Asthma, rhinitis and air pollution: is traffic to blame?

# 12 This issue of the European Respiratory Journal contains two papers that contribute to a growing body of evidence incriminating traffic fumes in respiratory disease. NICOLAI et al. [1] report a cross-sectional study that finds significant associations between traffic counts and exposure to traffic-related air pollution on the one hand and current asthma, wheeze and cough on the other. In a subgroup of children exposed to environmental tobacco smoke, traffic counts are also related to allergic sensitisation. LEE et al. [2] report a large questionnaire survey from Taiwan, in which a composite measure of exposure to traffic-related air pollution is found to be associated with physician-diagnosed allergic rhinitis. A parallel analysis reported previously [3] found a similar association between traffic-related air pollution and physician-diagnosed as well as questionnaire-reported asthma. How do these studies relate to earlier work on air pollution and childhood respiratory illness? How do they relate to earlier work on traffic-related pollution? Large-scale, cross-sectional studies on air pollution and respiratory outcomes in children have been reported from the USA [4], Switzerland [5], Canada [6] and Austria [7]. The US and Swiss studies found associations between some air pollutants (especially fine particles) and cough and bronchitis symptoms, the Canadian study found no relationships and the Austrian study documented associations between nitrogen dioxide (NO 2 ; described as a marker for traffic-related air pollution) and asthma, wheeze and cough. East/West comparisons have generally highlighted high bronchitis and cough prevalence in the East, which were ascribed to "classical" pollution, consisting of sulphur dioxide (SO 2) and particles [8], with higher rhinitis in the West. A recent study from California, USA, found an association between wheeze prevalence and the air pollution components, acid and NO 2. Taken together, these findings suggest that society is witnessing a transition from classical pollution, dominated by SO 2 and particles generated by coal and oil combustion, with the effects primarily on cough and bronchitis, to pollution mixtures dominated by traffic exhausts represented by NO 2 , with effects on wheeze and perhaps asthma prevalence. It is important to look at what precisely is the definition of asthma in some of these studies. The paper by NICOLAI et al. [1] defines asthma as a report by parents that a doctor has diagnosed asthma at least once or that a doctor has diagnosed asthmatic, spastic or obstructive bronchitis more than once. This definition therefore includes, to some …