Irritant exposure, bronchial reactivity and asthma.

The role of irritant exposure in the pathogenesis of bronchial reactivity and asthma is uncertain. This paper reviews the evidence from environmental epidemiological surveys, studies of occupationally exposed populations and chamber studies of asthmatic and nonasthmatic subjects exposed to irritant fumes. The reactive airways dysfunction syndrome and occupational asthma due to irritant exposure are considered in the context of these results. Although several irritants cause acute bronchoconstriction by a number of mechanisms in chamber studies, there is little convincing evidence to suggest that irritant exposure without pulmonary injury is a risk factor for the development of bronchial hyperresponsiveness. This is the case both in relatively intense concentrations, such as those experienced in industrial or chamber exposure, and at the levels experienced by the general population.