Historical Redlining Impacts Contemporary Environmental and Asthma-related Outcomes in Black Adults

Abstract

Rationale: Environmental threats and poorly controlled asthma disproportionately burden Black people. Some have attributed this to socioeconomic or biologic factors; however, racism, specifically historical redlining, a U.S. discriminatory mortgage lending practice in existence between the 1930s and the 1970s, may have actuated and then perpetuated poor asthma-related outcomes. Objectives: To link historical redlining (institutional racism) to contemporary environmental quality- and lung health-related racial inequity. Methods: Leveraging a broadly recruited asthma registry, we geocoded 1,034 registry participants from Pittsburgh/Allegheny County, Pennsylvania, to neighborhoods subjected to historical redlining, as defined by a 1930s Home Owners' Loan Corporation (HOLC) map. Individual-level clinical/physiologic data, residential air pollution, demographics, and socioeconomic factors provided detailed characterization. We determined the prevalence of uncontrolled and/or severe asthma and other asthma-related outcomes by HOLC (neighborhood) grade (A-D). We performed a stratified analysis by self-identified race to assess the distribution of environmental and asthma risk within each HOLC grade. Measurements and Main Results: The registry sampling overall reflected Allegheny County neighborhood populations. The emissions of carbon monoxide, filterable particulate matter <2.5 μm, sulfur dioxide, and volatile organic compounds increased across HOLC grades (all P ⩽ 0.004), with grade D neighborhoods encumbered by the highest levels. The persistent, dispersive socioenvironmental burden peripherally extending from grade D neighborhoods, including racialized access to healthy environments (structural racism), supported a long-term impact of historical/HOLC redlining. The worst asthma-related outcomes, including uncontrolled and/or severe asthma (P < 0.001; Z = 3.81), and evidence for delivery of suboptimal asthma care occurred among registry participants from grade D neighborhoods. Furthermore, elevated exposure to filterable particulate matter <2.5 μm, sulfur dioxide, and volatile organic compound emissions (all P < 0.050) and risk of uncontrolled and/or severe asthma (relative risk [95% confidence interval], 2.30 [1.19, 4.43]; P = 0.009) demonstrated inequitable distributions within grade D neighborhood boundaries, disproportionately burdening Black registry participants. Conclusions: The racist practice of historical/HOLC redlining profoundly contributes to long-term environmental and asthma-related inequities in Black adults. Acknowledging the role racism has in these outcomes should empower more specific and novel interventions targeted at reversing these structural issues.

Keywords: asthma; environment; pollution; racism; redlining.

Figure 1.

Historical/Home Owners’ Loan Corporation redlining map of Pittsburgh/Allegheny County, Pennsylvania, from 1935 (18). Reprinted by permission from Reference .

Figure 2.

Grade D neighborhoods contain the worst indicators of environmental quality, including the highest emissions of filterable particulate matter <2.5 μm (PM_2.5), sulfur dioxide (SO₂), volatile organic compounds (VOCs), and carbon monoxide (CO) over the study period (National Emissions Inventory year, circle = 2008; square = 2011; triangle = 2014; diamond = 2017) (A), as well as the highest railroad density and closest proximity to active waterways (B). P values were calculated by Cochran-Armitage test for trend or Spearman’s rho correlations with post hoc Dunn test.

Figure 3.

Comparison of area estimates of population size and percentage Black race based on asthma registry sampling (upper graph) and census sampling (lower graph) from Allegheny County neighborhoods subjected to historical/Home Owners’ Loan Corporation (HOLC) redlining demonstrates population-level similarities. The darker bars correspond to the left y-axis, and the lighter bars correspond to the right y-axis. In the lower graph, the lighter bars represent medians with interquartile ranges.

Figure 4.

Registry participants from grade D neighborhoods show the most evidence for uncontrolled and/or severe asthma (stacked bar graphs; black = no; colors = yes) (A), secondary clinical outcomes (stacked bar graphs; black = no; colors = yes) (B), current diabetes (general health indicator; stacked bar graphs; black = no; colors = yes) (C), spirometric measurements (Tukey plots) (D), and exploratory outcomes (stacked bar graphs; black = no; colors = yes) (E). P values were calculated by Cochran-Armitage test for trend or Spearman’s rho correlations. AIT = allergen immunotherapy.

Figure 5.

Forest plot (relative risk [RR], 95% confidence interval [CI]) of categorical asthma-related outcomes (A) and Tukey plots of daily short-acting β-agonist (SABA) use (B), FEV₁ (C), FVC (D), and FEV₁ reversibility (E) depicting the inequitable distribution of worsened asthma among Black and White registry participants with residence in grade D neighborhoods. The outcomes/measurements shown demonstrated significant, monotonic trends with grades A to D neighborhood directionality in the initial analyses. P values were calculated by RR (95% CI) and Mann-Whitney test (*P < 0.05; **P < 0.01; ***P < 0.001). AIT = allergen immunotherapy.