Objectives Occupational exposures to inhalative irritants have been associated with an increased reporting of respiratory symptoms in previous studies. Methacholine responsiveness represents a continuous measure of airway responsiveness. As such, it may be less subject to recall bias and more sensitive to detecting effects of occupational exposure on airways. Such effects may be stronger among atopic persons. The objective of the study was to examine the relationship between self-reports of occupational exposure to dusts, 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 inhalative allergens. Nonspecific bronchial reactivity was tested using methacholine chloride and quantified by calculating the slope of the dose-response. Results The methacholine slopes were 19% [95% confidence interval (95% CI) 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 were examined, the increase was larger (37%, 95% CI 7-75), and for persons with 22 positive skin prick tests the effect was still higher (42%, 95% CI-1.5-104). Exposure to vapors and aerosols was strongly associated with increased methacholine slopes among the atopic subjects. Conclusions Occupational exposure, particularly to dusts and fumes, was associated with increased bronchial reactivity in never smokers in this study. The magnitude of the effect was larger among atopic subjects. Key terms allergy skin tests, bronchial hypesreactivity, human adults, methacholine challenge. Part of the Study on Air Pollution and Lung Diseases in Adults (the SAPALDIA study).

The oxygen concentration (O2%) produced by 12 type A concentrators, with a working time of 28-18,099 h, and 6 type B concentrators, with a working time of 0-3,033 h, was measured over a 12 month period in the user's home, at a flow rate of 2 l.min-1. One hundred and two measurements of O2% (mean 82.9), made at least once monthly by a visiting nurse, showed that type A concentrators were usually delivering less than 92% expected O2. Four concentrators were delivering less than 40% O2 after a working time of only 4,000 h. Sixty two measurements made by the manufacturer confirmed these findings (mean 86.8). The 18 measurements performed by the nurse on the type B concentrators showed expected O2% values (mean 93.1). Our study demonstrates the necessity of regular clinical and technical surveillance, at the user's home, during long-term domiciliary oxygen therapy and the need for the manufacturer to incorporate an alarm system monitoring the O2% into oxygen concentrators.