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It is not just high temperatures that make heatwaves unsafe, say scientists
Stephen Beech and Lauren Haughey Lifestyle and Money Reporter
09:32, 18 Aug 2025
New research has explored some overlooked potential effects of heatwaves(Image: VictorHuang via Getty Images)
Heatwaves could lead to an increase in worrying air pollution, according to new research. Scientists have claimed that it’s not just high temperatures that pose a risk, but also the surge in airborne pollutants exacerbated by heat.
Specialists have especially warned about the risk of prolonged hot weather in already warm places. For instance, over 300 people lost their lives due to heat in Texas in 2023, as reported by local authorities, marking the highest number since the state started recording such fatalities in 1989.
As predictions indicate worsening heatwaves in the coming years, researchers from Texas A&M University’s Atmospheric Chemistry and the Environment (CACE) team sought to understand how extreme heat affects atmospheric chemistry and air quality. They carried out a preliminary study on atmospheric chemistry during a Texas heatwave last August.
The team gathered air samples day and night from August 5 to September 3, 2024, on the university campus, where temperatures varied between 90 and 106 degrees Fahrenheit (32 to 41 degrees Celsius). Samples were collected when there were no wildfires in the vicinity, thus isolating the effects of the heatwave without the influence of wildfire smoke on air quality.
The researchers analysed these air samples for pollutants of public health concern, including nitrogen oxides, ozone, volatile organic compounds (VOCs), and nanoparticles. They employed a variety of sophisticated instruments to identify trace gases and assess aerosol characteristics, including a proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-4000).
Team member Bianca Pamela Aridjis-Olivos said: “You can think of it like a super sensitive nose.” She explained that the PTR-ToF-4000 ‘sniffs’ for VOCs then ‘gently marks them so they could be identified and weighed in real time’.
Findings revealed ‘concerning’ concentrations of ozone, oxygenated VOCs and acid-rich nanoparticles that rose alongside outdoor temperatures. The scientists also noted heightened levels of airborne contaminants produced by sunlight-driven chemical reactions in the atmosphere.
They additionally discovered that, during extreme heat periods, trees emit greater quantities of natural VOC emissions, including isoprene – a precursor to ozone – that could prove hazardous in densely forested areas.
Ms Aridjis-Olivos, a graduate student in aerosol and atmospheric chemistry, said: “It really was surprising, how these emissions from trees increase during heatwaves and interact with air pollution.”
She added: “On their own, the trees’ emissions aren’t dangerous. It’s when they react with other emissions under strong solar radiation that we get elevated ozone and secondary organic aerosols that are dangerous for the public health.”
Now, the scientists are examining further data from their August 2024 research but have produced a series of guidelines for staying safe during extreme heat events. These measures include remaining inside during peak sunlight hours, typically between noon and 4 pm, when temperatures and ozone concentrations reach their highest levels.
Experts also recommend avoiding physical activity or travelling near busy roads or urban hotspots during extreme heat, whilst keeping windows shut to reduce exposure to outdoor air pollutants.
The research team suggests monitoring the local air quality index and modifying outdoor activities accordingly where feasible. Although these tips can help in the short term, the researchers stressed that ‘real progress’ relies on further climate change research.
That way, experts can better understand the implications for atmospheric chemistry and air quality, allowing for more accurate pollution predictions to protect public health.
The findings are due to be presented at the fall meeting of the American Chemical Society (ACS) in Washington, DC.
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