Travelling on the Tube could be
bad for your health because of tiny metal dust particles in the atmosphere, new
research from a UK university has claimed.
Experts found that the small dust particles in the air, or particulate matter,
in an underground railway were quite different to the dust breathed in every day
and that could have health implications because they could penetrate the lungs
and body easily including the liver, brain and kidneys.
Almost 1.2 billion journeys are made each year on the London Underground
The research team called for more work to be done to discover what the risks
were as the finding could mean that working or travelling on an underground
railway for a sustained period is bad for health.
Matt Loxham, PhD student at the University of Southampton, said: "We studied the
ultrafine dust (or particulate matter) found in an underground station in
Europe.
"Typically, ultrafine dust is composed of inert matter that does not pose much
of a risk in terms of its chemical composition.
"However, in the underground station we studied, the ultrafine dust was at least
as rich in metals as the larger dust particles and therefore, taken together
with their increased surface area to volume ratio, it is of potential
significance in understanding the risks of working and travelling in the
underground.
"These tiny dust particles have the potential to penetrate the lungs and the
body more easily, posing a risk to someone's health."
Previously published work suggested that working in environments such as steel
mills or welding plants, which are rich in airborne metals, like iron, copper
and nickel, could have damaging effects on health.
But little research has been done on the effects of working in an underground
railway environment - a similarly metal-rich environment - and results of
studies that have been conducted are often inconclusive.
Mechanical activity and high temperatures are key to the generation of the
metal-rich dust
While coarse dust is generally deposited in the conducting airways of the body,
for example nasal passages and bronchi, and the fine dust generally can reach
the bronchioles or smaller airways, it is almost exclusively the ultrafine dust
which is able to reach the deepest areas of the lungs, into the alveoli, where
oxygen enters the blood and waste gases leave, to be exhaled.
There is evidence that this ultrafine dust may be able to evade the protective
barrier lining the airways (the epithelium), and enter underlying tissue and the
circulation, meaning that the toxicity of ultrafine particles may not be limited
to the airways but may involve the cardiovascular system, liver, brain, and
kidneys.
Mr Loxham added: "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."
Researchers initially collected airborne dust from a mainline underground
station underneath an airport in Europe.
The research was conducted by the University of Southampton
The metal content of the dust was analysed and a detailed elemental profile was
established for each dust sample.
These profiles were then compared to profiles from other dusts analysed at the
same time, for example dust from wood-burning stoves and a heavily-trafficked
road tunnel, showing that underground particles were very rich in metals,
especially iron and copper.
The team then showed that the dust was capable of generating reactive molecules
which are fundamental to their toxic effects, and that this was dependent on the
metal content of the particles and, importantly, occurred to a greater extent as
the size of the individual particles decreased.
Further work is now being undertaken to examine the effects of underground dust
on airway cells in more detail and the potential mechanisms by which cells may
be able to protect themselves.
The study was funded through the Integrative Toxicology Training Partnership
studentship provided by the Medical Research Council UK and published in
Environmental Science and Technology.