PM is an abbreviation of Particulate Matter (substance in form of particles).  It is tiny particles of solid matter or liquid in gas state.


PM particles may be :

- Natural - the result of volcanoes, sandstorms, forest and steppe fires, etc. or 
- Created by human activity (anthropogenic) - combustion of fossil fuels in vehicles, power plants and various industrial processes.

PM 10 particles have a size less than 10 μm (micrometers ) in diameter. MP 2.5 particles have a size less than 2.5 μm in diameter. For comparison, a grain of sand is the size of about 90 μm in diameter.

The measurement of the presence of PM particles in the environment is micrograms in a cubic meter. According World Health Organization, the permissible limit for PM 10 particles during a period of 24 hours is 50 micrograms/m3 while for the PM 2.5 is 25 micrograms/m3. During the winter period it is happening in certain parts of Skopje to have the presence of PM particles up to 20 times more than the permitted amount.

When the air is polluted, we take in a large number of PM particles with single inhalation. The bigger particles adhere to the respiratory tract and rarely reach the lungs. They are usually eliminated by rinsing and coughing.

The tiny particles are much more dangerous. They reach the lungs, and those smaller than 2.5 microns go directly into the bloodstream and are thus transported throughout the body.

According to medical science, breathing polluted air can cause stroke, heart disease, lung cancer and other diseases. These diseases, which are a consequence of the air pollution, significantly increase the mortality rate in ​​Macedonia in winter time. Unofficial information (official does not exist) indicates that as a result of air pollution there are up to 1200 deaths per year in Macedonia.