Crystalline silica and silicosis
This page provides information for a person conducting a business or undertaking (PCBU) and workers about silica and some of the legal duties relating to protecting workers from developing silicosis.
Crystalline silica (silica) is found in sand, stone, concrete and mortar. It is also used to make a variety of products including composite stone used to fabricate kitchen and bathroom benchtops, bricks, tiles and some plastics. When workers cut, crush, drill, polish, saw or grind products that contain silica, dust particles are generated that are small enough to lodge deep in the lungs and cause illness or disease including silicosis.
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 silica, for example:
|Granite||25 to 40%|
|Composite (engineered or manufactured stone)||>90%|
|Aggregates, mortar and concrete||Various|
What is silica dust?
Silica dust 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. Some dust particles can be so small that they are not visible; these are commonly referred to as respirable particles.
Respirable silica dust particles are small enough to penetrate deep into the lungs and can cause irreversible lung damage.
The non-crystalline or amorphous forms of silica do not cause this kind of 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 respirable silica dust particles include:
- during fabrication and installation of composite (engineered or manufactured) 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
- construction labouring activities
- brick, concrete or stone cutting; especially using dry methods
- abrasive blasting (blasting agent must not contain greater than 1 per cent of crystalline silica)
- foundry casting
- angle grinding, jack hammering and chiselling of concrete or masonry, and
- pottery making.
What diseases can silica dust cause?
If a worker is exposed to and breathes in silica dust they could develop:
- chronic bronchitis
- 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 and causes fibrotic nodules and shortness of breath
- can include progressive massive fibrosis where the fibrotic nodules in the lung aggregate
- lung cancer
- kidney damage, or
- 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 Work Health and Safety (National Uniform Legislation) Regulations 2011, 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 sourcing composite stone benchtops with a lower percentage of 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
- should a risk still remain; administrative controls, including good housekeeping policies, shift rotations and modifying cutting sequences
- should a risk still remain; personal protective equipment including appropriate respiratory 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.
The workplace exposure standard
The workplace exposure standard for respirable crystalline silica that must not be exceeded is 0.1 mg/m3 (eight hour time weighted average).
PCBUs should keep worker exposures to respirable silica dust as low as reasonably practicable. Air monitoring will need to be conducted If there is any doubt that the exposure standard is being exceeded or to find out if there is a risk to a worker’s health.
This exposure standard has been reviewed as a priority by Safe Work Australia as part of the review of the workplace exposure standards.
Health monitoring for workers exposed to silica
Under the Work Health and Safety (National Uniform Legislation) Regulations 2011, PCBUs must provide health monitoring for workers if they carrying out ongoing work using, handling, generating or storing crystalline silica and there is a significant risk to the worker’s health because of exposure.
Further information about the duties for health monitoring can be found here:
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).