FOI request detail

PM2.5 and PM10 air quality data at platform level

Request ID: FOI-3282-1819
Date published: 20 May 2019

You asked

Please could you provide me with both annual and monthly average PM2.5 and PM10 concentration measurements at platform level - broken down for each TFL Underground station for 2018 and any previous years. Please ensure that the data is provided under a licence that facilitates re-use (the Open Government Licence would be ideal).

We answered

TfL Ref: FOI-3282-1819

Thank you for your Freedom of Information request of 6th March 2019 asking for data on air quality at platform level on the Underground.

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

Specifically you asked:

Please could you provide me with both annual and monthly average PM2.5 and PM10 concentration measurements at platform level - broken down for each TFL Underground station for 2018 and any previous years.”

TfL does not hold the requested data.

We do not yet monitor in PM2.5 or PM10 concentration measurements. Rather, our monitoring to date has 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. Furthermore, there has been no network-wide monitoring of air quality at platform level in 2018, and hence there is no data – either by month or for the year – showing average concentration measurements at each Underground station. However, note that following recommendations from the Committee on the Medical Effects of Air Pollutants, we will be measuring in PM2.5 and PM10 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. You may be interested in the work that TfL conducted in 2016 and 2017 at various Underground stations, which can be seen in the attached reports. A similar report for work carried out in 2018 will be published later this year. Note that the reports can be found on the TFL website via the following link (in the “Air Quality on the Underground” section):

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.

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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