Projection of combined vulnerability to air pollution and heat stress

Abstract

Background: Climate change caused by anthropogenic emissions is associated with increase in the frequency and intensity of climate extremes. Exposure to non-optimal temperature is related with 2-5 million deaths per year globally. In addition, air pollution has become a key concern for public health. Particulate matter less than 2.5 µm in diameter (PM2.5) is the largest environmental risk factor globally and is expected to worsen with projected increase in anthropogenic emissions. However, little is studied on vulnerability of combined exposure to these two environmental hazards under a changing climate. Methods: We use outputs from three CMIP6 models to project PM2.5 and Wet Bulb Global Temperature (WBGT) till end of the century under SSP126, 370 and 585 scenarios. We assessed the combined vulnerability of the exposed population, represented by vulnerability index(VI), to these two risk factors by factoring in the distribution of projected gross domestic product and education attainment (together termed socioeconomic indicator). Results: We find currently, 7% of the population (8% of the population above 65years) reside in regions with the highest vulnerability (mostly in Asia), which is projected to increase to 25% (and 32%) in 2050 under the SSP370 scenario. Globally, under all the three scenarios, percentage of population exposed to the most extreme VI was projected to increase till 2050, and decrease thereafter under SSP126, but under SSP585 and SSP370 scenarios, we found a significant increase in the population exposed to the most extreme VI. Conclusions: To the best of our knowledge, we present the first results on projections of combined vulnerability from exposure to two of the most hazardous environmental risk factors,by identifying their collocational hotspots across the globe. Our results may be used to assist decision making targeted towards averting exposure and excess deaths from heat stress and air pollution in the future decades.