The changing role of dust PM2.5 and its impact on Africa's air quality and human health

Aerosol pollution events pose serious threats to humans and ecosystems. Emissions from dust, fossil fuels and wildfires have increased in many places since preindustrial times globally in both urban and rural regions. Aerosol particles in these emissions directly alter the radiative budget of the atmosphere and modify snow and ice surface albedos when deposited on the surface. Aerosols also indirectly impact climate by modifying cloud properties and changing land and ocean biogeochemistry. In addition to these impacts, aerosols from dust, fossil fuels and wildfires pose major air quality and health concerns. Near-surface particulate matter (PM ) from aerosols are associated with negative health impacts, including premature mortality. Most studies have focused on anthropogenic emissions and their impacts on air quality. Natural aerosols are much less studied for their airquality impacts, even though dust and wildfires have likely changed because of anthropogenic activities and such changes have the potential to impact global mortality.This study seeks to understand how emissions of dust and wildfireaerosols (often referred to as natural aerosols) have changed over the African continent since the preindustrial era to the present day and how much they may signifcantly change in the future under the Coupled ModelInter comparison Project (CMIP) scenarios. Some studies have shown that global dust mass loading have increased by 55% since preindustrial times, with North Africa and Asia as the main drivers, while the frequency and severity of wild res has decreased signifcantly in recent decades, at least globally. The indirect effects of these changes on human health have not yet been adequately estimated. We will specifically consider the impact of changing aerosols on premature deaths and outdoor air quality, but do not consider potentially important changes to indoor air quality.This current study will use the latest Community Earth System Model (CESM) Community Atmosphere Model version 6 (CAM6) to simulate estimated preindustrial, present, and future scenarios of aerosol PM concentrations, including changes in dust and wildfires and apply a long-term concentration response function from epidemiological studies to estimate which aerosol sources are most important for changes in African mortality due to exposure. This study will also assess mortality changes due to differences in PM exposure between people in rural and urban communities.