China's massive 'pollution cloud' can be seen from space

The blanket of haze was so severe Beijing airport was forced to cancel 43 flights and delay an additional 80 more due to bad visibility.

The thick, heavily-polluted air that hangs ominously over many of its residents has long been a real nuisance.

On the ground floor, its a curtain of smog so ubiquitous that highways were forced to close and outdoor school activities cancelled. One of the most disruptive instances took place on the morning of January 10 2012 when the Beijing airport was forced to cancel 43 flights and delay an additional 80 more due to bad visibility. To blame was a stretch of fog and haze that was so massive and gritty NASA satellite photos show it completely blanketing Beijing along with a large swatch of the surrounding region.

Yet amazingly, according to data released by the Chinese government, Beijing saw more than 250 “blue sky days” annually for the past two years. If something doesn't seem to add up, there's a reason: Air quality readings in many of the major cities gauge the severity of given conditions based on the presence of tiny particles that measure up to 10 microns in diameter.

The problem with this standard is that most of the pollution that makes up haze isn’t PM10; it’s finer particles, smaller than 2.5 micrometers in diameter (PM2.5). These particles can embed themselves deep in the lungs and occasionally enter the blood stream. The fine particles are highly reflective, sending sunlight back into space. While the Chinese government doesn't measure PM2.5, the U.S. Embassy in Beijing reports their measurements hourly in a Twitter feed. And on the morning of January 10, PM2.5 measurements indicated that the skies were anything but blue, though by afternoon they had dropped to moderate levels.

Though China has blocked Twitter, the public outcry for official assessments based on readings of PM2.5 has only gotten louder. In response, the Beijing Environmental Bureau announced plans to start releasing PM2.5 measurements before January 23, the Chinese New Year.

“With amazing speed, this term of technical jargon, PM 2.5, became a household word,” Ma Jun, of China’s Institute of Public and Environmental Affairs told the Economist. People understood the huge impact on health, he says, and their fuss helped overcome the barriers to transparency.

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