Environmental protection officials on Friday called on the government to issue red smog alerts for 23 cities in northern China after Beijing issued a red alert for air pollution.

In what state media said was likely the worst smog since autumn, officials in Beijing had already issued a red alert for the capital on Thursday after warnings of a build-up of toxic air pollution during cold weather that could last until Dec. 21.

An additional nine cities have been advised to issue the lowest-level orange alert, the state-run English-language China Daily reported on Friday.

A resident of Beijing said the capital had woken to blue skies and white clouds, but that the smog had rolled across the capital city by lunchtime on Friday.

"It is acrid, and it makes breathing difficult; it makes you cough," the resident said. "People like me who breathe it in long term will always get a sore throat in these conditions.""I wear a face-mask, and we have bought an air-purifier for our home, and we try not to go out if possible," the resident said. "There's nothing else we can do."

And in Shijiazhuang, in neighboring Hebei province, a resident surnamed Zhang said many people she knows are on medication to counteract the effects of the smog.

"It's like this every year; we take medication for it, a lot of people do," she said. "The air quality has been getting worse and worse, year after year."

Steel producers seen as culprit

Environmental group Greenpeace said progress on air pollution is stalling in the wake of an economic stimulus package aimed at shoring up a flagging economy.

"Beijing is preparing for a five-day smog siege," it said in a statement on its website on Friday, adding that pollution levels were worse in October and November than in 2015.

"The culprit is coal-burning heavy industry in Beijing’s surrounding provinces," the group said.

It said the smog had built up in steel producing areas south of Beijing during the past week.

"When the wind direction changed on Friday, the smog began slowly rolling north, with air passing directly through steel clusters in some of Hebei’s most heavily polluted areas, before settling over Beijing," Greenpeace said.

It blamed a short-term economic stimulus package aimed at propping up the economy, that boosted steel production in the Beijing, Tianjin and Hebei region of northern China.

"With the increase of steel prices came an expansion of coal-fired production in steel producing areas, and with it, a halt in air quality improvement," it said.

Fraudulent vehicle emission certificates

Meanwhile, a lack of accurate measuring equipment for vehicle exhaust emissions is contributing to the problem, according to a campaigner at an anti-pollution group in Beijing.

"Ninety-five percent of the vehicle exhaust testing equipment has been manufactured without a license, and it hasn't even been subjected to a technical inspection," Yan Ziqing, who heads the Pollution Control Alliance in Beijing, told RFA.

"For this reason, none of the vehicle exhaust emissions figures are accurate," Yan said. "The environmental protection ministry lost control of vehicle emissions in 2009, after it introduced a quality seal of approval for vehicle emissions, because everyone just went out and bought their seal."

"It became purely symbolic," Yan said.

He said smog alerts cause huge damage to the economy.

"As soon as a red alert is issued, large numbers of factories have to shut down, and a lot of schools have to close," he said. "The vehicles go onto an odd-even license plate alternating system, which must affect the wider economy."

Reports were circulating online that a man had been detained after taking part in an online action originating in the southwestern city of Chengdu, that called on netizens to collect photos of the recently arrived smog in their city.

A Chengdu resident surnamed Huang said the city government had issued a statement warning people not to go to the city's central Tianfu Square in protest at the pollution.

"A lot of people are saying in public that they won't go there to protest, but privately they really want to," Huang said.

(Radio Free Asia)