Dust Control in Tunnel Construction & Silicosis Prevention

Dust Control for Tunnel Construction: Preventing Silicosis in Australia’s Largest Infrastructure Programme

One in every ten underground tunnel workers in Queensland is estimated to develop silicosis over their lifetime. This is the finding of peer-reviewed research published in the Annals of Work Exposures and Health in November 2025, authored by Cole, Carey and Driscoll. The researchers analysed air monitoring data from three major Queensland tunnel projects and modelled the long-term disease burden. Their conclusion: among a cohort of approximately 2,000 workers, between 200 and 300 would develop silicosis and between 20 and 30 would develop lung cancer as a direct result of respirable crystalline silica exposure during tunnelling.

That finding mirrors a 1924 government inquiry into sewer construction in Sydney. A century of technological advancement has not changed the disease rate for tunnel workers. The researchers observed that it does not seem things are any better in terms of silicosis risk in underground work than a century ago.

Australia is in the middle of the largest tunnel infrastructure programme in its history. Rail construction activity is expected to peak at $17.3 billion in 2025–26. Sydney Metro West has awarded $7.7 billion in new contracts, with tunnelling targeted for completion in 2026. The Suburban Rail Loop in Melbourne is commencing tunnelling in 2026. Cross River Rail in Brisbane features tunnels beneath the Brisbane River. Western Sydney Airport Metro is driving TBMs through sandstone. Thousands of workers are underground right now, cutting through silica-bearing rock and concrete.

No dust suppression company has published comprehensive guidance on tunnel construction dust control. The tunnelling industry relies on ventilation engineering, water sprays and PPE — the same approach that has produced the 1-in-10 silicosis rate. This article covers what is different about tunnel dust, why current approaches are producing unacceptable disease rates, and how chemical activation of spray water can close the gap between what water alone achieves and what worker health requires.

The Scale: Australia’s Tunnel Infrastructure Pipeline

Major Australian tunnel projects: active and upcoming

The combined workforce across these projects numbers in the tens of thousands. If the Cole, Carey and Driscoll disease rate applies — and their research suggests it does, based on analysis of actual air monitoring data from Queensland tunnel projects — then hundreds of these workers are at risk of developing silicosis over their lifetimes from exposures occurring right now. NSW alone has recorded 516 cases of silicosis and 36 deaths from the disease since 2017. SafeWork NSW has conducted over 100 site inspections at tunnelling sites in the Sydney metropolitan area since January 2024.

Why Tunnel Dust Is Different: Confined Space, Continuous Generation, Maximum Silica

Tunnel construction dust differs from surface construction or mining dust in three critical ways that make it more hazardous and harder to control.

Confinement. There is no atmospheric dilution. Every particle of respirable dust generated at the tunnel face remains in the tunnel atmosphere unless the ventilation system removes it. On a surface construction site, wind disperses dust over a large area, reducing the concentration at any single point. Underground, the dust is contained within a tube — the tunnel bore itself — and the concentration builds continuously as cutting progresses. Workers in the tunnel are immersed in the dust their work generates, with no ability to move upwind or increase separation distance.

Continuous high-energy generation. Tunnel boring machines (TBMs) and roadheaders operate continuously during excavation shifts, fracturing rock and concrete at high energy for hours at a time. A TBM’s cutterhead rotates against the rock face under enormous thrust, generating a continuous stream of cuttings and fine dust. Roadheaders used for station cavern and cross-passage excavation apply similar energy to smaller areas. Drill-and-blast methods fracture rock explosively. Shotcreting (spraying concrete for tunnel lining) generates aerosolised cement and silica dust. Every primary tunnelling activity produces respirable crystalline silica at rates that are among the highest of any construction process.

High silica content. The rock types encountered in Australian tunnel construction are typically high in crystalline silica. Sydney’s Hawkesbury sandstone contains 60–90% quartz. Brisbane’s sedimentary formations contain substantial silica. Melbourne’s basalt contains lower silica than sandstone but still exceeds the 1% Chapter 8A threshold. Concrete used for shotcreting, segments and structural elements contains 25–50% silica. The material being cut, blasted, drilled, sprayed and loaded at every stage of tunnel construction is a crystalline silica substance — and the dust it generates carries silica concentrations that directly threaten the lungs of every worker in the tunnel.

The Data Opacity Problem: What We Know and What We Don’t

The Cole, Carey and Driscoll research highlighted a fundamental barrier to improving tunnel worker health: data opacity. While tunnel projects are required to conduct air monitoring, the results are not routinely made public. The researchers obtained their data from a 2017 Queensland parliamentary inquiry — not from routine disclosure by the project operators.

The researchers noted that continued secrecy around silica dust data reduces our ability to understand the scale of the problem and respond effectively. A 2024 media investigation revealed that one-third of air monitoring tests from a Sydney tunnel project exceeded legal limits — information that only became public through investigative journalism, not through the project’s compliance reporting.

This opacity means that the true exposure profile of Australian tunnel workers is largely unknown outside the projects themselves. What is known — from the limited data that has been disclosed — supports a 1-in-10 lifetime silicosis risk. The actual rate may be higher or lower, but without systematic public reporting, the industry is flying blind. The NSW Government’s decision to review the Tunnels Under Construction Code of Practice (which had not been updated since 2006) and SafeWork NSW’s programme of over 100 tunnel site inspections since January 2024 signal regulatory recognition that the current approach is inadequate.

The Regulatory Framework: Chapter 8A Applies to Every Tunnel

Chapter 8A of the WHS Regulations (effective 1 September 2024) applies to every tunnel construction project in Australia. Tunnelling through rock, concrete, shotcrete or any material containing ≥1% crystalline silica is explicitly a crystalline silica process. High-risk crystalline silica work — which tunnelling unequivocally is — requires a silica risk control plan, accredited training, air monitoring and health surveillance.

The NSW Government has opened consultation on a new Tunnels Under Construction Code of Practice, replacing the 2006 version. The updated code will incorporate Chapter 8A requirements, strengthened monitoring obligations and contemporary engineering control expectations. For projects currently in construction, the existing code and Chapter 8A both apply. For projects entering construction in 2026–27, the updated code will set the standard from the outset.

The December 2026 reclassification of the RCS workplace exposure standard from WES to WEL (Workplace Exposure Limit) adds further regulatory force. The 0.05 mg/m³ limit will become a hard ceiling with strengthened enforcement. Victoria is already targeting 0.02 mg/m³. For tunnel projects where air monitoring has historically shown one-third of tests exceeding the current standard, the compliance challenge is existential.

Why Water-Only Suppression Fails in Tunnels

Every TBM, roadheader and drill jumbo is equipped with water spray systems. Water is delivered at the cutterhead, at the muck conveyor, at transfer points and through the ventilation system. These systems suppress the visible dust effectively — the larger particles are wetted and knocked down. But the 1-in-10 silicosis rate demonstrates that the visible dust is not what causes the disease.

The respirable fraction — particles below 10 μm, and particularly the sub-4 μm fraction that penetrates deepest into the lungs — resists capture by plain water through the same mechanisms that limit water-only suppression in any underground mining application. Freshly fractured silica surfaces are hydrophobic. The finest particles deflect off water droplets rather than being captured. The spray droplets are orders of magnitude larger than the dust particles they need to intercept. And the high-velocity air streams around the cutterhead and through the ventilation circuit carry fine particles away from the spray zone before contact can occur.

The ventilation system dilutes the concentration but does not eliminate it. In a tunnel that may be several kilometres long, with the face advancing away from the portal, the ventilation path lengthens progressively. Workers at the face, at the trailing gear, on the muck conveyor and in the cross-passages are all exposed to dust that the ventilation system is managing but not removing. The further the face advances from the portal, the more challenging the ventilation design becomes and the higher the residual dust concentrations in the tunnel atmosphere.

Chemical Activation: Making Every Spray Point in the Tunnel 12 Times More Effective

GRT: Activate UG was originally developed for underground coal mining, where the same hydrophobic dust challenge exists. The product’s four modes of action — rapid surface tension reduction (72 kN/m to <42 kN/m in 1/100th of a second), ionic charge attraction of hydrophobic particles, synergistic performance in mine water, and ultra-low concentration effectiveness at 0.02–0.03% — are directly applicable to tunnel construction dust.

The product is dosed into the water supply feeding the TBM or roadheader’s spray system at ratios between 1:1,000 and 1:5,000. It mixes readily with water and can be injected directly into water lines or added to holding tanks. No modification to the machine’s spray hardware is required. The existing nozzles, pressures and flow rates remain unchanged. The only difference is that the water emerging from those nozzles is now activated — capable of attracting and binding the fine, hydrophobic silica particles that plain water misses.

Independent testing has verified that GRT’s activation technology is 12 times more effective than water alone at suppressing fine dust. An independent effectiveness study conducted by the occupational hygiene team at a BMA underground coal operation confirmed that the product delivers meaningful dust reduction with large effect size when applied through existing spray systems. The technology is proven in underground conditions — confined spaces, limited ventilation, hydrophobic dust, high-energy mechanical cutting — precisely the conditions that characterise tunnel construction.

The GRT: Activate Ready Reckoner provides a straightforward dosing calculation: for a TBM using 100,000 litres of water per day for dust suppression, the daily Activate requirement is 50–100 litres at a 1:1,000 to 1:2,000 ratio. The cost per day is a fraction of the daily operating cost of the TBM itself — and the health outcome it protects against is an incurable, potentially fatal lung disease.

Application Points: Where to Deploy Chemical Activation in a Tunnel

Tunnel construction: dust sources and chemical activation points

The simplest deployment is to inject Activate UG into the main water supply for the tunnel. Every spray point connected to that supply — TBM sprays, conveyor sprays, ventilation mist sprays — automatically delivers activated water instead of plain water. This is the approach recommended in the Activate UG Technical Data Sheet: simple addition into the main water supply for underground operations will see the dust suppression benefits across all aspects of operations where water is sprayed.

For tunnel roadways and the invert surface where vehicle traffic generates dust, GRT: Wet-Loc provides waterless dust control. Applied neat to the tunnel invert, Wet-Loc eliminates the need for continuous watering of traffic surfaces underground — reducing both dust and the mud and slip hazards that excess water creates in confined tunnelling environments.

The Case for Immediate Action: Cost of Prevention vs Cost of Disease

The cost of dosing Activate UG into a TBM’s water supply is measured in hundreds of dollars per day. The cost of a single silicosis diagnosis is measured in hundreds of thousands of dollars in workers’ compensation, medical treatment, legal liability, regulatory investigation, project delay and reputational damage. For a project employing 2,000 tunnel workers where the peer-reviewed evidence projects 200–300 silicosis cases, the collective liability is measured in the tens of millions.

But the case for action is not primarily financial. It is human. Silicosis is an incurable disease that progressively destroys lung function, causes severe disability and can be fatal. The workers who are cutting through sandstone beneath Sydney right now, boring through basalt under Melbourne, and excavating beneath the Brisbane River do not know whether they will be among the 1 in 10. The engineering controls deployed today determine whether they will be.

The principal contractors responsible for these projects — and the government agencies that commissioned them — have an obligation to deploy every reasonably practicable engineering control that reduces respirable crystalline silica exposure at the face. Chemical activation of spray water is reasonably practicable: it uses existing infrastructure, requires no hardware modification, costs a fraction of the project budget, and is independently proven to be 12 times more effective than water alone. Not deploying it requires an explanation for why a proven, available, affordable engineering control was not used to protect workers from an incurable disease.

A Century of the Same Disease Rate Is Not Acceptable. The Technology to Change It Exists.

The 1924 inquiry into Sydney’s sewer construction found the same silicosis rate that the 2025 research found in Queensland’s tunnel workers. One hundred years of engineering advancement has not changed the outcome for the workers who build underground. That is not because the technology to protect them does not exist. It is because the technology has not been deployed.

GRT: Activate UG overcomes the hydrophobic barrier that makes plain water ineffective against fine silica dust. It works through existing TBM and roadheader spray systems. It has been independently validated in underground coal operations by one of Australia’s largest mining companies. It costs hundreds of dollars per day on a project costing billions. And it targets the specific particle size range — the sub-10 μm respirable fraction — that causes the disease these workers are being diagnosed with.

For tunnel project managers, construction managers, principal contractors and government infrastructure agencies responsible for Australia’s $100+ billion tunnel construction programme, the question is direct: the peer-reviewed evidence says 1 in 10 of your workers will develop silicosis. The engineering control that can change that number is available, proven and affordable. What reason is there not to deploy it?

Sources and References

Oxford Academic / Annals of Work Exposures and Health: Cole, Carey & Driscoll (2025) — The Future Burden of Silicosis and Lung Cancer Among Tunnel Construction Workers in Queensland, Vol. 69(9), pp. 917–926

The Conversation: 1 in 10 Tunnel Workers Could Develop Silicosis, Our New Research Shows (April 2025)

Health & Safety International: One in Ten Tunnel Workers Projected to Develop Silicosis, Study Warns (April 2025)

NSW Government: New Tunnelling Code Open for Consultation — 516 silicosis cases and 36 deaths in NSW since 2017; 100+ tunnel site inspections since Jan 2024

ENR: Sydney Launches Major Underground Metro Build with $7.7B in New Contracts (January 2026)

Rail Express: New Research Reveals Rail Investment Pipeline — $17.3B peak 2025–26, 94% east coast (December 2025)

Railway News: Melbourne Metro Rail 2026 Update — $12.8B, 9 km twin bores, opened November 2025

Construction Jobs Australia: 2025 Infrastructure Projects — SRL tunnelling 2026, Sydney Metro West TBMs, Cross River Rail

Safe Work Australia: Stronger Regulation of Crystalline Silica Substances — Chapter 8A

GRT: GRT: Activate UG — super-activated dust control for underground operations

GRT: GRT: 12X — independently verified 12× more effective than water

GRT: GRT: DC Binder — drill cuttings and blast pattern polymer binder

GRT: GRT: Wet-Loc — waterless dust suppression

GRT: SMART Dosing Units