This study evaluated non-respiratory effects in a cohort of asbestos-exposed vermiculite workers. We followed 1672 white male Libby, Montana, vermiculite miners, millers, and processing workers with amphibole fiber exposure. Using the NIOSH Life Table Analysis System, age-adjusted underlying cause arthritis mortality through 2001 was compared to white men in the U.S. population. Allowing for a 15-year lag, these workers were 9.5 times (95% CI 3.1-23.5) more likely than expected to die with a diagnosis of arthritis (n ¼ 5). After death certificate review to identify any mention of rheumatoid arthritis (n ¼ 12 deaths), multiple cause mortality was evaluated using the Cox proportional hazards model. After controlling for years since hire and pack years, using age at death as the time dimension, the relative hazard ratio (HR) for rheumatoid arthritis was 1.3 (95% CI 0.8-1.9) per 100,000 fibers/cc-years. For duration, the HR was 1.05 (95% CI 0.99-1.12), suggesting a 5% increase in risk of dying with rheumatoid arthritis for each year of employment. The HR for pack-years was 1.017 (95% CI 0.998-1.036). The association with smoking was expected given previous research on rheumatoid arthritis. These findings are consistent with a recently published report of excess rheumatoid arthritis morbidity among a subset of Libby vermiculite workers (Noonan et al., 2006). Taken together, that report and the findings reported here suggest that exposure to asbestos fibers may be associated with at least one systemic autoimmune disease. Disclaimer: This abstract does not necessarily reflect EPA policy.
American Journal of Epidemiology; 41st Annual Meeting Society for Epidemiologic Research Chicago, Illinois, June 24-27, 2008