The bad quality of air in Beijing has returned after clear skies appeared during and for a few days of the APEC week held in the Chinese capital earlier this month.
Air control officials issued a hazardous air alert as smog covered the city on Wednesday and called upon citizens to stay in their houses to protect themselves from pollution, according to a Global Times report.
A blue alert, the lowest of the four levels in the warning system devised by the government, was raised by Bejing's air pollution emergency response office at 3 p.m. on Wednesday for the rest of the day and on Thursday.
The Beijing Environmental Protection Monitoring Center also announced on the same day that at 4 p.m., the city's air quality index based on the amount of harmful PM2.5 was at 348.
The authorities blamed pollution in the region at large and the weather conditions for the increase in the volume of pollutants.
Before pollution returned to the city, Beijing experienced unusual blue skies during the stretch of the APEC summit and the week following it, leading citizens to coin the term "APEC blue."
The government had ordered the temporary shutting down of factory operations and construction work in the city and surrounding areas during the event, giving the atmosphere a respite from pollution.
With the termporary ban on pollution sources lifted, Zhang Dawei, director of the monitoring center, said that pollutants have begun to build up.
The official said that the air quality in Beijing will suffer for two or three days.
"All we can do is wait for a new cold front to clean the air," he said.