Radiological appearances of irregularly shaped small shadows on coalminers’ chest radiographs.

Five experienced readers classified, according to the ILO (1980) scheme, 3669 radiographs from 707 British coalworkers. Irregular opacities were more common at lower profusion categories than at higher profusions, and were more likely to be observed in the middle and lower zones of the lungs, whereas rounded opacities tended to appear in the middle and upper zones. It was concluded that published estimates of the risk of simple pneumoconiosis of Category 2 or more were not seriously deficient as a result of being based on rounded opacities only. It is suggested that any revision of the ILO (1980) classification scheme should seek to improve reader agreement on shape and position of opacities as well as on their profusion.