A 21-year radiographic follow-up of workers in the diatomite industry
Cooper, W.C.; Jacobson, G.
Journal of Occupational Medicine. Official Publication of the Industrial Medical Association 19(8): 563-566
1977
ISSN/ISBN: 0096-1736 PMID: 197217 Document Number: 112372
Review of the chest films of 428 current employees of a diatomite mining and processing plant, taken 21 yr after a Public Health Service survey in 1953, shows a continued drop in the incidence of pneumoconiosis. Of the current work force, 20 (4.7%) had films interpreted as positive for pneumoconiosis at the UICC [International Union Against Cancer]/Cincinnati [Ohio, USA] level of 1/1 or higher. Six others were classified 1/0. In 8 of the former and 4 of the latter, changes were present in preemployment films or were not regarded as representing pneumoconiosis, so that only 12 (2.8%) classified 1/1 and 2 (0.5%) classified 1/0, were regarded as consistent with diatomite pneumoconiosis. All but 2 of these 14 men were empoyed before 1953. The 129 current employees who were on the work force 20 yr or more included 13 with positive films considered consistent with diatomite pneumoconiosis; 6 of these were negative in 1953, 1 doubtful and 6 had definite pneumoconiosis at that time. All but 2 had mill exposures. Only 4 individuals had complicated or coalescent lesions; these were all category A, and were mill workers who were employed 27-46 yr. No massive coalescent lesions or distorting changes are present in the current work force. Study of terminated workers has confirmed the favorable results found in current employees. The almost complete elimination of new cases of diatomite pneumoconiosis is attributed to a program of strict dust control programs, supplemented by the mandatory wearing of respirators at jobs with high risk of cristobalite exposures.