What is Crystalline Silica Dust?
Crystalline silica is one of the most abundant minerals in the earth's crust and is a major constituent of construction materials such as bricks, tiles and concrete.
Crystalline silica consists of silicon and oxygen atoms (SiO2) arranged in a regular crystalline structure. There are different crystalline forms of silica, with the most common being quartz. In some circumstances, for example in the high temperatures of industrial furnaces and kilns, quartz may convert to another crystalline form of silica known as cristobalite. Quartz is found in varying amounts in almost all types of rock, sands, clays, shales and gravel. For example, sandstone is almost pure quartz, whereas granite might contain 15-30% quartz.
Exposure to silica dust causes many problems not only to miners and quarry workers, but also to workers in certain types of construction and demolition work, as well as those working in art rooms.
Silica dust is so fine it can enter the deepest parts of the lungs. This dust can build up in the lungs and scar them - leading to a number of diseases (see more information, below).
Action Plan for Health and Safety Reps
A strategy to prevent work related injury and illness must be aimed at modifying the workplace - controlling the hazard at source - rather than modifying, screening or excluding workers from the workplace.
As an OHS rep, you need to make your members aware of the risks of exposure to silica and ensure that the employer complies with his/her duties under the legislation to eliminate or reduce the risks.
- Check that materials used for abrasive blasting DO NOT contain more than 1% silica.
- Equipment used for cutting, grinding, etc. should be fitted with dust extraction devices.
- Where dust extraction is not practical, wet methods should be utilised.
- Unfortunately, for many jobs, some form of respiratory protection will be required. The type of respirator will depend on the amount of dust created by the process. Ensure the workers are thoroughly trained in the use and maintenance of respiratory protective devices. This training must be provided by an appropriately trained person before workers are required to use the PPE.
- Where there is likely to be excessive dust, all other workers should be cleared from the area so as prevent any unnecessary exposure.
- The removal of residual dust generated by the work process must be done in a manner that will not make the dust airborne.
It is important that there be monitoring of silica dust levels generated by the activity. The results can then be used to establish effective control methods in work practices and ensure that they remain effective. It is important that an approved workplace consultant who can also provide advice on workplace control strategies do monitoring. Contact your union for further advice.
Silica is classified as a hazardous substance and is therefore regulated under Chapter 4 - Hazardous Substances and Materials - of the 2007 Occupational Health and Safety Regulations. This means that the employer has the legal duty to identify the hazard and eliminate or control any risk, provide information and training , undertake atmospheric monitoring, maintain records and, in the case of crystalline silica, carry out health surveillance.
On 1 January 2002, the use of materials containing more than 1% crystalline silica for abrasive blasting was prohibited in all Victorian workplaces. The prohibition was made under the then Occupational Health and Safety (Hazardous Substances) Regulations 1999. This means materials such as silica sand, river sand, beach sand and other white sands must not be used for abrasive blasting. The WorkSafe website has more information on the ban.
More information on the duties of the employer under Part 4.1 - Hazardous Substances - of the OHS regulations.
The National Occupational Health and Safety Commission (NOHSC - now SafeWork Australia) has revised the exposure standards for the three forms of crystalline silica, quartz, cristobalite and tridymite. The revised national exposure standards for the three forms are 0.1 mg/m³ (time weighted average, 8 hours). (This is half the previous standard, which was 0.2 mg/m³.) The revised standard came into effect January 1, 2005.
More information on silica and its effects
The following activities create silica dust:
- Brick cutting and chasing.
- Angle grinding on concrete or masonry.
- Concrete cutting. Jack hammering, scabbling and chiselling of concrete.
- Cleaning up of dust and debris created by the above activities.
Workers at risk include those involved in:
- building, construction and demolition work
- excavation work
- abrasive blasting (but use of silica in abrasive blasting is now prohibited in Victoria - see below)
- mining, quarrying, crushing and tunnelling work
- brick making and glass making
- road building
- foundry or casting work
- explosives blasting work
- art workers, including teachers and cleaners
- jewellery workers (particularly in developing countries)
What are the health effects of exposure to silica dust?
The following diseases are caused by excessive exposure to airborne silica dust:
- Acute silicosis (rapid development after short exposure to high concentrations of silica dust).
- Silicotuberculosis (silicosis sufferers are at a higher risk of developing tuberculosis)
Silica dust, along with other atmospheric contaminates, can also cause or exacerbate these diseases:
- Simple chronic bronchitis;
- Chronic airway obstruction;
- Lung cancer.
What is silicosis?
Silicosis is a serious disease of the lungs caused by breathing in crystalline silica dust. Crystalline silica is a basic component of soil, sand, granite, and many other minerals (a common type is quartz). It can become respirable dust when workers chip, cut, drill, or grind objects that contain crystalline silica. In addition, the practice of using sand and other materials containing silica for abrasive blasting led to the creation of high levels of crystalline silica dust.
Silicosis can be disabling or even fatal. There are three types of silicosis:
- Chronic/classic silicosis - this is the most common form and occurs after 15-20 years of moderate to low exposures to respirable crystalline silica.
- Accelerated silicosis - which can occur after 5-10 years of high exposure.
- Acute silicosis - which can occur after a few months or as long as 2 years after exposure to extremely high levels of crystalline silica.
To learn more about the terrible effects of the disease, see this short film from China: Dying to breathe, about workers who contract silicosis after working in gold mines.
Crystalline silica also causes cancer of the lungs.
- WorkSafe Victoria:
- Health and Safety Solutions: Stonemasonry - Preventing crystalline silica exposure;
- Compliance Code for Foundries;
- Guidance Note: Roof Tile Cutting Silica Dust Exposure
- From the HSE : a range of COSHH (Control of Substances Hazardous to Health) Essentials with a range of flyers for managers and then a number of topics for:
- :Brick and tile making - information on clay milling, sand handling and screening, facing green bricks with sand, moving green and fired bricks, manual dehacking and batching, tile pressing, ventilated vehicle cabs
- Construction - information on concrete scabbling, chasing, Drilling and coring with power tools, crushing and screening, clearing and removing rubble, tunnelling and shaft sinking, and more.
- Ceramics - information on glaze and colour preparation, casting, fettling, kiln loading (placing) and unloading, and spraying glazes and colours
- Foundries - covering topics from fumes to furnace relining
- Manufacturing - information on making products that include mineral powder, dry-mixing powders containing silica, and small packing operations: Dry products containing silica
- Quarries - information on exacavting and haulage, crushing, drying and cooling, dry screening , silica flour: bag filling and transfer, cleaning up silica dusts and more
- Slate Works - information on primary sawing, automated slate sawing, sawing slate into special sizes and shapes, manual slate splitting, and dressing slate
- Stonemasons - information for managers, and on sawing, using rotary tools and chiselling
- a topic information page
exposure to stonemasonry dust: Guidance for employers
and Control of Exposure to Silica advice for employers on how to protect themselves and their employees from harmful dust present in many products like bricks, tiles and concrete.
- From the US:
- From National Institute for Occupational Safety and Health (NIOSH), a webpage on silicosis - specifically for workers in construction and abrasive blasting.
- Construction Research and Training (CPWR) - an organisation working closely with US construction unions- a website Work safely with silica. As well as information on US silica regulation and official research, the new resource includes other research, articles, and training materials, as well as responses to frequently asked questions. The site includes a 'Know the hazard' section, geared for anyone interested in learning more about why silica is hazardous, the risk, who's at risk, the health effects, and steps workers and contractors can take to work safely with silica.
Last updated, May 2015