‘Tube dust’: London launches investigation into potentially dangerous substances detected on Underground

Health and transport experts are to launch an inquiry into potentially harmful “Tube dust” amid concerns about the impact of pollution on commuters using the London Underground.

Previous studies have found high levels of airborne pollutants on the network, mostly comprised of iron, which comes from wear on the brakes and friction between wheels and tracks, and is linked to lung inflammation.

Quartz, associated with kidney and lung conditions, is known to exist in smaller quantities alongside “organic content” that can lead to allergic reactions or asthma attacks. Traces of chromium, manganese and copper have also been detected.

The Bakerloo line has the highest levels of inhalable dust – particles that are small enough to penetrate the deep lung and enter the bloodstream – closely followed by the Victoria line, a 2016 study found. The Circle and District lines recorded the lowest levels. Pollution on the Tube is said to be worse than other comparable public transport systems around the world because of the network’s age and reliance on deep, poorly ventilated tunnels.

Professor Stephen Holgate, a leading air quality expert, said Tube dust was mostly made up of metal particles. He told The Independent: “Metals from the rail and break friction are highly reactive and will damage the delicate lining cell of the lung, like welding fumes do.”

A study by the Committee on the Medical Effects of Air Pollutants, which advises the government on air quality, found it was “likely” that Tube dust posed a health risk and urged transport bosses to find ways to reduce pollutants on the network. Researchers found pollution in Tube stations was up to 30 times higher than beside busy roads.

A 2014 study by researchers at the University of Southampton also highlighted the “significant risk” of “non‐exhaust emissions such as metal‐rich wear particles from road, tyres and brakes”. But an earlier report from the Institute of Occupational Medicine concluded that dust on the Underground did not pose a risk to the health of employees or passengers.

A briefing note for the latest enquiry, which starts on Thursday and is led by the London Assembly’s Environment Committee, said in confined tunnels and stations dust “tends not to disperse”, and that while exposure on the Tube is for limited periods it “still could add significantly to overall exposure”.

The document stated: “For a commuter spending half an hour on the Underground twice a day, five days a week, 48 weeks a year ... the average across the year would be about 26 micrograms per cubic metre – similar to spending the whole year next to a busy road.”

Efforts to reduce the level of dust include new signalling on the Northern and Jubilee lines, which reduce the need to break defensively. TfL has also introduced new techniques to replace tracks, swapping jackhammers for “concrete breaking” that creates less dust.

The inquiry will look into whether increased tunnel ventilation using fans could reduce airborne particulates, and whether barrier doors could could lower the level of pollutants, as was shown in two studies on the Barcelona metro. An electrostatic precipitator could also be deployed, using electrical forces to collect particles.

Caroline Russell, chair of the Environment Committee, said: “Millions of Londoners use the Tube every day but we don’t know the level of air pollutants that they are breathing in. The Environment Committee are committed to finding out the content of tunnel and other dust on the Underground but also what the impact of Tube dust is on the health of workers and passengers.”

Dr Penny Woods, chief executive of the British Lung Foundation, said: “It’s great to see that the London Assembly are looking into pollution on the Underground, as we need to see far more research into all types of pollution and the impacts on our lungs, including the Tube.

“But we must also be mindful that the Tube network and public transport is a major asset for tackling London’s toxic air and moving people out of private cars. That’s why everything must be done to make sure the Tube network is as safe, affordable and effective as possible for all Londoners.”