Impact of introducing electric vehicles on ground-level O₃ and PM_2.5 in the Greater Tokyo Area: Yearly trends and the importance of changes in the Urban Heat Island effect

Abstract. Battery electric vehicles (BEVs) are considered a solution for global warming and air pollution, and several countries have announced a shift to BEVs in the 2030s. This study is an evaluation of changes in the urban heat island (UHI) effect in the Greater Tokyo Area (GTA) of Japan as a result of introducing BEVs using numerical weather prediction. The results indicated that the substitution of internal combustion vehicles with BEVs led to a maximum decrease of 0.2 °C in the local temperature for the metropolitan GTA. Estimation of the effects of introducing BEVs on tropospheric ozone (O₃) and fine particulate matter (PM_2.5) using a regional chemical transport model indicated that mitigating against the UHI effect led to a decline in the ground-level O₃ formation due to decreased atmospheric chemical reactions and lower biogenic volatile organic compounds (BVOC). The decrease in vehicular exhaust emissions and increase in power plant emissions were nonlinear, and the total change in O₃ depends on season and location. The temperature decrease that resulted from the mitigation of UHI resulted in enhanced particle coagulation, with an increase in ground-level PM_2.5 formation in several regions. Furthermore, a decrease in the BVOC emissions also resulted in increased PM_2.5 owing to enhancement of the OH + SO₂ reaction. The total prevented annual premature deaths of 175 and 77 that resulted from the changes in O₃ and PM_2.5, respectively, indicate the positive effects of BEV introduction on air quality management in the GTA, and may be applicable to other megacities worldwide.