Silicosis is a fibrotic disease of the lungs caused by the inhalation and deposition of respirable crystalline silica (RCS) in the lung tissue. It falls into the group of diseases known as pneumoconioses.¹ Very fine silica dust scars the lungs and causes progressive respiratory impairment.

Accelerated silicosis is an aggressive form of pneumoconiosis. It progresses more quickly than chronic silicosis, developing within 3 to 10 years of exposure. Once the disease has become established, symptoms include cough, breathlessness, tiredness and weight loss. These may develop after exposure to RCS has ceased, although continued exposure hastens the progression of the disease.

It's a preventable disease. There's currently no known treatment to arrest the progression of accelerated silicosis, apart from lung transplantation.

The nature of exposure

Cutting, grinding and polishing of artificial stone exposes workers to very fine respirable silica dust. Unlike natural stone like granite, which typically contains only up to 30% silica, engineered stone can have silica concentrations of over 90%.

No safe levels of silica exposure have been established.² Read the University of Adelaide engineered stone report for more information (PDF).

Types of silicosis

There are several clinical and pathologic varieties of silicosis, based on the time taken to accumulate a Total Lung Burden of respirable crystalline silica sufficient to trigger a nodular fibrotic reaction in the lung tissue. There are 3 major forms:

1. Chronic (Nodular) Silicosis – classic silicosis, exposure for more than 10 years.
2. Accelerated Silicosis – exposure over 1 to 10 years but usually only 3 to 10, historically rare but much more common recently in engineered stone workers.
3. Acute Silicosis – exposure for less than 1 year (used to be less than 3 years), historically very rare.

The development of different forms of silicosis is also dependent on the concentration and the surface texture of the crystalline silica particles. Chronic (nodular) silicosis is the most frequent form of the disease, often manifesting 10 to 20 years (but can be up to 40) after first exposure.

Although acute and accelerated silicosis are less common, accelerated silicosis can develop within only 5 to 10 years after the initial exposure to silica dust, while acute silicosis develops within a year.³

Initiation and progression of silicosis

The minimum Total Lung Burden of respirable crystalline silica needed to trigger accelerated silicosis or chronic silicosis isn't known. The rate of change in lung function deterioration for workers with accelerated silicosis is on average 10 times faster than the normal age-related deterioration. Even in the absence of further exposure, silicotic nodules may continue to develop and coalesce resulting in the development of progressive massive fibrosis (PMF). If a worker has had sufficient exposure to silica dust, the disease may not become first evident until after the worker has left the industry.

Symptoms

In general, most cases of silicosis are asymptomatic until the disease is severe. Progression of the disease may vary considerably between individuals for reasons not yet understood. In the early stages, workers will be asymptomatic and symptoms may not appear until some years later, even after exposure has ceased.

• Early symptoms of silicosis include shortness of breath (dyspnoea) after exercising and a harsh, dry cough.
• Increasing dyspnoea may develop as the disease progresses.
• Patients with advanced silicosis may have trouble sleeping and experience a productive cough, loss of appetite and weight loss.

The situation in Australia and Aotearoa New Zealand

Factors that have given rise to the silicosis epidemic include:

• Composition of artificial stone products — the various materials it's made from, including respiratory very high levels of respirable crystalline silica (RCS).
• Inadequate dust control measures or adherence to safe workplace practices.
• Barriers to instituting effective and regular health monitoring in at-risk workers.
• Failure of effective regulation within the relevant industries.
• Excessive exposure to RCS in many other industries like mining and construction.

Australia

• Employees across Australia have been placed at risk of developing an aggressive, debilitating and potentially lethal respiratory disease due to unsafe work practices in the manufacture and installation of engineered stone, commonly used for kitchen, bathroom and laundry benchtops.
• Silicosis can occur in various industries including those with natural silica sources like mining.
• Almost all cases of silicosis, especially those in younger age groups, are in stonemasons working with engineered stone.
• Silicosis cases have occurred for many years, but a dramatic increase began being reported from 2015 from cutting and installation of engineered stone benchtops.
• Silicosis associated with engineered stone has been found to be associated with a shorter duration of exposure, more rapid disease progression and higher mortality.⁴
• Cases continued to be diagnosed at such a fast rate since then, that we acted urgently, raising a national alarm and alerting authorities.
• The RACP, AFOEM and TSANZ all contributed to the membership and deliberations of the National Dust Disease Taskforce.

Aotearoa New Zealand

Aotearoa New Zealand has an engineered stone benchtop industry and our members are activating awareness and circulating information about what's needed to address a yet unmeasured and not fully investigated health issue.

WorkSafe, the Ministry of Health and ACC have worked together on a health assessment process to support the delivery of consistent prevention, assessment and treatment services across the country for engineered stone workers, see the Accelerated silicosis assessment pathway (PDF).

The importance of regular health surveillance

• Regular health surveillance to detect early lung changes is important as silicosis isn't often diagnosed until it is in advanced stages.
• Ongoing health monitoring is important for workers who have been exposed to hazardous levels of silica dust but where screening hasn't yet detected disease.
• Long term regular health surveillance must be conducted for all workers in the engineered stone industry and for at risk workers in other industries.
• Health surveillance should include a respiratory questionnaire, work and exposure history, lung function tests and lung imaging.
• Recommended standards for respiratory surveillance have been set out in the TSANZ Respiratory Surveillance Position Paper.⁵

References
¹ Austin EK, James C, Tessier J. Early detection methods for silicosis in Australia and internationally: a review of the literature. International Journal of Environmental Research and Public Health. 2021 Jul 31;18(15):8123.
² Ramkissoon C, Tefera Y, Gaskin S, Pisaniello D. Prohibition of engineered stone: Literature review and gap analysis. July 2023.
³ Hoy, R.F.; Baird, T.; Hammerschlag, G.; Hart, D.; Johnson, A.R.; King, P.; Putt, M.; Yates, D.H. Artificial stone-associated silicosis: A rapidly emerging occupational lung disease. Occup. Environ. Med. 2018, 75, 3 –5.
⁴ Wu N, Xue C, Yu S, Ye Q. Artificial stone‐associated silicosis in China: a prospective comparison with natural stone‐associated silicosis. Respirology. 2020 May;25(5):518-24.
⁵ Perret JL, Miles S, Brims F, et al. Respiratory surveillance for coal mine dust and artificial stone exposed workers in Australia and New Zealand: a position statement from the Thoracic Society of Australia and New Zealand. Respirology 2020; 25: 1193 –1202.