Breathing below ground: respirable crystalline silica risk

The discussion about exposure to silica dust in the workplace is currently receiving a great deal of air-time across Australia. Unions are calling for more rights to conduct measurements of airborne contaminants underground, while state and federal governments have tasked Safe Work Australia to conduct a review into placing a ban on engineered stone in Australia. However, although the risks of silica dust are becoming more widely understood, many workers are still experiencing high levels of exposure. So what level, if any, is “safe”, and what can be done to better protect them?

Miners and underground workers at risk

While much of the discussion surrounding respirable crystalline silica has been in relation to the use of engineered stone, there are workers in a wide range of industries who are at risk of developing silicosis.

In fact, a 2016 study found that 6.6% of the total Australian workforce were exposed to respirable crystalline silica (RCS), and 3.7% were “highly exposed” when carrying out tasks at work. Miners and construction workers were “most likely to be highly exposed to RCS when performing tasks with concrete or cement or working near crushers that create RCS-containing dusts.”¹

According to the Lung Foundation Australia’s draft National Silicosis Prevention Strategy 2023–2028 and accompanying National Action Plan — which was opened for public consultation in early 2023 — workers are generally at risk of silica exposure “if any material containing quartz is liberated from the natural environment (such as mining and quarry work), or when silica is used in industrial and manufacturing processes”. The report suggests that the occupations with the highest proportion of workers exposed to high levels of silica dust are therefore miners, construction workers, plumbers, handypersons and engineers.²

What steps can be taken to protect underground workers?

The best protections for workers involve “higher-order controls”, which are measures that aim to prevent dust from being generated in the first place.

However, Tracey Bence, Fellow and President of the Australian Institute of Occupational Hygienists, said that in many high-risk industries, these types of controls are not being used enough to prevent silicosis.

“That’s where the use of high-grade personal protective equipment comes in,” Bence said.

“In those cases, it’s really about understanding how to best use tight-fitting respirators — sometimes called P2 dust masks. For instance, when they need to be worn, and for how long — because the harmful silica dust is fine and hangs in the air even after the grinding, cutting, crushing and drilling stops. Respirators like these dust masks require a personal fit-test and workers will need training to appreciate how masks are to be worn if they are really going to protect them.”

The Australian Workers Union (AWU) has called for immediate reform that enables unions to have better access to worksites to monitor dust levels. AWU National Secretary Daniel Walton said union officials needed clear rights to conduct measuring of airborne contaminants underground.

“Right now, in most states, if our officials try to get onsite with a dust monitor device they are blocked,” Walton said.

“Yet we know silica exposure is all but certain to be occurring at dangerous levels. Our members are working in environments so dusty they can’t see more than 50 metres in front of them. They’re getting covered from head to toe in dust and they walk out with that dust on them which continues to spread.

“We also know it’s common for companies to operate for days despite ventilation breaking down. We know sites where water suppression is non-existent. And we know flimsy or damaged face masks are being regularly offered as PPE.

"We need union officials to be able to walk into a tunnelling site at any time to test if dust levels are unsafe. Companies should also have to automatically supply all dust monitoring results to the regulator and union promptly, instead of the drawn-out process that exists today,” he said.

Bence said that while most companies were trying to do the right thing, “unfortunately though, dust prevention is not consistent. We know that some workplaces do not undertake any air monitoring, or when they do, they do not act on the results where exceedances of the Workplace Exposure Standard occur. Occupational hygienists know that only air monitoring will demonstrate that the invisible silica dust hazard is there and whether it is at harmful levels — so yes, air monitoring is critical.”

Best practice for ensuring underground air quality

According to Bence, companies following best practice should engage a Certified Occupational Hygienist; put significant effort into ventilation design, job planning and engineering controls focused on preventing dust emission; regularly review how effective their controls are; routinely measure silica dust exposure, and take prompt action where improvements are needed.

Occupational hygienists utilise personal sampling and analysis techniques to determine how much dust an individual worker is inhaling, as well as small and portable monitoring devices. However, companies also need to be aware of overall dust levels on the worksite, and there is a range of technology available for occupational and environmental monitoring purposes.

“Newer developments in environmental monitoring and area sampling technology mean companies are now able to monitor the air in an entire plant or underground area with a series of sensors to work out where the dust is coming from. These days the devices are getting smaller and cheaper, so we can use more of them and protect more people,” Bence said.

“Silica dust is a microscopic hazard, whereas with something like working at heights the dangers are very apparent and comparatively easier to resolve. One difficulty with underground areas is that they often require extensive ventilation systems — and these are not easy to design, build and implement. They are also expensive to keep running and to put in place after an airborne hazard has already been realised. So it’s better to recognise from the outset that a project is going to create silica dust, and get the ventilation system in place from the beginning, as part of the way a company does business. If employers can do that, then everyone’s health can be protected.”

Bence also recommends increased company-wide training to support greater awareness on the issue of respirable crystalline silica and other harmful particles that may be in the air.

“Our free Breathe Freely program has several sections for construction, quarrying, mining, engineered stone and welders. The training is available here: www.breathefreelyaustralia.org.au, for free — for any worker or employer — they just have to pick it up and roll it out,” she said.

^{[1] https://pubmed.ncbi.nlm.nih.gov/26888888/}

^{[2] https://lungfoundation.com.au/wp-content/uploads/2023/02/NSPS-NAP-Fifth-Full-Draft-Copy-for-Public-Consultation.pdf}

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