title: A 26-year radiographic follow-up of workers in a diatomite mine and mill.
abstract: Chest roentgenograms of 473 employees of a California diatomite plant were reviewed as part of periodic reevaluation of the efficacy of the dust control program. The plant's processing of diatomite included flux-calcination, which provided opportunities for exposure to cristobalite. The films examined were those of workers with at least five years of service. Only 11 films were interpreted as showing changes consistent with pneumoconiosis, i.e., small opacities of profusion categorized as 1/1 or greater. Only six were classified as 1/2 or more. All who developed categories 1/1 or higher during their employment had more than 25 years of service. No large opacities were reported. The low prevalence of abnormalities and the absence of definite pneumoconiosis in employees with fewer than 25 years of service was in striking contrast with findings in 1953. At that time more than 25% of those with five or more years of employment had roentgenographic evidence of pneumoconiosis and over 10% had confluent changes producing large opacities.
mesh_terms: D000328:Adult; D000368:Aged; D007692:Diatomaceous Earth / Q000009:adverse effects*; D004391:Dust / Q000009:adverse effects; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D008906:Mining; D010994:Pleura / Q000000981:diagnostic imaging; D011009:Pneumoconiosis / Q000000981:diagnostic imaging* / Q000209:etiology; D011859:Radiography; D012822:Silicon Dioxide / Q000009:adverse effects*; D013997:Time Factors
chemical_list: D004391:Dust; D007692:Diatomaceous Earth; C033787:diatomite; D012822:Silicon Dioxide