Dust exposure and pneumoconiosis in a South African pottery. 2. Pneumoconiosis and factors influencing reading of radiological opacities.

A cross sectional radiological survey of workers exposed to pottery dust during the manufacture of wall tiles and bathroom fittings was conducted in a South African factory. Roughly one third of workers with 15 or more years of service in high dust sections of the factory had pneumoconiosis. Previously undiagnosed advanced cases, including two with progressive massive fibrosis, were working in dusty occupations. A firm diagnosis of potters' pneumoconiosis was made in 11 of the 358 workers radiographed; all had served more than 10 years suggesting that radiography of workers with more than 10 years service would be a successful case finding strategy in South Africa. A combination of rounded and irregular opacities was the most common radiological finding in the workers with pneumoconiosis (55%). Three readers reported on the chest radiographs, and all found an association between small radiological opacities, which were usually irregular or a combination of irregular and rounded, and exposure to pottery dust. The occurrence of irregular radiological opacities in workers exposed to pottery dust deserves further study. The least experienced reader significantly associated age with small opacities when duration of service (years) was used to measure exposure to dust. Sex was not an important predictor of radiological changes consistent with pneumoconiosis. Breast shadows were not an important cause of false positive readings and participating women did not develop pneumoconiosis after less exposure than men.