{"id":6473,"date":"2022-03-10T00:00:00","date_gmt":"2022-03-09T23:00:00","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/?post_type=purple_issue&p=6473"},"modified":"2022-03-23T10:17:13","modified_gmt":"2022-03-23T09:17:13","slug":"london-tube-does-it-harm-your-health","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/2022\/03\/10\/london-tube-does-it-harm-your-health\/","title":{"rendered":"London tube: Does it harm your health?"},"content":{"rendered":"\n

LONDON TUBE:<\/span>
DOES ITS AIR HARM YOUR HEALTH?<\/h2>\n\n

The Mayor of London hopes that 80 per cent of trips in the city will be made on foot, bike or public transport by 2041. But how polluted is the Underground\u2019s air?<\/strong><\/p>\n\n

O<\/span>n any given weekday, the London Underground can see up to five million passengers hopping on and off. Its 11 lines serve 272 stations, and at peak times there can be more than 500 trains hurtling around beneath the streets of London. As it\u2019s been in constant use since the 19th Century, the London Underground has remained largely the same, and hasn\u2019t been updated or researched as much as other forms of transport.<\/span><\/p>\n\n

The pandemic did provide Transport for London (TfL), which manages the London Underground, the opportunity to make some improvements. Ventilation systems were assessed and, according to the Mayor\u2019s Transport Strategy Update in 2021, \u201cthe London Underground ventilation infrastructure is typically designed in excess of statutory minimum requirements with an adequate provision of fresh air.\u201d<\/p>\n\n

\"\"
The London Underground\u2019s air quality is affected by emissions in the city, as well as particles that come from the trains and passengers themselves<\/figcaption><\/figure>\n\n

But how fresh is the air you\u2019re breathing on the Tube? \u201cThe air, even before it gets to the Underground, isn\u2019t perfectly clean,\u201d explains Dr David Green, who leads the aerosol science team at Imperial College London and is a member of the UK\u2019s 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.<\/p>\n\n

\u201cThe 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],\u201d he adds.<\/p>\n\n

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. There are also particles that come from Tube passengers, human and otherwise. Hair and skin cells, plastic fibres from clothing, and debris from the creatures that call the Underground their home all contribute to the air quality.<\/p>\n\n

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. This particulate matter is less than 10 micrometres in diameter, or roughly 0.01mm, and is known as PM10. 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 the body, affecting the brain, heart and other organs.<\/p>\n\n

UK exposure values for PM2.5 are still higher than the guidelines set by the World Health Organization (WHO), which recently changed its target to an average yearly exposure not exceeding 5 micrograms per metre cubed (\u03bcg\/m3 <\/sup>). Previously, this was 10\u03bcg\/m3<\/sup>. The European Union limit is 25\u03bcg\/m3<\/sup>, which is also the limit put in place by UK law.<\/p>\n\n

\u201cThe new WHO guideline is very challenging and currently I don\u2019t think any location in the UK will meet this,\u201d says Green. According to the latest COMEAP study, concentrations of PM2.5 on the London Underground were many times greater than in other London transport environments, and greater than on other subway systems around the world.<\/p>\n\n

CHOOSE YOUR TRANSPORT <\/span><\/strong><\/h4>\n\n

However, when thinking about the air quality in the Underground, Green said it\u2019s important to consider the context within the range of transport modes. A report in 2021 compared the PM2.5 averages across the Tube, bus, car, three types of trains, cycling and walking. Interestingly, the lowest exposures were found on electric and hybrid-style trains, even compared to cycling and walking, though this was not the case when these trains were in stations alongside diesel-powered trains.<\/p>\n\n

\u201c[Travelling on the Tube] for one hour every weekday for 48 weeks a year on the Victoria line would increase your annual exposure to PM2.5 by 6.8\u03bcg\/m3 <\/sup>. This increase is on top of individuals\u2019 usual exposure to pollutants in the air, which varies by location,\u201d says Green. \u201cThis compares to 1.2\u03bcg\/m3<\/sup> in a car. But remember the car pollutes everyone else as well.\u201d<\/p>\n\n

\u201cIt is much better that people get on the Underground than to get in their car to move around London\u201d<\/em><\/strong><\/span><\/p><\/blockquote>\n\n

For Green, this is key. \u201cIt is much better that people get on the London Underground than it is for them to get in their car to move around London. That\u2019s because if you\u2019re sitting in your car, you\u2019re exposed to very high concentrations of vehicle pollutants. <\/p>\n\n

You\u2019re sitting directly behind the exhaust of the car [in front], so you have a higher exposure than cyclists riding along the road or the pedestrians walking past. And the other thing is you\u2019re also polluting the world for everybody else. So, while the car isn\u2019t worse than the Tube in the case of PM2.5, it is much worse for other pollutants like nitrous oxides.\u201d<\/p>\n\n

\"\"
The London Underground trains and stations are cleaned with hospital-grade products so the risk of catching COVID-19 is deemed to be minimal<\/figcaption><\/figure><\/div>\n\n

For those who do have to travel on the Tube, it becomes a matter of choosing the best route. Green\u2019s research found that lines that run deeper, like the Northern line, are generally worse than higher level lines like the Circle, District, Hammersmith & City, and Metropolitan lines. Older lines and the type of trains used all play a part, so Green suggests opting for newer lines and stations that have platform doors installed to reduce exposure. However, he does admit that sometimes there isn\u2019t a lot of choice.<\/p>\n\n

Green is also concerned with the health of the staff on the London Underground. Unfortunately, there isn\u2019t enough data to say yet what the long-term health impacts of working on the Tube will be.<\/p>\n\n

\u201cWe\u2019re working closely with Transport for London to compare sickness absence from people working in London Underground with other TfL workers,\u201d he says. \u201cWe also want to look at pension data, to see if people who work on the Tube may die a little earlier than people who don\u2019t. But [these studies] are in the early stages at the moment.\u201d<\/p>\n\n

Tube passengers can be reassured that the risk of catching COVID-19, however, is minimal.<\/p>\n\n

\u201cTube trains and stations are cleaned with hospital-grade cleaning substances that kill viruses and bacteria on contact and provide ongoing protection,\u201d a TfL spokesperson told BBC Science Focus. <\/em>\u201cIndependent testing by Imperial College London has been carried out monthly since September 2020, taking swabs of touch points in stations, on buses and of air samples in ticket halls and up to the last verified testing round in December 2021 has found no traces of coronavirus on the public transport network.\u201d<\/p>\n\n

by AMY BARRETT <\/strong>
Amy is the editorial assistant for BBC Science Focus<\/em>.<\/p>\n\n

Photos: SHUTTERSTOCK, GETTY IMAGES<\/p>\n","protected":false},"excerpt":{"rendered":"

The Mayor of London hopes that 80 per cent of trips in the city will be made on foot, bike or public transport by 2041. 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