On a "blue-sky day", this tourist would have a clear view from the top of a hill in Jingshan Park in Beijing. But on Monday, visibility was less than 1 kilometer. [Photo by Wen Bao/for China Daily]

Capital's air quality rating raises public health concerns, Li Jing, Duan Yan and Cui Jia report in Beijing.

"Fog is not pollution," Du Shaozhong said in his micro blog on Monday morning, in response to a question about Beijing's poor air quality.

It was the third consecutive day of hazy weather, with visibility less than 1 kilometer. And it was the third time in a month that the capital was blanketed in thick smog.

"In Chinese we usually say a fairyland is wreathed in fog. How can it be a fairyland if it is surrounded by pollution?" asked Du, deputy director of the Beijing Environmental Protection Bureau. "But it is true that fog can trap pollutants, which will affect air quality."

The official rating for air quality by Du's bureau on Monday was "slightly polluted" with inhalable particles.

Du blamed stagnant weather conditions - light wind and low atmospheric pressure - a situation not uncommon for Beijing when seasons change.

"At such points, we still have to rely on natural conditions to clear away pollutants, considering we have such a large scale of pollution emissions in the city and a limited environmental capacity," he said.

Beijing residents responded with their views on the air quality through Weibo, a micro-blogging website operated by Sina Corp. Some posted photos of buildings blurred by the thick haze, and some said they feel choked by the smoky air.

"It's like walking in a huge chimney, or having countless people keep puffing secondhand smoke at you - all the time," Yanhanyh wrote on Weibo.

"I don't believe the air is only 'slightly polluted' today. I started to cough after 10 minutes' walk in the open air, and I don't even dare to let my kid go out," said another Weibo user, Dapeng.

By Tuesday night, a little drizzle had begun to refresh the city, but stronger winds and rains are still needed to clear up the haze.

A public trust crisis is spreading over the official readings of Beijing's air quality, especially when some residents find alternatives that are more in line with their own senses.