A lack of fresh air was found in a deep London Underground station, with air pollution at its worst during the evening rush hour, according to new research led by the University of Surrey, which was carried out as part of a study by the Engineering and physical sciences Council-funded INHALE project.
The Surrey Global Center for Clean Air Research (GCARE) collected airborne particles on a platform at a deep level (about 18 meters underground) at South Kensington station. The results found that the underground environment they tested exceeded the World Health Organization’s air quality guidelines for fine and coarse particulate air pollution*, although it remained within the limits set by the Health and Safety Executive.
The collected pollution was analyzed using an electron microscope by Imperial College London to test their composition, which found small amounts of ultrafine (100 nanometers or less) particles, including iron, manganese and traces of chromium and toxic organics.
Professor Prashant Kumar, study leader and director of GCARE at the University of Surrey, said:
“More work needs to be done to understand how trace metals in small particles in the air affect human health. In the meantime, we recommend that consideration be 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 efforts are made to clean the subway 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.”
Particle monitoring and collection took place on the eastbound Piccadilly Line platform at South Kensington station, which serves both the District and Circle Lines. A Piccadilly line is a deep line that is relatively closed to outside air.
The team monitored air pollution on one platform at the station during working hours (5am to midnight) and off-hours. The survey was conducted from September 2020 to October 2020.
The researchers also found that the underground station contained about twice as many coarse particles of polluted air during working hours compared to non-working hours – which they say could find their way into the human respiratory tract, but mainly to the nose and upper lungs .
In addition, the study also showed that 81 percent of smaller fine particles that can reach nanoparticle size (which is 1/800 the size of a human hair) can find their way to the deeper region people’s lungs, potentially causing health problems.
Professor Alex Porter of Imperial College London, who led the study of the particles collected under an electron microscope, said:
“Our research provides interesting preliminary evidence of pollution levels within an underground station. This is the first time that the chemistry of the smallest particles that can penetrate deep into the lungs and potentially damage cells has been identified. Future research will help determine the potential health consequences of such exposure.”
The research is part of the Engineering and Physical Sciences Research Council-funded INHALE project, led by Imperial College London, in which the University of Surrey and the University of Edinburgh are partners.
*Ultrafine (PM0.1), good (PM0.1-2.5) and coarse (PM2.5-10) particles
Materials provided by University of Surrey. Note: Content may be edited for style and length.