Particulates or atmospheric particulate matter (see below for other names) are microscopicparticles of solid or liquid mattersuspended in the air. The term aerosol refers to the particulate/air mixture, as opposed to the particulate matter alone,[1] though it is sometimes defined as a subset of aerosol terminology.[2] Sources of particulate matter can be natural or anthropogenic.[3] They have impacts on climate and precipitation that adversely affect human health, in ways additional to direct inhalation.
Types of atmospheric particles include suspended particulate matter; thoracic and respirable particles;[4] inhalable coarse particles, designated PM10, which are coarseparticles with a diameter of 10 micrometers (μm) or less; fine particles, designated PM2.5, with a diameter of 2.5 μm or less;[5]ultrafine particles, with a diameter of 100 nm or less; and soot.
Airborne particulate matter is a Group 1 carcinogen.[6] Particulates are the most harmful form (other than ultra-fines) of air pollution[7] as they can penetrate deep into the lungs and brain from blood streams, causing health problems such as heart disease, lung disease, cancer and preterm birth.[8] There is no safe level of particulates. Worldwide, exposure to PM2.5 contributed to 4.1 million deaths from heart disease, stroke, lung cancer, chronic lung disease, and respiratory infections in 2016.[9] Overall, ambient particulate matter is one of the leading risk factor for premature death globally.[10]