Polluted air may trigger more asthma attacks in urban children and teenagers, according to a study published online in The Lancet Planetary Health journal. Even moderate levels of ozone and fine airborne particulates — two ingredients of smog — appear to increase kids’ risk of asthma attacks, the findings said.

 “The strong association this study demonstrates between specific air pollutants among children in impoverished urban communities and non-viral asthma attacks further augments the evidence that reducing air pollution would improve human health,” said Dr. Hugh Auchincloss, acting director of the US National Institute of Allergy and Infectious Diseases (NIAID). The study also tied the ozone and fine airborne particulates to distinct changes in children’s airways that could trigger an asthma attack, said Dr. Matthew Altman, Associate Professor in the department of medicine at the University of Washington School of Medicine, in Seattle.

It’s one of the first times elevated levels of distinctive air pollutants in specific urban locations have been tied to the risk of asthma attacks.

During an asthma attack, inflammation causes the lining of airways to swell as muscles around the airways contract and mucus floods the passages — all substantially narrowing the space through which air passes in and out of the lungs.

Children in low-income urban areas are at particularly high risk for asthma attacks, the researchers said.

The study included 208 children aged six to 17 with attack-prone asthma living in low-income neighbourhoods in one of nine different US cities.

The researchers later validated their findings in a second group of 189 people aged six to 20 living in low-income areas of four US cities.

The team tracked daily air quality and compared it to reports of asthma attacks in the urban children. They also checked to make sure that the children weren’t suffering from respiratory viruses that can promote asthma.