Understanding silica exposure risk: insights from Dean Gleeson

Dean Gleeson

Dean Gleeson joined Tetra Tech in 2021and is a Principal Occupational Hygienist for the WHS team in Sydney, Australia. He is part of a national team that provides occupational hygiene risk management services for clients in construction, infrastructure, energy and resources sector. With work spanning the past 20 years has seen him manage WHS risk on some of the region’s largest infrastructure projects. Here he shares his insights on the steps being taken to protect the health of workers from exposure to silica dust.

As a Certified Occupational Hygienist, I have a passion for protecting the health of workers. Exposure to silica dust in the construction industry is one of the most significant health risks impacting the highest number of workers, second only to noise.

Silicosis is an entirely preventable disease that causes fibrosis of the lungs from the inhalation of silica dust, and from 1 September 2024, the stronger regulation of all crystalline silica substances comes into effect in Australia

Who is most at risk?

There has been a lot of attention lately on engineered stone due to the incidence of accelerated silicosis in stone masons.

But the issue is not unique to engineered stone and people need to understand that silica can be found in a range of natural and manufactured materials, including shale, sandstone, concrete, bricks, tiles, pavers and masonry.

Hazardous exposures to silica dust are most likely to occur when crystalline silica substances are processed with power tools or mechanical plant during activities including crushing, cutting, jackhammering, trimming, sanding, drilling, polishing or during any other activities which create fine dust. Cleaning up by dry sweeping is another significant source of exposure as settled dust is resuspended.

 

What are the challenges regarding industry compliance?

Several tier one contractors, especially those that work in high-risk industries such as tunnel construction have been managing silica exposure risks for many years, and as such implement robust controls proven effective through exposure monitoring programs.

However, many smaller companies and subcontractors might not be fully prepared for legislative changes. Because adverse health effects associated with silica exposures usually have a latency of several decades from beginning of exposure to the development of symptoms, the perception of exposure risk is generally underestimated.

It is really important that broader awareness increases and employers, in consultation with workers, adequately assess the risk of exposure to silica dust, implement effective controls, and conduct exposure monitoring to verify that the controls are effective.

Undertaking a statistically based exposure monitoring program developed by a competent person, such as a Certified Occupational Hygienist, is the only way to understand if the controls being implemented are managing exposures to below the workplace exposure standard.

Our team are actively involved in silica exposure assessments on several major infrastructure projects that involve tasks that are high risk for silica exposure. Because we get to work with many different employers, we get to see a variety of different controls measures being used and we have the statistically validated exposure monitoring data to understand what controls are effective and how to optimise controls.

How do we control exposure to silica dust?

The WHS regulations have always required that risks to health, such as exposure to silica dust are risk assessed and controlled. What the changes to the legislation coming in on the first of September do bring is a more prescriptive way of assessing the risk of exposure to silica dust, establishing minimum requirements for controls and the requirement to notify the regulator of air monitoring results that exceed the workplace exposure standard.

When developing a control strategy, it is important that we consider a thing called the hierarchy of control.

Personal protective equipment or PPE is at the bottom of the hierarchy, but a dust mask is often the only control that is used. PPE is the least effective type of control because it doesn’t actually control the hazard; it just protects the person wearing the PPE. So, it relies on the person to use it properly and using it when needed. If we’re talking about dust masks the most common type relies on forming a seal on the person’s face. Dust masks need to be fit tested to ensure that they fit the wearer’s face and form an effective seal. Facial hair interrupts this seal meaning that workers who grow facial hair need to be clean shaven where the dust mask contacts the skin. This can be an issue where facial hair is grown for cultural reasons. Also, construction workers work long hours and have early starts, so getting up earlier and shaving before work every day is going to be a change for a lot of people.

Another limitation of dust masks what we call wear time. This means wearing the mask for the whole amount of time that you’re in an exposure scenario. The hazardous silica dust, known as respirable crystalline silica is very small, small enough to penetrate to the lower part of the lungs. Respirable dust is so small it is not visible and it stays airborne for a very long time. Once the dust generating task is completed, if it is in an indoor environment the respirable dust is going to be in the air for the rest of the day.

If workers take the mask off because they’ve finished doing the dust generating task, they are still getting exposed, and that respiratory protection is completely ineffective. So going back to the hierarchy of control with the first thing is to eliminate the hazard where we can.

That’s going to be pretty hard with silica because it’s in so many construction materials and natural rock. Silica is everywhere, so it can’t be eliminated.

It’s very important that we that we use the hierarchy and we implement controls everywhere that’s reasonably practicable. While we may not be able to eliminate silica from concrete, we can eliminate the need to drill into it by casting in situ ferrules, fittings or tracks for the fit out of a building. Where possible materials should be substituted for products that contain less silica. Or work processes could be substituted, for example using a method or a tool that generates less dust.

The cabins of mobile plant when fitted with HEPA filtration systems, maintained in a clean standard and operated with doors and windows closed are a very effective isolation control. Engineering controls include effective water suppressions systems or on tool dust extraction. A worker standing and holding a garden hose on a dust generating task is not effective. We see this all the time in civil construction and demolition. Not only does it not control dust, it puts a worker in a position where they are exposed to the dust, high noise and a risk of being stuck by powered mobile plant.

Finally, administrative controls such as training, policies and procedures should be implemented before we come to the bottom of the hierarchy, the PPE.

Raising awareness for silicosis prevention

Our national team of Occupational Hygienists are working with our industry associations and our clients to raise awareness about legislative changes and key risk environments associated with crystalline silica exposure. Tetra Tech delivered a range of services targeted at awareness including stakeholder engagement, training and implementing and verifying effective control solutions.

We really want to emphasise that it is collective effort of workers, employers and industry to work together to raise the importance of awareness and steps they can take to protect themselves and help workers who are at the highest risk of dust exposure.

This change in legislation should help drive an understanding of what activities create a risk of overexposure to silica. Implementing higher order controls and not relying on PPE is going to be a cultural change in many industry sectors and it’s going to take a fair bit of time.

But I am optimistic. In the last decade in the tunnelling industry I have seen a change to the culture and attitudes to dust management, which is really positive and I think an increase in regulation, including the requirement to report over exposures to the regulator is going to see a change in how things are done. Hopefully the regulator gets out there and is a lot more proactive in industry, especially when it comes to things like whether employers are doing air monitoring, whether they are actually understanding what their exposures are and whether they’re verifying that the controls that the new regulations say you need to put in place are actually effective so we can ensure that we are protecting the health of workers.

Connect with Dean Gleeson Principal Occupational Hygienist East Coast and New Zealand – [email protected]

Be Silica Smart – Resources

For workers and employers seeking more information, visit:

Safe Work Australia resources page includes links to relevant information on silica dust in each state and territory.

WORKSAFE Mahi Haumaru Aotearoa resources page provides information about how to prevent exposure risks and monitoring health.

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