The Commission for Air Quality Management (CAQM) for Delhi-NCR last month advised the governments of Delhi, Haryana, Rajasthan and Uttar Pradesh to ensure that sports activities and competitions in schools are not scheduled in November and December, citing the effect of poor air quality on the children who take part.
Exercise affects how a person breathes. An athlete takes in many times more air than someone at rest, and more of it through the mouth, which bypasses some of the filtering done by the nose. A child who is running a race on a smoggy morning, for instance, would draw far more pollution, and draw it deeper into the lungs, than a classmate sitting at a desk.
CAQM is the body that directs or recommends measures to cut air pollution in Delhi-NCR, which typically spikes during the winter months every year.
What does the advisory say?
In its September 10 advisory, CAQM asked states to weigh the "air quality trends prevailing in the area" where an event is scheduled, and said competitions already on the calendar may be rescheduled. Students who miss out because of rescheduling should not be "unduly disadvantaged", the commission said, adding that states should look for other opportunities for them to compete at an appropriate time.
Last year, in November 2025, the Supreme Court had asked CAQM to issue directions to "shift such sport competition to safer months". CAQM subsequently wrote to the four states, asking them to postpone such events.
How exercise affects breathing
{{/usCountry}}Last year, in November 2025, the Supreme Court had asked CAQM to issue directions to "shift such sport competition to safer months". CAQM subsequently wrote to the four states, asking them to postpone such events.
How exercise affects breathing
{{/usCountry}}When exercising, the volume of air drawn in with each breath rises, and breathing shifts from mostly nasal to mostly oral, which bypasses some of the nose's filtering, research published in the journal Scientific Reports in February 2023 said. With air moving faster, pollutants are carried deeper into the respiratory tract, where they can potentially pass into the bloodstream or inflame the cardiovascular system, the researchers wrote.
The American Heart Association, reviewing the evidence in the journal Circulation in June 2010, concluded that exposure to PM2.5 over periods ranging from a few hours to weeks can trigger deaths from cardiovascular disease as well as non-fatal cardiovascular events.
The 2023 study also measured performance. Researchers analysed 1,104 performances in 143 five-kilometre races run by 334 male college track-and-field athletes from 46 US universities between 2010 and 2014. Athletes who had trained and raced in more polluted air over the preceding three weeks tended to run slower. Three weeks at a PM2.5 level of about 10 micrograms per cubic metre, compared with three weeks at about 5, was associated with race times 12.8 seconds slower on average, roughly 1.5%. The authors said a gap of that size can separate first place from sixth in a top-level college race.
This association held even at pollution levels that the US air quality index classifies as good to moderate. The study measured race times, and not the athletes' health.
The Centre for Science and Environment (CSE), a Delhi-based research and advocacy organisation, monitored the air along the route of the Delhi half marathon on November 29, 2015. Runners' average exposure to PM2.5, fine particles small enough to travel deep into the lungs, reached as high as 1,210 micrograms per cubic metre during the race, more than four times the background level at the nearest government monitoring station at Mandir Marg. Athletes typically take in 10 to 20 times as much air as sedentary people, CSE said.
Also read: Gurugram schools face air pollution 5.5 times above safe limits, study finds
Does polluted air cancel out the benefits of exercise?
A study published in the journal BMC Medicine in November 2025, led by Po-Wen Ku of National Chung Hsing University in Taiwan, pooled seven cohort studies covering more than 1.5 million adults in countries including the UK, Taiwan, China, Denmark and the US. Among people whose annual average PM2.5 exposure was below 25 micrograms per cubic metre, meeting recommended levels of leisure-time physical activity was associated with about a 30% lower risk of death from any cause. At 25 micrograms per cubic metre or higher, that reduction shrank to about 12% to 15%.
Co-author Andrew Steptoe, a professor at University College London, said in a statement that toxic air could "to some extent block the benefits of exercise", although not eliminate them.
The study looked at adults and long-term exposure, so it says nothing directly about a child running a race on a single winter morning. Its threshold does give a sense of scale. Delhi's annual average PM2.5 in 2025 was 97 micrograms per cubic metre, according to CAQM, nearly four times the level at which the study found the benefits of exercise began to shrink.
Why are children more at risk?
The World Health Organization (WHO), in its review of evidence on air pollution and children's health, said in an October 2018 report that 93% of the world's children under 15 lived where fine particulate pollution exceeded WHO's air quality guidelines. The report also linked outdoor and household air pollution to respiratory infections and other harm to children's health.
Children breathe more rapidly than adults and so absorb more pollutants, and their brains and bodies are still developing, the WHO said. A race would likely add to that load.