Outdoor air pollution contributes to millions of deaths worldwide yet air pollution has differential exposures across racial/ethnic groups and socioeconomic status. While green infrastructure has the potential to decrease air pollution and provide other benefits to human health, vegetation alone cannot resolve health disparities related to air pollution injustice. We discuss how unequal access to green infrastructure can limit air quality improvements for marginalized communities and provide strategies to move forward.Outdoor air pollution is a leading contributor to the environmental burden of disease and linked to over four million deaths worldwide each year 1 . The World Health Organization (WHO) reports that almost half of cities with more than 100,000 residents, and most (97%) cities in lowand middle-income countries of that size, do not meet WHO air quality guidelines 2 . From 1960 to 2009, global levels of fine particulate matter increased by 38% leading to a greater health burden from polluted air 3 . Even in the midst of the current pandemic, evidence of higher COVID-19 deaths among people with pre-existing conditions was linked to elevated air pollution exposure 4,5 and/or residing in areas with historically higher levels of air pollution 6 . Exposure to air pollution, however, is not evenly distributed, especially within cities. Many studies document differential exposure to air pollution by race/ethnicity 7,8 and socio-economic status 8-10 in cities across the world. Neighborhoods segregated by race and class often have less political and economic power, and are often neglected by government institutions such that they receive fewer resources compared to privileged communities 11 . This predicament results in disproportionate and overlapping exposures to environmental burdens 11 . Through the years, some approaches to decrease outdoor pollution include regulation of air pollution sources, emission controls on personal vehicles, and-more recently-the expansion of green infrastructure. The expansion of green infrastructure can mitigate urban air pollution to some extent. Yet, urban greening cannot compensate for systemic injustices that lead to disproportionate burdens in environmental health, and therefore, green infrastructure investments need to be balanced with other efforts to ameliorate air pollution injustices.
Green infrastructure for air pollution mitigationMany cities have explored the potential of green infrastructure to mitigate urban air pollution and studies estimate that the value of this ecosystem service is worth about $3.8 billion dollars in the United States alone 12 . The definition of green infrastructure varies by discipline and scope. In this article, we focus on the broader role of all urban vegetation that provides ecosystem services via the mitigation of air pollution. For example, roadside green barriers can block the movement