Prevalence of asthma and rhinitis in relation to long-term exposure to gaseous air pollutants

The relationship between long-term exposure to air pollutants, especially w ith regard to photochemical air pollutants, and asthma prevalence in develo ped countries is controversial. The objective of this cross-sectional surve y was to compare mean levels of the main gaseous air pollutants and prevale nce rates of rhinitis, asthma, and asthmatic symptoms. It included 2445 chi ldren from the 8th and 9th school grades who had been living for at least 3 years in an area where some communities undergo the heaviest photochemical exposure in France. Data on rhinitis, asthmatic symptoms, and asthma preva lence were gathered with the ISAAC paper and video questionnaires. The rela tion between level of air pollutants and asthma was assessed first by compa rison of crude prevalence rates (chi-square test), and then by simple regre ssion analysis and multiple logistic regression analysis. No consistent ass ociation between mean SO2 and NO2 levels and prevalence of rhinitis, asthma , or asthmatic symptoms could be demonstrated. In contrast, there were stat istically significant associations between prevalence of asthmatic symptoms and mean ozone (O-3) concentration. The interpretation of such findings is not straightforward, as these symptoms can be interpreted either as respir atory irritation due to exposure to nonspecific airway stimuli or as a true asthmatic state. Additional studies are required to clarify this important issue. In conclusion, this large cross-sectional epidemiologic survey perf ormed in an area of high photochemical air pollution did demonstrate statis tically significant associations between the prevalence of asthmatic sympto ms and mean O-3 concentration.