All schools were closed and private cars were ordered off the streets in Beijing on Tuesday as the Chinese capital issued its first ever red-alert over air pollution levels.
A grey haze descended on Beijing, home to around 21.5 million people, with levels of PM2.5 -- harmful microscopic particles that penetrate deep into the lungs -- at one point above 300 micrograms per cubic metre according to the US embassy, which issues independent readings.
The WHO’s recommended maximum exposure is 25.
Under the alert -- the highest in a four-tiered, colour-coded warning system -- outdoor construction sites are ordered to close, and some schools are urged to do so, with several Beijing residents saying their children had been told to stay at home.
Watch | Beijing in partial shutdown after first-ever ‘red alert’ over pollution
State media said that according to the emergency pollution regulations put in place in early 2013, “…kindergartens, primary and high schools are advised to suspend classes, outdoor operations of construction sites are banned and some industrial plants are required to last.”
The alert coincided with the global climate change talks in Paris, where Chinese President Xi Jinping has vowed “action” on greenhouse gas emissions.
Most of China’s greenhouse gas emissions come from the burning of coal for electricity and heating, which spikes when demand peaks in winter and is the main cause of smog.
It was the first time authorities declared a “red alert” since emergency air pollution plans were introduced two years ago, although levels were far from the city’s worst.
It came a week after thick grey smog shrouded Beijing, cutting visibility severely and sending PM 2.5 levels as high as 634 micrograms per cubic metre.
An odd-even number plate system also means that half the city’s private cars are not allowed onto the streets on alternate days. According to official statistics, almost 4.4 million private cars were registered in the Chinese capital at the end of 2014.
Chinese researchers have identified pollution as a major source of unrest around the country.
Authorities in the capital were heavily criticised after only issuing an orange alert for last week’s pollution.
An editorial in the government-published newspaper the China Daily on Tuesday said the decision to issue the alert showed that “authorities have listened to residents’ concerns”.
“Of course,” it added, “we don’t expect the frequent issuance of a red alert, and we hope that we will be able to forget about it in the near future”, when the government can “keep the air clean for good”.
According to the Beijing Municipal Environmental Monitoring Centre, heavy air pollution will linger until Thursday. It is expected to disperse by Thursday afternoon.