It’s important to consider a range of factors when determining the level of risk that dust poses to worker health, including the type of dust, the size of the dust particles, the amount of dust in the air, and the length of exposure.

Each of these factors is important to understand the potential for a worker to be exposed and how to effectively control the risk. This article will hone in on how gaining an understanding of the size of dust particles in a workplace is important for controlling worker exposure.

Dust releases in the workplace may result from any form of mechanical breakdown, such as those that occur in mining and quarrying, machining and other process operations, or from the movement of dusty materials.


Figure 1: Particle sizes compared to a five-cent piece.  Source: Workplace Health & Safety Queensland – 


Dusts are solid particles that vary greatly in aerodynamic diameter (size). It is crucial to understand sizes as it influences specific areas in our respiratory system.



Figure 2: The International Commission on Radiological Protection model showing the relationship between aerodynamic diameter and lung deposition.

Examples of common respirable dusts and the associated diseases are:

  • Respirable crystalline silica dust (Silicosis, progressive massive fibrosis, chronic obstructive pulmonary disease)
  • Asbestos fibres (Asbestosis, lung cancer, mesothelioma)
  • Respirable coal dust (Coal workers pneumoconiosis)

Due to the size and nature of the respirable dusts, they can progress further through the body than heavy dusts do, and end up settling in the lungs. This settling in the lungs is the catalyst of the diseases associated with respirable dusts.

Respirable dust particles can be difficult to manage and often require a range of controls to be implemented. For example, water sprays may appear to have successfully removed dust from the air, however, the respirable portion of dust (e.g. silica) in the air may still be present. This is a common occurrence in workplaces because respirable dust particles are invisible to the naked eye.

[Image adapted from Susan Sokolowski]

While water sprays may be effective in targeting larger dust particles, they will fail to impact smaller, respirable particles as they’re small enough to move around the water droplets. Even though the dust appears to have been reduced or eliminated, smaller dust particles are often still present. It’s important to understand the nature and size of the particles to ensure resources aren’t wasted on ineffective control measures.


What is Particle Size Distribution (PSD)? 

Understanding how particle size affects the movement of a particle is the first step in understanding the risk and required controls. Particle Size Distribution (or PSD) is the science of how particles move and behave depending on their size and the environment. By analysing particle size, an occupational hygienist can determine the effectiveness of potential controls.

There are a range of methods for analysing particle size, including laser particle size analysis, aerosol spectrometer or using cascade impactors. These methods allow us to build a clear picture of the types of dust particles present and make an informed decision around the right approach for managing dust. Over the years this technology has become smaller, more accessible and affordable to deploy in the field.


Real-time Monitoring (Control effectiveness case study)

Fixed real-time monitoring was installed at the primary tip of a material handling plant with the intent to measure the levels of the respirable dust at the source. It was found that exposures were constantly well above the national exposure standard.

The site went further and used this real time device relay output to activate water sprays when levels were above a certain set criterion for a sustained period. This also included a full stoppage should those levels not drop once controls are activated. In this example, they were able to utilise real time data to modify and improve the existing control measure in place while having all data at hand to make sound decisions.

More importantly, this technology may provide a very meaningful and effective solution of the age old challenge of early warning against early incidents. With a little more development, the same technology may be modified to provide the same results in other areas of operation. Considering the considerable capital and operational costs of the existing and new technology of mine control systems, this technological advancement is deemed both adequate and beneficia l to ensuring safety and health of workers and profitability of this operation.

Quoting the General Manager of this operation; “No task or activity is more important than the Health and Safety of our employees”, hoping that this type of technology would be widely implemented in a wide range of sectors to ensure production does not take prevalence above employee health. Real-time monitoring provides clients with timely, highly accurate dust measurements in the moment.  This improved delivery of monitoring information gives the workplace an ability to make quick and informed decisions on dust exposure, control and management.


Figure 3: Fixed monitor installed at primary activating water sprays.

It is highly likely that the dust in a workplace can be successfully controlled using a range of quality controls. Real-time monitoring can support your decision making around controls to ensure the most effective and efficient spend of budget. In the scheme of cost to a business, real-time monitoring is a fraction of the investment required to deploy a dust control across an entire site, fleet or workplace. Real-time monitoring can also provide scientific data to support a reduction in the use of PPE in certain scenarios.

If you are ready for the next chapter for your workplace and would like our support to work out the best way to control dust, contact us today to talk to an occupational hygiene consultant.

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