Texas study reveals heat waves can cause more polluted air

Heat waves are becoming more and more common, severe and durable. These prolonged periods of hot weather are particularly dangerous in already hot places like Texas. In 2023, more than 300 people in Texas died of heat, according to Texas Department of State Health Services, the most since the State began to follow these deaths in 1989. Researchers found that not only temperatures make heat waves dangerous but also the increase in the heat of air pollutants.

Bianca Pamela Aridjis-Olivos, a graduate student in aerosol and atmospheric chemistry of the Texas A&M University, presented the results of her team at the autumn meeting of the American Chemical Society (ACS Fall 2025) from August 17 to 21.

In 2023, while intense heat raged across Texas, Aridjis-Olivos began to work with the mentor of the Faculty Renyi Zhang and his colleagues from the Center for Atmospheric Chemistry and the Environment (CACE) in Texas A&M. Since heat waves should make the United States worse in the coming years, the CACE team was motivated to determine the impact of heat extremely impacting atmospheric chemistry and air quality.

The researchers designed and conducted a pilot study of atmospheric chemistry during the heat wave of Texas August 2024. They collected air samples throughout the day and the night from August 5 to September 3 on the university campus at College Station, TX, where temperatures varied from 90 to 106 degrees Fahrenheit (32 to 41 degrees Celsius). In addition, air sampling occurred when there were no nearby forest fires, insulating the effects of the heat wave itself without the influence of forest smoke on air quality.

The researchers analyzed air samples for public health pollutants, including nitrogen oxides, ozone, volatile organic compounds (VOCs) and nanoparticles. For this work, they used a series of sensitive instruments to detect traces gases and measure the properties of aerosols, including a mass spectrometer of proton reaction time (PTR-TOF-4000).

“You can think about it as a super sensitive nose,” said Aridjis-Olivos, adding that the PTR-TOF-4000 then sniffs for VOCs “the brand gently so that they can be identified and weighed in real time.”

The results have shown ozone levels, oxygen VOCs and acid -rich nanoparticles that have increased in concentration with external temperatures. Researchers also observed increased levels of airborne pollutants created by chemical reactions fueled by sunlight in the air.

They notably discovered that, during heat waves, trees release more natural VOC emissions, including isoprene, a pioneer of ozone, which could be harmful in highly wooded places, such as College Station.

“It was really surprising to see how these trees are increasing during heat waves and interact with air pollution,” said Aridjis-Olivos, referring to the large oaks in the region.

“In themselves, trees are not dangerous. It is when they react with other emissions under a strong solar radiation that we obtain a high ozone and secondary organic aerosols which are dangerous for public health.”

Researchers are currently analyzing additional data of their work in the August 2024 field. In the meantime, they share recommendations to stay safe during heat waves:

• Stay inside during the peak hours of the sun (generally from noon to 4 p.m.), when temperatures and ozone levels are the highest.
• Avoid exercising or traveling near the main roads or urban hot spots during extreme heat.
• Keep an eye on the local air quality index and adjust the exterior plans accordingly, when possible.
• Keep closed windows to limit exposure to external air pollutants.

Although these advice can help in the short term, researchers say that real progress depend on understanding how climate change affects atmospheric chemistry and air quality so that scientists can better predict pollutants and protect public health.