Annex I: Silicosis and engineered stone background

This risk results from the extremely fine dusts created while engineered stone products are being cut, ground or polished, usually during fabrication as benchtops and other bathroom and kitchen benches and furnishings. 

Crystalline silica dust, particularly RCS, is an occupational hazard that has been known about, and managed to some extent, for hundreds of years or longer. It has been known as a cause of silicosis, a chronic fibrotic lung disease.^[1]

There are three types of silicosis: 

• Acute silicosis: may occur after exposure of less than a year to very large amounts of RCS.
• Accelerated silicosis: may occur after exposure to large amounts of RCS over a shorter period of time, typically 3 to 10 years, and has been seen in workers from the engineered stone kitchen benchtop industry.
• Chronic silicosis: typically results from exposure to RCS over more than 20 years, and is usually seen in miners, tunnellers, and stonemasons and others working with stone and cement products.

Developed countries have regulated for the management of RCS risks for at least a century, and until recently, RCS risks had been considered well managed, and generally a reduced threat to workers. Each time there has been a significant change in technology or work methods there has needed to be changes to the management of risks to workers. When hand tools and traditional crafts were replaced by pneumatic cutting and hammering equipment a century or more ago, worker output and exposures to dust increased greatly and there were resulting changes to ventilation, dust suppression, and personal protective equipment (PPE) requirements for workers. Where these controls weren’t in place there were inevitably increases in the incidence of disease among workers. 

There is increasing evidence that workers remain at risk of harm from exposures to RCS.^[2] In recent years this has led many countries to revise the Workplace Exposure Standard (WES) for RCS that are set under health and safety legislation (See Annex IV).

Recent research on causation

It is well established that processing engineered stone gives rise to particularly high concentrations of crystalline silica as very fine dusts (less than 600 nm) that react with cells in the lungs and which the body is not able to remove, as with other exposures to RCS. 

The most recent research has begun to examine more closely the effect of dust particle chemistry on the lung cell response. This research suggests that metallic elements present in addition to crystalline silica, volatile organic compounds in resins, and dust particle physical characteristics all combine to make engineered stone particularly toxic to lung cells.^[3] It is, however, an emerging area of research that has been laboratory based. There are several key aspects of the physiology that will require further laboratory study and we would expect that the findings from the work will be further validated in a clinical setting, and extend into studies of workplace practices. This is an emerging area of research, MBIE has commissioned an independent scientific review in order to assess the available scientific evidence for known risks and impacts of working with engineered stone.

Current known incidence of silicosis in engineered stone workers in New Zealand

New Zealand has established an Accelerated Silicosis Assessment Pathway (ASAP). This assesses workers who may have been exposed to RCS from fabricating engineered stone in New Zealand for at least six months in the past ten years. The claim is first lodged by a medical practitioner if the exposure threshold and ACC eligibility criteria are met. The Assessment through the ASAP is then progressed. There is a health pathway still available through the ASAP for those who meet the exposure threshold but do not meet the ACC eligibility criteria.^[4]

From a review of claims in March 2022, the ages of those assessed range from just under 20 years to mid-70s. The median age at lodgement is 42 years. The median age of claimants with a diagnosis of silicosis is 47 years, with 65 per cent aged 30–49. This is also broadly consistent with international findings. 

Silicosis is not restricted to working with engineered stone. There are risks to workers from a broad range of stone, masonry and ceramic materials that contain crystalline silica and that have historically been a cause of silicosis in mine and quarry workers, stonemasons in natural stone, and the construction sector, predominantly with concrete products, but others as well. WorkSafe estimate that up to 80,000 workers in these sectors are working in conditions where the Workplace Exposure Standard (WES) for RCS is regularly exceeded. Table I.1 shows the crystalline silica content of some of the materials involved, however, caution must be applied as the risk does not relate directly to the crystalline silica content, but rather to how well the workers’ exposure is controlled.  

Table I.1 – Crystalline silica content of different types of building material

From: Safe Work Australia^[5]

Footnotes

^[1] The term ‘silicosis’ was first used in the 1870s, and the condition was recognised by the International Labour Organization (ILO) in 1930. An ILO convention was introduced in 1934, and in 1958, an ILO agreement defined the chest radiograph features of the disease. Later, in 1995, an ILO/World Health Organization (WHO) Global Programme for the Elimination of Silicosis was established and subsequently reaffirmed.

^[2] See https://bpac.org.nz/2023/silicosis.aspx.

^[3] Ramkissoon C, Song Y, Yen S, Southam K, Page S, Pisaniello D, Gaskin S, Zosky GR. Understanding the pathogenesis of engineered stone-associated silicosis: The effect of particle chemistry on the lung cell response. Respirology. 2024 Mar;29(3):217-227. doi: 10.1111/resp.14625. Epub 2023 Dec 3. PMID: 38043119..

^[4] The Assessment Pathway was created by ACC, Ministry of Health and WorkSafe in September 2020. The Assessment Pathway involves an initial assessment by a GP who can lodge a work-related gradual process claim with ACC for further specialised tests and investigations funded by ACC based on exposure. The health assessment is voluntary, but workers who may have been exposed to RCS are strongly encouraged to be assessed so any dust-related health condition can be managed appropriately..

^[5] Safe Work Australia: Crystalline silica and silicosis. From: https://www.safeworkaustralia.gov.au/safety-topic/hazards/crystalline-silica-and-silicosis. 

^[6] The Health and Safety Executive (United Kingdom), May 2024. From: https://www.hse.gov.uk/pubns/indg463.pdf.

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