Silica Dust COSHH Assessment: What UK Employers Must Do

Why Silica Dust Deserves Its Own COSHH Assessment

Silica dust is not just another COSHH substance. It is one of the most serious occupational health hazards in UK construction, engineering, and manufacturing — and it is invisible. The particles that cause disease are respirable crystalline silica (RCS), too fine to see with the naked eye, generated whenever silica-containing materials are cut, drilled, ground, or sanded.

Long-term exposure causes silicosis, an irreversible scarring of the lung tissue that reduces lung function progressively and permanently. There is no cure. Acute silicosis — from very high short-term exposure — can be fatal within weeks. The connection between silica dust and lung cancer, COPD, and kidney disease is also well-established.

For all these reasons, HSE guidance makes clear that silica dust cannot be managed with a generic dust section in a general COSHH assessment. It warrants its own assessment, its own monitoring, and its own health surveillance programme.

What Materials Contain Silica?

Silica (silicon dioxide) is one of the most common minerals in the earth's crust. The materials you encounter on construction sites that contain crystalline silica include:

Concrete and cement — typically 25–70% silica content depending on mix (HSE construction dust guidance)
Bricks and clay blocks — typically 30–50% silica
Sandstone and natural stone — typically up to 90% silica in quartzite
Granite — typically 25–30% silica
Mortar and render
Ceramic tiles
Engineered stone products — kitchen worktops and similar composite materials (very high silica content, typically 90%+)

Silica becomes hazardous when it is disturbed. Intact concrete or stone sitting on a pallet poses no risk. Cutting, grinding, drilling, blasting, or demolishing those materials releases RCS into the air.

The Workplace Exposure Limit for Silica Dust

The workplace exposure limit (WEL) for respirable crystalline silica is 0.1 mg/m³ expressed as an 8-hour time-weighted average. This figure comes from the EH40 Workplace Exposure Limits document published by the HSE.

That is a very low threshold. For context, 0.1 mg/m³ is well below the level at which RCS becomes visible to the eye. Uncontrolled cutting of concrete or grinding of stone can produce exposures many times higher than 0.1 mg/m³ in a matter of minutes.

The HSE treats respirable crystalline silica as a carcinogen, and both HSE guidance and good practice require employers to reduce exposure to "as low as is reasonably practicable" under COSHH Regulation 7 — consistent with the hierarchy of control applied to other serious respiratory hazards. Meeting the WEL is necessary, but it is not sufficient — you must continue to drive exposure down.

Conducting a COSHH Assessment for Silica Dust

A silica dust COSHH assessment follows the same structure as any COSHH assessment, but with specific content driven by the characteristics of RCS.

Step 1: Identify the tasks that generate silica dust

Start by listing every work activity that involves silica-containing materials. Be specific about the task — not just "concrete work" but the exact operations:

Disc cutting or angle grinding concrete
Core drilling through concrete floors or walls
Brick cutting with a petrol saw
Block grinding or rubbing
Grit blasting stonework
Breaking out concrete with a breaker
Demolition of masonry

Each task will have a different exposure profile. Dry cutting with an uncontrolled petrol saw generates far higher exposures than wet cutting or on-tool extraction — so each task needs its own control assessment.

Step 2: Assess the exposure level

The HSE's COSHH Essentials guidance and the silica-specific control guidance sheets (available at hse.gov.uk/coshh/essentials) give task-by-task exposure estimates. For higher-risk tasks, employers may need to commission air monitoring to measure actual exposures using personal sampling equipment — a service provided by occupational hygienists.

You do not need to measure exposure for every task. A competent assessment can use the HSE's own exposure bands and published data to determine whether existing controls are likely to reduce exposure below the WEL. Air monitoring becomes essential when:

Tasks are prolonged or frequent
Controls cannot be fully applied (enclosed spaces, overhead work)
Workers show symptoms of respiratory or skin problems
There is any doubt about whether the WEL is being met

Step 3: Apply the hierarchy of control

COSHH Regulation 7 requires employers to apply the hierarchy of control. For silica dust, working down that hierarchy looks like this:

1. Elimination — Remove the source of silica dust entirely. This is rarely possible, but redesigning the work sometimes is: pre-formed openings eliminate cutting; factory-cut components reduce on-site generation.

2. Substitution — Use lower-silica materials where possible. Engineered stone worktops have very high silica content; natural stone alternatives may be lower-risk. Specify wet-cast concrete products that eliminate cutting.

3. Engineering controls — This is where most control effort sits for silica dust:

On-tool water suppression: Built into most modern disc cutters and core drills. Wet cutting reduces airborne silica by over 90% compared to dry cutting.
On-tool dust extraction (LEV): Vacuum attachments fitted directly to the tool capture dust at source. These must be H-class (HEPA-rated) vacuums — not standard industrial or domestic machines.
Enclosed processes: Cutting booths or dedicated enclosures with extraction ventilation for high-frequency operations.

4. Administrative controls — Rotate workers to reduce individual exposure duration; exclude non-essential personnel from the cutting area; schedule high-dust tasks when fewer people are present.

5. RPE (respiratory protective equipment) — RPE is required when engineering controls alone cannot bring exposure below the WEL, and as a backup control for residual risk. For silica dust, the minimum standard is a P3-rated half-mask respirator, giving an assigned protection factor of 20. For sustained work with heavy dust generation, powered air-purifying respirators (PAPR) with P3 filters are more appropriate.

RPE must be fit-tested, regularly maintained, and replaced on schedule. A P3 disposable mask that has never been face-fitted and is worn by a worker with a beard provides minimal protection.

Step 4: Record the assessment and review it

Record what tasks are involved, what the likely exposure levels are, what controls are in place, and what monitoring and surveillance will be applied. The assessment must be reviewed whenever there is a change in materials, tasks, or controls — and regularly as a matter of good practice, commonly at least every two years.

Health Surveillance for Silica Dust Exposure

COSHH Regulation 11 requires health surveillance "where appropriate" — and for workers regularly exposed to silica dust, the HSE is clear that it is appropriate.

Health surveillance for silica exposure typically involves:

Baseline pre-placement lung function test (spirometry) — establishes a personal benchmark before work begins
Annual questionnaire and symptom check — shortness of breath, persistent cough, changes from baseline
Periodic spirometry — frequency determined by risk level; typically every 1–3 years for regular silica workers
Chest X-ray — in some occupational health programmes for higher-risk exposures, to detect early nodular changes

Health surveillance must be conducted or overseen by a competent occupational health professional. Results must be kept in a confidential health record for 40 years — silicosis can take decades to develop, and the latency period means employment records and health data must be retained long after the work ends.

Who Carries the Duty?

Every employer whose workers are regularly exposed to silica dust has COSHH duties. That includes:

Main contractors on construction sites, for their own employees and for the effect their managed activities have on subcontractors
Subcontractors, for their own employees
Stonework and masonry contractors
Worktop fabricators (especially engineered stone — this is currently one of the HSE's enforcement priorities)
Demolition contractors
Quarrying and mineral extraction businesses

The duty does not disappear because the work is short-duration or because you are a subcontractor on someone else's site. If your employees are cutting concrete, you own the COSHH duty for their silica exposure.

Common Failures the HSE Finds

Enforcement action for silica dust tends to cluster around the same failures:

Dry cutting without suppression or extraction. Petrol disc cutters used dry without water or extraction generate some of the highest silica exposures encountered in inspection. This is illegal and HSE will issue Prohibition Notices on the spot.

RPE as the primary (or only) control. Putting workers in P3 masks and continuing to dry-cut is not an adequate control hierarchy. RPE sits at the bottom of the hierarchy for good reason — it fails when not worn, not fitted, or not maintained.

Generic COSHH assessments that do not address specific tasks. "Risk of dust — wear mask" in a toolbox talk does not constitute a suitable and sufficient COSHH assessment for silica.

No health surveillance. Many employers conducting regular silica-dust-generating work have no occupational health arrangements in place at all.

H-class vacuum misidentification. Operators using M-class or standard industrial vacuums for silica dust cleanup. Only H-class (HEPA) vacuums provide adequate filtration for RCS.

Linking Silica Dust to Your Wider COSHH Programme

A silica dust assessment does not sit in isolation. It links to:

Your COSHH control measures programme — silica is the primary application of the engineering controls hierarchy on most construction sites
Your LEV testing and maintenance schedule — on-tool extraction systems need the same 14-month thorough examination as any other LEV system under COSHH Regulation 9
Your COSHH training programme — workers need to understand what silica is, why it matters, and how to use the controls correctly
Your substance register — every silica-containing material in regular use should be listed, with the relevant COSHH assessment cross-referenced

For more on the dust and fume hazards your workers face across the whole site, see our construction site COSHH guide.

Making Silica Dust Compliance Manageable

Managing silica COSHH assessments on paper across a construction site — task by task, worker by worker, with monitoring and health surveillance records — is genuinely complex. The assessment is not the hard part. The hard part is ensuring the controls are in place every day, that RPE is being worn correctly, that vacuums are being maintained, and that health surveillance is booked and followed up.

COSHHmate is being built to centralise that process — assessments, monitoring records, health surveillance reminders, and team access to control requirements in one place. If you want to hear when it launches, join the waitlist.

This guide is for information only and does not constitute legal advice. COSHH obligations for silica dust depend on specific tasks, materials, durations, and control measures in your workplace. The definitive sources are the Control of Substances Hazardous to Health Regulations 2002 and HSE guidance at hse.gov.uk/coshh.

Sources

HSE: Silicosis — causes and risk controls (hse.gov.uk)
COSHH Regulations 2002, Regulation 7 — Adequate control of exposure to substances hazardous to health (legislation.gov.uk)
COSHH Regulations 2002, Regulation 11 — Health surveillance (legislation.gov.uk)
Control of Substances Hazardous to Health Regulations 2002 (SI 2002/2677) (legislation.gov.uk)
HSE COSHH Essentials — control guidance sheets including silica dust (hse.gov.uk)