Respiratory Responses to Ozone Exposure: The Multicenter Ozone Study in oldEr Subjects (MOSES).

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Abstract

RATIONALE

Acute respiratory effects of low-level ozone exposure are not well defined in older adults.

OBJECTIVE

The Multicenter Ozone Study in oldEr Subjects (MOSES), although primarily focused on acute cardiovascular effects, provided an opportunity to assess respiratory responses to low concentrations of ozone in older healthy adults.

METHODS

We performed a randomized crossover, controlled exposure study of 87 healthy adults (59.9±4.5 years old; 60% female) to 0, 70, and 120 ppb ozone for 3 hours with intermittent exercise. Outcome measures were spirometry, sputum markers of airway inflammation, and plasma club cell protein-16 (CC16), a marker of airway epithelial injury. The effects of ozone exposure on these outcomes were evaluated with mixed effect linear models. A p-value <0.01 was chosen a priori to define statistical significance.

MAIN RESULTS

The mean (95% CI) FEV1 and FVC increased from pre-exposure values by 2.7% (2.0, 3.4) and 2.1% (1.3, 2.9), respectively, 15 min post-exposure to filtered air (0 ppb). Exposure to ozone reduced these increases in a concentration-dependent manner. After 120 ppb exposure, FEV1 and FVC decreased by 1.7% (1.1, 2.3) and 0.8% (0.3, 1.3), respectively. A similar concentration-dependent pattern was still discernible 22 h post-exposure. At 4 h post-exposure, plasma CC16 increased from pre-exposure levels in an ozone-concentration-dependent manner. Sputum neutrophils obtained 22 h post-exposure showed a marginally significant increase in a concentration-dependent manner (p=0.012), but pro-inflammatory cytokines (IL-6, IL-8, TNFα) were not significantly affected.

CONCLUSIONS

Exposure to ozone at near ambient levels induced lung function effects, airway injury, and airway inflammation in older healthy adults. Clinical trial registration available at www.clinicaltrials.gov, ID NCT01487005.

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