Objectives: To investigate types of cancer caused by occupational exposure to vinyl chloride monomer (VCM) and the temporal mortality trends of these cancers in workers from polyvinyl chloride (PVC) manufacturing factories in Taiwan, with follow-up of the cohort extended by 15 years, from 1980 to 2007. Methods A retrospective cohort study of workers from six PVC factories in Taiwan was conducted. 3336 male PVC workers were enrolled and further linked with the National Mortality Registry and National Household Registry databases. Standardised mortality ratios (SMR) with 95% CIs were calculated and compared to the general Taiwanese male population. Cause-specific mortality between two study periods, 1980-1997 and 1998-2007, was compared. Six-year moving averages of the SMRs were calculated to examine mortality trends.
Results: Liver cancer mortality increased during 1989-1994 (SMR 1.90, 95% CI 1.01 to 3.25), reached a peak during 1991-1996 (SMR 2.31, 95% CI 1.39 to 3.61) and became non-significant during 1994-1999 (SMR 1.42, 95% CI 0.80 to 2.34). Leukaemia mortality significantly increased during 1984-1989 (SMR 6.06, 95% CI 1.24 to 17.53), reached a peak during 1985-1990 (SMR 7.56, 95% CI 2.06 to 19.35) and became non-significant during 1991-1996 (SMR 3.24, 95% CI 0.39 to 11.69). The mortality trend for haemolymphopoietic cancer showed a similar pattern to that of leukaemia.
Conclusions: VCM may increase the risk of liver cancer and leukaemia. When VCM exposure was controlled at worksites, mortality from these cancers returned to background levels.