FOI request detail

TfL clean air zone

Request ID: FOI-0647-2223
Date published: 17 June 2022

You asked

Where do you get your data from on air quality? I have a calibrated air quality monitor that measures pm2.5/VOC and health index. If I type my postcode into the government air quality checker( Cm179ht) it tells me that the pm2.5 is over 100 , yet on my device it never goes above 10 outside and is normally reading 2-4. I even took my device into central london and the readings I took were no where near the published figures( I am aware that one days readings can be misleading). Can you explain why I get very different readings to the published data when using calibrated up to date measuring equipment. I am beginning to think this is just a way to raise revenue and no longer about clean air. Also how is it we get moss on our roofs in London. Moss will only grow in areas with clean air.

We answered

TfL Ref: FOI-0647-2223

Thank you for your request received by us on 14 June 2022 asking for information about data on air quality.
Your request has been considered in accordance with the requirements of the Environmental Information Regulations and our information access policy.  I can confirm that we hold the information you require.

The London Atmospheric Emissions Inventory (LAEI) provides emissions estimates for key pollutants (NOx, PM10, PM2.5 and CO2) by source type. The area covered by the LAEI includes Greater London (the 32 London boroughs and the City of London), as well as areas outside Greater London up to the M25 motorway.

These emissions have been used to estimate ground level concentrations of key pollutants NOx, NO2, PM10 and PM2.5 across Greater London for year 2019, using an atmospheric dispersion model. Air pollutant concentration maps and associated datasets are also available for download. This can all be found on the following website:

If this is not the information you are looking for, or if you are unable to access it for any reason, please do not hesitate to contact me.

Please see the attached information sheet for details of your right to appeal as well as information on copyright and what to do if you would like to re-use any of the information we have disclosed.

Yours sincerely

Eva Hextall
FOI Case Management Team
General Counsel
Transport for London

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