What is particulate matter?

Particulate matter is commonly used interchangeably with other terms such as dust, smoke, soot and haze. Particulate matter is a generic term that describes solid or liquid particles that are suspended in the atmosphere.

The potential effect of particulate matter on the environment, human health and amenity depends on the concentration of particulate matter in an area as well as the size and chemical makeup of the particles.

Particulate matter is measured by concentration, which is the mass of particulate matter that is suspended per unit volume of air. It is usually reported in micrograms per cubic metre (µg/m³).

Particulate matter is sub-divided into a number of metrics based on particle size:

• PM₁₀ refers to particulate matter with an aerodynamic diameter less than 10 micrometres (µm) and is sometimes called coarse dust. Particulate matter larger than 10 µm tends to be associated with amenity impacts, while PM₁₀ is associated with health impacts.
• PM_2.5 is a subset of PM₁₀ and refers to particulate matter with an aerodynamic diameter less than 2.5 µm. PM_2.5 is also called fine dust.

Where does particulate matter come from?

Particulate matter around the Hazelwood Rehabilitation Project can come from a variety of internal and external sources, including:

• Rehabilitation activities such as earthworks and demolition, mainly in the form of dust
• Industrial sources not associated with the Project
• Residential/domestic sources such as wood heaters
• Natural sources such as prescribed burns and wind erosion of bare earth
• Motor vehicles through both combustion of fuel and wheel and brake generated dust.

What are the air quality objectives for particulate matter?

The Environment Protection Act 1970 (the Act) provides the main legislative instrument for the protection of the environment within the State of Victoria. The Act provides for the development of regulations and Environmental Reference Standards (ERSs) that contain environmental quality objectives for particulate matter.

Airborne particulate matter arising from activities at the Hazelwood Rehabilitation Project is compared to the objectives set by the Environmental Reference Standard (ERS) for Ambient Air:

• Concentrations of PM₁₀ to be less than 50 µg/m³ as a 24-hour average
• Concentrations of PM_2.5 to be less than 25 µg/m³ as a 24-hour average

Objectives are used to assess air quality monitoring data to determine whether the environmental values set out in the ERS are being protected.

Air quality objectives for the demolition dust - hourly monitors is related to "nuisance dust" throughout the daily demolition period. Safe Work Australia have recommended exposure to dusts should be maintained below 10 mg/m³ (10,000 µg/m³), measured as inhalable dust (8-hour time-weighted average). For more information view the Safe Work Australia Guidance.