Prevalence of asthma and mean levels of air pollution: results from the French PAARC survey

Among the possible explanations for the recent increase in the prevalence o f asthma in several countries, air pollution is one of the foremost public health concerns. Data from the "Pollution Atmospherique et Affections Respiratoires Chroniqu es" (PAARC) survey collected in 24 areas of seven French towns during 1974- 1976 were reanalysed to assess the relationship between the prevalence of a sthma and the following air pollutants: sulphur dioxide (specific (SO2) and acidimetric methods), total suspended particles (TSP), black smoke (BS), n itrogen dioxide and nitric oxide. Correlation coefficients between annual m ean levels of pollution and prevalence of asthma in the different areas wer e first calculated. Random-effects models were then estimated. Of the 20,310 adults aged 25-59 yrs, 1,291 (6.4%) were found to be asthmati cs as well as 195 (6.1%) of the 3,193 children aged 5-9 yrs. A geographical correlation between asthma and annual mean level of SO2 (ranging 17-85 mu g.m(-3)) was found (r=0.45, p=0.01) in adults. No relationship was found in children. After controlling for age, educational level, smoking, and geogr aphical clustering,vith a multivariate random-effects model, the relationsh ip remained significant in adults for 802 (odds ratio for a 50 mu g m(-3) i ncrease=1.24, confidence interval 1.08-1.44, p=0.0035). It also remained si gnificant when taking into account only the people reporting their last ast hma attack occurring after settling in the study area. These results are consistent with the known short-term effects of 802 in as thma and demonstrate the necessity for further studies on delayed effects o f air pollution in respiratory diseases.