The cover illustration is an air quality map of the u.s. which 

displays the highest second daily maximum 1-hour average ozone 

concentration by metropolitan statistical area (MSA) for 1988. 

(National Air Quality and Emission Trends Report, 1988, EPA-450/4-001) 

• 

This report has been reviewed by the Office of Air Quality 

Planning and Standards, EPA, and approved for publication. 

Mention of trade names or commercial products is not intended to 

constitute endorsement or recommendation for use. 
Preface 

This document was finalized in June 1989 and reviews 

information from relevant studies of 0 3 health and welfare 

effects and of exposure and risk analysis through early 1989. 

The assessment contained in this staff paper reflects information 

in the documents "Air Quality criteria for Ozone and Other 

Photochemical oxidants" (EPA-600/8-84-020F) and "Summary of 

Selected New Information on Effects of Ozone on Health and 

Vegetation: Supplement to Air Quality Criteria for Ozone and 

Other Photochemical oxidants" (EPA-600/8-88/1-Sa). 
i 

Acknowledgements 

This staff paper is the product of the Office of Air Quality 

Planning and Standards (OAQPS). Tables and Figures not otherwise 

cited are original to this report. The principal authors include 

Dr. David J. McKee, Ms. Pamela M. Johnson, Mr. Thomas R. McCurdy, 

and Mr. Harvey M. Richmond. This report has been improved by 

comments from other staff within OAQPS, the Office of Research 

and Development, the Office of Policy and Program Evaluation, and 

the Office of General counsel within EPA. Three drafts were 

formally reviewed by the Clean Air Scientific Advisory Committee 

and comments incorporated. Particularly important in the final 

review of this staff paper was the technical and editorial 

support provided by Ms. Victoria Atwe~l and the clerical and 

editorial support of Mrs. Patricia R. crabtree and Mrs. Barbara 

• 

Miles. 

Helpful comments and suggestions were also submitted by a 

number of independent scientists, by officials from the State 

environmental agencies of Illinois, Minnesota, California and 

Texas, by the Department of the Navy, and the Department of 

Energy, and by environmental and industrial groups including the 

Natural Resources Defense Council, the American Lung Association, 

the Chemical Manufacturers Association, the American Petroleum 

Institute, and the Motor Vehicle Manufacturers Association. 
ii 

Project Team For 

Review of the National Ambient Air Quality Standards for Ozone 

Dr. David J. McKee, Project Manager and Author of Chapters I 

through III and VI through VIII 

Ambient Standards Branch, Air Quality Management Division 

Office of Air Quality Planning and Standards (MD-12) 

U.S. Environmental Protection Agency 

Research Triangle Park, N.C. 27711 

Ms. Pamela M. Johnson, Author of Chapters IX through XI 

Ambient Standards Branch, Air Quality Management Division 

Office of Air Quality Planning and Standards (MD-12) 

U.S. Environmental Protection Agency 

Research Tri~ngle Park, N.C. 27711 

Mr. Thomas R. McCurdy, Author of Chapters IV and V and Appendix A 

Ambient Standards Branch, Air Quality Management Division 

Office of Air Quality Planning and Standards (MD-12) 

u.s. Environmental Protection Agency 

Research Triangle Park, N.C. 27711 

Mr. Harvey M. Richmond, Author of Section VII.B. 

Ambient Standards Branch, Air Quality Management Division 

Office of Air Quality Planning and Standards (MD-12) 

u.s. Environmental Protection Agency 

Research Triangle Park, N.C. 27711 
iii 

u.s. Environmental Protection Agency 

Science Advisory Board . Clean Air Scientific Advisory Committee 

Subcommittee on ozone 

Chairman 

Dr. Roger 0. McClellan 

CIIT 

Post Office Box 12137 

Research Triangle Park, NC 27709 

Members 

Dr. Eileen G. Brennan 

Department of Plant Pathology 

Martin Hall, Room 213 

Lipman Drive 

Cook College-NJAES, Rutgers Univ. 

P.O. Box 231 

New Brunswick, New Jersey 08903 

Dr. Edward D. Crandall 

Division of Pu~monary Medicine 

Starr Pavilion 505 

Cornell Medical College 

1300 York Avenue 

New York, New York 10021 

Dr. James D. Crapo 

Box 3177 

Duke University Medical 

Durham, North Car~lina 

Dr. Robert Frank 

Center 

27711 

Professor of Environmental Health 

Sciences 

Johns Hopkins School of Hygiene and 

Public Health 

615 N. Wolfe Street 

Baltimore, Maryland 21205 

Prof. A. Myrick Freeman, III 

Department of Economics 

Bowdoin College 

Brunswick, Maine 04011 
Dr. Jay s. Jacobson 

Plant Physiologist 

Boyce Thompson Institute 

Tower Road 

Ithaca, New York 14853 

Dr. Jane Q. Koenig 

Research Associate Professor 

Department of Environmental 

Health SC-34 

University of Washington 

Seattle, Washington 98195 

Dr. Timothy Larson 

Environmental Engineering and 

Science Program 

Department of Civil Engineering 

FX-10 

University of Washington 

Seattle, Washington 98195 

iv 

Dr. Morton Lippmann, Professor 

Institute of Environmental Medicine 

NYU Medical center 

Tuxedo, New York 10987 

. Prof. M. Granger Morgan 

Head, Department of Engineering 

and Public Policy 

Carnegie-Mellon University 

Pittsburgh, Pennsylvania 15253 

Dr. D. Warner North, Principal 

Decision Focus, Inc. 

Los Altos.Office Center 

Suite 200 

4984 El Camino Real 

Los Altos, California 94022 

Dr. Gilbert s. Omenn, 

Professor and Dean 

School of Public Health and 

Community Medicine SC-30 

University of washington 

Seattle, Washington 98195 

Dr. Robert D. Rowe 

Energy and Resource Consultants 

P.O. Drawer 0 

Boulder, Colorado 80306 
Dr. Marc B. Schenker, Director 

Occupational and Environmental 

Health Unit 

University of California 

Davis, California 95616 

Mr. Stephen Smallwood 

Air Pollution Control Program 

Manager 

v 

Bureau of Air Quality Management 

Florida Department of Environmental 

Regulation 

Twin Towers Office Bldg. 

2600 Blair Stone Road 

Tallahassee, Florida 32301 

Dr. George Taylor 

Environmental Sciences Division 

P.O. Box X 

Oak Ridge National Laboratory 

Oak Ridge, Tennessee 37831 

Dr. Mark J. Utell 

Pulmonary Unit - Box 692 

Strong Memorial Hospital 

Rochester, New York 14642 

Dr. Jerry Wesolowski 

1176 Shattuck Avenue 

Berkeley, California 94704 

Dr. George T. Wolff 

Senior Staff Research Scientist 

General Motors Research Labs 

Environmental Science Department 

Warren, Michigan ·48090 
vi 

EPA Reviewers 

Mr. Allen c. Basala (MD-12) 

Office of Air Quality Planning and Standards, OAR U.S. EPA 

RTP, NC 27711 

Mr. Frank L. Bunyard (MD-12) 

Office of Air Quality Planning and Standards, OAR 

U.S. EPA 

RTP, NC 27711 

Dr. Thomas c. Curran (MD-14) 

Office of Air Quality Planning and Standards, OAR 

U.S. EPA 

RTP, NC 27711 

Mr. Robert Fegley (PM-221) 

Office of Policy Analysis, OPPE 

·U.S. EPA 

Waterside Mall 

401 M Street, SW 

Washington, DC 20460 

Mr. Lewis Felleisen 

Air Programs & Engineering Branch 

U.S. EPA, Region III 

Curtis Building 

6th & Walnut Streets 

Philadelphia, PA 19106 

Mr. Robert A. Flaak (A-107F) 

Science Advisory Board, OA 

U.S. EPA 

Waterside Mall 

401 M street, SW 

Washington, DC 20460 

Dr. J.H.B. Garner (MD-52) 

Environmental Criteria and Assessment Office, ORO 

U.S. EPA 

RTP, NC 27711 

Mr. Gerald K. Gleason (LE-132A) 

Office of General counsel 

U.S. EPA 

Waterside Mall 

401 M Street, sw 

.Washington, D"C 20460 
vii 

Dr. Judith A. ~raham (MD-52) 

Environmental Criteria and Assessment Office, ORO 

U.S. EPA 

RTP, NC 27711 

Dr. · Lester D. Grant (MD-52) 

Environmental Crit~ria and Assessment Office, ORO 

U.S. EPA 

RTP, NC 27711 

Dr. Carl G. Hayes (MD-55) 

Health Effects Research Laboratory, ORD 

U.S. EPA 

RTP, NC 27711 

Dr. Donald H. Horstman (MD-58) 

Health Effects Research Laboratory, ORO 

U.S. EPA 

. RTP I. NC 27711 

Mr. William F. Hunt (MD-14) 

Office of Air Quality Planning and Standards, OAR -

U.S. EPA 

RTP, NC 27711 

Mr. Michael H. Jones (MD-12) 

Office of Air Quality Planning and Standards, OAR 

U.S. EPA 

RTP, NC 27711 

Mr. Bruce C. Jordan (MD-12) 

Office of Air Quality Planning and Standards, OAR 

U.S. EPA 

RTP, NC 27711 

Mr. Bruce Madariaga (MD-12) 

Office of Air Quality Planning and Standards, OAR 

U.S. EPA 

RTP, NC 27711 

Dr. William F. McDonnell (MD-58) 

Health Effects Research Laboratory, ORO 

U.S. EPA 

RTP, NC 27711 

Mr. Thomas B. McMullen (MD-52) 

Environmental Criteria and Assessment Office, ORD 

U.S. EPA 

RTP, NC 27711 
viii 

Dr. Edwin L. Meyer (MD-14) 

Office of Air Quality Planning and Standards, OAR U.S. EPA 

RTP, NC 27711 

Dr. John J. O'Neil (MD-58) 

Health Effects Research Laboratory, ORD U.S. EPA 

RTP, NC 27711 

Mr. Norman c. Possiel (MD-14) 

Office of Air Quality Planning and standards, OAR 

U.S. EPA 

RTP, NC 27711 

Mr. James A. Raub (MD-52) 

Environmental Criteria and Assessment Office, ORO 

U.S. EPA 

RTP, NC 27711 

Mr. Robert Rose (ANR-443) 

Office of Policy, Planning, and Evaluation 

U.S. EPA 

Waterside Mall 

401 M street, SW 

Washingten, DC 20460 

Mr. Joel Scheraga (PM-221) 

Office of Policy Analysis, OPPE 

U.S. EPA 

Waterside Mall 

401 M Street, sw 

Washington, DC 20460 

Mr. William P. Smith (PM-223) 

Office of Stds. & Regulations, OPPE 

U.S. EPA 

Waterside Mall 

401 M Street, SW 

Washington, DC 20460 

Dr. Joseph Sommers 

Emission Control Technology Division 

Office of Mobile Sources, OAR 

Ann Arbor, MI 48105 

Ms. Beverly E. Tilton (MD-52) 

Environmental Criteria and Assessment Office, ORD 

U.S. EPA 

RTP, NC 27711 
Dr .. Dave T. Tingey 

Envir9nmental Research 

Laboratory--Corvallis/ORO 

200 S.W. 35th Street 

~orvallis, OR 97333 

ix 
X 

Table of Contents 

Acknowledgements. • • • • • • • • • • • • • • • • • • . • • • • • • • • • • • • • • • • • • • • • • • i 

Project Team for Review . of the National Ambient Air 

Quality Standards for Ozone ....... ~ ....................... ii 

Clean Air Scientific Advisory Committee Subcommittee 

on ozone ...................... . ......•............. . . .. . • . iii 

EPA Reviewers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi 

Table of Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x 

List of Figures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . xv 

List of Tables. . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xviii 

Execut1 . ' ve Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi 

I . Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . I -1 

II. Background ............................................ II-1 

III. Approach......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III-1 

IV. Ambient Ozone Concentrations in Urban and Rural Areas' IV-1 

A. Urban Areas .••••....•..••••••.•••••••.••••.•••.... IV-1 

B. Non-MSA Areas. • • . . . . . • • • • • • • • • • • • • • • • . • • • • . . • • • • . . IV-2 

c. Natural Ozone Background .... . ..................... IV-3 

v. Ozone Exposure Analysis ............................... V-1 

A. Overview of the Ozone NAAQS Exposure Model ........ V-1 

B. Air Quality Concentrations in Microenvironments ... V-2 

C. Simulation of Population Movement ....... -. . . . . . . . . . V-4 

D. Study Areas Modeled in Ozone NAAQS Exposure 

Model. • • • • • • • • • • • • • • • . • • • • • • • • • • • • • • • • • • • • • • • • . • • • V -4 

E. Exercise Modeling in Ozone NAAQS 

Exposure Model ••••••...••••••••••••••• ·. • • . • . • • • . . . V-7 

F. Eight-Area Aggregated Estimates of Population 

Exposure to Alternative ozone Standards ..•........ V-8 
xi 

Page 

G. Caveats and Limitations ........................... V-13 

VI. Factors Relevant to Review of the Primary Standard(s) for Ozone .......... .................................... VI-1 

A. · Ozone Absorption and Mechanisms of Effects ........ VI-1 

B. Factors Affecting Susceptibility to Ozone ......... VI-3 

1. Age .......................................... VI-4 

2 . sex. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VI-5 

3 . Smoking Status. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VI -6 

4. Nutritional Status ........................... VI-7 

5. Environment~l Stresses ..............•........ VI-8 

6. Exercise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VI -8 

c. Potentially susceptible Groups ................... VI-9 

1. Individuals Having Preexisting Disease ....... VI-9 

,. 

2. Exercising Individuals ....................... VI-13 

VII. Assessment of Health Effects and Related Health Issues 

Considered in Selecting Primary standard(s) for 

Qz.one .............................••••................ VII-1 

A. Health Effects of Concern ........................ VII-1 

1. Alterations in Pu~monary Function ........... VII-2 

2. Symptomatic Effects ......................... VII-15 

3. Exercise Performance ........................ VII-20 

4. Bronchial Reactivity and Inflammation ....... VII-22 

5. Aggravation of Existing Respiratory Disease VII-24 

6. Morphological Effects ....................... VII-28 

7. Effects of ozone on Host Defense Mechanisms 

in Experimental Animals •.....••............ VII-32 

8. Extrapulmonary Effects ..•................... VII-35 
xii 

B. Pulmonary Function and Symptom Health Risk 

Assessment ....................................... VII-37 

l. Overview of Lung _Function and Symptom Risk Assessment ............................. VII-37. 

2. Benchmark Risk Results ...................... VII-40 

3. Headcount Risk Results ••••............ ·-···· VII-45 

4. Caveats and Limitations .•................... VII-50 

c. Related Health Effects Issues •................... VII-52 

1. Adverse Respiratory Health Effects of 

Acute Ozone Exposure ....•................... VII-53 

2. Attenuation of Acute Pulmonary Effects ...... VII-56 

3. Relationship Between Acute and Chronic 

Effects ............... ...................... VII-58 

4. Effects of Other Photochemical Oxidants ..... VII-62 

. 5. Interactions with Other Pollutants .......... VLI-63 

VIII. Staff Conclusions and Recommendations for Ozone 

Primary Standard(s) .............................. VIII-1 

A. Pollutant Indicator .............•........... VIII-1 

B·. Form of the Standard ........................ VIII-4 

c. Averaging Time(s) ........................... VIII-5 

D. Level of the Primary Standard(s) ............ VIII-9 

E. summary of staff Recommendations ............ VIII-20 

IX. Factors Relevant to the Review of the Secondary Standard for Ozone .................................... IX-1 

A. Mechanisms of Action for Vegetation .............. IX-1 

1. Biochemical Response. . . . . . . . . . . . . . . . . . . . . . . . IX -2 

2. Physiological Response ..•.•................. IX-3 

B. Factors Affecting Plant Response ................. IX-5 

1. Biological Factors .......................... IX-6 
xiii 

a. Plant Genetics ....•......•.............. IX-6 b. Developmental Factors .................. IX-7 

c. Pat~ogen and Pest Interactions 

w1th Ozone ...............•........... IX-7 

2. Physical Factors ..........•................ ·. IX-8 

3. Chemical Factors ........................ ·. . . . IX-9 

a. Multiple Pollutants .................... IX-9 b. Chemical Sprays ........................ IX-11 

c. Heavy Metals. . . . . . . . . . . . . . . . . . . . . . . . . . . IX-11 

X. Assessment of Welfare Effects and Related Welfare Issues Considered in Selecting Secondary Standard(s) for Ozone. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X-1 

A. Vegetation Effects ............................... X-2 

1. Types of Exposure Effects ...•............... X-2 

a. Visible Foliar Injury Effects .......... X-3 b. Growth and Yield Effects ............... X-6 

1. Open Top Chamber Studies .......... X-7 2. Greenhouse and Controlled 

Environment Studies .•............. X-13 3. Ambient Air Exposure Studies ...... X-14 

2. Related Vegetation Issues ................... X-20 

a. Empirical Models Used to Develop Exposure Response Relationships ........ X-20 b. Statistics ·Used to Characterize 

Ozone Exposures ........................ X-21 

c. Exposure and Response to 

Peroxyacetyl Nitrate ...•..•............ X-23 d. Economic Assessments of Agriculture .... X-24 

B. Natural Ecosystem Effects ........................ X-26 

1. Forest Ecosystems ........................... X-27 

a. Effects on Plant Processes ............. X-29 b. Effects on Growth .................... · .. X-31 

c. Ecosystem Responses: The San 

Bernardino Study . . . . . . • . . • . . . . . . . . . . . . . X-3 8 

2. Interrelated Ecosystems ..........•.......... X-40 

a. Aquatic Ecosystems .......•............. X-40 b. Agricultural Ecosystems ................ X-40 
xiv 

Page 

C. Materials Damage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X-41 

1. Elastomers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x -4 2 

2. Textile Fibers and Dyes ..................... X-43 

3. Paints. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X-45 

4. Conclusion .................................. X-45 

D. Effects on Personal Comfort and Well Being ....... X-45 

E. Related Welfare Effects Information and Issues ... X-46 

1. Air Quality Analyses ........................ X-49 

2. Crop Loss Estimates .................. _ ... ~ ; . . . X-50 

3 . Averaging Times. . . . . . . . . . . . . . . . . . . . . . . . . . . . . x.:...54 

a. NCLAN/CERL Reanalysis .................. X-54 

b. New Studies ............................ X-62 

4. Forest Risk Assessment ...................... X-66 

XI. Staff Conclusions and Recommendations Regarding the 

Secondary Standard ( s) ........... .'. . . . . . . . . . . . . . . . . . . . . XI -1 ... 

A. Pollutant Indicator .............................. XI-1 

B. Form of the Standard and Averaging Time(s) ....... XI-3 

c. Level of standard ...................•............ XI-10 

D. Summary of Conclusions ........................... XI-16 

Appendix A. Air Quality .... : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1 

Appendix B. Glossary of Pulmonary Terms and Symbols ....... B-1 

Appendix c. CASAC Closure Letter .......................... C-1 

References 
VII-1 

VII-2 

VII-3 

VII-4 

VII-5 

VII-6 

VII-7 

VII-8 

X-1 

X-2 

X-3 

XV 

List of Figures 

Group Mean Decrements in 1-sec Forced Expiratory 

Volume During 2-hour ozone Exposures with Different 

Levels of Intermitt~nt Exercise ....•............. VII-4 

Fraction of Heavily Exercising Population 

Experiencing ~ 10% and > 20% Change in 1-sec 

Forced Expiratory Volume Due to Various Ozone 

Leve 1 s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VI I -11 

Fraction of Heavily Exercising Population 

Experiencing Mild and Moderate Symptoms 

Due to Various Ozone Levels ...................... VII-17 

Fraction of Heavily Exercising Population Experiencing Lower Respiratory Symptoms Due to Various 

Ozone _Levels ..................................... VII-18 

Benchmark Risk in St. Louis for 1-sec Forced 

Expiratory Volume Decrements of > 10% and 

> 20%, Under Heavy Exercise, for Three 

Exposure-Response Data Sets (Avol, Kulle, and 

McDonnell) ....................................... VII-43 

Benchmark Risk in St. Louis for Chest Discomfort 

Symptoms (any and moderatejsevere), under Heavy 

Exercise, for Three Exposure-Response Data Sets 

(Avol, Kulle, and McDonnell) ..................... VII-44 

Expected Headcount (pulmonary function) 

Aggregated for Eight U.S. Urban Areas With a 

Total Population of 9.3 Million (number 

of heavily exercising people responding during 

the ozone season) .....................•....... ... VII-47 

Expected Headcount (chest discomfort) Aggregated 

for Eight u.s. Urban Areas With a Total Population of 9.3 Million (number of heavily 

exercising people responding during the ozone 

season) ........................................ . . ~JII-48 

Examples of the Effects of ozone on the Yield of 

Soybean and Wheat Cultivars ...................... X-9 

Examples of the Effects of Ozone on the Yield of 

Cotton, Tomato, and Turnip ....................... X-10 

Eastern White Pine - Comparisons Across Expert 

Judgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X -7 3 
xvi 

Page 

A-1 Correlations Among Short- and Long-Term Air Quality Indicators in MSAs (Using 2nd High) .............. A-10 

A-2 Correlations Among Short- and Long-Term Air Quality Indicators in ·MSAs (Using ExEx) .................. A-12 

A-3 Proportion (In Percent) of Urban Sites Exceeding· Expected Number of days with an 8-Hour Daily Maximum 

Average > .08 ppm for Five 1-Hour Daily Maximum 

Standards ............ . .................. ......... A-13 

A-4 Proportion (In Percent) of Urban Sites Exceeding Expected Number of Days with an 8-Hour Daily Maximum Average > .06 ppm for Four 1-Hour Daily 

A-5 

Maximum Standards. . . . • . . • . . . . . . . . . . . • . . . . . . . . . . . . A-14 

Proportion (In Percent) .of Urban Areas Exceeding Expected Number of Days with an 8-Hour Daily Maximum Average > .10 ppm for Three 1-Hour 

Daily Maximum standards ......•......•............ A-15 

A-6 Generalized Relationships of the Current ozone 

NAAQS and Three Alternative 8-Hour Averages ...... A-19 

A-7 Cumulative Frequency Distribution of Three Peak 

Air Quality Indicators ........... ~~ ........... ~ .. A-28 

A-8 Correlations Among Short-Term, Multiple-Peak, and Longer-Term Air Quality Indicators in NonUrban Areas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-3 o 

A-9 Proportion (In Percent) of Rural/Remote Sites 

Exceeding Specified Expected Number of 8-Hour 

Daily Maximum Averages > .08 ppm for Three 1-Hour 

A-10 

A-ll 

A-12 

Daily Maximum Standards .......................... A-31 

Proportion (In Percent) of Rural/Remote Sites 

Exceeding Specified Maximum Monthly 1-Hour Daily Maximum Values for Three 1-Hour Daily Maximum 

N'AA.QS. . . . . . . . . . . . . . . . . . . . • . . • . . • . . . . . . . . . . . • . . . . . A-3 2 

Proportion (In Percent) of Rural/Remote Sites 

Exceeding Specified Three Month 8-Hour Averages 

Daily Maximum Three Month 8-Hour Averages For 

Three 1-Hour Daily Maximum NAAQS ................. A-33 

Proportion (In Percent) of Rural/Remote Sites 

Exceeding Specified Second High 1-Hour Daily 

Maximum Values for Three 8-Hour Daily Maximum 

Averages> .08 ppm Standards ..................... A-34 

.. 
A-13 

xvii 

Proportion (In Percent) of Rural/Remote Sites 

Exceeding Specified Number of Second High 1-Hour 

Daily Maximum Values for Three Maximum Monthly Mean 

1-Hour Daily Maximum Standards •.•.•••...••....... A-35 
Table 

V-1 

V-2 

V-3 

VI-1 

VI-2 

VII-1 

VII-2 

VII-3 

VII-4 

VII-5 

IX-1 

X-1 

xviii 

List of Tables 

Title 

Study Areas Modeled in Ozone-National Exposure 

Model ............................................ V-5 

Estimate of the Cumulative Number of Heavy 

Exercisers in the 8-Area Aggregation Population 

Exposed to One-Hour Average ozone Concentration 

During the ozone Season at Heavy Exercise Under 

Alternative Air Quality Scenarios ....•........... V-12 

Estimate of the Cumulative Number of PersonOccurrences of Heavy Exercise in the 8-Area 

Aggregation Population Exposed to One-Hour Average 

ozone During the ozone Season at Very Heavy 

Exercise Under Alternative Air Quality 

Scenarios ......................... ~· ............. V-14 

Estimated Values of Oxygen Consumption and 

Minute Ventilation Associated with Representative 

Types of Exercise ................................ VI-10 

Prevalence of Chronic Respiratory Conditions by 

Sex and Age for 1979 · .......•................... VI-12 

Key Human Studies Near the Current 1-Hour National 

Ambient Air Quality Standard for Ozone ........... VII-7 

Morphological Effects of Ozone in Experimental 

Animals .......................................... VII-29 

Effects of ozone on Host Defense Mechanisms 

in Experimental Animals .......................... VII-34 

Percent of Heavy Exercisers Responding Under 

Alternative Air Quality Scenarios ................ VII-49 

Gradation of Response for Healthy Individuals 

Acutely Exposed to Ozone ......................... VII-55 

Effect of Ozone on Photosynthesis ................ IX-4 

Ozone Concentrations for Short-term Exposure that 

Produce 5 or 20 Percent Injury to Vegetation 

Growth Under Sensitive Conditions .......•........ X-4 
xix 

LIST OF TABLES (continued) 

Table Title 

X-2 Summary of Ozone Concentrations Predicted to 

Caus.e 10 Percent and 3 0 Percent Yield Losses 

and Summary of Yield Losses Predicted to Occur 

at 7-hour Seasonal Mean -Ozone Concentrations of 

X-3 

0 . o 4 and o . o 6 ppm . . . . . . . . . • . . • . • . . • . . . . . . . . . . . . . . X -11 

Ozone Concentrations at Which Significant Yield 

Losses Have Been Noted for a Variety of Plant 

Species Exposed Under Various Experimental Conditions ....................................... X-15 

X-4 Effects of Ambient Air in Open-Top Chambers, Outdoor CSTR Chambers, or Growth and Yield of 

Selected Crops. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X-17 

X-5 Effects of Ozone on Crop Yield as Determined 

by the Use of Chemical Protectants ............... X-19 

< 

X-6 Continuum of Characteristic Ecosystem Responses to Pollutant Stress .................... X-28 

X-7 Effects of Ozone Added to Filtered Air on the 

Yield of Selected Tree Crops ..................... X-34 

X-8 Potential Ambient ozone Standards that would 

Limit Soybean Crop Reduction to 5, 10, 15, or 

2 0 Percent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X-52 

·X-9 Percentiles and Mean Predicted Relative Yield 

Losses Associated with Various Levels of the Four 

Exposure Indices, HDM2, M7, SUM06, and SUM07, for 

X-10 

X-11 

XI-1 

the 16 NCLAN Cases. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X-59 

Exposure Levels Associated with Predicted 

Relative Yield Losses of 5 to 30% for the Four 

Exposure Indices, HDM2, M7, SUM06, and SUM07, for the 16 NCLAN Studies ........•.....•...... ... X-60 

Forest Response Experts. . . . . . . . . . . . . . . . . . . . . . . . . . X -71 

u.s. Agricultural Welfare Benefits from Reducing Rural Ambient Ozone (7-hr seasonal means) to 60, 45, and 30 ppb for Three Alternative Benefit 

Measures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XI -14 

A-1 Cumulative Frequency Descriptive Statistics 

Associated with Peak and Multiple-Hour Ozone 

Air Quality Indicators in Urban Areas ............ A-5 

A-2 Cumulative Frequency Descriptive Statistics 

Associated w{th Various 8-Hour Ozone 

Air Quality Indicators in Urban Areas ............ A-7 
Table 

A- 3 

XX 

LIST OF TABLES (continued) 

Title Page 

Cumulative Frequency Descriptive Statistics Associated with Longer-Term Ozone Air Quality Indicators in Urban Areas .•..•.•.......•......... A-9 

A-4 Percent of Day~ Exceeding the .Current Ozone NAAQS and 3 Alternative 8-Hour Average Daily Maximum 

"CutPoints" ...................................... A-21 

A-5 Estimated Frequency of Daily Ozone Episodes by Length of the Episodes ......••................... A-22 

A-6 Descriptive cumulative Frequency Statistics Associated with Peak Ozone Air Quality Indicators . ... • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-25 

A-7 Descriptive Cumulative Frequency Statistics Associated with Longer-Term Air Quality Indicators (in ppm) ......................................... A-27 

• 
xxi 

Executive Summary 

This revised staff paper evaluates and interprets the 

available scientific and technical information that the EPA staff 

believe is most relevant to the review of primary (health) and 

secondary (welfare) national ambient air quality standards 

(NAAQS) for ozone (03) and presents staff recommendations on 

alternative approaches to revising the standards. Periodic 

review of the NAAQS is a process instituted to ensure the 

scientific adequacy of air quality standards and is required by 

• section 109 of the 1977 Clean Air Act Amendments. The assessment 

in this staff paper is intended to help build a bridge between 

the scientific review contained in the EPA 0 3 criteria document 

(hereafter referred to as CD) (U.S. EPA, 1986), apd the CD 

Supplement (hereafter referred to a~ CDS) (U.S. EPA, 1988) 

prepared by the Environmental Criteria and Assessment Office 

(ECAO) and the judgments req~ired of the Administrator in setting 

ambient standards for 0 3 • Therefore, the staff paper is an 

important element in the standards review process and provides an 

opportunity for review by the Clean Air Scientific Advisory 

Committee (CASAC) and the general public on proposed staff 

recommendations before they are presented to the Administrator. 

This staff paper has been revised based upon comments received 

from CASAC and the public and upon staff analyses which are 

available for public review. 
xxii 

Ozone is a trace constituent formed in the atmosphere as a 

result of a series of complex chemical reactions involving both 

anthropogenic and natural hydrocarbons and nitrogen oxides, 

oxygen and sunlight. At ambient concentrations often measured 

during warmer months, o3 can adversely affect human health, 

agricultural crops, forests, ecosystems, and materials. 

Interactions of 0 3 with nitrogen oxides and sulfur oxides may 

also contribute to the formation of acidic vapors and aerosols 

which might have direct effects on human health and welfare, as 

well as indirect effects following their deposition on surfaces. 

It should be noted that new evidence indicates that co-exposure 

to acidic aerosols can potentiate response to 0 3 • 

Annual average background surface 0 3 concentrations in the 

northern hemisphere generally range betw~en 0.03 and 0.05 ppm but 

are as low as 0.015 to o.o~o ppm in the tropics (U.S. EPA, 19861 

p. 3-80). Stratospheric intrusion is recognized as causing 

locally high o3 levels for periods lasting from minutes to hours, 

but these intrusions are usually worse in spring, fall, and 

winter. In contrast, during the photochemically active summer 

months intrusion is less common and less severe. Summertime 

hourly 0 3 levels have recently been reported to be as high as 

0.35 ppm in one of the nation's most heavily populated 

metropolitan areas. Daily daylight seasonal averages of o3 in 

some rural areas have been reported to be 0.06 ppm and higher. 
xxiii 

Primary Standard 

The staff reviewed scientific and technical information on 

the known and potential health effects of o3 cited in the CD and 

the CDS. The information includes studies of respiratory tract 

absorption and deposition of 0 3 , studies of mechanisms of o3 

toxicity, and controlled human exposure, field, epidemiological 

and animal toxicology studies of effects of exposure to o3 as 

well as air quality information. On the basis of this review, 

the staff derives the following conclusions. 

1) Inhaled 0 3 may pose health risks as a result of (a) 

penetration of 0 3 into various regions of the 

respiratory tract and absorption of 0 3 in this tract 

(b) provocation of pulmonary response resulting from 

chemica~ interactions of o3 along the respiratory 

• • tract, and (c) extrapulmonary effects caused indirectly 

by reaction of 0 3 in the lungs. 

2) The risks of adverse effects associated with absorption 

of 0 3 in the tracheobronchial and alveolar regions of 

the respiratory tract are much greater than for 

absorption in the extrathoracic region (head). 

Increased exercise levels are generally associated with 

higher ventilation rates and increased oronasal or oral 

(mouth) breathing. Greater 0 3 penetration and exposure 

of sensitive lung tissue occurs when individuals are 

heavily exercising. 
xxiv 

3) Factors which have been demonstrated to affect 

susceptibility to 03 exposure are activity level and 

environmental stress (e.g., humidity, high 

temperature). Those factors which either have not been 

adequately tested or remain uncertain include age, sex, 

preexisting disease, nutrition, and smoking status. 

4) Major subgroups of the population that may be at 

greater risk to the effects of o3 include: (a) any 

individual exercising heavily during exposure to o3 , 

particularly those who are otherwise healthy 

individuals who may experience significantly greater 

than group mean lung function response to 0 3 exposure, 

and (b) individuals with preexisting respiratory 

disease (e.g., asthmatics and persons with allergies). 

~ 

The data base identifying exercising individuals as 

being at greater risk to 0 3 exposure is much stronger 

and more quantitative than that for individuals with 

preexisting respiratory disease. This is due to the 

large number of clinical studies investigating effects 

of 0 3 on exercising persons. 

5) The major effects categories of concern associated with 

exposures to 0 3 include: 

(a) alterations in pulmonary function 

(b) symptomatic effects (e.g., cough, throat 

irritation) 

(c) effects on work or athletic performance 
XXV 

(d) aggravation of preexisting respiratory disease . 

(e) morphological effects (lung.structure damage) 

(f) altered host defense systems (e.g., increased 

susceptibility to respiratory infection) 

(g) extrapulmonary effects (e.g., effects on blood 

enzymes, central nervous system, liver, endocrine 

system). 

6) An important source of applicable exposure-response 

information for a short-term standard is controlled 

human exposure and field studies, which provide 

concentration-response relationships between 

alterations in pulmonary function and o3 exposure 

concentrations. Other important sources of information 

for ~tandard setting are epidemiological and 

toxicological studies. Epidemiology has provided 

associations between ambient o.

3 exposures and lung 

function decrements and aggravation of existing 

respiratory disease, but with greater uncertainties 

about the exposures involved than with controlled human 

exposure and field studies. Animal toxicology data 

provide acute and chronic exposure effects information 

on incre~sed susceptibility to respiratory infection, 

lung structure damage, and extrapulmonary effects. 

Although human exposure, epidemiology, and animal 

toxicology studies all have limitations in assessing 

adverse effects and risk, it is the weight of evidence 
xxvi 

and integration of findings from all three disc~plines which 

should be used in assessing health effects associated with 

exposure to o 3 • 

Based on scientific and technical reviews, CASAC comments, 

and policy considerations, the staff makes the following 

recommendations with respect to primary 0 3 standards: 

1) ozone should remain as the surrogate for controlling 

ambient concentrations of photochemical oxidants. 

2) The existing form of the standard should be retained 

(i.e., that the NAAQS is attained when the expected 

number of days per calendar year with maximum 1-hour 

average concentrations above the level of the standard 

is equal to or less than one) . 

3) The 1-hr averaging time of the standard should be 

retained. 

4) The range of 1-hour average o 3 levels of concern for 

standard-setting purposes is 0.08 to 0.12 ppm in 

concordance with CASAC comments (CASAC, 1986, 1987, 

1988) comments. This range is based solely on 1-2 hour 

exposure data. 

5) Because. there is a good health effects data base 

· available on 1-2 hour exposures, the staff concurs with 

the CASAC conclusion (McClellan, ~989) that review of 

the scientific basis for the 1-hr 0 3 primary standard 

be closed out. With this portion of the review 

complete, and after considering CASAC's views on all 
xxvii 

issues, the Administrator will be in a position to make 

a regulatory decision on how and when to best act on 

the 1-hour standard. 

6} In response to suggestions made by CASAC (1986, 1987, 

1988}, staff investigated the potential need and basis 

for a longer-term (6-8 hour) primary standard. 

Although an emerging data base reporting significant 

lung function decrements and symptoms in subjects 

exposed to 0 3 for 6 to 8 hours has provided some 

evidence of effects below 0.12 ppm 0 3 , staff concurs 

with CASAC's conclusion that "· .. such information 

can better be considered in the next review of the 

ozone standards." (McClellan, 1989}. It is recommended 

that EPA continue review of scientific information on 

health effects of prolonged exposure to o3 • Once these 

studies have been more completely evaluated during the 

next CD review, the Administrator will be able to 

assess the need for development of a longer-term 0 3 

primary standard. 

7) Further review and analysis also will be necessary 

before fully assessing the need for a separate standard 

to protect against chronic effects of 0 3 • Data on 

nasopharyngeal removal, dosimetry modeling and health 

effects based on and chronic exposure of animals will 

be used for future animal extrapolation and risk 

assessment of chronic 0 3 exposures. 
xxviii 

Secondary Standard 

The staff has reviewed the scientific and technical 

information on the known and potential welfare effects of o3 

cited in the CD and the CDS. This information includes impacts 

on vegetation, natural ecosystems, materials, and symptomatic 

effects on humans. Based on this review, the staff derives the 

following conclusions: 

1} The mechanisms by which 0 3 may injure plants a·nd plant 

communities include (a} absorption of 0 3 into leaf 

through stomata, followed by diffusion through the cell 

wall and membrane, (b) alteration of cell structure and 

function as well as critical plant processes, resulting 

from the chemical interaction of 0 3 with cellular 

components, and (c) occurrence of secondary effects 

including reduced photosynthesis and growth and yield 

and altered carbon allocation. 

2} The magnitude of the o3-induced effects depen~s upon 

the physical and chemical environment of the plant, as 

well as on various biological factors (including 

genetic potential, developmental age of plant, and 

interaction with plant pests} . 

3} The weight of the recent evidence seems to suggest that 

long-term averages, such as the 7-hour seasonal mean, 

may not be adequate indicators for relating o3 exposure 

and plant response. 
xxix 

4) Repeated peak concentrations are the most critical 

element in determining plant response. Exposure 

indicators which emphasize peak concentrations and 

accumulate concentrations over time probably provide 

the best biological basis for standard setting (See 

staff paper, p. X-50). 

5) There is currently a lack of exposure-response 

information on forest tree effects. In addition, there 

is a broad range of uncertainty among scientists 

regarding o3 effects on forest trees. Consequently 

there is no consensus on the most important averaging 

time for perennials or on the precise role of 0 3 vs. 

other pollutants in causing forest decline. Therefore, 

the staff concludes that a separate secondary standa:r:d 

based on protection of forest trees is not warranted • at 

this time. 

6) There appears to be no threshold level below which 

materials damage will not occur; exposure of sensitive 

materials to any non-zero concentration of 0 3 

(including natural background levels) can produce 

effects if the exposure duration is sufficiently long. 

However, the slight acceleration of aging processes of 
XXX 

materials which occurs at the level of the NAAQS is not 

judged to be significant or adverse. Consequently, the 

staff concludes that materials data should not be used 

as a basis for adequately defining an averaging time or 

concentration level for the secondary standard and that 

the secondary standard should be based on protection of 

vegetation. 

7) Effects on personal comfort and well-being, as defined 

by human symptomatic effects, have been observed in 

clinical studies at 03 levels in the range of 0.12-0.16 

for 1-2 hour exposures and at somewhat lower levels in 

extended exposure clinical and epidemiological studies. 

CASAC recommended that these effects be considered 

health effects in developing a basis for the _primary 

standard for 0 3 • -

Based on scientific and technical reviews, CASAC comments, 

and policy considerations, the staff makes the following 

recommendations with respect to secondary standards: 

1) In consideration of the large base of welfare 

information attributing effects to 0 3 exposure and the 

limited evidence which demonstrates welfare effects 

from exposure to ambient levels of non-0 3 photochemical 

-oxidants, there appears to be little evidence to 

suggest a change in chemical designation from 0 3 to 

photochemical oxidants. 
xxxi 

2) Given the lack of effects data on forests and the 

preliminary nature of the Lee et al. (1988c) results 

regarding selection of the appropriate exposure 

statistic for crops, the EPA staff concludes that it 

may be premature at this point in time to change the 

form of the standard and the averaging time. It is our 

judgment that a 1-hr averaging time standard in the 

range of 0.06-0.12 ppm represents the best staff 

recommendation that could be made to the Administrator 

at this time to close out the review of the scretltific 

data. This is consistent with CASAC comments (CASAC, 

1987, 1988) urging EPA to consider a 1-hr averaging 

time and to act on the existing state of scie11ce rather 

than extend the review until a more exhaustive 

\ 

assessment is made of alternative averaging times. 

With this portion of the review complete, and after 

considering CASAC's .views on all issues, the 

Administrator will be in a position to make a 

regulatory decision on how and when to best act on the 

1-hr standard. 

Alternatively, EPA could continue the standard review until 

the information on alternative exposure indicators has matured. 

Additional time for review and revision of Lee et al. ·(1988c) 

would allow the scientific community the opportun.ity to review 

the alternative indicators and move toward a consensus regarding 

selection of the most appropriate exposure indicator. The 
xxxii 

lia~ility of this alternative is that it postpones action on the 

secondary standard and thus fails to utilize new and existing 

information to· assess the most appropriate exposure statistic or 

the protection afforded by the current 1-hr standard. 

~ . 

,• 

\ 
x- 1 

X. Assessment of Welfare Effects and Related Welfare Issues 

Considered in Selecting Secondary standard(s) for ozone 

Of the phytotoxic compounds commonly found in the ambient 

air, 0 3 is the most prevalent, impairing crop production and 

injuring native vegetation and ecosystems more than any other air 

pollutant (Heck et al., 1980). Some of the effects of o 3 

reported in the literature occur at 0 3 levels at or below natural 

background concentrations in many areas of the country (see 

Section IV. for further discussion of background values). Ozone 

has also been shown to damage elastomers, textile fibers and dyes 

and certain types of paints. Other photochemical oxidants of 

importance to effects on vegetation, ecosystems and materials are 

nitrogen dioxide (N02 ) and peroxyacetyl nitrates. Air Quality 

Criteria for oxides of Nitrogen (U.S. EPA, 1982) and Review of 

the NAAQS for NOI: Assessment of Scientific and Technical 

Information (U.S. EPA, 1984) previously assessed the phytoxicity 

of N021 and thus N02 will not be discussed in this staff paper. 

In addition, while at a given dose the peroxyacetyl nitrates ~re 

more phytotoxic than 0 3 (p. X-22), they generally occur at 

significantly lower ambien~ concentrations. Because phytotoxic 

concentrations of peroxyacetyl nitrates are less widely 

distributed than those of 0 3 (CD, p. 6-1), the focus of this 

staff paper will be on the effects of 0 3 • 

The objective of this section of the staff paper is to 

assess the current basis for the 63 secondary NAAQS as contained 

in Chapters 6, 7 and 8 of the CD. In addition, the section will 

summarize new analyses that address key issu~s of concern for the 

secondary standard: relationships of various air quality 

indicators, crop loss estimates, averaging times and forest 

response to 0 3 . ·Key new studies that relate to the issue of 

averaging time(s) will also be discussed to determine whether new 

effects information suggests any change in existing secoDdary 

NAAQS for 0 3 •