Occupational exposure to inhalative irritants and methacholine responsiveness

Objectives Occupational exposures to inhalative irritants have been associa ted with an increased reporting of respiratory symptoms in previous studies . Methacholine responsiveness represents a continuous measure of airway res ponsiveness. As such, it may be less subject to recall bias and more sensit ive to detecting effects of occupational exposure on airways. Such effects may be stronger among atopic persons. The objective of the study was to exa mine the relationship between self-reports of occupational exposure to dust s, gases, vapors, aerosols, and fumes and methacholine responsiveness. Methods A sample was studied of never smokers (N=3044) chosen randomly from 8 areas in Switzerland. Atopy was defined as any positive skin test to 8 i nhalative allergens. Nonspecific bronchial reactivity was tested using meth acholine chloride and quantified by calculating the slope of the dose-respo nse. Results The methacholine slopes were 19% [95% confidence interval(95% CT) 6 -32] higher for never smokers with exposure to dusts, fumes, vapors, gases, or aerosols than for the unexposed group. When only atopic never smokers w ere examined, the increase was larger (37%, 95% CI 7-75), and for persons w ith greater than or equal to 2 positive skin prick tests the effect was sti ll higher (42%, 95% CI -1.5-104). Exposure to vapors and aerosols was stron gly associated with increased methacholine slopes among the atopic subjects . Conclusions occupational exposure, particularly to dusts and fumes, was ass ociated with increased bronchial reactivity in never smokers in this study. The magnitude of the effect was larger among atopic subjects.