Study finds air quality variability at London Underground station

This is one of the conclusions to a study led by Surrey University, which was conducted as part of the EPSRC-funded INHALE project.

In the study, researchers found that a lack of fresh air was found in South Kensington station and that air pollution is at its worst during the evening rush hour.

Surrey's Global Centre for Clear Air Research (GCARE) collected airborne particulates on a platform at the station, which are within air quality guidelines set by the Health and Safety Executive.

The pollution collected was analysed using an electron microscope at Imperial College London to test their makeup, which detected tiny amounts of ultrafine particles, including iron, manganese and traces of chromium and toxic organic matter.

In a statement, Professor Prashant Kumar, study lead and director of GCARE, 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."

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The monitoring and collection of particles took place on the eastbound Piccadilly Line platform in South Kensington station, which also serves the District and Circle Lines. The Piccadilly Line is a deep-level line that is relatively closed to outside air.

The team monitored air pollution between at one platform in the station during operating hours (5 am until midnight) and non-operating hours. The study took place from September 2020 until October 2020.

Researchers also found that the underground station contained around double the amount of coarse air pollution particles during operating hours compared with non-operating hours, which they estimate could find their way to a person's human respiratory tract, but mainly to the nose and upper part of the lungs.

The research also indicated that 81 per cent of the smaller-sized fine particles that can go down to the size of nanoparticles could find their way to the deeper region of people's lungs, which could potentially cause health problems.

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."

“Our monitoring has shown that dust levels on the Tube remain well below limits set by the Health and Safety Executive, but we are going further and have developed a number of innovative new cleaning regimes,” said Lilli Matson, TfL’s chief safety, health & environment officer. “We are working with the authors to review the results of their study and to ensure we fully understand them and how to further reduce the levels further.” 

The research has been published in Science of the Total Environment.