On top of the sweaty armpits in your face and packed carriages, it turns out that air pollution on subways is another factor determined to make your morning commute even worse. That’s despite subway trains being powered by electricity.
A new studyin the journal Environmental Science & Technology has looked into Canadian subway systems and found that the air pollution levels on the platforms of Torontos underground trains are comparable with a typical day in Beijing. While not all of Canadas subways faired quite this poorly, the findingssupport plenty ofother studies that highlight that subways in many cities worldwide area wheezing pocket of air pollution.
The research by the University of Toronto compared the PM2.5 levels on Toronto’s subway lines with Vancouver’s SkyTrain and Montreal’s Metro system. On a poor air quality day in Toronto, the outdoor PM2.5 value isabout 30 micrograms per cubic meter. On the days they studied, the researchers found thatToronto subway platforms and trains had on average 100 micrograms per cubic meter.
Thats comparable with a typical day in Beijing, lead research Greg Evans saidin astatement.Of course, it’s important to remember that youre only exposed to these high levels for the short length of your travels, perhaps 20 minutes to an hour, not a whole day.
Outside of Toronto, Vancouvers Skytrain systemwhich is primarily above ground had PM2.5 values of 17 micrograms per cubic meter and Montreals subway, entirely below ground, averaged 36 micrograms per cubic meter.
PM2.5 is particulate matter, both organic and inorganic, that’s smaller than 400th of a millimeter. Theseparticulates arelinked to numerous deadly health risks, namely involving the heart and lungs. A major source of the harmful particulates comes from fossil fuel combustion and other industrial activity.
Subway trains are primarily electric, sothe particulatesare likely comingfrom a different source. Alternatively, the study found a high concentration of metal in the particulates, which suggests it could be from the train’s wheels grinding against the track.
We know from analyzing the composition of the particles that its not just everyday grime, added Evans. The metal concentrations are very high, and the ratios of manganese to iron are similar to what you see in steel.
While the study only focuses on a few Canadian subways, the study authors say the findings are similar to previously published studies conducted in metro systems across the world. However, since the samplingwas conducted during peak hours, the measurements may overestimate exposure outside of rush hour.
A separate study released earlier this year on Londons pollution levels found that cars produce the most amount of pollution per commuter, however the drivers are also the least exposed to it. Instead, those traveling on the London Underground are exposed to the highest levels of large-sized particles.