AN EPIDEMIOLOGICAL-INDUSTRIAL HYGIENE STUDY OF TALC WORKERS

Abstract

Abstract Two-hundred and ninety-nine (299) miners and millers exposed to talc from Montana, Texas and North Carolina were examined in a cross-sectional study of respiratory systems, lung function and chest X-rays. Work histories were taken from personnel records. Personal respirable dust samples were collected for all jobs. Cumulative exposure was calculated by summing the products of the estimated exposure for each job and the length of time worked in that job. The average time worked was 7, 6, and 10 yr and the average exposure (cumulative exposure/total time worked) was 1.2,2.6, and 0.3 mg m~3 in Montana, Texas, and North Carolina respectively. Free silica content of bulk samples was low (below the limit of detection in Montana, 1.5% in North Carolina, and 2.2% in Texas). No fibres were observed under the light microscope. Under the transmission electron microscope, tremolite and antigorite fibres (0.5-3 μm length) were observed on the Texas talc, acicular particles (aspect ratios 5-100 to 1 and some diameters less than 0.1 jum) in North Carolina talc, and no fibres in the Montana talc. The differences in age-corrected symptom prevalences (cough, phlegm, and dyspnea) between regions, when compared by both smoking categories and exposure groups were not statistically significant. None of the symptoms showed any consistent association with years worked or cumulative exposure. Symptom prevalence was not elevated compared with blue collar workers and potash miners. There were two cases (less than 1 %) of grade 1 small rounded opacities. The prevalence of bilateral pleural thickening among workers 40 yr or older was 7,16, and 14% in Montana, Texas, and North Carolina, and 0, 0, and 10% in those less than 40 yr of age. No non-smoker had bilateral pleural thickening and there was a slight tendency for the prevalence to increase with exposure. Workers with bilateral pleural thickening had lung function 10-20% below workers with no pleural thickening. They had also worked twice as long (13 yr) and an average of 13 yr between beginning exposure to talc and the time of the X-ray. The prevalence of bilateral pleural thickening was elevated in workers 40 yr or older compared with blue collar workers and potash miners. There also were no demonstrated differences in prevalence when the subjects in this study were compared with workers exposed to New York talc which contains tremolite and anthophyllite. For the entire study population no association of reduced lung function with exposure was demonstrated. After adjustments for age, height, and smoking, FEVi and FVC were not detectably different compared with potash miners and blue collar workers; however, flow rates at low lung volumes were' reduced 4-19%. There was little difference among these three populations in age coefficients for FEVX, FVC, and flow rates by smoking category. Predicted pulmonary function of the study population was elevated compared with New York talc workers. There were no significant increases in symptoms or pneumoconiosis among the study group of talc workers nor significant reductions in lung function; however, the average amount of time worked by the study group was short. Bilateral pleural thickening was significantly increased and was associated with decreased pulmonary function. The prognostic significance of the pleural thickening awaits prospective evaluation.