Estimated HRs for total and cause-specific mortality associated with CDE in the cohort (n = 74,040), 1960–2003.

All Cox proportional hazards models included age as the time variable. Categorical analyses were based on levels of CDE, including unexposed, low, medium, and high; the unexposed level was used as the reference category (low level for pneumoconiosis). In all models, the HRs associated with CDE were adjusted for gender, year of hire (five categories: 1955 or earlier, 1956–1960, 1961–1965, 1966–1970, and 1970 or later), age at hire (continuous), and type of mine/factory (four categories: tungsten, iron/copper, tin, and pottery).aLevels were tertiles of CDE of all the workers with exposure to silica dust: low, 0.01–1.23 mg/m3-y; medium, 1.24–4.46 mg/m3-y; and high, >4.46 mg/m3-y.bAssessed by including the median values of exposure within each category as a continuous variable in the model, including the reference category.