By Kim Robson:
Mexico City, the capital of Mexico, is located in the Valley of Mexico, also called the Basin of Mexico. This basin is surrounded by the Trans-Mexican Volcanic Belt in the high mountain plateaus of South-Central Mexico. It has a minimum altitude of 7,200 feet above sea level, and the surrounding mountains and volcanoes reach elevations of over 16,000 feet. This natural geographic “bowl” traps air pollution, so it can’t be naturally cleared by wind. As a result, Mexico City has long had a reputation as one of the Western World’s most polluted cities.
Outdoor air pollution kills 3.3 million people every year, mostly in cities. That’s more than HIV, malaria and influenza combined.
By the 1990s, however, Mexico City had become a proactive model for dramatically lowering pollution levels. By 2014, carbon monoxide levels had dropped dramatically, and levels of sulfur dioxide and nitrogen dioxide (NO2) were nearly three times lower than in 1992. NO2 comes primarily from diesel exhaust and is particularly dangerous; it was estimated to be responsible for 5,900 deaths in London alone last year.
The levels of signature pollutants in Mexico City are similar to those of Los Angeles, which are still much, much lower than, say, Delhi or Beijing. Despite the Mexico City cleanup, the metropolitan area is still the most ozone-polluted part of the country, with ozone levels 2.5 times beyond safe limits defined by the World Health Organization.
To implement the cleanup, the federal and local governments enacted numerous plans, including the constant monitoring and reporting of environmental conditions such as ozone and nitrogen oxides. When the levels of these two pollutants reached critical levels, contingency plans went into effect, which included closing factories, changing school hours, and extending the Day without a Car program to two days a week. The government also instituted industrial technology improvements, a strict twice-yearly vehicle emission inspection, and the reformulation of gasoline and diesel fuels. The introduction of Metrobús bus rapid transit and the Ecobici bike-sharing were among efforts to encourage alternate, greener forms of transportation.
In the past, Mexico City declared these pollution plans in effect after smog reached 1.9 times acceptable limits, or soot reached 1.75 times acceptable limits. Now, the city announces alerts at just 1.5 times acceptable limits. As a result, Mexico City authorities recently declared a pollution alert after smog rose to 1.5 times acceptable limits. The timing couldn’t have been worse: it was on the eve of an unpopular new program to reduce the number of cars on the road in hopes of further improving the capital’s unhealthy air.
Instead of keeping cars at home just two days a week, the new rule, to be in effect at least through June, will keep twenty percent of the city’s cars sidelined every weekday beginning April 5th. Before the new rule was decreed, newer or cleaner cars had been exempt from the regulation, which bans cars from being driven based on their license plate number. To ease commuters’ inconvenience, however, the city is offering some free bus services and taxi discounts.