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 03 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. 27711iii 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 CollegeBrunswick, Maine 04011Dr. Jay s. Jacobson Plant Physiologist Boyce Thompson Institute Tower RoadIthaca, New York 14853 Dr. Jane Q. Koenig Research Associate Professor Department of Environmental Health SC-34 University of Washington Seattle, Washington 98195 Dr. Timothy LarsonEnvironmental Engineering and Science ProgramDepartment 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 80306Dr. 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 TaylorEnvironmental 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 ·48090vi 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 20460vii 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 27711viii 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 27711Dr .. Dave T. TingeyEnvir9nmental Research Laboratory--Corvallis/ORO 200 S.W. 35th Street **~orvallis,** OR 97333 ixX 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-8xi 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-35xii 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-6xiii 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-40xiv 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 ReferencesVII-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 3xvi 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- 3o 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-35Table 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-4xix LIST OF TABLES (continued) Table Title X-2 Summary of Ozone Concentrations Predicted to Caus .e 10 Percent and 30 Percent Yield Losses

and Summary of Yield Losses Predicted to Occur

at 7-hour Seasonal Mean - Ozone Concentrations of X-3 0.o4 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 20 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-7TableA-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 •xxiExecutive 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 (0 3) 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 03 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 03• 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 03 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 03• Annual average background surface 03 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 o 3 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 03, 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 03 may pose health risks as a result of (a) penetration of 03 into various regions of the respiratory tract and absorption of 03 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 03 in the lungs. 2) The risks of adverse effects associated with absorption of 03 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 03 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 03 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 performanceXXV (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 evidencexxvi and integration of findings from all three **disc~plines** which should be used in assessing health effects associated with exposure to o3• Based on scientific and technical reviews, CASAC comments, and policy considerations, the staff makes the following recommendations with respect to primary 03 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 03 primary standard

be closed out. With this portion of the review complete, and after considering CASAC's views on allxxvii 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 03 for 6 to 8 hours has provided some evidence of effects below 0.12 ppm 03, 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 03 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 03• 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 03 exposures.xxviii Secondary Standard

The staff has reviewed the scientific and technical information on the known and potential welfare effects of o 3 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 03 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 03 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 03 (including natural background levels) can produce effects if the exposure duration is sufficiently long. However, the slight acceleration of aging processes ofXXX 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 03• 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 03 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 03 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. Thexxxii **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. AssessmentofWelfareEffectsandRelatedWelfareIssues ConsideredinSelectingSecondarystandard(s)forozone Ofthephytotoxiccompoundscommonlyfoundintheambient air,03isthemostprevalent,impairingcropproductionand injuringnativevegetationandecosystemsmorethananyotherair pollutant(Hecketal.,1980). 

### Someoftheeffectsofo3 

### reportedintheliteratureoccurat03levelsatorbelownatural backgroundconcentrationsinmanyareasofthecountry(see SectionIV.forfurtherdiscussionofbackgroundvalues). Ozone hasalsobeenshowntodamageelastomers,textilefibersanddyes andcertaintypesofpaints. Otherphotochemicaloxidantsof importanceto effectsonvegetation,ecosystemsandmaterialsare nitrogendioxide(N02)

### andperoxyacetylnitrates. AirQuality CriteriaforoxidesofNitrogen(U.S.EPA,1982)

### andReviewof theNAAQSforNOI: AssessmentofScientificandTechnical Information(U.S.EPA,1984)

### previouslyassessedthephytoxicity ofN021

### andthusN02

### willnotbediscussedinthisstaffpaper. Inaddition,whileatagivendosetheperoxyacetylnitrates**~re** 

### morephytotoxicthan03

### (p.X-22),

### theygenerallyoccurat significantlylower**ambien~**

### concentrations. Becausephytotoxic concentrationsofperoxyacetylnitratesarelesswidely distributedthanthoseof03(CD,p.6-1),thefocusofthis staffpaperwillbeontheeffectsof03• 

### Theobjectiveofthissectionofthestaffpaperisto assessthecurrentbasisforthe

### 63

### secondaryNAAQSascontained inChapters6,7and8oftheCD. Inaddition,thesectionwill summarizenewanalysesthataddresskey**issu~s**

### ofconcernforthe secondarystandard: relationshipsofvariousairquality indicators,croplossestimates,averagingtimesandforest responseto03.·Keynewstudiesthatrelatetotheissueof averagingtime(s)willalsobediscussedtodeterminewhethernew effectsinformationsuggestsanychangeinexistingsecoDdary NAAQSfor03•