Outdoor sulphur dioxide and respiratory symptoms in Czech and Polish school children: a small-area study (SAVIAH)

Objectives: Air pollution has been linked to respiratory outcomes but contr oversy persists about its long-term effects. We used a novel technique to e stimate the outdoor concentrations of sulphur dioxide (SO2) at small-area l evel to study the long-term effects on respiratory symptoms and disease in children. Methods: As part of the international SAVIAH study, parents of 8, 013 children aged 7-10 studied in Prague (Czech Republic) and Poznan (Polan d) completed a questionnaire covering respiratory health, demographic and s ocio-economic factors and health behaviours (response rate 91%). This repor t is based on 6,959 children with complete data. Outdoor SO2 was measured b y passive samplers at 80 sites in Poznan and 50 sites in Prague during 2-we ek campaigns. Concentrations Of SO2 at each point (location) in the study a reas were estimated from these data by modelling in a geographical informat ion system. The mean ofthe estimated SO2 concentrations at children's homes and schools was used as an indicator of exposure to outdoor SO2. Results: The prevalence of respiratory outcomes was similar in both cities. In the p ooled data, 12% of children had experienced wheezing/whistling in the past 12 months; 28% had a lifetime prevalence of wheezing/whistling; 14% had a d ry cough at night; and 3% had had asthma diagnosed by a doctor. The estimat ed mean exposure to outdoor SO, was 80 (range 44-140) mug/m(3) in Poznan an d 84 (66-97) mug/m(3) in Prague. After socio-economic characteristics and o ther covariates were controlled for, SO2 was associated with wheezing/whist ling in the past 12 months (adjusted OR per 50 mug/m(3) 1.32, 95% Cl 1.10-1 .57), lifetime prevalence of wheezing/whistling (OR 1.13, 95% CI 0.99-1.30) , and lifetime prevalence of asthma diagnosed by a doctor (OR 1.39, 95% Cl 1.01-1.92). The association with dry cough at night did not reach statistic al significance. Conclusions: In these two Central European cities with rel atively high levels of air pollution, small-area based indicators of long-t erm outdoor winter concentrations Of SO2 were associated with wheezing / wh istling and with asthma diagnosed by a doctor.