Particulate matter

This article is about particles suspended in air. For general discussion of particulate types, see Particle § Distribution of particles. "Particulates" redirects here. For other uses, see Particulates (disambiguation).

Particulate matter (PM) or particulates are microscopic particles of solid or liquid matter, which are suspended in the air. An aerosol is a mixture of particulates and air, as opposed to the particulate matter alone. Sources of particulate matter can be natural or result from human activities. Particulates adversely affect human health and have impacts on climate and precipitation.

Categories of atmospheric particles include inhalable coarse particles, designated PM10, which are coarse particles with a diameter of 10 micrometers (μm) or less; fine particles, designated PM2.5, with a diameter of 2.5 μm or less; ultrafine particles, with a diameter of 100 nm or less; and soot (fine or ultrafine particles primarily made up of carbon).

Airborne particulate matter is a Group 1 carcinogen. Particulates are the most harmful form of air pollution as they can penetrate deep into the lungs and brain from blood streams, causing health problems such as stroke, heart disease, lung disease, cancer, and preterm birth. There is no safe level of particulates. Worldwide, exposure to PM2.5 contributed to 7.8 million deaths in 2021, of which 4.7 million were from outdoor air pollution and the remainder from household air pollution. Overall, ambient particulate matter is one of the leading risk factor for premature death globally.


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