Document Type

Article

Publication Date

9-23-2025

Abstract

Given the recent reduction in the U.S. National Ambient Air Quality Standard (NAAQS) for annual PM2.5from 12 to 9 μg m–3, the contribution of exceptional, though natural, particulate transport events has assumed greater regulatory relevance. This study examines the evolution of a June 2022 trans-Atlantic Saharan dust outbreak and contextualizes its impact on the 2023 PM2.5design values (DVs) for continental U.S. air quality monitors. The results demonstrate that the intrusion of Saharan dust yielded mean 24 h PM2.5values > 35 μg m–3for multiple days across the Central U.S. and single-handedly elevated the 2022 mean annual PM2.5by > 0.5 μg m–3for some Gulf Coast communities. Moreover, the Saharan dust outbreak led to ∼0.1 μg m–3increases in the 2023 PM2.5DVs for approximately 20 monitoring sites in Texas and Louisiana, and in the case of Port Allen, La., and at least two other monitors, the Saharan dust pushed the DV above the 9 μg m–3NAAQS. As this June 2022 episode illustrates, seemingly rare atmospheric phenomena are positioned to play disproportionately large regulatory roles, given the tighter air policy landscape.

Publication Source (Journal or Book title)

Environmental Science and Technology

First Page

19745

Last Page

19754

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