Lung Function and Inflammation in Healthy Young Adults After 6.6 Hours of 0.07 ppm Ozone Exposure

Rationale: Exposure to ozone results in decreased lung function and increased airway inflammation in healthy young adults at concentrations between 0.06-0.07 ppm. The US Environmental Protection Agency is reconsidering whether the current ozone National Ambient Air Quality Standard (NAAQS) of 0.07 ppm is protective of human health. Objectives: To determine if decrements in pulmonary function and inflammatory changes are observed at the NAAQS for ground level ozone, which is currently set at 0.07 ppm. Methods: Pulmonary function and subjective symptom scores were measured in 38 healthy young adults (19–34 yr) immediately before and after exposure to 0.0 (clean air, CA) and 0.07 ppm ozone for 6.6 hours while undergoing intermittent moderate exercise. Polymorphonuclear neutrophil (PMN) influx into the respiratory tract was quantified in 14 subjects 16 to 18 hours post-exposure. Results: Participants experienced a significantly greater  change in FEV1 immediately after exposure to 0.07 ppm ozone compared with CA (-1.24 ± 0.92% vs. 0.83 ± 0.50%; p = 0.017). The decrement in FVC was also greater after ozone relative to CA (-1.22 ± 0.29% vs. -0.44 ± 0.40%), although changes were not statistically significant. Percent PMNs in sputum samples was greater after ozone relative to CA exposure (33.4 ± 6.9% vs.18.6 ± 5.6%; p = 0.013). Reported symptom scores were significantly elevated during hours 5.5 and 6.5 during exposure to ozone, relative to CA. The most commonly reported symptoms were headache, fatigue, throat irritation followed by shortness of breath, runny nose/nose irritation, and chest tightness.   Conclusions: Exposure of healthy young adults to 0.07 ppm ozone for 6.6 hours causes a significant decrement of FEV1 and increased neutrophilic pulmonary inflammation. Self-reported total symptom scores are significantly elevated during ozone exposure relative to CA.

Impact/Purpose

Potential health effects of ozone have been extensively studied over decades at various levels of exposure concentration and for varying time periods in young healthy adult subjects. Effects of ozone have been well documented particularly for decrements of lung function and an influx of neutrophils and other markers of pulmonary inflammation. The majority of those studies were done at ozone concentrations between 0.12 and 0.40 ppm, considerably higher than the current EPA NAAQS ozone standard of 0.070 ppm, and at exposure durations of two hours, even though the current standard is an 8-hour standard. However, a small number of studies have assessed changes in lung function following exposure to low levels of ozone for several hours. These studies have shown that exposure to ozone for 6.6 hours at concentrations between 0.06 and 0.08 ppm causes mild reversible decrements in lung function (1.7-10%)  and increased ozone-induced neutrophils in induced sputum and bronchoalveolar lavage fluid. The EPA is considering whether the current ozone NAAQS standard at 0.070 is protective and has asked EPA researchers to conduct a study similar to those done at 0.06 and 0.08 ppm.

Citation

Pennington, E., J. Pulczinski, M. Case, J. Griffin, N. Alexis, C. Robinette, A. Chelminski, A. Davis, N. Miller, A. Ghio, D. Diazsanchez, AND A. Rappold. Lung Function and Inflammation in Healthy Young Adults After 6.6 Hours of 0.07 ppm Ozone Exposure. American Thoracic Society, New York, NY124387, (2026). [DOI: 10.1016/j.envres.2026.124387]

DOI: Lung Function and Inflammation in Healthy Young Adults After 6.6 Hours of 0.07 ppm Ozone Exposure