Asbestos Discussion: Mortality Study at the Libby Mine from 1963-1990

Read about the asbestos mortality study conducted at the Libby, Montana mine site.  This section details exposure limits.

Under contract with the company that operated the mine and mill from 1963–1990, McDonald et al. (1986) evaluated the mortality experience through mid-1983 of 406 white men with a mean cumulative exposure of 144.6 fibers/cc-years; these men had at least 1 year of tenure and were hired before 1963.

McDonald et al. (2004) later independently reevaluated the mortality experience of these workers with follow-up through 1998. Overall SMRs of 2.4 (95% CI, 1.7–3.2) for respiratory cancer (44 deaths; ICD-9 codes 160–165) and 3.1 (95% CI, 2.3–4.1) for nonmalignant respiratory disease (51 deaths; ICD-9 codes 010–108 and 460–519) were reported.

Using Poisson regression, McDonald et al. (2004) found an exposure-response relationship between cumulative fiber exposure and respiratory cancer [highest quartile of cumulative exposure relative risk (RR) = 3.2; 95% CI, 1.2–8.8], nonmalignant respiratory disease (highest quartile RR = 3.1; 95% CI, 1.2–8.4), and mesothelioma (highest quartile RR = 3.4; 95% CI, 0.4–33.2). Asbestosis mortality per se was not described.