Almost a third of new childhood asthma cases in London are attributable to nitrogen dioxide pollution, which is mainly emitted from road transport
'One in five new childhood asthma cases in the UK could be linked to traffic pollution, new research suggests.
Exposure to nitrogen dioxide, which is mainly emitted from road transport, appears to be a "substantial" risk factor for the condition, according to a study in journal The Lancet Planetary Health.
The researchers estimate that four million new cases of childhood asthma globally - 13 per cent of those diagnosed - could be attributable to nitrogen dioxide pollution every year.
In the UK, they suggest 19 per cent of new childhood asthma cases every year are attributable to nitrogen dioxide pollution.
This figure rises to 23 per cent in Manchester and 29 per cent in London.
"Our study indicates that policy initiatives to alleviate traffic-related air pollution can lead to improvements in children's health and also reduce greenhouse gas emissions," lead author Dr Ploy Achakulwisut, from George Washington University, in the US, said.
Recent examples include Shenzhen's electrification of its entire bus fleet and London's Ultra-Low Emission Zone congestion charges."
It is thought that pollution from traffic may damage airways, leading to inflammation and the development of asthma in children who are genetically predisposed to the condition.
While it is not clear which pollutant in traffic air pollution is responsible, previous research has suggested exposure to nitrogen dioxide is key.
Traffic emissions can contribute up to 80 per cent of ambient nitrogen dioxide in cities.
The researchers used global data on nitrogen dioxide concentration and asthma incidence to estimate the number of new cases in children aged one to 18 years old which could be related to traffic pollution.'
Read more: Traffic pollution results in four million child asthma cases every year, research suggests