Silica Dust in Construction Trades: Bricklaying, Concreting and Plastering

The construction industry employs hundreds of thousands of Australian workers, many of whom perform routine tasks that generate respirable crystalline silica (RCS) at concentrations far exceeding the 0.05 mg/m³ Workplace Exposure Standard. Dry cutting concrete, grinding brick, sawing tiles, chasing walls for electrical and plumbing services — these everyday construction activities can produce dangerous RCS exposure when performed without adequate controls. Unlike the engineered stone industry (which has received significant regulatory and media attention), silica hazards in general construction trades are often overlooked and under-resourced.

Silica-Containing Materials in Construction

Many common construction materials contain crystalline silica. Percentage estimates (silica content as % of total material mass):

• Concrete and cement products: 25–70% (from aggregate and sand)
• Sand and gravel: Up to 95% quartz
• Brick and pavers: 20–60%
• Mortar and render: 20–50% (sand-based)
• Roof tiles (terracotta and concrete): 25–60%
• Ceramic and porcelain floor tiles: 5–30%
• Sandstone and granite (natural stone): 15–30%
• Fibre cement sheeting (Hardie products): 30–50% crystalline silica
• Engineered stone (quartz agglomerate): 90–95% — highest risk material

Importantly, the RCS content of the airborne dust generated by cutting or grinding a material may differ from the silica content of the bulk material. Liberation of fine crystalline silica during cutting depends on the cutting method, tool type, and material composition. NATA-accredited XRD analysis of collected dust samples determines the actual RCS fraction of generated airborne dust.

High-RCS Tasks in Construction Trades

Angle Grinding and Dry Cutting

Dry angle grinding of concrete, brick, mortar joints or tiles generates the highest RCS concentrations of any common construction task. Studies consistently measure RCS concentrations of 1–10 mg/m³ — 20–200× the WES — at the operator’s breathing zone during uncontrolled dry grinding. Dry cutting of concrete with a disc saw (without water) produces similar concentrations. These exposures are simply incompatible with the WES regardless of work duration. Dry cutting without engineering controls is not reasonably practicable for silica-bearing materials.

Core Drilling Concrete

Dry core drilling produces a plume of fine silica-rich concrete dust from the core exit point. Wet core drilling (water through the drill bit) dramatically reduces RCS generation. On-tool vacuum extraction for dry drilling operations is available and required where wet drilling is not practicable.

Chasing Walls and Floors

Wall chasing (creating channels in brick or concrete walls for services) generates intense RCS exposure. Electric wall chasers without extraction produce RCS concentrations 50–200× the WES. On-tool extraction with an H-class vacuum is the mandatory control — available for all common wall chaser models through compatible shroud attachments.

Bricklaying and Block Cutting

Cutting bricks and blocks with an angle grinder (the most common site method) is extremely high risk. A tile saw with water suppression is the preferred alternative for cut-to-size bricks and pavers. Where angle grinder cutting must be used (irregular cuts), on-tool extraction attachment or wet suppression is required.

Plastering and Rendering

Bag-mixing plaster, render and grout generates dust during mixing, particularly when powders are manually emptied into mixers. Inhalable dust (including silica from sand-based products) can be significant. Use of pre-mixed products in buckets (eliminating dry bag mixing) is the preferred control. Where dry mixing is unavoidable, local exhaust ventilation at the mixing area reduces exposure.

Demolition Activities

Breaking up concrete with jackhammers and breakers generates RCS in high concentrations from impact fragmentation. Water suppression at the breaker tool, combined with respiratory protection, is required. Demolition of silica-bearing structures should be assessed for RCS exposure before work commences.

Principal Contractor Duties for Silica on Construction Sites

Under the model WHS Act, the principal contractor for a construction project has a primary duty to ensure, so far as is reasonably practicable, that workers on the site are not exposed to health risks — including from RCS generated by sub-contractors’ work. This duty cannot be discharged simply by requiring sub-contractors to have their own WHS management systems. The principal contractor must:

• Ensure the site WHS management plan identifies silica-generating tasks and mandated controls
• Include silica control requirements in sub-contractor pre-qualification and site induction
• Actively enforce wet cutting/on-tool extraction requirements through site walk-throughs and stop-work authority
• Provide or require provision of health surveillance for workers performing regular high-exposure tasks
• Stop non-compliant dry cutting as an immediately observable unsafe condition

Regulators have increasingly exercised powers to issue prohibition notices against dry-cutting on construction sites. Principal contractors who permit ongoing non-compliant practices face category 2 and category 1 WHS liability.

Mandatory Control Package for Construction Silica

The minimum control package for silica-generating construction tasks:

1. Wet cutting as default: Water suppression at blade/disc for all concrete, tile, brick and stone cutting where feasible
2. On-tool extraction where water is impractical: H-class vacuum with OTE shroud for angle grinders, wall chasers, core drills
3. P2 respirator as minimum RPE: For any silica-generating task regardless of engineering controls. P3 for high-intensity dry grinding where engineering controls are inadequate
4. HEPA vacuum for cleanup: No dry sweeping or compressed air in areas where silica dust has settled
5. Health surveillance: For workers regularly performing silica-generating tasks — baseline and periodic chest X-ray and spirometry