Race, historical redlining, and contemporary transportation noise disparities in the United States.

Background: Legacies of discriminatory federal housing practices-e.g., racialized property appraisal by the Home Owners' Loan Corporation (HOLC) and institutionalized redlining by the Federal Housing Administration-include disparate present-day environmental health outcomes. Noise pollution is health-harming, but just one study has associated contemporary noise with redlining in some HOLC-mapped United States (US) cities, while two national studies found associations between greater neighborhood-level people of color composition and increased noise. No studies have examined noise pollution exposure disparities across all HOLC-mapped cities or based on the intersection of race/ethnicity and redlining.

Objective: We address three objectives: (1) Assess disparities in fine-scale, per person transportation noise exposures by historical redlining status across all HOLC-mapped cities. (2) Quantify disparities in noise exposures by race/ethnicity nationwide. (3) Explore interactions between redlining status and race/ethnicity in noise exposures.

Methods: We analyzed three data sources: (1) complete digital HOLC maps of ordered investment risk grades (A-D), (2) fine-scale (30 m) estimates of transportation noise levels (year-2020), and (3) sociodemographic characteristics of individuals in year-2020 census blocks.

Results: We find an approximately monotonic association for excess transportation noise with HOLC grade, marked by a pronounced exposure increase (17.4 dBA or 3× loudness) between contemporary residents of grade A (highest-graded) and D (lowest-graded) neighborhoods, a pattern consistent across HOLC-mapped cities. People of color experience ~7 dBA greater (2× louder) excess transportation noise exposures than White people nationwide, a pattern consistent across US counties. Noise exposure disparities are larger by HOLC grade than by race/ethnicity. However, contemporary racial/ethnic noise exposure disparities persist within each HOLC grade at levels approximating those disparities existing in ungraded areas, indicating that historical redlining is one of multiple discriminatory practices shaping contemporary national soundscape injustices.

Significance: Findings illustrate how historical redlining and broader racialized inequalities in US society have shaped environmental injustices nationwide.

Impact statement: Excessive noise exposures harm human health. Communities of color in the United States experience disparate noise exposures, although previous studies are limited by reliance upon aggregated data. They are also disproportionately concentrated in historically redlined areas. Legacies of redlining include persistent racial and economic inequalities and environmental health disparities. Here, we conduct the first complete national examination of contemporary noise pollution disparities with respect to historical redlining and race/ethnicity. Findings advance understanding of the historical roots and enduring salience of race-based disparities in noise pollution exposures and can inform efforts to address these disparities through noise pollution policy-making.