CIIC:Today's featured article/May25, 2012

From Wiki China org cn
The smog in Beijing

Particulate matter, or PM, is the term for particles found in the air, including dust, dirt, soot, smoke, and liquid droplets. PM2.5 particles are air pollutants with a diameter of 2.5 micrometers or less, small enough to invade even the smallest airways. (More...)