Navigating Silica Content in Construction
Silicosis, an occupational lung disease resulting from inhaling crystalline silica dust, has emerged as a pressing concern within the construction industry, paralleling the historical impact of asbestos. Whisker Architecture, attuned to the industry-wide repercussions of silicosis, is spearheading a comprehensive approach to silica management in the products we specify. This article explores the broader implications of silica inclusion, focusing on the Australian context and referencing authoritative sources, notably those from WorkSafe Victoria.
UPDATE: “On 13 December 2023, WHS ministers representing the Commonwealth, states and territories agreed to Safe Work Australia’s recommendation to prohibit the use of engineered stone to protect thousands of workers from respirable crystalline silica (silica dust).” https://www.safeworkaustralia.gov.au/safety-topic/hazards/crystalline-silica-and-silicosis/prohibition-use-engineered-stone
Silica in Common Construction Materials
In the construction industry, silica is pervasive, with implications reaching beyond the engineered stone benchtops that have sparked recent discussions. It's an issue that is more complex than it may appear on the surface.
For the purpose of clarity in this article we will park any conversations about the environmental concerns about any of the products we mention and focus purely on the health concerns. Worksafe Victoria did a series of personal protective equipment (PPE) and workplace equipment (e.g. air filtration units) audits as well as scanning of the lungs of stonemasons a couple of years ago. This was a great step forward in improving safety with these materials in a factory or workshop. It's much harder for organisations like Worksafe to police individual worksites versus fixed factory sites but it's also much less likely for the cutting of those products to be in a confined space on a work site - or is it?
It’s also worth noting that we are not economic experts but we do acknowledge that the authorities have a delicate balance to strike between making the workplace of trades safe and not making any sudden supply chain changes to an industry already struggling under a housing crisis.
For context the list below is from Worksafe Victoria. These materials contain common natural and manufactured products and their typical crystalline silica content:
engineered stone: 40% to 95%
sandstone: 70% to 90%
granite: 25% to 60%
ceramic tiles: 5% to 45%
autoclaved aerated concrete: 20% to 40%
slate: 20% to 40%
concrete: less than 30%
porcelain: 14% to 18%
brick: 5% to 15%
marble: less than 5%
fibre cement: 20% to 60%
Engineered stone benchtops contain 40-95% silica. Worksafe Victoria define engineered stone as “a manufactured composite stone material that contains resins and 40% or more crystalline silica”. Which is why you may have seen some manufacturers publicly announce that their benchtop materials are not engineered stone. Their products may contain less than 40% silica and be porcelain based instead.
Natural granite, a widely used material, contains 20-40% silica, akin to concrete and equal to low-silica engineered stone benchtops and some ceramic tiles.
What we, as responsible and professional architects, are doing through the process of writing this article is working to understand as much as we can about this problem so we can do our part to minimise the impact of silica in our industry.
It’s important to consider where the materials we use come from and what the standard of manufacturing safety is through the entire lifecycle of that product.
Is There a Safe Level of Silica?
In October 2023 Safe Work Australia has today published the Decision Regulation Impact Statement: Prohibition on the use of engineered stone (Decision RIS). As part of their press release, they state:
“The recommendation for a prohibition is based on the following:
Engineered stone workers exposed to respirable crystalline silica (RCS) are significantly over-represented in silicosis cases. Engineered stone workers are being diagnosed with silicosis at a much younger age than workers from other industries.
Engineered stone is physically and chemically different to natural stone. The high levels of RCS generated by working with engineered stone, as well as the differing properties of this RCS, are likely to contribute to more rapid and severe disease.
There is no toxicological evidence of a ‘safe’ threshold of crystalline silica content in engineered stone, or that other chemicals found in engineered stone do not pose a health risk to workers.
Silicosis and silica-related diseases are preventable. However, a persistent lack of compliance with, and enforcement of, the obligations imposed under WHS laws across the engineered stone industry at all levels have not protected workers from the health risks associated with RCS.”
Item 3 on that list about “safe” thresholds of silica raises some important questions. The report expands on this item:
“Adverse health effects are associated with airborne silica dust exposure, not the silica content of the bulk material. The limited empirical evidence available supports that a lower silica stone produces less RCS when processed (Qi and Echt 2016) (Ramkissoon, C, et al. 2022), and this in turn supports the logical presumption that reducing the crystalline silica content in the engineered stone slab results in reduced exposure to RCS. However, there is no epidemiological or laboratory toxicological evidence describing how the risk of disease would differ for workers exposed to RCS generated from engineered stone over a range of crystalline silica concentrations, or how it compares to that generated from natural stone. This is particularly important as the processing method is a known determinant of RCS production (Healy 2014) (van Deurssen , et al. 2014), and it can also impact the size of the particles emitted (Hall, et al. 2022).”
The difficulty we have with a determination that all engineered stone be banned is that the information readily available to the public regarding these products doesn’t seem to cover the adjacencies of several other common engineered construction materials - such as ceramic tiles, fibre cement cladding, and concrete. Inhaling silica dust causes silicosis. And even though there aren’t studies testing the % of silica in the dust content and how that might impact silicosis rates (an experiment which I’m sure would fail any ethics test) the report agrees that it’s logical to assume that less silica means less risk.
Until the government makes a ruling on this issue, we’ve chosen to benchmark acceptable silica levels in products used by our office in line with other accepted industry materials.
Alternative Construction Materials
Whisker Architecture, positioning itself ahead of industry guidelines towards best practices, actively seeks alternatives with reduced silica content. Reviewing the levels of silica in various material types has led us to believe that a maximum of 20% silica content in products we expect to be frequently cut - exposing the trade to regular dust inhalation - is a fair and reasonable benchmark.
Porcelain, with a silica content of 14-18%, stands out as a preferred choice for benchtops for its low silica content and high durability. Solid surface acrylic solutions, including Corian and Meganite, are zero-silica however there are concerns in our office regarding their chemical compositions and references to "dust explosions" in their Safety Data Sheets. Stainless Steel is another material, traditionally seen in commercial kitchens, with a zero-silica content that is gaining interest from architects and interior designers.
The cost implications associated with porcelain, solid surface acrylics, and stainless steel render them prohibitive for some clients. This economic reality has prompted a resurgence of interest in laminate benchtops, which, although previously overlooked due to limited durability, are making a comeback for certain clients.
Approved Benchtop Materials List
Whisker Architecture's benchmark of 20% silica content and below has led to a curated list of approved benchtop materials inside our office:
Porcelain - Silica content: 14-18%, Highly Durable
e.g. Cosentino DektonSolid Surface Acrylics - 0% Silica, Not suitable to place hot items on surface, under review in our office due to chemical concerns
e.g. Corian, MeganiteStainless Steel - 0% Silica, Highly Durable, some clients consider this cold and noisy as a material, no colour choice
Timber - Limited usage due to porosity and client maintenance
Laminate - 0% Silica, Economically viable, Not suitable to place hot items on surface and can be scratched
Other Composite Materials - Products like Paperock are a sustainable alternative for benchtops. We haven’t found their samples durable enough for a kitchen or wet area but would confidently use them elsewhere in the home.
This meticulous selection aligns with Whisker Architecture's commitment to sustainable and safe construction practices and will continue to be reviewed as we continue to learn.
Stainless steel is an alternative benchtop material many clients and architects are considering for its safety and potential for recycling.
Fibre cement cladidng is frequently used on homes and commercial buildings - as panels (as shown here) or as weatherboards or weatherboard-look panels. There has been a great increase in use of fibre cement due to its durability and affordability.
Beyond Benchtops: Considerations for Silica in Construction
The scrutiny of silica content in our office extends beyond benchtops to other critical construction elements.
Walls
Bricks, with a silica content of 5-15%, remain acceptable. Bricks are often broken on site but rarely in enclosed spaces.
Fibre Cement (FC) and Compressed Fibre Cement (CFC) contain 20-60% silica and are to be avoided in favour of products like Weathertex unless there is a specific fire rating or waterproofing requirement. These products are all cut on site but again, often not in enclosed situations.
Tiles
Porcelain tiles (14-18%) are endorsed for low silica content and high durability
Ceramic tiles (5-45% silica) and terrazzo (0-30% silica) will require a Safety Data Sheet verifying a silica content of 20% or less to be specified in our office. This is because tiles are often cut inside after plaster and windows are installed.
Structure - Structural components, particularly concrete, are under close examination. Whisker Architecture aims to reduce on-site concrete cutting and explore low-silica alternatives in collaboration with their engineering team. This strategy resonates with the broader goal of minimizing concrete usage without compromising on thermal mass benefits.
In navigating the complexities of silica inclusion, Whisker Architecture is not only responding to industry concerns but also leading the way towards a safer and more environmentally conscious built environment. Our commitment to staying ahead of industry guidelines, coupled with a nuanced understanding of economic realities, positions us as professional guides for our clients.
We are constantly learning and improving.
This article will continue to be updated as we learn more about this issue.
References:
WorkSafe Victoria. "Silica - Frequently Asked Questions." WorkSafe Victoria, https://www.worksafe.vic.gov.au/silica-faqs
WorkSafe Victoria. "Silica Dust - Construction Industry." WorkSafe Victoria, https://www.worksafe.vic.gov.au/silica-dust-construction
Australian Government. "Model Work Health and Safety Regulations." Australian Government, https://www.legislation.gov.au/Details/F2021C00231
Natural Stone Council. "Silica and the Built Environment." Natural Stone Council, https://naturalstonecouncil.org/
Safe Work. “Decision Regulation Impact Statement: Managing the risks of respirable crystalline silica at work” Safe Work, https://www.safeworkaustralia.gov.au/doc/decision-regulation-impact-statement-managing-risks-respirable-crystalline-silica-work
