The health impacts of aerosol-planetary boundary layer interactions on respiratory and circulatory mortality

Aerosols could affect the thermal radiation process of planetary boundary layer (PBL), thus changing its thermodynamic and circulation structure and further triggering changes in aerosol concentrations. However, previous studies mostly focused on the direct health impacts of aerosols and meteorological conditions in the boundary layer and little is known about the health impacts associated with aerosol-PBL interactions. We quantitatively estimate the impacts of PM2.5 and air temperature on mortality caused by aerosol-PBL interactions. Utilizing the WRF-Chem model, we conducted a one-month numerical simulation during December 2015 in the Beijing-Tianjin-Hebei (BTH) region, one of the most polluted regions with the highest population density in China. We simulated PM2.5 concentrations and air temperature under two scenarios: with/without considering the aerosol-PBL interactions. Based on the simulation data, we adopted the distributed lag non-linear model (DLNM) to establish the exposure-response associations of PM2.5 and temperature with mortality and calculated the population-weighted exposure levels of PM2.5 and temperature. During December 2015 in the BTH region, the additional PM2.5-related and temperature-related deaths were 312 due to respiratory and circulatory disease. Without considering the aerosol-PBL interactions, the population-weighted average levels of both PM2.5 and temperature increased compared with the average levels. However, after considering the aerosol-PBL interactions, the population-weighted average temperature was decreased, while the population-weighted average PM2.5 concentration was increased. In the BTH region, more people lived in areas with high PM2.5 concentrations where have strong aerosol-PBL interactions. The aerosol-PBL interactions could intensify the adverse health impacts of temperature and PM2.5, which should not be neglected when to assess the health effects of aerosol and meteorological conditions.