Over recent months, we have had several enquiries from designers in relation to industry concerns with silica-based building products and the potential for serious health risks including lung diseases such as silicosis. The intention of this article is to provide a better understanding to designers of the products containing silica, increasing the awareness of the risks when handling these products (and for that matter any products that generate airborne dust) and ultimately managing the risk appropriately.
What is Silica?
Silica, also named silicon dioxide, is a compound of the two most abundant elements in Earth’s crust, silicon and oxygen. The mass of Earth's crust is 59 percent silica, the main constituent of more than 95 percent of the known rocks. It is widely used in structural materials, microelectronics and as components in the food, pharmaceutical and Construction industries.
Silica Use in Construction Materials
Silica is found in many of the most common raw materials used in construction such as asphalt, brick, cement, concrete and concrete block masonry, drywall, fibre cement, grout, shotcrete, mortar, some paints, plaster, rock, clay and ceramic roofing tiles, sand and soil. Various decorative stone finishes can also contain silica, with examples including limestone, quartz, sandstone, slates, marble, granite, and engineered stone.
Silica, is known to cause adverse health effects if handled improperly, including silicosis, bronchitis or lung cancer, lung diseases caused by prolonged inhalation of fine crystalline silica dust.
In addition to understanding the materials that can produce respirable crystalline silica, it's vital for workers to know what construction processes put them and others at potential risk. These include abrasive blasting, cutting, coring, drilling, grinding, jackhammering, milling, mining, mixing, polishing, sanding, sawing, scraping, scarifying (earthworks).
Processes such as sweeping and cleaning up a construction site can be hazardous if any of these processes have taken place beforehand. The potential risk of exposure to fine crystalline silica dust remains high and can easily be overlooked when “pushing around a broom”, without thinking and without the use of appropriate personal protective equipment. Accordingly, making sure that respiratory protection is used in any and every situation involving respirable crystalline silica is vital.
The Health and Safety at Work Act 2015 requires that work health and safety is everyone’s responsibility, PCBUs who are ‘upstream’ from the workplace (for example designers such as architects and engineers, manufacturers, suppliers or installers of plant, substances or structures) also have a role to play in managing risks to health and safety at work.
What is Silicosis?
Silicosis is an irreversible and progressive disease that causes fibrosis of the lungs from the inhalation of tiny particles of respirable crystalline silica (RCS) being imbedded in the lining of the lungs. The only treatment for advanced disease is a lung transplant.
Documented severe cases of the disease have been consistent with accelerated silicosis, a form of the disease which develops over a short period (1 to 10 years) from inhalation of very high concentrations of RCS. This is typically associated with the drilling or cutting silica-containing material without personal protection.
Engineered Stone
Engineered stone is widely used for kitchen and bathroom countertops and is known for being extremely durable, resistant to heat, scratching, chemicals and stains. It is non-porous unlike marble or granite products and as such doesn’t require sealing and ongoing maintenance to maintain a hygienic and durable surface.
While silica is also found in natural stones such as marble and granite, it is typically in lower quantities than in engineered stone made with quartz, which can contain up to 90 per cent silica. Reputable stone manufacturers are acutely aware of the health risks associated with silica and in recent years have been researching and developing alternative products with substantially reduced silica content. This work is ongoing.
Crystalline silica is an occupational hazard for those working with stone countertops, because the process of cutting and installing the countertops can potentially create large amounts of toxic airborne silica dust.
Workers are not at risk when safety measures are implemented correctly in the fabrication shop. Fabricators are required to ensure the safety of their workers by properly implementing and enforcing safety measures, which include wet working methods, local exhaust ventilation and extraction systems, air measurement and filtration systems and use of personal protection equipment. Fabricators and product installers who fail to implement appropriate safety measures, put themselves, fellow workers and other contractors at high risk!
The engineered stone manufacturers must also provide sufficient detailed technical information about their products to ensure that the fabricator is aware of the risks associated with handling silica-based materials and to implement adequate and appropriate safety measures to protect the safety of its workers.
Engineered stone surfaces are completely safe in any of their final applications and do not pose any risk to the end user. That said, the end user of the product must be made aware that any future modifications to the product is high risk and must be done carefully adhering to the recommended Health and Safety procedures eg drilling the benchtop on site for the installation of a filtered water tap or permanent connection to a coffee machine is high risk.
Working with Engineered Stone - Worksafe NZ Advice
Worksafe Mahi Haumaru Aotearoa have published extensive advice relating to the management of risks associated with respirable crystalline silica. In summary:
Before starting work using engineered stone, businesses must complete a risk assessment and review their controls. It is important to eliminate uncontrolled dry cutting, grinding or polishing of engineered stone.
If this is not reasonably practicable then exposures must be minimised. Options include:
- substituting engineered stone for materials with a lower silica content.
- isolating work areas or tasks that generate dust using physical barriers or computer numerical control (CNC) machines.
- using engineering controls, such as local exhaust ventilation (LEV), water suppression (wet cutting), or on-tool dust extraction attachments. Wet sprays should be controlled by guards to prevent dust becoming airborne and wet waste must be managed. LEV system dust collectors or vacuums should be H-class HEPA filtered. Any LEV must be effective, fit for purpose, installed, set up and used correctly and maintained so that it remains effective.
- further minimisation controls include administrative controls, such as good housekeeping practice (wet wiping, using an H-class HEPA-filtered vacuum, and low-pressure water cleaning – dry wiping or sweeping is not appropriate).
If a risk still remains, use the appropriate personal protective equipment:
- use a suitable respirator with a filter cartridge with the appropriate assigned protection factor; the appropriate respirator and filter cartridge combination will be informed by exposure monitoring.
- ensure the respirator is fit-tested for the worker, cleaned and maintained properly.
- wear suitable work clothing such as coveralls that are disposable or can be laundered at the workplace to avoid taking them home.
Links:
For more information about the control of dust (including silica) in the workplace, please visit the following Worksafe links
- https://www.worksafe.govt.nz/about-us/news-and-media/accelerated-silicosis/
- https://www.worksafe.govt.nz/topic-and-industry/dust/silica-dust-in-the-workplace/
- https://www.worksafe.govt.nz/topic-and-industry/dust/8-key-things-for-workers-to-know-controlling-silica-dust-in-the-workplace/
- https://www.worksafe.govt.nz/topic-and-industry/dust/controlling-dust-with-on-tool-extraction/
Further information is available through Site Safe New Zealand Inc.:
- https://www.sitesafe.org.nz/guides--resources/practical-safety-advice/dust/
Managing the Risk
The Health and Safety at Work Act 2015 requires that work health and safety is everyone’s responsibility, PCBUs who are ‘upstream’ from the workplace (for example designers such as architects and engineers, manufacturers, suppliers or installers of plant, substances or structures) also have a role to play in managing risks to health and safety at work.
“They have a duty to ensure, so far as is reasonably practicable, that the work they do or the things they provide to the workplace, such as plant, substances or structures, don’t create health and safety risks.”
While the Act does not specify how safe design information should be communicated from designers to clients, contractors and users, depending on the size of the project, it may be useful to consider the following:
- Health and Safety section in specification
- Safety notes on plans
- Risk Register
- A Health and Safety File within the project file
- Safe Design Report/Design Construction Safety Report or Statement
- Post-construction Review Report
Health and Safety Section in Specification
It is important for the designer to incorporate Masterspec specification sections 1220 Project, and 1260 Project Management and to add project specific content. These preliminary and general sections include detailed information relating to Health and Safety processes and a place where known hazards can be identified by the Designer.
Risk Register
The risk register should include:
- Your risk analysis and hazard management planning
- Records from any safety team meetings or workshops. The risk register should be updated throughout the lifecycle of your design with information about any changes that could affect health and safety aspects.
‘Health and Safety by Design’ is the process of managing health and safety risks throughout the lifecycle of structures, plant, substance, or other products. Designers are in a strong position to make work healthy and safe from the start of the design process. Health and Safety by Design is not considered a separate concept from good design – they are the same thing.
Risks to health and safety arise from people being exposed to hazards (anything that can cause harm). This includes workers and others.
Designers must eliminate health and safety risks arising from work so far as is reasonably practicable. If it’s not practicable to eliminate, they must minimise risks, so far as is reasonably practicable.
Wherever possible, design safety reviews should involve the people who will eventually construct, manufacture or maintain the structure, plant or substance.