Not All Neighborhoods Are Affected Equally by Heat Waves, New Data Shows

As the Earth’s climate warms, abnormal heat waves remain an increasingly dire health hazard. But not all neighborhoods are affected equally: redlining, housing discrimination, and inequitable public infrastructure have contributed to disparities in health outcomes from heat.

Policymakers and government officials now have a powerful tool to address these issues.

A team of researchers at Yale School of Public Health has developed a metric to gauge heat vulnerability at the census-tract level and created a color-coded interactive map for public use.

The innovative visual aid, presented in refined detail, can help officials identify areas that may need more public health and policy interventions to combat the adverse effects of heat stress, said Kai Chen, assistant professor of epidemiology (environmental health) and director of research for the Yale Center on Climate Change and Health.

“We want this tool to be used by the public so that we can raise awareness of how vulnerable their communities are and help them take appropriate action,” Chen said. “But also, we want this to be used by policymakers so that they can see the distribution within their state, or even nationally, so they can have certain communities in mind when they implement climate adaptation policies.”

The team’s index-based analysis reveals new insights into the nature of heat-related health disparities, including its association with race. According to the analysis, which spanned more than 55,000 census tracts across the continental United States, non-white people of color composed more than three-quarters of the population of the nation’s most vulnerable tracts. Meanwhile, in the least vulnerable areas, only about one-quarter of the population were people of color.

The Heat Vulnerability Index combines a variety of data points like race and ethnicity, diabetes prevalence, building density, evidence of historic redlining, and air temperature anomalies into a single score, from 10 to 26.

The study was supported by a seed grant from the Yale Planetary Solutions Project and the High Tide Foundation.

The index draws a clear correlation between historically redlined neighborhoods and heat vulnerability today. Redlining was a discriminatory practice initially employed by the federal government during the 1930s when it attempted to rank the risk of issuing government-insured mortgages to homeowners. Federal officials used color-coded maps to classify perceived investment risk, with the riskiest areas – neighborhoods where property values were most likely to go down – marked in red. Most of the redlined areas were neighborhoods where Black residents lived, making it difficult for Black residents to access homeownership and government-backed lending programs. Efforts to address redlining culminated in the Fair Housing Act of 1968, which prohibits housing discrimination.