Relationship between silicosis and lung function.
In an examination of the relationship between silicosis and lung function, relevant studies of silica-exposed workers were reviewed. Smoking, dust exposure, and emphysema are three important factors that can confound the association between silicosis and lung function. Despite the importance of smoking in relation to lung function, some studies did not control for smoking, or smoking was controlled inadequately. The data suggest a weak association between lung function (mainly obstruction) and dust exposure, although some studies had crude measures of exposure. In general, the lung function of those with radiographic silicosis in category 1 was indistinguishable from those in category 0. Those in category 2 had small reductions in lung function relative to those with category 0 and little difference in the prevalence of emphysema. There were slightly greater decrements in lung function with category 3 and more significant reductions with progressive massive fibrosis. Emphysema was related to higher categories of silicosis, as well as to smoking. Silica exposure was often inadequately controlled in studies examining silicosis and lung function. A few studies suggested that emphysema is an independent risk factor associated with significant reductions in lung function.