Introduction
Crystalline silica is a natural substance found in concrete, bricks, rocks, stone (including artificial or engineered stone found in composite kitchen benchtops), sand and clay.
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When in the form of a fine respirable dust (respirable crystalline silica or RCS) it is considered hazardous to health. RCS is generally created in the workplace by processes such as cutting, drilling, crushing, grinding, sawing and polishing of natural or man-made products containing crystalline silica.
RCS is released into the air if appropriate control measures are not in place. For example, the dry cutting of engineered stone, where dust is readily dispersed into the air when control measures such as a water spray or a vacuum source are not in use. Workers in the following industries or who work with the following materials are most at risk of being exposed to RCS: mining; quarrying; tunnelling; roading; foundries; construction; manufacturing of concrete, bricks and tiles; kitchen benchtop manufacturing (natural and engineered stone), finishing and fitting; abrasive blasting; monumental masonry work; concrete drilling, cutting, grinding, fettling, mixing, handling, and dry shovelling.[1]
Ongoing exposure to RCS can cause a fibrotic lung disease called silicosis, as well as lung cancer and other disease. However, evidence indicates that silicosis from working with engineered stone occurs at a younger age, after shorter exposure periods, and has more severe health impacts. This is called ‘accelerated’ silicosis.
Due to the higher risks involved with engineered stone this document sets out several options which directly relate to work with engineered stone (refer to options 2, 3, and 5). However, to ensure controls are in place for all exposed industries we have also included options which would apply to all industries.
Engineered stone is widely used in New Zealand
Engineered stone is a popular kitchen and bathroom bench material used in New Zealand homes and businesses, and is used in more than half of new home builds. The product is popular because of its serviceability, high standard of finish, and price, and the market for it has grown steadily since it first became available in New Zealand in the late 1980s.
Engineered stone is imported as slabs or solid sheets from United States, Israel, Spain, and China in particular, and there are six or more major suppliers into the New Zealand market. Since the early 2000s, engineered stone sales have maintained five per cent per annum growth to make it the pre-eminent benchtop material. Sales are currently about 60,000 slabs[2] annually. To meet this demand, there are currently about 157 fabrication businesses employing about 600 fabrication workers in New Zealand. WorkSafe estimates the cumulative number of fabrication workers in the industry since 2001 at approximately 1,000.
There are health risks faced by workers in engineered stone fabrication
Engineered stone products are a mixture of natural stone, glass and other materials that are ground and baked into a polymer binder. Engineered stone is primarily made up of quartz and can contain in excess of 90 per cent crystalline silica, compared to 3–40 per cent in natural stone, such as granite or marble.
The manipulation of engineered stone, such as cutting to size, drilling holes for positioning taps or sinks, and polishing, creates RCS which can cause severe health implications in workers frequently exposed to it.
Exposure to, and inhalation of, high levels of RCS can cause silicosis, a fibrotic disease of the lungs. All workers who come in contact with RCS are at risk of chronic silicosis, usually over long periods of exposure, but those exposed to RCS from work with engineered stone are at risk of earlier and more severe disease, known as ‘accelerated silicosis’.[3]
Accelerated silicosis is an emerging occupational disease caused by exposure to significant concentrations of respirable crystalline silica from unsafe work with engineered stone benchtops. It is an aggressive form of silica-related disease that can develop over a short period of time (usually approximately 3–10 years, although it can manifest in less than one year). It is distinct from chronic silicosis, which is not uncommon and rarely becomes progressive.
Several Australian screening studies have found that 20–30 per cent of engineered stone workers exposed to RCS in the period before 2019 have developed some degree of respiratory disease as a result.[4] This figure is likely to increase over time. Since 2019, Australian regulatory settings regarding risk management of RCS have changed; however, the impact of these changes on silicosis incidence has not been assessed.
It is expected that as the demand for engineered stone benchtop and similar fabricated products continues to grow in New Zealand, between 600–1,000 workers are at significantly elevated risk of crystalline silica-related disease.[5] Evidence from Australia is that about one in four of this group of workers already have silicosis, even though some do not yet show symptoms.[6] Fewer workers have been assessed in New Zealand than Australia.
There are other industries that face similar risks due to the generation of RCS
As noted above, risks of RCS exposure are not limited to engineered stone. Approximately 270,000 workers in New Zealand are probably exposed to RCS, and approximately 80,000 have probable high exposure,[7] defined as exposure at or above the corresponding Workplace Exposure Standard (WES). Most workers with probable high exposure work in the construction sector.[8]
Footnotes
[1] WorkSafe 2019, https://www.worksafe.govt.nz/topic-and-industry/dust/silica-dust-in-the-workplace/.
[2] Engineered stone is generally manufactured and imported in 3.0 by 1.4 m slabs.
[3] See Annex I for a brief history on silicosis and its incidence rate in New Zealand.
[4] Hoy RF, Dimitriadis C, Abramson M, et al. (2023). Prevalence and risk factors for silicosis among a large cohort of stone benchtop industry workers. Occupational and Environmental Medicine, 80;439-446. This study in Victoria, Australia, found that 117 of 414 engineered stone workers who underwent screening (28 per cent) had silica-related disease. The median age of diagnosis was 42 years, and the median exposure time was 12 years.
[5] Based on WorkSafe estimates.
[6] See https://www.health.gov.au/ministers/the-hon-ged-kearney-mp/media/national-registry-to-fight-silicosis-and-protect-workers.
[7] Based on the New Zealand Carcinogens Survey (2021) and workforce data (2021).
[8] See New Zealand Carcinogens Survey 2021: https://www.worksafe.govt.nz/research/new-zealand-carcinogens-survey-2021/ and McLean D, Glass B, ‘t Mannetje A & Douwes J (2017). Exposure to respirable crystalline silica in the construction industry—do we have a problem? The New Zealand Medical Journal, 130;1466, p78-82.