Ambient nitrogen dioxide (NO2) pollution poses significant effects on human health, especially in urban areas, and is a tracer for urban activity. As urban activity ground to halt in early 2020 due to the COVID-19 crisis, levels of NO2 plummeted in cities around the globe. Here, we provide two vignettes to show how new insights gained from understanding changes in NO2 pollution during this natural experiment can inform long-term transportation policy and protect public health. The first vignette examines disparities in NO2 pollution among racial and ethnic demographic subgroups in the United States (U.S.), which have persisted for decades even with overall reductions in NO2. To investigate these disparities, we use satellite-derived measurements of NO2 from the TROPospheric Monitoring Instrument for a baseline (spring 2019) and lockdown (spring 2020) period together with demographic data from the U.S. Census Bureau. In the second vignette, we demonstrate how diesel passenger vehicles, which produce considerably more NOx emissions compared with gasoline engines, contribute to urban NO2 pollution. The lessons learned from both vignettes during this natural experiment point to the dirty reality of combustion-based transportation and provide further motivation to address NO2 pollution stemming from the transportation sector and the associated public health damages. Electrifying passenger and heavy-duty vehicles and promoting congestion pricing, low emissions zones, and active transportation (e.g., cycling, walking) are examples of actions that could broadly lower NO2 levels and advance environmental justice by reducing NO2 disparities.
Dr. Gaige Kerr is currently a postdoctoral fellow at George Washington University, working with Susan Anenberg in the Department of Engineering and Occupational Health. He received his bachelor's degree in Atmospheric Science from Cornell University, and his PhD in Earth & Planetary Sciences from Johns Hopkins University. During his graduate work, he was a fellow of the NSF Water, Climate and Health Integrative Graduate Education and Research Traineeship (IGERT) program. He currently serves as an Air Quality Fellow for the US State Department's Greening Diplomacy Initiative. His research interests include chemical transport models and the disparities in O3 and NO2 pollution.
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