Increase in air pollution takes a toll on your sleep
Even in cities where local pollution levels were below the World Health Organization’s recommended daily exposure limit, a new study has found that bad air quality can lead to respiratory symptoms at lower...
Even in cities where local pollution levels were below the World Health Organization’s recommended daily exposure limit, a new study has found that bad air quality can lead to respiratory symptoms at lower exposure levels than previously thought. That’s due to the human respiratory system being extremely sensitive to short-term fine particulate matter fluctuations even in relatively clean urban environments.
Researchers from the University of Cambridge in the United Kingdom, Tsinghua University in China and the sleep technology company Sleep Cycle found that when pollution levels increased by 10 micrograms of particulate matter per cubic metre (μg/m³), there was a 2.4% rise in coughing levels over the next five days.
They analysed coughing sounds from around 100,000 users of the Sleep Cycle app across 32 cities in 12 countries over 500 days.
“This suggests that there may be no such thing as a safe threshold for exposure to air pollution, although our research is purely observational,” said Cecilia Mascolo, who led the research at Cambridge.
“However, people may wish to consider how they might mitigate their own exposure to air pollution, by using masks or air filters, for example.”
In addition to immediate respiratory irritation, night-time coughing also disrupts sleep, which could link acute air pollution exposure to broader systemic consequences, including cardiometabolic dysfunction, impaired cognitive performance, and neurodegenerative risks linked to poor-quality rest.
Researchers also looked at the case of Los Angeles in 2025, where the city suffered its worst wildfire season in years. They found that a 10-microgram-per-cubic-metre increase in particulate matter produced a 10% surge in nocturnal coughing, suggesting that extreme air pollution episodes trigger immediate, disproportionately large spikes in acute respiratory symptoms.
The researchers also accounted for external factors that could contribute to a rise in coughing levels, such as weather conditions or influenza levels — yet, the pattern caused by air pollution remained.
What are the air quality levels in Europe?
Across the 13 European cities included in the study, average daily fine particulate matter concentrations ranged from a low of 5.47 μg/m³ in Uppsala, Sweden, to a high of 14.70 μg/m³ in Bergamo, Italy. The mean level across all 13 European cities was approximately 10.58 μg/m³. The World Health Organization recommends that daily exposure should not exceed 15 μg/m³ for a 24-hour average more than 3 to 4 days per year.
Overall, European cities in the study exhibited low-to-moderate baseline pollution levels compared to the most polluted cities in the broader global dataset, such as Beijing at 40.97μg/m³ or Shanghai at 33.48 μg/m³.
Broader health consequences
Beyond the irritation of coughing and a sore throat, such symptoms can be a sign of latent conditions, the authors warned.
“Everyone coughs from time to time, but coughing, whether it’s a one-off or more persistent, is a sign of irritation or inflammation in the lungs,” said lead author Tong Xia from Tsinghua University. “A cough could be a sign of something that hasn’t become chronic yet, but might in future.”
