Commuters on the London Underground inhale on average tens of millions of toxic particles a minute, including iron dust, clothing fragments and their fellow passenger’s dead skin cells.
The Sunday Times has revealed that the Tube has some of the most polluted air in Britain, with levels of toxicity 18 times higher than on surface level trains.
A lack of ventilation in the deepest tunnels, such as on the Central and Northern lines, was cited as the root of the problem.
Scientists have warned that a one-hour daily journey on the Tube can increase the risk of heart attacks, strokes and asthma attacks.
Brynmor Saunders of University College London said: “If the health impacts of Tube dust are the same as surface-level pollution, then a person with this exposure would have a 7 to 11 per cent higher chance of death due to increased risks of cardiovascular diseases.”
The particles in question are so small that they can cross into the bloodstream and become lodged in the brain, heart, liver and other organs where they cause inflammation that can raise the risk of heart attacks and stroke.
Authorities around the country are taking radical steps to counter levels of air pollution.
In October it was announced that Bristol could become the first city to introduce a ban on cars in its city centre.
The highest level of the particles was found on the Victoria line, and was 22 times higher than the government’s limit.
Around 2.8m passengers use the Underground network every day. David Green, a research scientist who worked on the study, said:
“We know a lot of the dust is of human origin because on Saturdays, when there are just as many trains but fewer people, the organic content goes down.”
Lilli Matson, Transport for London’s health and environment director, said: “We are committed to maintaining the cleanest air possible for our staff and customers when using the Tube.”
Main image credit: Getty