MEXICO CITY – "Don't try to breathe in Mexico City." There is advice from a newspaper columnist, as the capital is becoming one of its worst pollutants this year.
This spreading megalopolis has been covered in smoky haze since last weekend, the result of dozens of forest fires and warm, windless weather at the end of the dry season.
On Thursday, the government took the big step to finish primary schools, along with a restrictive public-work project. It also ordered tens of thousands of vehicles outside the streets.
The authorities shut down playgrounds in the capital of the scattering Chapultepec park, as parents were advised to keep the children indoors and windows closed. A semi-final match between the first division's football team Club America and Leon was moved from Mexico City to Queretaro because of the air.
The government reported that the levels of particles of 2.5 microns or less, known as PM2.5, reached 148 micrograms per cubic meter of air Thursday. It is about six times the daily limit recommended by the World Health Organization. The ozone content was also high.
The Mexican capital has long suffered from smog, as it lies in a "bowl" between mountains that fall pollutants. In 1992, the United Nations described it as the most polluted city in the world. At that time, the rising ozone levels are blamed for an estimated 1,000 deaths per year.
The city has come a long way since, as a result of an energetic effort to replace old cars, expand public transport, remove lead from gasoline and close refineries and factories.
Mayor Claudia Sheinbaum has been criticized for not explaining a pollution incident to Tuesday. The leftist mayor, who hired in December, said that the city did not have protocols to deal with particle levels.
"Why didn't she do it on Sunday or Saturday when the quality of the air was obviously poor?" Paola Virrueta, a columnist for Excelsior daily, asked. She urged readers to protect themselves by not breathing.
About 20 million people live in the Mexico City area, one of the largest urban concentrations on the planet.
Gabriela Martinez contributed to this report.