Title - Underground railway dust ‘may pose a risk to health’

Microscopic dust particles in underground railways may pose a risk to public health, according to university research.

Travelling or working on an underground railway for sustained period of time could have health implications due to concentrations of metal-rich microscopic dust particles that can penetrate the lungs.These are the findings of a University of Southampton study, ‘Physicochemical Characterisation of Airborne Particulate Matter at a Mainline Underground Railway Station’, published in the Environmental Science and Technology journal on April 16.Scientists studied the ultrafine particulate matter (PM0.1) found in an underground station beneath an airport in Europe and found there were similar concentrations of airborne metals in the dust particles in heavily-trafficked road tunnels and wood burning stoves.According to the authors of the study, previously published work suggests that working in environments – steel mills or welding plants for example – that are rich in airborne metals including iron, copper and nickel can have damaging effects on health.However, little research has so far been carried out on the effects of working in an underground railway environment, which may also be rich in airborne metals.

The Southampton research team included the Geochemistry Group at the National Oceanography Centre, Southampton, and the Inhalation Toxicology Group at the National Institute for Public Health and the Environment (RIVM) in Bilthoven, Netherlands.

Smaller than PM10 and PM2.5, comparatively little is known about the chemistry of ultrafine PM0.1 particles, but it does not typically pose such a risk to health, the study authors said.

However, the ultrafine PM found in the underground station that the authors studied was different to that in air normal air, as it was rich in metals as larger particulate matter while also having an increased surface area to volume ratio.

Health risk Ultrafine particles can reach the deepest areas of the lungs – the alveoli – where oxygen enters the blood and waste gases leave to be exhaled. According to the study, there is evidence that ultrafine dust may be able to evade the protective barrier lining the airways to enter circulation. This means that ultrafine particles may not just impact on the airways but also on the cardiovascular system, liver, brain and kidneys.

Lead author of the study, University of Southampton PHD student Matt Loxham, said: “These tiny dust particles have the potential to penetrate the lungs and the body more easily, posing a risk to someone’s health.”

As a result of the study’s findings, Mr Loxham called for further research into the health impacts of particulate matter at underground railways.

He said: “Underground rail travel is used by great numbers of people in large cities all over the world, for example, almost 1.2 billion journeys are made per year on the London Underground. The high level of mechanical activity in underground railways, along with very high temperatures is key in the generation of this metal-rich dust, and the number of people likely to be exposed means that more studies into the effects of particulate matter in the underground railway environment are needed, as well as examining how the levels of dust and duration of exposure might translate to effects on health.”

Campaigners have frequently called for more research to be carried out on concentrations of dust on the London underground, but TfL has previously said that tunnel dust on the tube is “highly unlikely” to be dangerous (see airqualitynews.com story).

The study was funded through the Integrative Toxicology Training Partnership studentship provided by the Medical Research Council UK.