Paris smog: scientific explanation for worsening air pollution in France

Originally published March 17, 2014

Air pollution levels in Paris have prompted the French government to impose major traffic restrictions that will be in effect on Monday, according to a BBC report.

The Paris traffic restriction, effective from 5:30 a.m. to midnight on Monday, permits only cars and motorcycles with odd-numbered license plate numbers to drive. Even-numbered plates will be allowed to drive on Tuesday if the restriction continues after the government reviews the pollution levels.

Violators will be fined a small sum, while free parking spaces will be made available to vehicles with even-numbered license plates. Public transportation has also been made free for three days, starting Friday.

Motor vehicle exhaust and factory smoke is largely to blame for the severe smog now enveloping France and Belgium. PM10 particulates (particles smaller than 10 micrometres) emitted by vehicles and heavy industry, reached 180 microgrammes per cubic metre on Friday, which is more than double the safety limit.

Under normal convection, pollution is dispersed when the warm air at the earth’s surface rises to the higher atmosphere. Warm days and cool nights in the spring cause temperature inversion, where the surface air that has cooled overnight becomes trapped by a layer of warm air. This causes a smog build-up that can only be dispersed by horizontal winds or by heavy rain.

Similar traffic restrictions were imposed in Paris in 1997.


December 29th, 2015 by