DOES OCCUPATIONAL EXPOSURE TO BROWN-COAL DUST CAUSE A DECLINE IN LUNG-FUNCTION

Objectives-To determine if the rate of change in forced expiratory vol ume in one second (FEV1) in subjects with high exposure to Latrobe Val ley brown coal dust was significantly greater than the rate of change among subjects with low exposure. Methods-A retrospective dynamic coho rt design with variable time windows. This study was conducted over a period of 14 years from 1980 to 1994 and used data collected by the St ate Electricity Commission (SEC) Lung Function Unit for an asbestos su rveillance programme. The subjects were exposed to low, medium, or hig h levels of coal dust. Basic spirometry with wedge bellows spirometers was used to assess lung function. A general linear model (GLM) was us ed to assess the effects of smoking and exposure to coal dust upon the change in forced expiratory volume in one second (FEV,) while adjusti ng for age and height. Results-The mean (95% confidence interval (95% CI)) rate of decline in FEV, was 40 (36 to 44) ml/year. Age was a sign ificant predictor of change. A significant effect was found for smokin g (P=0.02) and for exposure to coal dust (P=0.008). The only significa nt difference with exposure to coal dust was between the high and mixe d exposure categories. Conclusion-There is no convincing evidence of e xcessive decline in FEV, with exposure to coal dust >0.75 mg/m(3). The absence of a dose response relation provides some evidence against a causal relation. On the basis of this study, reduction of the exposure standards currently applied to brown coal dust in the Victorian elect ricity industry is not warranted to prevent respiratory disease.