A ranking of environmental indicators among historically redlined neighborhoods in Detroit, Michigan, USA

Background and Aim: The Home Owners’ Loan Corporation (HOLC) in the 1930s drew maps of cities across the US that labeled neighborhoods by mortgage risk. This historical practice, commonly called "redlining”, labeled neighborhoods deemed "hazardous” with the color red. This policy denied mortgage loans to minority persons seeking homes in White/affluent neighborhoods, segregating these areas by race and ethnicity. This legacy of de jure segregation shaped neighborhoods today and influenced their environmental exposures, a form of environmental racism. The aim of this study was to identify the most pervasive exposures associated with redlining. Methods: The Detroit shapefile defined by the HOLC and digitized by the Mapping Inequality project overlaid onto the Environmental Protection Agency’s EJSCREEN and the Department of Transportation National Transportation Noise Map was used to determine modern environmental exposures and transportation noise within historical boundaries. Differences in demographic and environmental hazards between redlined (red or D grade) and non-redlined neighborhoods (grades A, B, and C) were assessed using hypothesis testing and a boosted classification tree algorithm. Results: Historically redlined Detroit neighborhoods experience significantly higher environmental hazards than non-redlined neighborhoods from diesel particulate matter (PM), traffic volumes, hazardous road noise, cancer risk from air pollution, and are closer to hazardous waste and Risk Management Plan (RMP) sites. With all factors taken together, boosted regression trees indicated the most pervasive environmental exposures among redlined neighborhoods in Detroit are the proximity to RMP sites, hazardous road noise, diesel PM, and cancer risk from air pollution. Conclusions: Institutional segregation via historical redlining is associated with environmental injustices in Detroit today. Policies targeting transportation-related air and noise pollution, particularly from sources of diesel exhaust, in redlined neighborhoods may ameliorate some of the disproportionate impacts of historical redlining, providing a proof-of-concept to apply to other redlined cities. Keywords: environmental justice; redlining; EJSCREEN; noise, Detroit