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The inequality of heat stress.


Vista de edificios de ladrillo con diferentes estilos en una ciudad vista desde la cima de un edificio cercano.

This is a officially approved translation of an article from Eos.

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During each summer, record temperatures and heat domes envelop large areas of the United States, and individuals experience these extreme heat events differently. Those living in historically marginalized neighborhoods, where land use and discriminatory housing policies have led to segregation and racism, continue to face a higher risk from high temperatures and the health effects of heat stress.

A recent study published by One Earth revealed that in 481 American cities, heat stress disproportionately affects low-income and people of color. According to TC Chakraborty, a scientist at the Pacific Northwest National Laboratory and lead author of the study, “We found that the current disparity was consistent across cities: in over 90% of the cities we considered, we found inequalities in heat exposure related to both income and race.” This information can assist city leaders in implementing better measures to address heat disparities and protect populations at higher risk of heat exposure.

The danger of relentless heat

The urban heat islands, hot areas in the city where asphalt, high building density, and infrastructure cause temperatures to rise more than in surrounding areas, are home to millions of people who are unable to escape the effects of relentless summer heat.

Continuous exposure to excessive heat has an effect on cardiovascular, respiratory, and mental health.

“Las personas que viven en zonas urbanas suelen caminar para hacer sus tareas diarias. Una de las ventajas de vivir en una ciudad es que las cosas están cerca y puedes utilizar el transporte público, pero eso también significa que tienes que pasar más tiempo al aire libre”, dijo Neelima Tummala, médico y co-directora del Instituto de Salud Ambiental en la Universidad George Washington, quien no estuvo involucrada en el estudio.

In neighborhoods without parks or large trees, where asphalt and buildings absorb and radiate summer heat, residents may find it difficult to escape extreme temperatures both indoors and outdoors. This continuous exposure can be very dangerous. The body becomes unable to cool down properly through sweating. Chronic exposure to excessive heat has an impact on cardiovascular, respiratory, and mental health, Tummala explained. “Prolonged exposure to high nighttime temperatures can affect sleep quality and mental and cardiac health,” he said. “You are constantly at a high temperature that your body has to deal with.”

Mapeando la disparidad de calor

Previous studies on urban heat have used satellite data to estimate land surface temperatures. However, Chackraborty and colleagues evaluated heat stress using the heat index from the US National Weather Service and the humidex index from the Canadian National Weather Service, combining air temperature and humidity to better describe how heat feels. Using models that combine these variables was a more accurate way to categorize heat stress in American cities between 2014 and 2018.

The correlation between mapped heat indices and census data revealed that low-income neighborhoods and residents of color experienced higher temperatures and humidity, which together amplify heat stress. Census tracts with higher incomes experienced less heat stress. Heat stress was also generally higher in areas with a higher percentage of Black and African American residents.

Mapa de polígonos con colores del arcoiris.

Baltimore census tracts shaded by heat index and percentage of black residents. A comparison shows that in areas with a higher proportion of black residents, there is greater heat stress. Credit: TC Chakraborty/PNNL

Un mapa de aspecto antiguo con polígonos rojos, verdes, amarillos y azules sobrepuestos sobre cajas negras más pequenas.

A 1938 map of Brooklyn, New York from the Home Owners’ Loan Corporation displays neighborhoods color-coded based on loan value. The areas in red (marginalized neighborhoods) indicate areas where banks and other lenders generally deemed residents unworthy of inclusion in loan and homeownership programs. These marginalized neighborhoods had a disproportionate number of black residents. Credit: Home Owners’ Loan Corporation, Public Domain.

The researchers compared these findings with historical data from 177 cities to further observe the income and race disparity over time. In the 1930s, the United States government classified neighborhoods based on their investment capacity. Many of the neighborhoods that housed poor and minority populations, particularly black and African American residents, were considered riskier investments and therefore received less funding for development and housing programs. Today, these marginalized neighborhoods suffer from much worse environmental conditions than other parts of their respective cities. They have less tree coverage and experience higher surface temperatures than neighborhoods that were not originally marginalized.

Chakraborty reported that the disparities were pronounced. Marginalized neighborhoods, often labeled with a “D” by lenders, had a higher heat index compared to those labeled with an “A”. “This finding was very intriguing – that this level of inequality and segregation correlated so strongly with levels of heat disparity,” they said.

Protecting the most vulnerable individuals.

“Studies such as this, which aim to further understand existing disparities in heat exposure, are crucial in identifying which communities are most at risk for experiencing environmental changes related to climate change, such as increasing levels of extreme heat,” stated Tummala. Public health measures and mitigation strategies are needed to protect citizens who are at a higher risk for heat-related illnesses, especially as temperatures continue to rise.

Areas with fewer trees on the streets and less access to green spaces – That is where we begin to see the effects of disinvestment and institutional racism coming into play.

Areas with fewer trees on the streets and less access to green spaces are where the effects of disinvestment and institutional racism are most visible, according to Lara Whitely Binder, manager of the climate preparedness program in King County, Washington. She was not involved in the research.

As the climate continues to change and evolve, cities must now prepare for hotter summers and more frequent deadly heat waves by utilizing various methods both indoors and outdoors. “It’s not just about understanding where it’s hot, but also understanding the socioeconomic factors for the inhabitants of those areas,” stated Whitely Binder. “We can start by analyzing the heat islands and using that information to inform the policy decisions we make.”

– Author of science, Rebecca Owen (@beccapox)

Nel Rodriguez Sepulveda’s translation was made possible through a partnership with Planeteando.

This article is part of our ENGAGE resource for teachers looking for science news to use in their lessons. Check out all of our ENGAGE articles and let other educators know how you incorporated this article into a classroom activity by leaving a comment below.

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