The Greater London Authority (GLA) commissioned researchers from the Environment Research Group (ERG) at Imperial College London to investigate the size of the link between asthma and air pollution in London, using current (2019) and past levels (2016) of air pollution.

Key findings

Exacerbation of asthma by air pollution is estimated to lead to around 700 asthma admissions from 2017 - 2019 in children in London, 7% of all asthma admissions in children in London. (Asthma admissions may have more than one cause e.g. air pollution may worsen response to an allergen.)

Children are more sensitive than adults, so the numbers for adults are smaller (around 200 adult asthma admissions from 2017-2019).

Chronic obstructive pulmonary disease (COPD), another respiratory disease similar to asthma particularly found in smokers, is more common in the elderly and difficult to distinguish from asthma. Results for the elderly therefore combined asthma and COPD.

Exacerbation of asthma and COPD by air pollution is estimated to lead to around 900 asthma/COPD admissions from 2017-2019 in the elderly in London.

The total across these age groups is over 1,700 air pollution-associated asthma and COPD admissions, with asthma admissions in children accounting for over a third of these admissions.

The air pollution attributable asthma admissions in children were estimated to have reduced by 30% since 2016 (from approximately 1,000 to 700).  The equivalent reductions for asthma in adults and COPD/asthma in the elderly were 27% (from around 250 to 180) and 26% (from around 1,200 to 900), respectively. The percentage reductions were similar or smaller for NO2 no cut-off and PM2.5 with or without the cut-off.  These percentage reductions, however, can be attributed to the reductions in air pollution concentrations, as baseline asthma admissions showed similar distribution in the two time periods and the concentration-response functions used were the same.

Authors: Dimitris Evangelopoulos, David Dajnak, Dylan Wood, Daniela Fecht and Heather Walton