Characteristics of the cohort (n = 74,040) based on CDE, 1960–2003.

Values expressed as mean ± standard deviation, unless otherwise indicated. Percentages may not total 100 due to rounding.aLevels are 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.bData were available for the sub-cohorts that had been followed through the end of 2003. Smokers were defined as those who had smoked regularly for over 1 y. Smokers who stopped smoking within 1 y before the end of follow-up were defined as current smokers.cThese characteristics were calculated among workers exposed to silica dust. Mean silica dust concentration was calculated as CDE divided by duration of silica dust exposure.dThese characteristics were calculated among workers diagnosed with pneumoconiosis. Latency of pneumoconiosis was defined as the period between the year of first exposure to dust and the year of first diagnosis of pneumoconiosis.NA, not applicable.