Associations Between Historical Redlining and Present-Day Heat Vulnerability Housing and Land Cover Characteristics in Philadelphia, PA

Abstract

Historical, institutional racism within the housing market may have impacted present-day disparities in heat vulnerability. We quantified associations between historically redlined areas with present-day property and housing characteristics that may enhance heat vulnerability in Philadelphia, PA. We used color-coded Home Owners Loan Corporation (HOLC) maps and tax assessment data to randomly select 100 present-day (2018-2019) residential properties in each HOLC grade area (A = Best; B, C, and D = Most hazardous; N = 400 total). We conducted virtual inventories of the properties using aerial and streetview imagery for land cover and housing characteristics (dark roof color, flat roof shape, low or no mature tree canopy, no recently planted street trees) that may enhance heat vulnerability. We used modified Poisson regression models to estimate associations of HOLC grades with the property characteristics, unadjusted and adjusted for historical and contemporary measures of the neighborhood sociodemographic environment. Compared to grade A areas, higher proportions of properties in grade B, C, and D areas had dark roofs, low/no mature tree canopy, and no street trees. Adjusting for historical sociodemographics attenuated associations, with only associations with low or no tree canopy remaining elevated. Adjusting for present-day concentrated racial and socioeconomic deprivation did not substantially impact overall findings. In Philadelphia, PA, HOLC maps serve as spatial representations of present-day housing and land cover heat vulnerability characteristics. Further analyses incorporating longitudinal data on urban redevelopment, reinvestment, and neighborhood change are needed to more fully represent complex relationships among historical racism, residential segregation, and heat vulnerability.

Fig. 1

Crude risk ratio estimates of asssociation comparing the proportion of 100 residential properties in grade B, C, and D vs. grade A areas of Philadelphia, PA, with present-day heat vulnerability enhancing housing or land cover characteristics

Fig. 2

Risk ratio estimates of asssociation comparing proportion of 100 residential properties in grade B, C, and D vs. grade A areas of Philadelphia, PA, respectively, with present-day heat vulnerability enhancing housing or land cover characteristics, adjusted for neighborhood socioeconomic environment (measured using an index measure combining dimensions of housing environment, educational attainment, and unemployment), and for racialized segregation (measured using the Index of Concentration at the Extremes comparing proportion Black vs. proportion white) in the 1940s