Silica

Silica is a common naturally occurring mineral, also known as silicon dioxide. One common type of crystalline silica is quartz. Silica can be found or manufactured in different forms, broadly divided into crystalline and non-crystalline (amorphous). This information focuses on respirable crystalline silica, which is the more hazardous form. 

Silica is a major constituent of many types of sand. It is also a component of concrete and some bricks and rocks (eg granite, slate, sandstone) and engineered stone. As such, this hazard can be found in industries such as construction, masonry, mining and foundries. 

Breathing in fine (respirable) crystalline silica can cause:

• Silicosis (an incurable lung disease, with inflammation and scarring of the lungs, causing shortness of breath, coughing, fatigue and other symptoms). Silicosis can develop either quickly or slowly depending on exposure levels. It is a potentially fatal condition
• Lung cancer
• Kidney disease
• Increased risk of tuberculosis
• Possible increased risk of autoimmune diseases

Amorphous silica does not have these health hazards. 

• Jack-hammering concrete
• Dry sanding of concrete
• Dry cutting of brick, concrete, engineered stone or natural stone
• Abrasive blasting where the blasting agent or the surface being blasted (eg brick, concrete) contains significant silica content;
• Earthworks
• Demolition of structures containing masonry or concrete
• Rock crushing
• Mineral sample milling
• Roadworks
• Drilling, blasting or excavating in mining operations
• Other tasks where dust is generated from a material with high crystalline silica content

Crystalline silica particles that have just been fractured or abraded are more hazardous (eg crushing or cutting processes). 

Work health and safety legislation requires PCBUs, in consultation with workers, to identify hazards, assess risks and implement practical controls to protect workers’ health and safety. 

Silica can be identified by considering the types of materials used in the task. More information is available in safety data sheets or product data sheets where these are available (eg for abrasive blasting agents) and from material suppliers. 

The risk of silica exposure from the task is assessed by examining the work processes involving crystalline silica. The assessment must consider the dust exposure that could occur. Having dust levels monitored is the most accurate way to assess the risk, however in some cases (eg where there are visible clouds of dust from high silica materials, such as during dry concrete cutting) the risk may be clear without monitoring.  It should be noted that very fine particles may not be visible in air, and monitoring is required to assess the risk from such particles. Workers must not be exposed to respirable crystalline silica levels above the national workplace exposure standard of 0.05 mg/m3.  

The work health and safety regulations require that exposure to hazardous chemicals be prevented where practical. If exposure can’t be prevented, the risk must be reduced firstly by controls other than personal protective equipment (PPE). Regulation 36 of the Work Health and Safety (General) Regulations 2022 and the Work Health and Safety (Mines) Regulations 2022 require that PPE is only to be used to manage any remaining risk. In many circumstances, multiple controls are needed to adequately control exposure to respirable crystalline silica.

Examples of controls for crystalline silica include: 

• Choosing materials (eg abrasive blasting agents) that are silica free or have the lowest  available silica content
• Designing buildings with recesses for services or attachment points, to reduce the amount of chasing and drilling required
• Providing vehicles with enclosed cabs fitted with high efficiency air filters, for dusty earthworks or mining
• Using wet work methods to reduce dust (eg wet cutting or polishing, water sprays during earthworks)
• Using water spray or rubber curtains around conveyor transfer points
• Using local extraction ventilation, either fixed or on-tool (eg for mixing, crushing, milling, drilling or chasing)
• Vacuum clean-up rather than sweeping
• Not blowing dust with compressed air
• In addition to other controls, PPE such as an appropriate respirator (selected in accordance with Australian/New Zealand Standard AS/NZS 1715: Selection use and maintenance of respiratory protective equipment or an equivalent international standard) may be required, depending on the task and the effectiveness of the other controls. If respirators are used, a program including selection, use, maintenance, and training is required, and fit testing is required for fitted respirators.

If there is regular exposure to respirable crystalline silica and there may be a health risk (for example, where exposure is frequently at or above 50% of the workplace exposure standard), health monitoring must be provided to workers under regulation 368 of the WHS regulations. 

Workers must be given information and training on:

• Possible health effects of respirable crystalline silica exposure
• Control measures and how to use them (including PPE)
• Any requirement for health monitoring under regulation 368 of the WHS regulations

The PCBU should keep records of: 

• The risk assessment
• Air monitoring results
• Health monitoring reports
• Training records