Mexican smog triggers car ban

Authorities in greater Mexico City extended an air pollution alert for a fourth day, as smog levels improved slightly but pollution remained at almost 1 times acceptable limits in some areas. The city’s first air pollution alert in 11 years resulted in a driving ban that kept hundreds of thousands of cars from the roads on Wednesday.

A metropolitan commission said that had helped, but hot, dry, windless conditions were expected to last through mid-day on Thursday. In a rotating scheme, a different but equivalent set of cars will be told to stay off the streets on Thursday. The city offered free subway and bus rides to coax people from their vehicles.

Officials advised people to limit outdoor activity due to high ozone levels that were nearly double acceptable limits in the sprawling capital, which lies in a high-altitude valley ringed by smog-trapping volcanic mountains. Amid a muddy brown haze, some residents covered their mouths with scarves or paper masks as they moved through the streets. Some schools kept kids indoors during recess.

Environment Secretary Alejandro Pacchiano said if conditions did not improve, further measures might be considered, such as suspending industrial activity at factories. By late Wednesday afternoon, pollution continued above acceptable limits. Mayor Miguel Angel Mancera said about 1.1 million cars in the Valley of Mexico were ordered off the streets under the restrictions.