Clean air for some: How satellite-measured NO2 reveals sources and impacts of and equitable solutions to long-standing disparities

The pollutant nitrogen dioxide (NO₂), a tracer for fossil fuel combustion from transportation and industry and commonplace in urban areas, is associated with a growing number of adverse health outcomes. Many of its sources as well as NO₂ concentrations themselves are often highest within marginalized and minoritized communities in the United States (U.S.) and throughout the world. The short lifetime and spectral properties of NO₂ allow for high-fidelity, space-based measurements, and the increasingly high spatial resolution and complete geographic coverage of satellite-derived NO₂ provided by current instruments, such as the TROPOsphere Monitoring Instrument (TROPOMI), attest to recent advances in our ability to surveil NO₂ from space. 

Here, we highlight how remotely-sensed observations of NO₂ or estimates of NO₂ that incorporate satellite data can reveal the extent, sources, and impacts of these disparities. To these points, we show how communities of color in the U.S. face significantly higher levels of NO₂ by a factor of ~2.1 than majority white, non-Hispanic communities and trace back this disproportionate exposure to particular NO₂ sources such as light- and heavy-duty transportation and the rapidly-growing e-commerce and warehousing industry. These inequitable exposures are associated with a large burden of disease—including an estimated 115,000 new cases of pediatric asthma annually in the U.S.—disproportionately borne by marginalized communities. Despite the concerted efforts of policymakers to reduce these health disparities, we find that the magnitude of disparities has grown in recent years. 

We discuss how new geostationary instruments with complete daytime coverage, such as Tropospheric Emissions: Monitoring of Pollution (TEMPO), may reveal different disparities in NO₂ exposure compared with polar-orbiting instruments such as TROPOMI that provide only a single early afternoon snapshot of NO₂ levels. We also broaden our exploration of urban air quality, health, and equity to the global scale and discuss how global marginalized communities may face similar, disproportionate exposure to this pollutant as they do within the U.S. Overall, these satellite-enabled insights can spur and inform policies that would not only reduce urban pollution but could have outsized benefits for overburdened communities, and we discuss how actions such as adopting more stringent air quality or engine standards can reduce NO₂ emissions and targeted cleanup of emission sources within these overburdened communities could reduce these long-standing disparities.