Dust is a general term used to describe microscopic solid particles suspended in the air.

It is recognised nationally and internationally that the most common metrics for measuring air quality is particulate matter (PM), specifically PM10 and PM2.5. This refers to the size in aerodynamic diameter measured in micrometres (μm).

The composition of dust can vary from location to location. In cities dust tends to be dominated by small particles from combustion sources, such as vehicle emissions. In regional areas, combustion sources are less concentrated, and dust tends to be dominated by larger particles. In Port Hedland, the composition of dust is significantly different, consisting largely of iron oxide.