Cost-efficient strategy for reducing particulate matter 2.5 in the Tokyo Metropolitan area:An integrated approach with aerosol and economic models

Concentrations of particulate matter 2.5 (PM 2.5) are high in the Tokyo metropolitan area, even though concentrations of PM10 have dropped dramatically since the implementation of the NOx-PM Act. Currently, monitored concentration levels continue to exceed the designated ambient air quality standard set by the Japanese Ministry of the Environment. To our knowledge, no study has investigated a cost-efficient strategy to reduce PM 2.5 concentration levels in the Tokyo metropolitan area. This is the first study to examine a proper control strategy for Japan by developing an integrated model that includes both aerosol and economic models. The simulation results show that prefectures in the Tokyo metropolitan area cannot achieve the standards by relying on their own efforts to reduce PM 2.5. That is, prefectural governments in Tokyo metropolitan areas need to cooperate with prefectures outside of the area to improve their PM 2.5 concentration levels. Thus, we simulated policies under the assumption that emissions from other sources are reduced to evels such that the PM 2.5 concentration declines by approximately 18 µg/m3. We first simulated an efficient policy, i.e., the implementation of a pollution tax. We found that the total abatement cost to meet the air quality standard using the cost-efficient strategy is approximately 142.7 billion yen. We also simulated a policy in which we emphasize the equality of burden, i.e., each prefecture's government reduces emissions by the same proportion. In this scenario, the total cost of the strategy that maintains high equality among prefectures is approximately 416.3 billion yen. Thus, when authorities focus on other criteria such as equality, cost-efficiency deteriorates greatly. Therefore, to attain cleaner air, it is important that authorities make informed decisions when selecting a strategy.Length: 44 pages