Particulate Matter (PM)

Particulate matter is a mix of solids and liquids, including carbon, complex organic chemicals, sulphates, nitrates, mineral dust, and water suspended in the air. Man-made particulate matter mainly comes from industry, building work, diesel and petrol engines, friction from brakes and tyres, and dust from road surfaces. Diesel engines tend to produce much more than equivalent petrol engines. Natural sources of particulate matter include volcanoes, sea spray, pollen and soil. It is also formed in the atmosphere when gases such as nitrogen dioxide and sulphur dioxide are changed in the air by chemical reactions.