The legacy of the Home Owners' Loan Corporation and the political ecology of urban trees and air pollution in the United States.

This study examines the persistent impacts of historical racebased discriminatory housing policies on contemporary urban environments in the United States. Specifically, we examine the relationships between Home Owners' Loan Corporation (HOLC) grades assigned to neighborhoods in the 1930s and the current distribution of tree canopy and level of exposure to air pollution hazards. Our results indicate a clear gradient in tree canopy by HOLC grade, with better neighborhood grades associated with significantly higher percentage of tree canopy coverage. The pattern also exists for airborne carcinogens and respiratory hazards, with worse neighborhood grades associated with significantly higher hazards exposure. Our findings indicate that early 20th century discriminatory housing policies exert a contemporary influence on patterns of green space exposure in American cities, with implications for health and health inequities. Our findings suggest that, in order to achieve equitable access to the benefits of urban greenspace, we must acknowledge these historical influences and consider policies and practices that directly counter these influences, for example, through targeted greenspace development in areas historically identified as unfit for investment.