

Some particles less than 10 micrometers in diameter can get deep into your lungs and some may even get into your bloodstream.

Particulate matter contains microscopic solids or liquid droplets that are so small that they can be inhaled and cause serious health problems. 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. Some are emitted directly from a source, such as construction sites, unpaved roads, fields, smokestacks or fires. These particles come in many sizes and shapes and can be made up of hundreds of different chemicals. The average human hair is about 70 micrometers in diameter – making it 30 times larger than the largest fine particle. How small is 2.5 micrometers? Think about a single hair from your head.

