On Friday evening, China’s Environmental Authorities told 23 northern cities to declare the highest possible warning level – Red Alert due to the devastating air pollution the country has experienced since autumn, state media said.

Last December, the capital issued the first ever highest warning level for smog after the adoption of a color-coded emergency warning as part of the government initiative to curb environmental degradation after decades of unconstrained economic growth.

Right after the Ministry of Environmental Protection forecasted the status of the air quality with heavy smog across china’s north cities, Beijing officials immediately issued Red Alert warning on Thursday. The alert will probably last until Dec. 21.

smog-bjThe ministry has also advised 22 more cities affected by the ’worst’ smog to declare red alert warnings, the official China Daily said on Friday.

Nine cities, including Jinan in the province of Shangdong, were advised to issue the lower-status orange alert, Liu Bingjing, the head of air quality management, told the news.

The notification will be the third joint warning by city governments this month, Liu added.

The regular scene of toxic smog covering northern China this year came from a mix of local emissions, unfavorable weather and pollutants wafted in from elsewhere, Bai Qiuyong, head of China’s Environmental Monitoring Center, told the news.

Meanwhile, according to a post of Hebei province Environmental Officials on its Weibo account on Thursday, it requested for a level one emergency warning from major cities in the region starting Friday.

The order requires a large amount of heavy polluting industries in these cities, including in Tangshan, China’s steel capital, to reduce or stop production until Wednesday.

Beijing will issue its highest alert when the daily average air quality index (AQI) forecast would exceed 500 for a day, 300 for two days in a row or 200 for four days.

‘Cautionary measures’

At each level, the color-coded emergency warning system gives advisories for schools, hospitals, and businesses and also gives traffic and construction restrictions.

The threshold for issuing an alert depends on the status of the cities, each city has its own “cautionary measure” that will guide local residents and businesses at each alert stages.

Moreover, residents of smaller cities near Beijing have previously complained about the government’s failure to issue warnings when the level of pollution was just as extreme as in the capital.