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Prevalence of clinical and radiographic abnormalities in 150 workers exposed to non-calcined diatomaceous earth in central California.

Howard-J; Culver-BD; Sargent-EN
NIOSH 1990 Nov; (II):1202-1203
A study of the prevalence of clinical and radiographic abnormalities in workers exposed to noncalcined diatomaceous-earth (68855549) (diatomite) was conducted. The study group consisted of 150 workers, 121 males, employed at Excel Mineral Company (SIC-3295), in the southern San Joaquin Valley, California. Workers had been exposed to diatomite dust for periods up to 17 or more years. The workers completed a questionnaire to obtain information on general health status, respiratory symptoms, and occupational history. Pulmonary function testing was performed and chest X-rays were obtained. The chest X-rays were read for opacities using the 1980 International Labour Organization System. Exposure indices (EIs) were estimated from the occupational history data. Dust samples obtained at the mill were analyzed for their mineral content. Wheezing was the most frequently reported respiratory complaint. The frequency of respiratory symptoms increased with increasing EI. Pulmonary function testing revealed no obstructive or restrictive defects. Eleven subjects (7%) had radiographic profusion scores of Three subjects (2%) had definite radiographic evidence of pneumoconiosis, profusion scores of 1/1 or greater. The dusts contained 69% amorphous silica (7631869) and 6% crystalline silica (14808607). The crystalline silica was present as alpha-quartz (14808607) and cristobalite (14464461). The authors conclude that the prevalence rate of pneumoconiosis in the cohort is lower than that noted in previous studies. Since the concentration of fibrogenic silica noted in the dust samples generally exceeds that normally noted in uncalcined diatomite, employees at Excel Mineral may be at greater risk of pneumoconiosis than other employees in the California diatomite industry.
Mineral-dusts; Occupational-exposure; Dust-exposure; Respiratory-system-disorders; Chest-X-rays; X-ray-analysis; Epidemiology; Lung-lesions
68855-54-9; 7631-86-9; 14808-60-7; 14808-60-7; 14464-46-1
Publication Date
Document Type
Conference/Symposia Proceedings
Fiscal Year
NTIS Accession No.
NTIS Price
Identifying No.
(NIOSH) 90-108
Priority Area
SIC Code
Source Name
Proceedings of the VIIth International Pneumoconioses Conference