What is the chemical formula for particulate matter in pollution?

Particulate matter (PM) in pollution does not have a specific chemical formula because it is a complex mixture of various substances. PM can include solid particles and liquid droplets composed of a range of components such as organic compounds, metals, soot, sulfates, nitrates, and dust. The composition varies based on the source of pollution and environmental conditions, making it difficult to define a single formula. Commonly studied categories of particulate matter include PM10 and PM2.5, which refer to particles with diameters of 10 micrometers and 2.5 micrometers or smaller, respectively.