Particulate matter can be either natural or man-made.
Man-made sources of particulate matter include, for example, cars and trucks, incinerators, power and heating plants, stoves and heaters in the home or within agricultural and industrial processes. In the urban environment, traffic also plays a significant role. In this setting, particulate matter is created from diesel soot, fine brake and tire wear and road dust.
Natural sources of particulate matter include, among other things, emissions from volcanoes and seas, soil erosion, forest and brush fires, viruses, bacterial and fungal spores, and algae or cell particles.