Asthma and traffic pollution are linked Askin Tulay Over/Getty

Four million cases of childhood asthma globally could be attributable to nitrogen dioxide from traffic pollution every year.

Pollution from vehicles may damage airways, leading to inflammation and the development of asthma in children who are genetically predisposed to the condition. Although it isn’t certain which pollutant is responsible, previous research has suggested that exposure to NO 2 is key – and traffic emissions can contribute up to 80 per cent of ambient NO 2 in cities.

Ploy Achakulwisut at George Washington University in Washington DC looked at global data on NO 2 concentration and asthma rates to estimate the number of new cases in children between the ages of 1 and 18 that could be related to traffic pollution.


Out of the 194 countries, they found that the UK had the 24th highest proportion of new childhood asthma cases that could be attributable to traffic pollution. This related to 23 per cent of cases in Manchester and 29 per cent in London.

South Korea topped the list, with nearly one-third of new diagnoses linked to NO 2 exposure. The US was in 25th position and India was 58th.

The team found that 92 per cent of cases of childhood asthma attributable to exposure to traffic pollution occurred in areas with average NO 2 concentrations below the World Health Organization (WHO) guideline of 21 parts per billion.

“Our findings suggest that the WHO guideline for annual average NO 2 concentrations might need to be revisited, and that traffic emissions should be a target to mitigate exposure,” says team member Susan Anenberg at George Washington University.

Policy changes can help improve traffic-related air pollution, says Achakulwisut. “Recent examples include Shenzhen’s electrification of its entire bus fleet and London’s Ultra Low Emission Zone congestion charges,” she says.

Journal reference: The Lancet Planetary Health, DOI: 10.1016/S2542-5196(19)30046-4