What is PM2.5?

Particulate matter (PM2.5) refers to particulate matter found in the air with a diameter less than 2.5 micrometers. These include combustible materials, organic compounds, metals, and other small materials that are emitted into the air, usually from power plants, motor vehicles, and burning wood. They are also referred to as fine particles, and they can stay in the air for long periods of time due to their lightness.