Do Ambient Ozone or Other Pollutants Modify Effects of Controlled Ozone Exposure on Pulmonary Function?

Area of Science:

• Environmental Health Sciences
• Pulmonary Medicine
• Cardiovascular Physiology

Background:

• Previous studies indicated controlled ozone (O3) exposure impacts lung function and airway inflammation.
• Potential confounding from prior exposure to indoor/outdoor air pollutants on O3 biomarker responses was noted.
• The MOSES trial previously showed O3 effects on lung function but not cardiovascular function.

Purpose of the Study:

• To investigate if personal or ambient air pollutant levels (NO2, O3, PM2.5, CO, SO2) modify biomarker responses to controlled O3 exposure.
• To assess the impact of pollutants in the 72-96 hours preceding controlled O3 exposure on cardiovascular and pulmonary outcomes.

Main Methods:

• Subjects underwent 3-hour controlled exposures to clean air, 70 ppb O3, or 120 ppb O3 with alternating exercise/rest.
• Biomarkers of autonomic function, repolarization, ST segment, arrhythmia, vascular status, inflammation, vascular function, pulmonary function, oxidative stress, and lung injury were measured.
• Mixed effects linear regression analyzed modification of O3 effects by tertiles of personal exposure samplers (PES) for O3/NO2 and ambient pollutant concentrations in the 96 hours prior.

Main Results:

• Controlled O3 exposure effects on forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) were significantly modified by ambient NO2, CO, and PES NO2.
• Reductions in FEV1 and FVC were observed only when preceding NO2 and CO concentrations were in the medium or high tertile (within 72 hours).
• No significant modification was found for other measured cardiopulmonary outcome groups.

Conclusions:

• Preceding ambient and personal nitrogen dioxide (NO2) and carbon monoxide (CO) pollution levels modify the impact of controlled ozone (O3) exposure on lung function.
• Reduced lung function (FEV1, FVC) from O3 exposure was evident only when NO2 and CO levels were elevated in the days prior.
• These findings highlight the importance of cumulative air pollution exposure in assessing O3 health effects.