Taking public transport is more beneficial to the environment, but what about your health?
No matter what day it is, 5 million passengers are hopping on and off the tube, which has been in constant use since the 19th Century. Beneath the streets of London, 12 lines are serving 272 stations, and at rush hour over 500 trains are hurtling.
Despite being research carried out for other modes of transport- such as updating the cars with airbags or seatbelts, the tube has been understudied.
The pandemic allowed Tfl (Transport for London – which manages the Underground) to improve its ventilation systems. Thus, the ventilation infrastructure can provide the statutory minimum requirements of fresh air – but how fresh is this air that commuters breathe on the daily basis?
Dr. David Green, who regularly assesses the COVID-19 risk on the Underground, noted that the air is not perfectly clean even before it gets to 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].”
The particles come from the brake blocks rubbing on the wheels, the carriage moving along the rails, and the electrical connection between the collector plate and the live rail. However, particles also come from humans – hair and skin cells, animals that live underground, and plastic fibers from clothing, all contribute to the air quality.
“So, you’ve got iron rubbing on steel, steel on steel, iron, and copper and barium from the barkers,” 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].”
The larger particles are caught by the hair in your throat and nose, keeping them far away from getting into and damaging your lungs. The 2.5 micrometers (PM2.5) in diameter ones are considered to be small particles and these cannot be caught, thus, penetrating deep into your lungs and sometimes bloodstream. These are then transported around the body, affecting the heart, brain, and other organs.
He adds that "We do not have enough evidence to state categorically whether pollution on the tube does or doesn’t harm your health, but we do know that exposure to PM2.5 is harmful. This is shown by studies from all over the world looking at deaths and hospital admissions, and studies on smaller groups of people including those with existing health problems.
However, the dust in subway systems is quite different from PM2.5 in outdoor air and we do not know whether we can extrapolate these findings to the subway environment. So, we are now studying groups of vulnerable people and TfL staff to understand whether exposure to this type of PM2.5 is harmful."
According to his research findings, the lowest exposures were found on electric and hybrid-style trains, the exposure to pollutants in the air varies by location, and the fact that is better to get on the tube than the car to move around London because sitting in the car exposes you to high concentrations of vehicle pollutants. However, “the car isn’t worse than the tube in the case of PM2.5, it is much worse for other pollutants like nitrous oxides”.
The deeper and older running lines are worse such as the Northern line compared to higher level lines like the Circle, District, Hammersmith & City, and Metropolitan lines.
Green will further examine also his greatest concern – the health of the staff – the long-term impacts: “We're working closely with Transport for London (TFL) to compare sickness absence from people working in London Underground with other TFL workers. We 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’t. But [these studies] are in the early stages at the moment.”
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