Exposure to outdoor
air pollutants and passive tobacco
smoke are common but avoidable worldwide risk factors for morbidity and mortality of individuals. In addition to well-known effects of
pollutants on the cardiovascular system and the development of
cancer, in recent years the association between air pollution and respiratory morbidity has become increasingly apparent. Not only in adults, but also in children with
asthma and in healthy children a clear harmful effect of exposure towards
air pollutants has been demonstrated in many studies. Among others increased pollution has been shown to result in more frequent and more severe respiratory symptoms, more frequent exacerbations, higher need for
asthma medication, poorer lung function and increased visits to the emergency department and more frequent hospitalisations. While these associations are well established, the available data on the role of air pollution in the development of
asthma seems less clear. Some studies have shown that increased exposure towards tobacco
smoke and air pollution leads to an increase in
asthma incidence and prevalence; others were not able to confirm those findings. Possible reasons for this discrepancy are different definitions of the outcome
asthma, different methods for exposure estimation and differences in the populations studied with differing underlying genetic backgrounds. Regardless of this inconsistency, several mechanisms have already been identified linking air pollution with
asthma development. Among these are impaired lung growth and development, immunological changes, genetic or epigenetic effects or increased predisposition for allergic sensitisation. What the exact interactions are and which asthmatic phenotypes will be influenced most by
pollutants will be shown by future studies. This knowledge will then be helpful in exploring possible preventive measures for the individual and to help policy makers in deciding upon most appropriate regulations on a population level.