Disparities in Heat Vulnerability in the United States

Exposure to extreme heat adversely affects a comprehensive spectrum of diseases, including  myocardial infarction (i.e., heart attack) ,  stroke ,  diabetes ,  kidney diseases ,  unintentional injuries , and  mental disorders , leading to increased mortality and morbidity burden.

The burden of  heat-related illness is inequitably distributed  due to disparities in heat exposure and access to individual- and community-level protective factors.

To better understand place-based and race/ethnicity-based disparities in heat vulnerability across the United States, an expansive and uniform Heat Vulnerability Index (HVI) was developed. The HVI aimed to quantify the various socioeconomic, demographic, biological, and exposure  determinants of heat vulnerability  into a single measure. The resulting HVI scores were assessed across historical and contemporary measures of residential disparity, and for the various race/ethnicity groups in the United States.

For a full description of the methodology, results, and discussion, see  Residential and Race/Ethnicity Disparities in Heat Vulnerability in the United States  (DOI: 10.1029/2022GH000695).

In the 1930s, the  Home Owners' Loan Corporation (HOLC)  created lending maps to assess a neighborhood's level of loan risk. Lending risk grades were given based on neighborhoods'  demographic composition , public utilities and physical building conditions.  HOLC grades  ranged from "A" to "D", where 'A' was "Best", 'B' was 'Desirable', 'C' was "Definitely Declining", and 'D' was "Hazardous". These HOLC maps were color coded, with the highest-risk areas colored red, giving rise to the term " redlining ".

HVI score increased by 0.8 points for each one-point increase in weighted HOLC grade.

Mean HVI scores were 17.56 for HOLC grade A census tracts, 18.61 for grade B, 19.45 for grade C, and 19.93 for grade D.

HVI scores were higher for each incrementally higher-risk HOLC grade, differing by 1.05 between ‘A’ and ‘B,’ by 0.84 between ‘B’ and ‘C,’ and by 0.48 between ‘C’ and ‘D’.

The White House Council on Environmental Quality's  Climate and Economic Justice Screening Tool (CEJST)  identifies "disadvantaged" communities based on various socioeconomic, environmental and health criteria. The CEJST provides a contemporary measure of residential disparity in the United States, though differing from HOLC grades by its inclusion of suburban and rural areas, as well as by its  equity promoting purpose .

Mean HVI score for "disadvantaged" census tracts was 2.45 points higher than for "non-disadvantaged" census tracts

Average HVI score was highest for "disadvantaged" census tracts with HOLC grade 'D' (20.4) and lowest for "non-disadvantaged" census tracts with HOLC grade 'A' (17.3).

The disproportionate exposure of communities of color to environmental hazards is a fundamental manifestation of environmental racism in the United States. Using data from the  American Community Survey (ACS) 5-Year Demographic and Housing Estimates from 2019 , heat vulnerability was analyzed for the various race/ethnicity groups in the United States.

The mean HVI score was highest for the non-Hispanic Black or African American race/ethnicity group at 18.51, followed by 18.19 for Hispanic or Latino of any race, 17.95 for Other races, 17.31 for Asian, 17.05 for American Indian or Alaskan Native, 17.05 for Multi-race, 16.76 for non-Hispanic White, and 16.76 for Native Hawaiian or Pacific Islander.

Non-white persons were overrepresented in the most heat-vulnerable census tracts