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SAFETY AND HEALTH ALERTS AND GUIDANCE
KNOW YOUR HAZARDS: SILICA EXPOSURE IN MINING OPERATIONS In the January 2019 edition of ThinkSafe we looked at Silica exposure in general industries. In this issue we put the spotlight on the resources sector, what to look out for and what guidance is available to both workers and employers. ...
Silica or silicon dioxide exists in most metal, nonmetal and coal mines and is generated during drilling, blasting, mining, crushing, cutting and handling ores. It occurs in either crystalline or noncrystalline (amorphous) forms. The main geological forms of crystalline silica are found in quartz, cristobolite and tridymite. Quartz is most common and occurs in higher concentrations in granite (25 - 40%), shale (around 22%) and sandstones (up to 67%). Very fine dusts of crystalline silica with low densities can travel deep into the alveoli of the lungs where respiration, or air-exchange, occurs. These very small particles are usually less than five micrometres in diameter, and are termed "respirable crystalline silica" (RCS). Workers exposed to high concentrations for long periods above regulated exposure standards are at risk of developing simple pneumoconiosis, progressive massive fibrosis, silicosis, chronic obstructive heart disease and lung cancer. These diseases usually have very long latency periods, so workers may not develop any symptoms or signs until many years after they stop working around RCS.
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Early signs include coughing or wheezing, or experiencing shortness of breath that may limit activities, some people have no early symptoms. Some people are genetically more susceptible. Other exposures, such as smoking cigarettes, are known to enhance the risk of developing these conditions.
REDUCING EXPOSURE The most effective way to prevent developing these diseases is to reduce exposures to as low as possible at all times. Mines Safety Bulletin No. 163 Reducing exposure to respirable crystalline silica (quartz) highlights the need to reduce the amount of dust that is generated and released into the atmosphere.
