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Why extreme temperatures raise the number of deaths in Latin American cities

The study estimated that just over 900,000 deaths between 2002 and 2015 could have been caused by extreme temperatures in large Latin American cities (EFE/Salas)
The study estimated that just over 900,000 deaths between 2002 and 2015 could have been caused by extreme temperatures in large Latin American cities (EFE/Salas)

The Emissions of greenhouse gases encourage, daily, that the global warming advance form accelerated. In addition, the advance of humanity towards natural habitats and the deforestation associated with this phenomenon, encourages the increase in temperature not to subside.

Now, in the cities, where a large part of the world’s population resides, the temperature can far exceed that registered in peri-urban areas. Thus, urban residents are especially exposed to the extreme heat or even extreme cold. Both phenomena have been related to excess morbidity and premature mortality, through a variety of physiological mechanisms.

A work carried out by an international team of researchers from the University of California and Drexel, which was published in nature medicine, estimated just over 900,000 deaths between 2002 and 2015 could have been caused by extreme temperatures in large Latin American cities.

How urban environments and policies affect the health of residents of the region's cities / (EFE/ Mariscal)
How urban environments and policies affect the health of residents of the region’s cities / (EFE/ Mariscal)

Since most of the studies that have been carried out on extreme temperatures that are related to mortality in major cities are in North America, Europe and China, this estimate was positioned as the most elaborate that has been obtained for Latin America.

“Latin America is just a part of the world that hasn’t received a lot of attention,” said Ana Diez Roux, an epidemiologist at Drexel University and co-author of the study. In addition, she indicated that this work has a much better representation of urban areas in Latin America than previous studies in the region.

To estimate how many people died from extreme heat or cold, researchers from the Urban Health in Latin America project assessed how urban environments and policies affect the health of residents of cities in the region, and analyzed data from mortality between 2002 and 2015 from the records of 326 cities in nine countries, with more than 100,000 inhabitants.

Although deaths on extremely cold days were higher than those on extremely hot days / (Photo: Victoria Valtierra / Cuartoscuro.com)
Although deaths on extremely cold days were higher than those on extremely hot days / (Photo: Victoria Valtierra / Cuartoscuro.com)

They also analyzed average daily temperatures and estimated the temperature range for each city, based on a public data set of atmospheric conditions. In order for a death to be linked to a temperature extreme, the death had to occur on either the 18 hottest days or the 18 coldest days each city experienced in a typical year.

To compare the risk of dying on very hot and cold days, the researchers used a statistical model in which they also contrasted warm days.

They discovered that in Latin American cities almost 6%, that is, almost 1 million, of all deaths between those years occurred on days of extreme heat and cold. At the same time they were able to create an interactive map with data from individual cities.

Nearly 1 million of all deaths analyzed by experts occurred on days of extreme heat and cold.
Nearly 1 million of all deaths analyzed by experts occurred on days of extreme heat and cold.

With 7.5% of deaths related to extreme heat and cold during the study period, the team found that older adults are especially vulnerable. Although the numbers vary from year to year, for example in 2015, more than 16,000 deaths among people aged 65 and over were attributed to extreme temperatures.

Population aging in Latin America is projected to increase faster than in other parts of the world: from 9% in 2020 to 19% in 2050, according to some estimates.

According to Josiah Kephart, an environmental epidemiologist at Drexel, who led the study, an aging population combined with Latin America’s high urbanization (more than 80% of the population lives in cities) and worsening impacts of climate change “make extreme temperatures are a truly alarming or dangerous danger for the cities of Latin America, particularly in the 21st century”.

In cities like Buenos Aires, Rio de Janeiro and Mérida (Colombia), heat is more lethal than cold / (AP Photo/Markus Schreiber)
In cities like Buenos Aires, Rio de Janeiro and Mérida (Colombia), heat is more lethal than cold / (AP Photo/Markus Schreiber)

Although deaths on extremely cold days (about 785,000) were much higher than those on extremely hot days (about 103,000), overall there were more days with intense cold, which could explain this difference.

But for some cities like Buenos Aires, Rio de Janeiro and Mérida (Colombia), the heat was more lethal than the cold. According to the scientists, when the temperature is very high, the probability of dying increases by 5.7% for every 1 °C increase in temperature. In Kephart’s words, “it is very alarming how quickly the risk of mortality increases at high temperatures, even with as little as 1°”.

For her part, Rosana Abrutzky, a sociologist at the Gino Germani Research Institute of the University of Buenos Aires, in statements to Science magazine, stated: “During the summer is when temperature changes have a stronger and more immediate impact. There is no quick way to escape.” In 2019, the expert led a study in which they determined that daily deaths increased by 43% during a heat wave in Buenos Aires, in December 2013.

The team discovered that older adults are especially vulnerable to extreme temperatures / (REUTERS / Agustín Marcarian)
The team discovered that older adults are especially vulnerable to extreme temperatures / (REUTERS / Agustín Marcarian)

Meanwhile, when evaluating this study, Abrutzky stated that “obtaining this type of comprehensive data is not easy.” “Although regional trends, such as the vulnerability of the elderly to extreme temperatures, are valuable, specific reasons behind the deaths cannot be established from this study,” he assessed, stating in that article: “Everything depends not only on the different climates, but also of the different characteristics of the population”.

The Drexel team is now working to unravel how certain inequities, such as housing conditions and access to green space, affect deaths that occur on hot or cold days.

In the coming decades, Latin America is projected to experience a substantial increase in the frequency of heat waves, so the team is also looking at temperature projections in these cities 50 years from now to estimate how these deaths will increase and what cities will be the most difficult.

Since 2018, researchers have partnered with local agencies in Buenos Aires and the city’s meteorological service to have an early warning system for extreme temperatures, allowing citizens and health services to be prepared to care for victims. .

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