Particulate matter is the term used for particles that are small enough to reach the lower regions of the respiratory tract. The “10” stands for particles equal to or less than10 micrometers (10 micrometers is about the equivalent of one-seventh the width of a human hair). The particles may be solid or liquid. They may be directly emitted or formed in the atmosphere when gaseous pollutants such as sulfur dioxide and nitrogen oxides react to form fine particles.
PM10 can be generated by moving dry, dusty materials such as sand, gravel, grain and coal. Cutting, grinding and crushing can release PM10. Vehicles release PM10 from tire wear, abrasion against road surfaces and exhaust. Plants and fungus can also emit PM10, such as pollen or mold. Particles can remain suspended for weeks before settling on the ground or falling to earth in rain, snow or fog.
Particles can harm lung tissue by lodging in the lungs causing scarring and decreased lung function. PM10 also causes eye and throat irritation, premature death and reduced visibility from haze.