A regional meteorology-chemistry model was used to assess the effects of passenger car conversion to battery electric vehicles (BEV) on summer O3 concentrations in Kanto (Japan's most populous region). Four sensitivity experiments were conducted on different on-road and upstream (power plant and gas station) emission conditions. Daytime 8-h maximum O3 decreased by 3 ppb (5%) and 4 ppb (5%) in urban and inland suburbs, respectively. O3 levels decreased even in urban (VOC-limited regions) because exhaust and evaporative VOC emissions from vehicle and gas stations were reduced effectively (especially alkenes from gasoline evaporation; highly reactive in O3 formation). In the suburbs (NOx-limited regions), reduction of exhaust NOx by BEV shifting was significant, but in urban, even only evaporation measures induced almost the same O3 reduction effect as BEV shifting. The additional emissions from thermal power plants due to BEV night charging contributed little to the next day's daytime O3 on a monthly average basis. However, on some days, pollutants were stored in the upper part of the stable nighttime boundary layer and could affect the surface O3 as the next day's mixed layer development. Depending on the O3 sensitivity regime (NOx-or VOC-limited), additional NOx plumes from rural (urban) power plants tended to increase (decrease) the next day's O3. However, the distribution of the regime changes temporally and spatially. The H2O2/HNO3 ratio was discovered to be a clear indicator for distinguishing regime boundaries and was effective in predicting positive or negative O3 sensitivity to the additional emissions from power plants.

Ozone (O 3 ) in surface air has adverse effects on human health, particularly in the respiratory system (e.g., Tager et al., 2005;Zhang et al., 2019). O 3 is not only an oxidizing agent by itself, but can also generates strong secondary oxidants such as ascorbic acid ozonide (AOZ) when degraded by antioxidants in the body (Enami et al., 2008;Tang et al., 2007). Furthermore, water-soluble gaseous pollutants such as SO 2 influence only the upper respiratory tract, whereas O 3 reaches deep into the lungs because of its hydrophobic nature (Schraufnagel et al., 2019).

The impacts of renewable energy shifting, passenger car electrification, and lightweighting through 2050 on the atmospheric concentrations of PM2.5 total mass, Fe, Cu, and Zn, and aerosol acidity in Japan were evaluated using a regional meteorology–chemistry model. We focus on the changes in on-road exhaust/non-exhaust and upstream emissions. The domestic primary emissions of PM2.5, Fe, Cu, and Zn were reduced by 9%, 19%, 18%, and 10%, and their surface concentrations in the urban area decreased by 8%, 13%, 18%, and 5%, respectively. On a PM2.5 mass basis, battery electric vehicles (BEVs) have been considered to have no advantage in non-exhaust PM emissions because the increased tire and road wear and resuspension due to their heavy weight offset the benefit of brake wear reduction by regenerative brake. Indeed, passenger car electrification without lightweighting also did not significantly reduce PM2.5 concentration in urban area in this study (-2%) but was highly effective in reducing Fe and Cu concentrations owing to their high brake wear dependence (-8% and -13%, respectively). Furthermore, the lightweigting of the drive battery and the body frame of BEVs reduced even tire and road wear and resuspension. Therefore, vehicle electrification and lightweighting could effectively reduce the risks of respiratory inflammation. The reduction of SOx, NOx, and NH3 emissions changed aerosol acidity in urban area (maximum pH ±0.2). However, changes in aerosol acidity only slightly changed water-soluble metal concentrations (maximum +2% for Fe and +0.5% for Cu and Zn); therefore, it is important to focus on reducing primary metal emissions.

<p>Transition metal components in PM<sub>2.5</sub> induce inflammation of the respiratory system. The increase in aerosol acidity due to gaseous pollutants promotes metal dissolution and contributes to redox activation. In this study, the impact of renewable energy shifting, passenger car electrification and light-weighting on atmospheric concentration of PM<sub>2.5</sub> total mass, Fe, Cu, Zn and aerosol acidity in Japan over 2050 was evaluated using a regional meteorology-chemistry model. The primary emissions of PM<sub>2.5</sub>, Fe, Cu, and Zn were reduced by 9%, 19%, 18% and 10%, and their surface wide-area concentrations decreased 6 – 8%, 10 – 12%, 16 – 18% and 2 – 4%, respectively. On a PM<sub>2.5</sub> mass basis, battery electric vehicles (BEVs) have been considered to have no advantage in non-exhaust PM emissions because the increased tire and road wear and resuspension due to their heavy weight offset the benefit of brake wear reduction by regenerative brake. Indeed, passenger car electrification without light-weighting also did not significantly reduce total primary PM<sub>2.5</sub> emissions in Japan in this study (-1.4%), but was highly effective in reducing metals, especially Fe and Cu (-6.7% and -11.4%, respectively). Furthermore, this study estimated that even tire and road wear and resuspension could be reduced if the drive battery and body frame were light-weighted, and the benefit would be larger. Therefore, vehicle electrification (mainly BEVs) and light-weighting could be one of the effective means of reducing the risks of respiratory inflammation. The renewable energy shifting reduced SO<sub>x</sub> and NO<sub>x</sub> emissions from thermal power plants and decreased aerosol acidity near power plants (approximately pH +0.2), while the passenger car electrification reduced NO<sub>x</sub> and NH<sub>3</sub> emissions and slightly increased aerosol acidity in urban, as a result of acid-base balance (in July, approximately pH -0.1 – -0.2). However, anyway, the sensitivity of water-soluble metal concentrations was mostly dependent on changes in primary metal emissions and little affected by changes in aerosol acidity (0 – +2% for Fe, 0 – +0.5% for Cu and Zn). Therefore, it was suggested that primary emission control of metals is more important than gaseous pollutants in reducing water-soluble metal concentrations.</p>