This March 2014, stagnant air over Europe caused by a thermal inversion created a situation where particulate matter (PM
2.5) accumulated in the air over Paris, peaking at 185 micrograms per cubic meter on the 14th. The World Health Organization considers PM
2.5 levels to be safe when they are below 25. Particulate matter that is smaller than 2.5 micrometers (PM
2.5) - about 1/3 the diameter of a human hair - is of particular concern because it can bypass the bodies defenses and lodge deep into human lungs. Paris officials took the rare step of temporarily barring half of all vehicles from the
road and making public transportation systems free.
This is nowhere near as bad as the pollution was in China in January 2013 though. The image below was taken on a day when the US Embassy ground based sensors registered PM
2.5
measurements of 291 micrograms per cubic meter of air and the air quality index (AQI) in Beijing was 341. An AQI above 300 is considered hazardous to all humans. On January 12, the peak of the air crisis, AQI was 775 the U.S
Embassy Beijing Air Quality Monitor—off the U.S. Environmental
Protection Agency scale—and PM
2.5 was 886 micrograms per cubic meter. Jon Steward of the Daily Show called this air that you could chew.
Watching the Paris pollution saga has made me so jealous. I live in Beijing, and it would be awesome if they'd make public transport free & introduce stricter bans on cars whenever the AQI jumped over 300. (Or 200! It's really not that high in Paris...) I think at the moment all they do is take some government cars off the road, and tell factories in the surrounding countryside to take a couple of days off if the high pollution levels drag on for too long.
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