WHAT IS SILICA?

Silica: Crystalline silica, also referred to as quartz, is a common mineral.

Quartz is actually the earths most common mineral and can occur in very small to very large crystals (crystalline) or in fine-grained material with crystals invisible to the unaided eye.

It’s found in soil, sand, granite, concrete, rock, and many other materials.

When natural stone or rock and other silica containing products are cut, crushed, drilled or sanded, dust is released.

The very fine portion of the dust that is generated is known as respirable crystalline silica or silica dust.

What is respirable crystalline silica?

Crystalline silica is the crystalline form of silicon dioxide, a naturally occurring mineral that forms a major component of most rocks.

When dust is created through natural or artificial means it comes in a range of sizes, from very small (less than 10 micrometres [µm] in diameter) to larger particles that can be seen with the naked eye. Dust that is less than 10 µm in diameter (Figure 1) is known as respirable dust as, when inhaled, it travels deep into the lungs.

What are the health hazards associated with silica?

Silica dust is harmful when inhaled into your lungs. As it is 100 times smaller than a grain of sand, you can be breathing it in without knowing.

Exposure to silica dust can lead to the development of lung cancer, silicosis (an irreversible scarring and stiffening of the lungs), kidney disease and chronic obstructive pulmonary disease.

It is estimated that 230 people develop lung cancer each year as a result of past exposure to silica dust at work.

Not all exposed workers will develop cancer; cancer risk increases with long-term or repeated high-level exposure.

Silica dust is a significant health hazard for workers. Very small particles of silica dust cannot be seen under normal lighting or with the naked eye and stay airborne for long periods of time.

When airborne, workers can easily inhale the small silica dust particles deep into their lungs where it can lead to a range of respiratory diseases, including:

• Silicosis
• Progressive massive fibrosis
• Chronic obstructive pulmonary disease
• Chronic bronchitis
• Lung cancer

Silica dust also 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.

Silicosis is a serious, irreversible lung disease that causes permanent disability and can be fatal.

Silica dust can be breathed deep into the lungs and, when silica dust comes into prolonged contact with the lung tissue, it causes inflammation and scarring and reduces the lungs’ ability to take in oxygen.

Silicosis may continue to progress even after a worker is removed from exposure to silica dust. As the disease progresses, a worker may experience shortness of breath, a severe cough or general weakness. There are three types of silicosis:

Acute

• Can develop after short-term and very high levels of silica dust (for example less than one year, and after a few weeks)
• Causes severe inflammation and protein in the lung.

Accelerated

• Results from short term exposure to large amounts of silica dust (1 to 10 years of exposure).
• Causes inflammation, and protein and scarring in the lung (fibrotic nodules).

Chronic

• Results from long term exposure (over 10 years of exposure) to low levels of silica dust.
• Causes scarring of the lung and shortness of breath.

Damage to the lungs from silica dust and symptoms of disease (such as lung cancer, silicosis and progressive massive fibrosis) may not appear for many years. Workers may not show any symptoms, even at the point of initial diagnosis, which is why prevention and health monitoring are critical.

There is no cure for silicosis.

However, all silica dust-related diseases are preventable through using effective controls throughout the lifecycle of the product to eliminate or minimise exposure to silica dust at the workplace.

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Common products containing silica

Silica dust is generated in workplace processes such as crushing, cutting, drilling, grinding, sanding, sawing or polishing of natural stone or manufactured silica containing products.

A label or safety data sheet (SDS) may not always be available at a workplace or with a product that contains silica. If you do not have an information sheet or SDS for a product, you might need to talk to your supplier about whether the product contains silica and how much silica may be present. Common silica containing materials and products include:

• Stone products (natural and engineered)
• Composite dental fillings
• Manufactured timber
• Bricks
• Cement
• Asphalt
• Grout
• Mortar
• Tiles
• Even some plastic material

Activities that release silica dust into the air include:

• Excavation, earth moving and drilling plant operations
• Clay and stone processing machine operations
• Cutting and laying pavers and surfacing
• Mining, quarrying and mineral ore treating processes
• Road construction and tunnelling
• Construction, building and demolition
• Brick, concrete or stone cutting
• 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
• Hydraulic fracturing of gas and oil wells
• Pottery
• Crushing, loading, hauling and dumping of rock, or muck from tunnelling
• Clean-up activities such as sweeping or pressurised air blowing of dust

Fabricating, installing, maintaining and removing silica containing products. Silica dust can be made when cutting, grinding, trimming, polishing, removing or blasting silica containing products or from storing or disposing of dusty waste from these processes.

Mining, quarrying, tunnelling and extractive minerals. Exposure to silica dust is a known issue, with high risks of worker exposure during rock crushing and tunnelling activities. Construction, building and demolition. Silica dust can be formed on site from brick, stone and concrete cutting using power tools.

Who has health and safety duties in relation to working with engineered Silica?

Duty holders with a role in managing the risks of silica dust when working with engineered stone include:

• persons conducting businesses or undertakings (PCBUs)
• officers
• designers, manufacturers, importers, suppliers
• workers
• WHS service providers
• other persons in the workplace

A person can have more than one duty and more than one person can have the same duty at the same time. Person conducting a business or undertaking (PCBU) WHS Primary duty of care When working with Silica, a PCBU must eliminate risks arising from exposure to silica dust or, if that is not reasonably practicable, minimise the risks so far as is reasonably practicable to workers and other persons at their workplace.

The WHS Act requires that a PCBU ensures, so far as is reasonably practicable, the provision of any information, training, instruction and supervision that is necessary to protect all persons from risks to their health and safety arising from work with silica that is carried out as part of the conduct of the business or undertaking.

A PCBU must ensure that information, training and instruction provided to a worker are suitable and adequate and have regard to:

• the nature of the work carried out by the worker
• the nature of the risks associated with the work at the time the information, training and instruction is provided
• the control measures implemented

A PCBU must also ensure, so far as is reasonably practicable, that information, training and instruction are provided in a way that is readily understandable by any person to whom it is provided.. Workers must be trained and have the appropriate skills to carry out tasks safely.

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Risk:

A risk assessment will help you determine how serious the risk posed by the hazard is, what action is necessary to control the risk, and who is responsible for implementing the control measure.

A risk assessment should be carried out if any of the following apply:

• there is uncertainty about how a hazard may result in a harm
• the work activity involves several different hazards
• there is any lack of understanding of how these hazards may interact with each other

Risk assessments should consider:

• the effectiveness of existing control measures
• how work is undertaken in the workplace
• maintenance and cleaning
• breakdowns of equipment
• failures of health and safety controls

The assessment should also:

• identify the type and potential severity of the harm
• consider the number of people potentially exposed to the hazard
• work out the likelihood of harm occurring
• consider how frequently the task involving the hazard is done or how close people are to a hazard

If you have identified silica dust at your workplace or identified that it may be generated as part of your work practices, you should consider:

• how, where and for how long workers could be exposed to silica dust
• the control measures you have in place to control the dust
• the ways you can assess how well your control measures work

When assessing risk, you should consider if there are other airborne contaminants (fumes or mists) that workers could also be exposed to. It is important to consider if the control measures protect your workers from all possible exposures.

If your workers are cutting, grinding, sanding, drilling and polishing silica containing products or carrying out any activities that release silica dust into the air, then there is a significant risk that without effective controls they will be exposed to silica dust and develop an illness or silica-associated disease.

If your workplace has any work practices that generate dust from silica containing materials, there is a significant risk to the health of your workers and others who may be exposed.

Some tools and processes release more silica dust into the air than others. Some silica containing products contain very high levels of silica and are considered to pose a significant risk to the health of workers who work with them.

Workers who use hand tools to cut or grind silica containing materials (such as circular saws or grinders) can have some of the highest exposures to silica dust. These tools are often used to complete fabrication and installation tasks including cutting holes for sinks and stove tops for installation of natural stone benchtops or during shaping and joining of stone pieces.

For further information about working with engineered stone products, including on-site installation requirements, please refer to the model Code of Practice: Managing the risks of respirable crystalline silica from engineered stone in the workplace

When controlling silica dust exposure the hierarchy of control must be used:

Elimination

The first thing you must consider is whether a risk can be completely removed from the workplace.

If it is reasonably practicable, eliminate the silica containing products from your workplace. This will effectively remove the risk of workers being exposed to silica dust when working with these products.

In many cases, eliminating silica containing products may not be reasonably practicable. Elimination may not be possible if silica dust is naturally occurring at your workplace or you can’t make the end product or deliver a service without generating it.

If it is not reasonably practicable to eliminate the risk, then risks must be minimised, so far as is reasonably practicable, using the hierarchy of controls.

Substitution

Substitution is where you replace a product with something that is less hazardous and therefore has a lower risk.

Effective substitution of silica and silica containing products will depend on your workplace and the work tasks your workers carry out. Again, substitution might not be practicable where silica is naturally occurring or if it means you can’t make the end product or deliver a service.

Substitution can be an effective way of managing the risk of exposure to silica dust. For example, you can:

• use products that do not contain silica or have less silica in them
• use a silica containing product that does not need to be cut, ground or polished

Isolation

Isolation involves physically separating the source of harm from people.

This may involve placing barriers or distance between a hazard and your workers.

Isolation is an effective way of protecting your workers from exposure to silica dust. Physical barriers that remove the worker from contact with silica dust are the most effective form of isolation controls.

Isolation controls include:

• isolating high dust generation work processes within an enclosed room with restricted access

An example of an isolation booth used for automated wet cutting

• providing physical barriers and exclusion zones between different workers and workstations to prevent dust or water mist from moving into other work areas or towards other workers
• distancing a work process from other workers
  • for example, consider where other workers are working when powered hand tools are used
• designating a room or area for other tasks such as changing or eating, away from the work area

You can also use barriers around automated tasks to shield workers from silica dust.

Wherever possible, workers should not fabricate silica containing products at the installation site. If modifications at the installation site need to be made, this work should be done outdoors in a designated area, wearing appropriate PPE and using engineering controls, including wet methods and dust collection systems.

Engineering controls

Engineering controls use physical methods to change the characteristics of a task, including mechanical devices or processes that eliminate or minimise the generation of dust and minimise it becoming airborne. Engineering controls to control silica dust can include:

• automation when cutting, grinding or drilling, using wet cutting methods, local exhaust ventilation
• drills, routers, saws and other equipment designed to be fitted with local exhaust ventilation and a water attachment to suppress dust using sacrificial backer-boards or spoil boards, fitting large machinery such as excavators and bulldozers with positive pressure enclosed cabs
• cleaning up dust with a M or H-class industrial vacuum cleaner

As many engineering controls are motorised you should be aware of noise and vibration levels at your workplace and issue personal hearing protection as needed.

Administrative controls

Administrative controls should only be used to provide additional protection and must only be considered after implementing substitution, isolation and engineering controls.

Administrative controls rely on worker behaviour and it is very important to have administrative policies and worker training when silica is identified at your workplace. You also need to supervise your workers to make sure they understand and follow your administrative policies.

Examples of administrative controls for silica dust include:

• planning cutting tasks to make sure the minimum number of cuts are made
• written rules and policies for working with silica or cleaning silica waste
  • for example, having a written clean-up procedure and log
• a maintenance schedule and log for equipment and PPE
• shift rotation policies to make sure workers are not exposed to dust above the workplace exposure standard and for extended periods of time
• restricted area policies so that only staff who are carrying out a task that generates silica dust are allowed access to those areas
• signage at the workplace highlighting there is a dust hazard and any required use of RPE and PPE

Personal protective equipment

Personal protective equipment (PPE) is the least effective method for controlling risks. However, it can be effective at minimising residual risk when used in conjunction with higher order controls. Before working with silica containing products, a PCBU, the principal contractor or person in control of the workplace should assess the conditions likely to affect the health and safety of workers and arrange for the provision and use of appropriate PPE.

Fit testing should be repeated on a regular basis and based upon the outcomes of a risk assessment (e.g. every one or two years). For RPE to be effective, workers who are required to wear tight-fitting respirators must be clean shaven. If they cannot be clean shaven, ensure:

• there is no hair between their face and the seal of the respirator face piece as it can interfere with a proper fit. This is important as silica dust is smaller than facial hair
• facial hair does not interfere with the inhalation/exhalation valve operation

Respiratory protective equipment (RPE)- As silica dust particles are very small, workers should use a tight-fitting respirator with an effective face seal. This means they need to be clean-shaven or only have facial hair that does not interfere with the fitting surfaces or the respirator valve. As everyone’s face is a different size and shape, there is no ‘one size fits all’ tight-fitting respirator. This means that you should also fit test each worker and their RPE before they undertake dusty work. For workers who want to keep facial hair that may interfere with the operation or proper fit of tight-fitting respirator (for example a closely trimmed beard), a powered air purifying respirator with a loose hood may be suitable.

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Ventilation is a very effective engineering control when designed correctly. There are a range of different ventilation systems and you need to use the ones that suit your workplace and the tasks your workers carry out.

Local exhaust ventilation can be used to remove silica dust close to the source before it reaches the breathing zone of a worker.

Figures 5-7 show on tool dust extraction and local exhaust ventilation.

More information about ventilation and other engineering controls can be found in the model Code of Practice: Managing the risks of respirable crystalline silica from engineered stone in the workplace and the model Code of Practice: Managing risks of hazardous chemicals in the workplace.

For this reason, properly designed water suppression and local exhaust ventilation may be required in combination when working with these products. It is important to:

only use tools and machinery that have been specifically designed for use with water attachments with the appropriate ingress protection (IP), for example:

• when cutting natural stone slabs, use bridge saws fitted with water attachments to suppress dust
• to complete sink and stovetop cut outs, use water suppressed routers, water jet cutters or bridge saws
• for brick and concrete cutting, use hand-held power tools fitted with multiple water feeds that deliver water to the cutting blade and use water suppressed wet edge milling machines or polishing machines
• use an adequate number of water feeds to prevent visible dust during the process
• maintain adequate water pressure (0.5 L/min or as specified by the manufacturer) to make sure water is reaching the product or tool; control water spray using guards, plastic flaps or brush guards
• prevent workers from being able to turn water suppression systems down or off during operation
• only use tools and machinery that have been specifically designed for local exhaust ventilation attachments such as drills, circular saws and grinders equipped with a shroud and an M- or H- class rated vacuum
• install fixed, portable or flexible capturing hoods to capture dust at the point of generation

suppress dust by using water sprays to reduce airborne dust and dust clouds (for example, during earthworks, on stockpiles and roads, and when using machinery and cutting equipment).

The use of a handheld spray bottle, sponge or garden hose to separately apply water to rotating tools is not adequate to suppress silica dust.

Wet methods of fabrication can introduce other hazards to your workplace. When using wet methods consider:

• installing ventilation to control water mist that may carry dust in the mist cloud
• providing waterproof aprons, waterproof, non-slip footwear and eye protection that does not fog up and obstruct worker’s vision
• filtering water that is recycled
• ensuring run-off is effectively drained away from equipment and work areas
• installing non-slip flooring
• implementing housekeeping policies to make sure run-off does not dry to create a dust hazard

Respiratory protective equipment

As silica dust particles are very small, workers should use a tight-fitting respirator with an effective face seal. This means they need to be clean-shaven or only have facial hair that does not interfere with the fitting surfaces or the respirator valve. As everyone’s face is a different size and shape, there is no ‘one size fits all’ tight-fitting respirator. This means that you should also fit test each worker and their RPE before they undertake dusty work.

For workers who want to keep facial hair that may interfere with the operation or proper fit of tight-fitting respirator (for example a closely trimmed beard), a powered air purifying respirator with a loose hood may be suitable.

Fit testing measures the effectiveness of the seal between the respirator and the wearer’s face.

Workers should pass a respirator fit test before they first start wearing a tight-fitting respirator including:

• half face disposable
• half face reusable
• full face reusable
• tight-fitting powered air purifying respirators (PAPR)

There are two types of fit testing that can be carried out:

• Qualitative
  • a pass/fail test that relies on the wearer’s ability to taste or smell a test agent
  • only used on half face respirators
• Quantitative
  • uses specialised equipment to measure how much air leaks into the respirator
  • used on half face respirators, full face respirators and PAPR

Quantitative fit testing results are more objective than qualitative testing because some workers have difficulty with their ability to taste or smell. This can result in a ‘false pass’ and worker health not being adequately protected.

It is recommended that full face respirators and PAPR are fit tested using the quantitative method.

All fit testing must be carried out by a competent person, manufacturer, supplier or consultant:

• before a worker wears a tight-fitting respirator for the first time
• each time a new make or model of respirator is provided to a worker
• whenever there is a change in the wearer’s facial characteristics or features that may affect the seal (e.g. large weight loss or gain)

Fit testing should be repeated on a regular basis and based upon the outcomes of a risk assessment (e.g. every one or two years).

Keep a written record of fit tests carried out for each worker including the:

• type of test performed
• make, model, style and size of respirator tested
• date and result of the test

Issue your workers with a fit test record card after fit testing.

You must provide training for your workers who are provided with RPE. This is to make sure they fit, use and maintain the RPE they are expected to use. Training must be provided by a competent person; this could be a consultant, someone in house or a representative from a RPE manufacturer or supplier.

Good training for RPE should cover:

• why the RPE is required for their job
• when the worker should and must wear the RPE
• how the RPE works
• the limitations of the RPE
• how to correctly put on and take off the RPE
• how to fit check
• how to clean and maintain the RPE
• when and how to replace the filters
• how and where to store RPE when not in use

Full face respirator (cartridge)

Reusable half-face respirator.

Full face Powered Air Purifying Respirator (PAPR)

Full face Powered Air Purifying Respirator (PAPR)

PPE when working with silica containing products

Respiratory protective equipment is not enough to protect your workers from silica dust.

Due to the high levels of silica in engineered stone products, a combination of controls are required to protect workers’ health including engineering, isolation, work practices, personal protective equipment, worker training and consultation.

It is recommended that for workers using hand held water fed equipment to wear a full face respirator with a P3 class filter or a full face PAPR with a P2 class filter.

Fit testing is essential to make sure the respirator works correctly and is comfortable to wear with any other PPE that may be needed for the task. This may require seeking advice from suppliers or manufacturers.

The PPE you select must also be appropriate for other risks that might arise when working with silica containing products such as:

• eye protection
• aprons, foot wear and gloves
• hard hats
• personal hearing protection

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Participant Evaluation Part I