What is crystalline silica?
Crystalline silica is a natural mineral found in stone products. The table below lists the common stone products and their typical crystalline silica content.
- Engineered stone: 80% to 95%
- Sandstone: 70% to 90%
- Granite: 25% to 60%
- Slate: 20% to 40%
- Marble: Less than 5%
Engineered stone is also known as reconstituted, artificial or manufactured stone, and quartz conglomerate. It is made up of composite stone bound together by resins, and contains at least 80 per cent crystalline silica.
High levels of crystalline silica may also be found in some natural stone products. To find out how much crystalline silica is in a product, check the safety data sheet (SDS) or other information from the supplier.
Stonemasons are exposed to crystalline silica dust
Tasks like cutting, grinding or abrasively polishing stone products release respirable crystalline silica dust – dust particles small enough to breathe into your lungs. This dust may not be visible.
Stonemasons will be exposed to crystalline silica dust, especially when using power tools to cut, grind or polish stone products. In particular, people working in benchtop fabrication are at higher risk, because they regularly do this kind of work with engineered stone, which has a very high crystalline silica content. Uncontrolled cutting, grinding or polishing with power tools can generate dust with very high levels of crystalline silica.
Silica dust can be harmful when it’s inhaled into your lungs over a long period of time at low to moderate levels, or short periods at high levels.
When crystalline silica dust is inhaled it can cause silicosis, a scarring of the lungs. Silicosis is a serious and incurable disease, with symptoms including shortness of breath, coughing, fatigue and weight loss. In severe cases, the damage caused to the lungs by silicosis can require a lung transplant or may lead to death.
Breathing in silica dust can also cause other serious diseases, such as:
- lung cancer
- kidney disease
- autoimmune disease, such as scleroderma.
Safe Work Australia publishes exposure standards for airborne contaminants in the workplace.
The exposure standard for crystalline silica dust (listed under Quartz (respirable dust)) is 0.05 mg/m3 as a TWA (time-weighted average) airborne concentration over 8 hours.
An 8-hour time-weighted average exposure standard is the average airborne concentration of a particular substance permitted over an 8-hour working day and 5-day working week.
The workplace exposure standard for respirable crystalline silica is based on the levels found in a person’s breathing zone, outside of any respiratory protective equipment that may be in use.
Employers are required to ensure employee exposure does not exceed this standard.
WorkSafe Victoria recommends that employees are not exposed to levels above 0.02 mg/m3 as a TWA. This is a precautionary measure to prevent silicosis, and to minimise the risk of lung cancer.
Controlling the risk of exposure
Employers must control the risk associated with exposure to crystalline silica by applying the hierarchy of control in Part 4.1 of the Occupational Health and Safety Regulations 2017 (OHS Regulations).
An employer must, so far as is reasonably practicable, eliminate the risk associated with exposure to crystalline silica in their workplace (for example by using non silica-containing products).
If it is not reasonably practicable to eliminate a risk associated with crystalline silica, the employer must reduce the risk so far as is reasonably practicable by:
- substitution (for example instead of using engineered stone, which can be up to 95% silica, use natural stone, which has a much lower silica content)
- isolation (for example using automation)
- engineering controls (see below) or
- a combination of any of the above risk control measures.
If the risk of exposure still remains after the above risk control measures have been implemented, administrative controls (such as rotation during shifts between high and low exposure tasks) must be used to reduce the risk so far as is reasonably practicable. If a risk remains, an employer must provide appropriate personal protective equipment, such as respiratory protective equipment (RPE), to employees at risk.
You will most likely need more than one control to control the risk sufficiently.
- Required controls when using a power tool to cut, grind or polish engineered stone
A ban on the uncontrolled dry cutting of engineered stone is in effect in Victoria.
Part 4.5 of the OHS Regulations requires an employer, self-employed person or a person who manages or controls a workplace to ensure that a power tool is not used for cutting, grinding or abrasively polishing engineered stone at a workplace, unless the use is controlled.
The use of a power tool will be controlled if it is used with:
- an integrated water delivery system that supplies a continuous feed of water (such as on-tool water suppression), or
- a commercially available on tool extraction system connected to a Dust Class H vacuum or other suitable system that captures the dust generated.
Dust Class H vacuum means a vacuum that complies with the Class H requirements in AZ/NZS 60335.2.69 Household and similar electrical appliances—Safety—Particular requirements for wet and dry vacuum cleaners, including power brush, for commercial use or its equivalent.
If these controls are not reasonably practicable, employers, self-employed persons and persons who manage or control a workplace must control the use of a power tool through local exhaust ventilation (LEV).
Employers, self-employed persons and persons who manage or control a workplace must provide the person who is cutting, grinding or polishing engineered stone with respiratory protective equipment that:
- is designed to protect the wearer from the inhalation of airborne contaminants entering the nose, mouth and lungs, and
- complies with AS/NZS 1716 – Respiratory protective devices.
For more information, see Working with engineered stone (link below).
There are consequences for employers who don't control the risks of dry cutting. If WorkSafe inspectors observe cutting, polishing or grinding without appropriate controls in place, they may issue enforcement notices or take other action. Failing to control the risks of dry cutting is a breach of the OHS Regulations and may be a criminal offence.
- Use of engineering controls to minimise exposure to silica dust
- Respiratory protective equipment (RPE)
- Reducing dust during installation work
- Reducing dust during clean up and housekeeping
- Personal decontamination
- Managing crystalline silica waste
By law, employers must carry out air (atmospheric) monitoring for crystalline silica dust generated at their workplace where:
- there is uncertainty about whether the exposure standard is or may be exceeded, or
- air monitoring is necessary to determine whether there is a risk to employee health, and therefore if health monitoring is required.
There is insufficient evidence to show that any single control or combination of controls is guaranteed to keep exposure to respirable crystalline silica below the exposure standard when power tools are used on engineered stone.
An ongoing air monitoring program is required to confirm that the exposure standard for respirable crystalline silica is not being exceeded. Employers need to conduct ongoing air monitoring, at least once every six months.
In addition to the ongoing schedule, employers should conduct air monitoring:
- when there are changes to work practices, the materials being used or the work environment
- if a health monitoring report for an employee indicates a negative change in health status which may be related to silica exposure
- if an HSR requests a review of control measures
- if there are changes to the workplace exposure standard, and previous air monitoring results have indicated levels above the new standard.
Air monitoring and the interpretation of results (including comparison with the exposure standard) needs to be conducted by a competent person (such as an occupational hygienist) to determine employee exposure to crystalline silica. Results of air monitoring must be shared with employees who have been, or may have been, exposed. Where possible, air monitoring results should be shared with medical practitioners who are conducting health monitoring for employees.
Employers must provide health monitoring if exposure to crystalline silica is likely to have an adverse effect on employees' health.
Due to the high silica content of engineered stone, it is recommended that employers provide health monitoring to all employees who work in the vicinity of engineered stone processing work. This includes, but is not limited to, employees directly involved in engineered stone processing tasks, as well as other employees such as supervisors, labourers, forklift operators, cleaning and maintenance staff, office and sales staff.
Health monitoring must be undertaken by a registered medical practitioner. It needs to be carried out by an occupational physician who is a fellow of the Australasian Faculty of Occupational and Environmental Medicine (AFOEM), with expertise in respiratory and silica exposure health monitoring. A list of practitioners can be found on the Royal Australasian College of Physicians website at racp.edu.au. Employers should speak to the occupational physician to ensure they have experience with silicosis and other silica dust diseases.
Where health monitoring is required, it should be completed when an employee is hired with a new employer (before they start work), regularly while they are in the job and when they finish working for that employer.
For more information on health monitoring see Crystalline silica health assessments (link below).
Crystalline silica: Safety basics
Working with engineered stone
Changes to protect Victorians working with engineered stone
Dust containing crystalline silica in construction work
Crystalline silica health assessments
Dust containing crystalline silica in the extractive industry
AIOH: Find an occupational hygienistExternal link
RACP: Find an AFOEM consultantExternal link