Silicosis in Australia 

Silicosis is a progressive lung disease caused by the inhalation of respirable crystalline silica (RCS) dust. The silica dust causes lung scarring (pulmonary fibrosis), which impairs breathing and can be fatal. Silicosis is categorized as either ‘simple’ or ‘complicated’ depending on the pattern and extent of the scarring. Silicosis is also categorized based on the duration between exposure and disease onset. Acute silicosis occurs relatively shortly after exposure to silica dust. Accelerated silicosis occurs from three to ten years after exposure. Chronic silicosis, the most common form of the disease, occurs from ten to thirty years after exposure. Sources of RCS dust include: 

• Sandstone 
• Gritstone 
• Quartzite 
• Concrete 
• Mortar 
• China stone 
• Slate 
• Brick 
• Ironstone 
• Basalt 
• Dolerite 
• Limestone 
• Chalk 
• Marble 

In this article, Global Road Technology evaluates silicosis in Australia focusing on silicosis as a deemed disease in Australia, national silicosis data, silicosis health reforms in Australia, and HRCT vs X-Rays for silicosis diagnosis in Australia.

Silicosis as a Deemed Disease in Australia. 

The first national Deemed Diseases in Australia list was published on 31 August 2015. Most jurisdictional lists associated with Deemed Diseases legislation appear to have been originally based on the International Labor Organization (ILO) List of Classified Diseases originally presented in Convention 42. Australia is a signatory to ILO Convention 42. Silicosis caused by exposure to silica dust is a respiratory disease Silicosis with or without pulmonary tuberculosis if silicosis is an essential factor in causing the resultant incapacity or death according to Convention 42 which is a Deemed disease in Australia. The Review of the 2015 Deemed Diseases in Australia was published in December 2021 along with a revised List of Deemed Diseases in Australia and Supporting Guidance Material. The report provides evidence-based information on a list of diseases and occupational exposures, for consideration by worker’s compensation jurisdictions when reviewing the deemed diseases lists in their compensation legislation. The deemed diseases approach reverses the onus of proof when a claim is made but doesn’t guarantee the success of a claim. The worker still must demonstrate they have had sufficient occupational exposure to the relevant exposure. 

National silicosis data – The data gap in Australia.  

At present, there is no national data relating to the incidence and outcomes of silicosis nor do all States and Territories publish silicosis data. The National Dust Disease Taskforce has responded to this data gap by recommending that a National Occupational Respiratory Disease Registry be operationalized as soon as possible, with an initial focus on mandatory reporting of silicosis, and voluntary reporting of other occupational respiratory diseases. In the absence of a National Occupational Respiratory Disease Registry, the NDDT noted that the best estimates of silicosis prevalence must be drawn from data collected and reported by some jurisdictions. The available data shows: 

• Queensland screened 1053 workers and identified 202 silicosis cases 
• Victoria screed 456 workers and identified 133 silicosis cases 
• South Australia screened 295 workers and identified 18 cases of probable, possible or confirmed simple silicosis 
• Western Australia has screened 90 workers and identified 8 silicosis cases 

The NDDT provided data on accepted silicosis workers’ compensation claims by jurisdiction and industry. However, it cautioned that workers’ compensation claims data are not a true indication of the incidence of silicosis in Australia, as only accepted workers’ compensation claims are included. Further, the established compensation schemes for workers affected by dust diseases are not uniform across all jurisdictions and there are many reasons why a worker with silicosis may not make a compensation claim, including fear of loss of employment. 

Silicosis related health reforms in Australia 

We look at the different health reforms that have been recently implemented in the different States and Territories of Australia. 

NSW – 1 July 2020, the NSW Government halved the silica exposure limit, from 0.1 mg/m3 to 0.05 mg/m3 and this was followed up with commencement of the NSW Dust Disease Register which required all NSW medical practitioners to notify the NSW Health upon diagnosing a silicosis case. Late 2020, the NSW Government published NSW Dust Strategy 2020-2022 which focused on asbestos, silica and wood. Air monitoring and health screening are key features of the NSW Dust Strategy. Health screening in NSW is free in some instances. Icare NSW provides free lung screening when a business has received a Safe Work NSW improvement notice. 

Victoria – 17 December 2019, the reduced exposure standard of RCS to 0.05 mg/m3 which led to publication of Compliance Code on Managing exposure to crystalline silica: Engineered stone in February 2020. In September 2021, the Victorian Minister for Workplace Safety announced Australia’s first dedicated public occupational respiratory clinic. The facility offered health screenings and treatments as part of a partnership between WorkSafe and The Alfred. Eligible workers would go through full health assessments for silicosis and receive both their health outcome and treatment plan during a one-day clinic visit. 

Queensland – 1 September 2020 the occupational RCS exposure limit was reduced to 0.05 mg/m3 on 1 September 2020. In November 2020, the Queensland Government announced the development of whole lung lavage, in a collaboration between Prince Charles Hospital and University of Queensland. Whole lung lavage involves the precision removal of silica crystals and damaged cells from the lungs, effectively rinsing out the lungs in what can be a four to five-hour procedure. 

South Australia – 1 July 2020, the occupational RCS exposure limit was reduced to 0.05 mg/m3 in South Australia. The Silicosis database was also developed, and a compliance program introduced, with 102 compliance breaches identified in 2020-21. 

Western Australia – 27 October 2020 the WA Government reduced the occupational RCS exposure limit to 0.05 mg/m3 with a few months later, the Government announced that it had amended the Occupational Safety and Health Regulations 1996 (WA) to require employers to provide a low-dose high-resolution computed tomography (HRCT) scan instead of the previously required chest X-ray. 

HRCT vs X-rays for silicosis diagnosis in Australia 

Respiratory surveillance also referred to as occupational lung disease screening in Australia has common elements, although differences do occur due to available technology and the cost of surveillance. Exposure history and respiratory symptom questionnaires constitute the first step in respiratory health surveillance. Spirometry is a second commonly used method. Together with questionnaires and spirometry, medical imaging commonly radiography (X-ray) is used for diagnosis, surveillance and screening of occupational lung disease. In addition, various HRCT protocols are a final step in the surveillance process. Most silicosis cases are not diagnosed at an early stage, as the initial phase of the disease is typically asymptomatic and is often undetectable with spirometry and X-ray. Specifically, silicosis can present a diagnostic challenge due to its radiological resemblance and clinical overlap with sarcoidosis, pulmonary tuberculosis, and neoplastic lesions. 

Compounding the issue of exposure to RCS is that X-ray and HRCT present the concern of giving a regular radiation dose to workers. For example, in NSW, workers need to be scanned every year for their whole career. Regulators have a duty of care not to expose workers to an ongoing, annual dose of radiation, although it may be argued that level of radiation is incidental and must be weighed against the opportunity for a more sensitive test that reliably detects diseases. It has been identified that chest X-rays are failing to reliably detect occupational lung disease. In a cohort of workers from Queensland, 43% had chest X-rays classified as normal using ILO Classification System, however, the disease was visible on HRCT. It is recommended that HRCT be used for diagnosis of occupational lung disease owing to its higher sensitivity to detect early diseases and greater accuracy in characterizing patterns of disease. The enhanced sensitivity is provided by the finer spatial resolution and 3D nature of HRCT. 

Conclusions 

Silicosis is a fatal disease and yet it is totally preventable by removing exposure. At risk-occupations include mining, quarrying, construction, and the not so traditional occupations such as garment sandblasting, horse training and stone masonry. The resurgence of silicosis in Australia is a cause for concern and it shows that many workers are at risk of developing silicosis. Early detection of silicosis should focus on providing insight into its pathogenesis and the biological mechanisms that underpin its progression. X-ray was determined as not sufficient in detecting silicosis, while spirometry is subject to the skill and experience of the practitioner. HRCT is recognised as the optimal method, however, it is not always available. 

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