Silica

Silica is a common naturally occurring mineral, also known as silicon dioxide. Silica can be found in different forms, broadly divided into crystalline and non-crystalline (amorphous).

Crystalline silica is the crystalline form of silicon dioxide that forms a major component of most rocks (e.g., granite, slate, sandstone), soil, sand and clay. One common type of crystalline silica is quartz. It is a component of concrete, some bricks, natural stone products, and engineered stone products. When crystalline silica is subjected to high-speed abrasive processes, such as cutting, grinding and polishing, it gives off very fine particles of crystalline silica dust. These very fine particles can be inhaled deep into the lung and are referred to as respirable. This presents a serious health hazard. Consequently, this hazard can be found in industries such as construction, masonry, mining, and foundries. This information focuses on respirable crystalline silica, which is the most hazardous form.

RCS is classified as a hazardous chemical according to the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) and has a workplace exposure standard. The WHS Regulations include specific requirements for a PCBU to manage the risks associated with hazardous chemicals, including air monitoring and health monitoring.

RCS is a significant health hazard for workers. Very small particles of RCS cannot be seen under normal lighting or with the naked eye and stay airborne for long periods of time. A person exposed to airborne RCS can breathe it deep into their lungs and can lead to a range of respiratory diseases, including:

• 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).
• progressive massive fibrosis
• chronic obstructive pulmonary disease
• chronic bronchitis
• lung cancer.

RCS increases the risk of developing chronic kidney disease, autoimmune disorders (such as scleroderma and systemic lupus erythematosus) and other adverse health effects, including an increased risk of activating latent tuberculosis, eye irritation and eye damage.

Processing of CSS includes the following activities:

• the use of power tools or mechanical plant to carry out an activity involving the crushing, cutting, grinding, trimming, sanding, abrasive polishing or drilling of a CSS
• the use of roadheaders to excavate material that is a CSS
• the quarrying of a material that is a CSS
• mechanical screening involving a material that is a CSS
• tunnelling through a material that is a CSS
• a process that exposes, or is reasonably likely to expose, a person to respirable
• crystalline silica during the manufacture or handling of a CSS.

Note: Dust can contain not just RCS but many other substances that are hazardous to health. Exposure to all dust needs to be eliminated so far as is reasonably practicable.

As a business, you must manage your workers’ exposure to RCS dust and put measures in place to keep workers safe and healthy. This includes, but is not limited to, eliminating or minimising the risks of exposure to RCS when working with a CSS. In addition to your usual responsibilities and duties under WHS there are specific laws that require you to protect workers exposure to RCS.

Workplace exposure standard

A PCBU must ensure that no person at the workplace is exposed to RCS, at a concentration above the workplace exposure standard. The workplace exposure standard for RCS is an eight hour time weighted average (TWA) of 0.05 milligrams per cubic metre (mg/m³). 

More information is available on the Safe Work Australia webpage Guidance on interpretation of Workplace exposure standards for airborne contaminants.

Air monitoring

Air monitoring involves measuring the level of RCS in the breathing zone of workers by using a personal sampler during their usual shift activities (including routine breaks). Air monitoring is important to:

• check the effectiveness of control measures
• monitor the workplace atmosphere to ensure the workplace exposure standard is not being exceeded
• help choose the right level of respiratory protection
• inform health-monitoring requirements.

Air monitoring results must be kept for 30 years after the record is made and be readily available to those who may be exposed to the substance or mixture in the workplace.

In assessing any processing of a CSS, you must have regard to the results of any previous air monitoring that has been conducted at that workplace that are relevant to the task, controls and conditions in your workplace. If you do not have any previous air monitoring results, this does not prevent you from determining whether the processing of a CSS is high risk, rather you must undertake your assessment considering all the matters.

Some businesses and industries, such as the stone-benchtop industry have specific air monitoring requirements that are outlined in the Managing the risks of respirable crystalline silica from engineered stone in the workplace: Code of practice.

Health monitoring

Health monitoring of a worker means monitoring the worker to identify changes in their health because of exposure to certain substances. It involves collecting data to measure exposure or evaluate its effects and determine whether the absorbed dose is within safe levels.

A PCBU must organise and pay for health monitoring if there is a risk to the health of their workers because of exposure to silica dust at the workplace. Health monitoring identifies any changes to the health of workers resulting from exposure to respirable crystalline silica (RCS).

Under WHS Regulations, the minimum requirements for health monitoring for crystalline silica through exposure to silica dust are:

• collection of demographics, medical and occupational history
• records of personal exposure
• standardised respiratory questionnaire
• standardised respiratory function tests, for example, FEV1 (forced expiratory volume in one second), FVC (forced vital capacity) and FEV1/FVC (respiratory ratio, or Tiffeneau index)
• low dose high resolution computed tomography of the chest at less than 1 millisievert (mSv) equivalent dose for the entire study. The study must image the whole of each lung on inspiration at 1.5 mm slice thickness or less, without an interslice gap, and must include expiratory imaging. The images must be of adequate quality to detect subtle abnormalities, including ground glass opacities and small nodules.

The registered medical practitioner who prepares the health monitoring report must give the regulator a copy if the report contains monitoring results consistent with exposure to silica. When conducting the assessment to determine if the processing of CSS is high risk, you must consider the results of any relevant health monitoring that has been previously conducted at the workplace.

More information on health monitoring of workers for exposure to crystalline silica can be found in the Health monitoring guide for registered medical practitioners: Silica (respirable crystalline)

Health monitoring records must be kept confidential and for at least 30 years after the record is made, even if the worker no longer works at the workplace.

Information about health monitoring reports is available in the Health monitoring duties for persons conducting a business or undertaking: Guide.

Providing information, training, instruction and supervision

The business must provide training for carrying out processing of a CSS:

• as a part of induction and refresher training
• to a worker who will be carrying out a particular task or activity where RCS is present or could be generated, and
• when significant changes are made at the workplace that change how workers might be exposed to RCS.

Take care of your own health and safety

As a worker, you must take reasonable care for your own health and safety and not adversely affect the health and safety of others. You must comply with any reasonable WHS instructions given by the PCBU, such as participating in health monitoring and wearing relevant personal protective equipment, and cooperate with any reasonable policy or procedure relating to WHS at the workplace that has been notified to you.

Wear and correctly use personal protective equipment

You must wear and correctly use personal protective equipment if it is provided. Ask for a replacement if it is damaged or needs to be cleaned.

The following examples give an indication of the varying levels of crystalline silica in different products:

• engineered stone: up to 97%
• sandstone: 70–90%
• granite: 25–60%
• ceramic tiles: 5–45%
• autoclaved aerated concrete: 20–40%
• Slate: 20–40%
• concrete: less than 30%
• porcelain: 14–18%
• brick: 5–15%
• marble: 2%

You can check safety data sheets and other information from suppliers to find out whether products contain crystalline silica.

Identify where and how dust from these products is being released at your place of work. This may be achieved by:

• conducting a walk-through assessment of the workplace
• observing the work and talking to workers and/or HSRs about how work is carried out
• inspecting the plant and equipment that is used as part of the fabrication and other relevant processes – for example, hand-held tools may generate more silica dust than automated machinery
• undertaking air monitoring at the workplace
• inspecting workplace surfaces for build-up of settled dust, and
• reading product labels, safety data sheets and manufacturers’ instruction manuals.

A risk assessment involves considering what could happen if a worker is exposed to a hazard and the likelihood of it happening. Exposure to silica dust can adversely affect a worker’s health, including developing silicosis, progressive massive fibrosis, chronic obstructive pulmonary disease, chronic bronchitis, and lung cancer.

A PCBU must assess the processing of a CSS carried out by the business or undertaking at the workplace to determine if the processing is high risk. This assessment must consider the the forms of crystalline silica present in the CSS, it's concentration (weight/weight), hazards associated with work including frequency and duration of exposure, any relevant air or health monitoring details,

If you have identified silica, assess the risks by carrying out a risk assessment. 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 (e.g. 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.

Silica risk control plan

A silica risk control plan is a practical tool to document the specific tasks and control measures related to each processing of a CSS that is high risk carried out by the PCBU. If you have assessed the processing of a CSS, or a combination of processing of a CSS, as being high risk, you must develop a silica risk control plan covering those processing tasks. This must be available for all workers to access before they commence the processing of a CSS. A template for a silica risk control plan is provided in the Working with crystalline silica substances: Guide or refer to completing a silica risk control plan by Safe Work Australia.

• 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 (e.g. 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 (e.g. for mixing, crushing, milling, drilling or chasing)
• shadow vacuuming (e.g. 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

Further guidance on the risk management process and the hierarchy of control measures is available in the How to manage work health and safety risks: Code of practice.

You should regularly review your control measures to make sure they remain effective for managing your workplace risks.

For example, a PCBU should conduct daily start up checks to ensure that:

• machine and water mist guards and LEV are fitted correctly and are working effectively
• LEV filters are clean and replaced according to the manufacturer’s instructions
• there is an adequate water supply for water suppression
• all respiratory protective equipment (RPE) is in good, working condition and fit checked.

A PCBU should routinely monitor the workplace for signs of visible dust on work surfaces or clothing as that may be an indication that some controls are not working effectively.

Further guidance on the risk management process is available in the How to manage work health and safety risks: Code of practice..

Further guidance on how to effectively manage risks associated with working with engineered stone and, subsequently, minimise the incidence of respirable crystalline silica related diseases, such as silicosis is available in the Managing the risks of respirable crystalline silica from engineered stone in the workplace: Code of practice.

From 1 July 2024 the use of engineered stone will be banned in Western Australia. You can read about the announcement below.

• Engineered stone banned and national labour hire scheme endorsed | Western Australian Government (www.wa.gov.au)

Note: Western Australia will join the rest of the country in banning the use of engineered stone in workplaces due to the risk to workers of silicosis. To find out more about the ban, visit the Engineered stone ban webpage.