Potential Impacts of Energy and Vehicle Transformation through 2050 on
the Atmospheric Environment of Japan: focus on PM2.5 Metals and Aerosol
Acidity inducing Respiratory Inflammation
Abstract
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.