[Evaluation of the effectiveness of medical prevention of pneumoconiosis based on studies of its incidence in selected coal mines].

In a group of 3,938 persons--pit miners of 3 coal mines--employed over 8 years, full-size X-ray pictures of the chest have been taken and through a special questionnaire information has been collected on the length of employment, workstation, risk of dustiness, exposure to fibrogenic dusts outside the mine. Basing on the studies, the mean annual incidence of pneumoconiosis in particular mines has been calculated. The data has been compared with the mean annual incidence rate of pneumoconiosis calculated for 10 years prior to epidemiological studies and based on the primary selection by means of small-size pictures. This comparison indicated that the full-size pictures revealed 3-7 times more pneumoconioses as compared to the hitherto applied system. The comparison of full-size and small-size X-ray pictures demonstrated that the lesions visible in full-size pictures have not been registered in small-size pictures in as many as half of the cases. The obtained results indicate that the effectiveness of the hitherto applied system of medical prevention of pneumoconiosis is insufficient. A change in this system is indispensable; miniature roentgenography should be replaced by full-size X-ray pictures.