Dust particles

A class of particles which have equivalent aerodynamic diameters less than 50 µm and includes a mixture of large and fine particles. The larger particles that have equivalent aerodynamic diameters greater than 10µm are generally trapped in our noses and throats, so they do not reach the lungs; however, they may cause nuisance and soiling of surfaces. That said, PM10 particles may also be associated with visible dust, which is why PM10 is often measured in conjunction with TSP.

Particles are often a complex mixture of materials arising from many sources, and are generally grouped into two categories, called PM₁₀ and PM_2.5. Fine particles are able to enter the lungs and are known to have health effects.

PM₁₀ are particles less than 10 μm in diameter. Sources of these particles include combustion sources, but also crushing or grinding operations, pollen, road dust and sea salt.

PM_2.5 are airborne particles with a diameter of less than 2.5 μm. General sources of these particles include all types of combustion processes, including motor vehicles and power plant emissions. Very fine particles pose the greatest risk to human health, as their very small size means they can be breathed deep into the lungs.

*Particles come in a wide range of sizes. They are measured in micrometres (μm) – 1 μm is 0.001 mm.