Could you please send through PM 2.5 data you have for London Underground platforms. Ideally this would be granular cut by the following dimensions: Underground station Date Time PM2.5 value Ideally this would be daily data but perhaps you only take readings weekly or monthly. Please send through the data for as long as you have been measuring it.

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TfL Ref: EIR-2712-1920

Thank you for your request received by Transport for London (TfL) on 4^th December 2019 asking for information about air quality on London Underground platforms.

Your request has been considered in accordance with the requirements of the Environmental Information Regulations and our information access policy.

Specifically you asked:

“Could you please send through PM 2.5 data you have for London Underground platforms. Ideally this would be granular cut by the following dimensions:

Underground station

Date

Time

PM2.5 value

Ideally this would be daily data but perhaps you only take readings weekly or monthly. Please send through the data for as long as you have been measuring it.”

I can confirm that we hold some information within the scope of your request. However, note that historically TfL has not measured in PM2.5 concentration and the data we hold in that regard is limited. Rather, our monitoring to date has largely been for respirable dust at PM4.0 concentration. PM2.5, PM10, Respirable (PM4.0 or formally PM4.3) and Inhalable (PM100) fractions are all common parameters used to describe the aerodynamic diameter of airborne particles, more commonly referred to as dusts. The first two parameters are primarily used in environmental measurements with the latter two being used in occupational safety. As we measure against occupational exposure on the Underground, dusts in the Underground network are measured in the fraction called respirable dust, which has a diameter of 4.0µm and less. However, following recommendations from the Committee on the Medical Effects of Air Pollutants, we will be measuring in PM2.5 more extensively in the future.

The composition of London Underground dust has been a topic for discussion for many years and over that time the main characteristics have not changed. The particulates below ground in London Underground infrastructure are predominantly iron oxide particles from track, wheel and brake wear. We routinely monitor and undertake dust surveys across the network to evaluate staff and customer exposures to respirable and inhalable dusts. I attach copies of reports following work that TfL conducted in 2016 and 2017 at various Underground stations, which contain some PM2.5 measurements (note that these reports can be also found on the TFL website via the following link (in the “Air Quality on the Underground” section):

https://tfl.gov.uk/corporate/publications-and-reports/environment-reports

Further monitoring reports are planned to be published in the new year.

We are committed to maintaining the cleanest air possible for our staff and customers when using the Tube. London Underground continues to operate well within the Health and Safety Executive exposure limit in spite of the increased demand, higher level of service and increased level of upgrade and maintenance works being delivered in recent years. In addition TfL has informally adopted a much stricter target to meet the recommendations of the Institute of Occupational Medicine (May 2011) to limit inhalable dust exposures to less than 5mg /m3 and Respirable Dusts to 1mg/m3. Moreover, with staff shifts running for 7-8 hours, it is assumed that any exposures by non-employees, primarily customers, will be significantly lower than that for employees.

Dust levels fluctuate from year to year. To ensure that dust levels remain low and within acceptable levels, London Underground has a stringent cleaning regime. This is to ensure a more pleasant environment for customers and staff, and prevent dust from interfering with the functioning of electrical equipment. As new trains are commissioned, London Underground requests the installation of “rheostatic” braking, which reduces the friction action of brakes on wheels by using the engine power to brake the train, thereby reducing the amount of dust produced.

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,

David Wells

FOI Case Officer

FOI Case Management Team

General Counsel

Transport for London

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