Urban Air Pollution and Children Respiratory Hospital Admissions in Pisa (italy) A Time Series and A Case-Crossover Approach

OBJECTIVES:we evaluated the association of daily pollutants' concentrations with daily hospital admissions for respiratory causes in children residents in Pisa during 1998-2002. We compared the results obtained with two methods of statistical analyses. A total of 657 children under ten years and admitted to local hospitals for respiratory diseases (ICD 9: 460-469, 480- 519) were included in the study.DESIGN:both time-series and case-crossover analysis were applied, controlling for temperature, holidays, influenza epidemics,rain and relative humidity. Pollutants' effects are expressed as percentage increase (and 95% CI) of hospital admissions for an increase of 10 μg/m³ of pollutants (1 mg/m³ for CO).RESULTS:with both analyses, children's hospital admissions for respiratory conditions were significantly associated to increasing daily levels of PM10 and CO at different time lags, while no association was found for NO₂ and O₃. In the case-crossover analysis, for a daily increase of 10 μg/m³ in PM10, a significant increment of 8.5% (CI 95% 0.02; 17.6) in children respiratory admissions was observed at lag 0-3. Results were stronger for males and during the warm season. A 1 mg/m³ increment in daily CO levels was associated with an increase of respiratory admissions at lag 0 (20.2%, CI 95% 5.3; 37.2) and at all cumulative lags: the maximum value was observed at lag 0-3 (32.6%, CI 95%8.3; 62.2). Time series analyses provides similar results, although the estimates were lower than with the other method, in terms of percentage increment and length of confidence intervals.CONCLUSIONS:this study indicates adverse effects of air pollution on respiratory health of children living in urban environment. The results of both analyses were consistent.