Respirable dust refers to airborne particulates that can be inhaled and travel through your airways and be deposited in your lungs. Examples of materials that produce hazardous dust include crystalline silica, coal, and asbestos (whether in its natural or processed state). Respirable dust is best controlled at its source in mineral mines and quarries. Exposure to silica dust even in small amounts over time can result in silicosis. Exposure to respirable dust can lead to mine dust lung disease and lung cancer. No amount of exposure to crystalline silica is safe for mineral mine and quarry workers. The Queensland Natural Resources and Mining released QGL02 which provides ways to identify, analyse and track risks associated with dust. It is highlights the importance of establishing and maintaining effective controls. Workers exposed to respirable dust should be under health surveillance. This article focusses our attention on respirable silica dust. It tackles exposure to crystalline silica dust at mineral mines and quarries. It concludes with how we here at GRT deal with crystalline silica dust at its source. 

Standards for the mining and quarrying industry

QGL02 falls under the Mining and Quarrying Safety and Health Act 1999. Its recent update was in 2020. Application of QGL02 involves a risk management process. Several risk management techniques are applicable. These risk assessments happen on Similar Exposure Groups (SEGs). These SEGs are a group of workers who have the same general exposure to risk. It could be in the tasks they perform, materials and processes they work. The risk management process starts with identifying hazards. These respirable dust hazards arise from operations such as crushing, excavating, and transporting. Materials like sand & sandstone, shale, granite and clays contain respirable crystalline silica. Then followed by conducting a qualitative risk assessment. If found to be acceptable risk review takes place and periodic monitoring ensures. The risk is then re-evaluated at least every 2 years. If the risk assessment yields unacceptable levels control measures apply. They need to be developed and implemented. When the levels of exposure are uncertain, a quantitative risk assessment happens. It eliminates the uncertainty. Upper confidence limit (UCL0.95) < OEL (occupational exposure limit) yield different results. It leads to risk review and periodic monitoring. UCL0.95 > OEL leads to development and implementation of control measures. This happens before risk review and periodic monitoring. This risk management process governs the decision making processes. It applies an A-B system depending on the situation. This is important at every stage of managing respirable dust risk at the mine. Development and implementation of safety and health management system is important. It should take place from a detailed risk management process. 

Applying the hierachy of controls

The designated authority doing risk analysis should consider the result of hazard identification. Risk monitoring and exceedance investigations has to happen. The work environment and work methods for operations is important. It helps understand the interaction of hazards present in the operation. Effectiveness of control measures in the operation is key to deploy reliable changes. Exposure limits are referenced from the regulation. Hazard controls reduce risk. The hierarchy of control is applicable when controlling respirable dust. Controls at the top of the hierarchy are more effective. There are more reliable than controls at the bottom of the hierarchy. The risk management process for respirable dust must be practicable to a reasonable level. This means that when applying controls the following must be considered:

Are environmental regulations, health and safety concerns or potential profit loss a concern right now?

  • the likelihood of the hazard or the risk concerned occurring
  • the degree of harm that might result from the hazard or risk
  • what the person knows about the hazard or risk and about ways of eliminating the risk
  • the availability and suitability of ways to cut or minimise the risk
  • cost associated with available ways of eliminating the risk and know where the cost is disproportionate to the risk

Why is silica dust harmful?

Silica occurs naturally in a crystalline or amorphous form. It is one of the most common and abundant minerals largely present in the Earth’s crust. In the mining and quarrying industry exposure to respirable crystalline silica can occur in almost all stages of the production processes. Occupational exposure to silica dust leads to adverse health effects. Crystalline silica is carcinogenic. It can be inhaled in the form of quartz from occupational sources. It is natural to wonder whether it is possible to further reduce silicosis mortalities and morbidities. Can improved compliance monitoring and enforcement help? Perhaps reducing exposure limits? Are these efforts going to prevent more deaths? Are they any human benefits to the changes? The answer to all these questions is in elimination of dust at its source. Dust control should take place at the source of the dust. No amount of limits or compliance can reduce the risks associated with crystalline silica dust exposure. Prevention of death is only if no form of dust is exposed to mine workers. Over time even the low exposure to respirable silica dust can result in silicosis. There are three forms of silicosis depending on characteristics of silica exposure. Chronic, accelerated and acute silicosis. The human benefits are only realized when dust is controlled at its source with the intention to cut dust at its source. 

Example of Industry Best Practice

Industry best practice happens through establishing and maintaining effective and reliable controls. Global Road Technology has a variety of dust control solutions. They control respirable crystalline silica dust at the source. We recently penned an article on Silica Dust – Industries at Risk. Silicosis is harmful to human health. It is important for regulations to protect worker safety and health. Dust suppression products should ensure best practice for worker health and safety. In managing respirable crystalline silica dust at the source in activities such as shearing, drilling, crushing and conveying, we recommend GRT Activate. It caters for the hydrophilic and hydrophobic nature of crystalline silica dust. GRT Activate super activates the water. This lowers its surface tension on interaction with crystalline silica. Fine crystalline silica dust to be bound and dislodged from being airborne. Queensland guidelines encourage the elimination of dust at its source. GRT reiterates that “crystalline silica dust control is non-negotiable.” There is no true compensation for the lives lost from exposure to respirable dust. 

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Cox, L.A. 2016. How accurately and consistently do laboratories measure workplace concentration of respirable crystalline silica. Regulatory Toxicology and Pharmacology. 

Department of Natural Resources, Mines and Energy. 2020. Guidelines for management of respirable dust in Queensland mineral mines and quarries. 

Hoy, R.F. and Chambers. D.C. 2020. Silica-related diseases in the modern world. Allergy. 75:11. 2805-2817. 

Leung, C.C., Yu, I.T., and Chen, W. 2012. Silicosis. 379. 1-11. 

Thakur, P. 2019. Health Hazards of Respirable Dusts. Advanced Mine Ventilation. 95-104. 

Zilaout et al. 2017. 15 years of monitoring occupational exposure to respirable dust and quartz within the European industrial minerals sector. International Journal of Hygiene and Environmental Health.