Mortality of Vermiculite Miners Exposed to Tremolite

Abstract

Abstract Closely similar cohort mortality studies were conducted independently and in parallel by groups from NIOSH and McGill University among past and present employees of a Montana mine and mill where the vermiculite ore is contaminated by amphibole fibres, mainly of the tremolite-actinolite series. The NIOSH cohort consisted of 569 men hired before 1970, while the McGill cohort consisted of 406 men hired before 1963, and men in both cohorts were employed at least 1 year. Exposures were estimated for each man in fibre-years (f-y) from work histories and all available samples of airborne dust tested by governmental agencies or the company since 1956. A man-years analysis against U.S. white male mortality showed increased SMR's from lung cancer and non-malignant respiratory disease (NIOSH:2.15 and 2.46; McGill: 2.45 and 2.55). In relation to exposure, the SMR for lung cancer was estimated to increase 0.6% by NIOSH and 1.1% by McGill with each unit increase in f-y. Mortality from mesothelioma was reported as the underlying cause of death in 2 cases in the NIOSH cohort, and as the underlying or contributing cause of death in 4 cases in the McGill cohort.