Silica (also known as crystalline silica) is silicon dioxide. It is naturally occurring and can be found in rocks, soils, sand, concrete and mortar.
Where silica is used
Silica is used to make products including:
- composite stone used to fabricate kitchen and bathroom benchtops
- some plastics.
There are non-crystalline and crystalline forms of silicon dioxide.
The most common type of crystalline silica is quartz.
When silica is dangerous
When silica becomes airborne and is inhaled by a worker it is extremely dangerous.
Silica dust is generated in workplace processes such as:
Silica dust can be generated and found:
- during manufacturing and construction
- when mining or tunnelling
- in waste or sand-based products
- in materials brought to your workplace
- 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 percent of crystalline silica)
- foundry casting
- angle grinding, jack hammering and chiselling of concrete or masonry
- hydraulic fracturing of gas and oil wells
- pottery making
- concrete cutting
- dry sweeping respite facilities
- demolition activities.
Some dust particles can be so small that they are not visible, these are referred to as respirable particles. Respirable silica dust particles are small enough to breathe in and penetrate deep into the lungs causing permanent damage that can lead to serious illness or death.
If a worker is exposed to silica and breathes it in they can 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
- 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.
What duty holders need to do
Persons conducting a business or undertaking (PCBUs - employers) or duty holders need to implement control measures to eliminate or minimise generating silica dust in the workplace.
Officers, such as company directors, have a duty to ensure the business or organisation has and uses appropriate resources and processes to eliminate or minimise the risks of working with silica and silica containing products. This includes:
- identifying the hazard of silica dust
- controlling the risk of exposure to silica dust
- conducting air monitoring
- providing health monitoring for workers.
As an employer, when discussing health and safety matters with workers, you should take a consultative approach to allow workers a reasonable opportunity to express views before any decision is made.
Workers have a duty to take reasonable care for their own health and safety and they must take reasonable care that their actions or omissions do not adversely affect the health and safety of other people.
As a worker, you must:
- comply, as far as reasonably able, with any work health and safety instruction from the employer
- cooperate with any reasonable policy or procedure relating to work health and safety that your employer puts in place
- wear personal protective equipment as instructed by the employer and participate in health monitoring, if you have been told about it beforehand. If you refuse, the employer may take action to meet its duties under work health and safety laws – including removing you from the source of exposure.
Workplace exposure standards
Exposure to substances or mixtures in the workplace can occur through inhalation, absorption through the skin or ingestion. Most exposure occurs through the inhalation of vapours, dusts, fumes or gases. For some chemicals, absorption through the skin may also be a significant source of exposure.
Exposure standards have been established in Australia for around 700 substances and mixtures. The standards are updated occasionally and may not always reflect the latest research or state of knowledge on the hazardous effects of chemicals.
Exposure standard means an exposure standard listed in the Workplace exposure standards for airborne contaminants (WES) and represents the airborne concentration of a particular substance or mixture that must not be exceeded. There are three types of exposure standards:
- eight-hour time-weighted average (TWA)
- short-term exposure limit (STEL)
- peak limitation.
The WES for respirable crystalline silica in the Comcare jurisdiction is a TWA of 0.05 mg/m3. The exposure standard was halved from a TWA of 0.1 mg/m3 on 1 July 2020 following agreement by jurisdictional work health and safety ministers and an extensive review by Safe Work Australia.
Hierarchy of controls
Managing risks and worker exposure to silica can be achieved by the following 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, Misting or halo sprays water suppression (wet cutting) or using tools with dust collection attachments.
- administrative controls (should a risk still remain) – including good housekeeping policies, shift rotations and modifying cutting sequences.
- personal protective equipment (should a risk still remain) – including appropriate respiratory equipment (generally a minimum of a P2 efficiency half face respirator) that has been fit-tested by a competent person and work clothing that does not collect dust.
More than one control will normally be required to adequately protect workers.