Mortality after exposure to polychlorinated biphenyls and polychlorinated dibenzofurans: A meta-analysis of two highly exposed cohorts

Both Yucheng and Yusho were events of accidental exposure to highly doses of polychlorinated biphenyls and dibenzofurans in Asian people. Mortality experiences caused by various diseases were reported in both cohorts with similar and dissimilar findings. We thus conducted a meta-analysis of two cohorts to reevaluate the effects of PCBs and PCDFs on major causes of mortalities. Two recently updated Yucheng and Yusho mortality studies were included. For selected diseases, standardized mortality ratios (SMR) and 95% confidence intervals (95% CI) were extracted. Meta-analyses were conducted using a random-effects model only when heterogeneity (I²>50% and/or p value <0.10 by the Q test) was not found. A total of 1,803 Yucheng subjects (male, N=830; female, N=973) with 48,751 person-years of follow-up and 1,664 Yusho subjects (male, N=860; female, N=804) with 50,773 person-years are included. An increase in all-cause mortality (pooled SMR=1.2, 95% CI: 1.1-1.3, I²=0.0%), all cancers (pooled SMR=1.3, 95% CI: 1.1-1.6, I²=0.0%), lung cancer (pooled SMR=1.7, 95% CI: 1.2-2.3, I² =0.0%), heart disease (pooled SMR=1.3, 95% CI: 1.0-1.7, I²=43.4%) and hepatic disease (pooled SMR=1.9, 95% CI: 1.3-2.8, I²=0.0%) were found in pooled males. Significant elevation from liver cancer was found in pooled females (pooled SMR=2.0, 95% CI: 1.1-3.6, I²=0.0%). This meta-analysis of Yucheng and Yusho cohorts showed similar elevation from all cancer, lung cancer, heart disease and hepatic disease mortalities in exposed men. Furthermore, a new finding of elevated liver cancer mortality in exposed women was identified.