Oct 07, 2023 14:00:00

Extreme heat and air pollution are dangerous on their own, but when combined they increase the risk of death even more.

It has been reported that July 2023 was the ``

hottest month on record '' worldwide, and there are concerns that temperatures will continue to rise due to climate change. Researchers at the University of Southern California warn that when such temperature rises are combined with air pollution such as PM2.5 (fine particulate matter) , the risk of death will further increase.

The Effects of Coexposure to Extremes of Heat and Particulate Air Pollution on Mortality in California: Implications for Climate Change | American Journal of Respiratory and Critical Care Medicine
https://www.atsjournals.org/doi/10.1164/rccm.202204-0657OC

Extreme heat and air pollution can be deadly, with the health risk together worse than either alone
https://theconversation.com/extreme-heat-and-air-pollution-can-be-deadly-with-the-health-risk-together-worse-than-either-alone-187422

Extreme heat and air pollution alone are known to have serious negative effects on the human body and increase the risk of death. Therefore, a research team led by Erica Garcia , an assistant professor in the School of Public Health Sciences at the University of Southern California, analyzed data on the number of deaths from 2014 to 2020 in California, which is prone to air pollution caused by heat waves and wildfires. I analyzed it.

As a result of analyzing the data on the total number of deaths of 1.5 million people and the weather conditions on the day the deaths occurred, it was found that the number of deaths increases on ``hot days'' and ``days with high PM2.5 concentrations''. It turns out that. They found that days when extreme heat and air pollution occurred together resulted in far more deaths than days when each occurred separately.

Looking at the bar graph below, you can see that the risk of death increased by 5% on days when the light blue concentration of PM2.5 was extremely high, and the risk of death increased by 6% on days when it was extremely hot in red. Masu. Furthermore, it can be seen that the risk of death increased by 21% on purple days when both extreme air pollution and intense heat occurred. This effect is particularly pronounced among the elderly, with the risk of death for people over 75 increasing by more than 33% when both air pollution and extreme heat occur.

The research team has proposed several hypotheses as to why the combination of extreme heat and air pollution increases the risk of death. The first is

oxidative stress , which is caused by an imbalance between the production and decomposition of active oxygen . Air pollution and intense heat cause excessive production of active oxygen and reduce the activity of antioxidants, making oxidative stress worse.

The second possibility is that sleep deprivation due to the intense heat is having an effect. This study showed that the negative effects are greatest when high nighttime temperatures and air pollution occur together. This suggests that high nighttime temperatures may disrupt sleep, which in combination with disturbances in body temperature regulation, may make people more susceptible to the effects of air pollution.

Additionally, older people in particular often have chronic health problems such as heart disease, high blood pressure, diabetes, and lung disease, and body temperature regulation disorders are more likely to occur as we age. Therefore, the combination of extreme heat and air pollution may be more damaging to older people, Garcia and colleagues say.

Although this study focused on California in the United States, climate change is increasing temperatures in many countries and regions around the world, and is also affecting outdoor PM2.5 levels. The problem is not limited to California.

The research team said people should take steps to reduce the negative effects of extreme heat and air pollution. He argued that installing air conditioners in shopping malls and public places, and turning on air conditioners at home on hot days can reduce the damage caused by extreme heat, and that installing air purifiers can also be helpful.