Mexico study finds unexpectedly high heat risk for working-age adults
Could working-age adults be at higher risk of extreme heat than previously thought?
Scientific studies have long shown that extreme heat claims a disproportionate share of lives among the elderly and very young children. But a new report, based in 20 years of mortality and weather data from across Mexico, shows an unexpectedly high rate of deaths among 18 to 35 year olds, “the very group that one might expect to be most resistant to heat,” the study noted.
“One of our hypotheses is that’s a lot of occupational exposure to heat, in farming, hot factories, construction and so on,” said Jeffrey Shrader, an economist at Columbia University and a co-author of the report published Friday in the journal Science Advances.
Researchers and other heat experts said the findings could have serious implications for worker safety and economic productivity around the world, especially in regions where many people work outside or without access to cooling as global temperatures continue to set records.
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​“The big open question for me is how this applies to other locations in the world that are hotter, have younger populations and more occupational exposure to heat. We don’t have the rich data there we have in Mexico,” Shrader said in an interview with Climate Resilience for All.
In data-poor regions like Africa, in particular, “it’s a giant hole in our understanding of the likely implications of climate change,” said the economist, who works Columbia’s Center for Environmental Economics and Policy.
The study, based on Mexican data from 1998 to 2019, combined weather station readings with detailed records of every recorded death in Mexico over that period, looking for “excess deaths” - those above the normal death rate - during hot and humid periods.
Researchers found an average of 3,300 heat-related deaths each year in the nation, which currently has a population of close to 130 million people. The United States, by comparison, which has almost three times more people, had 2,325 official heat-related deaths recorded in 2023, though the actual rate is believed to be significantly higher.
Of Mexico’s heat deaths, 36 percent came among children under 5, who make up only 10 percent of the country’s population. But the second highest percentage - 32 percent - came among people 18 to 35 years old, who account for about 28 percent of the population.
People over 70, unusually, accounted for only 8 percent of deaths, and made up about 4 percent of Mexico’s population, a finding Shrader speculated might be related to higher access to air conditioning in urban parts of the middle income country.
He said a majority of working-age Mexicans who died were men - a finding paralleled by research in the United States - but that the gender divide in deaths was likely different in other countries and regions of the world, where gender roles, incomes and the kind of outside work done by women vary widely.
For instance, only about 15% of Mexico’s workers are employed in agriculture, the study noted - far fewer than in regions such as South Asia or Africa.
Looking at both gender and occupation data recorded in Mexican death documents, researchers are now trying to understand in more detail the unexpected data on working-age deaths as a result of heat, Shrader said.
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​​​​Laurence Kalkstein, a climate scientist carrying out research on extreme heat and health, said the study’s findings are particularly worrying given growing evidence that climate change is not only driving higher global temperatures but making nights particularly warmer, giving heat-affected workers little chance to recover.
“The difference between day and night temperatures is getting much smaller, and nighttimes are getting worse,” said Kalkstein, the science advisor to Climate Resilience for All. “This has a negative effect on human health outcomes.”
Researchers said the findings - based on data recorded before a recent series of record heat years globally - suggest countries and companies should rapidly adopt stronger regulations to protect workers from increasing heat and humidity, to protect lives and economic productivity.
President Joe Biden’s administration in the United States, for instance, in June proposed requiring employers to evaluate heat risks to workers and create plans to reduce them, such as by providing drinking water and rest breaks.
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“We need to build institutions and policy and just awareness” of growing heat threats, Shrader said. “Workers need to know and understand the symptoms of heat-related illness, and you have to do that before the heat arrives.”
With 2024 expected to be the hottest year in recorded history and the first to pass the 1.5 degree Celsius guardrail set in the Paris Agreement, heat deaths are growing, scientists say - and will surge further unless there is swift action to adapt to threats and slash use of climate-changing fossil fuels.