marketed” (U.S. EPA, 2006c). Figure 6-7 provides the Millennium Ecosystem 

Assessment’s schematic demonstrating the connections between the categories of ecosystem 

services and human well-being. The interrelatedness of these categories means that any one 

ecosystem may provide multiple services. Changes in these services can affect human wellbeing by affecting security, health, social relationships, and access to basic material goods 

(MEA, 2005).

Figure 6-7. Linkages between Categories of Ecosystem Services and Components of Human 

Well-Being from Millennium Ecosystem Assessment (MEA, 2005)

In the Millennium Ecosystem Assessment (MEA, 2005), ecosystem services are classified 

into four main categories:

1. Provisioning: Products obtained from ecosystems, such as the production of food 

and water

2. Regulating: Benefits obtained from the regulation of ecosystem processes, such as 

the control of climate and disease

3. Cultural: Nonmaterial benefits that people obtain from ecosystems through spiritual 

enrichment, cognitive development, reflection, recreation, and aesthetic 

experiences
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4. Supporting: Services necessary for the production of all other ecosystem services, 

such as nutrient cycles and crop pollination

The monetization of ecosystem services generally involves estimating the value of 

ecological goods and services based on what people are willing to pay (WTP) to increase 

ecological services or by what people are willing to accept (WTA) in compensation for 

reductions in them (U.S. EPA, 2006c). There are three primary approaches for estimating the 

monetary value of ecosystem services: market-based approaches, revealed preference 

methods, and stated preference methods (U.S. EPA, 2006c). Because economic valuation of

ecosystem services can be difficult, nonmonetary valuation using biophysical measurements 

and concepts also can be used. An example of a nonmonetary valuation method is the use of 

relative-value indicators (e.g., a flow chart indicating uses of a water body, such as boatable, 

fishable, swimmable, etc.). It is necessary to recognize that in the analysis of the environmental 

responses associated with any particular policy or environmental management action, only a 

subset of the ecosystem services likely to be affected are readily identified. Of those ecosystem 

services that are identified, only a subset of the changes can be quantified. Within those 

services whose changes can be quantified, only a few will likely be monetized, and many will 

remain nonmonetized. The stepwise concept leading up to the valuation of ecosystems services 

is graphically depicted in Figure 6-8.

Figure 6-8. Schematic of the Benefits Assessment Process (U.S. EPA, 2006c)
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6.7.1 Ecosystem Benefits for Metallic and Organic Constituents of PM

Several significant ecological effects are associated with deposition of chemical 

constituents of ambient PM such as metals and organics (U.S. EPA, 2009b). The trace metal 

constituents of PM include cadmium, copper, chromium, mercury, nickel, zinc, and lead. The 

organics include persistent organic pollutants (POPs), polyaromatic hydrocarbons (PAHs) and 

polybromiated diphenyl ethers (PBDEs). Exposure to PM for direct effects occur via deposition 

(e.g., wet, dry or occult) to vegetation surfaces, while indirect effects occur via deposition to 

ecosystem soils or surface waters where the deposited constituents of PM then interacts with 

biological organisms. While both fine and coarse-mode particles may affect plants and other 

organisms, more often the chemical constituents drive the ecosystem response to PM (Grantz 

et al., 2003). Ecological effects of PM include direct effects to metabolic processes of plant 

foliage; contribution to total metal loading resulting in alteration of soil biogeochemistry and 

microbiology, plant and animal growth and reproduction; and contribution to total organics 

loading resulting in bioaccumulation and biomagnification across trophic levels.

The PM ISA concludes that a causal relationship is likely to exist between deposition of 

PM and a variety of effects on individual organisms and ecosystems (U.S. EPA 2009b). Most 

direct ecosystem effects associated with particulate pollution occur in severely polluted areas 

near industrial point sources (quarries, cement kilns, metal smelting) (U.S. EPA, 2009b). 

However the PM ISA also finds, in many cases, it is difficult to characterize the nature and 

magnitude of effects and to quantify relationships between ambient concentrations of PM and 

ecosystem response due to significant data gaps and uncertainties as well as considerable 

variability that exists in the components of PM and their various ecological effects (U.S. EPA, 

2009b).

Particulate matter can adversely impact plants and ecosystem services provided by 

plants by deposition to vegetative surfaces (U.S. EPA, 2009b). Particulates deposited on the 

surfaces of leaves and needles can block light, altering the radiation received by the plant. PM 

deposition near sources of heavy deposition can obstruct stomata limiting gas exchange, 

damage leaf cuticles and increase plant temperatures (U.S. EPA, 2009b). Plants growing on 

roadsides exhibit impact damage from near-road PM deposition, having higher levels of 

organics and heavy metals, and accumulate salt from road de-icing during winter months (U.S. 

EPA, 2009b). In addition, atmospheric PM can convert direct solar radiation to diffuse radiation, 

which is more uniformly distributed in a tree canopy, allowing radiation to reach lower leaves 

(U.S. EPA, 2009b). Decreases in crop yields (a provisioning service) due to reductions in solar 
6-41

radiation have been attributed to regional scale air pollution in other counties with especially 

severe regional haze (Chameides et al., 1999).

In addition to damage to plant surfaces, deposited PM can be taken up by plants from 

soil or foliage. Copper, zinc, and nickel have been shown to be directly toxic to vegetation under 

field conditions (U.S. EPA, 2009b). The ability of vegetation to take up heavy metals is 

dependent upon the amount, solubility and chemical composition of the deposited PM. Uptake 

of PM by plants from soils and vegetative surfaces can disrupt photosynthesis, alter pigments 

and mineral content, reduce plant vigor, decrease frost hardiness and impair root development.

Particulate matter can also contain organic air toxic pollutants, including PAHs, which 

are a class of polycyclic organic matter (POM). PAHs can accumulate in sediments and 

bioaccumulate in freshwater, flora and fauna. The uptake of organics depends on the plant 

species, site of deposition, physical and chemical properties of the organic compound and 

prevailing environmental conditions (U.S. EPA, 2009b). Different species can have different 

uptake rates of PAHs. For example, zucchini (Cucurbita pepo) accumulated significantly more 

PAHs than related plant species (Parrish et al., 2006). PAHs can accumulate to high enough 

concentrations in some coastal environments to pose an environmental health threat that 

includes cancer in fish populations, toxicity to organisms living in the sediment and risks to 

those (e.g., migratory birds) that consume these organisms (Simcik et al., 1996; Simcik et al., 

1999). Atmospheric deposition of particles is thought to be the major source of PAHs to the 

sediments of Lake Michigan, Chesapeake Bay, Tampa Bay and other coastal areas of the U.S. 

(Arzavus, Dickhut, and Canuel, 2001).

Contamination of plant leaves by heavy metals can lead to elevated concentrations in 

the soil. Trace metals absorbed into the plant, frequently bind to the leaf tissue, and then are 

lost when the leaf drops. As the fallen leaves decompose, the heavy metals are transferred into 

the soil (Cotrufo et al., 1995; Niklinska et al., 1998). Many of the major indirect plant responses 

to PM deposition are chiefly soil-mediated and depend on the chemical composition of 

individual components of deposited PM. Upon entering the soil environment, PM pollutants 

can alter ecological processes of energy flow and nutrient cycling, inhibit nutrient uptake to 

plants, change microbial community structure and, affect biodiversity. Accumulation of heavy 

metals in soils depends on factors such as local soil characteristics, geologic origin of parent 

soils, and metal bioavailability. Heavy metals, such as zinc, copper, and cadmium, and some 

pesticides can interfere with microorganisms that are responsible for decomposition of soil 

litter, an important regulating ecosystem service that serves as a source of soil nutrients (U.S. 

EPA, 2009b). Surface litter decomposition is reduced in soils having high metal concentrations. 
6-42

Soil communities have associated bacteria, fungi, and invertebrates that are essential to soil 

nutrient cycling processes. Changes to the relative species abundance and community 

composition are associated with deposited PM to soil biota (U.S. EPA, 2009b).

Atmospheric deposition can be the primary source of some organics and metals to 

watersheds. Deposition of PM to surfaces in urban settings increases the metal and organic 

component of storm water runoff (U.S. EPA, 2009b). This atmospherically-associated pollutant 

burden can then be toxic to aquatic biota. The contribution of atmospherically deposited PAHs 

to aquatic food webs was demonstrated in high elevation mountain lakes with no other 

anthropogenic contaminant sources (U.S. EPA, 2009b). Metals associated with PM deposition 

limit phytoplankton growth, affecting aquatic trophic structure. Long-range atmospheric 

transport of 47 pesticides and degradation products to the snowpack in seven national parks in 

the Western U.S. was recently quantified indicating PM-associated contaminant inputs to 

receiving waters during spring snowmelt (Hageman et al., 2006).

The recently completed Western Airborne Contaminants Assessment Project (WACAP) is 

the most comprehensive database on contaminant transport and PM depositional effects on 

sensitive ecosystems in the Western U.S. (Landers et al., 2008). In this project, the transport, 

fate, and ecological impacts of anthropogenic contaminants from atmospheric sources were 

assessed from 2002 to 2007 in seven ecosystem components (air, snow, water, sediment, 

lichen, conifer needles and fish) in eight core national parks. The study concluded that 

bioaccumulation of semi-volatile organic compounds occurred throughout park ecosystems, an 

elevational gradient in PM deposition exists with greater accumulation in higher altitude areas, 

and contaminants accumulate in proximity to individual agriculture and industry sources, which 

is counter to the original working hypothesis that most of the contaminants would originate 

from Eastern Europe and Asia.

Although there is considerable data on impacts of PM on ecological receptors, few 

studies link ambient PM levels to observed effect. This is due, in part, to the nature, deposition, 

transport and fate of PM in ecosystems. Some of the difficulties in quantifying the ecosystem 

benefits associated with reduced PM deposition include the following:

 PM is not a single pollutant, but a heterogeneous mixture of particles differing in 

size, origin and chemical composition. Since vegetation and other ecosystem 

components are affected more by particulate chemistry than size fraction, exposure 

to a given mass concentration of airborne PM may lead to widely differing plant or 

ecosystem responses, depending on the particular mix of deposited particles.
6-43

 Composition of ambient PM varies in time and space and the particulate mixture 

may have synergistic, antagonistic or additive effects on ecological receptors 

depending upon the chemical species present.

 Presence of co-pollutants makes it difficult to attribute observed effects to 

ecological receptors to PM alone or one component of deposited PM.

 Ecosystem effects linked to PM are difficult to determine because the changes may 

not be observed until pollutant deposition has occurred for many decades. 

Furthermore, many PM components bioaccumulate over time in organisms or 

plants, making correlations to ambient levels of PM difficult.

 Multiple ecological stressors can confound attempts to link specific ecosystem 

responses to PM deposition. These stressors can be anthropogenic (e.g., habitat 

destruction, eutrophication, other pollutants) or natural (e.g., drought, fire, disease). 

Deposited PM interacts with other stressors to affect ecosystem patterns and 

processes.

 Each ecosystem has a unique topography, underlying bedrock, soils, climate, 

meteorology, hydrologic regime, natural and land use history, and species 

composition. Sensitivity of ecosystem response can be highly variable in space and 

time. Because of this variety and lack of data for most ecosystems, extrapolating 

these effects from one ecosystem to another is highly uncertain.

6.7.2 Ecosystem Benefits from Reductions in Nitrogen and Sulfur Emissions

Emissions of the PM precursors, such as nitrogen and sulfur oxides occur over large 

regions of North America. Once these pollutants are lofted to the middle and upper 

troposphere, they typically have a much longer lifetime and, with the generally stronger winds 

at these altitudes, can be transported long distances from their source regions. The length scale 

of this transport is highly variable owing to differing chemical and meteorological conditions 

encountered along the transport path (U.S. EPA, 2008c). Secondary particles are formed from 

NOX and SO2 gaseous emissions and associated chemical reactions in the atmosphere. 

Deposition can occur in either a wet (i.e., rain, snow, sleet, hail, clouds, or fog) or dry form (i.e., 

gases or particles). Together these emissions are deposited onto terrestrial and aquatic 

ecosystems across the U.S., contributing to the problems of acidification, nutrient enrichment, 

and methylmercury production as represented in Figures 6-9 and 6-10. Although there is some 

evidence that nitrogen deposition may have positive effects on agricultural and forest output 

through passive fertilization, it is likely that the overall value is very small relative to other 

health and welfare effects. In addition to deposition effects, SO2 can affect vegetation at 

ambient levels near pollution sources.
 

6-44

Figure 6-9. Schematics of Ecological Effects of Nitrogen and Sulfur Deposition

NOX 

Atmospheric 

Fate and 

Transport

Deposition 

Process

Acidification

Aquatic 

Ecosystems

Terrestrial 

Ecosystems

Nutrient 

Enrichment

Aquatic 

Ecosystems

Terrestrial 

Ecosystems

SO2 

Atmospheric 

Fate and 

Transport

Deposition 

Process

Acidification

Aquatic 

Ecosystems

Terrestrial 

Ecosystems

Methylmercury 

Production
 

6-45

Figure 6-10. Nitrogen and Sulfur Cycling, and Interactions in the Environment

Source: U.S. EPA, 2008c

The atmospheric lifetimes of particles vary with particle size. Accumulation-mode 

particles such as sulfates are kept in suspension by normal air motions and have a lower 

deposition velocity than coarse-mode particles; they can be transported thousands of 

kilometers and remain in the atmosphere for a number of days. They are removed from the 

atmosphere primarily by cloud processes. Particulates affect acid deposition by serving as cloud 

condensation nuclei and contribute directly to the acidification of rain. In addition, the gasphase species that lead to the dry deposition of acidity are also precursors of particles. 

Therefore, reductions in NOX and SO2 emissions will decrease both acid deposition and PM 

concentrations, but not necessarily in a linear fashion (U.S. EPA, 2008c). Sulfuric acid is also 

deposited on surfaces by dry deposition and can contribute to environmental effects (U.S. EPA, 

2008c).

6.7.2.1 Ecological Effects of Acidification

Deposition of nitrogen and sulfur can cause acidification, which alters biogeochemistry 

and affects animal and plant life in terrestrial and aquatic ecosystems across the U.S. Soil 

acidification is a natural process, but is often accelerated by acidifying deposition, which can 

decrease concentrations of exchangeable base cations in soils (U.S. EPA, 2008c). Major 
6-46

terrestrial effects include a decline in sensitive tree species, such as red spruce (Picea rubens) 

and sugar maple (Acer saccharum) (U.S. EPA, 2008c). Biological effects of acidification in 

terrestrial ecosystems are generally linked to aluminum toxicity and decreased ability of plant 

roots to take up base cations (U.S. EPA, 2008c). Decreases in the acid neutralizing capacity and 

increases in inorganic aluminum concentration contribute to declines in zooplankton, macro 

invertebrates, and fish species richness in aquatic ecosystems (U.S. EPA, 2008c).

Geology (particularly surficial geology) is the principal factor governing the sensitivity of 

terrestrial and aquatic ecosystems to acidification from nitrogen and sulfur deposition (U.S. 

EPA, 2008c). Geologic formations having low base cation supply generally underlie the 

watersheds of acid-sensitive lakes and streams. Other factors contribute to the sensitivity of 

soils and surface waters to acidifying deposition, including topography, soil chemistry, land use, 

and hydrologic flow path (U.S. EPA, 2008c).

Aquatic Acidification. Aquatic effects of acidification have been well studied in the U.S. 

and elsewhere at various trophic levels. These studies indicate that aquatic biota have been 

affected by acidification at virtually all levels of the food web in acid sensitive aquatic 

ecosystems. The ISA for NOx/SOx—Ecological Criteria concluded that the evidence is sufficient 

to infer a causal relationship between acidifying deposition and effects on biogeochemistry 

related to aquatic ecosystems and biota in aquatic ecosystems (U.S. EPA, 2008c). Effects have 

been most clearly documented for fish, aquatic insects, other invertebrates, and algae. 

Biological effects are primarily attributable to a combination of low pH and high inorganic 

aluminum concentrations. Such conditions occur more frequently during rainfall and snowmelt 

that cause high flows of water and less commonly during low-flow conditions, except where 

chronic acidity conditions are severe. Biological effects of episodes include reduced fish 

condition factor34, changes in species composition and declines in aquatic species richness 

across multiple taxa, ecosystems and regions. These conditions may also result in direct fish 

mortality (Van Sickle et al., 1996). Biological effects in aquatic ecosystems can be divided into 

two major categories: effects on health, vigor, and reproductive success; and effects on 

biodiversity. Surface water with ANC values greater than 50 μeq/L generally provides moderate 

protection for most fish (i.e., brook trout, others) and other aquatic organisms (U.S. EPA, 

2009c). Table 6-9 provides a summary of the biological effects experienced at various ANC 

levels.

 34 Condition factor is an index that describes the relationship between fish weight and length, and is one measure 

of sublethal acidification stress that has been used to quantify effects of acidification on an individual fish (U.S.

EPA, 2008f).
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Table 6-9. Aquatic Status Categories

Category Label ANC Levels Expected Ecological Effects

Acute 

Concern

<0 micro 

equivalent per 

Liter (μeq/L)

Near complete loss of fish populations is expected. Planktonic communities have 

extremely low diversity and are dominated by acidophilic forms. The number of 

individuals in plankton species that are present is greatly reduced.

Severe 

Concern 0–20 μeq/L

Highly sensitive to episodic acidification. During episodes of high acidifying 

deposition, brook trout populations may experience lethal effects. Diversity and 

distribution of zooplankton communities decline sharply. 

Elevated 

Concern 20–50 μeq/L

Fish species richness is greatly reduced (i.e., more than half of expected species 

can be missing). On average, brook trout populations experience sublethal 

effects, including loss of health, reproduction capacity, and fitness. Diversity and 

distribution of zooplankton communities decline.

Moderate 

Concern 50–100 μeq/L

Fish species richness begins to decline (i.e., sensitive species are lost from lakes). 

Brook trout populations are sensitive and variable, with possible sublethal 

effects. Diversity and distribution of zooplankton communities also begin to 

decline as species that are sensitive to acidifying deposition are affected.

Low Concern >100 μeq/L

Fish species richness may be unaffected. Reproducing brook trout populations 

are expected where habitat is suitable. Zooplankton communities are unaffected 

and exhibit expected diversity and distribution.

A number of national and regional assessments have been conducted to estimate the 

distribution and extent of surface water acidity in the U.S. (U.S. EPA, 2008c). As a result, several 

regions of the U.S. have been identified as containing a large number of lakes and streams that 

are seriously impacted by acidification. Figure 6-11 illustrates those areas of the U.S. where 

aquatic ecosystems are at risk from acidification.

Because acidification primarily affects the diversity and abundance of aquatic biota, it 

also affects the ecosystem services that are derived from the fish and other aquatic life found in 

these surface waters.

While acidification is unlikely to have serious negative effects on, for example, water 

supplies, it can limit the productivity of surface waters as a source of food (i.e., fish). In the 

northeastern United States, the surface waters affected by acidification are not a major source 

of commercially raised or caught fish; however, they are a source of food for some recreational 

and subsistence fishermen and for other consumers. For example, there is evidence that certain 

population subgroups in the northeastern United States, such as the Hmong and Chippewa 

ethnic groups, have particularly high rates of self-caught fish consumption (Hutchison and Kraft, 

1994; Peterson et al., 1994). However, it is not known if and how their consumption patterns 

are affected by the reductions in available fish populations caused by surface water 

acidification.
 

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Figure 6-11. Areas Potentially Sensitive to Aquatic Acidification

Source: U.S. EPA, 2008c

Inland surface waters support several cultural services, including aesthetic and 

educational services and recreational fishing. Recreational fishing in lakes and streams is among 

the most popular outdoor recreational activities in the northeastern United States. Based on 

studies conducted in the northeastern United States, Kaval and Loomis (2003) estimated 

average consumer surplus values per day of $36 for recreational fishing (in 2007 dollars); 

therefore, the implied total annual value of freshwater fishing in the northeastern United States 

was $5.1 billion in 2006.35 For recreation days, consumer surplus value is most commonly 

measured using recreation demand, travel cost models.

Another estimate of the overarching ecological benefits associated with reducing lake 

acidification levels in Adirondacks National Park can be derived from the contingent valuation 

(CV) survey (Banzhaf et al., 2006), which elicited values for specific improvements in 

acidification-related water quality and ecological conditions in Adirondack lakes. The survey 

described a base version with minor improvements said to result from the program, and a 

 

35 These estimates reflect the total value of the service, not the marginal change in the value of the service as a 

result of the emission reductions achieved by this rule. 
6-49

scope version with large improvements due to the program and a gradually worsening status 

quo. After adapting and transferring the results of this study and converting the 10-year annual 

payments to permanent annual payments using discount rates of 3% and 5%, the WTP 

estimates ranged from $48 to $107 per year per household (in 2004 dollars) for the base 

version and $54 to $154 for the scope version. Using these estimates, the aggregate annual 

benefits of eliminating all anthropogenic sources of NOx and SOx emissions were estimated to 

range from $291 million to $829 million (U.S. EPA, 2009c).36

In addition, inland surface waters provide a number of regulating services associated 

with hydrological and climate regulation by providing environments that sustain aquatic food 

webs. These services are disrupted by the toxic effects of acidification on fish and other aquatic 

life. Although it is difficult to quantify these services and how they are affected by acidification, 

some of these services may be captured through measures of provisioning and cultural services.

Terrestrial Acidification. Acidifying deposition has altered major biogeochemical 

processes in the U.S. by increasing the nitrogen and sulfur content of soils, accelerating nitrate 

and sulfate leaching from soil to drainage waters, depleting base cations (especially calcium and 

magnesium) from soils, and increasing the mobility of aluminum. Inorganic aluminum is toxic to 

some tree roots. Plants affected by high levels of aluminum from the soil often have reduced 

root growth, which restricts the ability of the plant to take up water and nutrients, especially 

calcium (U. S. EPA, 2008c). These direct effects can, in turn, influence the response of these 

plants to climatic stresses such as droughts and cold temperatures. They can also influence the 

sensitivity of plants to other stresses, including insect pests and disease (Joslin et al., 1992) 

leading to increased mortality of canopy trees. In the U.S., terrestrial effects of acidification are 

best described for forested ecosystems (especially red spruce and sugar maple ecosystems) 

with additional information on other plant communities, including shrubs and lichen (U.S. EPA, 

2008c). The ISA for NOx/SOx—Ecological Criteria concluded that the evidence is sufficient to 

infer a causal relationship between acidifying deposition and effects on biogeochemistry 

related to terrestrial ecosystems and biota in terrestrial ecosystems (U.S. EPA, 2008c).

Certain ecosystems in the continental U.S. are potentially sensitive to terrestrial 

acidification, which is the greatest concern regarding nitrogen and sulfur deposition U.S. EPA 

(2008c). Figure 6-12 depicts the areas across the U.S. that are potentially sensitive to terrestrial 

acidification.

 36 These estimates reflect the total value of the service, not the marginal change in the value of the service as a 

result of the emission reductions achieved by this rule.
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Figure 6-12. Areas Potentially Sensitive to Terrestrial Acidification

Source: U.S. EPA, 2008c

Both coniferous and deciduous forests throughout the eastern U.S. are experiencing 

gradual losses of base cation nutrients from the soil due to accelerated leaching from acidifying 

deposition. This change in nutrient availability may reduce the quality of forest nutrition over 

the long term. Evidence suggests that red spruce and sugar maple in some areas in the eastern 

U.S. have experienced declining health because of this deposition. For red spruce, (Picea 

rubens) dieback or decline has been observed across high elevation landscapes of the 

northeastern U.S., and to a lesser extent, the southeastern U.S., and acidifying deposition has 

been implicated as a causal factor (DeHayes et al., 1999). Figure 6-13 shows the distribution of 

red spruce (brown) and sugar maple (green) in the eastern U.S.

Terrestrial acidification affects several important ecological endpoints, including 

declines in habitat for threatened and endangered species (cultural), declines in forest 

aesthetics (cultural), declines in forest productivity (provisioning), and increases in forest soil 

erosion and reductions in water retention (cultural and regulating).
 

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Figure 6-13. Distribution of Red Spruce (pink) and Sugar Maple (green) in the Eastern U.S.

Source: U.S. EPA, 2008c

Forests in the northeastern United States provide several important and valuable 

provisioning services in the form of tree products. Sugar maples are a particularly important 

commercial hardwood tree species, providing timber and maple syrup. In the United States, 

sugar maple saw timber was nearly 900 million board feet in 2006 (USFS, 2006), and annual 

production of maple syrup was nearly 1.4 million gallons, accounting for approximately 19% of 

worldwide production. The total annual value of U.S. production in these years was

approximately $160 million (NASS, 2008).37 Red spruce is also used in a variety of products 

including lumber, pulpwood, poles, plywood, and musical instruments. The total removal of red 

spruce saw timber from timberland in the United States was over 300 million board feet in 

2006 (USFS, 2006).

Forests in the northeastern United States are also an important source of cultural 

ecosystem services—nonuse (i.e., existence value for threatened and endangered species), 

 

37 These estimates reflect the total value of the service, not the marginal change in the value of the service as a 

result of the emission reductions achieved by this rule. 
6-52

recreational, and aesthetic services. Red spruce forests are home to two federally listed species 

and one delisted species:

1. Spruce-fir moss spider (Microhexura montivaga)—endangered

2. Rock gnome lichen (Gymnoderma lineare)—endangered

3. Virginia northern flying squirrel (Glaucomys sabrinus fuscus)—delisted, but 

important

Forestlands support a wide variety of outdoor recreational activities, including fishing, 

hiking, camping, off-road driving, hunting, and wildlife viewing. Regional statistics on 

recreational activities that are specifically forest based are not available; however, more 

general data on outdoor recreation provide some insights into the overall level of recreational 

services provided by forests. More than 30% of the U.S. adult population visited a wilderness or 

primitive area during the previous year and engaged in day hiking (Cordell et al., 2008). From 

1999 to 2004, 16% of adults in the northeastern United States participated in off-road vehicle 

recreation, for an average of 27 days per year (Cordell et al., 2005). The average consumer 

surplus value per day of off-road driving in the United States was $25 (in 2007 dollars), and the 

implied total annual value of off-road driving recreation in the northeastern United States was 

more than $9 billion (Kaval and Loomis, 2003). More than 5% of adults in the northeastern 

United States participated in nearly 84 million hunting days (U.S. FWS and U.S. Census Bureau, 

2007). Ten percent of adults in northeastern states participated in wildlife viewing away from 

home on 122 million days in 2006. For these recreational activities in the northeastern United 

States, Kaval and Loomis (2003) estimated average consumer surplus values per day of $52 for 

hunting and $34 for wildlife viewing (in 2007 dollars). The implied total annual value of hunting 

and wildlife viewing in the northeastern United States was, therefore, $4.4 billion and $4.2 

billion, respectively, in 2006 (U.S. EPA, 2009c).38

As previously mentioned, it is difficult to estimate the portion of these recreational 

services that are specifically attributable to forests and to the health of specific tree species. 

However, one recreational activity that is directly dependent on forest conditions is fall color 

viewing. Sugar maple trees, in particular, are known for their bright colors and are, therefore, 

an essential aesthetic component of most fall color landscapes. A survey of residents in the 

Great Lakes area found that roughly 30% of residents reported at least one trip in the previous 

year involving fall color viewing (Spencer and Holecek, 2007). In a separate study conducted in 

 38 These estimates reflect the total value of the service, not the marginal change in the value of the service as a 

result of the emission reductions achieved by this rule.
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Vermont, Brown (2002) reported that more than 22% of households visiting Vermont in 2001 

made the trip primarily for viewing fall colors.

Two studies estimated values for protecting high-elevation spruce forests in the 

southern Appalachian Mountains. Kramer et al. (2003) conducted a contingent valuation study 

estimating households’ WTP for programs to protect remaining high-elevation spruce forests 

from damages associated with air pollution and insect infestation. Median household WTP was 

estimated to be roughly $29 (in 2007 dollars) for a smaller program, and $44 for the more 

extensive program. Jenkins et al. (2002) conducted a very similar study in seven Southern 

Appalachian states on a potential program to maintain forest conditions at status quo levels. 

The overall mean annual WTP for the forest protection programs was $208 (in 2007 dollars). 

Multiplying the average WTP estimate from these studies by the total number of households in 

the seven-state Appalachian region results in an aggregate annual range of $470 million to $3.4 

billion for avoiding a significant decline in the health of high-elevation spruce forests in the 

Southern Appalachian region (U.S. EPA, 2009c).39

Forests in the northeastern United States also support and provide a wide variety of 

valuable regulating services, including soil stabilization and erosion control, water regulation, 

and climate regulation. The total value of these ecosystem services is very difficult to quantify 

in a meaningful way, as is the reduction in the value of these services associated with total 

nitrogen and sulfur deposition. As terrestrial acidification contributes to root damages, reduced 

biomass growth, and tree mortality, all of these services are likely to be affected; however, the 

magnitude of these impacts is currently very uncertain.

6.7.2.2 Ecological Effects from Nitrogen Enrichment

Aquatic Enrichment. The ISA for NOx/SOx—Ecological Criteria concluded that the 

evidence is sufficient to infer a causal relationship between nitrogen deposition and the 

alteration of species richness, species composition, and biodiversity in wetland, freshwater 

aquatic and coastal marine ecosystems (U.S. EPA, 2008c).

One of the main adverse ecological effects resulting from nitrogen deposition, 

particularly in the Mid-Atlantic region of the United States, is the effect associated with nutrient 

enrichment in estuarine waters. A recent assessment of 141 estuaries nationwide by the 

National Oceanic and Atmospheric Administration (NOAA) concluded that 19 estuaries (13%) 

suffered from moderately high or high levels of eutrophication due to excessive inputs of both 

 39 These estimates reflect the marginal value of the service for the hypothetical program described in the survey, 

not the marginal change in the value of the service as a result of the emission reductions achieved by this rule.
6-54

N and phosphorus, and a majority of these estuaries are located in the coastal area from North 

Carolina to Massachusetts (NOAA, 2007). For estuaries in the Mid-Atlantic region, the 

contribution of atmospheric distribution to total N loads is estimated to range between 10% 

and 58% (Valigura et al., 2001).

Eutrophication in estuaries is associated with a range of adverse ecological effects. The 

conceptual framework developed by NOAA emphasizes four main types of eutrophication 

effects—low dissolved oxygen (DO), harmful algal blooms (HABs), loss of submerged aquatic 

vegetation (SAV), and low water clarity. Low DO disrupts aquatic habitats, causing stress to fish 

and shellfish, which, in the short-term, can lead to episodic fish kills and, in the long-term, can 

damage overall growth in fish and shellfish populations. Low DO also degrades the aesthetic 

qualities of surface water. In addition to often being toxic to fish and shellfish, and leading to 

fish kills and aesthetic impairments of estuaries, HABs can, in some instances, also be harmful 

to human health. SAV provides critical habitat for many aquatic species in estuaries and, in 

some instances, can also protect shorelines by reducing wave strength; therefore, declines in 

SAV due to nutrient enrichment are an important source of concern. Low water clarity is in part 

the result of accumulations of both algae and sediments in estuarine waters. In addition to 

contributing to declines in SAV, high levels of turbidity also degrade the aesthetic qualities of 

the estuarine environment.

Estuaries in the eastern United States are an important source of food production, in 

particular fish and shellfish production. The estuaries are capable of supporting large stocks of 

resident commercial species, and they serve as the breeding grounds and interim habitat for 

several migratory species. To provide an indication of the magnitude of provisioning services 

associated with coastal fisheries, from 2005 to 2007, the average value of total catch was $1.5 

billion per year. It is not known, however, what percentage of this value is directly attributable 

to or dependent upon the estuaries in these states.

In addition to affecting provisioning services through commercial fish harvests, 

eutrophication in estuaries may also affect the demand for seafood. For example, a wellpublicized toxic pfiesteria bloom in the Maryland Eastern Shore in 1997, which involved 

thousands of dead and lesioned fish, led to an estimated $56 million (in 2007 dollars) in lost 

seafood sales for 360 seafood firms in Maryland in the months following the outbreak (Lipton, 

1999).

Estuaries in the United States also provide an important and substantial variety of 

cultural ecosystem services, including water-based recreational and aesthetic services. The 
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water quality in the estuary directly affects the quality of these experiences. For example, there 

were 26 million days of saltwater fishing coastal states from North Carolina to Massachusetts in 

2006 (FWA and Census, 2007). Assuming an average consumer surplus value for a fishing day at 

$36 (in 2007 dollars) in the Northeast and $87 in the Southeast (Kaval and Loomis, 2003), the 

aggregate value was approximately $1.3 billion (in 2007 dollars) (U.S. EPA, 2009c).40 In addition, 

almost 6 million adults participated in motorboating in coastal states from North Carolina to 

Massachusetts, for a total of nearly 63 million days annually during 1999–2000 (Leeworthy and 

Wiley, 2001). Using a national daily value estimate of $32 (in 2007 dollars) for motorboating 

(Kaval and Loomis (2003), the aggregate value of these coastal motorboating outings was $2 

billion per year (U.S. EPA, 2009c).41 Almost 7 million participated in birdwatching for 175 million 

days per year, and more than 3 million participated in visits to non-beach coastal waterside 

areas.

Estuaries and marshes have the potential to support a wide range of regulating services, 

including climate, biological, and water regulation; pollution detoxification; erosion prevention; 

and protection against natural hazards from declines in SAV (MEA, 2005). SAV can help reduce 

wave energy levels and thus protect shorelines against excessive erosion, which increases the 

risks of episodic flooding and associated damages to near-shore properties or public 

infrastructure or even contribute to shoreline retreat.

We are unable to provide an estimate of the aquatic enrichment benefits associated 

with the alternative standard level combinations due to data, time, and resource limitations.

Terrestrial Enrichment. Terrestrial enrichment occurs when terrestrial ecosystems 

receive N loadings in excess of natural background levels, through either atmospheric 

deposition or direct application. Evidence presented in the Integrated Science Assessment (U.S. 

EPA, 2008c) supports a causal relationship between atmospheric N deposition and 

biogeochemical cycling and fluxes of N and carbon in terrestrial systems. Furthermore, 

evidence summarized in the report supports a causal link between atmospheric N deposition 

and changes in the types and number of species and biodiversity in terrestrial systems. 

Nitrogen enrichment occurs over a long time period; as a result, it may take as much as 50 

years or more to see changes in ecosystem conditions and indicators. This long time scale also 

affects the timing of the ecosystem service changes. The ISA for NOx/SOx—Ecological Criteria 

 40 These estimates reflect the total value of the service, not the marginal change in the value of the service as a 

result of the emission reductions achieved by this rule. 41 These estimates reflect the total value of the service, not the marginal change in the value of the service as a 

result of the emission reductions achieved by this rule.
6-56

concluded that the evidence is sufficient to infer a causal relationship between nitrogen 

deposition and the alteration of species richness, species composition, and biodiversity in 

terrestrial ecosystems (U.S. EPA, 2008c).

One of the main provisioning services potentially affected by N deposition is grazing 

opportunities offered by grasslands for livestock production in the Central U.S. Although N 

deposition on these grasslands can offer supplementary nutritive value and promote overall 

grass production, there are concerns that fertilization may favor invasive grasses and shift the 

species composition away from native grasses. This process may ultimately reduce the 

productivity of grasslands for livestock production. Losses due to invasive grasses can be 

significant; for example, based on a bioeconomic model of cattle grazing in the upper Great 

Plains, Leitch, Leistritz, and Bangsund (1996) and Leistritz, Bangsund, and Hodur (2004) 

estimated $130 million in losses due to a leafy spurge infestation in the Dakotas, Montana, and 

Wyoming.42 However, the contribution of N deposition to these losses is still uncertain.

Terrestrial nutrient enrichment also affects cultural and regulating services. For 

example, in California, Coastal Sage Scrub (CSS) habitat concerns focus on a decline in CSS and 

an increase in nonnative grasses and other species, impacts on the viability of threatened and 

endangered species associated with CSS, and an increase in fire frequency. Changes in Mixed 

Conifer Forest (MCF) include changes in habitat suitability and increased tree mortality, 

increased fire intensity, and a change in the forest’s nutrient cycling that may affect surface 

water quality through nitrate leaching (U.S. EPA, 2008c). CSS and MCF are an integral part of 

the California landscape, and together the ranges of these habitats include the densely 

populated and valuable coastline and the mountain areas. Numerous threatened and 

endangered species at both the state and federal levels reside in CSS and MCF. The value that 

California residents and the U.S. population as a whole place on CSS and MCF habitats is 

reflected in the various federal, state, and local government measures that have been put in 

place to protect these habitats, including the Endangered Species Act, conservation planning 

programs, and private and local land trusts. CSS and MCF habitat are showcased in many 

popular recreation areas in California, including several national parks and monuments. In 

addition, millions of individuals are involved in fishing, hunting, and wildlife viewing in California 

every year (DOI, 2007). The quality of these trips depends in part on the health of the 

ecosystems and their ability to support the diversity of plants and animals found in important 

habitats found in CSS or MCF ecosystems and the parks associated with those ecosystems. 

 42 These estimates reflect the total value of the service, not the marginal change in the value of the service as a 

result of the emission reductions achieved by this rule.
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Based on analyses in the NOx SOx REA average values of the total benefits in 2006 from fishing, 

hunting, and wildlife viewing away from home in California were approximately $950 million, 

$170 million, and $3.6 billion, respectively (U.S. EPA, 2009c).43 In addition, data from California 

State Parks (2003) indicate that in 2002, 69% of adult residents participated in trail hiking for an 

average of 24 days per year. The aggregate annual benefit for California residents from trail 

hiking in 2007 was $11 billion (U.S. EPA, 2009c).44 It is not currently possible to quantify the loss 

in value of services due to nitrogen deposition as those losses are already reflected in the 

estimates of the contemporaneous total value of these recreational activities. Restoration of 

services through decreases in nitrogen deposition would likely increase the total value of 

recreational services.

Fire regulation is also an important regulating service that could be affected by nutrient 

enrichment of the CSS and MCF ecosystems by encouraging growth of more flammable grasses, 

increasing fuel loads, and altering the fire cycle. Over the 5-year period from 2004 to 2008, 

Southern California experienced, on average, over 4,000 fires per year burning, on average, 

over 400,000 acres per year (National Association of State Foresters [NASF], 2009). It is not 

possible at this time to quantify the contribution of nitrogen deposition, among many other 

factors, to increased fire risk.

We are unable to provide an estimate of the terrestrial nutrient enrichment benefits 

associated with the alternative standard level combinations due to data, time, and resource 

limitations. Methods are not yet available to allow estimation of changes in ecosystem services 

due to nitrogen deposition.

6.7.2.3 Vegetation Effects Associated with Gaseous Sulfur Dioxide

Uptake of gaseous sulfur dioxide in a plant canopy is a complex process involving 

adsorption to surfaces (leaves, stems, and soil) and absorption into leaves. SO2 penetrates into 

leaves through to the stomata, although there is evidence for limited pathways via the cuticle 

(U.S. EPA, 2008c). Pollutants must be transported from the bulk air to the leaf boundary layer in 

order to get to the stomata. When the stomata are closed, as occurs under dark or drought 

conditions, resistance to gas uptake is very high and the plant has a very low degree of 

susceptibility to injury. In contrast, mosses and lichens do not have a protective cuticle barrier 

to gaseous pollutants or stomates and are generally more sensitive to gaseous sulfur and 

 43 These estimates reflect the total value of the service, not the marginal change in the value of the service as a 

result of the emission reductions achieved by this rule. 44 These estimates reflect the total value of the service, not the marginal change in the value of the service as a 

result of the emission reductions achieved by this rule.
6-58

nitrogen than vascular plants (U.S. EPA, 2008c). Acute foliar injury usually happens within hours 

of exposure, involves a rapid absorption of a toxic dose, and involves collapse or necrosis of 

plant tissues. Another type of visible injury is termed chronic injury and is usually a result of 

variable SO2 exposures over the growing season. Besides foliar injury, chronic exposure to low 

SO2 concentrations can result in reduced photosynthesis, growth, and yield of plants (U.S. EPA, 

2008c). These effects are cumulative over the season and are often not associated with visible 

foliar injury. As with foliar injury, these effects vary among species and growing environment. 

SO2 is also considered the primary factor causing the death of lichens in many urban and 

industrial areas (Hutchinson et al., 1996). The ISA for NOx/SOx—Ecological Criteria concluded 

that the evidence is sufficient to infer a causal relationship between SO2 injury to vegetation 

(U.S. EPA, 2008c).

6.7.2.4 Mercury-Related Benefits Associated with the Role of Sulfate in Mercury Methylation

Mercury is a persistent, bioaccumulative toxic metal that is emitted from in three forms: 

gaseous elemental Hg (Hg0

), oxidized Hg compounds (Hg+2), and particle-bound Hg (HgP). 

Methylmercury (MeHg) is formed by microbial action in the top layers of sediment and soils, 

after Hg has precipitated from the air and deposited into waterbodies or land. Once formed, 

MeHg is taken up by aquatic organisms and bioaccumulates up the aquatic food web. Larger 

predatory fish may have MeHg concentrations many times, typically on the order of one million 

times, that of the concentrations in the freshwater body in which they live.

The NOx SOx ISA—Ecological Criteria concluded that evidence is sufficient to infer a 

causal relationship between sulfur deposition and increased mercury methylation in wetlands 

and aquatic environments (U.S. EPA, 2008c). Specifically, there appears to be a relationship 

between SO4

2-

deposition and mercury methylation; however, the rate of mercury methylation 

varies according to several spatial and biogeochemical factors whose influence has not been 

fully quantified (see Figure 6-14). Therefore, the correlation between SO4

2-

deposition and 

MeHg could not be quantified for the purpose of interpolating the association across 

waterbodies or regions. Nevertheless, because changes in MeHg in ecosystems represent 

changes in significant human and ecological health risks, the association between sulfur and 

mercury cannot be neglected (U.S. EPA, 2008c).
 

6-59

Figure 6-14. Spatial and Biogeochemical Factors Influencing MeHg Production

As research evolves and the computational capacity of models expands to meet the 

complexity of mercury methylation processes in ecosystems, the role of interacting factors may 

be better parsed out to identify ecosystems or regions that are more likely to generate higher 

concentrations of MeHg. Figure 6-15 illustrates the type of current and forward-looking 

research being developed by the U.S. Geological Survey (USGS) to synthesize the contributing 

factors of mercury and to develop a map of sensitive watersheds. The mercury score 

referenced in Figure 6-15 is based on SO4

2- concentrations, acid neutralizing capacity (ANC), 

levels of dissolved organic carbon and pH, mercury species concentrations, and soil types to 

gauge the methylation sensitivity (Myers et al., 2007).
 

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Figure 6-15. Preliminary USGS Map of Mercury Methylation–Sensitive Watersheds

Source: Myers et al., 2007

Interdependent biogeochemical factors preclude the existence of simple sulfate-related 

mercury methylation models. It is clear that decreasing sulfate deposition is likely to result in 

decreased MeHg concentrations. Future research may allow for the characterization of a usable 

sulfate-MeHg response curve; however, no regional or classification calculation scale can be 

created at this time because of the number of confounding factors.

Decreases in SO4

2- deposition have already shown promising reductions in MeHg. 

Observed decreases in MeHg fish tissue concentrations have been linked to decreased 

acidification and declining SO4

2- and mercury deposition in Little Rock Lake, WI (Hrabik and 

Watras, 2002), and to decreased SO4

2- deposition in Isle Royale in Lake Superior, MI (Drevnick et 

al., 2007). Although the possibility exists that reductions in SO4

2- emissions could generate a 

pulse in MeHg production because of decreased sulfide inhibition in sulfate-saturated waters, 

this effect would likely involve a limited number of U.S. waters (Harmon et al., 2007). Also, 

because of the diffusion and outward flow of both mercury-sulfide complexes and SO4

2-, 

increased mercury methylation downstream may still occur in sulfate-enriched ecosystems with 

increased organic matter and/or downstream transport capabilities.
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Remediation of sediments heavily contaminated with mercury has yielded significant 

reductions of MeHg in biotic tissues. Establishing quantitative relations in biotic responses to 

MeHg levels as a result of changes in atmospheric mercury deposition, however, presents 

difficulties because direct associations can be confounded by all of the factors discussed in this 

section. Current research does suggest that the levels of MeHg and total mercury in ecosystems 

are positively correlated, so that reductions in mercury deposited into ecosystems would also 

eventually lead to reductions in MeHg in biotic tissues. Ultimately, an integrated approach that 

involves the reduction of both sulfur and mercury emissions may be most efficient because of 

the variability in ecosystem responses. Reducing SOX emissions could have a beneficial effect on 

levels of MeHg in many waters of the United States.

MeHg is the only form of mercury that biomagnifies in the food web. Concentrations of 

MeHg in fish are generally on the order of a million times the MeHg concentration in water. In 

addition to mercury deposition, key factors affecting MeHg production and accumulation in fish 

include the amount and forms of sulfur and carbon species present in a given waterbody. Thus, 

two adjoining water bodies receiving the same deposition can have significantly different fish 

mercury concentrations.

Methylmercury builds up more in some types of fish and shellfish than in others. The 

levels of methylmercury in high and shellfish vary widely depending on what they eat, how long 

they live, and how high they are in the food chain. Most fish, including ocean species and local 

freshwater fish, contain some methylmercury. In general, higher mercury concentrations are 

expected in top predators, which are often large fish relative to other species in a waterbody.

The ecosystem service most directly affected by sulfate-mediated mercury methylation 

is the provision of fish for consumption as a food source. This service is of particular importance 

to groups engaged in subsistence fishing, pregnant women and young children.

6.7.3 Ecosystem Benefits from Reductions in Mercury Emissions

Deposition of mercury to waterbodies can also have an impact on ecosystems and 

wildlife. Mercury contamination is present in all environmental media with aquatic systems 

experiencing the greatest exposures due to bioaccumulation. Bioaccumulation refers to the net 

uptake of a contaminant from all possible pathways and includes the accumulation that may 

occur by direct exposure to contaminated media as well as uptake from food.

Atmospheric mercury enters freshwater ecosystems by direct deposition and through 

runoff from terrestrial watersheds. Once mercury deposits, it may be converted to organic 
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methylmercury mediated primarily by sulfate-reducing bacteria. Methylation is enhanced in 

anaerobic and acidic environments, greatly increasing mercury toxicity and potential to 

bioaccumulate in aquatic foodwebs. A number of key biogeochemical controls influence the 

production of methylmercury in aquatic ecosystems. These include sulfur, pH, organic matter, 

iron, mercury “aging,” and bacteria type and activity (Munthe et al., 2007).

Wet and dry deposition of oxidized mercury is a dominant pathway for bringing mercury 

to terrestrial surfaces. In forest ecosystems, elemental mercury may also be absorbed by plants 

stomatally, incorporated by foliar tissues and released in litterfall (Ericksen et al., 2003). 

Mercury in throughfall, direct deposition in precipitation, and uptake of dissolved mercury by 

roots (Rea et al., 2002) are also important in mercury accumulation in terrestrial ecosystems.

Soils have significant capacity to store large quantities of atmospherically deposited 

mercury where it can leach into groundwater and surface waters. The risk of mercury exposure 

extends to insectivorous terrestrial species such as songbirds, bats, spiders, and amphibians 

that receive mercury deposition or from aquatic systems near the forest areas they inhabit 

(Bergeron et al., 2010a, b; Cristol et al., 2008; Rimmer et al., 2005; Wada et al., 2009 & 2010).

Numerous studies have generated field data on the levels of mercury in a variety of wild 

species. Many of the data from these environmental studies are anecdotal in nature rather than 

representative or statistically designed studies. The body of work examining the effects of these 

exposures is growing but still incomplete given the complexities of the natural world. A large

portion of the adverse effect research conducted to date has been carried out in the laboratory 

setting rather than in the wild; thus, conclusions about overarching ecosystem health and 

population effects are difficult to make at this time. In the sections that follow numerous 

effects have been identified at differing exposure levels.

6.7.3.1 Mercury Effects on Fish

A review of the literature on effects of mercury on fish (Crump and Trudeau, 2009) 

reports results for numerous species including trout, bass (large and smallmouth), northern 

pike, carp, walleye, salmon and others from laboratory and field studies. The effects studied are 

reproductive and include deficits in sperm and egg formation, histopathological changes in 

testes and ovaries, and disruption of reproductive hormone synthesis. These studies were 

conducted in areas from New York to Washington and while many were conducted by adding 

MeHg to water or diet many were conducted at current environmental levels. While we cannot 

determine at this time whether these reproductive deficits are affecting fish populations across 

the United States it should be noted that it is possible that over time reproductive deficits could 
6-63

have an effect on populations. Lower fish populations would conceivably impact the ecosystem 

services like recreational fishing derived from having healthy aquatic ecosystems quite apart 

from the effects of consumption advisories due to the human health effects of mercury.

6.7.3.2 Mercury Effects on Birds

In addition to effects on fish, mercury also affects avian species. In previous reports (U.S. 

EPA (1997); U.S. EPA (2005)), much of the focus has been on large piscivorous species in 

particular the common loon. The loon is most visible to the public during the summer breeding 

season on northern lakes and they have become an important symbol of wilderness in these 

areas (McIntyre and Barr, 1997). A multitude of loon watch, preservation, and protection 

groups have formed over the past few decades and have been instrumental in promoting 

conservation, education, monitoring, and research of breeding loons (McIntyre and Evers, 

2000; Evers, 2006). Significant adverse effects on breeding loons from mercury have been 

found to occur including behavioral (reduced nest-sitting), physiological (flight feather 

asymmetry) and reproductive (chicks fledged/territorial pair) effects (Evers, 2008). Additionally 

Evers, et al (2008) report that they believe that the weight of evidence indicates that 

population-level effects occur in parts of Maine and New Hampshire, and potentially in broad 

areas of the loon’s range.

Recently attention has turned to other piscivorous species such as the white ibis, and 

great snowy egret. While considered to be fish-eating generally these wading birds have a very 

wide diet including crayfish, crabs, snails, insects and frogs. These species are experiencing a 

range of adverse effects due to exposure to mercury. The white ibis has been observed to have 

decreased foraging efficiency (Adams and Frederick, 2008). Additionally ibises have been shown 

to exhibit decreased reproductive success and altered pair behavior (Frederick and Jayasena, 

2010). These effects include significantly more unproductive nests, male/male pairing, reduced 

courtship behavior (head bobbing and pair bowing) and lower nestling production by exposed 

males. In this study, a worst-case scenario suggested by the results could involve up to a 50% 

reduction in fledglings due to MeHg in diet. These estimates may be conservative if male/male 

pairing in the wild it could result in a shortage of partners for females and the effect of 

homosexual breeding would be magnified. In egrets, mercury has been implicated in the 

decline of the species in south Florida (Sepulveda, et al., 1999) and Hoffman (2010) has shown 

that egrets show liver and possibly kidney effects. While ibises and egrets are most abundant in 

coastal areas and these studies were conducted in south Florida and Nevada the ranges of 

ibises and egrets extend to a large portion of the United States. Ibis territory can range inland 
6-64

to Oklahoma, Arkansas and Tennessee. Egret range covers virtually the entire United States 

except the mountain west.

Insectivorous birds have also been shown to suffer adverse effects due to mercury 

exposure. These songbirds such as Bicknell’s thrush, tree swallows and the great tit have shown 

reduced reproduction, survival, and changes in singing behavior. Exposed tree swallows 

produced fewer fledglings (Brasso, 2008), lower survival (Hallinger, 2010) and had 

compromised immune competence (Hawley, 2009). The great tit has exhibited reduced singing 

behavior and smaller song repertoire in an area of high contamination in the vicinity of a 

metallurgic smelter in Flanders (Gorissen, 2005).

6.7.3.3 Mercury Effects on Mammals

In mammals, adverse effects have been observed in mink and river otter, both fish 

eating species. For otter from Maine and Vermont maximum concentrations on Hg in fur nearly 

equal or exceed a concentration associated with mortality and concentration in liver for mink in 

Massachusetts/Connecticut and the levels in fur from mink in Maine exceed concentrations 

associated with acute mortality (Yates, 2005). Adverse sublethal effects may be associated with 

lower Hg concentrations and consequently be more widespread than potential acute effects. 

These effects may include increased activity, poorer maze performance, abnormal startle reflex, 

and impaired escape and avoidance behavior (Scheuhammer et al., 2007).

6.7.3.4 Mercury Ecological Conclusions

The studies cited here provide a glimpse of the scope of mercury effects on wildlife 

particularly reproductive and survival effects. These effects range across species from fish to 

mammals and spatially across a wide area of the United States. The literature is far from 

complete however. Much more research is required to establish a link between the ecological 

effects on wildlife and the effect on ecosystem services (services that the environment provides 

to people) for example recreational fishing, bird watching and wildlife viewing. EPA is not, 

however, currently able to quantify or monetize the benefits of reducing mercury exposures 

affecting provision of ecosystem services.

6.7.4 Vegetation Benefits from Reductions in Ambient Ozone

Control strategies that include emission reductions of NOx would affect ambient ozone 

concentrations. Ozone causes discernible injury to a wide array of vegetation (U.S. EPA, 2006a; 

Fox and Mickler, 1996). Air pollution can affect the environment and affect ecological systems, 

leading to changes in the ecological community and influencing the diversity, health, and vigor 
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of individual species (U.S. EPA, 2006a). In terms of forest productivity and ecosystem diversity, 

ozone may be the pollutant with the greatest potential for regional-scale forest impacts (U.S. 

EPA, 2006a). Studies have demonstrated repeatedly that ozone concentrations commonly 

observed in polluted areas can have substantial impacts on plant function (De Steiguer et al., 

1990; Pye, 1988).

When ozone is present in the air, it can enter the leaves of plants, where it can cause 

significant cellular damage. Like carbon dioxide (CO2) and other gaseous substances, ozone 

enters plant tissues primarily through the stomata in leaves in a process called “uptake” 

(Winner and Atkinson, 1986). Once sufficient levels of ozone (a highly reactive substance), or its 

reaction products, reaches the interior of plant cells, it can inhibit or damage essential cellular 

components and functions, including enzyme activities, lipids, and cellular membranes, 

disrupting the plant’s osmotic (i.e., water) balance and energy utilization patterns (U.S. EPA, 

2006a; Tingey and Taylor, 1982). With fewer resources available, the plant reallocates existing 

resources away from root growth and storage, above ground growth or yield, and reproductive 

processes, toward leaf repair and maintenance, leading to reduced growth and/or 

reproduction. Studies have shown that plants stressed in these ways may exhibit a general loss 

of vigor, which can lead to secondary impacts that modify plants’ responses to other 

environmental factors. Specifically, plants may become more sensitive to other air pollutants, 

or more susceptible to disease, pest infestation, harsh weather (e.g., drought, frost) and other 

environmental stresses, which can all produce a loss in plant vigor in ozone-sensitive species 

that over time may lead to premature plant death. Furthermore, there is evidence that ozone 

can interfere with the formation of mycorrhiza, essential symbiotic fungi associated with the 

roots of most terrestrial plants, by reducing the amount of carbon available for transfer from 

the host to the symbiont (U.S. EPA, 2006a).

This ozone damage may or may not be accompanied by visible injury on leaves, and 

likewise, visible foliar injury may or may not be a symptom of the other types of plant damage 

described above. Foliar injury is usually the first visible sign of injury to plants from ozone 

exposure and indicates impaired physiological processes in the leaves (Grulke, 2003). When 

visible injury is present, it is commonly manifested as chlorotic or necrotic spots, and/or 

increased leaf senescence (accelerated leaf aging). Visible foliar injury reduces the aesthetic 

value of ornamental vegetation and trees in urban landscapes and negatively affects scenic 

vistas in protected natural areas.

Ozone can produce both acute and chronic injury in sensitive species depending on the 

concentration level and the duration of the exposure. Ozone effects also tend to accumulate 
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over the growing season of the plant, so that even lower concentrations experienced for a 

longer duration have the potential to create chronic stress on sensitive vegetation. Not all 

plants, however, are equally sensitive to ozone. Much of the variation in sensitivity between 

individual plants or whole species is related to the plant’s ability to regulate the extent of gas 

exchange via leaf stomata (e.g., avoidance of ozone uptake through closure of stomata) and the 

relative ability of species to detoxify ozone-generated reactive oxygen free radicals (U.S. EPA, 

2006a; Winner, 1994). After injuries have occurred, plants may be capable of repairing the 

damage to a limited extent (U.S. EPA, 2006a). Because of the differing sensitivities among 

plants to ozone, ozone pollution can also exert a selective pressure that leads to changes in 

plant community composition. Given the range of plant sensitivities and the fact that numerous 

other environmental factors modify plant uptake and response to ozone, it is not possible to 

identify threshold values above which ozone is consistently toxic for all plants.

Because plants are at the base of the food web in many ecosystems, changes to the 

plant community can affect associated organisms and ecosystems (including the suitability of 

habitats that support threatened or endangered species and below ground organisms living in 

the root zone). Ozone impacts at the community and ecosystem level vary widely depending 

upon numerous factors, including concentration and temporal variation of tropospheric ozone, 

species composition, soil properties and climatic factors (U.S. EPA, 2006a). In most instances, 

responses to chronic or recurrent exposure in forested ecosystems are subtle and not 

observable for many years. These injuries can cause stand-level forest decline in sensitive 

ecosystems (U.S. EPA, 2006a, McBride et al., 1985; Miller et al., 1982). It is not yet possible to 

predict ecosystem responses to ozone with certainty; however, considerable knowledge of 

potential ecosystem responses is available through long-term observations in highly damaged 

forests in the U.S. (U.S. EPA, 2006a).

6.7.4.1 Ozone Effects on Forests

Air pollution can affect the environment and affect ecological systems, leading to 

changes in the ecological community and influencing the diversity, health, and vigor of 

individual species (U.S. EPA, 2006a). Ozone has been shown in numerous studies to have a 

strong effect on the health of many plants, including a variety of commercial and ecologically 

important forest tree species throughout the United States (U.S. EPA, 2007b).

In the U.S., this data comes from the U.S. Department of Agriculture (USDA) Forest 

Service Forest Inventory and Analysis (FIA) program. As part of its Phase 3 program (formerly 

known as Forest Health Monitoring), FIA looks for visible foliar injury of ozone-sensitive forest 

plant species at each ground monitoring site across the country (excluding woodlots and urban 
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trees) that meets certain minimum criteria. Because ozone injury is cumulative over the course 

of the growing season, examinations are conducted in July and August, when ozone 

concentrations and associated injury are typically highest.

Monitoring of ozone injury to plants by the U.S. Forest Service has expanded over the 

last 15 years from monitoring sites in 10 states in 1994 to nearly 1,000 monitoring sites in 41 

states in 2002. Since 2002, the monitoring program has further expanded to 1,130 monitoring 

sites in 45 states. Figure 6-16 shows the results of this monitoring program for the year 2002 

broken down by U.S. EPA Regions.45 Figure 6-17 identifies the counties that were included in 

Figure 6-16, and provides the county-level data regarding the presence or absence of ozonerelated injury. As shown in Figure 6-16, large geographic areas of EPA Regions 6, 8, and 10 were 

not included in the assessment. Ozone damage to forest plants is classified using a subjective 

five-category biosite index based on expert opinion, but designed to be equivalent from site to 

site. Ranges of biosite values translate to no injury, low or moderate foliar injury (visible foliar 

injury to highly sensitive or moderately sensitive plants, respectively), and high or severe foliar 

injury, which would be expected to result in tree-level or ecosystem-level responses, 

respectively (U.S. EPA, 2006a; Coulston, 2004). The highest percentages of observed high and 

severe foliar injury, which are most likely to be associated with tree or ecosystem-level 

responses, are primarily found in the Mid-Atlantic and Southeast regions. While the assessment 

showed considerable regional variation in ozone injury, this assessment targeted different 

ozone-sensitive species in different parts of the country with varying ozone sensitivity, which 

contributes to the apparent regional differences. It is important to note that ozone can have 

other, more significant impacts on forest plants (e.g., reduced biomass growth in trees) prior to 

showing signs of visible foliar injury (U.S. EPA, 2006a).

Assessing the impact of ground-level ozone on forests in the U.S. involves understanding 

the risks to sensitive tree species from ambient ozone concentrations and accounting for the 

prevalence of those species within the forest. As a way to quantify the risks to particular plants 

from ground-level ozone, scientists have developed ozone-exposure/tree-response functions by 

exposing tree seedlings to different ozone levels and measuring reductions in growth as 

“biomass loss.” Typically, seedlings are used because they are easy to manipulate and measure 

their growth loss from ozone pollution. The mechanisms of susceptibility to ozone within the 

leaves of seedlings and mature trees are identical, and the decreases predicted using the 

seedlings should be related to the decrease in overall plant fitness for mature trees, but the

 45 The data are based on averages of all observations collected in 2002, which is the last year for which data are 

publicly available. For more information, please consult EPA’s 2008 Report on the Environment (U.S. EPA, 

2008b).
 

6-68

c

Degree of Injury: These categories reflect a subjective index based on expert opinion. Ozone can have other, 

more significant impacts on forest plants (e.g., reduced biomass growth in trees) prior to showing signs of visible 

foliar injury.

Figure 6-16. Visible Foliar Injury to Forest Plants from Ozone in U.S. by EPA Regionsa,b,c
 

6-69

Figure 6-17. Presence and Absence of Visible Foliar Injury, as Measured by U.S. Forest 

Service, 2002

Source: U.S. EPA, 2007b

magnitude of the effect may be higher or lower depending on the tree species (Chappelka and 

Samuelson, 1998). In areas where certain ozone-sensitive species dominate the forest 

community, the biomass loss from ozone can be significant. Experts have identified 2% annual 

biomass loss as a level of concern, which would cause long term ecological harm as the shortterm negative effects on seedlings compound to affect long-term forest health (Heck and 

Cowling, 1997).

Ozone damage to the plants including the trees and understory in a forest can affect the 

ability of the forest to sustain suitable habitat for associated species particularly threatened and 

endangered species that have existence value—a nonuse ecosystem service—for the public. 

Similarly, damage to trees and the loss of biomass can affect the forest’s provisioning services 

in the form of timber for various commercial uses. In addition, ozone can cause discoloration of 

leaves and more rapid senescence (early shedding of leaves), which could negatively affect fallcolor tourism because the fall foliage would be less available or less attractive. Beyond the 

aesthetic damage to fall color vistas, forests provide the public with many other recreational 

and educational services that may be affected by reduced forest health including hiking, wildlife 
6-70

viewing (including bird watching), camping, picnicking, and hunting. Another potential effect of 

biomass loss in forests is the subsequent loss of climate regulation service in the form of 

reduced ability to sequester carbon and alteration of hydrologic cycles.

Some of the common tree species in the United States that are sensitive to ozone are 

black cherry (Prunus serotina), tulip-poplar (Liriodendron tulipifera), and eastern white pine 

(Pinus strobus). Ozone-exposure/tree-response functions have been developed for each of 

these tree species, as well as for aspen (Populus tremuliodes), and ponderosa pine (Pinus 

ponderosa) (U.S. EPA, 2007b).

6.7.4.2 Ozone Effects on Crops

Laboratory and field experiments have shown reductions in yields for agronomic crops 

exposed to ozone, including vegetables (e.g., lettuce) and field crops (e.g., cotton and wheat). 

Damage to crops from ozone exposures includes yield losses (i.e., in terms of weight, number, 

or size of the plant part that is harvested), as well as changes in crop quality (i.e., physical 

appearance, chemical composition, or the ability to withstand storage) (U.S. EPA, 2007b). The 

most extensive field experiments, conducted under the National Crop Loss Assessment 

Network (NCLAN) examined 15 species and numerous cultivars. The NCLAN results show that 

“several economically important crop species are sensitive to ozone levels typical of those 

found in the United States” (U.S. EPA, 2006a). In addition, economic studies have shown 

reduced economic benefits as a result of predicted reductions in crop yields, directly affecting 

the amount and quality of the provisioning service provided by these crops, associated with 

observed ozone levels (Kopp et al., 1985; Adams et al., 1986; Adams et al., 1989). In addition, 

visible foliar injury by itself can reduce the market value of certain leafy crops (such as spinach, 

lettuce). According to the Ozone Staff Paper, there has been no evidence that crops are 

becoming more tolerant of ozone (U.S. EPA, 2007b). Using the Agriculture Simulation Model 

(AGSIM) (Taylor, 1994) to calculate the agricultural benefits of reductions in ozone exposure, 

U.S. EPA estimated that attaining a W126 standard of 13 ppm-hr would produce monetized 

benefits of approximately $400 million to $620 million in 2006 (inflated to 2006 dollars) (U.S. 

EPA, 2007b).46

 46 These estimates illustrate the value of vegetation effects from a substantial reduction of ozone concentrations, 

not the marginal change in ozone concentrations anticipated a result of the emission reductions achieved by 

this rule.
6-71

6.7.4.3 Ozone Effects on Ornamental Plants

Urban ornamental plants are an additional vegetation category likely to experience 

some degree of negative effects associated with exposure to ambient ozone levels. Several 

ornamental species have been listed as sensitive to ozone (Abt Associates, 1995). Because 

ozone causes visible foliar injury, the aesthetic value of ornamental plants (such as petunia, 

geranium, and poinsettia) in urban landscapes would be reduced (U.S. EPA, 2007b). Sensitive 

ornamental species would require more frequent replacement and/or increased maintenance 

(fertilizer or pesticide application) to maintain the desired appearance because of exposure to 

ambient ozone (U.S. EPA, 2007b). In addition, many businesses rely on healthy-looking 

vegetation for their livelihoods (e.g., horticulturalists, landscapers, Christmas tree growers, 

farmers of leafy crops, etc.). The ornamental landscaping industry is a multi-billion dollar 

industry that affects both private property owners/tenants and governmental units responsible 

for public areas (Abt Associates, 1995). Preliminary data from the 2007 Economic Census 

indicate that the landscaping services industry, which is primarily engaged in providing 

landscape care and maintenance services and installing trees, shrubs, plants, lawns, or gardens, 

was valued at $53 billion (U.S. Census Bureau, 2010). Therefore, urban ornamentals represent a 

potentially large unquantified benefit category. This aesthetic damage may affect the 

enjoyment of urban parks by the public and homeowners’ enjoyment of their landscaping and 

gardening activities. In addition, homeowners may experience a reduction in home value or a 

home may linger on the market longer due to decreased aesthetic appeal. In the absence of 

adequate exposure-response functions and economic damage functions for the potential range 

of effects relevant to ornamental plants, we cannot conduct a quantitative analysis to estimate 

these effects.

We are unable to provide an estimate of the ozone crop benefits associated with the 

alternative standard level combinations due to data, time, and resource limitations.

6.8 References

Abt Associates, Inc. 1995. Urban ornamental plants: sensitivity to ozone and potential economic 

losses. U.S. EPA, Office of Air Quality Planning and Standards, Research Triangle Park. 

Under contract to RADIAN Corporation, contract no. 68-D3-0033, WA no. 6. pp. 9-10. 

Available on the Internet at 

<http://www.epa.gov/ttn/ecas/regdata/Benefits/background/abt1995.pdf>.
6-72

Abt Associates, Inc. 2001. Assessing Public Opinions on Visibility Impairment due to Air 

Pollution: Summary Report. Prepared for EPA Office of Air Quality Planning and 

Standards; funded under EPA Contract No. 68-D-98-001. Abt Associates Inc., Bethesda, 

MD. January. Available on the Internet at 

<http://www.epa.gov/ttncaaa1/t1/reports/vis_rpt_final.pdf>.

Adams, Evan M., and Frederick, Peter C. 2008. “Effects of methylmercury and spatial complexity 

on foraging behavior and foraging efficiency in juvenile white ibises (Eudocimus albus).” 

Environmental Toxicology and Chemistry. Vol 27, No. 8.

Adams, R. M., Glyer, J. D., Johnson, S. L., McCarl, B. A. 1989. “A reassessment of the economic 

effects of ozone on U.S. agriculture.” Journal of the Air Pollution Control Association, 39, 

960-968.

Adams, R. M., Hamilton, S. A., McCarl, B. A. 1986. “The benefits of pollution control: the case of 

ozone and U.S. agriculture.” American Journal of Agricultural Economics, 34, 3-19.

Anselin, L., Le Gallo, J. 2006. “Interpolation of air quality measures in hedonic house price 

models: Spatial aspects.” Spatial Economic Analysis 1: 31–52

Anselin, L., Lozano-Gracia, N. 2009. “Errors in variables and spatial effects in hedonic house 

price models of ambient air quality.” Empirical Economics 34: 5–34.

Arrow, K.J., et al. 1993. Report of the NOAA Panel on Contingent Valuation. Federal Register. 

Volume 58, Number 10. Pages 4601 to 4614. Available on the Internet at 

<http://www.darp.noaa.gov/library/pdf/cvblue.pdf>.

Arzavus K.M., Dickhut R.M., and Canuel E.A. 2001. “Fate of Atmospherically Deposited 

Polycyclic Aromatic Hydrocarbons (PAHs) in Chesapeake Bay.” Environmental Science & 

Technology, 35, 2178-2183.

Bond, T.C., and Sun H.L. (2005) Can reducing BC emissions counteract global warming? 

Environmental Science & Technology 39 (16).

Banzhaf, S., D. Burtraw, D. Evans, and A. Krupnick. 2006. “Valuation of Natural Resource 

Improvements in the Adirondacks.” Land Economics 82:445-464.

Bayer, P., Keohane, N.O. and Timmins, C. 2009. “Migration and hedonic valuation: the case of 

air quality,” Journal of Environmental Economics and Management, 58 (2009) 1–14.

BBC Research & Consulting. 2003. Phoenix Area Visibility Survey. Draft Report. Available on the 

Internet at <http://www.azdeq.gov/environ/air/download/vis_021903f.pdf>.

Bergeron, CM., Bodinof, CM., Unrine, JM., Hopkins, WA. 2010a. “Mercury accumulation along a 

contamination gradient and nondestructive indices of bioaccumulation in amphibians.” 

Environmental Toxicology and Chemistry 29(4), 980-988.
6-73

Bergeron, CM., Bodinof, CM., Unrine, JM., Hopkins, WA. 2010b. “Bioaccumulation and maternal 

transfer of mercury and selenium in amphibians.” Environmental Toxicology and 

Chemistry 29(4), 989-997.

Beron KJ, Murdoch J, Thayer M. 2001. “The benefits of visibility improvement: New evidence 

from Los Angeles metropolitan area.” J Real Estate Finance Econ 22(2–3):319–337.

Beron KJ, Hanson Y, Murdoch JC, Thayer MA. 2004. “Hedonic price functions and spatial 

dependence: implications for the demand for urban air quality.” In: Anselin L, Florax RJ, 

Rey SJ (eds) Advances in spatial econometrics: methodology, tools and applications. 

Springer-Verlag, Berlin, pp 267–281.

Brasso, Rebecka L., and Cristol, Daniel A. 2008. “Effects of mercury exposure in the reproductive 

success of tree swallows (Tachycineta bicolor).” Ecotoxicology. 17:133-141.

Brookshire, D.S., R.C. d’Arge, W.D. Schulze and M.A. Thayer. 1979. Methods Development for 

Assessing Tradeoffs in Environmental Management, Vol. II: Experiments in Valuing NonMarket Goods: A Case Study of Alternative Benefit Measures of Air Pollution Control in 

the South Coast Air Basin of Southern California. Prepared for the U.S. Environmental 

Protection Agency, Office of Research and Development. Available on the Internet at 

<http://yosemite.epa.gov/ee/epa/eerm.nsf/vwAN/EE-0271B-1.pdf/$file/EE-0271B1.pdf>.

Brookshire, D.S., Thayer, M.A., Schulze, W.D. & D’Arge, R.C. 1982. “Valuing Public Goods: A 

Comparison of Survey and Hedonic Approaches.” The American Economic Review. 72(1): 

165-177.

Burgess, Neil M., and Meyer, Michael W. 2008. “Methylmercury exposure associated with 

reduced productivity in common loons.” Ecotoxicology. 17:83-91.

California State Parks. 2003. Public Opinions and Attitudes on Outdoor Recreation in California 

2002. California State Parks, Sacramento, California. December 2003. Available on the 

Internet at <http://parks.ca.gov/pages/795/files/poa2002final.pdf>.

Carson, R.T., R.C. Mitchell, and P.A. Rudd. 1990. “Valuing Air Quality Improvements: Simulating 

a Hedonic Pricing Equation in the Context of a Contingent Valuation Scenario.” In 

Visibility and Fine Particles, Transactions of an AWMA/EPA International Specialty 

Conference, C.V. Mathai, ed. Air and Waste Management Association, Pittsburgh. 

Available on the Internet at

<http://www.econ.ucsd.edu/~rcarson/papers/AirQuality.pdf>.

Chameides. W.L., Yu, H., Liu, S.C., Bergin, M., Zhou, X., Mearns, L., Wang, G., Kiang, C.S., Saylor, 

R.D., Luo, C. Huang, Y., Steiner, A., and Giorgi, F. 1999. “Case study of the effects of 

atmospheric aerosols and regional haze on agriculture: an opportunity to enhance crop 

yields in China through emission controls?” PNAS, 96: 13626-13633.
6-74

Chappelka, A.H., Samuelson, L.J. 1998. “Ambient ozone effects on forest trees of the eastern 

United States: a review.” New Phytologist, 139, 91-108.

Chay KY, Greenstone M. 2005. “Does air quality matter? evidence form the housing market.” J 

Polit Econ 113(2):376–424.

Chestnut, L.G. 1997. Methodology for Estimating Values for Changes in Visibility in National 

Parks. Prepared for Office of Policy, Planning and Evaluation, May. Available on the 

Internet at 

<http://www.epa.gov/ttn/ecas/regdata/Benefits/background/chestnut1997.pdf>.

Chestnut, L.G. and R. Dennis. 1997. “Economic Benefits of Improvements in Visibility: Acid Rain 

Provisions of the 1990 Clean Air Act Amendments.” Journal of Air and Waste 

Management Association 47: 395-402.

Chestnut, L.G., and R.D. Rowe. 1990a. “New National Park Visibility Value Estimates.” In 

Visibility and Fine Particles, Transactions of an AWMA/EPA International Specialty 

Conference, C.V. Mathai, ed. Air and Waste Management Association, Pittsburgh.

Chestnut, L.G. and R.D. Rowe. 1990b. Preservation Values for Visibility Protection at the 

National Parks. Prepared for U.S. Environmental Protection Agency, Office of Air Quality 

Planning and Standards, and National Park Service, Air Quality Management Division. 

Available on the Internet at 

<http://www.google.com/url?sa=t&source=web&cd=2&ved=0CBkQFjAB&url=http%3A

%2F%2Fyosemite.epa.gov%2Fee%2Fepa%2Feerm.nsf%2FvwAN%2FEE-0405-

01.pdf%2F%24file%2FEE-0405-

01.pdf&rct=j&q=%22Preservation%20Values%20for%20Visibility%20Protection%20at%2

0the%20National%20Parks%22&ei=IAH4TOOlFM3MswaHsozaCA&usg=AFQjCNFcUMZPo

2v9nNOwLVJneZkGSJSYpg&cad=rja>.

Chestnut, L.G. and R.D. Rowe. 1990c. “Economic Valuation of Changes in Visibility: A State of 

the Science Assessment for NAPAP.” Section B5 in Irving, Patricia M., e.d., 1991. Acid 

Deposition: State of Science and Technology, Volume IV, Control Technologies, Future 

Emissions, and Effects Valuation, The U.S. National Acid Precipitation Assessment 

Program, Report 27, page 27–153.

Chestnut, L.G., R.D. Rowe and J. Murdoch. 1986. Review of ‘Establishing and Valuing the Effects 

of Improved Visibility in Eastern United States.’ Prepared for the U.S. Environmental 

Protection Agency. October. Available on the Internet at 

<http://www.epa.gov/ttn/ecas/regdata/Benefits/background/chestnut1986.pdf>.
6-75

Cordell, H.K., C.J. Betz, G. Green, and M. Owens. 2005. Off-Highway Vehicle Recreation in the 

United States, Regions and States: A National Report from the National Survey on 

Recreation and the Environment (NSRE). Prepared for the U.S. Department of 

Agriculture Forest Service, Southern Research Station, National OHV Policy and 

Implementation Teams, Athens, GA. Available on the Internet at 

<http://www.fs.fed.us/recreation/programs/ohv/OHV_final_report.pdf>

Cordell, K., B. Leeworthy, G.T. Green, C. Betz, B. Stephens. 2008. The National Survey on 

Recreation & the Environment. Research Work Unit 4953. Pioneering Research on 

Changing Forest Values in the South and Nation, U.S. Department of Agriculture Forest 

Service, Southern Research Station, Athens, GA. Available on the Internet at 

<http://www.srs.fs.fed.us/trends>.

Cotrufo, M.F., De Santo A.V., Alfani A., Bartoli G., De Cristofaro A. 1995. “Effects of urban heavy 

metal pollution on organic matter decomposition in Quercus ilex L. Woods.” 

Environmental Pollution, 89(1), 81-87.

Coulston, J.W., Riitters, K.H., Smith, G.C. 2004. “A preliminary assessment of the Montreal 

process indicators of air pollution for the United States.” Environmental Monitoring and 

Assessment, 95, 57-74.

Cristol D. A., Brasso R. L., Condon A. M., Fovargue R. E., Friedman S. L., Hallinger K. K., Monroe 

A. P., White A. E. 2008. “The movement of aquatic mercury through terrestrial food 

webs.” Science 320, 335–335.

Cropper, Maureen. 2000. “Has Economic Research Answered the Needs of Environmental 

Policy?” Journal of Environmental Economics and Management 39, 328-350.

Crump, Kate L., and Trudeau, Vance L. 2009. “Mercury-induced reproductive impairment in 

fish.” Environmental Toxicology and Chemistry. Vol. 28, No. 5.

De Steiguer, J., Pye, J., Love, C. 1990. “Air Pollution Damage to U.S. Forests.” Journal of Forestry, 

88(8), 17-22.

DeBell, L. J.; Gebhart, K. A.; Hand, J. L.; Malm, W. C.; Pitchford, M. L.; Schichtel, B. A.; White, W. 

H. 2006. Spatial and Seasonal Patterns and Temporal Variability of Haze and its 

Constituents in the United States, Report IV; Cooperative Institute for Research in the 

Atmosphere, Nov; ISSN 0737-5352-74. Available on the Internet at 

<http://vista.cira.colostate.edu/improve/Publications/Reports/2006/2006.htm>.

DeHayes, D.H., P.G. Schaberg, G.J. Hawley, and G.R. Strimbeck. 1999. “Acid rain impacts on 

calcium nutrition and forest health.” Bioscience 49(10):789–800.
6-76

Ely, D.W., Leary, J.T., Stewart, T.R., Ross, D.M. 1991. “The Establishment of the Denver Visibility 

Standard.” Presented at Air and Waste Management Association 84th Annual Meeting, 

June 16-21, Paper 91-48.4, 17pp. Available on the Internet at 

<http://www.albany.edu/cpr/stewart/Papers/T0210-ElyDenverVisStandard1991cap.pdf>.

Ericksen, J. A., Gustin, M. S., Schorran, D. E., Johnson, D. W., Lindberg, S. E., & Coleman, J. S. 

(2003). “Accumulation of atmospheric mercury in forest foliage.” Atmospheric 

Environment 37(12), 1613-1622.

Evers, D.C., 2006. Status assessment and conservation plan for the common loon (Gavia immer) 

in North America. U.S. Fish and Wildlife Service, Hadley, MA, USA.

Evers, David C., Savoy, Lucas J., DeSorbo, Christopher R., Yates, David E., Hanson, William, 

Taylor, Kate M., Siegel, Lori S., Cooley, John H. Jr., Bank, Michael S., Major, Andrew, 

Munney, Kenneth, Mower, Barry F., Vogel, Harry S., Schoch, Nina, Pokras, Mark, 

Goodale, Morgan W., Fair, Jeff. 2008. “Adverse effects from environmental mercury 

loads on breeding common loons.” Ecotoxicology. 17:69-81.

Fox, S., Mickler, R. A. (Eds.). 1996. Impact of Air Pollutants on Southern Pine Forests, Ecological 

Studies. (Vol. 118, 513 pp.) New York: Springer-Verlag.

Frederick, Peter, and Jayasena, Nilmini. 2010. “Altered pairing behavior and reproductive 

success in white ibises exposed to environmentally relevant concentrations of 

methylmercury.” Proceedings of the Royal Society B. doi: 10-1098.

Gorissen, Leen, Snoeijs, Tinne, Van Duyse, Els, and Eens, Marcel. 2005. “Heavy metal pollution 

affects dawn singing behavior in a small passerine bird.” Oecologia. 145: 540-509.

Grantz DA; Garner JHB; Johnson DW. 2003. “Ecological effects of particulate matter.” Environ 

Int, 29: 213-239.

Grosclaude P. and N. Soguel. 1994. “Valuing damage to historic buildings using a contingent 

market: a case study of road traffic externalities,” Journal of Environmental Planning and 

Management 37 (1994) (3), pp. 279–287.

Grulke, N.E. 2003. “The physiological basis of ozone injury assessment attributes in Sierran 

conifers.” In A. Bytnerowicz, M.J. Arbaugh, & R. Alonso (Eds.), Ozone air pollution in the 

Sierra Nevada: Distribution and effects on forests. (pp. 55-81). New York, NY: Elsevier 

Science, Ltd.

Hadley O.L., Corrigan C.E., Kirchstetter T.W., Cliff S.S., and Ramanathan V. (2010) Measured 

black carbon deposition on the Sierra Nevada snow pack and implication for snow pack 

retreat. Atmos. Chem. Phys. Discuss. 10, 10463-10485 

(doi:10.5194/acpd-10-10463-2010).
6-77

Hageman KJ; Simonich SL; Campbell DH; Wilson GR; Landers DH. 2006. “Atmospheric deposition 

of current-use and historic-use pesticides in snow at national parks in the western 

United States.” Environ Sci Technol, 40: 3174-3180

Hallinger, Kelly K., Cornell, Kerri L., Brasso, Rebecka L., and Cristol, Daniel A. 2010. “Mercury 

exposure and survival in free-living tree swallows (Tachycineta bicolor).” Ecotoxicology. 

Doi: 10.1007/s10646-010-0554-4.

Hawley, Dana M., Hallinger, Kelly K., Cristol, Daniel A. 2009. “Compromised immune 

competence in free-living tree swallows exposed to mercury.” Ecotoxicology. 18:499-

503.

Heck, W.W. &Cowling E.B. 1997. “The need for a long term cumulative secondary ozone 

standard—an ecological perspective.” Environmental Management, January, 23-33.

Hoffman, David J., Henny, Charles J., Hill, Elwood F., Grover, Robert A., Kaiser, James L., 

Stebbins, Katherine R. 2009. “Mercury and drought along the lower Carson River, 

Nevada: III. Effects on blood and organ biochemistry and histopathology of snowy egrets 

and black-crowned night-herons on Lahontan Reservoir, 2002–2006.” Journal of 

Toxicology and Environmental Health, Part A. 72: 20, 1223-1241.

Hutchison, R., and C.E. Kraft. 1994. “Hmong Fishing Activity and Fish Consumption.” Journal of 

Great Lakes Research 20(2):471–487.

Intergovernmental Panel on Climate Change 4th Assessment Report: Climate Change 2007 

Synthesis Report Summary for Policy Makers Pachauri, R.K. and Reisinger, A. (Eds.). 

Available on the Internet at 

<http://ipcc.ch/publications_and_data/ar4/syr/en/spm.html>.

IMPROVE (Interagency Monitoring of Protected Visual Environments). 2010. 1992–2008 data 

from the IMPROVE network based on the “New IMPROVE algorithm” (updated 

November, 2008). Available on the Internet at 

<http://vista.cira.colostate.edu/improve/Data/IMPROVE/summary_data.htm.>

Irving, P.M., e.d. 1991. Acid Deposition: State of Science and Technology, Volume III, Terrestrial, 

Materials, Health, and Visibility Effects, The U.S. National Acid Precipitation Assessment 

Program, Chapter 24, page 24–76.

Joslin, J.D., Kelly, J.M., and van Miegroet, H. 1992. “Soil chemistry and nutrition of North 

American spruce-fir stands: evidence for recent change. “ Journal of Environmental 

Quality, 21, 12-30.
6-78

Kaval, P., and J. Loomis. 2003. Updated Outdoor Recreation Use Values With Emphasis On 

National Park Recreation. Final Report October 2003, under Cooperative Agreement CA 

1200-99-009, Project number IMDE-02-0070. Available on the Internet at 

<http://www.mngt.waikato.ac.nz/departments/staff/pkaval/Kaval%26LoomisNPSRepor

t10-03.pdf>.

Kim, CW, Phipps, T, and Anselin L. 2003. “Measuring the benefits of air quality improvement: a 

spatial hedonic approach.” J Environ Econ Manage 45:24–39.

Koch, D., Bond, T.C., Streets D., and Unger N. (2007) Linking future aerosol radiative forcing to 

shifts in source activities. Geophys. Res. Lett. 34 (L05821), AGU 

(doi:10.1029/2006GL028360, 2007). Available on the Internet at 

<http://dx.doi.org/10.1029/2006GL028360>.

Koch D., Bond T.C., Streets D., Unger N., and van der Werf G.R. (2007) Global impacts of 

aerosols from particular source regions and sectors. Journal of Geophysical 

Research-Atmospheres 112 (D02205).

Kopp, R. J., Vaughn, W. J., Hazilla, M., Carson, R. 1985. “Implications of environmental policy for 

U.S. agriculture: the case of ambient ozone standards.” Journal of Environmental 

Management, 20, 321-331.

Kramer, A., T. Holmes, and M. Haefel. 2003. Contingent valuation of forest ecosystem 

protection. Pp. 303–320 in Forests in a Market Economy. Edited by E.O. Sills and K.L. Abt. 

Dordrecht, The Netherlands: Kluwer Academic Publishers.

Landers DH; Simonich SL; Jaffe DA; Geiser LH; Campbell DH; Schwindt AR; Schreck CB; Kent ML; 

Hafner WD; Taylor HE; Hageman KJ; Usenko S; Ackerman LK; Schrlau JE; Rose NL; Blett 

TF; Erway MM. (2008). The Fate, Transport and Ecological Impacts of Airborne 

Contaminants in Western National Parks (USA). EPA/600/R-07/138. U.S. Environmental 

Protection Agency, Office of Research and Development, NHEERL, Western Ecology 

Division. Corvallis, Oregon.

Leeworthy, V.R., and P.C. Wiley. 2001. Current Participation Patterns in Marine Recreation. 

Silver Spring, MD: U.S. Department of Commerce, National Oceanic and Atmospheric 

Administration, National Ocean Service, Special Projects. November. Available on the 

Internet at < http://www.naturetourismplanning.com/pdfs/NSRE_2.pdf>.

Leggett, C.G. and J.E. Neumann. 2004. Responding to SAB Council Comments on the May 2003 

Draft Analytical Plan for the Section 812 Second Prospective—Visibility Benefits.

Prepared for U.S. Environmental Protection Agency OPAR. Available on the Internet at 

<http://www.epa.gov/ttn/ecas/regdata/Benefits/background/leggettandneumann2004.

pdf>.
6-79

Leistritz, F. L., D. A. Bangsund, and N. M. Hodur. 2004. “Assessing the Economic Impact of 

Invasive Weeds: The Case of Leafy Spurge (Euphorbia esula).” Weed Technology

18:1392-1395.

Leitch, J. A, F. L Leistritz, and D. A Bangsund. 1996. “Economic effect of leafy spurge in the 

upper Great Plains: methods, models, and results.” Impact Assessment 14: 419–434.

Lipton, D. W. 1999. “Pfiesteria’s economic impact on seafood industry sales and recreational 

fishing, p. 35–38.” In B. L. Gardner and L. Koch (ed.), Proceedings of the Conference, 

Economics of Policy Options for Nutrient Management and Pfiesteria. Center for 

Agricultural and Natural Resource Policy, University of Maryland, College Park.

Loehman, E.T., D. Boldt, K. Chaikin. 1985. Measuring the Benefits of Air Quality Improvements

in the San Francisco Bay Area. From Methods Development for Environmental Control 

Benefits Assessment, Volume IV. Prepared for the U.S. Environmental Protection 

Agency, Office of Policy, Planning and Evaluation, September. Grant #R805059-01-0 

Available on the Internet at 

<http://yosemite.epa.gov/ee/epa/eerm.nsf/vwGA/e85705387833398f8525644d0053bd

d0!OpenDocument#_Section6>.

Loehman, E.T., S. Park, and D. Boldt. 1994. “Willingness to Pay for Gains and Losses in Visibility 

and Health.” Land Economics 70(4): 478-498.

Malm, WC. 1999. Introduction to visibility. Colorado State University, Fort Collins, CO, USA, 

1983, Revised edition, 1999. Available on the Internet at 

<vista.cira.colostate.edu/improve/Education/IntroToVisinstr.htm>.

McBride, J.R., Miller, P.R., Laven, R.D. 1985. “Effects of oxidant air pollutants on forest 

succession in the mixed conifer forest type of southern California.” In: Air Pollutants 

Effects on Forest Ecosystems, Symposium Proceedings, St. P, 1985, p. 157-167.

McClelland, G., W. Schulze, D. Waldman, J. Irwin, D. Schenk, T. Stewart, L. Deck and M. Thayer. 

1993. Valuing Eastern Visibility: A Field Test of the Contingent Valuation Method. 

Prepared for U.S. Environmental Protection Agency, Office of Policy, Planning and 

Evaluation. September. Available on the Internet at 

<http://yosemite.epa.gov/ee/epa/eerm.nsf/vwAN/EE-0008-1.pdf/$file/EE-0008-1.pdf >.

McIntyre, J.W., Barr, J.F. 1997. “Common Loon (Gavia immer)” in: Pool A, Gill F (eds.) The Birds 

of North America. Academy of Natural Sciences, Philadelphia, PA, 313

McIntrye, J.W., and Evers, D.C.,(eds). 2000. “Loons: old history and new finding.” Proceedings of 

a Symposium from the 1997 meeting, American Ornithologists’ Union. North American 

Loon Fund, 15 August 1997, Holderness, NH, USA.
6-80

Millennium Ecosystem Assessment Board (MEA). 2005. Ecosystems and Human Well-being: 

Synthesis. Washington, DC: World Resources Institute. Available on the Internet at 

<http://www.who.int/globalchange/ecosystems/ecosystems05/en/index.html>.

Miller, P.R., O.C. Taylor, R.G. Wilhour. 1982. Oxidant air pollution effects on a western 

coniferous forest ecosystem. Corvallis, OR: U.S. Environmental Protection Agency, 

Environmental Research Laboratory (EPA600-D-82-276).

Mitro, Matthew G., Evers, David C., Meyer, Michael W., and Piper, Walter H. 2008. “Common 

loon survival rates and mercury in New England and Wisconsin.” Journal of Wildlife 

Management 72(3): 665-673.

Munthe, J., Bodaly, R. A., Branfireun, B. A., Driscoll, C. T., Gilmour, C. C., Harris, R., et al. (2007). 

“Recovery of Mercury-Contaminated Fisheries.” Environmental Science & Technology

36(1), 33-44.

National Agricultural Statistics Service (NASS). 2008. Maple Syrup—June 12, 2008: Maple Syrup 

Production Up 30 Percent Nationwide. U.S. Department of Agriculture, National 

Agricultural Statistics Service, New England Agricultural Statistics, Concord, NH.

National Association of State Foresters (NASF). 2009. Quadrennial Fire Review 

2009.Washington, DC: NASF. Quadrennial Fire and Fuel Review Final Report 2009. 

National Wildfire Coordinating Group Executive Board. January.

National Oceanic and Atmospheric Administration (NOAA). 2007. Annual Commercial Landing 

Statistics. August. Available on the Internet at <http://www.st.nmfs.noaa.gov/ 

st1/commercial/landings/annual_landings.html>.

National Park Service (NPS). 1997. Statistical Abstract: 1997. Department of Interior, National 

Park Service Social Science Program, Public Use Statistics Office, Denver, Colorado. 

Available on the Internet at 

<http://www.nature.nps.gov/stats/abstracts/abst1997.pdf>.

National Park Service (NPS). 2008. Statistical Abstract: 2008. Department of Interior, National 

Park Service Social Science Program, Public Use Statistics Office, Denver, Colorado. 

Available on the Internet at 

<http://www.nature.nps.gov/stats/abstracts/abst2008.pdf>.

Neumann, J.E. and R.W. Patterson. 2009. Alternative Approach to Estimating Monetized 

Benefits of Residential Visibility for the Section 812 Second Prospective. Prepared for U.S. 

Environmental Protection Agency OAR/OPAR. Available on the Internet at 

<http://www.epa.gov/ttn/ecas/regdata/Benefits/background/neumannpaterson2009.p

df>.
6-81

Niklinska M., Laskowski R., Maryanski M. (1998). “Effect of heavy metals and storage time on 

two types of forest litter: basal respiration rate and exchangeable metals” 

Ecotoxicological Environmental Safety, 41, 8-18.

Office of Management and Budget (OMB). 2003. Circular A-4: Regulatory Analysis. Washington, 

DC. Available on the internet at <http://www.whitehouse.gov/omb/circulars/a004/a4.html>.

Painter, et al. 2007. “Impact of disturbed desert soils on duration of mountain snow cover.” 

Geophys. Res. Lett. 34, L12502.

Parrish ZD; White JC; Isleyen M; Gent MPN; Iannucci-Berger W; Eitzer BD; Kelsey JW; Mattina 

MI. 2006. “Accumulation of weathered polycyclic aromatic hydrocarbons (PAHs) by 

plant and earthworm species.” Chemosphere, 64: 609-618.

Patterson, R.W., J.E. Neumann, and C.G. Leggett. 2005. Recommended Residential Visibility 

Values for the Section 812 Second Prospective Analysis. Prepared for U.S. Environmental 

Protection Agency OPAR. Available on the Internet at 

<http://www.epa.gov/ttn/ecas/regdata/Benefits/background/patersonneumanleggett2

005.pdf>.

Peterson, D.E., M.S. Kanarek, M.A. Kuykendall, J.M. Diedrich, H.A. Anderson, P.L. Remington, 

and T.B. Sheffy. 1994. “Fish Consumption Patterns and Blood Mercury Levels in 

Wisconsin Chippewa Indians.” Archives of Environmental Health 49(1):53–58.

Pitchford, M and W. Malm. 1994. “Development and Application of a Standard Visual Index.” 

Atmospheric Environment 28(5): 1049-1054.

Prasad, A.M. and Iverson, L.R. 2003. “Little’s range and FIA importance value database for 135 

eastern U.S. tree species.” Northeastern Research Station, USDA Forest Service. 

Available on the Internet at 

<http://www.fs.fed.us/ne/delaware/4153/global/littlefia/index.html>.

Pryor, S.C. 1996. “Assessing Public Perception of Visibility for Standard Setting Exercises.” 

Atmospheric Environment 30, no. 15, pp. 2705-2716.

Pye, J.M. 1988. “Impact of ozone on the growth and yield of trees: A review.” Journal of 

Environmental Quality, 17, 347-360.

Qian Y., Gustafson W.I., Leung L.R., and Ghan S.J. 2009. “Effects of soot-induced snow albedo 

change on snowpack and hydrological cycle in western United States based on Weather 

Research Forecasting Chemistry and Regional Climate Simulations.” Journal of 

Geophysical Research 114 (DO2108).

Rae, D.A. 1983. Benefits of Visual Air Quality in Cincinnati Results of a Contingent Ranking 

Survey. Prepared for Electric Power Research Institute. May.
6-82

Ramanathan V. and Carmichael G. (2008) Global and regional climate changes due to black 

carbon Nature Geoscience 1, 221-227.

Rea, A. W., Lindberg, S. E., Scherbatskoy, T., & Keeler, G. J. 2002. “Mercury Accumulation in 

Foliage over Time in Two Northern Mixed-Hardwood Forests.” Water, Air, & Soil 

Pollution 133(1), 49-67.

Rimmer, C. C., McFarland, K. P., Evers, D. C., Miller, E. K., Aubry, Y., Busby, D., et al. 2005. 

“Mercury Concentrations in Bicknell’s Thrush and Other Insectivorous Passerines in 

Montane Forests of Northeastern North America.” Ecotoxicology 14(1), 223-240.

Scheuhammer, Anton M., Meyer Michael W., Sandheinrich, Mark B., and Murray, Michael W. 

2007. “Effects of environmental methylmercury on the health of wild birds, mammals, 

and fish,” Ambio Vol.36, No.1.

Sepulveda, Maria S., Frederick, Peter C., Spalding, Marilyn G., and Williams, Gary E. Jr. 1999. 

“Mercury contamination in free-ranging great egret nestlings (Ardea albus) from 

southern Florida, USA,” Environmental Toxicology and Chemistry Vol. 18, No.5.

Shindell, Drew (2007) Local and remote contributions to Arctic warming. Geophysical Research 

Letters, Vol 34, L14704, doi:10.1029/2007GL030221.

Simcik M.F., Eisenreich S.J., Lioy P.J. 1999. “Source apportionment and source/sink relationship 

of PAHs in the coastal atmosphere of Chicago and Lake Michigan.” Atmospheric 

Environment, 33, 5071-5079.

Simcik M.F., Eisenreich, S.J., Golden K.A., et al. 1996. “Atmospheric Loading of Polycyclic 

Aromatic Hydrocarbons to Lake Michigan as Recorded in the Sediments.” Environmental 

Science and Technology, 30, 3039-3046.

Sisler, J.F. 1996. Spatial and seasonal patterns and long-term variability of the composition of 

the haze in the United States: an analysis of data from the IMPROVE network. CIRA 

Report, ISSN 0737-5352-32, Colorado State University.

Smith, G., Coulston, J., Jepsen, E., Prichard, T. 2003. “A national ozone biomonitoring program—

results from field surveys of ozone sensitive plants in Northeastern forests (1994–

2000).” Environmental Monitoring and Assessment, 87, 271-291.

Smith, V.K., G. Van Houtven, and S.K. Pattanayak. 2002. “Benefit Transfer via Preference 

Calibration.” Land Economics 78:132-152.

Spencer, D.M., and D.F. Holecek. 2007. “Basic characteristics of the fall tourism market.” 

Tourism Management 28:491–504.

Taylor R. 1994. “Deterministic versus stochastic evaluation of the aggregate economic effects of 

price support programs.” Agricultural Systems 44: 461-473.
6-83

Tingey, D.T., and Taylor, G.E. 1982. “Variation in plant response to ozone: a conceptual model 

of physiological events.” In M.H. Unsworth & D.P. Omrod (Eds.), Effects of Gaseous Air 

Pollution in Agriculture and Horticulture. (pp.113-138). London, UK: Butterworth 

Scientific.

Tolley, G., A. Randall, G. Blomquist, M. Brien, R. Fabian, G. Fishelson, A. Frankel, M. Grenchik, J. 

Hoehn, A. Kelly, R. Krumm, E. Mensah, and T. Smith. 1984. Establishing and Valuing the 

Effects of Improved Visibility in Eastern United States. Prepared for U.S. Environmental 

Protection Agency, Office of Policy, Planning and Evaluation. March. U.S. Environmental 

Protection Agency Grant #807768-01-0. Available on the Internet at 

<http://yosemite.epa.gov/ee/epa/eerm.nsf/vwAN/EE-0003-01.pdf/$file/EE-0003-

01.pdf>.

Trijonis, J.C. et al. 1987. “Preliminary extinction budget results from the RESOLVE program,” pp. 

872-883. In: P.J. Bhardwaja, et al. Visibility Protection Research and Policy Aspects. Air 

Pollution Control Assoc., Pittsburgh, PA.

Trijonis, J.C. et al. 1988. RESOLVE Project Final Report: Visibility conditions and Causes of 

Visibility Degradation in the Mojave Desert of California. NWC TP #6869. Naval Weapons 

Center, China Lake, CA. Available on the Internet at 

<www.dtic.mil/dtic/tr/fulltext/u2/a206322.pdf>.

United Nations Environmental Programme, World Meteorological Organization and Stockholm 

Environment Institute (UNEP). 2011. Integrated Assessment of Black Carbon and 

Tropospheric Ozone Summary for Decision Makers. Available on the Internet at 

<http://www.unep.org/dewa/Portals/67/pdf/Black_Carbon.pdf>.

U.S. Census Bureau. 2010. “Sector 56: EC075612: Administrative Support and Waste 

Management and Remediation Services: Industry Series: Preliminary Comparative 

Statistics for the United States (2002 NAICS Basis): 2007 and 2002.” American FactFinder 

Available on the Internet at http://factfinder.census.gov (accessed August 25, 2010)

U.S. Department of the Interior (DOI). 2007. 2006 National Survey of Fishing, Hunting, and 

Wildlife-Associated Recreation. U.S. Department of the Interior, Fish and Wildlife 

Service, and U.S. Department of Commerce, U.S. Census Bureau. Washington, DC. 

Available on the Internet at <http://www.census.gov/prod/2008pubs/fhw06-nat.pdf>.

U.S. Environmental Protection Agency—Science Advisory Board (U.S. EPA-SAB). 1999. The Clean 

Air Act Amendments (CAAA) Section 812 Prospective Study of Costs and Benefits (1999): 

Advisory by the Advisory Council on Clean Air Compliance Analysis: Costs and Benefits of 

the CAAA. EPA-SAB-COUNCIL-ADV-00-002. October. Available on the Internet at 

<http://yosemite.epa.gov/sab/sabproduct.nsf/E992F918DF32131A852571B9004571F7/

$File/coua0002.pdf>.
6-84

U.S. Environmental Protection Agency—Science Advisory Board (U.S. EPA-SAB). 2004. Review of 

the Draft Analytical Plan for EPA’s Second Prospective Analysis—Benefits and Costs of 

the Clean Air Act, 1990-2020: An Advisory by the Advisory Council for Clean Air 

Compliance Analysis. EPA-SAB-COUNCIL-ADV-04-004. May. Available on the Internet at 

<http://yosemite.epa.gov/sab/sabproduct.nsf/7CCBBFE15CD4C8B185256F17005E3079/

$File/council_adv_04004.pdf>.

U.S. Environmental Protection Agency—Science Advisory Board (U.S. EPA-SAB). 2007. Clean Air 

Scientific Advisory Committee’s (CASAC) Review of the Agency’s Final Ozone Staff Paper.

EPA-CASAC-07-002. Available on the Internet at 

<http://yosemite.epa.gov/sab/sabproduct.nsf/FE915E916333D776852572AC007397B5/

$File/casac-07-002.pdf>.

U.S. Environmental Protection Agency—Science Advisory Board (U.S. EPA-SAB). 2010. Advisory 

on a Preliminary Draft of the Second Section 812 Prospective Study of the Benefits and 

Costs of the Clean Air Act (April 2010). EPA-COUNCIL-10-004. Available on the Internet at 

<http://yosemite.epa.gov/sab/sabproduct.nsf/553D59A280CDCF388525776D005EE83A

/$File/EPA-COUNCIL-10-004-unsigned.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 1997. Mercury Study Report to Congress. 

Volume V: Health Effects of Mercury and Mercury Compounds. EPA-452/R-97-007. U.S. 

EPA Office of Air Quality Planning and Standards, and Office of Research and 

Development. Available on the Internet at 

<http://www.epa.gov/ttncaaa1/t3/reports/volume5.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 1998. Advisory Council on Clean Air 

Compliance Analysis Advisory on the Clean Air Act Amendments (CAAA) of 1990 Section 

812 Prospective Study: Overview of Air Quality and Emissions Estimates: Modeling, 

Health and Ecological Valuation Issues Initial Studies. EPA-SAB-COUNCIL-ADV-98-003. 

Available on the Internet at 

<http://yosemite.epa.gov/sab/sabproduct.nsf/D20F5AE06F98883F852571AF00474927/

$File/coad9803.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 1999a. Regional Haze Regulations, July 1, 

1999. (64 FR 35714, July 1, 1999).

U.S. Environmental Protection Agency (U.S. EPA). 1999b. The Benefits and Costs of the Clean Air 

Act, 1990–2010. Prepared for U.S. Congress by U.S. EPA, Office of Air and Radiation,

Office of Policy Analysis and Review, Washington, DC, November; EPA report no. 

EPA410-R-99-001. Available on the Internet at <http://www.epa.gov/oar/sect812/1990-

2010/chap1130.pdf>.
6-85

U.S. Environmental Protection Agency (U.S. EPA). 2004. Air Quality Criteria for Particulate 

Matter Volume II of II. National Center for Environmental Assessment, Office of 

Research and Development, U.S. Environmental Protection Agency, Research Triangle 

Park, NC EPA/600/P-99/002bF. Available on the Internet at 

<http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=87903>.

U.S. Environmental Protection Agency (U.S. EPA). 2005. Regulatory Impact Analysis of the Final 

Clean Air Mercury Rule. Office of Air Quality Planning and Standards, Research Triangle 

Park, NC., March; EPA report no. EPA-452/R-05-003. Available on the Internet at 

<http://www.epa.gov/ttn/ecas/regdata/RIAs/mercury_ria_final.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2006a. Air Quality Criteria for Ozone and 

Related Photochemical Oxidants (Final). EPA/600/R-05/004aF-cF. Washington, DC: U.S. 

EPA. February. Available on the Internet at 

<http://cfpub.epa.gov/ncea/CFM/recordisplay.cfm?deid=149923>.

U.S. Environmental Protection Agency (U.S. EPA). 2006b. Regulatory Impact Analysis, 2006 

National Ambient Air Quality Standards for Particulate Matter. Office of Air Quality 

Planning and Standards, Research Triangle Park, NC. October. Available on the Internet 

at < http://www.epa.gov/ttn/ecas/regdata/RIAs/Appendix%20I--

Visibility%20Benefits%20Methodology.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2006c. Ecological Benefits Assessment 

Strategic Plan. EPA-240-R-06-001. Office of the Administrator. Washington, DC. October. 

Available on the Internet at 

<http://yosemite.epa.gov/ee/epa/eed.nsf/webpages/EcologBenefitsPlan.html>.

U.S. Environmental Protection Agency (U.S. EPA). 2007a. Guidance on the Use of Models and 

Other Analyses for Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, and 

Regional Haze. Office of Air Quality Planning and Standards. EPA-454/B-07-002. April. 

<Available on the Internet at http://www.epa.gov/scram001/guidance/guide/final-03-

pm-rh-guidance.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2007b. Review of the National Ambient Air 

Quality Standards for Ozone: Policy assessment of scientific and technical information. 

Staff Paper. Office of Air Quality Planning and Standards. EPA-452/R-07-007a. July. 

Available on the Internet at 

<http://www.epa.gov/ttn/naaqs/standards/ozone/data/2007_07_ozone_staff_paper.p

df>.

U.S. Environmental Protection Agency (U.S. EPA). 2007c. Technical Report on Ozone Exposure, 

Risk, and Impact Assessments for Vegetation. Office of Air Quality Planning and 

Standards. EPA-452/R-07-002. January. Available on the Internet at 

http://www.epa.gov/ttn/naaqs/standards/ozone/s_o3_pr.html
6-86

U.S. Environmental Protection Agency (U.S. EPA). 2008a. Regulatory Impact Analysis, 2008 

National Ambient Air Quality Standards for Ground-level Ozone, Chapter 6. Office of Air 

Quality Planning and Standards, Research Triangle Park, NC. March. Available at 

<http://www.epa.gov/ttn/ecas/regdata/RIAs/6-ozoneriachapter6.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2008b. U.S. EPA’s 2008 Report on the 

Environment (Final Report). Washington, D.C., EPA/600/R-07/045F (NTIS PB2008-

112484). May. Available on the Internet at 

<http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=190806>. Updated in 

December 2010, available on the Internet at 

<http://cfpub.epa.gov/eroe/index.cfm?fuseaction=detail.viewInd&showQues=Air&ch=4

7&lShowInd=0,287&subtop=341&lv=list.listByQues&r=188207>.

U.S. Environmental Protection Agency (U.S. EPA). 2008c. Integrated Science Assessment for 

Oxides of Nitrogen and Sulfur—Ecological Criteria National (Final Report). National 

Center for Environmental Assessment, Research Triangle Park, NC. EPA/600/R-08/139. 

December. Available on the Internet at 

<http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=201485>.

U.S. Environmental Protection Agency (U.S. EPA). 2009a. The NOx Budget Trading Program: 

2008 Environmental Results. Clean Air Markets Division. September. Available on the 

Internet at <http://www.epa.gov/airmarkt/progress/NBP_3/

NBP_2008_Environmental_Results.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2009b. Integrated Science Assessment for 

Particulate Matter (Final Report). EPA-600-R-08-139F. National Center for 

Environmental Assessment—RTP Division. December. Available on the Internet at 

<http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=216546>.

U.S. Environmental Protection Agency (U.S. EPA). 2009c. Risk and Exposure Assessment for 

Review of the Secondary National Ambient Air Quality Standards for Oxides of Nitrogen 

and Oxides of Sulfur (Final Report). EPA-452/R-09-008a. Office of Air Quality Planning 

and Standards, Research Triangle Park, NC. September. Available on the Internet at 

<http://www.epa.gov/ttn/naaqs/standards/no2so2sec/data/NOxSOxREASep2009MainC

ontent.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2010a. Updated Regulatory Impact Analysis 

(RIA) for the Reconsideration of the 2008 Ozone National Ambient Air Quality Standard 

(NAAQS). Office of Air Quality Planning and Standards, Research Triangle Park, NC. 

January. Available on the Internet at <http://www.epa.gov/ttn/ecas/regdata/RIAs/s1-

supplemental_analysis_full.pdf>.
6-87

U.S. Environmental Protection Agency (U.S. EPA). 2010b. Particulate Matter Urban-Focused 

Visibility Assessment—Final Document (Corrected). Office of Air Quality Planning and 

Standards, Research Triangle Park, NC. July. Available on the Internet at <Particulate 

Matter Urban-Focused Visibility Assessment—Final Document>.

U.S. Environmental Protection Agency (U.S. EPA). 2011a. Policy Assessment for the Review of 

the PM NAAQS—Final Document. Office of Air Quality Planning and Standards, Research 

Triangle Park, NC. April. Available on the Internet at 

<http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_pa.html>.

U.S. Environmental Protection Agency (U.S. EPA). 2011b. The Benefits and Costs of the Clean Air 

Act 1990 to 2020: EPA Report to Congress. Office of Air and Radiation, Washington, DC. 

March. Available on the Internet at 

<http://www.epa.gov/air/sect812/feb11/fullreport.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2011c. Regulatory Impact Analysis for the 

Federal Implementation Plans to Reduce Interstate Transport of Fine Particulate Matter 

and Ozone in 27 States; Correction of SIP Approvals for 22 States. June. Available on the 

Internet at: <http://www.epa.gov/airtransport/pdfs/FinalRIA.pdf>

U.S. Environmental Protection Agency (U.S. EPA). 2011d. Regulatory Impact Analysis for the 

Final Mercury and Air Toxics Standards. EPA-452/R-11-011. December. Available on the 

Internet at: <http://www.epa.gov/ttn/ecas/regdata/RIAs/matsriafinal.pdf>

U.S. Fish and Wildlife Service and U.S. Census Bureau (FWS and Census). 2007. 2006 National 

Survey of Fishing, Hunting, and Wildlife-Associated Recreation (FHWAR). FHW/06-NAT. 

U.S. Department of the Interior, U.S. Fish and Wildlife Service, Washington, DC, and U.S. 

Department of Commerce, U.S. Census Bureau, Washington, DC.

U.S. Forest Service (USFS). 2006. Forest Inventory and Analysis National Program: Forest 

Inventory Data Online. Online database. U.S. Department of Agriculture Forest Service, 

Forest Inventory and Analysis, Arlington, VA. Available on the Internet at 

<http://fia.fs.fed.us/tools-data>.

Valigura, R.A., R.B. Alexander, M.S. Castro, T.P. Meyers, H.W. Paerl, P.E. Stacy, and R.E. Turner. 

2001. Nitrogen Loading in Coastal Water Bodies: An Atmospheric Perspective. 

Washington, DC: American Geophysical Union.

Van Sickle, J., Baker, J.P., Simonin, H.A., Baldigo, B.P., Kretser, W.A., Sharpe, W.E. 1996. 

“Episodic acidification of small streams in the northeastern United States: Fish mortality 

in field bioassays.” Ecological Applications, 6, 408-421.

Wada, H. and Cristol, D.A. and McNabb, F.M.A. and Hopkins, W.A. 2009. “Suppressed 

adrenocortical responses and thyroid hormone levels in birds near a mercurycontaminated river.” Environmental Science & Technology 43(15), 6031-6038.
6-88

Wada, H., Yates, DE., Evers, DC., Taylor, RJ., Hopkins, WA. 2010. “Tissue mercury concentrations 

and adrenocortical responses of female big brown bats (Eptesicus fuscus) near a 

contaminated river.” Ecotoxicology 19(7), 1277-1284.

Winner, W.E. 1994. “Mechanistic analysis of plant responses to air pollution.” Ecological 

Applications, 4(4), 651-661.

Winner, W.E., and C.J. Atkinson. 1986. “Absorption of air pollution by plants, and consequences 

for growth.” Trends in Ecology and Evolution 1:15-18.

Wiscombe W. and Warren S. 1980. “A model for the spectral albedo of snow. Snow containing 

atmospheric aerosols.” J. Atmos. Sci. 37, 2734-2274.

Yates, David E., Mayack, David T., Munney, Kenneth, Evers David C., Major, Andrew, Kaur, 

Taranjit, and Taylor, Robert J. 2005. “Mercury levels in mink (Mustela vison) and river 

otter (Lonra canadensis) from northeastern North America,” Ecotoxicology 14, 263-274.
6.A-1

APPENDIX 6.A

ADDITIONAL DETAILS REGARDING THE VISIBILITY BENEFITS METHODOLOGY

6.A.1 Introduction

Economic benefits may result from two broad categories of changes in light extinction: 

(1) changes in “residential” visibility—i.e., the visibility in and around the locations where 

people live; and (2) changes in “recreational” visibility at Class I areas—i.e., visibility at Class I 

national parks and wilderness areas.1 In this analysis, only those recreational and residential 

benefits in areas that have been directly studied in the valuation literature are included in the 

primary presentation of benefits; recreational benefits in other U.S. Class I regions and 

residential benefits in other metropolitan areas are presented as sensitivity analyses of visibility 

benefits.

In Chapter 6 of this RIA, we provide an overview of the visibility benefits methodology 

and results. This appendix provides additional detail regarding specific aspects of the visibility 

benefits methodology and is organized as follows. Section 6.A.2 describes the process we used 

to convert the modeled light extinction data to match the spatial scale of the visibility benefits 

assessment. We present the basic utility model in Section 6.A.3. In Section 6.A.4 we discuss the 

measurement of visibility, and the mapping from environmental “bads” to environmental 

“goods.” In Sections 6.A.5 and 6.A.6 we summarize the methodology for estimating the 

parameters of the model corresponding to visibility at in-region and out-of-region Class I areas, 

and visibility in residential areas, respectively, and we describe the methods used to estimate 

these parameters. Section 6.A.7 describes the process for aggregating the recreational and 

residential visibility benefits. Section 6.A.8 describes the adjustment to reflect income growth 

over time. Section 6.A.9 provides all the parameters used to calculate visibility benefits.

6.A.2 Converting Modeled Light Extinction Estimates

To calculate visibility benefits, we use light extinction estimates generated by the CMAQ 

model.2 Modeled light extinction estimates are measured in units of inverse megameters 

(Mm-1). Because the valuation studies measure visibility in terms of visual range, we convert the 

light extinction units from Mm-1 to visual range (in km) for both recreational and residential 

 1 Hereafter referred to as Class I areas, which are defined as areas of the country such as national parks, national 

wilderness areas, and national monuments that have been set aside under Section 169(a) of the Clean Air Act 

to receive the most stringent degree of air quality protection. Class I federal lands fall under the jurisdiction of 

three federal agencies, the National Park Service, the Fish and Wildlife Service, and the Forest Service. 2 For more information regarding the CMAQ modeling conducted for the PM NAAQS RIA, please see Chapter 3 of 

this RIA.
6.A-2

visibility benefits. Using the relationships derived by Pitchford and Malm (1994), the formulas 

for this conversion are

Deciviews = 10 ∗ ln �

391

VR � = 10 ∗ ln �

βext

10 �

where VR denotes visual range (in kilometers) and βext denotes light extinction (in Mm-1

). 

Because we leverage the tools and data prepared for previous analyses (U.S. EPA, 2011), we use 

a two-step process to convert from Mm-1 to VR using deciviews as an intermediate conversion 

instead of converting directly. Therefore, the full formula incorporating the two-step 

conversion is

VR = 391 ∗ e−0.1∗(10∗ln�

βext

10 �)

The spatial scale of the modeled light extinction estimates must also be adjusted to 

correspond with the design of the valuation studies and the underlying population and 

economic data. For the residential visibility benefits analysis, we convert the spatial resolution 

of the light extinction estimates from 12-km grid to county-level. We use county-level light 

extinction to match the MSA boundaries, population data, and household income data. We 

used the geographic centroids of each 12-km grid cell with the Veronoi Neighborhood 

Averaging (VNA) interpolation method in the BenMAP model for this conversion (Abt 

Associates, 2010).

For the recreational visibility benefits analysis, we use the light extinction estimates 

from 12-km grid cell located at the geographic center of the Class I area. Although we 

considered using the IMPROVE monitor location instead, we selected the park centroid for 

three reasons:

1. Consistency with previous method for estimating recreational visibility benefits

2. Not all Class I areas have monitors, and shared monitors may be outside park

3. Siting criteria for IMPROVE monitors do not include iconic scenic vista location

6.A.3 Basic Utility Model

Within the category of recreational visibility, further distinctions have been made. There 

is evidence (Chestnut and Rowe, 1990) that an individual’s WTP for improvements in visibility at 

a Class I area is influenced by whether it is in the region in which the individual lives, or whether 

it is somewhere else. In general, people appear to be willing to pay more for visibility 
6.A-3

improvements at parks and wilderness areas that are “in-region” than at those that are “out-ofregion.” This is plausible, because people are more likely to visit, be familiar with, and care 

about parks and wilderness areas in their own part of the country.

To value estimated changes in visibility, we use an approach that is consistent with 

economic theory. Below we discuss an application of the Constant Elasticity of Substitution 

(CES) utility function approach3 to value both residential visibility improvements and visibility 

improvements at Class I areas in the United States. This approach is based on the preference 

calibration method developed by Smith, Van Houtven, and Pattanayak (2002).

We begin with a CES utility function in which a household derives utility from

1. “all consumption goods,” X,

2. visibility in the residential area in which the household is located (“residential 

visibility”),4

3. visibility at Class I areas in the same region as the household (“in-region recreational 

visibility”), and

4. visibility at Class I areas outside the household’s region (“out-of-region recreational 

visibility”).

We have specified a total of six recreational visibility regions,5 so there are five regions 

for which any household is out of region. The utility function of a household in the nth

residential area and the i

th region of the country is:

 3 The constant elasticity of substitution utility function has been chosen for use in this analysis because of its 

flexibility when illustrating the degree of substitutability present in various economic relationships (in this case, 

the trade-off between income and improvements in visibility). 4 We remind the reader that, although residential and recreational visibility benefits estimation is discussed 

simultaneously in this section, benefits are calculated and presented separately for each visibility category. 5 See Section 6.3.4 of this RIA for a description of the different recreational visibility considered in this analysis.

U X Z Q Q

i k j k

ni n ik ik

k

N

jk jk

k

N

j i

ik jk

i j

= + + +

> > ∀ > ∀ ≤

= ≠ =

( ∑ ∑ ∑ ) ,

, , , , , , , .

ρ ρ ρ ρ /ρ θ γ δ

θ γ δ ρ

1 1

1

0 0 0 1
6.A-4

where

Zn = the level of visibility in the nth residential area;

Qik = the level of visibility at the kth in-region park (i.e., the kth park in the ith region);

Qjk = the level of visibility at the kth park in the jth region (for which the household is 

out of region), j≠i;

Ni = the number of Class I areas in the ith region;

Nj = the number of Class I areas in the jth region (for which the household is out of 

region), j≠i; and

θ, the γ’s and δ’s are parameters of the utility function corresponding to the visibility 

levels at residential areas, and at in-region and out-of-region Class I areas, 

respectively.

In particular, the γik’s are the parameters corresponding to visibility at in-region Class I 

areas; the δ1’s are the parameters corresponding to visibility at Class I areas in region 1 

(California), if i≠1; the δ2’s are the parameters corresponding to visibility at Class I areas in 

region 2 (Colorado Plateau), if i≠2, and so forth. Because the model assumes that the 

relationship between residential visibility and utility is the same everywhere, there is only one 

θ. The parameter ρ in this CES utility function is an important determinant of the slope of the 

marginal WTP curve associated with any of the environmental quality variables. When ρ=1, the 

marginal WTP curve is horizontal. When ρ<1, it is downward sloping.

The household’s budget constraint is:

where m is income, and p is the price of X. Without loss of generality, set ρ = 1. The only choice 

variable is X. The household maximizes its utility by choosing X=m. The indirect utility function 

for a household in the nth residential area and the ith region is therefore

where Q denotes the vector of vectors, Q1, Q2, Q3, Q4, Q5, and Q6, and the unsubscripted γ and 

δ denote vectors as well.

m − p ⋅ X ≤ 0 ,

Vni m Zn Q m Zn ikQik Q

k

N

jk jk

k

N

j i

i j

( , , ; , , , ) ( ) , / θ γ δ ρ θ γ δ ρ ρ ρ ρ ρ = + + + = ≠ =

∑ ∑ ∑

1 1

1
6.A-5

Given estimates of ρ, θ, the γ’s and the δ’s, the household’s utility function and the 

corresponding WTP functions are fully specified. The household’s WTP for any set of changes in 

the levels of visibility at in-region Class I areas, out-of-region Class I areas, and the household’s 

residential area can be shown to be:

The household’s WTP for a single visibility improvement will depend on its order in the 

series of visibility improvements the household is valuing. If it is the first visibility improvement 

to be valued, the household’s WTP for it follows directly from the previous equation. For 

example, the household’s WTP for an improvement in visibility at the first in-region park, from 

Qi1 = Q0i1 to Qi1 = Q1i1, is

if this is the first (or only) visibility change the household values.

6.A.4 Measure of Visibility: Environmental “Goods” Versus “Bads”

In the above model, Q and Z are environmental “goods.” As the level of visibility 

increases, utility increases. The utility function and the corresponding WTP function both have 

reasonable properties. The first derivative of the indirect utility function with respect to Q (or Z) 

is positive; the second derivative is negative. WTP for a change from Q0 to a higher (improved) 

level of visibility, Q1, is therefore a concave function of Q1, with decreasing marginal WTP.

The measure of visibility that is currently preferred by air quality scientists is the 

deciview, which increases as visibility decreases. Deciview, in effect, is a measure of the lack of 

visibility. As deciviews increase, visibility, and therefore utility, decreases. The deciview, then, is 

a measure of an environmental “bad.” There are many examples of environmental “bads”—all 

types of pollution are environmental “bads.” Utility decreases, for example, as the 

concentration of particulate matter in the atmosphere increases.

One way to value decreases in environmental bads is to consider the “goods” with 

which they are associated, and to incorporate those goods into the utility function. In 

particular, if B denotes an environmental “bad,” such that:

WTPni Z Q m m Z n Z n ik Q ik Q ik Q Q

k

N

jk jk jk

k

N

j i

i j

( , ) [ ( ) ( ) ( )] . / ∆ ∆ = − + − + − + − = ≠ =

∑ ∑ ∑ ρ ρ ρ ρ ρ ρ ρ ρ θ 0 1 γ 0 1 δ

1

0 1

1

1

WTP Qi m m i Q i Q i ( ) [ ( )] , / ∆ 1 1 0 1 1 1

1 = − + − ρ ρ ρ ρ γ

∂

∂

V

B

< 0 ,
6.A-6

and the environmental “good,” Q, is a function of B,

then the environmental “bad” can be related to utility via the corresponding environmental 

“good”:6

The relationship between Q and B, F(B), is an empirical relationship that must be estimated.

There is a potential problem with this approach, however. If the function relating B and 

Q is not the same everywhere (i.e., if for a given value of B, the value of Q depends on other 

factors as well), then there can be more than one value of the environmental good 

corresponding to any given value of the environmental bad, and it is not clear which value to 

use. This has been identified as a problem with translating deciviews (an environmental “bad”) 

into visual range (an environmental “good”). It has been noted that, for a given deciview value, 

there can be many different visual ranges, depending on the other factors that affect visual 

range—such as light angle and altitude. We note here, however, that this problem is not unique 

to visibility, but is a general problem when trying to translate environmental “bads” into 

“goods.”7

In order to translate deciviews (a “bad”) into visual range (a “good”), we use a 

relationship derived by Pitchford and Malm (1994) in which

where DV denotes deciview and VR denotes visual range (in kilometers). Solving for VR as a 

function of DV yields

 6 There may be more than one “good” related to a given environmental “bad.” To simplify the discussion, however, 

we assume only a single “good.” 7 Another example of an environmental “bad” is particulate matter air pollution (PM). The relationship between 

survival probability (Q) and the ambient PM level is generally taken to be of the form 

where ∀ denotes the mortality rate (or level) when there is no ambient PM (i.e., when 

PM=0). However, α is implicitly a function of all the factors other than PM that affect mortality. As these factors 

change (e.g., from one location to another), αwill change (just as visual range changes as light angle changes). It 

is therefore possible to have many values of Q corresponding to a given value of PM, as the values of ∀ vary.

Q = F(B) ,

V = V(m,Q) = V(m,F(B)) .

DV 10* ln(

391

VR = ) ,

Q e

PM = 1 − α β .
6.A-7

This conversion is based on specific assumptions characterizing the “average” conditions 

of those factors, such as light angle, that affect visual range. To the extent that specific 

locations depart from the average conditions, the relationship will be an imperfect 

approximation.8

6.A.5 Estimating the Parameters for Visibility at Class I Areas: the γ’s and δ’s

As noted in Section 6.A.3, if we consider a particular visibility change as the first or the 

only visibility change valued by the household, the household’s WTP for that change in visibility 

can be calculated, given income (m), the “shape” parameter, ρ, and the corresponding 

recreational visibility parameter. For example, a Southeast household’s WTP for a change in 

visibility at in-region parks (collectively) from Q1 = Q01 to Q1 = Q11 is:

if this is the first (or only) visibility change the household values.

Alternatively, if we have estimates of m as well as WTP1

in and WTP1out of in-region and 

out-of-region households, respectively, for a given change in visibility from Q01 to Q11 in 

Southeast parks, we can solve for γ1 and δ1 as a function of our estimates of m, WTP1

in and 

WTP1

out, for any given value of ρ. Generalizing, we can derive the values of γ and δ for the jth

region as follows:

and

Chestnut and Rowe (1990) and Chestnut (1997) estimated WTP (per household) for 

specific visibility changes at national parks in three regions of the United States—both for 

households that are in-region (in the same region as the park) and for households that are out-

 8 Ideally, we would want the location-, time-, and meteorological condition-specific relationships between 

deciviews and visual range, which could be applied as appropriate. This is probably not feasible, however.

VR 391* e . 0.1DV = −

WTP(DQ ) m [m g (Q Q )] 1

r

1 01

r

11

r 1/r = − + −

γ

ρ ρ

j ρ ρ

j

in

j j

m WTP m

Q Q = − −

−

( )

( ) 0 1

δ

ρ ρ

j ρ ρ

j

out

j j

m WTP m

Q Q = − −

−

( )

( ) . 0 1
6.A-8

of-region. The Chestnut and Rowe study asked study subjects what they would be willing to pay 

for each of three visibility improvements in the national parks in a given region. Study subjects 

were shown a map of the region, with dots indicating the locations of the parks in question. The 

WTP questions referred to the three visibility improvements in all the parks collectively; the 

survey did not ask subjects’ WTP for these improvements in specific parks individually. 

Responses were categorized according to whether the respondents lived in the same region as 

the parks in question (“in-region” respondents) or in a different region (“out-of-region” 

respondents). The areas for which in-region and out-of-region WTP estimates are available 

from Chestnut and Rowe (1990), and the sources of benefits transfer-based estimates that we 

employ in the absence of estimates, are summarized in Table 6.A-1. In all cases, WTP refers to 

WTP per household.

Table 6.A-1. Available Information on WTP for Visibility Improvements in National Parks

Region of Park

Region of Household

In Regiona Out of Regionb

1. California WTP estimate from study WTP estimate from study

2. Colorado Plateau WTP estimate from study WTP estimate from study

3. Southeast United States WTP estimate from study WTP estimate from study

4. Northwest United States (based on benefits transfer from California)

5. Northern Rockies (based on benefits transfer from Colorado Plateau)

6. Rest of United States (based on benefits transfer from Southeast U.S.)

a In-region” WTP is WTP for a visibility improvement in a park in the same region as that in which the household is 

located. For example, in-region WTP in the “Southeast” row is the estimate of the average Southeast 

household’s WTP for a visibility improvement in a Southeast park.

b Out-of-region” WTP is WTP for a visibility improvement in a park that is not in the same region in which the 

household is located. For example, out-of-region WTP in the “Southeast” row is the estimate of WTP for a 

visibility improvement in a park in the Southeast by a household outside of the Southeast.

In the primary calculation of visibility benefits for this analysis, only visibility changes at 

parks within visibility regions for which a WTP estimate was available from Chestnut and Rowe 

(1990) are considered (for both in- and out-of-region benefits). Primary estimates will not 

include visibility benefits calculated by transferring WTP values to visibility changes at parks not 

included in the Chestnut and Rowe study. Transferred benefits at parks located outside of the 

Chestnut and Rowe visibility regions will, however, be included as an alternative calculation.
6.A-9

The values of the parameters in a household’s utility function will depend on where the 

household is located. The region-specific parameters associated with visibility at Class I areas 

(that is, all parameters except the residential visibility parameter) are arrayed in Table 6.A-2. 

The parameters in columns 1 through 3 can be directly estimated using WTP estimates from 

Chestnut and Rowe (1990) (the columns labeled “Region 1,” “Region 2,” and “Region 3”).

Table 6.A-2. Summary of Region-Specific Recreational Visibility Parameters to be Estimated in 

Household Utility Functions

Region of Household

Region of Park

Region 1 Region 2 Region 3 Region 4 Region 5 Region 6

Region 1 γ1

a δ2 δ3 δ4 δ5 δ6

Region 2 δ1 γ2 δ3 δ4 δ5 δ6

Region 3 δ1 δ2 γ3 δ4 δ5 δ6

Region 4 δ1 δ2 δ3 γ4 δ5 δ6

Region 5 δ1 δ2 δ3 δ4 γ5 δ6

Region 6 δ1 δ2 δ3 δ4 δ5 γ6

a The parameters arrayed in this table are region-specific rather than park-specific or wilderness area-specific. For 

example, δ1 is the parameter associated with visibility at “Class I areas in region 1” for a household in any region 

other than region 1. The benefits analysis must derive Class I area-specific parameters (e.g., δ1k, for the kth Class I 

area in the first region).

For the three regions covered in Chestnut and Rowe (1990a) (California, the Colorado 

Plateau, and the Southeast United States), we can directly use the in-region WTP estimates 

from the study to estimate the parameters in the utility functions corresponding to visibility at 

in-region parks (γ1); similarly, we can directly use the out-of-region WTP estimates from the 

study to estimate the parameters for out-of-region parks (δ1). For the other three regions not 

covered in the study, however, we must rely on benefits transfer to estimate the necessary 

parameters.

While Chestnut and Rowe (1990) provide useful information on households’ WTP for 

visibility improvements in national parks, there are several significant gaps remaining between 

the information provided in that study and the information necessary for the benefits analysis. 

First, as noted above, the WTP responses were not park specific, but only region specific. 

Because visibility improvements vary from one park in a region to another, the benefits analysis 

must value park-specific visibility changes. Second, not all Class I areas in each of the three 

regions considered in the study were included on the maps shown to study subjects. Because 
6.A-10

the focus of the study was primarily national parks, most Class I wilderness areas were not 

included. Third, only three regions of the United States were included, leaving the three 

remaining regions without direct WTP estimates.

In addition, Chestnut and Rowe (1990) elicited WTP responses for three different

visibility changes, rather than a single change. In theory, if the CES utility function accurately 

describes household preferences, and if all households in a region have the same preference 

structure, then households’ three WTP responses corresponding to the three different visibility 

changes should all produce the same value of the associated recreational visibility parameter, 

given a value of ρ and an income, m. In practice, of course, this is not the case.

In addressing these issues, we take a three-phase approach:

1. We estimate region-specific parameters for the region in the modeled domain 

covered by Chestnut and Rowe (1990a) (California, the Colorado Plateau, and the 

Southeast)—γ1, γ2, and γ3 and δ1, δ2, and δ3.

2. We infer region-specific parameters for those regions not covered by the Chestnut 

and Rowe study (the Northwest United States, the Northern Rockies, and the rest of 

the U.S.)—γ4, γ5, and γ6 and δ4, δ5, and δ6.

3. We derive park- and wilderness area-specific parameters within each region (γ1k and 

δ1k, for k=1, ..., N1; γ2k and δ2k, for k=1, ..., N2; and so forth).

The question that must be addressed in the first phase is how to estimate a single 

region-specific in-region parameter and a single region-specific out-of-region parameter for 

each of the three regions covered in Chestnut and Rowe (1990) from study respondents’ WTPs 

for three different visibility changes in each region. All parks in a region are treated collectively 

as if they were a single “regional park” in this first phase. In the second phase, we infer regionspecific recreational visibility parameters for regions not covered in the Chestnut and Rowe 

study (the Northwest United States, the Northern Rockies, and the rest of the United States). As 

in the first phase, we ignore the necessity to derive park-specific parameters at this phase. 

Finally, in the third phase, we derive park- and wilderness area-specific parameters for each 

region.

6.A.5.1 Estimating Region-Specific Recreational Visibility Parameters for the Region Covered 

in the Chestnut and Rowe Study (Regions 1, 2, and 3)

Given a value of ρ and estimates of m and in-region and out-of-region WTPs for a 

change from Q0 to Q1 in a given region, the in-region parameter, γ, and the out-of-region 

parameter, δ, for that region can be solved for. Chestnut and Rowe (1990), however, 
6.A-11

considered not just one, but three visibility changes in each region, each of which results in a 

different calibrated γ and a different calibrated δ, even though in theory all the γ’s should be 

the same and similarly, all the δ’s should be the same. For each region, however, we must have 

only a single γ and a single δ.

Denoting as our estimate of γ for the jth region, based on all three visibility changes, 

we chose to best predict the three WTPs observed in the study for the three visibility 

improvements in the jth region. First, we calculated , i=1, 2, 3, corresponding to each of the 

three visibility improvements considered in the study. Then, using a grid search method 

beginning at the average of the three’s , we chose to minimize the sum of the squared 

differences between the WTPs we predict using and the three region-specific WTPs 

observed in the study. That is, we selected to minimize:

where WTPij and WTPij() are the observed and the predicted WTPs for a change in visibility in 

the jth region from Q0 = Q0i to Q1= Q1i, i=1, ..., 3. An analogous procedure was used to select an 

optimal δ, for each of the three regions in the Chestnut and Rowe study.

6.A.5.2 Inferring Region-Specific Recreational Visibility Parameters for Regions Not Covered 

in the Chestnut and Rowe Study (Regions 4, 5, and 6)

One possible approach to estimating region-specific parameters for regions not covered 

by Chestnut and Rowe (1990a) (γ4, γ5, and γ6 and δ4, δ5, and δ6) is to simply assume that 

households’ utility functions are the same everywhere, and that the environmental goods being 

valued are the same—e.g., that a change in visibility at national parks in California is the same 

environmental good to a Californian as a change in visibility at national parks in Minnesota is to 

a Minnesotan.

For example, to estimate δ4 in the utility function of a California household, 

corresponding to visibility at national parks in the Northwest United States, we might assume 

that out-of-region WTP for a given visibility change at national parks in the Northwest United 

States is the same as out-of-region WTP for the same visibility change at national parks in 

California (income held constant). Suppose, for example, that we have an estimated mean WTP 

of out-of-region households for a visibility change from Q01 to Q11 at national parks in California 

(region 1), denoted WTP1

out. Suppose the mean income of the out-of-region subjects in the 

γj

γj

γji

γji

γj

(WTP (  ) WTP ) ij j ij

i

γ − =

∑ 2

1

3
6.A-12

study was m. We might assume that, for the same change in visibility at national parks in the 

Northwest United States, WTP4

out = WTP1out among out-of-region individuals with income m.

We could then derive the value of δ4, given a value of ρ as follows:

where Q04 = Q01 and Q14 = Q11, (i.e., where it is the same visibility change in parks in region 4 

that was valued at parks in the region 1).

This benefits transfer method assumes that (1) all households have the same preference 

structures and (2) what is being valued in the Northwest United States (by a California 

household) is the same as what is being valued in the California (by all out-of-region 

households). While we cannot know the extent to which the first assumption approximates 

reality, the second assumption is clearly problematic. National parks in one region are likely to 

differ from national parks in another region in both quality and quantity (i.e., number of parks).

One statistic that is likely to reflect both the quality and quantity of national parks in a 

region is the average annual visitation rate to the parks in that region. A reasonable way to 

gauge the extent to which out-of-region people would be willing to pay for visibility changes in 

parks in the Northwest United States versus in California might be to compare visitation rates in 

the two regions.9 Suppose, for example, that twice as many visitor-days are spent in California 

parks per year as in parks in the Northwest United States per year. This could be an indication 

that the parks in California are in some way more desirable than those in the Northwest United 

States and/or that there are more of them—i.e., that the environmental goods being valued in 

the two regions (“visibility at national parks”) are not the same.

A preferable way to estimate δ4, then, might be to assume the following relationship:

(income held constant), where n1 = the average annual number of visitor-days to California 

parks and n4 = the average annual number of visitor-days to parks in the Northwest United 

States. This implies that

 9 We acknowledge that reliance on visitation rates does not get at nonuse value.

δ

ρ ρ

4 ρ ρ

4

04 14

= − −

−

(m WTP ) m

Q Q

out

WTP

WTP

n

n

out

out

4

1

4

1

=
6.A-13

for the same change in visibility in region 4 parks among out-of-region individuals with income 

m. If, for example, n1 = 2n4, WTP4

out would be half of WTP1out. The interpretation would be the 

following: California national parks have twice as many visitor-days per year as national parks in 

the Northwest United States; therefore they must be twice as desirable/plentiful; therefore, 

out-of-region people would be willing to pay twice as much for visibility changes in California 

parks as in parks in the Northwest United States; therefore a Californian would be willing to pay 

only half as much for a visibility change in national parks in the Northwest United States as an 

out-of-region individual would be willing to pay for the same visibility change in national parks 

in California. This adjustment, then, is based on the premise that the environmental goods 

being valued (by people out of region) are not the same in all regions.

The parameter δ4 is estimated as shown above, using this adjusted WTP4

out. The same 

procedure is used to estimate δ5 and δ6. We estimate γ4, γ, and γ6 in an analogous way, using 

the in-region WTP estimates from the transfer regions, e.g.,

6.A.5.3 Estimating Park- and Wilderness Area-Specific Parameters

As noted above, Chestnut and Rowe (1990) estimated WTP for a region’s national parks 

collectively, rather than providing park-specific WTP estimates. The ’s and ’s are the 

the parameters that would be in household utility functions if there were only a single park in 

each region, or if the many parks in a region were effectively indistinguishable from one 

another. Also noted above is the fact that the Chestnut and Rowe study did not include all Class 

I areas in the regions it covered, focusing primarily on national parks rather than wilderness 

areas. Most Class I wilderness areas were not represented on the maps shown to study 

subjects. In California, for example, there are 31 Class I areas, including 6 national parks and 25 

wilderness areas. The Chestnut and Rowe study map of California included only 10 of these 

Class I areas, including all 6 of the national parks. It is unclear whether subjects had in mind “all 

parks and wilderness areas” when they offered their WTPs for visibility improvements, or 

whether they had in mind the specific number of (mostly) parks that were shown on the maps. 

The derivation of park- and wilderness area-specific parameters depends on this.

WTP

n

n

WTP out out

4

4

1

1 = *

WTP

n

n

WTP in in

4

4

1

1 = * .
6.A-14

6.A.5.4 Derivation of Region-Specific WTP for National Parks and Wilderness Areas

If study subjects were lumping all Class I areas together in their minds when giving their 

WTP responses, then it would be reasonable to allocate that WTP among the specific parks and 

wilderness areas in the region to derive park- and wilderness area-specific γ’s and δ’s for the 

region. If, on the other hand, study subjects were thinking only of the (mostly) parks shown on 

the map when they gave their WTP response, then there are two possible approaches that 

could be taken. One approach assumes that households would be willing to pay some 

additional amount for the same visibility improvement in additional Class I areas that were not 

shown, and that this additional amount can be estimated using the same benefits transfer 

approach used to estimate region-specific WTPs in regions not covered by Chestnut and Rowe 

(1990a).

However, even if we believe that households would be willing to pay some additional 

amount for the same visibility improvement in additional Class I areas that were not shown, it is 

open to question whether this additional amount can be estimated using benefits transfer 

methods. A third possibility, then, is to simply omit wilderness areas from the benefits analysis. 

For this analysis we calculate visibility benefits assuming that study subjects lumped all Class I 

areas together when stating their WTP, even if these Class I areas were not present on the map.

6.A.5.5 Derivation of Park- and Wilderness Area-Specific WTPs, Given Region-Specific WTPs 

for National Parks and Wilderness Areas

The first step in deriving park- and wilderness area-specific parameters is the estimation 

of park- and wilderness area-specific WTPs. To derive park and wilderness area-specific WTPs, 

we apportion the region-specific WTP to the specific Class I areas in the region according to 

each area’s share of the region’s visitor-days. For example, if WTP1

in and WTP1out denote the 

mean household WTPs in the Chestnut and Rowe (1990) study among respondents who were 

in-region-1 and out-of-region-1, respectively, n1k denotes the annual average number of visitordays to the kth Class I area in California, and n1 denotes the annual average number of visitordays to all Class I areas in California (that are included in the benefits analysis), then we assume 

that

and

WTP

n

n k WTP in k in

1

1

1

1 = * ,
6.A-15

Using WTPj

in and WTPjout, either from the Chestnut and Rowe study (for j = 1, 2, and 3) or 

derived by the benefits transfer method (for j = 4, 5, and 6), the same method is used to derive 

Class I area-specific WTPs in each of the six regions.

While this is not a perfect allocation scheme, it is a reasonable scheme, given the 

limitations of data. Visitors to national parks in the United States are not all from the United 

States, and certainly not all from the region in which the park is located. A very large proportion 

of the visitors to Yosemite National Park in California, for example, may come from outside the 

United States. The above allocation scheme implicitly assumes that the relative frequencies of 

visits to the parks in a region from everyone in the world is a reasonable index of the relative 

WTP of an average household in that region (WTPj

in) or out of that region (but in the United 

States) (WTPj

out) for visibility improvements at these parks.10

A possible problem with this allocation scheme is that the relative frequency of visits is 

an indicator of use value but not necessarily of nonuse value, which may be a substantial 

component of the household’s total WTP for a visibility improvement at Class I areas. If park A 

is twice as popular (i.e., has twice as many visitors per year) as park B, this does not necessarily 

imply that a household’s WTP for an improvement in visibility at park A is twice its WTP for the 

same improvement at park B. Although an allocation scheme based on relative visitation 

frequencies has some obvious problems, however, it is still probably the best way to allocate a 

collective WTP.

6.A.5.6 Derivation of Park- and Wilderness Area-Specific Parameters, Given Park- and 

Wilderness-Specific WTP

Once the Class I area-specific WTPs have been estimated, we could derive the park- and 

wilderness area-specific γ’s and δ’s using the method used to derive region-specific γ’s and δ’s. 

Recall that that method involved (1) calibrating γ and δ to each of the three visibility 

improvements in the Chestnut and Rowe study (producing three γ’s and three δ’s), 

(2) averaging the three γ’s and averaging the three δ’s, and finally, (3) using these average γ and 

δ as starting points for a grid search to find the optimal γ and the optimal δ—i.e., the γ and δ 

 10 This might be thought of as two assumptions: (1) that the relative frequencies of visits to the parks in a region 

from everyone in the world is a reasonable representation of the relative frequency of visits from people in the 

United States—i.e., that the parks that are most popular (receive the most visitors per year) in general are also 

the most popular among Americans; and (2) that the relative frequency with which Americans visit each of their 

parks is a good index of their relative WTPs for visibility improvements at these parks.

WTP

n

n

 *WTP . 1k

out 1k

1

1

out =
6.A-16

that would allow us to reproduce, as closely as possible, the three in-region and three out-ofregion WTPs in the study for the three visibility changes being valued.

Going through this procedure for each national park and each wilderness area 

separately would be very time consuming, however. We therefore used a simpler approach, 

which produces very close approximations to the γ’s and δ’s produced using the above 

approach. If:

WTPj

in = the in-region WTP for the change in visibility from Q0 to Q1 in the jth region;

WTPjk

in = the in-region WTP for the same visibility change (from Q0 to Q1) in the kth

Class I area in the jth region (= sjk*WTPj

in, where sjk is the kth area’s share of 

visitor-days in the jth region);

m = income;

γj* = the optimal value of γ for the jth region; and

γjk = the value of γjk calibrated to WTPjk

in and the change from Q0 to Q1;

then11:

and

which implies that:

where:

 11 γj

* is only approximately equal to the right-hand side because, although it is the optimal value designed to 

reproduce as closely as possible all three of the WTPs corresponding to the three visibility changes in the 

Chestnut and Rowe study, γj* will not exactly reproduce any of these WTPs. 

γ

ρ ρ

j ρ ρ

j

in

m WTP m

Q Q

* ( )

( )

≈ − −

− 0 1

γ

ρ ρ

jk ρ ρ

jk

in m WTP m

Q Q = − −

−

( )

( ) 0 1

γ γ jk a jk j ≈ * , *

a

m WTP m

m WTP m jk

jk

in

j

in = − −

− −

( )

( ) .

ρ ρ

ρ ρ
6.A-17

We use the adjustment factor, ajk, to derive γjk from γj*, for the kth Class I area in the jth

region. We use an analogous procedure to derive δjk from δj* for the kth Class I area in the jth

region (where, in this case, we use WTPj

out and WTPjkout instead of WTPjin and WTPjkin).12

6.A.6 Estimating the Parameter for Visibility in Residential Areas: θ

In previous assessments, EPA used a study on residential visibility valuation conducted 

in 1990 (McClelland et al., 1993). Consistent with advice from EPA’s Science Advisory Board 

(SAB), EPA designated the McClelland et al. study as significantly less reliable for regulatory 

benefit-cost analysis, although it does provide useful estimates on the order of magnitude of 

residential visibility benefits (U.S. EPA-SAB, 1999).13 In order to estimate residential visibility 

benefits in this analysis, we have replaced the previous methodology with a new benefits 

transfer approach and incorporated additional valuation studies. This new approach was 

developed for The Benefits and Costs of the Clean Air Act 1990 to 2020: EPA Report to Congress

(U.S. EPA, 2011) and reviewed by the SAB (U. S. EPA-SAB, 2010). To value residential visibility 

improvements, the new approach draws upon information from the Brookshire et al. (1979), 

Loehman et al. (1985) and Tolley et al. (1984) studies.14 These studies provide primary visibility 

values for Atlanta, Boston, Chicago, Denver, Los Angeles, Mobile, San Francisco, and 

Washington D.C.15

The estimation of θ is a simpler procedure for residential visibility benefits, involving a 

straightforward calibration using the study income and WTP for each study city:

 12 This method uses a single in-region WTP and a single out-of-region WTP per region. Although the choice of WTP 

will affect the resulting adjustment factors (the ajk’s) and therefore the resulting γjk’s and δjk’s, the effect is 

negligible. We confirmed this by using each of the three in-region WTPs in California and comparing the 

resulting three sets of γjk’s and δjk’s, which were different from each other by about one one-hundredth of a 

percent. 13 EPA’s Advisory Council on Clean Air Compliance Analysis noted that the McClelland et al. (1993) study may not 

incorporate two potentially important adjustments. First, their study does not account for the “warm glow”

effect, in which respondents may provide higher willingness to pay estimates simply because they favor “good 

causes” such as environmental improvement. Second, while the study accounts for non-response bias, it may 

not employ the best available methods. As a result of these concerns, the Council recommended that 

residential visibility be omitted from the overall primary benefits estimate. (U.S. EPA-SAB, 1999) 14 Loehman et al. (1985) and Brookshire et al. (1979) were subsequently published in peer-reviewed journals (see 

Loehman et al. (1994) and Brookshire et al. (1982). The Tolley et al. (1984) work was not published, but was 

subject to peer review during study development. 15 Recognizing potential fundamental issues associated with data collected in Cincinnati and Miami (e.g., see 

Chestnut et al. (1986) and Chestnut and Rowe (1990c), we do not include values for these cities in our analysis. 

θ

ρ ρ

ρ ρ = − −

−

( )

( ) . m WTP mZ0 Z1
6.A-18

where:

m = household income,

ρ = shape parameter (0.1),

θ = WTP parameter corresponding to the visibility at MSA,

Z0 = starting visibility, and

Z1 = visibility after change.

Where studies provide multiple estimates for visual range improvements for a single 

study city, we estimate one θ as the simple average of the θ calculated for each set of visual 

range improvements.

6.A.7 Putting It All Together: The Household Utility and WTP Functions

Given an estimate of θ, derived as shown in Section 6.A.4, and estimates of the γ’s and 

δ’s, derived as shown in Section 6.A.3, based on an assumed or estimated value of ρ, the utility 

and WTP functions for a household in any region are fully specified. We could therefore 

estimate the value to that household of visibility changes from any baseline level to any 

alternative level in the household’s residential area and/or at any or all of the Class I areas in 

the United States, in a way that is consistent with economic theory. In particular, the WTP of a 

household in the ith region and the nth residential area for any set of changes in the levels of 

visibility at in-region Class I areas, out-of-region Class I areas, and the household’s residential 

area is:

The national benefits associated with any suite of visibility changes would be calculated 

as the sum of these household WTPs for those changes. The benefit of any subset of visibility 

changes (e.g., changes in visibility only at Class I areas in California) can be calculated by setting 

all the other components of the WTP function to zero (that is, by assuming that all other 

visibility changes that are not of interest are zero). This is effectively the same as assuming that 

the subset of visibility changes of interest is the first or the only set of changes being valued by 

households. Estimating benefit components in this way will yield slightly upward biased 

estimates of benefits, because disposable income, m, is not being reduced by the WTPs for any 

prior visibility improvements. That is, each visibility improvement (e.g., visibility at Class I areas 

in the California) is assumed to be the first, and they cannot all be the first. The upward bias 

WTPni Z Q m m Z n Z n ik Q ik Q ik Q Q

k

N

jk jk jk

k

N

j i

i j

( , ) [ ( ) ( ) ( )] . / ∆ ∆ = − + − + − + − = ≠ =

∑ ∑∑ ρ ρ ρ ρ ρ ρ ρ ρ θ 0 1 γ 0 1 δ

1

0 1

1

1
6.A-19

should be extremely small, however, because all of the WTPs for visibility changes are very 

small relative to income.

Although we recognize that the approach described above is most consistent with 

economic theory, we have chosen to not use this function with income constraints on overall 

WTP. Instead, we simply add the total preference calibrated recreational visibility benefits to 

the preference-calibrated residential visibility benefits. Again, because all of the WTPs for 

visibility changes are very small relative to income, the upward bias should be extremely small.

6.A.8 Income Elasticity and Income Growth Adjustment for Visibility Benefits

Growth in real income over time is an important component of benefits analysis. 

Economic theory argues that WTP for most goods (such as environmental protection) will 

increase if real incomes increase. There is substantial empirical evidence that the income 

elasticity16 of WTP for health risk reductions is positive, although there is uncertainty about its 

exact value. Thus, as real income increases, the WTP for environmental improvements also 

increases. Although many analyses assume that the income elasticity of WTP is unit elastic (i.e., 

a 10% higher real income level implies a 10% higher WTP to reduce risk changes), empirical 

evidence suggests that income elasticity is substantially less than one and thus relatively 

inelastic. As real income rises, the WTP value also rises but at a slower rate than real income.

The effects of real income changes on WTP estimates can influence benefits estimates 

in two different ways: through real income growth between the year a WTP study was 

conducted and the year for which benefits are estimated, and through differences in income 

between study populations and the affected populations at a particular time. Empirical 

evidence of the effect of real income on WTP gathered to date is based on studies examining 

the former. The Environmental Economics Advisory Committee (EEAC) of the Science Advisory 

Board (SAB) advised EPA to adjust WTP for increases in real income over time but not to adjust 

WTP to account for cross-sectional income differences “because of the sensitivity of making 

such distinctions, and because of insufficient evidence available at present” (U.S. EPA-SAB, 

2000a). A recent advisory by another committee associated with the SAB, the Advisory Council 

on Clean Air Compliance Analysis, has provided conflicting advice. While agreeing with “the 

general principle that the willingness to pay to reduce mortality risks is likely to increase with 

growth in real income (U.S. EPA-SAB, 2004)” and that “The same increase should be assumed 

for the WTP for serious nonfatal health effects (U.S. EPA-SAB, 2004),” they note that “given the 

 16 Income elasticity is a common economic measure equal to the percentage change in WTP for a 1% change in 

income.
6.A-20

limitations and uncertainties in the available empirical evidence, the Council does not support 

the use of the proposed adjustments for aggregate income growth as part of the primary 

analysis (U.S. EPA-SAB, 2004).” Until these conflicting advisories have been reconciled, EPA will 

continue to adjust valuation estimates to reflect income growth using the methods described 

below, while providing sensitivity analyses for alternative income growth adjustment factors.

We assume that the WTP for improved visibility would increase with growth in real 

income. The relative magnitude of the income elasticity of WTP for visibility compared with 

those for health effects suggests that visibility is not as much of a necessity as health, thus, WTP 

is more elastic with respect to income.

Details of the general procedure to account for projected growth in real U.S. income 

between 1990 and 2020 can be found in Kleckner and Neumann (1999). Specifically, we use the 

elasticity for visibility benefits provided in Chestnut (1997).

In addition to elasticity estimates, projections of real gross domestic product (GDP) and 

populations from 1990 to 2020 are needed to adjust benefits to reflect real per capita income 

growth. We used projections of real GDP provided in Kleckner and Neumann (1999) for the 

years 1990 to 2010.17 We used projections of real GDP provided by Standard and Poor’s (2000) 

for the years 2010 to 2020.18 Visibility benefits are adjusted by multiplying the unadjusted 

benefits by the appropriate adjustment factor.

6.A.9 Summary of Parameters

In Tables 6.A-3 through 6.A-6, we provide the parameters used to calculate recreational 

and residential visibility benefits.

 17 U.S. Bureau of Economic Analysis, Table 2A (available at http://www.bea.doc.gov/bea/dn/0897nip2/ tab2a.htm.) 

and U.S. Bureau of Economic Analysis, Economics and Budget Outlook. Note that projections for 2007 to 2010 

are based on average GDP growth rates between 1999 and 2007. 18 In previous analyses, we used the Standard and Poor’s projections of GDP directly. This led to an apparent 

discontinuity in the adjustment factors between 2010 and 2011. We refined the method by applying the 

relative growth rates for GDP derived from the Standard and Poor’s projections to the 2010 projected GDP 

based on the Bureau of Economic Analysis projections.
6.A-21

Table 6.A-3. Mean Annual Household WTP for Changes in Visual Range for Recreational 

Visibility (1990$)a

Region

WTP

In-region

WTP 

Out-of-region

Starting Visual 

Range (miles)

Ending Visual 

Range (miles)

Study Household 

Income

California $66.41 $43.85 90 125

$80.19 $53.88 90 150 $48,759

$71.42 $51.37 45 90

Southwest $50.12 $45.11 155 200

$72.67 $55.13 155 250 $48,759

$61.40 $48.87 115 155

Southeast $66.41 $35.08 25 50

$82.70 $53.88 25 75 $48,759

$75.18 $47.61 10 25

a Based on Chestnut (1997) and adjusted for study sample income and currency year

Table 6.A-4. Region-Specific Parameters for Recreational Visibility Benefitsa

Region Optimal γ Optimal δ

California 0.00517633 0.003629603

Southwest 0.006402706 0.005092572

Southeast 0.003552379 0.002163346

Northwest 0.001172669 0.000823398

Northern Rockies 0.005263445 0.004176339

Rest of U.S. 0.001211215 0.000738149

a Calculated using methodology described in sections 6.A.3 through 6.A.4
6.A-22

Table 6.A-5. Mean Annual Household WTP for Changes in Visual Range for Residential 

Visibility

City

WTP in 

Original 

Year’s $

Starting 

Visual 

Range 

(miles)

Ending 

Visual 

Range 

(miles)

Study 

Household 

Income

Year of 

Original 

Data

θ if ρ = 0.1 

(1990$, 

1990 

income)

θ if ρ = 

0.1 

(Simple 

Average)

Atlanta

(Tolley et al., 1984)

$188 12 22 $19,900a 1982 0.033446

0.021316

$281 12 32 $19,900a 1982 0.031661

$82 12 22 $27,600d 1984 0.010738

$119 12 32 $27,600d 1984 0.009417

Boston

(Tolley et al., 1984)

$139 18 28 $25,000a 1982 0.026636

0.022843

$171 18 38 $25,000a 1982 0.019049

Chicago

(Tolley et al., 1984)

$202 9 18 $30,000b 1981 0.022313

0.015480

$269 9 30 $30,000b 1981 0.016696

$121 10 20 $29,400d 1984 0.013180

$144 10 30 $29,400d 1984 0.009732

Denver

(Tolley et al., 1984)

$115 50 60 $32,000c 1984 0.038558

0.033181

$154 50 70 $32,000c 1984 0.027803

Los Angeles

(Brookshire et al., 

1979)

$43 2 12 $15,200d 1978 0.003866

$116 2 28 $15,200 0.007428 d 1978 0.006716

$71 12 28 $15,200d 1978 0.011702

Mobile

(Tolley et al., 1984)

$168 10 20 $20,200a 1982 0.026078

0.022480

$197 10 30 $20,200a 1982 0.018882

San Francisco

(Loehman et al., 1985)

$71 16.3 18.6 $26,100c 1980 0.045307 0.045307

Washington, DC

(Tolley et al., 1984)

$238 15 25 $27,500a 1982 0.036866

0.032335

$303 15 35 $27,500a 1982 0.027804

a See Chestnut et al. (1986), pages 5-5 through 5-10.

b See Tolley et al., (1984), page 127.

c See Loehman et al. (1985), page 38.

d Historical median income data by MSA from U.S. Census (1990).
6.A-23

Table 6.A-6. Parameters for Income Growth Adjustment for Visibility Benefits

Adjustment Step Parameter Estimate

Central Estimate of Elasticity a 0.90

Adjustment Factor Used to Account for Projected Real Income Growth in 2020b 1.517

a Derivation of estimates can be found in Kleckner and Neumann (1999) and Chestnut (1997).

b Based on elasticity values reported in Table 5-3, U.S. Census population projections, and projections of real GDP 

per capita.

6.A.10 References

Abt Associates, Inc. 2010. Environmental Benefits and Mapping Program (Version 4.0). 

Bethesda, MD. Prepared for U.S. Environmental Protection Agency Office of Air Quality 

Planning and Standards. Research Triangle Park, NC. Available on the Internet at 

<http://www.epa.gov/air/benmap>.

Brookshire, D.S., R.C. d’Arge, W.D. Schulze and M.A. Thayer. 1979. Methods Development for 

Assessing Tradeoffs in Environmental Management, Vol. II: Experiments in Valuing NonMarket Goods: A Case Study of Alternative Benefit Measures of Air Pollution Control in 

the South Coast Air Basin of Southern California. Prepared for the U.S. Environmental 

Protection Agency, Office of Research and Development. Available on the Internet at 

<http://yosemite.epa.gov/ee/epa/eerm.nsf/vwAN/EE-0271B-1.pdf/$file/EE-0271B1.pdf>.

Brookshire, D.S., Thayer, M.A., Schulze, W.D. & D’Arge, R.C. 1982. “Valuing Public Goods: A 

Comparison of Survey and Hedonic Approaches.” The American Economic Review. 72(1): 

165-177.

Chestnut, L.G. 1997. Draft Memorandum: Methodology for Estimating Values for Changes in 

Visibility in National Parks. Prepared for Office of Policy, Planning and Evaluation, May. 

Available on the Internet at 

<http://www.epa.gov/ttn/ecas/regdata/Benefits/background/chestnut1997.pdf>.

Chestnut, L.G., and R.D. Rowe. 1990. “A New National Park Visibility Value Estimates.” In 

Visibility and Fine Particles, Transactions of an AWMA/EPA International Specialty 

Conference, C.V. Mathai, ed. Air and Waste Management Association, Pittsburgh. 

Chestnut, L.G., R.D. Rowe and J. Murdoch. 1986. Review of ‘Establishing and Valuing the Effects 

of Improved Visibility in Eastern United States.’ Prepared for the U.S. Environmental 

Protection Agency. October. Available on the Internet at 

<http://www.epa.gov/ttn/ecas/regdata/Benefits/background/chestnut1986.pdf>.
6.A-24

Kleckner, N., and J. Neumann. 1999. Recommended Approach to Adjusting WTP Estimates to 

Reflect Changes in Real Income. Memorandum to Jim Democker, U.S. EPA/OPAR. June. 

Available on the Internet at <http://www.epa.gov/ttn/ecas/regdata/Benefits/

background/klecknerandneumann1999.pdf>.

Loehman, E.T., D. Boldt, K. Chaikin. 1985. Measuring the Benefits of Air Quality Improvements

in the San Francisco Bay Area. From Methods Development for Environmental Control 

Benefits Assessment, Volume IV. Prepared for the U.S. Environmental Protection 

Agency, Office of Policy, Planning and Evaluation, September. Grant #R805059-01-0 

Available on the Internet at <http://yosemite.epa.gov/ee/epa/eerm.nsf/ 

vwGA/e85705387833398f8525644d0053bdd0!OpenDocument#_Section6>.

Loehman, E.T., S. Park, and D. Boldt. 1994. “Willingness to Pay for Gains and Losses in Visibility 

and Health.” Land Economics 70(4): 478-498.

McClelland, G., W. Schulze, D. Waldman, J. Irwin, D. Schenk, T. Stewart, L. Deck and M. Thayer. 

1993. Valuing Eastern Visibility: A Field Test of the Contingent Valuation Method. 

Prepared for U.S. Environmental Protection Agency, Office of Policy, Planning and 

Evaluation. September. Available on the Internet at 

<http://yosemite.epa.gov/ee/epa/eerm.nsf/vwAN/EE-0008-1.pdf/$file/EE-0008-1.pdf >.

Pitchford, M.L., and W.C. Malm. 1994. “Development and Applications of a Standard Visual 

Index.” Atmospheric Environment 28(5):1049-1054.

Sisler, J.F. 1996. Spatial and Seasonal Patterns and Long Term Variability of the Composition of 

the Haze in the United States: An Analysis of Data from the IMPROVE Network. Colorado 

State University, Cooperative Institute for Research in the Atmosphere (CIRA), ISSN 

0737-5352-32. Fort Collins, CO. July. Available on the Internet at <http://vista.cira. 

colostate.edu/improve/Publications/Reports/1996/PDF/TBLCON1.96.pdf>.

Smith, V.K., G. Van Houtven, and S.K. Pattanayak. 2002. “Benefit Transfer via Preference 

Calibration.” Land Economics 78:132-152.

Tolley, G., A. Randall, G. Blomquist, M. Brien, R. Fabian, G. Fishelson, A. Frankel, M. Grenchik, J. 

Hoehn, A. Kelly, R. Krumm, E. Mensah, and T. Smith. 1984. Establishing and Valuing the 

Effects of Improved Visibility in Eastern United States. Prepared for U.S. Environmental 

Protection Agency, Office of Policy, Planning and Evaluation. March. U.S. Environmental 

Protection Agency Grant #807768-01-0. Available on the Internet at 

<http://yosemite.epa.gov/ee/epa/eerm.nsf/vwAN/EE-0003-01.pdf/$file/EE-0003-

01.pdf>.

U.S. Census. 1990. “Table 1: Median Household Income by Metropolitan Statistical Areas 

(MSA): 1969, 1979, and 1989.” 1970, 1980, and 1990 Censuses of Population and 

Housing. Income Statistics Branch/HHES Division. Available on the Internet at 

<http://www.census.gov/hhes/www/income/data/historical/metro/msa1.html>.
6.A-25

U.S. Environmental Protection Agency—Science Advisory Board (U.S. EPA-SAB). 1999. The Clean 

Air Act Amendments (CAAA) Section 812 Prospective Study of Costs and Benefits (1999): 

Advisory by the Advisory Council on Clean Air Compliance Analysis: Costs and Benefits of 

the CAAA. EPA-SAB-COUNCIL-ADV-00-002. October. Available on the Internet at 

<http://yosemite.epa.gov/sab/sabproduct.nsf/E992F918DF32131A852571B9004571F7/

$File/coua0002.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2011b. The Benefits and Costs of the Clean Air 

Act 1990 to 2020: EPA Report to Congress. Office of Air and Radiation, Washington, DC. 

March. Available on the Internet at 

<http://www.epa.gov/air/sect812/feb11/fullreport.pdf>.

U.S. Environmental Protection Agency (U.S. EPA). 2000. Guidelines for Preparing Economic 

Analyses. EPA 240-R-00-003. National Center for Environmental Economics, Office of 

Policy Economics and Innovation. Washington, DC. September. Available on the Internet 

at <http://yosemite.epa.gov/ee/epa/eed.nsf/webpages/Guidelines.html/ 

$file/cover.pdf>.
7-1

CHAPTER 7

ENGINEERING COST ANALYSIS

7.1 Synopsis

This chapter summarizes the data sources and methodology used to estimate the 

engineering costs of attaining the alternative, more stringent levels for the PM2.5 primary 

standard analyzed in this RIA. This chapter provides the estimates of the engineering costs of 

alternative annual standards of 13, 12, and 11 μg/m3 in conjunction with retaining the 24-hour 

standard of 35 μg/m3, as well as one of the alternative, more stringent annual standards 

(11 μg/m3) in conjunction with an alternative, more stringent 24-hour standard of 30 μg/m3

(referred to as 13/35, 12/35, 11/35, and 11/30). This chapter also presents engineering cost 

estimates for the control strategies outlined in Chapter 4. The cost discussion for known 

controls in Section 7.2.2 is followed by a presentation of estimates for the engineering costs of 

the additional (beyond known controls) tons of emission reductions that are needed to move to 

full attainment of the alternative standards analyzed; this estimation approach, discussed in 

Section 7.2.3, is referred to as extrapolated costs.

The engineering costs described in this chapter generally include the costs of 

purchasing, installing, operating, and maintaining the referenced technologies. For a variety of 

reasons, actual control costs may vary from the estimates EPA presents. As discussed 

throughout this document, the technologies and control strategies selected for analysis are 

illustrative of one way in which nonattainment areas could meet a revised standard. There are 

numerous ways to construct and evaluate potential control programs that would bring areas 

into attainment with alternative standards, and EPA anticipates that state and local 

governments will consider programs that are best suited for local conditions. Furthermore, 

based on past experience, EPA believes that it is reasonable to anticipate that the marginal cost 

of control will decline over time due to technological improvements and more widespread 

adoption of previously considered niche control technologies.1 Also, EPA recognizes the 

extrapolated portion of the engineering cost estimates reflects substantial uncertainty about 

which sectors, and which technologies, might become available for cost-effective application in 

the future. 

The engineering cost estimates are limited in their scope. This analysis focuses on the 

emission reductions needed for attainment of a range of alternative revised standards, not 

 1 See Chapter 4, Section 4.3 for additional discussion of uncertainties associated with predicting technological 

advancements that may occur between now and 2020.
7-2

implementation of a final revised standard. EPA understands that some states will incur costs 

both designing State Implementation Plans (SIPs) for and implementing new control strategies 

to meet the revised standard. However, EPA does not know what specific actions states will 

take to design their SIPs to meet the revised standards, therefore we do not present estimated 

costs that government agencies may incur for managing the requirement, implementing these 

(or other) control strategies, or for offering incentives that may be necessary to encourage the 

implementation of specific technologies, especially for technologies that are not necessarily 

market driven. This analysis does not assume specific control measures that would be required 

in order to implement these technologies on a regional or local level.

7.2 PM2.5 Engineering Costs

7.2.1 Data and Methods—Identified Control Costs (non-EGU Point and Area Sources)

After designing the hypothetical control strategy using the methodology discussed in 

Chapter 4, EPA used the Control Strategy Tool2 (CoST) to estimate engineering control costs for 

non-EGU point and area sources.3 CoST calculates engineering costs using one of three 

different methods: (1) by multiplying an average annualized cost-per-ton estimate against the 

total tons of a pollutant reduced to derive a total cost estimate; (2) by calculating cost using an 

equation that incorporates key plant information; or (3) by using both cost-per-ton and cost 

equations. Most control cost information within CoST was developed based on the cost-per-ton 

approach because estimating engineering costs using an equation requires more data, and 

parameters used in other non-cost-per-ton methods may not be readily available or broadly 

representative across sources within the emissions inventory. The costing equations used in 

CoST require either plant capacity or stack flow to determine annual, capital and/or operating 

and maintenance (O&M) costs. Capital costs are converted to annual costs using the capital 

recovery factor (CRF).4 Where possible, cost calculations are used to calculate total annual 

control cost (TACC), which is a function of capital costs (CC) and O&M costs. The CRF 

incorporates the interest rate and equipment life (in years) of the control equipment. Operating 

costs are calculated as a function of annual O&M and other variable costs. The resulting TACC 

equation is TACC = (CRF * CC) + O&M.

 2 The Control Strategy Tool recently underwent peer review by an ad hoc panel of experts. Responses to the peer 

review are currently under development and will be available by final promulgation of this rule. 3 Area sources are not necessarily non-urban sources. 4 The capital recovery factor formula is expressed as [r*(1+r)^n/(1+r)^n -1]. Where r is the real rate of interest and 

n is the number of time periods. For more information on this cost methodology and the CoST, please refer to 

the documentation at http://www.epa.gov/ttn/CoST, the EPA Air Pollution Control Cost Manual found at 

http://epa.gov/ttn/catc/products.html#cccinfo, and EPA’s Guidelines for Preparing Economic 

Analyses, Chapter 6 found at http://yosemite.epa.gov/ee/epa/eed.nsf/webpages/Guidelines.html#download.
7-3

Engineering costs will differ based upon quantity of emissions reduced, plant capacity, 

or stack flow, which can vary by the emissions inventory year. Engineering costs will also differ 

in nominal terms by the year the costs are calculated for (i.e., 1999$ versus 2006$).5 For capital 

investment, in order to attain standards in 2020 we assume capital investment occurs at the 

beginning of 2020. We make this simplifying assumption because we do not know what all firms 

making capital investments will do and when they will do it. For 2020, our estimate of 

annualized costs includes annualized capital and O&M costs for those controls included in our 

identified control strategy analysis. Our engineering cost analysis uses the equivalent uniform 

annual costs (EUAC) method, in which annualized costs are calculated based on the equipment 

life for the control measure along with the interest rate incorporated into the CRF. Annualized 

costs represent an equal stream of yearly costs over the period the control technology is 

expected to operate. We make no presumption of additional capital investment in years 

beyond 2020. The EUAC method is discussed in detail in the EPA Air Pollution Control Cost 

Manual.6 Applied controls and their respective engineering costs are provided in the PM NAAQS 

docket.

7.2.2 Identified Control Costs

In this section, we provide engineering cost estimates for the control strategies 

identified in Chapter 4 that include control technologies on non-EGU point sources and area 

sources. Engineering costs generally refer to the capital equipment expense, the site 

preparation costs for the application, and annual operating and maintenance costs. Note that 

the application of these control strategies results in some, but not all, geographic areas 

reaching attainment for the alternative PM2.5 standards.

Because we obtain control cost data from many sources, we are not always able to 

obtain consistent data across original data sources.7 If disaggregated control cost data is 

unavailable (i.e., where capital, equipment life value, and O&M costs are not separated out), 

EPA typically assumes that the estimated control costs are annualized using a 7 percent 

discount rate. When disaggregated control cost data is available (i.e., where capital, equipment 

life value, and O&M costs are explicit) we can recalculate costs using a 3 percent discount rate. 

For non-EGU point source controls, some disaggregated data is available and we were able to 

calculate costs at both 3 and 7 percent discount rates for that control cost data. For the 12/35, 

 5 The engineering costs will not be any different in real (inflation-adjusted) terms if calculated in 2006 versus otheryear dollars, if the other-year dollars are properly adjusted. For this analysis, all costs are reported in real 2006 

dollars. 6 http://epa.gov/ttn/catc/products.html#cccinfo

7 Data sources can include states and technical studies, which do not typically include the original data source.
7-4

11/35, and 11/30 alternative standards approximately 31 percent, 33 percent, and 29 percent, 

respectively, of known control costs are disaggregated at a level that could be discounted at 3 

percent. Because we do not have disaggregated control cost data for any area source controls, 

total annualized costs are assumed to be calculated using a 7 percent discount rate. See Table 

7-1 for a summary of sectors, control costs, and discount rates used.

Table 7-1. Summary of Sectors, Control Costs, and Discount Rates for Known Control Costs

(millions of 2006$)a

Alternative 

Standard

Emissions Sector Known Control Costs (Millions of 2006$)

7 Percent 

Discount Rate b

Partial Control 

Cost at 3 Percent 

Discount Rate c

3 Percent Discount Rate 

(3 Percent & 7 Percent 

Discount Rates Combined) d

13/35 non-EGU Point Sources — — —

Area Sources — — —

Total — — —

12/35 non-EGU Point Sources $0.098 $0.057 $0.061

Area Sources $0.210 — $0.210

Total $0.31 $0.057 $0.27

11/35 non-EGU Point Sources $25 $16 $24

Area Sources $28 — $28

Total $53 $16 $52

11/30 non-EGU Point Sources $46 $25 $42

Area Sources $54 — $54

Total $100 $25 $96 a All estimates rounded to two significant figures.

b All non-EGU point source costs and all area source costs are included in this column and are assumed to be 

calculated at a 7 percent discount rate.

c This column includes the non-EGU point source costs that we were able to calculate at a 3 percent rate and no 

area source costs. The non-EGU point source costs calculated at a 3 percent rate are those for which we have 

disaggregated control cost data.

d Our known control costs discounted at a 3 percent rate are a combination of area source costs and non-EGU 

point source costs discounted at a 7 percent rate only and non-EGU point source costs discounted at 3 percent 

when disaggregated control cost data is available.

The total annualized cost of control in each sector in the control scenario is summarized 

by region in Table 7-2. Table 7-2 includes annualized control costs to allow for comparison 

across regions and between costs and benefits. These numbers reflect the engineering costs 

annualized at discount rates of 3 percent and 7 percent, consistent with the guidance provided 

in the Office of Management and Budget’s (OMB) (2003) Circular A-4. However, it is important 

to note that it is not possible to estimate both 3 percent and 7 percent discount rates for each 

individual facility.
7-5

In this RIA, non-EGU point sources were the only sources with available data to perform 

a sensitivity analysis of our annualized control costs to the choice of interest rate. As such, the 3 

percent column in Table 7-2 reflects the sum of some non-EGU point sources at a 3 percent 

discount rate, some non-EGU point sources at a 7 percent discount rate, and the area sources 

at a 7 percent discount rate. The 3 percent column represents a slight overestimate because 

some non-EGU point sources and area sources are included using a 7 percent discount rate.8

With the exception of the 3 percent Total Annualized Cost estimate in Table 7-2, engineering 

cost estimates presented throughout this and subsequent chapters are based on a 7 percent 

discount rate.

Table 7-2. Partial Attainment Known Control Costs in 2020 for Alternative Standards 

Analyzeda (millions of 2006$)a

Alternative 

Standard

Region Known Controls

3%b 7%

13/35c East — —

West — —

California — —

Total — —

12/35 East $0.061 $0.098

West $0.21 $0.21

Californiac — —

Total $0.27 $0.31

11/35 East $46 $48

West $3.0 $3.0

California $3.0 $3.0

Total $52 $53

11/30 East $46 $48

West $31 $33

California $19 $19

Total $96 $100

a Estimates are rounded to two significant figures, as such numbers may not sum down columns.

 8 In these analyses, the discount rates refer to the rate at which capital costs are annualized. A higher discount, or 

interest, rate results in a larger annualized cost of capital estimate.
7-6

b Because we obtain control cost data from many sources, we are not always able to obtain consistent data across 

original data sources. Where disaggregated control cost data is available (i.e., where capital, equipment life 

value, and O&M costs are explicit) we can calculate costs using a 3 percent discount rate. Therefore the cost 

estimate provided here is a summation of costs at 3 percent and 7 percent discount rates.

c All known controls were applied in the baseline.

The total annualized engineering costs associated with the application of known 

controls, incremental to the baseline and using a 7 percent discount rate, are approximately 

$310,000 for an alternative annual standard of 12/35, $53 million for an 11/35 alternative 

standard, and $100 million for an 11/30 alternative standard. In addition, it is important to note 

there is no partial attainment known control costs for a 13/35 alternative standard.9

7.2.3 Extrapolated Costs

This section presents the methodology and results of the extrapolated engineering cost 

calculations for attainment of alternative PM2.5 standards of 13/35, 12/35, 11/35, and 11/30. All 

costs presented for the illustrative control strategies are calculated incrementally from the 

current PM2.5 standard of 15/35, therefore, any additional emission reductions needed to attain 

the current 24-hour standard of 35 μg/m3 are part of the baseline analysis and not presented 

here. Note that the extrapolated costs don’t account for cost differences between reducing 

additional tons by emissions source sector.

As mentioned earlier in this chapter, the application of the modeled control strategy 

was not successful in reaching nationwide attainment for these alternative PM2.5 standards. 

Because some areas remained in nonattainment, the engineering costs detailed in Section 7.2.2 

represent the costs of partial attainment for PM2.5 standards of 13/35, 12/35, 11/35, and 11/30. 

For each alternative standard and geographic area that cannot reach attainment with known 

controls, we estimated, in a least-cost way, the additional emission reductions needed for PM2.5 

and its precursors, NOx and SO2, to attain the standard. To generate estimates of the costs and 

benefits of meeting alternative standards, EPA has assumed the application of unspecified 

future controls that make possible the emission reductions needed for attainment in 2020. By 

definition, no cost data currently exists for unidentified future technologies or innovative 

strategies. EPA used two methodologies for estimating the costs of unspecified future controls: 

a fixed-cost methodology and a hybrid methodology. The fixed-cost methodology is more 

straight forward and transparent than the hybrid methodology. In the hybrid methodology, the 

coefficient for the X2 term can be difficult to estimate and if it is zero, the functional form 

 9 Only one county (Riverside County, CA) exceeded the 13/35 alternative standard. All known controls were used in 

the baseline analysis for this county; therefore there are no known control costs for this standard. Total costs 

for 13/35 are represented by extrapolated costs only—see Table 7.3 below.
7-7

becomes the same as the fixed-cost methodology’s functional form. Additional discussion of 

the functional form associated with the hybrid methodology is in Appendix 7.A. Both 

approaches assume that innovative strategies and new control options make possible the 

emissions reductions needed for attainment by 2020. The fixed-cost methodology uses a 

$15,000/ton estimate for each ton of PM2.5, SO2, andNOx reduced, and the hybrid approach is 

similar to the hybrid approach used for the 2008 Ozone NAAQS RIA cost analysis. The 

$15,000/ton amount is commensurate with that used in the 1997 Ozone Regulatory Impact 

Analysis and is consistent with what an advisory committee to the Section 812 second 

prospective analysis on the Clean Air Act Amendments suggested. In Section 7.A.2.1 we conduct 

sensitivity analysis on the fixed-cost estimate of $15,000/ton. The fixed-cost methodology was 

preferred by EPA’s Science Advisory Board over two other options, including a marginal-costbased approach. 

“When assigning costs to unidentified measures, the Council suggests that a simple, 

transparent method that is sensitive to the degree of uncertainty about these costs is best. 

Of the three approaches outlined, assuming a fixed cost/ton appears to be the simplest 

and most straightforward. Uncertainty might be represented using alternative fixed costs 

per ton of emissions avoided.”

EPA requests comments or suggestions on all aspects of the methodologies for estimating the 

costs of unspecified future controls to provide illustrative estimates of NAAQS costs, including 

choice of functional forms of the equations, initial parameter estimates, and the initial fixedcost estimate of $15,000/ton.

In Appendix 4.A we include estimates of the relationship between additional emission 

reductions for each pollutant and air quality improvements. In this chapter we present 

estimates of the costs for each additional emission reduction for each pollutant and geographic 

area. The mix of pollutants varies by area, because each area has different amounts of known 

controls, different additional air quality improvements required, and different amounts of 

uncontrolled emissions remaining. 

Estimating engineering costs for emission reductions needed beyond those from known 

controls to reach attainment in 2020 is inherently a challenging exercise. As described later in 

this chapter, our experience with Clean Air Act implementation shows that technological 

advances and development of innovative strategies can reduce emissions and reduce the costs 

of emerging technologies over time. Technological change may provide new possibilities for 

controlling emissions as well as reducing the cost of known controls through technological 
7-8

improvements or higher control efficiencies. EPA requests comment on the likelihood that new 

technologies that control direct PM2.5 and its precursors will become available between now 

and 2020.

Because three different pollutants are involved, there are many different combinations 

of pollutant reductions that would result in the required air quality improvements. Early in our 

analysis we decided to use the hybrid-cost methodology to estimate the costs of the emission 

reductions needed from unknown controls. However, the hybrid methodology still has a 

number of important uncertainties, and its reliability for extrapolating costs has not been 

evaluated. While we applied the methodology to generate emission reduction estimates 

needed beyond known controls for the proposed PM2.5 standards and several alternatives, the 

degree of extrapolation for emissions reductions caused us to reconsider applying the hybrid 

methodology to obtain estimates of extrapolated costs. Consistent with an SAB 

recommendation, we use the fixed-cost per ton methodology to generate the estimates of 

extrapolated costs for emission reductions needed from unknown controls. We perform 

sensitivity analyses using both the alternative fixed cost per ton and the hybrid methodologies 

in Appendix 7.A 

As discussed in Chapter 4, we developed the emission reduction estimates for each 

alternative standard using the hybrid methodology. As a result, the emissions reductions that 

form the basis of the primary cost and benefit estimates may include a different mix of PM2.5

and SO2 emissions reductions than may have been identified as least cost had we employed the 

fixed-cost methodology to develop the emission reduction estimates. Using the fixed-cost 

methodology, the less expensive pollutant, for air quality improvements, to reduce will be 

selected until there are no remaining tons to reduce. Using the hybrid methodology, the less 

expensive pollutant to reduce will be selected until the marginal cost to reduce the next ton 

exceeds the marginal cost to reduce the next ton of an alternate pollutant. At that point, the 

methodology chooses a mix of pollutants to achieve the least-cost solution. Since the cost per 

ton is held constant in the fixed-cost methodology, the least-cost solution would select all 

available direct PM2.5 emissions reductions before selecting SO2 emissions reductions.10

Therefore, the hybrid methodology estimates PM2.5 emissions reductions lower than or equal 

 10 Because the marginal cost equation for each pollutant is expected to be less accurate for the very last portion of 

a pollutant in an area, and it is unlikely an area would reduce all anthropogenic emissions to zero on one 

pollutant prior to controlling others, we included the constraint that no more than 90% of the remaining 

emissions in an area for a given pollutant can be reduced from emission reductions beyond known control 

measures.
7-9

to the fixed-cost methodology and SO2 emission reductions higher than or equal to the fixedcost methodology. 

Because we used the hybrid methodology in selecting emissions reductions, the total 

cost estimate is higher than if we had selected needed emissions reductions using the fixedcost methodology. This is because the total number of tons identified and summed across 

pollutants under the hybrid methodology may be higher than the total number of tons needed 

under the fixed-cost methodology. For example, the hybrid methodology may choose to reduce 

direct PM2.5 by 15 tons of and SO2 by 8 tons, whereas the fixed-cost methodology may choose 

to reduce direct PM2.5 by 20 tons to obtain the same air quality improvement for an area. 

Applying the fixed cost-per-ton to the total reductions, the hybrid methodology would result in 

total costs of $345,000 (23 tons * $15,000/ton), and the fixed-cost methodology would result in 

total costs of $300,000 (20 tons * $15,000/ton).

Extrapolated cost estimates are provided using a 7 percent discount rate because 

known control measure information is available at 7 percent for all measures applied in this 

analysis. Table 7-3 provides the extrapolated cost estimates using the fixed-cost methodology 

described above, using a fixed cost-per-ton of $15,000/ton. The extrapolated costs estimate is 

$69 million dollars (2006$) for the 12/35 alternative standard.
7-10

Table 7-3. Fixed Costs by Alternative Standard Analyzeda (millions of 2006$)a

Alternative Standard Region

Fixed Cost Methodology

7%

13/35 East —

West —

California $2.9

Total $2.9

12/35 East —

West $3.3

California $65

Total $69

11/35 East $1.3

West $38

California $180

Total $220

11/30 East $21

West $79

California $190

Total $290

a Estimates are rounded to two significant figures.

Of note is the geographic distribution of extrapolated costs. For all of the alternative 

standards, the above costs indicate that California, as possibly expected, represents a 

significant portion of the extrapolated costs. For the 11/30, 11/35, 12/35, and 13/35 alternative 

standards, California represents 65 percent, 82 percent, 94 percent and 100 percent, 

respectively, of the extrapolated cost estimates. 

7.2.4 Total Cost Estimates

Table 7-4 presents a summary of the total national costs of attaining 13/35, 12/35, 

11/35, and 11/30 alternative standards in 2020. This summary includes the engineering costs 

presented above from the known controls analysis, as well as the extrapolated costs. As 

discussed in Section 7.2.2, costs for known controls for non-EGU point sources where capital 
7-11

cost and equipment life information were available were calculated at a 3 percent discount 

rate. Extrapolated costs were calculated at a 7 percent discount rate only. 

To calculate total cost estimates at a 3 percent discount rate and to include the 

extrapolated costs in those totals, we added the known control estimates at a 3 percent 

discount rate to the extrapolated costs at a 7 percent discount rate. To more clearly present the 

total cost calculations for both approaches, we include column labels in Table 7-4, e.g., A, B, 

and C. 

The costs associated with monitoring, reporting, and record keeping for affected 

sources are not included in these annualized cost estimates. Based on preliminary estimates 

prepared for the upcoming PM2.5 Implementation Rule Information Collection Request (ICR), 

EPA believes these costs are minor compared to the control costs.
7-12

Table 7-4. Total Costs by Alternative Standard Analyzed (millions of 2006$)a

Alternative 

Standard

Region Known Controls Fixed-Cost 

Methodology

Total Costs

Fixed-Cost Methodology

3% b

A

7%

B

7%

C

3%

(A+C)

7%

(B+C)

13/35 East — — — — —

West — — — — —

California — — $2.9 $2.9 $2.9

Total — — $2.9 $2.9 $2.9

12/35 East $0.061 $0.098 — $0.061 $0.098

West $0.21 $0.21 $3.3 $3.6 $3.6

California — — $65 $65 $65

Total $0.27 $0.31 $69 $69 $69

11/35 East $46 $48 $1.3 $47 $49

West $3.0 $3.0 $38 $41 $41

California $3 $3 $180 $180 $180

Total $52 $53 $220 $270 $270

11/30 East $46 $48 $21 $67 $69

West $31 $33 $79 $110 $110

California $19 $19 $190 $210 $210

Total $96 $100 $290 $390 $390

a Estimates are rounded to two significant figures, as such numbers may not sum down columns.

b Cost Estimates are not available at 3% for all control measures. Therefore the cost estimate provided here is a 

summation of costs at 3% and 7% discount rates.

7.3 Changes in Regulatory Cost Estimates over Time

Our analyses focus on controls for non-EGU and area sources. Future technology 

developments in sectors not analyzed here (e.g., EGUs) may be transferrable to non-EGU and 

area sources, making these sources more viable for achieving future attainment at a lower cost. 

These same future technology developments may also make the sectors not analyzed here 

(e.g., EGUs) more viable for achieving future attainment at a lower cost. There are many 

examples in which technological innovation and “learning by doing” have made it possible to 

achieve greater emission reductions than had been feasible earlier, or have reduced the costs 
7-13

of emission control in relation to original estimates. Studies have concluded that costs of some 

EPA programs have been less than originally estimated, due in part to EPA’s inability to predict 

and account for future technological innovation in regulatory impact analyses.11 Technological 

change will affect baseline conditions for our analysis. This change may lead to potential 

improvements in the efficiency with which firms produce goods and services; for example, firms 

may use less energy to produce the same quantities of output.

Constantly increasing marginal abatement costs are likely to induce the type of 

innovation that would result in lower costs than estimated in this chapter. By 2020, 

breakthrough technologies in control equipment could result in a downward shift in the 

marginal abatement cost curve for such equipment (Figure 7-1)12 as well as a decrease in its 

slope, reducing marginal costs per unit of abatement. In addition, elevated abatement costs 

may result in significant increases in the cost of production and would likely induce production 

efficiencies, in particular those related to energy inputs, which would lower emissions from the

production side. EPA requests comment on how marginal control costs for specific technology 

applications may have changed over the past 20 years.

Figure 7-1. Technological Innovation Reflected by Marginal Cost Shift

 11 Harrington et al. (2000) and previous studies cited by Harrington. Harrington, W., R.D. Morgenstern, and P. 

Nelson. 2000. “On the Accuracy of Regulatory Cost Estimates.” Journal of Policy Analysis and Management 

19(2):297-322. 12 Figure 7-1 shows a linear marginal abatement cost curve. It is possible that the shape of the marginal abatement 

cost curve is non-linear.

MC0 MC1

SO2 Reductions

Cost/

Ton

Induced Technology Shift

Slope =?0

Slope =?1

MCLONG
7-14

7.3.1 Examples of Technological Advances in Pollution Control

There are numerous examples of low-emission technologies developed and/or 

commercialized over the past 15 or 20 years, such as

 Selective catalytic reduction (SCR) and ultra-low NOx burners for NOx emissions

 Scrubbers, which achieve 95% and potentially greater SO2 control on boilers

 Sophisticated new valve seals and leak detection equipment for refineries and 

chemical plants

 Low- or zero-VOC paints, consumer products and cleaning processes

 Chlorofluorocarbon (CFC) free air conditioners, refrigerators, and solvents

 Water- and powder-based coatings to replace petroleum-based formulations

 Vehicles are much cleaner than believed possible in the late 1980s due to 

improvements in evaporative controls, catalyst design and fuel control systems for 

light-duty vehicles; and treatment devices and retrofit technologies for heavy-duty 

engines

 Idle-reduction technologies for engines, including truck stop electrification efforts

 Market penetration of gas-electric hybrid vehicles, and clean fuels

 The development of retrofit technology to reduce emissions from in-use vehicles 

and non-road equipment

These technologies were not commercially available 2 decades ago, and some did not 

even exist. Yet today, all of these technologies are on the market, and many are widely 

employed. Several are key components of major pollution control programs.

What is known as “learning by doing” or “learning curve impacts,” which is a concept 

distinct from technological innovation, have also made it possible to achieve greater emissions 

reductions than had been feasible earlier, or have reduced the costs of emission control in 

relation to original estimates. Learning curve impacts can be defined generally as the extent to 

which variable costs (of production and/or pollution control) decline as firms gain experience 

with a specific technology. Impacts such as these would manifest themselves as a lowering of 

expected costs for operation of technologies in the future below what they may have been.
7-15

The magnitude of learning curve impacts on pollution control costs has been estimated 

for a variety of sectors as part of the cost analyses done for the Draft Direct Cost Report for the 

second EPA Section 812 Prospective Analysis of the Clean Air Act Amendments of 1990.13 In 

that report, learning curve adjustments were included for those sectors and technologies for 

which learning curve data was available. A typical learning curve adjustment example is to 

reduce either capital or O&M costs by a certain percentage given a doubling of output from 

that sector or for that technology. In other words, capital or O&M costs will be reduced by 

some percentage for every doubling of output for the given sector or technology.

T.P. Wright, in 1936, was the first to characterize the relationship between increased 

productivity and cumulative production. He analyzed man-hours required to assemble 

successive airplane bodies. He suggested the relationship is a log linear function, since he 

observed a constant linear reduction in man-hours every time the total number of airplanes 

assembled was doubled. The relationship he devised between number assembled and assembly 

time is called Wright’s Equation (Gumerman and Marnay, 2004).14 This equation, shown below, 

has been shown to be widely applicable in manufacturing:

Wright’s Equation: CN = Co * Nb, (7.2)

where:

N = cumulative production

CN = cost to produce Nth unit of capacity

Co = cost to produce the first unit

b = learning parameter = ln (1-LR)/ln(2), where

LR = learning by doing rate, or cost reduction per doubling of capacity or output.

The percentage adjustments to costs can range from 5 to 20 percent, depending on the 

sector and technology. Learning curve adjustments were prepared in a memo by IEc supplied to 

US EPA and applied for the mobile source sector (both onroad and nonroad) and for application 

 13 E.H. Pechan and Associates and Industrial Economics, Direct Cost Estimates for the Clean Air Act Second Section 

812 Prospective Analysis: Draft Report, prepared for U.S. EPA, Office of Air and Radiation, February 2007.

Available at http://www.epa.gov/oar/sect812/mar07/direct_cost_draft.pdf. 14 Gumerman, Etan and Marnay, Chris. Learning and Cost Reductions for Generating Technologies in the National 

Energy Modeling System (NEMS), Ernest Orlando Lawrence Berkeley National Laboratory, University of 

California at Berkeley, Berkeley, CA. January 2004, LBNL-52559. 
7-16

of various EGU control technologies within the Draft Direct Cost Report.15 Advice received from 

the SAB Advisory Council on Clean Air Compliance Analysis in June 2007 indicated an interest in 

expanding the treatment of learning curves to those portions of the cost analysis for which no 

learning curve impact data are currently available. Examples of these sectors are non-EGU point 

sources and area sources. The memo by IEc outlined various approaches by which learning 

curve impacts can be addressed for those sectors. The recommended learning curve impact 

adjustment for virtually every sector considered in the Draft Direct Cost Report is a 10% 

reduction in O&M costs for two doublings of cumulative output, with proxies such as 

cumulative fuel sales or cumulative emission reductions being used when output data was 

unavailable.

For this RIA, we do not have the necessary data for cumulative output, fuel sales, or 

emission reductions for all sectors included in our analysis in order to properly generate control 

costs that reflect learning curve impacts. Clearly, the effect of including these impacts would be 

to lower our estimates of costs for our control strategies in 2020, but we are not able to include 

such an analysis in this RIA.

7.3.2 Influence on Regulatory Cost Estimates

Studies indicate that it is not uncommon for pre-regulatory cost estimates to be higher 

than later estimates, in part because of an inability to predict technological advances. Over 

longer time horizons, the opportunity for technical advances is greater.

7.3.2.1 Multi-Rule Study

Harrington et al. of Resources for the Future (RFF)16 conducted an analysis of the 

predicted and actual costs of 28 federal and state rules, including 21 issued by EPA and the 

Occupational Safety and Health Administration (OSHA), and found a tendency for predicted 

costs to overstate actual implementation costs. Costs were considered accurate if they fell 

within the analysis error bounds or if they fall within 25 percent (greater or less than) of the 

predicted amount. They found that predicted total costs were overestimated for 14 of the 28 

rules, while total costs were underestimated for only three rules. Differences can result 

because of quantity differences (e.g., overestimate of pollution reductions) or differences in 

per-unit costs (e.g., cost per unit of pollution reduction). Per-unit costs of regulations were 

 15 Industrial Economics, Inc. Proposed Approach for Expanding the Treatment of Learning Curve Impacts for the 

Second Section 812 Prospective Analysis: Memorandum, prepared for U.S. EPA, Office of Air and Radiation, 

August 13, 2007. 16 Harrington, W., R.D. Morgenstern, and P. Nelson. 2000. “On the Accuracy of Regulatory Cost Estimates.” Journal 

of Policy Analysis and Management 19(2):297-322.
7-17

overestimated in 14 cases, while they were underestimated in six cases. In the case of EPA 

rules, the Agency overestimated per-unit costs for five regulations, underestimated them for 

four regulations (three of these were relatively small pesticide rules), and accurately estimated 

them for four. Based on examination of eight economic incentive rules, “for those rules that 

employed economic incentive mechanisms, overestimation of per-unit costs seems to be the 

norm,” the study said. It is worth noting here that the controls applied for this NAAQS do not 

use an economic incentive mechanism. In addition, Harrington et al. also states that 

overestimation of total costs can be due to error in the quantity of emission reductions 

achieved, which would also cause the benefits to be overestimated. A 2010 update to this study 

by Harrington et al. of RFF showed that EPA and other regulatory agencies tend to overestimate 

the total costs of regulations; their estimates of the cost per-unit of pollution eliminated by 

regulations tend to be more accurate, however. Calculations of the total cost of regulation 

include not only the “unit costs” multiplied by the number of units of pollution avoided, but 

also estimates of the basic adjustment process and costs of change itself. Of the rules initially 

examined, 14 projected inflated total costs, while pre-regulation estimates were too low for 

only three rules. These exaggerated adjustment costs are often attributable to underestimates 

of the potential that technological change could minimize pollution abatement costs.

17

Based on the case study results and existing literature, the authors identified 

technological innovation as one of five explanations of why predicted and actual regulatory cost 

estimates differ: “Most regulatory cost estimates ignore the possibility of technological 

innovation ... Technical change is, after all, notoriously difficult to forecast ... In numerous case 

studies actual compliance costs are lower than predicted because of unanticipated use of new 

technology.”

It should be noted that many (though not all) of the EPA rules examined by Harrington 

et al. had compliance dates of several years, which allowed a limited period for technical 

innovation.

 17 Harrington, W, R Morgenstern, and P Nelson. “How Accurate Are Regulatory Cost Estimates?” Resources for the

Future, March 5, 2010. Available on the Internet at

http://www.rff.org/wv/Documents/HarringtonMorgensternNelson_regulatory%20estimates

.pdf.
7-18

7.3.2.2 Acid Rain SO2 Trading Program

Recent cost estimates of the Acid Rain SO2 trading program by RFF and MIT have been 

as much as 83 percent lower than originally projected by EPA.18 As noted in the RIA for the 

Clean Air Interstate Rule, the ex ante numbers in 1989 were an overestimate in part because of 

the limitation of economic modeling to predict technological improvement of pollution controls 

and other compliance options, such as fuel switching. The fuel switching from high-sulfur to 

low-sulfur coal was spurred by a reduction in rail transportation costs due to deregulation of 

rail rates during the 1990’s. Harrington et al. report that scrubbing turned out to be more 

efficient (95% removal vs. 80–85% removal) and more reliable (95% vs. 85% reliability) than 

expected, and that unanticipated opportunities arose to blend low- and high-sulfur coal in older 

boilers up to a 40/60 mixture, compared with the 5/95 mixture originally estimated.

Table 7-5. Phase 2 Cost Estimates

Phase 2 Cost Estimates

Ex ante estimates $2.7 to $6.2 billiona

Ex post estimates $1.0 to $1.4 billion

a 2010 Phase II cost estimate in 1995$.

7.3.2.3 EPA Fuel Control Rules

A 2002 study by two economists with EPA’s Office of Transportation and Air Quality19

examined EPA vehicle and fuels rules and found a general pattern that “all ex ante estimates 

tended to exceed actual price impacts, with the EPA estimates exceeding actual prices by the 

smallest amount.” The paper notes that cost is not the same as price, but suggests that a 

comparison nonetheless can be instructive.20 An example focusing on fuel rules is provided in 

Table 7-6.

 18 Carlson, Curtis, Dallas R. Burtraw, Maureen, Cropper, and Karen L. Palmer. 2000. “Sulfur Dioxide Control by 

Electric Utilities: What Are the Gains from Trade?” Journal of Political Economy 108(#6):1292-1326.

Ellerman, Denny. January 2003. Ex Post Evaluation of Tradable Permits: The U.S. SO2 Cap-and-Trade Program. 

Massachusetts Institute of Technology Center for Energy and Environmental Policy Research. 19 Anderson, J.F., and Sherwood, T., 2002. “Comparison of EPA and Other Estimates of Mobile Source Rule Costs to 

Actual Price Changes,” Office of Transportation and Air Quality, U.S. Environmental Protection Agency. 

Technical Paper published by the Society of Automotive Engineers. SAE 2002-01-1980. 20 The paper notes: “Cost is not the same as price. This simple statement reflects the fact that a lot happens 

between a producer’s determination of manufacturing cost and its decisions about what the market will bear in 

terms of price change.”
7-19

Table 7-6. Comparison of Inflation-Adjusted Estimated Costs and Actual Price Changes of 

EPA Fuel Control Rulesa

Inflation-adjusted Cost Estimates (c/gal) Actual Price 

Changes (c/gal)

EPA DOE API Other

Gasoline

Phase 2 RVP Control (7.8 RVP—

Summer) (1995$)

1.1 1.8 0.5

Reformulated Gasoline Phase 1 

(1997$)

3.1–5.1 3.4–4.1 8.2–14.0 7.4 (CRA) 2.2

Reformulated Gasoline Phase 2 

(Summer) (2000$)

4.6–6.8 7.6–10.2 10.8–19.4 12 7.2 (5.1, when 

corrected to 5yr 

MTBE price)

30 ppm sulfur gasoline (Tier 2) 1.7–1.9 2.9–3.4 2.6 5.7 (NPRA), 

3.1 (AIAM)

N/A

Diesel

500 ppm sulfur highway diesel 

fuel (1997$)

1.9–2.4 3.3 (NPRA) 2.2

15 ppm sulfur highway diesel 

fuel

4.5 4.2–6.0 6.2 4.2–6.1 

(NPRA)

N/A

a Anderson, J.F., and Sherwood, T., 2002. “Comparison of EPA and Other Estimates of Mobile Source Rule Costs to 

Actual Price Changes,” Office of Transportation and Air Quality, U.S. Environmental Protection Agency. Technical 

Paper published by the Society of Automotive Engineers. SAE 2002-01-1980.

Chlorofluorocarbon (CFC) Phase-Out: EPA used a combination of regulatory, marketbased (i.e., a cap-and-trade system among manufacturers), and voluntary approaches to phase 

out the most harmful ozone depleting substances. This was done more efficiently than either 

EPA or industry originally anticipated. The phase out for Class I substances was implemented 

4–6 years faster, included 13 more chemicals, and cost 30 percent less than was predicted at 

the time the 1990 Clean Air Act Amendments were enacted.21

The Harrington et al. study states, “When the original cost analysis was performed for 

the CFC phase-out it was not anticipated that the hydrofluorocarbon HFC-134a could be 

substituted for CFC-12 in refrigeration. However, as Hammit22 notes, ‘since 1991 most new U.S. 

 21 Holmstead, Jeffrey, 2002. “Testimony of Jeffrey Holmstead, Assistant Administrator, Office of Air and Radiation, 

U.S. Environmental Protection Agency, Before the Subcommittee on Energy and air Quality of the committee 

on Energy and Commerce, U.S. House of Representatives, May 1, 2002, p. 10. 22 Hammit, J.K. (2000). “Are the costs of proposed environmental regulations overestimated? Evidence from the 

CFC phase out.” Environmental and Resource Economics, 16(#3): 281-302.
7-20

automobile air conditioners have contained HFC-134a (a compound for which no commercial 

production technology was available in 1986) instead of CFC-12” (p.13). He cites a similar story 

for HCFRC-141b and 142b, which are currently substituting for CFC-11 in important foamblowing applications.”

Additional examples of decreasing costs of emissions controls include: SCR catalyst costs 

decreasing from $11k-$14k/m3 in 1998 to $3.5k-$5k/m3 in 2004, and improved low NOx burners 

reduced emissions by 50% from 1993–2003 while the associated capital cost dropped from $25-

$38/kW to $15/kW.23 Also, FGD scrubber capital costs have been estimated to have decreased 

by more than 50 percent from 1976 to 2005, and the O&M costs decreased by more than 50% 

from 1982 to 2005. Many process improvements contributed to lowering the capital costs, 

especially improved understanding and control of process chemistry, improved materials of 

construction, simplified absorber designs, and other factors that improved reliability.24

We cannot estimate the precise interplay between EPA regulation and technology 

improvement, but it is clear that a priori cost estimation often results in overestimation of costs 

because changes in technology (whatever the cause) make less costly control possible.

7.3.3 Influence of Regulation on Technological Change

We cannot estimate the interplay between EPA regulation and technology improvement 

but have reason to believe it may be significant. There is emerging research on technologyforcing polices (i.e., where a regulator specifies a policy standard that cannot be met with 

existing technology or met with existing technology but not at an acceptable cost, and over 

time market demand will provide incentives for industry to develop the appropriate 

technology). This is illustrated by Gerard and Lave (2005). Therein, they demonstrate through a 

careful policy history that the 1970 CAA legislated dramatic improvements in the reduction of 

emissions for 1975 and 1976 automobiles. Those mandated improvements went beyond the 

capabilities of existing technologies. But the regulatory pressure “pulled” forth or “forced” 

catalytic converting technology in 1975.

Work for EPA by RTI in 2011 studied the relationship between patents and the SO2 capand-trade program. This preliminary, non-peer reviewed study seems to indicate that patents 

 23 ICF Consulting. October 2005. The Clean Air Act Amendment: Spurring Innovation and Growth While Cleaning 

the Air. Washington, DC. Available at http://www.icfi.com/Markets/Environment/doc_files/caaa-success.pdf. 24 Yeh, Sonia and Rubin, Edward. February 2007. “Incorporating Technological Learning in the Coal Utility 

Environmental Cost (CUECost) Model: Estimating the Future Cost Trends of SO2, NOx, and Mercury Control 

Technologies.” Prepared for ARCADIS Geraghty and Miller, Research Triangle Park, NC 27711. Available at 

http://steps.ucdavis.edu/People/slyeh/syeh-resources/Drft%20Fnl%20Rpt%20Lrng%20for%20CUECost_v3.pdf.
7-21

may be related to SO2 regulatory actions and drops in the long-term SO2 allowance price. Popp 

(2003) and Keohane (2002) have both provided empirical evidence that Title IV led to induced 

technological change. Popp provides evidence that since Title IV there has been technological 

innovations that have improved the removal efficiency of scrubbers. Keohane provides 

evidence that fossil-fuel fired electric utilities that were subject to Title IV were, for a given 

increase in the cost of switching to low sulfur coal, more likely to install a scrubber.

7.4 Uncertainties and Limitations

EPA bases its estimates of emission control costs on the best available information from 

available engineering studies of air pollution controls and developed a reliable modeling 

framework for analyzing the cost, emission changes, and other impacts of regulatory controls. 

However, our cost analysis is subject to uncertainties and limitations, which we document on a 

qualitative basis in Table 7-7 below. For additional discussion of how we assess uncertainty, see 

Section 5.5.7.

Table 7-7. Summary of Qualitative Uncertainty for Modeling Elements of PM Engineering 

Costs

Potential Source of Uncertainty

Direction 

of 

Potential 

Bias

Magnitude of 

Impact on 

Monetized 

Costsa

Degree of 

Confidence 

in Our 

Analytical 

Approachb

Ability to 

Assess 

Uncertaintyc

Uncertainties Associated with Engineering Costs

Engineering Cost Estimates

▪ Capital recovery factor estimates (7% and 3%)

▪ Estimates of private compliance cost

▪ Increased advancement in control 

technologies as well as reduction in costs over 

time

▪ Cost estimates for PM10

Both Medium-high Medium Tier 2

Unquantified Costs

▪ Costs of federal and state administration of SIP 

program, as well as permitting costs.

▪ Transactional costs

Low Medium Medium Tier 1

Extrapolated Costs Both High Low Tier 1

a Magnitude of Impact

High—If error could influence the total costs by more than 25%

Medium—If error could influence the total costs by 5% -25%

Low—If error could influence the total costs by less than 5%
7-22

b Degree of Confidence in Our Analytic Approach

High—The current evidence is plentiful and strongly supports the selected approach

Medium—Some evidence exists to support the selected approach, but data gaps are present

Low—Limited data exists to support the selected approach

c Ability to Assess Uncertainty (using WHO Uncertainty Framework)

Tier 0—Screening level, generic qualitative characterization

Tier 1—Scenario-specific qualitative characterization

Tier 2—Scenario-specific sensitivity analysis

Tier 3—Scenario-specific probabilistic assessment of individual and combined uncertainty

7.5 References

Anderson, J.F., and Sherwood, T., 2002. “Comparison of EPA and Other Estimates of Mobile 

Source Rule Costs to Actual Price Changes,” Office of Transportation and Air Quality, 

U.S. Environmental Protection Agency. Technical Paper published by the Society of 

Automotive Engineers. SAE 2002-01-1980.

Carlson, Curtis, Dallas R. Burtraw, Maureen, Cropper, and Karen L. Palmer. 2000. “Sulfur Dioxide 

Control by Electric Utilities: What Are the Gains from Trade?” Journal of Political 

Economy 108(#6):1292-1326.

Ellerman, Denny. January 2003. Ex Post Evaluation of Tradable Permits: The U.S. SO2 Cap-andTrade Program. Massachusetts Institute of Technology Center for Energy and 

Environmental Policy Research.

Gerard, D. and L.B. Lave (2005). “Implementing Technology-Forcing Policies: The 1970 Clean Air 

Act Amendments and the Introduction of Advanced Automotive Emissions Controls in 

the United States,” Technological Forecasting and Social Change, 72: 761-778.

Gumerman, Etan and Marnay, Chris. Learning and Cost Reductions for Generating Technologies 

in the National Energy Modeling System (NEMS), Ernest Orlando Lawrence Berkeley 

National Laboratory, University of California at Berkeley, Berkeley, CA. January 2004, 

LBNL-52559.

Hammit, J.K. (2000). “Are the costs of proposed environmental regulations overestimated? 

Evidence from the CFC phase out.” Environmental and Resource Economics, 16(#3): 281-

302.

Harrington, W., R.D. Morgenstern, and P. Nelson. 2000. “On the Accuracy of Regulatory Cost 

Estimates.” Journal of Policy Analysis and Management 19(2):297-322.

Harrington, W., R.D. Morgenstern, and P. Nelson. 2010. “How Accurate Are Regulatory Cost 

Estimates.” Available at http://www.rff.org/wv/Documents/

HarringtonMorgensternNelson_regulatory%20estimates.pdf.
7-23

Holmstead, Jeffrey, 2002. “Testimony of Jeffrey Holmstead, Assistant Administrator, Office of 

Air and Radiation, U.S. Environmental Protection Agency, Before the Subcommittee on 

Energy and air Quality of the committee on Energy and Commerce, U.S. House of 

Representatives, May 1, 2002, p. 10.

ICF Consulting. 2005. The Clean Air Act Amendment: Spurring Innovation and Growth While 

Cleaning the Air. Washington, DC. Available at 

http://www.icfi.com/Markets/Environment/doc_files/caaa-success.pdf.

Industrial Economics, Inc. Proposed Approach for Expanding the Treatment of Learning Curve 

Impacts for the Second Section 812 Prospective Analysis: Memorandum, prepared for 

U.S. EPA, Office of Air and Radiation, August 13, 2007.

Keohane, Nathaniel. 2002. “Environmental Policy and the Choice of Abatement Technique” 

Evidence from Coal-Fired Power Plants.” February. Yale School of Management.

Manson, Nelson, and Neumann. Unpublished Paper,2002. “Assessing the Impact of Progress 

and Learning Curves on Clean Air Act Compliance Costs.”

Office of Management and Budget (OMB). 2003. Circular A-4. Available at 

http://www.whitehouse.gov/omb/circulars_a004_a-4/

Popp, David. 2003. “Pollution Control Innovations and the Clean Air Act of 1990.” Autumn. 

Journal of Policy Analysis and Management, 22(4), 641-60.

E.H. Pechan and Associates and Industrial Economics, Direct Cost Estimates for the Clean Air Act 

Second Section 812 Prospective Analysis: Draft Report, prepared for U.S. EPA, Office of 

Air and Radiation, February 2007. Available at 

http://www.epa.gov/oar/sect812/mar07/direct_cost_draft.pdf.

U.S. Environmental Protection Agency (U.S. EPA). 2002. EPA Air Pollution Control Cost 

Manual—Sixth Edition (EPA 452/B-02-001). Office of Air Quality Planning and Standards, 

Research Triangle Park, NC. Also Available at http://epa.gov/ttn/catc/dir1/c_allchs.pdf.

U.S. Environmental Protection Agency (U.S. EPA). 2006. AirControlNET 4.1 Control Measures 

Documentation Report. Office of Air Quality Planning and Standards, Research Triangle 

Park, NC. Also Available at http://www.epa.gov/ttnecas1/models/

DocumentationReport.pdf.

U.S. Environmental Protection Agency. June 2007. Advisory Council on Clean Air Compliance 

Analysis (COUNCIL), Council Advisory on OAR’s Direct Cost Report and Uncertainty 

Analysis Plan. Washington, DC.
7-24

U.S. Environmental Protection Agency (U.S. EPA). 2010. Guidelines for Preparing Economic 

Analysis. Office of Policy, National Center for Environmental Economics. Also Available 

at http://yosemite.epa.gov/ee/epa/eed.nsf/Webpages/Guidelines.html/

$file/Guidelines.pdf

Yeh, Sonia and Rubin, Edward. February 2007. “Incorporating Technological Learning in the Coal 

Utility Environmental Cost (CUECost) Model: Estimating the Future Cost Trends of SO2, 

NOx, and Mercury Control Technologies.” Prepared for ARCADIS Geraghty and Miller, 

Research Triangle Park, NC 27711. Available at http://steps.ucdavis.edu/People/

slyeh/syeh-resources/Drft%20Fnl%20Rpt%20Lrng%20for%20CUECost_v3.pdf.
7.A-1

APPENDIX 7.A

OTHER EXTRAPOLATED COST APPROACHES

7.A.1 Extrapolated Cost Equations

The hybrid methodology creates a total cost curve for each pollutant for unknown 

future controls that might be used in order to move toward 2020 attainment. This approach 

explicitly estimates the cost of removing emissions for each pollutant for each area, with a 

higher cost-per-ton in areas needing a higher proportion of unknown controls relative to known 

modeled controls. For each pollutant in each area, the cost begins with a national constant 

cost-per-ton for that pollutant and increases as more of that pollutant is selected. The selection 

is made so that costs are minimized. The incremental improvement in air quality for an 

unknown control is determined, by pollutant, using an area-by-area ratio of air quality 

improvement to air quality change multiplied by the emission reductions from unknown 

controls for each pollutant and area. For each pollutant in an area, the per-unit costs of control 

increase with each additional unit of that pollutant chosen. The choices are made to minimize 

total cost. 

The hybrid methodology has the advantage of using the information about how 

significant the needed reductions from unspecified control technologies are relative to the 

known control measures and matching that with expected increasing per-unit cost for applying 

controls beyond those modeled. Under this approach, the relative costs of unknown controls in 

different geographic areas reflect the expectation that average per-ton control costs are likely 

to be higher in areas needing a higher ratio of emission reductions from unknown to known 

controls. Because no cost data exists for unknown future strategies, it is unclear whether 

approaches using hypothetical cost curves will be more accurate or less accurate in forecasting 

total national costs of unknown controls than a fixed-cost approach that uses a range of 

national cost-per-ton values. Extrapolated cost estimates are provided using a 7 percent 

discount rate because known control measure information is available at 7 percent for all

measures applied in the analysis. 

7.A.1.1 Theoretical Model for Hybrid Methodology

A model of increasing total costs was developed for each pollutant. The simplest form of 

ax2 + bx + c was used where x is the tons of a particular pollutant to be reduced in a particular 

area and a, b, and c are constants. For the hybrid methodology b is set to be a national, initial 

cost-per-ton (N) for unknown controls for a pollutant, and c is zero because there is no cost to 
7.A-2

imposing no control. The hybrid methodology has a different a for each pollutant and 

geographical area. For a particular geographic area and pollutant a is N/E where

N = national, initial cost/ton (b from above)

E = by geographic area and by pollutant, is the denominator1 and represents all 

emission reductions estimated to be required (from applying known and 

unknown controls to obtain the 15/35 baseline, as well as known controls to 

achieve the alternative standard) prior to estimating needed emission reductions 

from unknown controls to achieve the alternative standard. 

The hybrid methodology attempts to consider the varying conditions in each geographic 

area exceeding the alternative standard. Using the hybrid methodology, we develop marginal 

control cost curves associated with unknown control costs for each geographic area. Because 

the rate at which the unknown control costs increase varies across areas, the marginal cost will 

vary. For example, applying unknown controls to obtain the needed emission reductions in a 

geographic area with few emissions sources, very few known controls and many emission 

reductions needed will have a higher marginal cost. Where in another circumstance, applying 

unknown controls to obtain the needed emission reductions in a geographic area with many 

emissions sources, many known controls and many emission reductions needed will have a 

lower marginal cost.

The total cost equations presented below in Section 7.A.1.2 are used with the constraint 

that

Q − RSO2USO2 − RPM2.5UPM2.5 − RNOxUNOx = 0 (7.1)

where

U = unknown emission reductions

Q = air quality change needed for area to reach attainment

R = air quality to emissions ratio for area.

This equation above uses the R developed in Section 3.3.1.3 (Estimating Full Attainment) 

for each pollutant and area that is used to estimate the change in air quality for each unit of 

emissions. In other words, R is a measure of how much the air quality concentration changes 

 1 The numerator differs by pollutant and is the national, initial cost-per-ton for unknown controls discussed below, 

e.g., $17,000/ton for PM2.5.
7.A-3

when the emissions change. The least-cost solution is found for each geographic area and for 

each standard. See Section 4.2.2 for a discussion of the order in which controls were applied for 

geographic areas and pollutants. 

The cost-per-ton estimates were calculated by developing marginal cost curves for all 

known controls applied for the alternative standards as well as the baseline. We reviewed data 

on controls in approximately 120 counties with higher PM2.5 concentrations. We plotted, in 

order of increasing marginal cost, the cost-per-ton and cumulative emission reductions 

associated with these controls for PM2.5, SO2, and NOx. For PM2.5, the data show that 

approximately 96 percent of potential emission reductions associated with the known controls 

in those 120 counties could be obtained for $17,000/ton (2006 dollars) or less. For SO2, the data 

show that approximately 94 percent of potential emission reductions associated with the 

known controls in those 120 counties could be obtained for $5,400/ton (2006 dollars) or less. 

For NOx, the data show that approximately 92 percent of potential emission reductions 

associated with the known controls in those 120 counties could be obtained for $5,500/ton 

(2006 dollars) or less. We conservatively defined a threshold of 90 percent for unknown 

emission reductions for a particular pollutant in an area after reductions associated with known 

controls are achieved. As such, the national, initial cost-per-ton for unknown controls for the 

parameters NPM2.5, NSO2, and NNOxwere chosen at $17,000/ton (2006 dollars), $5,400/ton (2006 

dollars), and $5,500/ton (2006 dollars) for PM2.5, SO2, and NOx emission reductions, 

respectively. 

The results for the alternative hybrid methodology described in this Appendix and the 

fixed-cost approach described in Chapter 7 are presented for comparison in Table 7.A-1.

Table 7.A-1. Extrapolated Costs by Alternative Standard Analyzed (millions of 2006$)a

Alternative Standard Region

Extrapolated Costs

Fixed-Cost Methodology

Alternative Hybrid 

Methodology

7% 7%

13/35 East — —

West — —

California $2.9 $3.6

Total $2.9 $3.6

12/35 East — —

West $3.3 $24
7.A-4

California $65 $100

Total $69 $130

11/35 East $1.3 $3

West $38 $310

California $180 $280

Total $220 $590

11/30 East $21 $47

West $79 $470

California $190 $320

Total $290 $830

a Estimates are rounded to two significant figures.

The hybrid model is presented more formally below. For the simple form of ax2 + bx + c, 

where x is the tons of a particular pollutant to be reduced in a particular area and a, b, and c are 

constants.

7.A.1.2 Framework Applied to This Analysis

Total Cost Equation for the three pollutants is

Minimize �

NSO2

ESO2

�USO2

2 + NSO2USO2 + c + �[� NPM2.5

EPM2.5(j)

�UPM2.5 (j)

2 + NPM2.5UPM2.5(j)

]

n

j=1

+ d

+ �

NNOx

ENOx

�UNOX

2 + NNOXUNOX + f +

subject to the constraint �Qj − RSO2jUSO2 − RPM2.5j

UPM2.5j − RNOXjUNOX = 0

n

j=1

Where j is jth county up to the total number of nonattainment counties in each defined 

geographic area

USO2 ≥ 0

�UPM2.5j ≥ 0

n

j=1

UNOx ≥ 0

USO2 ≤ 0.9(TSO2 − ESO2)
7.A-5

�UPM2.5j ≤ = 0.9(TPM2.5j − EPM2.5j)

n

j=1

UNOx ≤ 0.9(TNOx − ENOx)

The constraints require the emissions changes to result in the required air quality 

change. The emissions changes cannot be negative. The unknown emission reductions for a 

particular pollutant in an area cannot exceed 90% of the remaining emissions after reductions 

associated with known controls are achieved. Section 7.2.3.1 includes information on the 

selection of the 90% threshold.

where

N = national constant cost/ton

E = known emission reductions

U = unknown emission reductions

Q = air quality change

R = air quality to emissions ratio

T = total emissions

This optimization can be executed in a number of ways (all resulting in the same 

answer). For this analysis we employed the data solver add-in (solver) for Microsoft Excel. We 

ran the solver for each area needing unknown controls for each standard. The detailed 

spreadsheet will be in the PM NAAQS docket.

7.A.1.3 Cost Minimization Approach

The solver iterates to select how much of each pollutant to choose in a cost-minimizing 

manner. In each geographic area with one or more counties that requires additional emission 

reductions to reach attainment, to select a quantity of each pollutant to minimize the costs of 

the needed emissions reductions, the solver

 looks simultaneously at PM2.5 emissions within any counties not meeting the 

standard and SO2 and NOx emissions from within the geographic area.

For example, for a three-county area where two counties are not estimated to meet the 

alternative standard, the solver picks PM2.5 reductions in each of the two counties and then SO2
7.A-6

and NOx reductions for the entire geographic area such that both counties would reach 

attainment in the least cost way.

In Chapter 3, we define ratios for each of the two counties associated with how much 

air quality concentration improvement would result from 1,000 tons of PM2.5 reduction in each 

respective county. Also in Chapter 3, we define ratios for each of the two counties associated 

with how much air quality concentration improvement would result from 1,000 tons of SO2

reduction in the defined geographic area (not just the respective counties). Lastly in Chapter 3, 

we define ratios for each of the two counties associated with how much air quality 

concentration improvement would result from 1,000 tons of NOx reduction in the defined 

geographic area (not just the respective county). In Chapters 3 and 4, we define and present 

geographic areas where SO2 and NOx emissions contribute to the air quality problems in a close 

cluster of counties. 

7.A.2 Sensitivity Analyses of Extrapolated Cost Approaches

Because of the uncertainties associated with estimating costs for the PM2.5 NAAQS and 

because a significant portion of the estimated emissions reductions and related costs for 

attaining the NAAQS come from unknown controls, it is important to test the sensitivity of the 

assumptions applied to estimate unknown controls. The sensitivity analyses below are included 

to help characterize the uncertainty for the cost estimates from unknown controls and the 

responsiveness of the cost estimates to varying parameter estimates and assumptions. Note 

that the tables below include cost estimates associated with unknown controls and not total 

cost estimates.

While there are many approaches to sensitivity analysis, we selected analyses below, 

keeping emissions estimates constant, to show variability in the cost estimates and remain 

consistent with the benefits analysis. Note that the extrapolated cost estimates are provided 

using a 7 percent discount rate because known control measure information is available at 7 

percent for all measures applied in this analysis. 

7.A.2.1 Sensitivity Analysis of Fixed-Cost Approach

Table 7.A.2 below presents the sensitivity analysis of the fixed-cost approach and 

includes, by region and alternative standard, the primary cost estimate of $15,000/ton. The 

Table also includes, by region and alternative standard, cost estimates using $10,000/ton and 

$20,000/ton. For the 12/35 alternative standard, the total cost estimate associated with 

unknown control costs ranges from $46 million to $92 million, depending on the fixed-cost-perton assumed.
7.A-7

Table 7.A-2. Sensitivity Analysis of Fixed-Cost Approach for Unknown Controls by Alternative 

Standard Analyzed (millions of 2006$)a

Alternative 

Standard Region

Extrapolated Costs

$10,000/ton $15,000/ton $20,000/ton

7% 7% 7%

13/35 East — — —

West — — —

California $1.9 $2.9 $3.9

Total $1.9 $2.9 $3.9

12/35 East — —

West $2.2 $3.3 $4.5

California $44 $65 $87

Total $46 $69 $92

11/35 East $0.90 $1.3 $1.8

West $26 $38 $51

California $120 $180 $240

Total $150 $220 $290

11/30 East $14 $21 $28

West $53 $79 $110

California $130 $190 $250

Total $190 $290 $390

a Estimates are rounded to two significant figures.

7.A.2.2 Sensitivity Analysis of Alternative Hybrid Approach

Table 7.A.3 below presents the sensitivity analysis of the alternative hybrid approach. To 

be consistent with the sensitivity analysis of the fixed-cost approach, the table also includes, by 

region and alternative standard, cost estimates using alternate parameter estimates for the 

initial cost per ton. For the 12/35 alternative standard, the total cost estimate associated with 

unknown control costs ranges from $85 million to $170 million.
7.A-8

Table 7.A-3. Sensitivity Analysis of Alternative Hybrid Approach for Unknown Controls by 

Alternative Standard Analyzed (millions of 2006$)a

Alternative 

Standard Region

Extrapolated Costs

30 Percent Lower b

Estimate 

w/Original Cost 

of Initial Ton c 30 Percent 

Higher d

7% 7% 7%

13/35 East — — —

West — — —

California $2.4 $3.6 $4.7

Total $2.4 $3.6 $4.7

12/35 East — — —

West $16 $24 $32

California $69 $100 $140

Total $85 $130 $170

11/35 East $1.8 $3 $3.6

West $210 $310 $420

California $190 $280 $370

Total $400 $590 $790

11/30 East $32 $47 $63

West $310 $470 $630

California $210 $320 $420

Total $550 $830 $1,100

a Estimates are rounded to two significant figures. b These estimates reflect national, initial cost-per ton estimates for the three parameters that are 30 percent 

lower. c As discussed in Section 7.A.1.1 above, the national, initial cost-per-ton for unknown controls for the parameters 

NPM2.5, NSO2, and NNOx were chosen at $17,000/ton (2006 dollars), $5,400/ton (2006 dollars), and $5,500/ton 

(2006 dollars) for PM2.5, SO2, and NOx emission reductions, respectively. In addition, as discussed in Chapter 7, 

Section 7.2.3, the hybrid cost methodology is used to estimate the needed emission reductions. d These estimates reflect national, initial cost-per ton estimates for the three parameters that are 30 percent 

higher.
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CHAPTER 8

COMPARISON OF BENEFITS AND COSTS

8.1 Synopsis

This chapter compares estimates of the benefits with economic costs and summarizes 

the net benefits of alternative standards relative to a baseline that includes recently 

promulgated national regulations (CSAPR, MATS, and others). We include a discussion of net 

benefits for the case of full attainment and discuss selected limitations of the analyses.

8.2 Analysis

In the analysis, we estimate the net benefits of the proposed range of annual PM2.5

standards of 12/35 to 13/35. For 12/35, net benefits are estimated to be $2.3 billion to $5.9 

billion at a 3% discount rate and $2.0 billion to $5.3 billion at a 7% discount rate in 2020 (2006 

dollars).1 For 13/35, net benefits are estimated to be $85 million to $220 million at the 3% 

discount rate and $76 million to $200 million at the 7% discount rate.

The RIA also analyzes the benefits and costs of two alternative primary PM2.5 standards 

(11/35 and 11/30) that are more stringent than the proposed standard range of 12/35 to 13/35. 

The EPA estimated the net benefits of the alternative annual PM2.5 standard of 11/35 to be $8.9 

billion to $23 billion at a 3% discount rate and $8.0 billion to $21 billion at a 7% discount rate in 

2020. The EPA estimated the net benefits of the alternative annual PM2.5 standard of 11/30 to 

be $14 billion to $36 billion at a 3% discount rate and $13 billion to $33 billion at a 7% discount 

rate in 2020. All estimates are in 2006$.2

The EPA determined that all counties would meet the 14/35 standard concurrently with 

meeting the existing 15/35 standard at no additional cost. Consequently, there is no need to 

present an analysis of 14/35 in this RIA.

We provide these results in Table 8-1. In Table 8-2, we provide the avoided health 

incidences associated with these standard levels.

 1 Using a 2010$ year increases estimated costs and benefits by approximately 8%. Because of data limitations, we 

were unable to discount compliance costs for all sectors at 3%. As a result, the net benefit calculations at 3% 

were computed by subtracting the monetized benefits at 3% minus the costs at 7%. 2 Using a 2010 $ year increases estimated costs and benefits by approximately 8%. Because of data limitations, we 

were unable to discount compliance costs for all sectors at 3%. As a result, the net benefit calculations at 3% 

were computed by subtracting the monetized benefits at 3% minus the costs at 7%.
8-2

8.3 Conclusions of the Analysis

EPA’s illustrative analysis has estimated the health and welfare benefits and costs 

associated with proposed revised PM NAAQS. The results for 2020 suggest there will be 

significant health and welfare benefits and these benefits will outweigh the costs associated 

with the illustrative control strategies in 2020.

Table 8-1. Total Monetized Benefits, Total Costs, and Net Benefits in 2020 (millions of 

2006$a

)—Full Attainment 

Alternative 

Standard

Total Costs Monetized Benefits b Net Benefits b

3% Discount 

Ratec

7% Discount 

Rate

3% Discount 

Rate

7% Discount 

Rate

3% Discount 

Ratec

7% Discount 

Rate

13/35 $2.9 $2.9 $88 to $220 $79 to $200 $85 to $220 $76 to $200

12/35 $69 $69 $2,300 to 

$5,900

$2,100 to 

$5,400

$2,300 to 

$5,900

$2,000 to 

$5,300

11/35 $270 $270 $9,200 to 

$23,000

$8,300 to 

$21,000

$8,900 to 

$23,000

$8,000 to 

$21,000

11/30 $390 $390 $14,000 to 

$36,000

$13,000 to 

$33,000

$14,000 to 

$36,000

$13,000 to 

$33,000

a Rounded to two significant figures. Using a 2010$ year increases estimated costs and benefits by approximately 

8%.

b The reduction in premature deaths each year accounts for over 90% of total monetized benefits. Mortality risk 

valuation assumes discounting over the SAB-recommended 20-year segmented lag structure. Not all possible 

benefits or disbenefits are quantified and monetized in this analysis. B is the sum of all unquantified benefits. 

Data limitations prevented us from quantifying these endpoints, and as such, these benefits are inherently more 

uncertain than those benefits that we were able to quantify.

c Due to data limitations, we were unable to discount compliance costs for all sectors at 3%. As a result, the net 

benefit calculations at 3% were computed by subtracting the monetized benefits at 3% minus the costs at 7%.

For the lower end of the proposed standard range of 12/35, the EPA estimates that the 

benefits of full attainment exceed the costs of full attainment by 34 to 86 times at a 3% 

discount rate and 30 to 78 times at a 7% discount rate. For the upper end of the proposed 

standard range of 13/35, the EPA estimates that the benefits of full attainment exceed the 

costs of full attainment by 30 to 77 times at a 3% discount rate and 27 to 69 times at a 7% 

discount rate. For the alternative standards, 11/35 and 11/30, the EPA estimates that the 

benefits of full attainment exceed the costs of full attainment by 34 to 94 times at a 3% 

discount rate and 30 to 85 times at a 7% discount rate.
8-3

Table 8-2. Estimated Number of Avoided PM2.5 Health Impacts for Standard Alternatives—

Full Attainmenta

Health Effect

Alternative Combination of Primary PM2.5 Standards

13/35 12/35 11/35 11/30

Adult Mortality 

Krewski et al. (2009) 11 280 1,100 1,700

Laden et al. (2006) (adult) 27 730 2,900 4,500

Woodruff et al. (1997) (infant) 0 1 3 4

Non-fatal heart attacks (age >18)

Peters et al. (2001) 11 320 1,300 1,900

Pooled estimate of 4 studies 1 35 140 210

Hospital admissions—respiratory (all ages) 3 98 430 620

Hospital admissions—cardiovascular (age > 18) 3 95 400 580

Emergency department visits for asthma (age < 18) 6 160 730 1,000

Acute bronchitis (age 8–12) 22 540 2,000 3,100

Lower respiratory symptoms (age 7–14) 290 6,900 25,000 39,000

Upper respiratory symptoms (asthmatics age 9–11) 410 9,800 37,000 56,000

Asthma exacerbation (age 6–18) 410 24,000 89,000 140,000

Lost work days (age 18–65) 1,800 44,000 170,000 260,000

Minor restricted-activity days (age 18–65) 11,000 260,000 1,000,000 1,500,000

a Incidence estimates are rounded to whole numbers with no more than two significant figures.

8.4 Caveats and Limitations

EPA acknowledges several important limitations of the primary and secondary analysis. 

These include:

8.4.1 Benefits Caveats

 PM2.5 mortality co-benefits represent a substantial proportion of total monetized 

benefits (over 98%). To characterize the uncertainty in the relationship between 

PM2.5 and premature mortality, we include a set of twelve estimates based on 

results of the PM2.5 mortality expert elicitation study in addition to our core 

estimates. Even these multiple characterizations omit the uncertainty in air quality 

estimates, baseline incidence rates, populations exposed, and transferability of the 

effect estimate to diverse locations. As a result, the reported confidence intervals 

and range of estimates give an incomplete picture about the overall uncertainty in 

the PM2.5 estimates. This information should be interpreted within the context of the 

larger uncertainty surrounding the entire analysis.

 Most of the estimated avoided premature deaths occur at or above the lowest 

measured PM2.5 concentration in the two studies used to estimate mortality 
8-4

benefits. In general, we have greater confidence in risk estimates based on PM2.5 

concentrations where the bulk of the data reside and somewhat less confidence 

where data density is lower.

 We analyzed full attainment in 2020, and projecting key variables introduces 

uncertainty. Inherent in any analysis of future regulatory programs are uncertainties 

in projecting atmospheric conditions and source-level emissions, as well as 

population, health baselines, incomes, technology, and other factors.

 There are uncertainties related to the health impact functions used in the analysis. 

These include within-study variability; pooling across studies; the application of C-R 

functions nationwide and for all particle species; extrapolation of impact functions 

across populations; and various uncertainties in the C-R function, including causality 

and shape of the function at low concentrations. Therefore, benefits may be underor over-estimates.

 This analysis omits certain unquantified effects due to lack of data, time, and 

resources. These unquantified endpoints include other health and ecosystem 

effects. The EPA will continue to evaluate new methods and models and select those 

most appropriate for estimating the benefits of reductions in air pollution. 

8.4.2 Control Strategy and Cost Analysis Caveats and Limitations

Control Technology Data

 Technologies applied may not reflect emerging devices that may be available in 

future years.

 Control efficiency data depend on equipment being well maintained.

 Area source controls assume a constant estimate of emission reductions, despite 

variability in extent and scale of application.

Control Strategy Development

 States may develop different control strategies than the ones illustrated.

 Data on baseline controls from current SIPs are lacking.

 Timing of control strategies may be different than envisioned in the RIA.

 Controls are applied within the county with the violating monitor. It is possible that 

additional known controls could be available in a wider geographical area.

 Unknown controls were needed to reach attainment in several counties. Costs 

associated with these unknown controls were estimated using a fixed cost per ton 

methodology as well as an extrapolated cost methodology.

 Emissions reductions from mobile sources, EGUs, other PM2.5 precursors (i.e., 

ammonia and VOC), and voluntary programs are not reflected in the analyses.
8-5

Technological Change

 Emission reductions do not reflect potential effects of technological change that may 

be available in future years.

 Effects of “learning by doing” are not accounted for in the emission reduction 

estimates.

 Future technology developments in sectors not analyzed here (e.g., EGUs) may be 

transferrable to non-EGU and area sources, making these sources more viable for 

achieving future attainment at a lower cost than the cost presented in this analysis.

Engineering Cost Estimates

 Because of data limitations, we were unable to discount compliance costs for all 

sectors at 3%. 

 Estimates of private compliance cost are used as a proxy for social cost. 

Unquantified Costs

 A number of costs remain unquantified, including administration costs of federal and 

state SIP programs, and transactional costs.
9-1

CHAPTER 9

STATUTORY AND EXECUTIVE ORDER REVIEWS

9.1 Synopsis

This chapter summarizes the Statutory and Executive Order (EO) impact analyses 

relevant for the PM NAAQS Regulatory Impact Analysis. For each EO and Statutory requirement 

we describe both the requirements and the way in which our analysis addresses these 

requirements.

9.2 Executive Order 12866: Regulatory Planning and Review

Under section 3(f)(1) of Executive Order 12866 (58 FR 51735, October 4, 1993), this 

action is an “economically significant regulatory action” because it is likely to have an annual 

effect on the economy of $100 million or more. Accordingly, the EPA submitted this action to 

the Office of Management and Budget (OMB) for review under Executive Orders 12866 and 

13563 (76 FR 3821, January 21, 2011), and any changes made in response to OMB 

recommendations have been documented in the docket for this action.

9.3 Paperwork Reduction Act

This action does not impose an information collection burden under the provisions of 

the Paperwork Reduction Act, 44 U.S.S. 3501 et seq. Burden is defined at 5 CFR 1320.3(b). 

There are no information collection requirements directly associated with revisions to a NAAQS 

under section 109 of the CAA.

9.4 Regulatory Flexibility Act

The Regulatory Flexibility Act (RFA) generally requires an agency to prepare a regulatory 

flexibility analysis of any rule subject to notice and comment rulemaking requirements under 

the Administrative Procedure Act or any other statute unless the agency certifies that the rule 

will not have a significant economic impact on a substantial number of small entities. Small 

entities include small businesses, small organizations, and small governmental jurisdictions.

For purposes of assessing the impacts of this rule on small entities, small entity is 

defined as: (1) a small business that is a small industrial entity as defined by the Small Business 

Administration’s (SBA) regulations at 13 CFR 121.201; (2) a small governmental jurisdiction that 

is a government of a city, county, town, school district or special district with a population of 

less than 50,000; and (3) a small organization that is any not-for-profit enterprise which is 

independently owned and operated and is not dominant in its field.
9-2

After considering the economic impacts of this proposed rule on small entities, I certify 

that this action will not have a significant economic impact on a substantial number of small 

entities. This proposed rule will not impose any requirements on small entities. Rather, this rule 

establishes national standards for allowable concentrations of particulate matter in ambient air 

as required by section 109 of the CAA. See also American Trucking Associations v. EPA. 175 F.3d 

at 1044-45 (NAAQS do not have significant impacts upon small entities because NAAQS 

themselves impose no regulations upon small entities). Please refer to the preamble for 

additional details.

9.5 Unfunded Mandates Reform Act

This action contains no Federal mandates under the provisions of Title II of the 

Unfunded Mandates Reform Act of 1995 (UMRA), 2 U.S.C. 1531-1538 for state, local, or tribal 

governments or the private sector. The action imposes no enforceable duty on any state, local 

or tribal governments or the private sector. Therefore, this action is not subject to the 

requirements of sections 202 or 205 of the UMRA.

This action is also not subject to the requirements section 205 of the UMRA because it 

contains no regulatory requirements that might significantly or uniquely affect small 

governments. This action imposes no new expenditure or enforceable duty on any state, local, 

or tribal governments or the private sector, and the EPA has determined that this rule contains 

no regulatory requirements that might significantly or uniquely affect small governments.

Furthermore, in setting a NAAQS, the EPA cannot consider the economic or 

technological feasibility of attaining ambient air quality standards, although such factors may be 

considered to a degree in the development of state plans to implement the standards. See also 

American Trucking Associations v. EPA, 175 F. 3d at 1043 (noting that because the EPA is 

precluded from considering costs of implementation in establishing NAAQS, preparation of a 

Regulatory Impact Analysis pursuant to the Unfunded Mandates Reform Act would not furnish 

any information which the court could consider in reviewing the NAAQS). The EPA 

acknowledges, however, that any corresponding revisions to associated SIP requirements and 

air quality surveillance requirements, 40 CFR part 51 and 40 CFR part 58, respectively, might 

result in such effects. Accordingly, the EPA will address, as appropriate, unfunded mandates if 

and when it proposes any revisions to 40 CFR parts 51 or 58.

9.6 Executive Order 13132: Federalism

This action does not have federalism implications. It will not have substantial direct 

effects on the states, on the relationship between the national government and the states, or 
9-3

on the distribution of power and responsibilities among the various levels of government, as 

specified in Executive Order 13132. The rule does not alter the relationship between the 

Federal government and the states regarding the establishment and implementation of air 

quality improvement programs as codified in the CAA. Under section 109 of the CAA, the EPA is 

mandated to establish and review NAAQS; however, CAA section 116 preserves the rights of 

states to establish more stringent requirements if deemed necessary by a state. Furthermore, 

this proposed rule does not impact CAA section 107 which establishes that the states have 

primary responsibility for implementation of the NAAQS. Finally, as noted in section D on UMRA 

in the preamble, this rule does not impose significant costs on state, local, or Tribal 

governments or the private sector. Thus, Executive Order 13132 does not apply to this action.

However, as also noted in section D on UMRA in the preamble, the EPA recognizes that 

states will have a substantial interest in this rule and any corresponding revisions to associated 

air quality surveillance requirements, 40 CFR part 58. Please refer to the preamble for 

additional details on the Executive Order.

9.7 Executive Order 13175: Consultation and Coordination with Indian Tribal 

Governments

The action does not have tribal implications, as specified in Executive Order 13175 (65 

FR 67249, November 9, 2000). It does not have a substantial direct effect on one or more Indian 

Tribes, since Tribes are not obligated to adopt or implement any NAAQS. The Tribal Authority 

Rule gives Tribes the opportunity to develop and implement CAA programs such as the PM 

NAAQS, but it leaves to the discretion of the Tribe whether to develop these programs and 

which programs, or appropriate elements of a program, they will adopt. Thus, Executive Order 

13175 does not apply to this rule.

Although Executive Order 13175 does not apply to this rule, the EPA consulted with 

tribal officials or other representatives of tribal governments in developing this action. Please 

refer to the preamble for additional details on the Executive Order.

9.8 Executive Order 13045: Protection of Children from Environmental Health and Safety 

Risks

This action is subject to Executive Order 13045 (62 FR 19885, April 23, 1997) because it 

is an economically significant regulatory action as defined by Executive Order 12866, and the 

EPA believes that the environmental health or safety risk addressed by this action may have a 

disproportionate effect on children. Accordingly, we have evaluated the environmental health 

or safety effects of PM exposures on children. The protection offered by these standards may 
9-4

be especially important for children because childhood represents a lifestage associated with 

increased susceptibility to PM-related health effects. Because children have been identified as a 

susceptible population, we have carefully evaluated the environmental health effects of 

exposure to PM pollution among children. Discussions of the results of the evaluation of the 

scientific evidence and policy considerations pertaining to children are contained in sections 

III.B, III.D, IV.B, and IV.C of the preamble. A listing of documents that contain the evaluation of 

scientific evidence and policy considerations that pertain to children is found in the section on 

Children’s Environmental Health in the Supplementary Information section of the preamble, 

and a copy of all documents have been placed in the public docket for this action.

9.9 Executive Order 13211: Actions that Significantly Affect Energy Supply, Distribution or 

Use

This action is not a “significant energy action” as defined in Executive Order 13211, (66 

FR 28355, May 22, 2001) because it is not likely to have a significant adverse effect on the 

supply, distribution, or use of energy. The purpose of this action concerns the review of the 

NAAQS for PM. The action does not prescribe specific pollution control strategies by which 

these ambient standards will be met. Such strategies are developed by states on a case-by-case 

basis, and the EPA cannot predict whether the control options selected by states will include 

regulations on energy suppliers, distributors, or users.

9.10 National Technology Transfer and Advancement Act

Section 12(d) of the National Technology Transfer and Advancement Act of 1995 

(NTTAA), Public Law 104– 113, section 12(d) (15 U.S.C. 272 note) directs the EPA to use 

voluntary consensus standards in its regulatory activities unless to do so would be inconsistent 

with applicable law or otherwise impractical. Voluntary consensus standards are technical 

standards (e.g., materials specifications, test methods, sampling procedures, and business 

practices) that are developed or adopted by voluntary consensus standards bodies. The NTTAA 

directs the EPA to provide Congress, through OMB, explanations when the Agency decides not 

to use available and applicable voluntary consensus standards.

This proposed rulemaking involves technical standards for environmental monitoring 

and measurement. Specifically, the EPA proposes to retain the indicators for fine (PM2.5) and 

coarse (PM10) particles. The indicator for fine particles is measured using the Reference 

Method for the Determination of Fine Particulate Matter as PM2.5 in the Atmosphere (appendix 

L to 40 CFR part 50), which is known as the PM2.5 FRM, and the indicator for coarse particles is 

measured using the Reference Method for the Determination of Particulate Matter as PM10 in 
9-5

the Atmosphere (appendix J to 40 CFR part 50), which is known as the PM10 FRM. The EPA also 

proposes a separate secondary standard defined in terms of a calculated PM2.5 light extinction 

indicator, which would use PM2.5 mass species and relative humidity data to calculate PM2.5

light extinction.

To the extent feasible, the EPA employs a Performance-Based Measurement System 

(PBMS), which does not require the use of specific, prescribed analytic methods. The PBMS is 

defined as a set of processes wherein the data quality needs, mandates or limitations of a 

program or project are specified, and serve as criteria for selecting appropriate methods to 

meet those needs in a cost-effective manner. It is intended to be more flexible and cost 

effective for the regulated community; it is also intended to encourage innovation in analytical 

technology and improved data quality. Though the FRM defines the particular specifications for 

ambient monitors, there is some variability with regard to how monitors measure PM, 

depending on the type and size of PM and environmental conditions. Therefore, it is not 

practically possible to fully define the FRM in performance terms to account for this variability. 

Nevertheless, our approach in the past has resulted in multiple brands of monitors being 

approved as FRM for PM, and we expect this to continue. Also, the FRMs described in 40 CFR 

part 50 and the equivalency criteria described in 40 CFR part 53, constitute a performancebased measurement system for PM, since methods that meet the field testing and performance 

criteria can be approved as FEMs. Since finalized in 2006 (71 FR, 61236, October 17, 2006) the 

new field and performance criteria for approval of PM2.5 continuous FEMs has resulted in the 

approval of six approved FEMs. In summary, for measurement of PM2.5 and PM10, the EPA 

relies on both FRMs and FEMs, with FEMs relying on a PBMS approach for their approval. The 

EPA is not precluding the use of any other method, whether it constitutes a voluntary 

consensus standard or not, as long as it meets the specified performance criteria.

For the proposed distinct secondary standard defined in terms of a calculated PM2.5 light 

extinction indicator, the EPA proposes to use existing monitoring technologies that are already 

deployed in the CSN and IMPROVE monitoring programs as well as relative humidity data from 

sensors already deployed at routine weather stations. The sampling and analysis protocols in 

use in the CSN program are the result of substantial input and recommendations from CASAC 

both during their initial deployment about ten years ago, and during the more recent transition 

to carbon sampling that is consistent with IMPROVE protocols (Henderson 2005c). Monitoring 

agencies also played a strong role in directing the sampling technologies used in the CSN. 

During the first few years of implementing the CSN there were up to four different sampling 

approaches used in the network. Over time as monitoring agencies shared their experiences 
9-6

and data with each other, several agencies shifted their network operations to the sampling 

technology used today. By 2008, the EPA was working closely with all remaining monitoring 

agencies to transition to the current CSN sampling for ions and elements. All carbon sampling 

was fully transitioned to the current method by October of 2009 for consistency with the 

IMPROVE program. Therefore, while the current CSN sampling methods were not developed or 

adopted by a voluntary consensus standard body, they are the result of harmonizing the 

network by monitoring agency users and EPA. The CSN network and methods are described in 

more detail in the Policy Assessment (US EPA, 2011a, Appendix B, section B.1.3).

9.11 Executive Order 12898: Federal Actions to Address Environmental Justice in Minority 

Populations and Low-Income Populations

Executive Order 12898 (59 FR 7629, February 16, 1994) establishes federal executive 

policy on environmental justice. Its main provision directs federal agencies, to the greatest 

extent practicable and permitted by law, to make environmental justice part of their mission by 

identifying and addressing, as appropriate, disproportionately high and adverse human health 

or environmental effects of their programs, policies, and activities on minority populations and 

low-income populations in the United States.

The EPA maintains an ongoing commitment to ensure environmental justice for all 

people, regardless of race, color, national origin, or income. Ensuring environmental justice 

means not only protecting human health and the environment for everyone, but also ensuring 

that all people are treated fairly and are given the opportunity to participate meaningfully in 

the development, implementation, and enforcement of environmental laws, regulations, and 

policies. The EPA has identified potential disproportionately high and adverse effects on 

minority and/or low-income populations from this proposed rule.

The EPA has identified persons from lower socioeconomic strata as a susceptible 

population for PM-related health effects. As a result, the EPA has carefully evaluated the 

potential impacts on low-income and minority populations as discussed in section III.E.3.a of 

the preamble. The Agency expects this proposed rule would lead to the establishment of 

uniform NAAQS for PM. The Integrated Science Assessment and Policy Assessment contain the 

evaluation of the scientific evidence and policy considerations that pertain to these 

populations. These documents are available as described in the Supplementary Information 

section of the preamble and copies of all documents have been placed in the public docket for 

this action.
10-1

CHAPTER 10

SECONDARY STANDARDS ANALYSIS

10.1 Introduction

As defined by section 109(b)(2) of the Clean Air Act (CAA), the purpose of a secondary 

NAAQS standard is to protect public welfare against negative effects of criteria air pollutants, 

including decreased visibility, climate effects, and damage to ecological systems and building 

materials. Ambient PM has been associated with visibility impairment in diverse regions across 

the United States and is considered adverse to the public welfare. EPA is proposing a national 

visibility standard in conjunction with the Regional Haze Program as a means of achieving 

appropriate levels of protection against PM-related visibility impairments in urban, non-urban 

and Federal Class I areas across the country. EPA evaluated two proposed secondary standard 

levels of 30 deciviews (dv) and 28 dv, along with a more stringent standard level of 25 dv, based 

on 24-hour average speciated PM2.5 measurements and with a 3-year average, 90th percentile 

form. 

10.2 The Secondary NAAQS Standard

The secondary PM2.5 NAAQS standard consists of three parts: a level, averaging period, 

and form. In the Urban-focused Visibility Assessment (U.S. EPA, 2010) and the Policy Assessment 

for the Review of the PM NAAQS (U.S. EPA, 2011), several preference studies provide the 

foundation for the secondary PM NAAQS.1 The three completed survey studies (all in the west) 

included Denver, Colorado (Ely et al., 1991), one in the lower Fraser River valley near 

Vancouver, British Columbia (BC), Canada (Pryor, 1996), and one in Phoenix, Arizona (BBC 

Research & Consulting, 2003). A pilot focus group study was conducted in Washington, DC on 

behalf of EPA to inform the 2006 PM NAAQS review (Abt Associates Inc., 2001). Using the 

results of these studies, EPA determined that for a majority of individuals, the range of 

acceptable urban visibility falls between 20 dv and 30 dv based on a 4-hour average indicator 

(U.S. EPA, 2011). For this analysis, we consider the two proposed standard levels of 30 dv and 

28 dv, both averaged over 24 hours, along with a more stringent 24-hour average standard 

level.2 While a sub-daily (i.e., 4-hour) averaging period would capture the wide variations in 

 1 For more detail about these preference studies, including information about study designs and sampling 

protocols, please see Section 2 of the Particulate Matter Urban-Focused Visibility Assessment (U.S. EPA, 2010b). 2

In order to provide generally equivalent protection, the level of a NAAQS based on a 24-hour average indicator 

should include an adjustment compared to the level that would be applied to a NAAQS based on a daily 

maximum daylight 4-hour average indicator. Using 15 study sites, EPA staff investigated five approaches to 

making this adjustment, for 4-hour indicator NAAQS levels of 20, 25, and 30 dv. An approach thought by EPA 

staff to be more appropriate for further consideration yielded adjusted NAAQS levels of 21, 25, and 28 dv as 
10-2

visibility conditions that occur over the course of a day, a 24-hour averaging period avoids data 

quality uncertainties associated with instruments currently available to measure hourly PM2.5 

mass (U.S. EPA, 2011). 

EPA proposes using a 3-year average, 90th percentile form for the standard. Determining 

attainment using this form requires comparing the level of the standard to the 3-year average 

of the 90th percentile of the measured indicator. Using a multi-year percentile form for the 

standard lessens the influence of unusual emissions values and provides a degree of stability for 

implementation planning (U.S. EPA, 2011).

10.3 Visibility Benefits from PM Reduction3

Visibility directly impacts the quality of life in the places where people live, work, and 

travel (U.S. EPA, 2009). Air pollution, including particulates, contributes to decreased visibility 

by scattering and absorbing light, which reduces visual range and clarity. PM2.5 component 

species that contribute to decreased visibility include sulfates, nitrates, organic carbon, 

elemental carbon, and soil (Sisler, 1996). Visibility impairment is expressed in terms of light 

extinction, measured in inverse megameters (Mm-1), or in terms of the deciview haze index, 

which is calculated based on total light extinction (Pitchford and Malm, 1994). A change of one 

dv is believed to be the smallest change in visible air quality perceptible by the human eye 

(Pitchford and Malm, 1994).

Visibility conditions and sources of visibility impairment vary both by region and season. 

Humidity increases visibility impairment because some particles, such as ammonium sulfate 

and ammonium nitrate, absorb water and become larger when relative humidity increases, 

resulting in increased visibility impairment (U.S. EPA, 2009). The eastern U.S. generally 

experiences greater visibility impairment due to higher concentrations of particulates and 

higher average humidity levels. Particulate sulfate is the dominant source of reduced visual air 

quality in the eastern U.S. (>50% of the particulate light extinction) and an important 

contributor to visibility impairment elsewhere in the country (>20% of particulate light 

extinction) (U.S. EPA, 2009). Particulate nitrate contributes to decreased visibility in California 

and the upper Midwest, particularly during the winter (U.S. EPA, 2009). In all regions, urban 

particulate concentrations are higher than those in the surrounding non-urban area, but 

 

the 24-hour PM2.5 light extinction indicator levels that are generally equivalent to levels of 20, 25, and 30 dv 

applied to a daily maximum daylight 4-hour PM2.5 light extinction indicator (U.S. EPA, 2011). 3

Additional discussion of visibility benefits related to attainment of the primary PM NAAQS standard can be found 

in Chapter 6 of this RIA.
10-3

western urban areas show greater differences from the surrounding non-urban areas than do 

eastern urban areas (U.S. EPA, 2009).

10.4 Baseline Modeling Projection Data (2020)

EPA has proposed to use a calculated indicator of PM-related light extinction to 

determine whether an area is in attainment for the secondary PM2.5 NAAQS standard. The 

IMPROVE4 algorithm uses the estimated impact of each PM component species and relative 

humidity to calculate the amount of PM-related light extinction. In the equation, each PM 

component species is multiplied by a factor related to its impact on light extinction. Component 

species affected by the presence of water in the ambient air are also multiplied by a factor 

representing the relative humidity. These factors are summed to determine the total light 

extinction caused by PM. To calculate design values for this analysis, EPA is using a modified 

version of this algorithm, which is explained in more detail in Chapter 3 of this RIA.

To estimate design values for this analysis, we apply the original IMPROVE algorithm to 

24-hour, speciated PM2.5 concentrations measured at 236 Chemical Speciation Network (CSN) 

monitors across the country and climatological mean relative humidity data to calculate the 

estimated light extinction in each location. The 207 counties with CSN monitors are identified in 

Figure 10-1. We then compare the calculated light extinction from a monitor to the standard 

level to determine whether the county where the monitor is located is in attainment (U.S. EPA, 

2011).

Even before incorporating reductions to attain the current primary standard of 15 μg/m3

annual and 35 μg/m3 24-hour (denoted 15/35), no monitors are expected to exceed a 

secondary standard level of 30 dv and only three monitors are expected to exceed a secondary 

standard level of 28 dv in 2020. Because all three of these monitors also exceed the 15/35 

primary standard,5 we would expect each would attain a secondary standard of 28 dv when 

controlled at the primary standard level. Further emission reductions to meet a more stringent 

primary standard would lead to additional improvement in visibility in all areas. Table 10-1 

 4

The Interagency Monitoring of Protected Visual Environment (IMPROVE) program was established in 1985 to aid 

in the creation of state and federal implementation plans for visibility in Class I areas as required in the 1977 

amendments to the CAA. 5

The monitors that are above 15/35 are monitor id numbers: 60658001 (located in Riverside, CA); 60290014 

(located in Kern, CA); and 60990005 (located in Stanislaus, CA). The projected 2020 base case design values for 

the primary standard for these monitors are 16.30/46.5 μg/m3

, 14.18/44.0 μg/m3, and 10.85/37.0 μg/m3, 

respectively. The projected 2020 base case design values for the secondary standard for these monitors are: 29 

dv, 30 dv, and 29 dv, respectively. We believe that the emissions reductions needed to obtain the current 

primary standard levels of 15/35 will be enough to lower the projected 2020 secondary standard design values 

to 28 dv.
10-4

shows the percentage of monitors projected to exceed 30, 28, or 25 dv in 2020, prior to full 

attainment of the current primary standard. 

Figure 10-1. Counties with Monitors Included in Analysis

Table 10-1. Percentage of Monitors Projected to Exceed Alternative Secondary Standards in 

2020, Prior to Attainment of Primary Standard of 15/35

Level

Number Exceeding

Selected Level

% Exceeding Selected 

Level

30 0 0.0%

28 3 1.3%

25 28 11.9%

Of the 236 monitors for which visibility design values are available, 208 (88%) attain a 

secondary standard of 25 dv or better in 2020, prior to full attainment of the current primary 

standard. Figure 10-2 shows the counties that would exceed the secondary standards in this 

analysis. Visibility design values calculated from data for each monitor location included in this 

analysis can be found in Appendix 10-A.
10-5

Figure 10-2. Design Values in 2020, Prior to Full Attainment of a Primary Standard of 15/35

10.5 Impacts of Attaining a Distinct Secondary Standard

Based on the air quality analysis conducted for the primary PM2.5 standard, all 

monitored areas are estimated to be in attainment with a secondary standard level of either 30 

dv or 28 dv in 2020, assuming full attainment of the primary PM2.5 standard. For the two 

optional levels proposed for the secondary standard, no additional costs or benefits will be 

realized beyond those quantified for the primary PM2.5 standard in this RIA.6

10.6 Limitations of Analysis

Visibility design values for 2020 were calculated using the CMAQ modeling information 

and 2004-2006 ambient measurements. To determine the design values for meeting the 

current primary PM2.5 standard and proposed alternative primary standards, we used a 

 6 Based on the air quality modeling used in this analysis, EPA does not believe that any county that is in compliance 

with primary will violate secondary standard. However, different modeling trajectories could potentially lead to 

cases in which the secondary standard is binding.
10-6

methodology, described in Chapter 3, to estimate the small emissions reductions needed from 

control measures to show attainment and to estimate the costs and benefits of attaining the 

proposed alternative primary standards. It is not possible to apply this methodology to the 

visibility design values.7 As a result, the only analysis available for the proposed alternative 

secondary standards in 2020 is prior to full attainment of the current primary standard. All 

monitors analyzed are projected to attain a secondary standard of 30 dv in the 2020 base case. 

Given the 24-hr design value reductions that were included in simulating attainment of 15/35 in 

the 2020 base case, it is likely that all monitors will also attain a secondary standard of 28 dv 

when they attain the current primary standards.8

10.7 References

Abt Associates, Inc. 2001. Assessing Public Opinions on Visibility Impairment due to Air 

Pollution: Summary Report. Prepared for EPA Office of Air Quality Planning and 

Standards; funded under EPA Contract No. 68-D-98-001. Abt Associates Inc., Bethesda, 

MD. Available online at <http://www.epa.gov/ttncaaa1/t1/reports/vis_rpt_final.pdf>.

BBC Research & Consulting. 2003. Phoenix Area Visibility Survey. Draft Report. Available online 

at <http://www.azdeq.gov/environ/air/download/vis_021903f.pdf>.

Ely, D.W., Leary, J.T., Stewart, T.R., Ross, D.M. 1991. “The Establishment of the Denver Visibility 

Standard.” Presented at Air and Waste Management Association 84th Annual Meeting, 

June 16-21, Paper 91-48.4, 17pp. Available online at 

<http://www.albany.edu/cpr/stewart/Papers/T0210-ElyDenverVisStandard1991cap.pdf>.

Pitchford, M and W. Malm. 1994. “Development and Application of a Standard Visual Index.” 

Atmospheric Environment 28(5): 1049-1054.

 7

As described in Chapter 3, we apply a methodology of air quality ratios to estimate the emissions reductions 

needed to meet the current and proposed alternative levels for the primary standard. While this methodology 

can estimate how these emissions reductions will affect changes in the future-year annual design value and the 

corresponding response of the future-year 24-hr design value to changes in the annual design value, it is unable 

to estimate how each of the PM2.5 species will change with these emission reductions. Given that estimating 

changes in future-year visibility is dependent on the IMPROVE equation and how the PM2.5 species are 

projected to change in time, we are unable to estimate visibility design values for meeting the current and 

proposed alternative levels for the primary standard. 8 The projected 2020 base case design values for the secondary standard for the following monitors with id 

numbers 60658001 (located in Riverside, CA), 60290014 (located in Kern, CA), and 60990005 (located in 

Stanislaus, CA) are 29 dv, 30 dv, and 29 dv, respectively. The emissions reductions selected for simulating 

attainment of 15/35 in the 2020 base case resulted in the following reductions in the 24-hr design values for 

these three monitors: 11.1 μg/m3

, 21.9 μg/m3 and 5.3 μg/m3, respectively. Based on the trends presented in 

Wayland, 2012, we believe that these emissions reductions and 24-hr design value changes for simulating the 

current primary standard levels of 15/35 will be enough to lower the projected 2020 secondary standard design 

values for these three monitors to 28 dv or lower.
10-7

Pryor, S.C. 1996. “Assessing Public Perception of Visibility for Standard Setting Exercises.” 

Atmospheric Environment, vol. 30, no. 15, pp. 2705-2716.

Sisler, J.F. 1996. Spatial and seasonal patterns and long-term variability of the composition of 

the haze in the United States: an analysis of data from the IMPROVE network. CIRA 

Report, ISSN 0737-5352-32, Colorado State University.

U.S. Environmental Protection Agency (U.S. EPA). 2009. Integrated Science Assessment for 

Particulate Matter (Final Report). EPA-600-R-08-139F. National Center for 

Environmental Assessment—RTP Division. December. Available online at 

<http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=216546>.

U.S. Environmental Protection Agency (U.S. EPA). 2010. Particulate Matter Urban-Focused 

Visibility Assessment—Final Document (Corrected). Office of Air Quality Planning and 

Standards, Research Triangle Park, NC. July. Available online at 

<http://www.epa.gov/ttn/naaqs/standards/pm/data/FinalUFVAJuly2010.pdf>. 

U.S. Environmental Protection Agency (U.S. EPA). 2011. Policy Assessment for the Review of the 

PM NAAQS—Final Document. Office of Air Quality Planning and Standards, Research 

Triangle Park, NC. April. Available online at 

<http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_pa.html>.

Wayland, 2012. Technical Analyses to Support Surrogacy Policy for Proposed Secondary PM2.5

NAAQS under NSR/PSD Program. EPA docket #EPA-HQ-OAR-2012-XXXX.
10.A-1

APPENDIX 10.A

2017 MODELED DESIGN VALUES BY STATE, COUNTY, AND SITE

Table 10.A-1. 2017 Modeled Design Values by State, County, and Site

State County Site Design Value

Alabama Barbour 010050002 20

Jefferson 010730023 26

Jefferson 010732003 23

Jefferson 010731009 20

Madison 010890014 22

Mobile 010970003 21

Montgomery 011011002 22

Morgan 011030011 21

Russell 011130001 23

Arizona Maricopa 040130019 20

Maricopa 040139997 19

Maricopa 040139998 18

Maricopa 040137003 15

Maricopa 040137020 15

Pima 040191028 14

Arkansas Ashley 050030005 21

Pulaski 051190007 22

White 051450001 20

California Butte 060070002 24

Fresno 060190008 28

Imperial 060250005 23

Kern 060290014 30

Los Angeles 060371103 27

Plumas 060631009 22

Riverside 060658001 29

Sacramento 060670010 28

(continued)
10.A-2

Table 10.A-1. 2017 Modeled Design Values by State, County, and Site (continued)

State County Site Design Value

California (continued) Sacramento 060670006 25

San Diego 060730003 23

San Diego 060731002 23

Santa Clara 060850005 24

Stanislaus 060990005 29

Tulare 061072002 28

Ventura 061112002 23

Colorado Adams 080010006 19

El Paso 080410011 16

Mesa 080770017 19

Weld 081230008 18

Connecticut New Haven 090090027 24

D.C. Washington 110010042 24

Washington 110010043 24

Delaware Kent 100010003 23

New Castle 100032004 25

Florida Broward 120111002 17

Escambia 120330004 23

Hillsborough 120573002 19

Leon 120730012 21

Miami-Dade 120861016 17

Pinellas 121030026 21

Georgia Bibb 130210007 24

Chatham 130510017 21

Clarke 130590001 22

Coffee 130690002 19

De Kalb 130890002 22

Floyd 131150005 22

(continued)
10.A-3

Table 10.A-1. 2017 Modeled Design Values by State, County, and Site (continued)

State County Site Design Value

Georgia (continued) Muscogee 132150011 22

Richmond 132450091 23

Walker 132950002 23

Idaho Ada 160010010 23

Canyon 160270004 23

Illinois Cook 170310057 27

Cook 170310076 25

Cook 170314201 25

Du Page 170434002 27

Macon 171150013 25

Madison 171192009 25

Indiana Allen 180030004 25

Dubois 180372001 26

Elkhart 180390003 27

Henry 180650003 24

Lake 180890022 27

Lake 180892004 27

Marion 180970078 26

St Joseph 181411008 26

Vanderburgh 181630012 24

Iowa Linn 191130037 24

Polk 191530030 22

Scott 191630015 25

Kansas Sedgwick 201730010 21

Wyandotte 202090021 23

Kentucky Boyd 210190017 24

Daviess 210590005 26

Daviess 210590014 23

(continued)
10.A-4

Table 10.A-1. 2017 Modeled Design Values by State, County, and Site (continued)

State County Site Design Value

Kentucky (continued) Fayette 210670012 24

Jefferson 211110043 24

Jefferson 211110048 24

Kenton 211170007 23

Laurel 211250004 22

McCracken 211451004 23

Perry 211930003 21

Warren 212270007 24

Louisiana Bossier 220150008 20

East Baton Rouge 220330009 24

Maryland Anne Arundel 240030019 23

Baltimore 240053001 25

Prince Georges 240330030 23

Massachusetts Hampden 250130008 21

Suffolk 250250042 22

Michigan Allegan 260050003 25

Chippewa 260330901 22

Kalamazoo 260770008 25

Kent 260810020 25

Missaukee 261130001 21

Monroe 261150005 26

Washtenaw 261610008 26

Wayne 261630033 27

Wayne 261630001 25

Minnesota Hennepin 270530963 23

Mille Lacs 270953051 19

Olmsted 271095008 23

Ramsey 271230871 22

(continued)
10.A-5

Table 10.A-1. 2017 Modeled Design Values by State, County, and Site (continued)

State County Site Design Value

Mississippi Forrest 280350004 23

Grenada 280430001 20

Harrison 280470008 22

Hinds 280490018 21

Jones 280670002 23

Missouri Clay 290470005 22

Cooper 290530001 22

Jefferson 290990012 24

St Louis City 295100085 24

Ste Genevieve 291860005 22

Montana Lincoln 300530018 25

Missoula 300630031 23

Nebraska Douglas 310550019 22

Nevada Clark 320030561 22

Washoe 320310016 18

New Hampshire Hillsborough 330110020 23

Rockingham 330150014 19

New Jersey Camden 340070003 23

Middlesex 340230006 21

Morris 340273001 22

Union 340390004 25

New Mexico Bernalillo 350010023 14

New York Bronx 360050110 26

Bronx 360050083 25

Erie 360290005 24

Essex 360310003 17

Monroe 360551007 23

New York 360610062 25

(continued)
10.A-6

Table 10.A-1. 2017 Modeled Design Values by State, County, and Site (continued)

State County Site Design Value

New York (continued) Queens 360810124 24

Steuben 361010003 20

North Carolina Buncombe 370210034 22

Catawba 370350004 23

Cumberland 370510009 21

Davidson 370570002 23

Forsyth 370670022 23

Guilford 370810013 22

Lenoir 371070004 20

Mecklenburg 371190041 22

Rowan 371590021 22

Wake 371830014 22

North Dakota Burleigh 380150003 18

Cass 380171004 19

McKenzie 380530002 15

Ohio Butler 390171004 24

Cuyahoga 390350038 26

Cuyahoga 390350060 25

Franklin 390490081 25

Hamilton 390610040 24

Jefferson 390810017 26

Lawrence 390870010 25

Lorain 390930016 25

Lorain 390933002 21

Lucas 390950026 26

Mahoning 390990014 25

Montgomery 391130031 24

Stark 391510017 25

(continued)
10.A-7

Table 10.A-1. 2017 Modeled Design Values by State, County, and Site (continued)

State County Site Design Value

Ohio (continued) Stark 391510020 24

Summit 391530023 24

Oklahoma Ellis 400450890 17

Oklahoma 401091037 20

Tulsa 401431127 21

Oregon Jackson 410290133 24

Lane 410390060 19

Multnomah 410510246 22

Union 410610119 19

Pennsylvania Adams 420010001 23

Allegheny 420030064 28

Allegheny 420030008 24

Centre 420270100 24

Chester 420290100 25

Dauphin 420430401 26

Delaware 420450002 25

Erie 420490003 23

Lackawanna 420692006 22

Lancaster 420710007 27

Northampton 420950025 24

Perry 420990301 21

Philadelphia 421010055 26

Philadelphia 421010004 25

Philadelphia 421010136 23

Washington 421255001 20

Westmoreland 421290008 23

York 421330008 25

Rhode Island Providence 440070022 22

(continued)
10.A-8

Table 10.A-1. 2017 Modeled Design Values by State, County, and Site (continued)

State County Site Design Value

South Carolina Charleston 450190049 21

Charleston 450190046 19

Chesterfield 450250001 20

Greenville 450450009 23

Richland 450790019 22

South Dakota Minnehaha 460990006 21

Tennessee Davidson 470370023 22

Hamilton 470654002 23

Knox 470931020 22

Lawrence 470990002 20

Shelby 471570024 22

Shelby 471570047 22

Sullivan 471631007 24

Sumner 471650007 22

Texas Brewster 480430101 15

Dallas 481130069 20

El Paso 481410044 17

Harris 482011039 22

Utah Davis 490110004 25

Salt Lake 490353006 24

Utah 490494001 24

Vermont Chittenden 500070012 21

Virginia Bristol City 515200006 24

Henrico 510870014 23

Page 511390004 22

Roanoke City 517700014 23

Washington King 530330024 23

King 530330057 23

(continued)
10.A-9

Table 10.A-1. 2017 Modeled Design Values by State, County, and Site (continued)

State County Site Design Value

Washington (continued) King 530330032 22

King 530330048 21

King 530330080 20

Pierce 530530029 22

Spokane 530630016 21

West Virginia Kanawha 540391005 24

Kanawha 540390011 22

Marshall 540511002 22

Wisconsin Dodge 550270007 24

Kenosha 550590019 25

Manitowoc 550710007 24

Milwaukee 550790026 25

Taylor 551198001 21

Waukesha 551330027 25
11-1

CHAPTER 11

QUALITATIVE DISCUSSION OF EMPLOYMENT IMPACTS OF AIR QUALITY REGULATIONS

11.1 Introduction

Executive Order 13563 states that federal agencies should consider the effect of 

regulations on employment. According to the Executive Order, “our regulatory system must 

protect public health, welfare, safety, and our environment while promoting economic growth, 

innovation, competitiveness, and job creation. It must be based on the best available science” 

(Executive Order 13563, 2011). Although a stand-alone analysis of employment impacts is not 

typically included in a standard cost-benefit analysis,1 employment impacts are currently of 

particular concern due to recent economic conditions reflecting relatively high levels of 

unemployment. This chapter is intended to provide context for considering the potential 

influence of environmental regulation on growth and job shifts in the U.S. economy. Section 

11.2 addresses the particular influence of this proposed rule on employment. Section 11.3

presents a descriptive overview of the peer-reviewed literature relevant to evaluating the 

effect of air quality regulation on employment. Finally, in Section 11.4, we offer several 

conclusions.

11.2 Influence of NAAQS Controls on Employment

Peer-reviewed econometric studies that estimate the impact of air quality regulation on 

net overall employment and within the regulated sector converge on the finding that any net 

employment effects, whether positive or negative, have been small. This finding holds for even

major nationwide environmental regulations. Therefore, given the overall small effect 

environmental regulations have been shown to have on net employment in the regulated 

sectors, we do not expect them to have a significant impact on the overall economy.

Other factors affecting U.S. employment include cyclical, technological, demographic, 

and economic trends both in the United States and abroad. In this section, we focus on the 

studies most directly applicable to EPA analyses.

Estimating specific employment impacts from a new NAAQS standard is particularly 

challenging for two reasons. First, the NAAQS is a target level of public health protection that 

individual areas have flexibility to meet in a variety of ways, and the primary regulatory activity 

and implementation occur at the state or local level. Under these circumstances, states and 

localities are given considerable flexibility in choosing which strategies to adopt to meet the 

 1 This is the case except to the extent that labor costs are part of total costs in a cost-benefit analysis.
11-2

NAAQS target. State and local officials can consider employment impacts of various control 

strategies, as well as other factors, when designing their state implementation plans (SIPs). This 

makes it challenging to predict how specific sectors will be impacted and how those impacts 

vary across regions of the country. Analyses in the RIA are based on a particular NAAQS 

compliance scenario that reflects assumptions about control measures applied across all 

sectors and locations, specific control strategies adopted by the states and associated 

extrapolated costs. EPA believes this compliance scenario supports reasonably illustrative 

quantitative estimates of the potential overall economic effects of the revised NAAQS.

However, EPA does not consider this illustrative, aggregate compliance scenario to be 

sufficiently certain and precise to support quantitative projections of outcomes in particular 

locations, sectors, or markets, including labor markets, in light of the scarcity of applicable 

studies that can be used to generate such estimates. Therefore, this RIA does not include 

quantitative projections of aggregate shifts in employment.

Second, we anticipate that national employment levels will be changing during the 

period that the NAAQS is being implemented, a period that may be greater than 10 years for 

some areas, following designations of nonattainment. Although current unemployment rates 

remain high relative to historical averages largely due to the sharp increase in unemployment 

that began in early 2008 (U.S. Department of Labor, Bureau of Labor Statistics, 2012a), current

data suggest unemployment rates have been declining in recent months (U.S. Department of 

Labor, Bureau of Labor Statistics, 2012b). Policies to meet the NAAQS in all areas will not go 

into effect for several years. By this time we anticipate the economy will have had a chance to 

recover toward higher employment levels that more closely approximate full employment. In 

addition, over a period of 10 years or longer, potentially significant changes in technology, 

growth and distribution of economic activities, and other key determinants of local and national 

labor market conditions further complicate projections of future employment and the potential 

incremental effect of regulatory programs.

Although a quantitative assessment of employment consequences of today’s proposed 

revision to the national ambient PM standards remains beyond the reach of available data and 

modeling tools, EPA is in the process of supporting the development of tools and research that 

could assist in the future. In the interim, some insights on the potentially relevant 

consequences of revising ambient air pollution standards can be gained by considering 

currently available literature, including its limitations. In light of these challenges, Section 11.3 

focuses on qualitative insights from currently available peer-reviewed literature on the impact 

of air quality regulations in general.
11-3

11.3 The Current State of Knowledge Based on the Peer-Reviewed Literature

There is limited peer-reviewed econometric literature estimating employment effects of 

environmental regulations. We present an overview here, highlighting studies with particular 

relevance for NAAQS. Determining the direction of employment effects in the regulated 

industries is challenging because of competing effects. Complying with the new or more 

stringent regulation requires additional inputs, including labor, and may alter the relative 

proportions of labor and capital used by regulated firms in their production processes.

When the economy is at full employment, an environmental regulation is unlikely to 

have a considerable impact on net employment in the long run. Instead, labor would primarily 

be reallocated from one productive use to another (e.g., from producing electricity or steel to 

producing pollution abatement equipment). Theory supports the argument that, in the case of 

full employment, the net national employment effects from environmental regulation are likely 

to be small and transitory (e.g., as workers move from one job to another). There is reason to 

believe that when the economy is operating at less than full employment environmental 

regulation could result in a short-run net increase in employment.2 Several empirical studies 

suggest that net employment impacts may be positive but small even in the regulated sector. 

Taken together, the peer- reviewed literature does not contain evidence that environmental 

regulation would have a notable impact on net employment across the whole economy.

This discussion focuses on both short- and long-term employment impacts in the 

regulated industries, as well as on the environmental protection sector for construction of 

needed pollution control equipment prior to the compliance date of the regulation. EPA is 

committed to using the best available science and the relevant theoretical and empirical 

literature in this assessment and is pursuing efforts to support new research in this field.

11.3.1 Immediate and Short-Run Employment Impacts

Environmental regulations are typically phased in to allow firms time to invest in the 

necessary technology and process changes to meet the new standards. Whatever effects a 

regulation will have on employment in the regulated sector will typically occur only after a 

regulation takes effect, or in the long term, as new technologies are introduced. However, the 

environmental protection sector (pollution control equipment) often sees immediate 

employment effects. When a regulation is promulgated, the first response of industry is to 

order pollution control equipment and services to comply with the regulation when it becomes 

effective. This can produce a short-term increase in labor demand for specialized workers 

 2 See Schmalansee and Stavin (2011)
11-4

within the environmental protection sector related to design, construction, installation and 

operation of the new pollution control equipment required by the regulation. (see Schmalansee 

and Stavins, 2011; Bezdek, Wendling, and Diperna, 2008). 

As the NAAQS are implemented, it is possible that the regulated sector will experience 

short-run changes in employment. Because it is the states’ responsibility to design their state 

implementation plans (SIPs) over the next few years, we cannot assess the short-term effects of 

those SIPs on the regulated sector with sufficient precision to quantify the resulting incremental 

effects on employment. However, as previously noted, even in a full employment case, there 

may be transitory effects as workers change jobs. Some workers may need to retrain or 

relocate in anticipation of the new requirements or require time to search for new jobs, while 

shortages in some sectors or regions could bid up wages to attract workers.

It is important to recognize that these adjustment costs can entail local labor 

disruptions, and, although the net change in the national workforce might be small, gross 

reductions in employment can still have negative impacts on individuals and communities. The 

peer-reviewed literature that is currently available is focused on medium- and long-term 

employment impacts and does not offer much insight into the short-term balance between 

increased employment in the environmental protection sector and possible decreased 

employment in some regulated sectors.

11.3.2 Long-Term Employment Impacts on the Regulated Industry 

Determining the direction of net employment effects in regulated industries is 

challenging because of competing effects. Morgenstern, Pizer, and Shih (2002) demonstrate 

that environmental regulations can be understood as requiring regulated firms to add a new 

output (environmental quality) to their product mix. Although legally compelled to produce this 

new output, regulated firms have to finance this additional production input with the proceeds 

of sales of their other (market) products. The current literature on employment impacts of air 

quality regulations can be disaggregated into two types of approaches or models: 1) structural 

and 2) reduced-form models. Two papers that present a formal structural model of the 

underlying profit maximizing/cost minimizing problem of the firm are Berman and Bui (2001) 

and Morgenstern, Pizer, and Shih (2002). Berman and Bui (2001) developed an innovative 

approach to estimating the effect of environmental regulations designed to meet a NAAQS 

(e.g., ozone and NOX) requirement in California on employment. Berman and Bui’s model 

allows environmental regulation to operate via two separate mechanisms: 1) the output 

elasticity of labor demand and 2) the effect of pollution abatement activities on demand for 
11-5

variable factors, combined with the marginal rates of technical substitution between 

abatement activity and variable factors, including labor. Berman and Bui demonstrate, using 

economic theory, that the overall net effect of environmental regulation on employment, 

predicted by this model, is ambiguous. Neoclassical economic theory predicts that the output 

effect is, in most cases, negative, while the direction of the second, composite effect is 

indeterminate making the overall net effect ambiguous. 

Morgenstern, Pizer, and Shih (2002) developed a similar structural model to Berman and 

Bui’s (2001) model. Their model focuses on three mechanisms whereby environmental 

regulation may impact employment in regulated industries. First, is the demand, or output, 

effect, where new compliance costs increase the cost of production, raising prices and thereby 

reducing consumer demand, which, in turn, reduces labor demand. Second, is the cost effect,

which increases the demand for inputs, including labor, as more inputs are now required to 

produce the same amount of output. Finally, the factor-shift effect notes how regulated firms’ 

production technologies may be more or less labor intensive after complying with the 

regulation (i.e., more/less labor is required relative to capital per dollar of output), implying an 

ambiguous overall net effect on labor demand. Conceptually, this theoretical approach, which is 

very similar to Berman and Bui’s approach, could be applied to NAAQS. However, Morgenstern 

et al.’s empirical approach uses pollution abatement expenditures for only four highly 

polluting/regulated sectors (pulp and paper, plastics, steel, and petroleum refining) to estimate 

effects on net employment; therefore, their empirical results are not directly applicable to the 

full range of manufacturing and nonmanufacturing industries affected by NAAQS. Regardless, 

their work represents one of the most rigorous attempts to quantify the net employment 

impacts of regulation on the regulated sector. Morgenstern et al. conclude from their empirical 

results that increased pollution abatement expenditures generally have not caused a significant 

change in net employment in those four sectors. More specifically, their results show that, on 

average across the industries studied, each additional $1 million ($1987) spent on pollution 

abatement results in a (statistically insignificant) net increase of 1.5 jobs.

Berman and Bui (2001) use their model to empirically examine how an increase in local 

air quality regulation that reduces NOX emissions as a precursor to ozone and PM10 affects 

manufacturing employment in the South Coast Air Quality Management District (SCAQMD), 

which incorporates Los Angeles and its suburbs. During the time frame of their study, 1979 to 

1992, the SCAQMD enacted some of the country’s most stringent air quality regulations. Using 

SCAQMD’s local air quality regulations, which are more stringent than federal and state 

regulations, Berman and Bui identify the effect of environmental regulations on net 
11-6

employment in the regulated sectors.3 They compare changes in employment in affected plants 

to those in other plants in the same industries but in regions not subject to the local 

regulations. The authors find that “while regulations do impose large costs, they have a limited 

effect on employment”—even when exit and dissuaded entry effects are considered (Berman 

and Bui, 2001, p. 269). Their conclusion is that local air quality regulation “probably increased 

labor demand slightly” but that “the employment effects of both compliance and increased 

stringency are fairly precisely estimated zeros [emphasis added], even when exit and dissuaded 

entry effects are included” (Berman and Bui, 2001, p. 269). In their view, the limited effects 

likely arose because 1) the regulations applied disproportionately to capital-intensive plants 

with relatively little employment, 2) the plants sold to local markets where competitors were 

subject to the same regulations (so that sales were relatively unaffected), and 3) abatement 

inputs served as complements to employment. Although Berman and Bui focus on more sectors 

than Morgenstern et al. and focus specifically on air regulations, the study only examined 

impacts in Southern California and impacts may differ in other nonattainment areas.

Other studies, including Henderson (1996), Becker and Henderson (2000), Greenstone 

(2002), and List et al. (2003), have taken a reduced-form approach to ask a related but quite 

different question regarding the impact of environmental regulation on economic activity. All of 

these studies examined the effect of attainment status, with respect to NAAQS, on various 

forms of economic activity (e.g., employment growth, plant openings and closings, investment).

Polluting plants already located in and new polluting plants wanting to open in nonattainment 

counties (counties not in compliance with one or more NAAQSs) are likely to face more 

stringent air pollution regulations to help bring them into compliance. Thus, the stringency in 

environmental regulations may vary spatially, which may affect the spatial distribution of 

economic activity but not necessarily the overall level of economic activity. These studies find 

limited evidence that employment grows more slowly, investment is lower, or fewer new 

polluting plants open in nonattainment areas relative to attainment areas. However, this 

evidence does not mean that there is less aggregate economic activity as a result of

environmental regulation nor does it provide evidence regarding absolute growth rates; it 

simply suggests that the relative growth rate of some sectors may differ between attainment 

and nonattainment areas. The approach used in all of these other studies is not capable of 

estimating net employment effects as would be necessary for a national rulemaking, only 

certain aspects of gross labor flows in selected areas.

 3 Note, like Morgenstern, Pizer, and Shih (2002), this study does not estimate the number of jobs created in the 

environmental protection sector.
11-7

11.4 Conclusion

The long-term effects of a regulation on the environmental protection sector (which 

provides goods and services to the regulated sector) are difficult to assess. Employment in the 

industry supplying pollution control equipment is likely to increase with the increased demand 

from the regulated industry for the equipment.4 According to U.S. Department of Commerce 

(2010) data, by 2008, there were 119,000 environmental technology (ET) firms generating 

approximately $300 billion in revenues domestically (2% of national gross domestic product 

[GDP]), producing $43.8 billion in exports (2% of total exports), and supporting nearly 1.7 

million jobs (0.93% of total jobs). Air pollution control accounted for 18% of the domestic ET 

market and 16% of exports. Small and medium-size companies represent 99% of private ET 

firms, producing 20% of total revenue. The remaining 1% of companies are large companies 

supplying 49% of ET revenue (OEEI, 2010).

5

As described above, deriving estimates of how regulations will impact economy-wide 

net employment is a difficult task, especially in the case of setting a new NAAQS, given that 

economic theory predicts that the net effect of an environmental regulation on regulated 

sectors and the overall economy is indeterminate (not necessarily positive or negative). Peerreviewed econometric studies that use a structural approach, applicable to overall net effects in 

the regulated sectors, converge on the finding that any net employment effects of 

environmental regulation in general, whether positive or negative, have been small and have 

not affected employment in the economy in a significant way.

11.5 References

Becker, R. and V. Henderson (2000). “Effects of Air Quality Regulations on Polluting Industries.”

Journal of Political Economy 108(2): 379-421.

Berman, E. and L. T. M. Bui (2001). “Environmental Regulation and Labor Demand: Evidence 

from the South Coast Air Basin.” Journal of Public Economics 79(2): 265-295.

Bezdek, R. H., R. M. Wendling, and P. Diperna (2008). “Environmental Protection, the Economy, 

and Jobs: National and Regional Analyses.” Journal of Environmental Management 

86(1): 63-79.

Executive Order 13563 (January 21, 2011). “Improving Regulation and Regulatory Review. 

Section 1. General Principles of Regulation.” Federal Register 76(14): 3821-3823.

 4 See Bezdek et al. (2008), for example, and U.S. Department of Commerce (2010).

5 To calculate the percentages, total national 2008 GDP ($14,369.1 billion), exports ($1,842.68 billion), and

employment (181.75 million employees) were obtained from Bureau of Economic Analysis, U.S. Census Bureau 

and Woods & Poole, respectively.
11-8

Greenstone, M. (2002). “The Impacts of Environmental Regulations on Industrial Activity: 

Evidence from the 1970 and 1977 Clean Air Act Amendments and the Census of 

Manufactures.” Journal of Political Economy 110(6): 1175-1219.

Henderson, V. (1996). “Effects of Air Quality Regulation.” The American Economic Review 86(4): 

789-813.

List, J. A., D. L. Millimet, P. G. Fredriksson, and W. W. McHone (2003). “Effects of Environmental 

Regulations on Manufacturing Plant Births: Evidence from a Propensity Score Matching 

Estimator.” The Review of Economics and Statistics 85(4): 944-952.

Morgenstern, R. D., W. A. Pizer, and J-S. Shih (2002). “Jobs Versus the Environment: An 

Industry-Level Perspective.” Journal of Environmental Economics and Management 

43(3): 412-436.

Schmalansee, R. and R. Stavins (2011). “A Guide to Economic and Policy Analysis for the 

Transport Rule.” White Paper. Boston, MA: Exelon Corp.

U.S. Department of Commerce, International Trade Administration (2010, April). Environmental 

Industries Fact Sheet, using 2008 data from Environmental Business International, Inc. 

http://web.ita.doc.gov/ete/eteinfo.nsf/068f3801d047f26e85256883006ffa54/4878b7e2

fc08ac6d85256883006c452c?OpenDocument.

U.S. Department of Labor, Bureau of Labor Statistics (2012a). Databases, Tables & Calculators 

by Subject. http://data.bls.gov/timeseries/LNS14000000. Accessed April 16, 2012.

U.S. Department of Labor, Bureau of Labor Statistics (2012b, April 6). “The Employment 

Situation—March 2012.” News Release. http://www.bls.gov/news.release/pdf/empsit.pdf. 

Accessed April 16, 2012.
United States

Environmental Protection

Agency

Office of Air Quality Planning and Standards

Health and Environmental Impacts Division

Research Triangle Park, NC

Publication No. EPA-452/R-12-003

June 2012