Does the air pollution on the London Underground harm your health? – BBC Science Focus Magazine
On any given weekday, the London Underground sees up to five million passengers hopping on and off its network. Its 11 lines serve 272 stations, and at peak times there can be over 500 trains hurtling around beneath the streets of London.
Despite its constant use since the 19th Century, the London Underground has been relatively under-researched. While other modes of transport have been studied and updated accordingly – think back to when we didn’t have seatbelts in cars, or airbag…….
On any given weekday, the London Underground sees up to five million passengers hopping on and off its network. Its 11 lines serve 272 stations, and at peak times there can be over 500 trains hurtling around beneath the streets of London.
Despite its constant use since the 19th Century, the London Underground has been relatively under-researched. While other modes of transport have been studied and updated accordingly – think back to when we didn’t have seatbelts in cars, or airbags – the sprawling tube system has remained largely the same.
The pandemic did provide Transport for London (TfL), who manage the Underground, the opportunity to make some improvements. Ventilation systems were assessed and according to the Mayor’s Transport Strategy Update in 2021 “the London Underground ventilation infrastructure is typically designed in excess of statutory minimum requirements with an adequate provision of fresh air.”
But how fresh is the air that you’re breathing on the tube?
“The air, even before it gets to the Underground, isn’t perfectly clean,” explained Dr David Green, who leads the aerosol science team at Imperial College London and is a member of the UK’s Committee on the Medical Effects of Air Pollution (COMEAP). Green is also part of a group commissioned by TfL to regularly assess the COVID-19 risk on the Underground.
“The urban background air already has a low level of particulate matter, but on top of that you have all these extra emissions [coming from the tube].”
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These include particles that come from the carriage moving along the rails, the brake blocks rubbing on the wheels, and the electrical connection between the collector plate and the live rail.
“So you’ve got iron rubbing on steel, steel on steel, iron and copper and barium from the brakers,” says Green. “There’s lubricant on the wheels and that contains things like carbon and molybdenum. We find these metallic compounds in the atmosphere [on the Underground].”
There are also particles that come from tube passengers, human and otherwise. Hair and skin cells, plastic fibres from clothing, and animal particulates from the creatures that call the Underground their home all contribute to the air quality.
Some particles are large enough to be caught by the hairs in our nose and throat, stopping them from getting into our lungs and causing damage there. These are typically referred to as PM10; particulate matter that is under 10 micrometres in diameter, or roughly 0.01mm.
The smaller particles that are under 2.5 micrometres in diameter are referred to as PM2.5, and these are the ones that can penetrate deep into the lungs and may also enter the bloodstream to be transported around …….
Source: https://www.sciencefocus.com/news/london-underground-air-pollution/
