China’s capital today issued the first-ever red alert of the year for heavy air pollution as the city of over 22 million people was enveloped by thick smog stated to be the worst in recent months.

Beijing has upgraded its alert for air pollution from orange to red, the most serious level today, state-run Xinhua news agency reported. This is the first time the capital has issued the red alert, which will last from 7:00 AM Tuesday to 12:00 PM Thursday.

The notice, issued after days of heavy smog last week, also places traffic restrictions on certain types of vehicles in the city of 22.5 million people.

The air quality alert of the US Embassy in Beijing showed very unhealthy reading of PMI above 256 which could cause significant health problems for heart and lung diseases and significant increase in respiratory effects among general population.

Yesterday China’s weather observatory issued a yellow alert for smog that will cover the country’s northern regions and asked schools to keep the children not let them outdoors to avoid exposure to heavy smog.

Beijing, Tianjin, parts of the neighbouring provinces of Hebei, Henan and Shandong, as well as parts of eastern Jiangsu province will be shrouded in moderate smog and the southern part of Beijing will be choked by heavy smog, the National Meteorological Center (NMC) said. The smog will be dispersed by a cold front next Thursday, the NMC said.