Mortality of brain tumors among asbestos insulation workers in the United States and Canada.

Death resulting from brain tumors among workers in the petrochemical industry have called attention to the possibility that these neoplasms may be the result of occupational exposure to carcinogens. We have examined the experience of a cohort of 17,800 insulation workers known to be at significant increased risk of cancer at a number of sites (lung, mesothelioma, gastrointestinal, oral cavity, pharyngeal, larynx, renal) to ascertain whether their asbestos exposure also increased their risk of brain tumors. From 1967 to 1979, there were 24 deaths from primary brain tumors in this cohort, somewhat more than were anticipated (18.0 such deaths were expected based on U.S. general population data, and 20.5 if smoking was taken into account). The excess was not "statistically significant" at the 5% level although this does not rule out the possibility of an etiological association. It was of interest that the observed excess was concentrated (about twice expected) among insulators in the younger ages (those under 50) and during the early period after onset of work (15-24 years), in contrast with age distribution and latency in other asbestos-associated neoplasms. This may have relevance to theoretical concerns about questions of initiation and promotion in the etiology of cancer, particularly with regard to brain tumors.