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Inhaled metal Tube dust can enter bloodstream, finds study

By Belinda Liversedge on 19 December 2022

The London Tube network is polluted with metallic particles small enough to enter human bloodstream, a Cambridge university study has found.

In the first study of its kind on the world’s oldest metro, researchers carried out a new type of pollution analysis to arrive at the findings, using magnetism.

They found that the samples contained high levels of a type of iron oxide called maghemite.

Air quality on platforms was worse than in ticket halls or in operator cabins due to poor ventilation in the Underground, as iron-rich dust can be resuspended in the air when trains arrive at platforms.

Researchers say it is not clear whether iron oxide particles pose a health risk to workers or commuters. Photograph: iStock

Although researchers say it is not clear whether these particles pose a health risk to workers or commuters, it throws new light on the problem said Zack Polanski AM, Chair of the London Assembly Environment Committee: "The London Assembly Environment Committee has been raising the alarm for years about the dust on the London Underground and what potential health risks it could pose for both passengers and workers.

"This new study sheds light on a potentially concerning element of London Underground air pollution at some of our city's busiest stations and we will review the findings and what it means for Londoners with interest."

Dust levels are normally monitored using standard air filters, which cannot capture ultrafine particles or identify particles. These levels have been found to remain below limits set by HSE.

But Professor Richard Harrison from Cambridge’s Department of Earth Sciences, the paper’s senior author said: “Our techniques give a much more refined picture of pollution in the Underground. We can measure particles that are small enough to be inhaled and enter the bloodstream. Typical pollution monitoring doesn’t give you a good picture of the very small stuff.”

Some of the particles in the Cambridge study had a diameter of just five nanometres, making them small enough to be inhaled.

The samples were collected in 2019 and 2021 from platforms, ticket halls, and train operator cabins on the Piccadilly, Northern, Central, Bakerloo, Victoria, Northern, District and Jubilee lines.

Read the study here