Silica - are you aware of the hazards?
Silica is a naturally occurring mineral that is commonly found in sand, concrete and some bricks and rocks. Breathing in fine crystalline silica can cause a range of health conditions, including Silicosis and lung cancer. Workers in the electrical industry can be exposed to silica via dry brick and concrete cutting and wall-chasing. Please read the following information from WorkSafe:
What is the hazard?
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 (associated with silicosis)
- Kidney disease
- Increased risk of tuberculosis
- Possible increased risk of autoimmune diseases
Amorphous silica does not have these health hazards.
Risk management
Occupational safety and health legislation requires employers, 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 material safety 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 be difficult to see 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 exposure standard of 0.1 mg/m3.
The occupational safety and health regulations require that exposure to hazardous substances 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 5.20 of the Occupational Safety and Health Regulations 1996 (the OSH regulations) requires that PPE is only to be used to manage any remaining risk.
Examples of controls for crystalline silica include:
- Choosing materials (eg abrasive blasting agents) that are silica free or have the lowest silica content
- Designing buildings with recesses for services to reduce the amount of chasing 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)
- Shadow vacuuming (eg during drilling)
- 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) may be required, depending on the task and the effectiveness of the other controls
If there is regular exposure to crystalline silica and there may be a health risk (for example, where exposure is frequently at or above 50% of the exposure standard), health surveillance must be provided to workers under regulation 5.23 of the OSH regulations.
Workers must be given information and training on:
- Possible health effects of crystalline silica exposure
- Control measures and how to use them (including PPE)
- Any requirement for health surveillance under regulation 5.21 of the OSH regulations
The employer should keep records of:
- The risk assessment
- Air monitoring results
- Health surveillance reports
- Training records