Dust

Dust is a generic term used to describe fine particles that are suspended in the atmosphere. Airborne particles can be hazardous to human health or cause nuisance. Dust is classified according to the physical size, as follows:

• Deposited matter refers to any dust that falls out of suspension in the atmosphere.
• Total suspended particles (TSP) typically refers to particles 100μm (micrometers) (0.1mm diameter) in size or less.
• PM10 refers to particles 10μm (0.01mm) in size or less.
• PM2.5 refers to particles 2.5μm (0.0025mm) in size or less.

Deposited matter

Deposited matter generally comprises particles larger than 20 micrometres in diameter that rapidly settle out of the air near the point of emission. It is measured to assess if an emission source is causing nuisance. Deposited matter is measured using dust deposition gauges. This method measures dust deposition rate and involves the passive deposition and capture of dust within a funnel and bottle arrangement. Data is usually collected over monthly periods.

Dust deposition gauge

Total suspended particles

Airborne particles up to about 100 micrometres in diameter are referred to as TSP (total suspended particles). These particles can cause nuisance. Health effects associated with TSP mainly arise from the fraction of particles less than 10 micrometres in diameter.

Dust health effects

Not all of the dust that is breathed in will get into the lungs. The larger particles (greater than approximately 100 μm) are filtered out in the nose and the conductive airways (the bronchi and bronchioles). The particles that can enter deep into the lungs are called ‘respirable’.

The factors that influence the health effects of dust are:

1. • size of the dust particles
   • composition of the dust particles
   • concentration of the dust particles in the air
   • duration of exposure (possibly in years) to the dust particles.

The health impacts of dust are generally related to suspended particles in the air, rather than dust deposited from the air. Dust particles PM10 or less in size are likely to have the greatest health impacts because they may be drawn deep into the lungs. Particles larger than PM10 tend to be trapped in the nose, mouth, throat or bronchi and are typically expelled from the body.

Particles less than 10 micrometres in diameter (PM10)

Particles smaller than 10µm are especially concerning as these particles can enter the human respiratory system and penetrate deeply into the lungs, causing adverse health effects.

PM 10 particles in the air (source: https://www.epa.vic.gov.au/for-community/environmental-information/air-quality/pm10-particles-in-the-air)

Particles less than 2.5 micrometres in diameter (PM2.5)

PM2.5 particles can penetrate the lower airways of humans. These particles are so small they can get deep into the lungs and into the bloodstream. There is enough evidence that exposure to PM2.5 over long periods (years) can cause adverse health effects.

PM 2.5 particles in the air (source: https://www.epa.vic.gov.au/for-community/environmental-information/air-quality/pm25-particles-in-the-air)