Particulate Matter (PM) refers to a mixture of tiny particles and droplets in the air that can be inhaled into the lungs. These particles are classified based on their diameter: PM10 (particles with a diameter of 10 micrometers or less) and PM2.5 (particles with a diameter of 2.5 micrometers or less). Due to their small size, these particles can penetrate deep into the respiratory system and even enter the bloodstream.