Residential exposure to outdoor air pollution and adult lung function, with focus on small airway obstruction

Although a growing body of evidence suggests that chronic exposure to outdoor air pollution is linked to a decline in lung function, data on flow at low lung volumes that may be more specific of small airway obstruction are still scarce. We aimed to study the associations between residential exposure to air pollution and lung function, with specific focus on small airways obstruction. We assessed 2995 French participants (aged between 40 and 65) in the ELISABET cross-sectional survey. Residential exposures to nitrogen dioxide (NO2), particulate matter with a diameter < 10 mu m (PM10) and sulphur dioxide (SO2) were assessed. The spirometric parameters were forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and forced expiratory flow between 25% and 75% of FVC (FEF25-75) and at 75% of FVC (FEF75). Coefficients in linear regression models were expressed as the z-score [95% confidence interval] for an increment of 5 mu g/m(3) in NO2 and 2 mu g/m(3) in PM10 and SO2. NO2 was associated with significantly lower values of FEV1 (-0.10 [-0.15;-0.05]), FVC (-0.06 [-0.11;0.02]), FEV1/FVC (-0.07 [-0.11;-0.03]), FEF25-75 (-0.09 [-0.14;-0.05]) and FEF75 (-0.08 [-0.12;-0.04]). PM10 was associated with significantly lower values of FEV1 (-0.10 [-0.15;-0.04]), FVC (-0.06 [-0.11;-0.01]), FEV1/FVC (-0.06 [-0.11;-0.01]), FEF25-75 (-0.08 [-0.13;-0.03]) and FEF75 (-0.08 [-0.12;-0.04]). SO2 was associated with significantly lower values of FEV1 (-0.09 [-0.16;-0.02]), FEV1/FVC (-0.07 [-0.13;-0.01]), FEF25-75 (-0.09 [-0.15;-0.02]) and FEF75 (-0.08 [-0.14;-0.03]) but not FVC (-0.05 [-0.11; 0.009]). Even though spatial variations in pollutant levels were low, residential exposure to outdoor air pollution was associated with lower lung function, including lower FEF25-75 and FEF75 suggesting small airway obstruction.