Historical and future polychlorinated biphenyl emission trends in Japan

Different countries produce varying amounts of polychlorinated biphenyls (PCBs), have distinct patterns of use, and regulations for treatment and disposal. Therefore, long-term countermeasures require an understanding of historical and future emission trends at the national scale. In this study, we estimate historical PCB emissions from products containing PCBs, unintentional production related thermal processes, and disposal processes for products containing PCBs from 1950 to 2030 in Japan. In addition, in order to validate the results, we estimated PCB concentrations in environmental media using an environmental fate model and a sensitivity analysis was conducted. Our results show that total PCB emissions were approximately 2.6 tons in 2017, which was a dramatic decrease from peak emissions of 68.9 tons in 1970. We suggest that PCB emissions may continue to decrease, reaching 0.707 tons in 2030. This trend might be due to a change in the emission source; it was estimated that the main emission source in past and recent years was volatilization from large products containing PCBs. However, it is predicted that the main emission sources in the future will be unintentional PCB production from thermal processes and volatilization from small untreated products containing PCBs, although the estimation of environmental PCB levels suggested that there might be unknown emission sources. Additionally, the sensitivity analysis indicated that some parameters greatly influenced the estimation of recent and future emissions. In particular, there was no detailed information concerning the applications for PCBs, which potentially had a large influence on the estimation of future emissions.