Outdoor sulphur dioxide and respiratory symptoms in Czech and Polish school children: a small-area study (SAVIAH). Small-Area Variation in Air Pollution and Health.

OBJECTIVES: Air pollution has been linked to respiratory outcomes but controversy persists about its long-term effects. We used a novel technique to estimate the outdoor concentrations of sulphur dioxide (SO2) at small-area level 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 (Poland) completed a questionnaire covering respiratory health, demographic and socio-economic factors and health behaviours (response rate 91%). This report is based on 6,959 children with complete data. Outdoor SO2 was measured by passive samplers at 80 sites in Poznan and 50 sites in Prague during 2-week campaigns. Concentrations of SO2 at each point (location) in the study areas were estimated from these data by modelling in a geographical information system. The mean of the 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 pooled data, 12% of children had experienced wheezing/whistling in the past 12 months; 28% had a lifetime prevalence of wheezing/whistling; 14% had a dry cough at night; and 3% had had asthma diagnosed by a doctor. The estimated mean exposure to outdoor SO2 was 80 (range 44-140) microg/m3 in Poznan and 84 (66-97) microg/m3 in Prague. After socio-economic characteristics and other covariates were controlled for, SO2 was associated with wheezing/whistling in the past 12 months (adjusted OR per 50 microg/m3 1.32, 95% CI 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% CI 1.01-1.92). The association with dry cough at night did not reach statistical significance. CONCLUSIONS: In these two Central European cities with relatively high levels of air pollution, small-area based indicators of long-term outdoor winter concentrations of SO2 were associated with wheezing/whistling and with asthma diagnosed by a doctor.

Outdoor air concentrations of nitrogen dioxide and sulfur dioxide and prevalence of wheezing in school children.

We report analysis of data on outdoor air pollution and respiratory symptoms in children collected in the Czech part of the international Small Area Variations in Air pollution and Health (SAVIAH) Project, a methodological study designed to test the use of geographical information systems (GIS) in studies of environmental exposures and health at small area level. We collected the following data in two districts of Prague: (1) individual data on 3,680 children (response rate 88%) by questionnaires; (2) census-based socio-demographic data for small geographical units; (3) concentrations of nitrogen dioxide (NO2) and sulfur dioxide (SO2) measured by passive samplers in three 2-week surveys at 80 and 50 locations, respectively. We integrated all data into a geographical information system. Modeling of NO2 and SO2 allowed estimation of exposure to outdoor NO2 and SO2 at school and at home for each child. We examined the associations between air pollution and prevalence of wheezing or whistling in the chest in the last 12 months by logistic regression at individual level, weighted least squares regression at small area (ecological) level and multilevel modeling. The results varied by the level of analysis and method of exposure estimation. In multilevel analyses using individual data, odds ratios per 10 microg/m3 increase in concentrations were 1.16 (95% CI = 0.95-1.42) for NO2, and 1.08 (95% CI = 0.97-1.21) for SO2. While mapping of spatial distribution of NO2 and SO2 in the study area appeared valid, the interpolation from outdoor to personal exposures requires consideration.