Rogan, J. M., Attfield, M. D., Jacobsen, M., Rae, S., Walker, D. D., and Walton, W. H. (1973).British Journal of Industrial Medicine, 30, 217-226. Role of dust in the working environment in development of chronic bronchitis in British coal miners. In the course of a long-term prospective study of chronic respiratory disease in British coal miners the effects on pulmonary ventilatory function of exposure to airborne dust, of simple pneumoconiosis, and of chronic bronchitis have been examined in a group of 3581 coalface workers. The men were employed in 20 collieries throughout the British coalfields. Their cumulative exposures to coal mine dust in the respirable range (1-5 μm) were calculated from detailed dust sampling results at their work places during a 10-year period and from estimates of earlier exposures based on records of their industrial histories. A progressive reduction in FEV1·0 with increasing cumulative exposure to airborne dust has been demonstrated. This effect was evident also in a subgroup of the men studied who reported no signs of mild bronchitic symptoms (cough and phlegm for at least three months in a year). Among men with pneumoconiosis there was no evidence of a reduction of FEV1·0 in excess of that attributable to their dust exposures, smoking habits, age, and physique. Increasing severity of bronchitic symptoms was associated with a loss in FEV1·0 greater than that expected from the effects of dust exposure as measured, smoking, age, and physique. Possible explanations for this phenomenon are discussed. It is suggested that the results may indicate that once early bronchitic symptoms are present the disease may progress and ventilatory capacity may deteriorate independently of factors initiating the disease process.