Managing the London Underground’s air quality with better ventilation systems

A new study, led by the University of Surrey, has concluded that air quality is poor on the London Underground due to a lack of fresh air.

Surrey’s Global Centre for Clean Air Research (GCARE) collected airborne particulates on a deep-level platform – around 18 metres below ground – at South Kensington station. The collection of these samples proved that the environment exceeded the World Health Organization’s air quality guidelines for fine and coarse air pollution particles. Despite this, they remain well within the limits set by the Health and Safety Executive.

The study, titled ‘Characteristics of fine and ultrafine aerosols in the London Underground,’ also found that air pollution is at its worst during the evening rush hour, which could seriously impact people’s health.

Full results of the analysis of the air particles were published in the journal Science of the Total Environment.

Detecting toxic matter in air particles

The pollution collected was analysed using an electron microscope by Imperial College London to test their makeup, which detected tiny amounts of (100 nanometres or less) particles, including iron and manganese, along with traces of chromium and toxic organic matter.

Professor Prashant Kumar, 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 quality 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.”

The monitoring, which took place between September and October 2020, occurred on the eastbound Piccadilly Line platform in South Kensington station. The station also serves the District and Circle Lines; however, the Piccadilly Line platform is at a much deeper level and is relatively closed to outside air.

How does poor ventilation lead to serious impacts on people’s health?

The researchers also found that the underground station contained around double the amount of coarse air pollution particles during operating hours, when compared with non-operating hours. They estimated that these fluctuating air quality levels could find their way to deeper regions of people’s lungs, which could potentially lead to poor health.

Professor Alex Porter from Imperial College London, who led the examination of the particles collected under the electron microscope, concluded:

“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 research is part of the Engineering and Physical Sciences Research Council-funded INHALE project, led by Imperial College London, on which the University of Surrey and the University of Edinburgh are partners.

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