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6.6-Hour Inhalation of Ozone Concentrations from 60 to 87 Parts per Billion in Healthy Humans

¹ 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

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject The acute inhalation of ambient concentrations of ozone induces several health effects including airway irritation and inflammation, decrements in pulmonary function, and symptoms of respiratory discomfort. What This Study Adds to the Field This study identifies 70 ppb as the mean concentration of ozone averaged over 6.6 hours that results in a statistically significant decrement in FEV1 and presents an empirically validated model that predicts the onset of pulmonary responses induced by any combination of ozone concentration, minute ventilation, and exposure duration.

 

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				J. S. Brown Acute Effects of Exposure to Ozone in Humans: How Low Can Levels Be and Still Produce Effects? Am. J. Respir. Crit. Care Med., August 1, 2009; 180(3): 200 - 201. [Full Text] [PDF]