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Particles Without Borders
Aerosols have important and often adverse impacts on atmospheric composition, air quality, and climate. However, aerosols can be transported long distances, limiting the efficacy of local regulations. Yu et al. (p. 566) used satellite data to estimate how much of the aerosol load in the atmosphere above North America originates overseas. Approximately half of the dust and pollution over North America comes from Asia, Europe, Africa, and the Middle East. Asian dust is the largest fraction of this total. Furthermore, potential increases in dust emissions in response to climate change might overwhelm any reductions in pollution from emerging Asian economies.
Many types of aerosols have lifetimes long enough for their transcontinental transport, making them potentially important contributors to air quality and climate change in remote locations. We estimate that the mass of aerosols arriving at North American shores from overseas is comparable with the total mass of particulates emitted domestically. Curbing domestic emissions of particulates and precursor gases, therefore, is not sufficient to mitigate aerosol impacts in North America. The imported contribution is dominated by dust leaving Asia, not by combustion-generated particles. Thus, even a reduction of industrial emissions of the emerging economies of Asia could be overwhelmed by an increase of dust emissions due to changes in meteorological conditions and potential desertification.