2de55cd4_ealth_Effects_of_Air_Pollution__Sources
[Air Pollutant] Particulate Matter (PM) [Health Effects] PM is further identified according to their aerodynamic diameter, as either PM10 (particles with an aerodynamic diameter smaller than 10 µm) or PM2.5 (aerodynamic diameter smaller than 2.5 µm). The latter are more dangerous since, when inhaled, they may get deeper into the lungs. A number of research studies have shown association between increase in PM concentration and increase in daily hospital admissions and premature deaths from respiratory and cardiovascular diseases. Persons with pre-existing cardiovascular and respiratory diseases were found to be most susceptible. PM has been classified as carcinogenic to humans (Group 1) by IARC. [Sources] 
There are numerous sources of PM related to human activities as well as natural sources. Combustion of fossil fuels (such as from power plants and vehicles) and biomass burning (such as wildfires) are the key source categories. In general, PM consists of a complex mixture of solid and liquid particles of organic and inorganic substances suspended in the air.
Centre for Health Protection - The Health Effects of Air Pollution
Sources