Matter present as small particles. Particulate matter, also known as particulates, is produced as an airborne pollutant in many processes. It may be inorganic, e.g. silicate or carbon, or organic, e.g. polyaromatic hydrocarbons (PAHs). Particulates are classified by size; e.g. PM10, with particles less than 10 μm‎ and PM2.5, with particles less than 2.5 μm‎.