5/10/2016 The Economist
MEXICO’S capital is not a great place to be an asthmatic. Its levels of ozone, a pollutant which can damage lung tissue and cause breathing difficulties, are the highest of any city in Mexico and well beyond the recommended limits of the World Health Organisation. They are worst in the first few months of the year, because of the heat and the absence of rain. But in 2016 they have been particularly high. Indeed, in March, Mexico City endured its first “ozone alert” in almost 14 years. This was followed by further alerts in early April and early May (these were triggered by lower ozone levels, because the regulations had changed). The government responded to the first alarm by introducing new driving rules for those in the wider metropolitan area. From April to June, every car must be kept off the road for one day of the working week and one Saturday a month. The later alerts saw 40% of cars and motorbikes removed from the roads, for up to three days.