Abstract
In the Middle East, desert dust is assumed to dominate air pollution, being in permanent violation of public health guidelines. Here we present ship-borne measurements from around the Arabian Peninsula and modeling results to show that hazardous fine particulate matter is to a large extent of anthropogenic origin (>90%), and distinct from the less harmful, coarse desert dust particles. Conventionally, it was understood that desert dust dominates both the fine and coarse aerosol size fractions, which obscures the anthropogenic signal. We find that the annual excess mortality from the exposure to air pollution is 745 (514-1097) per 100,000 per year, similar to that of other leading health risk factors, like high cholesterol and tobacco smoking. Furthermore, anthropogenic pollution particles account for a major part (similar to 53%) of the visible aerosol optical depth. Therefore, in the Middle East anthropogenic air pollution is a leading health risk and an important climatic factor.