Silica dust is not just dust

Silica dust, also known as crystalline silica, is a naturally occurring and widely abundant mineral that forms the major component of most rocks and soils. Because of this, silica can be found in construction materials such as bricks, tiles, concrete, mortar, engineered stone, and some plastic material. When these materials are worked on, silica is released into the air as a fine (sometimes invisible) dust known as silica dust. Silica dust is 100 times smaller than a grain of sand, making it very easy for you to be breathing it in without knowing. Work activities that may pose a high risk of exposure include cutting, jackhammering, grinding, sanding, blasting, drilling, loading, or demolishing products that contain silica.

How can silica dust affect your health?

Silica is harmful when inhaled into the lungs over a long period at low to moderate levels, or short periods at high levels. Several health issues can be the result of silica dust inhalation, including; lung cancer, kidney disease, autoimmune diseases such as scleroderma, and silicosis. Silicosis is a serious and incurable disease whose symptoms include shortness of breath, coughing, fatigue, and weight loss. In severe cases, the damage caused by silica dust inhalation can require a lung transplant or may lead to death.

Prolonged exposure to silica dust has been linked to several types of cancer. Workers in different trades face increased risk of specific illnesses.

Where is silica dust found?

Silica dust is a widely abundant mineral that forms the major component of most rocks and soils. It can be found in construction materials such as bricks, tiles, concrete, mortar, engineered stone, and some plastic material. It is important to understand that the amount of crystalline silica present in products varies, some containing much more silica than others.

If you are unsure at any time if a product contains crystalline silica, or how much silica a product contains, check the safety data sheet (SDS) or other information from the product’s supplier.

Hierarchy of control

The hierarchy of control for silica was established to provide risk management controls to ensure that suitable measures are in place to protect your safety.

Ordered from highest level of health and safety protection and most reliable control measure, to lowest level of health and safety protection and least reliable control measure, the hierarchy of control works as follows:

Elimination
Stop work on materials containing silica to prevent silica dust being released into the air.

Substitution
Substitute materials with high silica content such as engineered stone to those with a low content such as marble or natural stone.

Engineering
Use wet cutting methods, HEPA filters on tools, air extraction on machinery, to remove the dust that is created before it has a chance to get into your lungs.

Engineering controls:

  • Install a water hose to wet down the dust at the point of generation
  • Install local exhaust ventilation
  • During rock drilling, flow water through the drill stem
  • Install dust collection systems onto machines or equipment that generates dust
  • Use concrete/masonry saws that provide water to the blade

Administrative
Make sure all of the cutting of materials containing silica is performed in the factory where the exposure to silica dust can be more controlled.

PPE
Wear a fitted and approved dust mask for the task.

Using on-tool water suppression

On-tool water suppression is a system that fits directly onto a tool and uses water to minimise the amount of dust generated. It also keeps cutting blades and grinding discs cool. Each part of the system is critical to the system’s effectiveness and level of dust control. You can buy a complete on-tool water suppression system or, alternatively, parts of the system to use with your existing tools. Make sure to choose parts that are compatible with your tools.

Water source
Use fresh water. Do not use water that has previously been used to suppress crystalline silica dust. Where mains water is not available, use a pressurised water bottle.

Shroud
The shroud directs water onto the tool and limits the amount of dust generated. It is often part of the tool but can also be retro-fitted to existing equipment. Poor design or damage to the shroud will significantly affect dust control.

Hose
The hose connects the water supply to the shroud. Check that the hose is made of durable material, is the right size (diameter and length) for the work and fits securely to the shroud and water supply.

Regular checks/maintenance
Maintain and operate the on-tool water suppression system according to the manufacturer’s instructions. Ensure the system works properly every time. It is good practice to carry out and record regular maintenance on tooling, to perform visual checks prior to use, and to tag ‘out of use’ and quarantine any faulty equipment.

Inspection and testing
Equipment needs to be properly serviced and tested to ensure it remains effective. For more information, contact the manufacturer or supplier

Using on-tool dust extraction

On-tool extraction is a type of local exhaust ventilation system which is fitted directly onto the tool. The system has several parts and each part is critical to the system’s effectiveness and level of dust control. Complete on-tool extraction systems are available but some parts (especially extraction units) can be used with other tool makes and models. For effective dust control, it’s important to choose parts that are compatible.

Captor hood
The hood captures the dust as it’s produced and is the most important part of the system. It’s often manufactured as part of the power tool but can also be retro-fitted to existing equipment.
Poor design or damage to the hood will significantly affect dust control. Check that the hood:

  • is designed for the tool and the task (seek guidance from the manufacturer or supplier)
  • sits as close as possible to the work surface when in use, as dust will escape through any gaps
  • is easy to use and doesn’t interfere with the work unnecessarily.
  • Ensure the unit is emptied regularly and safely.
  • Check that the unit has enough waste capacity for the task.

Extraction Unit
The extraction unit is like an industrial vacuum. It removes dust from the captor hood, filters it, and collects it for safe disposal.
The extraction unit should be suitable for the toxicity level and hazardous nature of the dust being extracted, as well as its size and type. Manufacturers of construction material can advise whether the dust produced by their products is classified as L (Low), M (Medium), H (High) class or non-hazardous.

  • L class – dust representing a low risk
  • M class – dust representing medium risk
  • H class – dust representing high risk.

For silica dust, use an H-class vacuum cleaner fitted with a filter that can achieve an efficiency of 99.995% (e.g H14 HEPA filter). Do not use a household vacuum cleaner to remove this dust. Lots of fine dust can quickly clog filters. Choose a unit with pre-filters, built-in ‘back-flushing’ filter cleaning mechanisms, or similar devices.

Regular checks/maintenance
Maintain and operate the on-tool dust extraction system according to the manufacturer’s instructions. Ensure the system works properly every time. It is good practice to carry out and record regular maintenance on tooling, to perform visual checks prior to use, and to tag ‘out of use’ and quarantine any faulty equipment. You may have to do checks more frequently if there is a high risk of the equipment being damaged.

Inspection and testing
Equipment needs to be properly serviced and tested to ensure it remains effective. For more information, contact the manufacturer or supplier

Using Respiratory Protective Equipment (RPE)

A risk assessment should be done to determine what other controls are in place before using Respiratory Protective Equipment (RPE). The use of RPE should only be used to supplement substitution, isolation, engineering, and administrative controls.

Wear an appropriate mask for the task at hand
A risk assessment will identify which jobs present the highest risk of silica dust exposure. The control measures that are the most effective for your workplace will depend on the task at hand and the risk of exposure.

Tasks ranked VERY HIGH present elevated risk of exposure to silica dust. Activities such as below-ground tunneling, concrete cutting/sawing, concrete grinding, jackhammering, or chiseling may require a half-face fitted mask.

Activities ranked a HIGH risk may include concreting, drilling, excavating, general demolition, operating a skid steer, or sweeping. P2 masks may be required alongside other controls such as on-tool dust extraction or water suppression.

RPE needs to comply with AS/NZS 1716. If you are ever unsure about the type of mask that is best suited for the task you are undertaking, contact your employer.

Ensure your mask is fitted well
As silica dust particles are very small, you should use a tight-fitting respirator with an effective face seal. This means you 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 a fit test should be conducted before any work is undertaken around dust.

Regular checks/maintenance
Maintain respiratory protective equipment according to the manufacturer’s instructions. Ensure the mask is fitted well and works properly every time. You may have to do checks more frequently if there is a high risk of the equipment being damaged..

Inspection and testing
Equipment needs to be properly serviced and tested to ensure it remains effective. For more information, contact the manufacturer or supplier.

References:

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