Air Pollution

Particulate matter (PM) is the term used to describe the mixture of solid particles and liquid droplets found in the air.  Most PM particles form in the atmosphere as a result of chemical reactions between pollutants. These particles come in many sizes and shapes and can be made up of hundreds of different chemicals. Some are emitted directly from a source, such as construction sites, unpaved roads, fields, smokestacks, or fires. Most particles form in the atmosphere as a result of complex reactions of chemicals such as sulfur dioxide and nitrogen oxides, which are pollutants emitted from power plants, industries, and automobiles. PM is the main cause of reduced visibility (haze) in parts of the United States.

 Of all the different types of PM that exist, PM2.5, poses the greatest risk to health. PM2.5 describes fine inhalable particles, with diameters that are generally 2.5 micrometers and smaller. They pose the greatest risk because they can get deep into your lungs, and some may even get into your bloodstream. How small is 2.5 micrometers? Think about a single hair from your head. The average human hair is about 70 micrometers in diameter – making it 30 times larger than the largest fine particle.