Remember the smog that paralyzed Harbin, China - a city of 10 million last week? Here is what that looks like from space:

From NASA's Earth Observatory:

Some neighborhoods experienced concentrations of fine particulate matter (PM2.5) as high as 1,000 micrograms per cubic meter. For comparison, the U.S. Environmental Protection Agency’s air quality standards say PM2.5 should remain below 35 micrograms per cubic meter. It is extremely rare for particulate levels to reach that high in the absence of a dust storm or forest fire.

Chinese authorities grounded airplanes, shuttered thousands of schools, and closed major roads in response to the surge in pollution. A few days after pollution levels started to rise, Harbin hospitals reported a 30 percent increase in admissions related to respiratory problems, and several Harbin pharmacies were sold out of pollution facemasks, according to media reports.

Cold weather and the lack of wind helped fuel the pollution outbreak, but human factors also played an important role. Wheat and corn farmers in the region light fires in the fall to burn off debris following the harvest. Also, city officials turned on Harbin’s city-wide, coal-powered heating system just prior to the pollution outbreak, according to China’s state-run Xinhua News Agency.

We used to experience something similar, albeit not nearly as severe, here in Austin, Texas when Mexican farmers would burn their crops. A gray haze would envelope the city for several days until the winds picked up or rains scrubbed the air.

Other space shots of Chinese pollution can be seen in "Beijing's air pollution as seen from space" and "China enveloped in smog, as seen from space. Again".