Regional air quality modeling of ethylene oxide in the Greater Tokyo Area of Japan

Ethylene oxide (EtO) is a volatile organic compound that poses both acute and chronic risks to human health, prompting governments worldwide to implement measures aimed at reducing ambient EtO concentrations. In this study, regional chemical transport model calculations were performed using the EtO emission inventory provided by the Ministry of Economy, Trade and Industry and the Ministry of the Environment, Japan. The target area and period were the Greater Tokyo Area (GTA) in 2017. The results indicated that the modeled atmospheric EtO concentrations were lower than the observed concentration at all monitoring sites in the GTA, with the discrepancy reaching up to one order of magnitude. Long-range transport of EtO from the Asian continent to Japan was not identified as the primary cause of this discrepancy. Instead, the significant discrepancy might be attributed to global background concentrations of EtO, resulting from its long tropospheric lifetime. To improve the accuracy of atmospheric EtO assessments using chemical transport models, it is essential to account for global emissions.