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Airborne Pollutants (2)

Questions to the Mayor of London – answered on 17th October 2019.

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Photo of Keith Prince Keith Prince Conservative

What, in order of impact, are the chief sources of the three primary airborne pollutants that the Mayor claims are killing people in London, and what is his source for this information?

Photo of Sadiq Khan Sadiq Khan Mayor of London

The three primary airborne pollutants are nitrogen dioxide (NO2), fine particulate matter (PM2.5) and coarse particulate matter (PM10). As NO can readily be converted to NO2 in the atmosphere emissions are usually calculated as a mixture of Nitrogen Oxides, NOx.

The London Atmospheric Emissions Inventory (LAEI), which is the GLA’s main dataset for air quality, is used to calculate the contributions from each sector to London’s total emissions. The LAEI is regularly updated and published on the London datastore. The most recent inventory (LAEI 2016) was published in May this year. The LAEI uses publicly available data, such as the Government’s National Atmospheric Emissions Inventory and registers of industrial processes, as well as data gathered by TfL, such as traffic counts, to calculate emissions.


Largest Source

2nd Largest source

3rd Largest source


Road transport

Industrial/commercial Heat/power




Road transport



Road transport

Domestic biomass (wood burning)


* “Resuspension” refers to Particulate Matter that is stirred up from roads or other surfaces back into the atmosphere.