The control measures that are the most effective for your workplace will depend on your industry, work processes and the risk of exposure.
It is most likely you will need to use a range of control measures to protect your workers from exposure to silica dust. You will also likely need air monitoring and health monitoring programs to confirm your control measures are working and your workers are protected.
Eliminating silica dust
Elimination means you completely remove the hazard from your workplace.
In many cases, eliminating silica dust is not 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.
You can eliminate silica dust at the source by eliminating the processes that generate dust. For example:
- adopting production processes that generate less dust
- for example any wet method is likely to generate less dust than a dry one
- treating the dust at the point of generation, as this is more effective than capturing airborne dust, and
- treating the dust on its transmission path using dust suppression techniques
- for example water sprays, chemical additives, local exhaust ventilation (LEV), vacuum.
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.
Substitution is where you replace a product or chemical 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, and
- use a liquid or paste form of a silica product.
Isolate workers and others from silica dust
Isolation is where you place 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
- 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 use physical methods to change the characteristics of a task. The best engineering controls for your workplace will depend on the tasks your workers carry out.
Engineering controls to control silica dust 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 H-class 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, and
- cleaning up dust with a M or H-class industrial vacuum cleaner.
When considering and using engineering controls, be aware of other hazards that may be introduced. 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.
Silica dust is abrasive and can damage and wear engineering controls. It is important to have a maintenance schedule in place to keep your equipment in good working order. You should regularly inspect your equipment for:
- wear and tear, corrosion or damaged parts
- air leaks in pneumatic tools
- kinks, holes or leaks in water suppression or dust extraction equipment, or
- damage to guards and flaps that contain water spray.
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
Local exhaust ventilation can be used to remove silica dust close to the source before it reaches the breathing zone of a worker.
More information about ventilation and other engineering controls can be found in the model Code of Practice: Managing risks of hazardous chemicals in the workplace.
Engineering controls for silica containing products
Research has found that even when wet methods are used on products that contain high levels of silica that silica dust is not adequately controlled. Applying water to rotating tools can also generate silica contaminated mist that must also be controlled.
For this reason, properly designed water suppression and local exhaust ventilation should be used 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 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
- use hand-held angle grinders fitted with multiple water feeds that deliver water to the cutting disc and the point of contact with the stone
- use water suppressed wet-edge milling machines or polishing machines
- when polishing or grinding stone, use polishers with a centre water feed
- 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 a h class rated vacuum, and
- install fixed, portable or flexible capturing hoods to capture dust at the point of generation.
The use of a handheld spray bottle, sponge or garden hose to separately apply water to rotating tools is inadequate 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
- 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, and
- if you are working outside with wet methods and it is very cold, check for ice hazards.
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
- a job rotation schedule so that the same workers are not continually exposed to silica, and
- restricted area policies so that only staff who are carrying out a task that generates silica dust are allowed access to high risk areas.
Administrative controls when working with silica containing products
If you work with silica containing products, you should develop and implement administrative controls to support the higher level control measures you have in place to protect your workers. These may include:
- shift rotation policies to make sure workers are not exposed to dust above the workplace exposure standard and for extended periods of time
- providing a laundry service for dusty PPE and work wear supported by a policy outlining:
- that dusty PPE and work wear are not to be taken home
- designated areas where dusty PPE and clothes must be changed
- when dusty PPE and clothes must be laundered
- policies for storage, cleaning and maintenance of equipment and PPE that require:
- dusty PPE and equipment to be stored in sealed bags when not in use
- cleaning of PPE and equipment to be done in designated areas only, and
- signage at the workplace highlighting there is a dust hazard and any use of RPE and PPE.
When you are working with silica or silica containing products, you must talk to your workers about silica dust hazards. Training must be provided:
- as part of induction and refresher training
- when a worker will be carrying out a particular task or activity where silica dust is present or could be generated, and
- when significant changes are made at the workplace that change how workers might be exposed.
The information you give to workers during training should give them a good understanding of:
- what silica dust is and health effects
- what controls are in place to protect them
- when they might be at risk of exposure including
- bad work practices, or
- when controls might not be effective, and
- what to do if they observe unsafe practices at the workplace.
You should encourage your workers to report hazards and health and safety problems immediately. This is important because it allows the risks to be managed before an incident or illness occurs.
Good housekeeping can eliminate or reduce exposure to silica dust, even after work has stopped. Developing written rules and policies for your workplace is a good way to implement housekeeping as an administrative control. For example you could require your workers to:
- wet down dusty work areas and processes
- conduct a cleaning schedule for work areas and a maintenance schedule for engineering controls
- for example regularly cleaning dusty vehicle track or high use areas and keep them wet during the day
- carry out daily cleaning procedures for slurry and settled dust
- for example placing wet slurry inside a sealed container for disposal
- never use compressed air, dry sweeping or general purpose vacuum cleaners to clean surfaces or clothing
- use a low pressure water, wet sweeping or a M or H class rated vacuum cleaner to clean dusty floors, walls, other surfaces and equipment, and
- always follow the vacuum manufacturer’s operator manuals and instructions for changing dust bags and filters.
If your workers are outdoors, you can cover the ground with plastic sheeting and remove remaining dust using the above methods.
Dusty clothing and PPE can expose workers and others to silica dust. Examples of how you can minimise exposure to dust carried on PPE and work clothes include:
- using an industrial H class vacuum cleaner to remove dust from clothes and uniforms
- by positioning these units at the exits of dusty work areas, you can encourage workers to vacuum their clothes before leaving
- you should make sure that workers have access to an area to wash their arms, hands, faces and even their hair.
- providing a laundry service for dusty work clothes and PPE so they are not taken home for washing
- if you use a commercial laundry, dampen the clothes and place them in a sealed, labelled plastic bag, and inform the laundry that the clothes are contaminated with crystalline silica
- requiring workers to change dusty clothing after each shift, or if they have just finished a very dusty task to change at their next break, and
- providing workers with rubber boots and aprons.
Worker’s clothes and uniforms must be cleaned frequently to stop silica dust from contaminating break rooms, other parts of the workplace and importantly, to stop workers from taking silica dust home.
More information about facilities at your workplace can be found in the model Code of Practice: Managing the work environment and facilities.
Personal protective equipment
You should never rely solely on PPE to protect workers from silica dust.
Before using PPE you need to do a risk assessment to see what other controls can and should be used. PPE should only be considered after implementing substitution, isolation, engineering and administrative controls. It should only be used to supplement higher-level control measures or when no other safety measures are available.
There are requirements under the WHS laws when it comes to choosing and using PPE.
You must make sure the PPE you provide is appropriate (check the SDS if one is provided) and fits the worker who will be wearing it. This will ensure that the PPE is doing its job. Wrong or ill-fitting PPE means that silica dust can harm your workers. For example the dust can get into worker’s eyes or into the worker’s breathing zone and into their lungs.
You must make sure PPE is clean, hygienic and in good working order. This is so that you do not introduce other hazards to the worker and that the PPE will work as intended. Information about maintaining and cleaning PPE should be sourced from the manufacturer or supplier.
You must provide ongoing training, information and instructions for your workers on how to use, clean and store the PPE you provide. Workers must take reasonable care for their own health and safety. They are expected to follow reasonable instructions and cooperate with any workplace policies you have in place to protect them. Workers must use and wear PPE as instructed by you. However, you must also supervise your workers to check they understand their training and are using the PPE correctly.
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 respiratory protective equipment
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, and
- tight-fitting powered air purifying respirators (PAPR).
There are two types of fit testing that can be carried out:
- a pass/fail test that relies on the wearer’s ability to taste or smell a test agent
- only used on half face respirators, and
- 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, and
- 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, and
- 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, and
- how and where to store RPE when not in use.
Figure 11 Respiratory protective equipment
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, and
- personal hearing protection.
As discussed above, training for workers by a competent person is essential and you should supervise your workers to make sure they understand their training and are using their PPE correctly.
Case study: Stonemason
A stonemason had been regularly working with natural marble and granite products for many years, the granite containing 25 per cent silica.
An occupational hygienist was engaged to measure the worker’s exposure levels in the early days of setting up the business. The worker had regular health monitoring, including an x-ray every five years.
Extraction ventilation systems kept exposures at a level under the workplace exposure standard.
The business model changed due to increased industry demand to using engineered stone products that contained more than 90 per cent silica.
When the silica exposure levels where rechecked, the airborne silica levels were above the workplace exposure standard and the control systems in place needed to be modified to bring exposure back under control.
To manage the risk, a system of wet cutting methods and wearing a powered air purifying respirator with a P2 class filter was introduced.
You can find more information on the Safe Work Australia webpage: Personal protective equipment.