What is crystalline silica? 

Silica is silicon dioxide, a naturally occurring and widely abundant mineral that forms the major component of most rocks and soils. There are non-crystalline and crystalline forms of silicon dioxide. The most common type of crystalline silica is quartz (CAS 14808-60-7). 

Different types of rock and rock products can contain different amounts of crystalline silica, for example: 

Type	Amount of crystalline silica (%)
Marble	2
Limestone	2
Slate	25 to 40
Shale	22
Granite	20 to 45 (typically 30)
Natural sandstone	70 to 95
Engineered stone	Up to 97
Aggregates, mortar and concrete	various

What is silica dust? 

Silica dust or respirable crystalline silica (RCS) is generated in workplace mechanical processes such as crushing, cutting, drilling, grinding, sawing or polishing of natural stone or man-made products that contain silica. RCS can penetrate deep into the lungs and can cause irreversible lung damage.

Work activities that may represent a high risk exposure 

Silica is one of the most abundant minerals found in the earth’s crust and is used in many products across a variety of industries and workplaces. Crystalline silica is most dangerous to health when dust is generated, becomes airborne and is then inhaled by a worker. 

Examples of work activities that can generate RCS include: 

• fabrication and installation of engineered stone countertops 
• excavation, earth moving and drilling plant operations 
• clay and stone processing machine operations 
• paving and surfacing 
• mining, quarrying and mineral ore treating processes 
• tunnelling 
• construction labouring activities 
• brick, concrete or stone cutting; especially using dry methods 
• abrasive blasting (blasting agent must not contain greater than 1% of crystalline silica) 
• foundry casting 
• angle grinding, jack hammering and chiselling of concrete or masonry 
• hydraulic fracturing of gas and oil wells, and 
• pottery making. 

What diseases can silica dust cause? 

If a worker is exposed to and breathes in RCS they could develop: 

• acute silicosis - can develop after a short exposure to very high levels of silica dust, within a few weeks or years, and causes severe inflammation and an outpouring of protein into the lung 
• accelerated silicosis  - can develop after exposures of 3 to 10 years to moderate to high levels of silica dust and causes inflammation, protein in the lung and scarring of the lung (fibrotic nodules) 
• chronic silicosis - can develop after long term exposure to lower levels of silica dust. It can lead to fibrotic nodules, shortness of breath, and progressive massive fibrosis 
• chronic bronchitis
• emphysema 
• lung cancer 
• kidney damage, or 
• scleroderma - a disease of the connective tissue of the body resulting in the formation of scar tissue in the skin, joints and other organs of the body. 

Choosing the best control measure 

Under the model WHS Regulations, PCBUs have specific duties to manage the risks to health and safety when using, handling, generating and storing hazardous chemicals, including silica. PCBUs also have a duty to ensure the workplace exposure standard for crystalline silica is not exceeded and to provide health monitoring to workers. 

Managing risks and worker exposures to silica can be achieved by selecting and implementing measures using the hierarchy of controls: 

• substitution such as choosing a benchtop product that does note contain crystalline silica 
• isolation of the hazard – using principles of safe work design to designate areas for tasks that generate dust and appropriate worker positioning during these tasks, using enclosures and automation to conduct dust generating tasks 
• engineering controls that minimise the risk of exposure to generated dust, for example, local exhaust ventilation, water suppression (wet cutting) or using tools with dust collection attachments 
• administrative controls, including good housekeeping policies, shift rotations and modifying cutting sequences 
• personal protective equipment including appropriate respiratory protective equipment (generally a minimum of a P2 efficiency half face respirator) and work clothing that does not collect dust. 

More than one control will normally be required to adequately protect workers, and must be used when processing engineered stone.

Preventing uncontrolled processing of engineered stone

Under the model WHS Regulations, PCBUs must not process, or direct or allow workers to process, engineered stone unless the processing is controlled. Any cutting, grinding, trimming, sanding, abrasive polishing and drilling of engineered stones using power tools or other mechanical plants, must be controlled using one of the following:

• a water suppression (wet cutting) system
• an on-tool dust extraction system, or 
• local exhaust ventilation system.

In addition, all workers who process engineered stone must be provided with and wear respiratory protective equipment.

Health monitoring for workers exposed to crystalline silica 

Under the model WHS Regulations, PCBUs must provide health monitoring for workers if they are carrying out ongoing work using, handling, generating or otherwise exposed to respirable crystalline silica and there is a significant risk to the worker’s health because of exposure. 

The minimum health monitoring requirements for crystalline silica include: 

• collection of demographic, medical and occupational history 
• records of personal exposure 
• standardised respiratory questionnaire 
• standardised respiratory function tests, for example, FEV1, FVC and FEV1/FVC, and 
• chest X-Ray full PA view (baseline and high risk workers only). 

Further information about the duties for health monitoring can be found in:  

• Health monitoring for exposure to hazardous chemicals - Guide for medical practitioners

• Health monitoring – Guide for crystalline silica

Workplace Exposure Standard (WES)

The workplace exposure standard (WES) for RCS is 0.05 mg/m³ (eight-hour time weighted average). The WES must not be exceeded.

PCBUs should keep worker exposure to silica dust as low as reasonably practicable. Air monitoring must be conducted if there is any uncertainty that the WES is being exceeded or to find out if there is a risk to a worker’s health. 

Further information about WHS duties related to crystalline silica

You can find further information on what you must do to keep your workers safe from the risks of crystalline silica in our Working with silica and silica containing products guidance material.

For specific information on working with engineered stone products refer to the model Code of Practice: Managing the risks of respirable crystalline silica from engineered stone in the workplace.