BEIJING — The Beijing government put in place emergency measures Wednesday to try to combat thick smog that has encased the city in brown and gray soot. The measures include temporarily shutting more than 100 factories and ordering a third of government vehicle off the streets, official news reports said.
The effort came on the second straight day of air that is rated ‘‘hazardous’’ by the standards of the US Environmental Protection Agency. That rating, in which the air quality index surpasses 300, means people should not venture outdoors.
This month, Beijing has writhed in the grip of the most polluted air on recent record. The surge in pollution, which is happening across northern China, has angered residents and led the state media to report more openly on air issues.
Officials have also begun acknowledging the severity of the pollution. Xinhua, the state news agency, reported that Wang Anshun, the mayor of Beijing, said Monday that the government had come up with a preliminary plan to curb the pollution.
“I hope we can have blue skies, clean water, less traffic, and a more balanced education system,’’ Wang said before the municipal legislature.
Wang also said the number of vehicles in Beijing should be allowed to increase, but slowly. The Xinhua report said there were an estimated 5.18 million vehicles in Beijing, compared with 3.13 million in 2008.
Officials are ordering 180,000 older vehicles off the roads, promoting the use of ‘‘clean energy’’ for government vehicles and heating systems, and growing trees over 250 square miles of land in the next five years, Xinhua said.
Prime Minister Wen Jiabao also addressed the air pollution at seminars on economic development in the past week, Xinhua said.
On Tuesday morning, the air quality index as measured by a device atop the US Embassy in central Beijing reached 517.