The spatiotemporal evolution of population exposure to PM2.5 within the Beijing-Tianjin-Hebei urban agglomeration, China

A range of environmental constraints including air pollution are now of widespread concern in China because of rapid urbanization. Here we explore the spatiotemporal evolution of population exposure to particulate matter with diameter not greater than 2.5 μm (PM 2.5 ) within the Beijing-Tianjin-Hebei urban agglomeration (BTHU) at a fine spatial resolution based on grid data for population and PM 2.5 . Our analysis of available data leads to a number of conclusions, including that the majority of areas within the BTHU have been in an air condition with excessive PM 2.5 concentrations for a long time. The PM 2.5 concentrations within this agglomeration have fluctuated and increased over time while the spatial distribution of this variable is significantly agglomerated and regional, high values in the southeast but low values in the northwest. Second, analyses show that PM 2.5 concentrations are especially high within the BTHU, most notably in metropolitan areas including Beijing, Tianjin, and Shijiazhuang where population exposure risk is significant. Third, analyses show that the dominant role of PM 2.5 concentrations in changing exposure intensities over time has gradually become less significant while urbanization and population migration have gradually exerted a higher degree of influence. The outcomes of this study provide new insights on pollution prevention in urban agglomerations in the future.