Effects of Increasing Aridity on Ambient Dust and Public Health in the U.S. Southwest Under Climate Change

The U.S. Southwest is projected to experience increasing aridity due to climate change. We quantify the resulting impacts on ambient dust levels and public health using methods consistent with the Environmental Protection Agency's Climate Change Impacts and Risk Analysis framework. We first demonstrate that U.S. Southwest fine (PM2.5) and coarse (PM2.5-10) dust levels are strongly sensitive to variability in the 2-month Standardized Precipitation-Evapotranspiration Index across southwestern North America. We then estimate potential changes in dust levels through 2099 by applying the observed sensitivities to downscaled meteorological output projected by six climate models following an intermediate (Representative Concentration Pathway 4.5, RCP4.5) and a high (RCP8.5) greenhouse gas concentration scenario. By 2080-2099 under RCP8.5 relative to 1986-2005 in the U.S. Southwest: (1) Fine dust levels could increase by 57%, and fine dust-attributable all-cause mortality and hospitalizations could increase by 230% and 360%, respectively; (2) coarse dust levels could increase by 38%, and coarse dust-attributable cardiovascular mortality and asthma emergency department visits could increase by 210% and 88%, respectively; (3) climate-driven changes in dust concentrations can account for 34-47% of these health impacts, with the rest due to increases in population and baseline incidence rates; and (4) economic damages of the health impacts could total $47 billion per year additional to the 1986-2005 value of $13 billion per year. Compared to national-scale climate impacts projected for other U.S. sectors using the Climate Change Impacts and Risk Analysis framework, dust-related mortality ranks fourth behind extreme temperature-related mortality, labor productivity decline, and coastal property loss. Plain Language Summary The southwestern United States is projected to experience severe, multidecadal droughts due to human-caused climate change. Mineral dust particles are a major contributor to air pollution in this region due to abundant deserts and drylands. To what extent could airborne dust levels increase as a result of the projected drought conditions? To answer this question, we first investigate the influence of drought conditions across southwestern North America on dust activity in recent years. We then use the observed relationships between dust and droughts to estimate future changes in dust levelsand the associated excess deaths and illnessesthrough the end of the century, using projections of temperature and precipitation from global climate models following two plausible (high and intermediate) greenhouse gas emissions scenarios. Under the high emissions scenario, premature mortality associated with dust exposure increases by 220% and hospitalization increases by 160% toward the end of this century, due to combined increases in population, disease rates, and dust levels. The annual economic damages of these health impacts are estimated to be $47 billion per year additional to the present-day value of $13 billion per year, making climate-driven changes in dust concentrations one of the costliest impacts projected for the United States so far.