Published ahead of print on May 15, 2009, doi:10.1164/rccm.200809-1484OC
© 2009 American Thoracic Society doi: 10.1164/rccm.200809-1484OC
6.6-Hour Inhalation of Ozone Concentrations from 60 to 87 Parts per Billion in Healthy Humans1 Department of Anatomy, Physiology, and Cell Biology, University of California Davis School of Veterinary Medicine, Davis; 2 California National Primate Research Center, University of California Davis, Davis; and 3 Department of Internal Medicine, University of California Davis Medical Center, Sacramento, California Correspondence and requests for reprints should be addressed to Edward S. Schelegle, Ph.D., Department of Anatomy, Physiology, and Cell Biology, University of California Davis, 1 Shields Avenue, Davis, CA 95616. E-mail: esschelegle{at}ucdavis.edu Rationale: Identification of the minimal ozone (O3) concentration and/or dose that induces measurable lung function decrements in humans is considered in the risk assessment leading to establishing an appropriate National Ambient Air Quality Standard for O3 that protects public health. Objectives: To identify and/or predict the minimal mean O3 concentration that produces a decrement in FEV1 and symptoms in healthy individuals completing 6.6-hour exposure protocols. Methods: Pulmonary function and subjective symptoms were measured in 31 healthy adults (18–25 yr, male and female, nonsmokers) who completed five 6.6-hour chamber exposures: filtered air and four variable hourly patterns with mean O3 concentrations of 60, 70, 80, and 87 parts per billion (ppb). Measurements and Main Results: Compared with filtered air, statistically significant decrements in FEV1 and increases in total subjective symptoms scores (P < 0.05) were measured after exposure to mean concentrations of 70, 80, and 87 ppb O3. The mean percent change in FEV1 (±standard error) at the end of each protocol was 0.80 ± 0.90, –2.72 ± 1.48, –5.34 ± 1.42, –7.02 ± 1.60, and –11.42 ± 2.20% for exposure to filtered air and 60, 70, 80, and 87 ppb O3, respectively. Conclusions: Inhalation of 70 ppb O3 for 6.6 hours, a concentration below the current 8-hour National Ambient Air Quality Standard of 75 ppb, is sufficient to induce statistically significant decrements in FEV1 in healthy young adults.
Key Words: ozone • clinical study • exposure assessment • human
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