Inequality of exposure to PM_2.5 and ozone among age groups and cities in Japan in 2030 and 2050

Global air pollution levels have increased in recent years, posing major health challenges. Although there is already evidence that residents of large cities and vulnerable groups such as the elderly and children are at higher risk of exposure to air pollution, there is a need to expand new perceptions in the face of a new phase of urbanization and demographic change in the future. In the face of population decline and the phenomena of aging and childlessness, it has become a pressing issue how Japan should respond to future national health risks associated with air pollution. However, no studies have yet comprehensively considered the long-term effects of emission reduction measures and future demographic changes on population exposure risks. Therefore, we developed methods to assess future population exposure risks under different combinations of emission reduction measures and demographic change scenarios. The results show that: electrification measures may not effectively reduce pollutants compared to end-of-pipe technologies and renewable energy. However, they offer long-term benefits in lowering ozone concentration and exposure risks. Over the next 30 years, urban populations under 15 years old show a negative correlation with PM_2.5 and an inverted U-shaped correlation with ozone. The elderly population's correlation with PM_2.5 weakens over time, with no clear correlation with ozone. The correlation between population size and PM_2.5 concentration varies for different classes of cities: positive for small cities, negative for medium cities, and negligible for large cities. No correlation was observed between ozone concentrations and urban population. Under equivalent abatement scenarios, the differences in exposure between the SSP scenarios are not large, but the SSP3 and SSP4 scenarios will bear a heavier healthcare burden and exposure inequity.