ABSTRACT
It is becoming increasingly clear that environmental exposures are the most important precipitants of asthma exacerbations. Exposure to environmental tobacco smoke has a detrimental effect on asthma, leading to an increase in acute asthma exacerbations and lower pulmonary function in children (10). Exposure to smoke from fireplaces and wood-burning stoves has also been implicated as a possible cause of asthma exacerbations. However, the role of air pollution in cities is still unclear, since death rates have increased while concentrations of major pollutants have decreased (9). It may be that the indoor environment (cat, house dust mite, and cockroach antigen) is a more important precipitant in the inner city. Epidemics of severe asthma in cities have followed exposures to high concentrations of aeroallergens (11-13). Viral respiratory tract infections remain the single most significant precipitant of severe asthma in children (14,15).
