London Underground air pollution could be harming health

The health of London commuters could be being put at risk by air pollution on London Underground platforms, one of which was found to exceed international guideline limits.

A study by the University of Surrey’s Global Centre for Clean Air Research (GCARE) and Imperial College London found that the airborne particles collected at South Kensington tube station exceeded the levels recommended by the World Health Organization, albeit within the limit set by the Health and Safety Executive.

The researchers took samples from the station’s eastbound Piccadilly line platform during both operational hours (5am to midnight) and non-operational times in September and October 2020.

The Piccadilly line was chosen as it is a deep-level route, which at South Kensington is 18 meters below ground, and therefore relatively closed to outside air.

The study found twice the amount of coarse air pollution particles (PM2.5-10) during operational hours than non-operating hours. These particles are small enough to find their way into an individual’s respiratory tract.

Researchers suggested that 81% of the smaller-sized fine (PM0.1-25) particles could find their way to the deeper region of the lungs, which could potentially cause health problems.

The substances detected in the particles included iron, manganese and traces of chromium and toxic organic matter.

Professor Prashant Kumar, study lead and director of GCARE at the University of Surrey, said: “More work needs to be done to understand how the metal traces in the small airborne particles impact people’s health. In the meantime, we recommend that consideration is given to improving ventilation on the London Underground where possible.

“We accept that air pollution on platforms is a very complex problem to solve and that an effort is being made to clean the Underground during quieter periods. Our team points to the newly opened Elizabeth Line as an example of good practice – in particular, the use of a screen between the train and the platform to protect passengers from pollution caused by the trains.”

Professor Alex Porter from Imperial College London, who led the examination of the particles, said: “Our research provides interesting preliminary evidence about the levels of pollution within one underground station. This is the first time the chemistry of the smallest particles, which can go deep into the lung and potentially damage cells, has been identified. Future research will help determine the potential health effects of such exposure.”

The study, published in the Science of The Total Environment journal, found that particle numbers gradually increased throughout the day, with the concentration peaking during the busy evening period (6pm to 9pm) when many workers are travelling home. Particulate concentrations also increased as trains arrived.

The daily average concentrations of PM10 and PM2.5 exceeded WHO guidelines.