Mexico City bans cars in desperate attempt to fight smog

Thursday, March 31, 2016, 10:32 AM -

The more than 20 million residents of Mexico City will be forced to comply with a driving ban one day a week between April 5 and June 30 as the government attempts to improve air quality.

Officials issued a statement on Wednesday amidst the first air-quality crisis the city has seen since 2005. A Phase 1 emergency for ozone - the second highest alert level - was first issued two weeks ago. The city last saw a phase 1 warning, for particulate matter, in January 2005.

Notoriously smoggy, Mexico City sits in the crater of an extinct volcano at 2,240 metres above sea level. Combining these factors with bright sunshine makes it the perfect cauldron for elevated concentrations of ground-level ozone. Engine efficiency decreases in the thinner atmosphere, flooding the area with excess nitrogen dioxide just waiting to produce photochemical smog when the sun shines.

While cars older than 8 years were previously forced to remain off the roads one day a week, the Supreme Court struck down the rule last year. Drivers could also be exempted from the "no circulation" rule by having their car certified as lower-emission by a government centre.

During the ozone "high season" - when temperatures start to rise but before the rainy season arrives in July - all vehicles will be required to comply with the rule banning them from the roads one day a week, and one Saturday per month.

Federal Environment Secretary Rafael Pacchiano tweeted on Wednesday that the contingency plan was a temporary measure designed to prevent pollution peaks during what is traditionally the worst time of the year for smog in the city. He also announced that changes were coming to the vehicle check program later this year, and that the government was working on other "medium-term solutions such as improvements to public transport."

While Mexico City has a reputation for bad air quality, they have it better than many when it comes to particulate pollution. Nine cities in India and Pakistan lead a World Health Organization report on pollution, with each averaging more than 100 micrograms per cubic meter of fine particulate matter in the air annually. Delhi tops the list at 153 µg/m3.  In a 2014 report, Mexico City averaged 93 µg/m3. By comparison, the famously soupy skies of Beijing average only 56 µg/m3.

Sources: The Guardian | CTV News | Reuters | IDRC | 

Watch: Ground level ozone: what is it?