The size of particulate matter has an adverse effect on our health. Particles are defined by their diameter. As we breathe, airborne particles and pathogens with an aerodynamic diameter of 10 microns (PM10) deposit in the nose and pharynx of our respiratory system. Particles with a diameter of 2.5 microns (PM2.5) are small enough to reach our lungs and deposit in the bronchia. Particles smaller or equal to 1 micron (PM1) find their way through the cell membranes of the alveoli into our bloodstream.
According to the CDC, airborne aerosols and particles under 5 microns are the most harmful to human health. They can contain viruses and bacteria and remain airborne in the breathing zone for up to 41 hours or more.

