BEIJING — Armed with a device that looks like an old transistor radio, some Beijing residents are recording pollution levels and posting them online.
It’s an act that borders on subversion.
The government keeps secret all data on the fine particles that shroud China’s capital in a health-threatening smog most days.
But as they grow more prosperous, Chinese are demanding the right to know what the government does not tell them: just how polluted their city is.
“If people know what their air is like, they are more likely to take action,” said Wang Qiuxia, a researcher at local environment group Green Beagle, who shows interested residents how to test pollution on a locally made monitoring machine.
Beijing is frequently cloaked in yellow haze. Buildings a couple of blocks away are barely visible. Still, Beijing’s official air quality index records the pollution as “light” - a reading at odds with what many people experience.
A reason for the discrepancy is that the official index does not include the fine particles Mr. Wang’s group is tracking, PM2.5.
Sometimes seen as soot or smoke, PM2.5 is tiny particulate matter - less than 2.5 micrometers in diameter, or approximately one-thirtieth the average width of a human hair - that can result from the burning of fuels in vehicles, power plants and agriculture.
Government agencies did not comment for this report. Scientists say government measures are reducing pollution.
The Ministry of Environmental Protection has announced plans to factor PM2.5 into air quality standards, beyond the coarser PM10 already measured, but not until 2016.
One environmental official was quoted by state media as saying conditions are “not ripe” for the tougher standard as many places would fail.
“The government always has this worry that if they tell the truth, there will be social unrest. But the reality is the reality. Whether you tell the public or not, the danger is still out there,” said Feng Yongfeng, a journalist and founder of Green Beagle, whose mission is to raise awareness of environmental problems and help improve China’s environment.
What matters now, Mr. Feng said, is for people to conduct their own testing “and see the truth right now.”
Green Beagle is recruiting people across the city to test the air in their homes, neighborhoods, offices and public spaces. It lends the sole monitoring device it possesses for up to a week.
Some residents even set it whirring in the supermarket. In return for lending the PM2.5 detector, Green Beagle gets the readings and posts them on its website.