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Understanding Present-Day Racialized Inequities in Urban Heat: the Legacy of Historical Redlining and the Ongoing Process of Neighborhood Change in Philadelphia, PA
Journal article   Open access   Peer reviewed

Understanding Present-Day Racialized Inequities in Urban Heat: the Legacy of Historical Redlining and the Ongoing Process of Neighborhood Change in Philadelphia, PA

Janelle Renee Edwards, Anneclaire J De Roos, Irene E Headen, Loni Phillip Tabb, Chen C Kenyon, Sharrelle M Barber, Xiaojiang Li and Leah Schinasi
Journal of Racial and Ethnic Health Disparities, Forthcoming
20 Jul 2026
DOI: https://doi.org/10.1007/s40615-026-03086-9
PMID: 42474699
Featured in Collection :   Drexel's Newest Publications
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https://doi.org/10.1007/s40615-026-03086-9View
Published, Version of Record (VoR) Open Access via Drexel Libraries Read and Publish Program 2026 Open CC BY V4.0

Abstract

Redlining Urban heat Gentrification Built environment Racial inequities Environmental Education Social History Urban Economics Urban History
Background Spatial inequities in greenspace and built environment characteristics contribute to micro-heat islands, where certain urban neighborhoods experience higher temperatures. Historical redlining, introduced by the Home Owners’ Loan Corporation (HOLC) in 1938, systematically denied mortgage loans in racially marginalized neighborhoods. Prior research shows that historically redlined neighborhoods exhibit higher land surface temperatures, lower tree canopy cover, and fewer climate adaptations. However, few studies have examined whether the relationship between redlining and urban heat islands varies by neighborhood gentrification. We quantified associations between historical redlining and contemporary micro-heat islands in Philadelphia, PA, and assessed modification by gentrification. We hypothesized that higher HOLC redlining scores would be associated with higher temperatures, but that gentrified tracts would show weaker associations. Methods Micro-heat islands in 2018 were measured as census tract radiant temperature deviations from the city mean. HOLC grades were assigned to 2010 census tracts using areal weighting. Gentrification for years 1990–2000, 2000–2010, and 2010–2020, was categorized by census tracts that were “ineligible,” “eligible but did not gentrify,” “gentrified,” or “intensely gentrified” based on socio-demographic changes across three decades. Spatial regression models estimated associations between redlining and radiant temperature deviations, with stratified analyses for gentrification. Results Among 384 census tracts, 7.8% were non-redlined, 33.6% were moderately redlined, 44.0% were highly redlined, and 15.6% were ungraded. Highly redlined tracts were 0.60 ± 0.20 °F hotter than non-redlined tracts. Gentrification across three decades did not significantly modify associations. Conclusion Historical redlining modestly contributes to contemporary micro-heat islands in Philadelphia, independent of recent gentrification processes.

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