Refractory ceramic fibre production workers. Analysis of radiograph readings.

As part of a morbidity study in seven European refractory ceramic fibre production plants co-ordinated by the Institute of Occupational Health, Birmingham, all workers were offered chest radiography. The response rate was 95%. For each of the 543 male responders, the median of three independent readings, using the ILO 1980 Classification of the Radiographic Appearances of the Pneumoconioses, was related to demographic variables and to indices of employment and exposure. Thirty-eight (7.0%) films showed small opacities of category 1/0 or more and five (0.9%) revealed bilateral pleural abnormalities. No large parenchymal opacities were reported. Rounded opacities were strongly associated with age, and their prevalence also varied between the seven production plants studied. There was some evidence of an association with time in the industry, and also with the current non-respirable fibre exposure level. The highest prevalences occurred for the highest time or exposure level. Irregular opacities were primarily related to age, and years of employment. Overall, there was some slight association between the prevalence of small opacities and working in ceramic fibre production. Because of the absence of pleural abnormalities and of an association of irregular small opacities with the fibre exposure indices, it seems unlikely that fibre exposure was the sole or main cause of radiographic abnormalities. The small opacities may have been related to another exposure in these production plants, to which the non-respirable fibre exposure index correlated.