In a recent study released by scholars and professors from the University of Southern California, it’s been found the impacts of air pollution are far more severe when combined with high heat. 

While both high heat and air pollution increase the risk of mortality individually, this recent study has found that while both are harmful on their own, they become significantly more deadly when combined. This is a particularly concerning issue because, in many areas, high heat leads to air pollution (through wildfires), meaning both are often present.

The research found that during the top 10% of hottest and most polluted days, deaths increased by around 4% (compared to days without extremes). On the top 1% of days, the mortality rate increased by 21% and by more than 33% for adults over 75. Individually, high temperatures and high air pollution increased the risk of death by 5% and 6%, respectively - far lower than the 21% found when the two were combined.

The reason for this increased mortality rate when both high heat and high air pollution are combined is due to oxidative stress, which is an imbalance in the production of reactive oxygen species and our body’s ability to remove them. ROS has been linked to a range of illnesses.

Typically antioxidants help balance ROS production. However, air pollution and heat can both disrupt the activity of antioxidants and lower it. This can lead to an imbalance causing potentially dangerous health implications. Older adults are more susceptible to these effects.

This finding is troubling because wildfires are becoming more common in many regions worldwide. Since wildfires are often caused by or occur during heat waves, we get the double impact of having both extreme temperatures and extreme particulate pollution.

If you would like to read more about the study on air pollution and high heat mortality rates, you can find a news article about the study here.