FOI request detail

LU air pollution tests

Request ID: FOI-1513-1718
Date published: 04 October 2017

You asked

I am writing to you under the Freedom of Information Act 2000 to request the following information relating to the London Underground: – A station by station breakdown of air pollution tests, for the last three tests of each station I am not sure how this data is held by TfL. Therefore any advice you could give me on how this is stored and the best way to answer this request would be appreciated.

We answered

TfL Ref: FOI-1513-1718

Thank you for your request received by Transport for London (TfL) on 19 September 2017 asking for information about air quality on the London Underground.

Your request has been considered in accordance with the requirements of the Environmental Information Regulations and our information access policy. I can confirm we hold some of the information you require.

We carry over a billion passengers each year on the Underground. The movement of trains over the rails, engineering works and customer use all contribute dust to the system. We manage dust levels by regular cleaning of London Underground stations and tunnels.

In 2003, we commissioned an independent report by the Institute of Occupational Medicine (IOM) to research the health impacts of tunnel dust. The results provided reassurance that the dust on the Underground does not pose a risk to the health of our customers or employees. The report also concluded that a comparison with outdoor air pollution using PM2.5 and PM10 (which measure the weight of dust per cubic metre) could be misleading because of the difference in particle size and content. The report is publicly available, and the link to it can be found here:

We carry out regular monitoring of dust on the Underground, and compare this to the levels set as safe by the Health & Safety Executive (HSE), the enforcing agency for health and safety in the UK. The monitoring shows that dust levels are consistently below the HSE workplace exposure limits for general dust, and are less than a third of the HSE dust exposure limit. Our ongoing monitoring also shows that the levels and content of dust in the underground sections of London Underground’s infrastructure have not changed markedly over time. However we do not conduct station by station tests and so are unable to provide the specific information you require.

Dusts monitored include:

Respirable Dusts, which are particles of a small enough size to penetrate deep into the breathing zone of the lungs.

Crystalline Silica, which comes from concretes and ballast dusts and can cause a disease known as Silicosis.

Iron, which predominates Underground dust and primarily comes from track and wheel wear and to a lesser extent wear from braking systems.

Other metals including Chromium, Nickel, Manganese, Copper, and Zinc, which are alloy metals used in steel track and wheel construction.

The levels measured are compared against the HSE’s Workplace Exposure Limits:

We also monitor research carried out by others very closely, particularly research into air quality on metro systems, and we grant researchers access to our system to facilitate their research. Our Occupational Health team reviews all new, relevant research relating to air quality and assesses the relevance to the Underground. In a number of cases, we have gone directly to the research team to better understand its work and how it may potentially apply to the Underground. Where necessary, we undertake monitoring into the type and composition of dust in underground sections of the Tube network, or into other aspects where we feel this might provide useful information about protecting the health of our employees and passengers. To date, studies of air quality in other parts of the world have not identified any concerns that are not being addressed through our existing programme.

To ensure that tunnel dust levels are managed, we have a cleaning regime in place with a team of staff working every night to remove dust. We continue to meet the levels considered safe by the HSE while demand and service levels have increased, alongside upgrade and maintenance works in recent years.

In addition, as new trains are commissioned, we specify regenerative braking, which reduces the friction action of brakes on wheels by using the engine power to brake the train.

Further information on air quality and dust levels on the Tube is available on our website:

Attached are full copies of TfL’s dust monitoring reports for 2015 and 2016 that are undertaken by our contractors – 4 Rail Services. These cover different lines and locations and measure exposures to station staff, driver operators and commuters. Please note there was no survey in 2014.

Also attached are a number of air quality monitoring reports undertaken by both TFL and contractors. Pollutants measured are listed below. London Underground only monitor particulate pollutants because it is these pollutants that we partly generate and are of more interest from a health perspective.

Inhalable Dust

Respirable Dust

PM 10’s

PM 2.5’s

PM 1.0’s

Respirable Crystalline Silica







The levels measured are considered against the Health and Safety Executive’s Workplace Exposure Limits (EH40)

Dust Monitoring Results Appendices:

Appendix 4 Respirable Airborne Dust Monitoring at Various London Underground Stations and Train Lines – 1st May 2015

Appendix 5 Respirable Airborne Dust Monitoring on the Victoria Line – September 2015

Appendix 6 Respirable Airborne Dust Monitoring at Various London Underground Stations and Train Lines – 22nd September 2016

Appendix 7 Pre Clean - Station and Tunnel Dust Monitoring Results. May-June 2017

Appendix 8 Post Clean - Station and Tunnel Dust Monitoring Results. July – August 2017

Please note that in accordance with TfL’s obligations under the Data Protection Act 1998 (DPA) some personal data in the attachments has been withheld. This is because disclosure of this personal data would be a breach of the DPA, specifically the first principle of the DPA which requires all processing of personal data to be fair and lawful. It would not be fair to disclose this personal information when the individuals have no expectation it would be disclosed and TfL has not satisfied one of the conditions of Schedule 2 of the Data Protection Act which would make the processing ‘fair’.

If this is not the information you are looking for, or if you are unable to access it for some 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

Lee Hill

Senior FOI Case Officer

FOI Case Management Team

General Counsel

Transport for London


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