PM10 is particulate matter present in the air, which is 10 microns or less in size (diameter). It remains suspended in the air and is very inhalable. Toxic levels in the air can cause serious health problems.
It’s mostly made up of solids and aerosols composed of small droplets of liquid, dry solid fragments, and solid cores with liquid fragments.
For measurements, you can refer to the following link. I found it comprehensive :