Particulate Matter (PM) refers to a mixture of tiny particles and liquid droplets suspended in the air. These particles can be composed of numerous substances including acids, organic chemicals, metals, and soil or dust particles. PM is categorized based on the size of the particles, with PM10 (particles with diameters of 10 micrometers or smaller) and PM2.5 (particles with diameters of 2.5 micrometers or smaller) being the most concerning for public health.
