Dust control in metalliferous mining in Australia – Part Three

The hierarchy of controls should underpin the dust control strategy adopted for metalliferous mining, so that occupational exposure to metalliferous dust can be controlled. Several metalliferous dust control measures may be required, and these control measures fall into at least three categories namely; metalliferous dust generation at the source, metalliferous dust generation throughout the workplace, and exposure to individuals at risk. Amongst other strategies are implementation, design and operation of ventilation systems. Separation of metalliferous mine workers position by distance of barriers from airborne dust may minimize exposure. Dust that needs controlling includes nuisance dust, fugitive dust, inhalable dust and respirable dust. The dangers of exposure and overexposure of these types of dust range from acute, chronic and accelerated pulmonary conditions which can eventually result in death. The article is the last of a series of three focused on metalliferous mining in Australia, dust generation and with this article, dust control in metalliferous mining in Australia. It will highlight the aftermath of exposure to metalliferous dust, its generation, the importance of dust control, and conclude with specific Global Road Technology products and how they work in relation to the needs for dust control in metalliferous mining in Australia. 

Health impacts

The grim picture to be painted from post occupational exposure to respirable crystalline silica from metalliferous mining in Australia is best understood from breaking down the actual workplace risks associated with it and why it is very important to have effective dust control solutions in place. Silicosis is caused by inhalation, retention and pulmonary reaction to crystalline silica and when it becomes symptomatic, the primary symptom is usually difficulty in breathing and shortness of breath, first noted with activity or exercise and later as the functional reserve of the lung is also lost it happens at rest. Other complications include tuberculosis, airways obstruction, progressive massive fibrosis and enlargement of the right side of the heart with consistent cough often present. A metalliferous mine worker may develop three types of silicosis, depending on the airborne concentration of respirable crystalline silica. Chronic silicosis usually occurs after 10 or more years of exposure at relatively low concentrations, whilst accelerated silicosis develops 5 to 10 years after the first exposure and acute silicosis develops after exposure to high concentrations of respirable crystalline silica and results in symptoms within a period of a few weeks to 5 years after the initial exposure. Select operations from bagging operators, crush operators, laborers and stone polishers vary in the extent to which exposure limits can be exceeded. 

A toxic mix

Metalliferous mine dusts and associated potentially toxic elements released through mining activities have different chemistries which also determines their mechanisms of action in the mine workers exposed to them. Potentially toxic elements associated with minerals in ore deposits include copper, nickel, uranium and zinc. Even though copper and zinc are essential for life their excess exposure can be toxic. Metalliferous mine dust including uranium and transition metals such as copper, nickel and zinc have the ability to generate reactive oxygen species in biological tissues via Fenton type reactions. In addition, iron bearing minerals such as iron oxides are potential contributors to inflammation in the human lung. Australia is the leading iron ore exporter and significant exporter of uranium, gold and other metalliferous minerals. The journey from pit to port and eventually the export destination is heavily managed by metalliferous mine workers who actively participate in the mining of the metalliferous minerals to be exported. In doing so their health in the workplace should be guarded and protected by all means to justify the economic value brought about by the mining activities. Australia is recognized amongst the global leaders in practices related to safety, risk and environmental management. 

Exposure from cradle to grave

In land clearing activities in metalliferous mining dust control happens through changing the moisture content of wet sprays systems. In haul roads dust control in metalliferous mining occurs through use of water by wetting the particles and increasing their mass and agglomeration although it requires regular application and overwatering can lead to problems. Hygroscopic salts that attract and retain moisture have been used in haul roads although there are corrosive, easily removed by rain and have adverse environmental impacts. Lignin derivatives act as adhesives to agglomerate the fines but usually disappear with rain and result in slippery haul roads when wet. At crushing sites metalliferous dust control has been performed using water, with milling circuits and transfer points utilizing enclosures to contain dust dispersal. The same approach applies for the screening processes which rely on enclosure to minimize dust dispersal. Metalliferous stockpiles have been subject to different dust control techniques which include compaction, roughening or kept moist, vegetating surfaces to reduce wind velocity and chemical suppressants such as wetting agents, binders, crushing agents and foaming agents. 

Best practice dust control

The synergies between Global Road Technology and dust control in metalliferous mining in Australia are based on efficacy of dust control technologies it offers and how they suppress fugitive dust particles that are generated during metalliferous mining activities. Global Road Technology through their flagship product GRT: Activate  offer surface active technology which super-activates water sprayed to control dust in drilling, blasting, excavation, loading and haulage, material crushing, transfer and handling operations. This surface-active agent technology tackles dust control through binding to buoyant fugitive dust particles in the interest of safety and health for the metalliferous mine workers, communities within the vicinity of operation and delicate environments from the harmful effects of respirable and inhalable dust. GRT: Ore-Loc, at the metalliferous mine can be utilized for stacking and stockpiling of bulk material which can later be reclaimed for loading for transit to the port for export and local use in Australia. It tackles dust through coating the material and enhancing resistance to the effects of wind which normally dislodges bulk material fines whilst imparting durability. GRT: Wet-Loc provides dust control well suited to dry underground mine roads as well as surface operations such as the go-line or workshops. Regardless of the magnitude of hauling traffic at the metalliferous mine, GRT: Haul-Loc allows for operations to continue running smoothly without delays due to the mine haul road wearing course conditions. The above examples show that there is not a one product fix – however there is a one company fix for your dust issues – Global Road Technology.

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REFERENCES 

• Colinet et al. 2010. Best Practices for Dust Control in Metal/Nonmetal Mining. Information Circular 9521. Department of Health and Human Services.
• Entwistle et al. 2019. Metalliferous Mine Dust: Human Health Impacts and the Potential Determinants of Disease in Mining Communities. Current Pollution Reports. 5. 67-83.
• Noble et al. 2017. Mineral Dust Emissions at Metalliferous Mine Sites. Environmental Indicators in Metal Mining.
• State of New South Wales. 2017. Airborne contaminants – metalliferous mines. Department of Planning & Environment.