The heat waves and the atmospheric pollution they are harmful, even deadly, and both are expected to increase in frequency due to climate change. A team of researchers from the University of Southern California (United States) has helped shed light on health risks by evaluating six years of data on air quality, temperature, and death certificates.
In their work, published in the scientific journal ‘American Journal of Respiratory and Critical Care Medicine’, have shown that, compared to days without extreme conditions, days of extreme heat entailed a 6.1 percent increased risk of death. On days of extreme air pollution, deaths were 5 percent more likely. But on days of extreme heat and air pollution, deaths were 21 percent more likely, a synergistic effect that nearly doubles the impact of individual exposures combined.
“We found that the effect of exposure to extreme temperatures and extreme pollution on mortality is greater than the sum of their individual effects,” explains Dr. Mostafijur Rahmanlead author of the study.
“We found that the effect of exposure to extreme temperatures and extreme pollution on mortality is greater than the sum of their individual effects”
Previous studies have examined how extreme heat and air pollution separately affect mortality risk, and how each varies with the other. But this study is the first to use a new approach to study what happens when extreme heat and air pollution coincide.
In addition to overall mortality, this study also examined deaths from conditions cardiovascular Y respiratory. On days of extreme exposure, people over the age of 75 were most at risk. The findings could ultimately help people, communities and health systems prepare for extreme weather and minimize potential damage.
“Understanding the risks associated with these exposures is really important, because we know that they will increase with climate change in many different parts of the United States and the world,” he said. Erika Garciaalso lead author of the study.
The forest firesfor example, which are projected to rise as much as 50 percent by the end of the century, often involve extreme heat and pollution that lasts for days or weeks.
Garcia, Rahman, and their colleagues studied all deaths that occurred in California between 2014 and 2019 (a total of more than 1.5 million) using the data from the death certificates of the Department of Public Health Of California. They also obtained data on air temperature and levels of fine particulate matter (PM2.5), a tiny particulate pollution in the air that is known to cause health problems.
They then linked the deaths to local environmental conditions. depending on the person’s address to understand the effects of exposure. Using data on temperature and air pollution levels, the researchers classified each day into one of four categories: no extreme exposure, extreme heat only, extreme air pollution only, or extreme heat and air pollution.
On days when both heat and air pollution reach extreme levels, people may experience increased inflammation and oxidative stress, as well as problems regulating internal body temperature
On days of extreme heat and air pollution, the overall mortality risk increased by 21 percent. The risk of death from cardiovascular problems increased by 29.9 percent and the risk of death from respiratory problems 38 percent.
Although the researchers did not study specific causes of death, these problems often include conditions such as heart failure and the pneumonia. On days when both heat and air pollution reach extreme levels, people may have more inflammation and oxidative stress, as well as problems regulating their internal body temperature, Rahman says.
Older adults faced a significantly higher risk, with a 36.2 percent increased mortality risk for those older than 75 yearscompared to an 8.5 percent increase in mortality risk for people age 75 and younger when exposed to both extreme heat and pollution.
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