Particulate matter: definition and sources
Particulate Matter (PM) consists of a mixture of solid particles and liquid droplets. PM comes in many different shapes and sizes and can be composed of hundreds of different chemicals.
PM can be either of natural origin or generated by human activity.
Primary PM comes directly from the source, for example from combustion processes.
Secondary PM, on the other hand, is formed in the air from so-called gaseous precursor pollutants such as sulphur oxide, nitrogen oxides, ammonia and Volatile Organic Compounds (VOCs).
More information can be found here: German Federal Office for the Environment and the Swiss Federal Office for the Environment (FOEN).
Important sources of man-made Particulate Matter
- District heating systems
- Stoves and heaters in residential buildings
- Waste incineration plants
- Motor vehicle traffic
- Brakes, tyres and roadways
- Swirling dust on road surfaces
- Bulk handling and certain industrial processes
- Construction
- Agriculture (secondary dust pollution/livestock)
- Even fireworks
Particulate matter is classified according to its size (see photo in the article)
For comparison:
A human hair has an average diameter of 40 to 80µm.
PM10: Coarse particulate matter, diameter between 2.5 and 10µm
PM2.5: Diameter less than 2.5µm
PM0.1: Diameter less than 0.1µm