Silica in Australia: Respirable Crystalline Silica Medicals

What is crystalline silica and silica dust?¹,²

Silica, also called silicon dioxide, is a widespread mineral that occurs naturally and is found in mortar, concrete, sand and stone, and manufactured in bench tops, tiles, bricks and some plastics. Most soils and rocks are largely made up of quartz, the most common form of crystalline silica, although different rock and soil types contain varying amounts. Silica dust is often generated through mechanical processes, including sawing, drilling, cutting, crushing and grinding.

Crystalline silica is most hazardous to workers when dust is produced, becomes airborne and inhaled. Due to the severity of the health defects that exposure to crystalline silica can cause, there is legislation in place to maintain and protect workers’ health. This includes the workplace health and safety (WHS) standards that states that silica dust levels are not to exceed the occupational exposure limit (OEL).

What is the workplace exposure standard (WES) in Australia?¹,²

It is the employer’s duty of care to ensure that exposure to respirable crystalline silica (RCS) does not exceed the occupational exposure limit (OEL). In Australia, the recognised standard is an eight-hour time weighted average (TWA) or 0.1 mg/m³.

Workplaces should aim to keep exposure as minimal as possible and to conduct air monitoring if there is a concern that the OEL is being surpassed and may pose a risk to an employee’s health.

How can silica dust effect workers?¹,³,⁶

Workers can be exposed to airborne RCS which is particularly dangerous when high levels of respirable size (diameter less than 10 µm) infiltrate deep into the lower lungs. Respirable silica dust particles are not usually visible and can result in irreparable lung and kidney damage.

Workers exposed to levels greater than the OEL are more at risk of developing occupational diseases, such as:

• Renal disease
• Chronic bronchitis
• Progressive massive fibrosis (PMF)
• Emphysema leading to chronic obstructive pulmonary disease
• Simple pneumoconiosis
• Acute silicosis
• Accelerated silicosis
• Chronic silicosis
• Scleroderma
• Lung cancer

What is silicosis and what are the symptoms?³,⁵,⁶

Chronic silicosis is a fibrotic lung disease caused by long term (ten years or more) exposure to and inhalation of low levels of free crystalline silica, or silica dust.

Accelerated silicosis develops after 3-10 years of moderate to high exposure to silica dust, resulting in scarring, inflammation and protein in the lungs.

Acute silicosis is a critical and accelerated form of the disease, which can be developed within several months or years of working with, and exposure to, high levels of silica dust. This causes a rush of protein into and serious inflammation of the lungs.

Even after exposure ends, the lungs continue to deteriorate, causing scarring to the tissue and symptoms to worsen. This generally includes occasional chest pain, feeling short of breath, loss of appetite, coughing, minor fatigue, weight loss and night sweats.

Unfortunately, there is no cure for the disease and silicosis is difficult to detect in the early stages, as symptoms do not tend to appear until much later. Affected workers are at significant risk of developing lung cancer and tuberculosis (TB).

How does crystalline silica effect the kidneys?⁷,⁸

Silica is better known to lead to diseases and illness in the lungs, however, studies have shown that workers exposed, compared to those not exposed, are 40% more at risk of developing renal disease. The disease, also known as chronic kidney disease (CKD), can effect the urinary system, raise blood pressure and cause oedema and kidney failure.

What occupational activities risk exposure?²,³,⁶

As silica is such an accessible and useful mineral, it is found in lots of products and used in many workplace and industry activities.

Activities include:

• Abrasive blasting (blasting tools can contain a maximum of 1% of crystalline silica)
• Angle grinding, chiselling and jack hammering of masonry or concrete
• Brick, stone or concrete cutting (specifically the use of dry processes)
• Construction labour activities – i.e. engaging compressed air or blowers and dry sweeping
• Excavation, earth moving and drilling of plant operations
• Fabrication and installation of composite (engineered and manufactured) stone benchtops
• Foundry casting
• Hydraulic fracturing of gas and oil wells
• Mining, mineral and quarrying ore treating methods
• Paving and surfacing
• Pottery making
• Stone and clay processing machine operations
• Tunnelling

Any activity involving the use of dry materials containing silica or quartz can generate dust particles.

What preventative measures can be introduced to the workplace?²,³

To decrease the risk of exposure in the workplace, a range of preventative measures are recommended, starting with identifying the activities and materials your workplace uses that may generate or contain crystalline silica. These methods should be implemented across each task stage involving silica, including the preparation, application and clear up of materials.

Some simple methods to minimise silica dust exposure are:

• Reading the safety data sheet (SDS) and labels of products to identify quartz
• Isolating the hazard to designated work areas
• Substitution
  – Swapping sand for metallic shot, grit or slag products in abrasive blasting
  – Using composite stone with less silica in bench tops
• Engineering controls using;
  – An industrial vacuum cleaner or wet sweeping to clean up dust
  – Routers and drills with dust collection bags
  – Tools with a water attachment fitted to suppress dust (on scabbling picks, power saws and jack picks)
  – Fitting large equipment (bulldozers and excavators) with air-filtering cabs
  – Wetting down dusty work spaces
• Personal protective equipment (PPE)
  – Half-face, P1 or P2 (particulate) respirator – must be clean-shaven to be effective
  – Airline respirators should be used in abrasive blasting
  – Clothing that does not collect dust easily

The Safe Work Australia guidelines recommend applying more than one control method where possible and to employ a health surveillance program to monitor any changes to your workers’ health.

Health surveillance for crystalline silica workers in Australia²,⁴

Australia’s leading occupational health bodies recognise that our construction, mining and masonry workers are among those most at risk. The Safe Work Australia guideline for PCBUs, Health Monitoring for Exposure to Hazardous Chemicals, states that workers should partake in a silica-specific medical examination at entry and exit to silica work, and annually for the duration of exposure. The purpose of annual surveillance as a preventative measure is to monitor any changes indicating lung deterioration caused by silica exposure.

The Safe Work Australia Crystalline Silica medical includes:

• Respiratory medical and occupational exposure history
• Medical examination
• Spirometry (lung function) test
• Medical review and sign off
• Chest X-ray (ILO standard)

Health surveillance for crystalline silica workers in Queensland mines and quarries¹

In 2017 the Queensland Department of Natural Resources, Mines and Energy (DNRME) introduced health monitoring guidelines for mine and quarry workers handling crystalline silica. The guidelines state that health surveillance should be conducted for every worker at entry and exit to crystalline silica work, and at least every 5 years during dust exposure. The aim is to record workers’ baseline and subsequent test results so that any silica-caused deterioration to lung function can be identified and addressed.

The Queensland Respirable Crystalline Silica (RCS) medical includes:

• Respiratory medical and occupational exposure history
• Medical examination
• Spirometry (lung function) test
• Medical review and sign off
• Chest X-ray (ILO standard)

How can KINNECT help?

Establishing periodic monitoring for workers that encounter crystalline silica is an important preventative measure that will ensure you are meeting your duty of care to keep your workers healthy, safe and productive.

At KINNECT, we offer the Queensland Respirable Crystalline Silica (RCS) medical for mine and quarry workers, and the Safe Work Australia Crystalline Silica medical. These follow the respective state department and national guidelines.

References

1. https://www.dnrm.qld.gov.au/__data/assets/pdf_file/0006/1263669/qgl02-guideline-mines-quarries.pdf
2. https://www.safeworkaustralia.gov.au/silica#overview
3. https://www.worksafe.qld.gov.au/__data/assets/pdf_file/0015/83130/silica-lung-factsheet.pdf
4. https://www.safeworkaustralia.gov.au/system/files/documents/1702/guide-pcbu-health-monitoring-exposure-hazardous-chemicals.pdf
5. https://www.racp.edu.au/advocacy/division-faculty-and-chapter-priorities/faculty-of-occupational-environmental-medicine/accelerated-silicosis
6. https://www.notimetolose.org.uk/wp-content/uploads/2018/03/Factsheet_Respirable_crystalline_silica_the_facts_MKT2730.pdf
7. http://www.health.gov.au/internet/main/publishing.nsf/Content/chronic-kidney
8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3266824/