Particle pollution, or particulate matter, consists of particles that are in the air. These particles come from dust, dirt, soot and smoke, and little drops of liquid. Some particles, such as soot or smoke, are large or dark enough to be seen. Other particles are so small that you cannot see them.
Particle pollution can come from primary or secondary sources. A primary source, such as wood stoves or forest fires, lets off particle pollution directly. A secondary source lets off gases that react and form particles. Examples of secondary sources are coal fires and power plants. Particle pollution also comes from motor vehicles, factories, and construction sites. These can be primary or secondary sources. Particle pollution can be a problem at different times of the year, depending on where you live.
Particle pollution includes:
Coarse particles that are between 2.5 and 10 micrometers
Fine particles that are between 0.1 micrometers and 2.5 micrometers (also known as PM2.5)
Ultrafine particles that are smaller than 0.1 micrometers
Particles bigger than 10 micrometers can irritate your eyes, nose and throat but do not usually reach your lungs. Ten micrometers is about seven times thinner than one human hair.
Fine and ultrafine particles are the size of most concern because they are most likely to cause health problems. Their small size allows them to get into the deep part of your lungs and even into your blood. Data about fine particulate matter (also known as PM2.5) are included in the Vermont Tracking portal.