Beijing has vowed to tighten its air-quality monitoring following widespread anger at discrepancies between government air quality readings and the visible smog that blankets China's major cities.
The Ministry of Environmental Protection said this week it would issue standards for the PM2.5 measurement of suspended particulate, the smallest specks of combusted particles contained in smoke, and the most damaging to human health.
China's air monitoring figures previously omitted measures of PM2.5 particles, leading many ordinary Chinese to club together and buy equipment to detect them, posting the results online.
Thick smog in Beijing grounded hundreds of planes and shut down freeways earlier this week.
Beijing International Airport said it had canceled nearly 500 flights out of Beijing on Monday.
While pollution readings at the time were described as “hazardous” by the U.S. embassy’s pollution monitoring system, China's official air pollution index charted the pollution as "light."
Around 350,000 people die prematurely each year from exposure to outdoor air pollution, with a further 300,000 premature deaths caused by indoor air pollution, according to a 2007 study by the World Bank.
A Beijing-based academic surnamed Liang said the city's pollution appeared to be taking a toll on local residents' health.
"The Tumor Hospital is full of patients, and a large proportion of them have lung cancer, as well as esophageal and bronchial tumors," he said.
He said most people doubted the government's assessment that the smog was "thick fog."
"When you went out, you had to hold your nose," Liang said. "They said it was thick fog but that's total rubbish."
"Fog is light and white," he said. "As soon as the sun comes out, it is gone. This goes on all day, so how can they say it's fog?"
"They say they have implemented car emission controls but it hasn't made any difference."
U.S.-based commentator Zheng Yi said many people were concerned at the government's failure to measure PM2.5 particles.
"These particles have a very serious effect on human health," Zheng said. "They are very small, and they can penetrate everything."
"They can even get into human organs and the bloodstream."
Parent activist Zhao Lianhai, who has led a campaign for compensation for children affected by the 2008 melamine-tainted milk scandal, said many people were simply staying home.
"I haven't been out for several days, because the pollution outside has been really bad," Zhao said.
"Visibility is very low, and it seems very dirty."
Beijing media have reported on the smog in recent days, noting that sales of face-masks and air purifiers had risen sharply in the city with the worsening pollution.
One Beijing resident said: "The smog these days has to do with the weather conditions, but also with damage to the environment."
China's EPA says it has received "overwhelming support" from the general public for PM2.5 measurements, which it planned to follow.
State media were cautiously supportive of the move.
"It is thought [the lack of PM2.5 measurements] is the reason for the frequent discrepancies between good ratings by government and the actual poor experience of urban Chinese," the official news agency Xinhua said in a commentary on Friday.
"Improving the air-quality index involves adding standards for ozone density and the revision of standards for other air pollutants, but adding PM2.5 standards is the most important amendment," the agency said.
It blamed "more cars and more power consumption" for the PM2.5 in the atmosphere.
However, the new air-quality index won't be fully implemented nationwide until 2016, Xinhua said.
Reported by Shi Shan for RFA's Mandarin service and by Bi Zimo for the Cantonese service. Translated and written in English by Luisetta Mudie.