AIRWAY RESPONSIVENESS AND JOB SELECTION - A STUDY IN COAL-MINERS AND NON-MINING CONTROLS

Background-It has been suggested that health related job selection is a major cause of the healthy worker effect, and may result in inaccura te estimates of health risks of exposures in the working environment. Improved understanding of self selection, including the role of airway hyperresponsiveness, should improve accuracy in estimating occupation al risks. Methods-We evaluated symptoms of the respiratory tract, lung function, occupational and smoking histories, and airway responsivene ss from a cross sectional survey of 478 underground bituminous coal mi ners and non-mining controls. Workers with abnormal spirometry were ex cluded from methacholine testing. Results-Methacholine responsiveness (greater than or equal to 15% decline in forced expiratory volume in o ne second) was associated in both miners and controls with reduced ven tilatory lung function and an increased risk of respiratory symptoms. Miners with the longest duration of work at the coal face had a low pr evalence of methacholine responsiveness, compared with miners who had never worked at the coal face (12% v 39%, P < 0.01). Throughout their mining careers, miners who responded to methacholine were consistently less likely to have worked in dusty jobs than miners who did not resp ond to methacholine. Conclusions-These results provide evidence that w orkers who are employed in dusty jobs are less likely than their unexp osed coworkers to show increased non-specific airway responsiveness, p resumably as a result of health related job selection. Surveys of work ers in which responsiveness data are unavailable may underestimate the effects of dust exposure on respiratory health.