Long-term ambient air pollution and respiratory symptoms in adults (SAPALDIA Study)

The association between long-term exposure to ambient air pollution and res piratory symptoms was investigated in a cross-sectional study in random pop ulation samples of adults (aged 18 to 60 yr, n = 9,651) at eight study site s in Switzerland. Information on respiratory symptoms was obtained with an extended version of the European Community Respiratory Health Survey questi onnaire. The impact of annual mean concentrations of air pollutants was ana lyzed separately for never-, former, and current smokers. After controlling for age, body mass index, gender, parental asthma, parental atopy, low edu cation, and foreign citizenship, we found positive associations between ann ual mean concentrations of NO,, total suspended particulates, and particula tes of less than 10 mu m in aerodynamic diameter (PM10) and reported preval ences of chronic phlegm production, chronic cough or phlegm production, bre athlessness at rest during the day, breathlessness during the day or at nig ht, and dyspnea on exertion. We found no associations with wheezing without cold, current asthma, chest tightness, or chronic cough. Among never-smoke rs, the odds ratio (95% confidence interval) for a 10 mu g/m(3) increase in the annual mean concentration of PM10 was 1.35 (1.11 to 1.65) for chronic phlegm production, 1.27 (1.08 to 1.50) for chronic cough or phlegm producti on, 1.48 (1.23 to 1.78) for breathlessness during the day, 1.33 (1.14 to 1. 55) for breathlessness during the day or at night, and 1.32 (1.18 to 1.46) for dyspnea on exertion. No associations were found with annual mean concen trations of O-3. Similar associations were also found for former and curren t smokers, except for chronic phlegm production. The observed associations remained stable when further control was applied for environmental tobacco smoke exposure, past and current occupational exposures, atopy, and early c hildhood respiratory infections when restricting the analysis to long-term residents and to non-alpine areas, and when excluding subjects with physici an-diagnosed asthma. The high correlation between the pollutants makes it d ifficult to sort out the effect of one single pollutant. This study provide s further evidence that long-term exposure to air pollution of rather low l evels is associated with higher prevalences of respiratory symptoms in adul ts.