We are all used to see pictures of Beijing and Shanghai blanked by pollution and smog, but now NASA’s Terra satellite has taken pictures of a massive haze that is over 750 miles long and stretches between the two cities. The satellite’s Moderate Resolution Imaging Spectroradiometer (MODIS) is able to distinguish between what appears to be cloud and what is pollution. According to NASA, “the brightest areas are clouds or fog. Polluted air appears gray.”
The image is yet another example of China’s frequent bouts of air pollution. “The fog has a smooth surface on the top, which distinguishes it from mid- and high-level clouds that are more textured and have distinct shadows on their edge,” explained Rudolf Husar, director of the Center for Air Pollution Impact and Trend Analysis at Washington University. “If there is a significant haze layer on top of the fog, it appears brownish. In this case, most of the fog over eastern China is free of elevated haze, and most of the pollution is trapped in the shallow winter boundary layer of a few hundred meters.”
What is worrying about these latest images, is that it is not common for the pollution from major cities to spread so far south. However, it appears that on this day, 7th December 2013, US embassies in both Beijing and Shanghai reported that pollution levels in the cities were as high as 480 and 355 micrograms per cubic meter of air respectively. The World Health Organization considers PM2.5 levels to be safe when they are below 25.
Any airborne particulate matter (PM) smaller than 2.5 microns (about one thirtieth the width of a human hair) is considered dangerous because it is small enough to enter the passages of the human lungs. An AQI above 300 is considered hazardous to all humans, not just those with heart or lung ailments.
In China, the situation has become so bad that authorities have ordered school children to stay indoors and halted construction in an attempt to reduce the smog.