Why overheating plus pollution is a deadly combination

BILLIONClimate-related health risks are converging with alarming frequency: record high temperatures and air pollution from things like car exhaust and wildfire smoke. Separately, these conditions can make people very sick and aggravate existing health problems. But what happens when they coincide?

Recently, researchers at the University of Southern California set out to answer that question. Their results, based on mortality data from California from 2014 to 2019 and published in late June in American Journal of Respiratory and Critical Care Medicineindicated that the combined mortality risk of extreme heat and thick pollution was significantly higher than the sum of their individual effects.

As the chart below shows, a person’s mortality rate increases by 6.1% on days with extreme temperatures and 5% on days with severe pollution compared to days that are not too extreme. But on days with both extreme conditions, the risk of death increased by 21%.

Like vehicle emissions, wildfires release PM2.5, a very fine particulate matter less than 2.5 micrometers in size. (For comparison, the diameter of a hair strand is 30 times larger than the largest of these fine particles.) While the USC researchers analyzed PM2.5 pollution levels regardless of its source. , they found that the days of extreme pollution occurred to coincide with the California wildfire event. “When you look at our top 1% of the most polluted days, the concentration of pollution is actually very, very high… four times higher. [than normal],” said Md Mostafijur Rahman, a postdoctoral researcher in the Department of Population and Public Health Sciences at USC’s Keck School of Medicine and one of the study’s co-authors. “That was certainly driven by another source. It’s not like the usual source from traffic”.

Francesca Dominici, a professor of biostatistics at Harvard’s TH Chan School of Public Health, who has studied these toxic things. However, while PM2.5 is known to cause cardiovascular disease, respiratory problems and cancer, some of its forms are worse than others. “The fine particulate matter in wildfires tends to be even more toxic,” says Dominici. “We have buildings on fire, we have cars on fire, we have all sorts of things on fire. There is currently research showing that the chemical composition is even more dangerous.”

Moreover, when the small particles response to high temperature and sunlightthey can depleting the ozone layer in the ground layer—Smog — can be activated respiratory effects like an asthma attack. One research from Washington State University published earlier this year found that periods of PM2.5 and high ozone have “become significantly more frequent and persistent” across the western United States over the past 20 years, due to ” Simultaneously, widespread hot weather and forest fire activity occurred. A notable 12-day period in summer 2020 includes an August day where nearly 70% of that region – including 43 million people – was affected by harmful levels of air pollution from fire activity unprecedented forest at that time.

Don’t be confused. The American West is certainly not the only place grappling with the dual threat of heat and pollution. Extreme temperatures have touched nearly every part of the country this summer, and fires are raging through forests in the far north. like Alaska. Eastern Australia, known for its hot summers and dangerous bushfires, has had a brutal 2019-2020 season in history. Russia has experienced one of the Largest recorded forest fire last year in Siberia in hot and dry conditions. In Europe, the hells ravaged Turkey and Greece last year; this year they are sweeping over Spain and Francefueled by heat waves that broke both records How is the beginning of the year? they showed up and How high is mercury?.

The confluence of these events during the summer months, when temperatures rise to unbearably high that our bodies can’t handleare becoming more common: Heatwaves make arid regions even drier — and ideal for wildfires that spew smoke far and wide. Erika Garcia, an assistant professor in the Department of Population and Public Health Sciences at USC’s Keck School of Medicine and co-author of the study with Rahman, cautions that although wildfires occur in waves, the effects do Theirs can last for weeks.

“As climate change progresses, we will continue to experience more frequent, more intense and longer-lasting extreme heat events and extreme particulate pollution events,” she said. “We really need better intervention and adaptation policies to save lives in these days of extreme pollution and heat.”

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