Haze filled the skies over eastern China in early January 2012, extending southward from Beijing over the coastal plain near the Yellow Sea. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this natural-color image on January 6, 2012. In some places, the gray-beige haze is thick enough to completely hide the land surface below.
On January 6, Reuters reported that the city government of Beijing planned to release the results of stricter air pollution standards. Airborne particles are generally measured in microns, or micrometers. A micron is one-millionth of a meter. Beijing’s air-monitoring center has historically tracked particles at 10 microns or larger. Particles with diameters of 2.5 microns or smaller, known as PM2.5, are believed to pose the greatest health risks because they can lodge deeply in the lungs, says the U.S. Environmental Protection Agency. Beijing’s new air-quality standards are expected to monitor PM2.5 particles.