Air at Helsinki Metro stations four times more impurities than outside air
Metal particles can trigger asthma symptoms
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Subterranean stations of the Helsinki Metro have been found to have four times the amount of airborne particles that is present in air in the city outside.
The average content at the Metro stations of the Central Railway Station and Sörnäinen during the day were about 50 microgrammes per cubic metre, whereas measuring stations of the Helsinki Metropolitan Area Council (YTV) at the same time recorded particle contents of 12-18 microgrammes per cubic metre outside.
Air quality in the Helsinki Metro was assessed in an extensive study in 2004, which was conducted by the National Public Health Institute, YTV, the Meteorological Institute, the University of Helsinki, and the research company Nordic Envicon.
Most of the impurities in the air at Metro stations are from the tracks, the wheels, and the bus-bar that supplies the electricity to the trains.
Most of the particles were iron, but samples taken at stations also showed greater amounts of chromium, manganese, nickel, and copper than is contained in outside air.
Päivi Aarnio, head of the YTV Environment Working Group, says that the findings are not particularly worrying. She notes that the situation is much worse in the underground train systems of Stockholm and London. Particle contents at stations of the Stockholm Tunnelbana were five times higher than in Helsinki, and on the London Underground they were ten times as high.
Aarnio notes that a mitigating factor is that passengers generally spend relatively short periods of time at metro stations.
Experts say that a much greater health hazard is posed by airborne particles stemming from incomplete combustion, contained in vehicle exhaust, for instance.
The airborne particles in the Metro are mainly metallic, and are larger than those produced by vehicle exhaust. Their health implications have not been investigated very closely.
"It is certain that all exposure to particles has implications for health. However, I believe that the risks caused by vehicle exhaust are much greater", says Dr. Raimo O. Salonen of the National Public Health Institute.
However, he adds that for sensitive asthmatics, the impurities of air in the Helsinki Metro can cause symptoms, such as cough, or breathing difficulties.
Possible changes at Metro stations include replacing the crushed rock beneath the Metro tracks at stations with concrete, which is easier to clean. Another possibility would be to separate the platform area from the tracks with a wall.
The composition of the metal used in wheels of the trains could also be reconsidered.
Helsingin Sanomat
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| 30.3.2006 - TODAY |
 Air at Helsinki Metro stations four times more impurities than outside air |
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