Risk of bile duct cancer among printing workers exposed to 1,2-dichloropropane and/or dichloromethane

Risk of bile duct cancer among printing workers exposed to 1,2-dichloropropane and/or dichloromethane: Tomotaka SOBUE, et al. Department of Environmental Medicine and Population Sciences, Graduate School of Medicine, Osaka University— Objectives: We conducted a retrospective cohort study to examine the risk of bile duct cancer among current and former workers in the offset color proof printing department at a printing company in Osaka, Japan. Methods: Standardized incidence ratios (SIRs) between January 1, 1985, and December 31, 2012, were estimated for the cumulative years of exposure to two chemicals, dichloromethane (DCM) and 1,2-dichlo- ropropane (1,2-DCP), using the national incidence level as a reference. In addition, we examined risk patterns by the calendar year in which observation started. Results: Among 106 workers with a total of 1,452.4 person-years of exposure, 17 bile duct cancer cases were observed, resulting in an estimated overall SIR of 1,132.5 (95% confidence interval (CI): 659.7−1,813.2). The SIR was 1,319.9 (95% CI: 658.9−2,361.7) for those who were exposed to both DCM and 1,2-DCP, and it was 1,002.8 (95% CI: 368.0−2,182.8) for those exposed to 1,2-DCP only. SIRs tended to increase according to years of exposure to 1,2-DCP but not DCM when a 5- year lag time was assumed. The SIRs were higher for the cohorts in which observation started in 1993−2000, particularly in cohorts in which it started in 1996−1999, compared with those in which it started before or after 1993−2000. Conclusions: We observed an extraor- dinarily high risk of bile duct cancer among the offset color proof printing workers. Elevated risk may be