Shape of small opacities and lung function in coalworkers.

Lung function and chest radiographs were reviewed in 357 coalworkers who had been referred from the Cardiff Pneumoconiosis Medical Panel. The chest films were read according to the 1980 ILO classification of radiographs by three experienced readers. An irregularity score, reflecting the shape of the small opacities, was derived from the readings and compared with the lung function variables. Men with higher irregularity scores had significant reductions in ventilatory capacity and gas transfer factor, with no change in total lung capacity, after age, height, profusion of small opacities, and smoking habit had been taken into account. The effects were present both in those with and in those without large opacities. The agreement between readers over the shape of opacities was almost as good as for their profusion. Men with rounded opacities had a lower gas transfer factor if they were predominantly of the "p" type. The results are consistent with those for a combination of emphysema and interstitial fibrosis, which has been found in coalworkers with irregular opacities.