Historical neighbourhood redlining and contemporary environmental racism

To stabilise the housing market during the great depression, the government-sanctioned Home Owners’ Loan Corporation (HOLC) created colour-coded maps of nearly 200 United States cities according to lending risk. These maps were largely driven by racial segregation, with the worst graded neighbourhoods coloured in red, later termed redlined neighbourhoods. We sought to investigate the association between historical redlining, and trends in environmental disparities across the US over the past few decades. We characterised environmental exposures including air pollutants (e.g. NO₂ and fine particulate matter), vegetation, noise, and light at night, proximity hazardous emission sources (e.g. hazardous water facilities, wastewater discharge indicator) and other environmental and social indicators harnessed from various sources across HOLC graded neighbourhoods and extrapolated census tracts (A [lowest risk neighbourhoods] to D [highest risk neighbourhoods]). Lower graded areas (C and D) had consistently higher exposures to worse environmental factors. Additionally, there were consistent relative disparities in the exposures to PM2.5 (1981–2018) and NO₂ (2005–2019), without significant improvement in the gap compared with HOLC grade A neighbourhoods. Our findings illustrate that historical redlining, a form of residential segregation largely based on racial discrimination is associated with environmental injustice over the past 2–4 decades.