Respirable Crystalline Silica: UK WELs & Control Guide

Summary

Crystalline silica is in almost everything tradespeople cut, grind, drill and chase: concrete, mortar, brick, block, stone, tiles, screed, granite and engineered/quartz worktops. When you work these materials dry with power tools, you generate a cloud of fine dust, and the smallest particles — respirable crystalline silica, around or below 10 microns — get deep into the lungs where they cause permanent, progressive scarring (silicosis), lung cancer and chronic obstructive pulmonary disease. The dust you can see settling is not the dangerous fraction; the dangerous fraction is the part you cannot see and that hangs in the air for hours. HSE estimates RCS exposure causes hundreds of construction deaths every year, and it is one of the most heavily enforced dust risks on UK sites.

This affects bricklayers, stonemasons, tilers, groundworkers, demolition crews, drylining and screeding teams, kitchen worktop fabricators and fitters, and anyone using a cut-off saw, angle grinder, wall chaser, breaker or core drill on masonry. The single biggest misconception is that "it's only dust" — RCS is a Group 1 human carcinogen, and there is no cure for silicosis. The second misconception is that a paper nuisance mask (FFP1) or a comfort mask gives protection — it does not; RCS needs FFP3 (or a powered hood) and only after engineering controls are in place. The third is that RPE alone is a control — under COSHH, RPE is the last resort, used to mop up residual risk after water or extraction has done the heavy lifting.

Control is well understood and cheap relative to the harm: cut wet, or use on-tool M-class extraction, keep people out of the dust, wear the right face-fitted RPE, and put exposed workers under health surveillance. Plan it in the method statement and price it in the quote.

Key Facts

• Workplace Exposure Limit (WEL) — RCS is 0.1 mg/m³, 8-hour TWA (HSE EH40 Workplace Exposure Limits). This is a maximum, not a safe level — keep exposure as low as reasonably practicable.
• Governing law — Control of Substances Hazardous to Health Regulations 2002 (COSHH), made under the Health and Safety at Work etc. Act 1974.
• Carcinogen status — crystalline silica (respirable) is classified as a Group 1 carcinogen by IARC; COSHH requires exposure to carcinogens to be reduced as low as reasonably practicable, below the WEL.
• Diseases caused — silicosis (irreversible lung scarring), lung cancer, chronic obstructive pulmonary disease (COPD), and is linked to kidney disease and autoimmune conditions.
• The danger fraction — respirable particles roughly ≤10 µm (and especially ≤4 µm) reach the deep lung; these are invisible and stay airborne for a long time.
• Hierarchy of control (COSHH Reg 7) — eliminate/substitute → engineering controls (water, LEV/on-tool extraction) → ways of working → RPE, in that order. RPE is last, not first.
• Water suppression — feeding water to the cutting point keeps dust down; it must be a continuous adequate flow, not a quick splash.
• On-tool extraction — capture dust at source with an M-class (or H-class) dust extractor matched to the tool. A standard workshop/wet-vac is not adequate for RCS.
• RPE for RCS — minimum FFP3 disposable or a reusable half-mask with P3 filters; powered/air-fed hoods (e.g. TH2/TH3) for long tasks or where face-fit to tight masks fails.
• Face fit testing — tight-fitting RPE (FFP3, half/full masks) legally requires a face fit test for each wearer, and the wearer must be clean-shaven at the seal.
• Health surveillance — required where exposure is significant; typically a respiratory questionnaire, lung function (spirometry) and, where indicated, chest imaging, with records kept for at least 40 years.
• Exposure monitoring — air monitoring may be needed to show the WEL is not exceeded (COSHH Reg 10).
• Housekeeping — never dry sweep or use compressed air to clean RCS dust; use an M/H-class vacuum or wet methods.
• CDM 2015 — designers and principal contractors must plan to design out or control silica risk; it's a foreseeable construction health risk.
• HSE guidance — HSG258 (Controlling airborne contaminants — LEV), plus HSE construction dust guidance (CIS36 and the "Construction dust" pages) and the WT (Welding/Wood/Stone) and Construction information sheets.

Quick Reference Table

Detailed Guidance

Knowing where the risk is

RCS is generated whenever you mechanically work a silica-containing material. Sandstone and quartz/engineered worktops are very high silica; concrete, mortar, brick and many natural stones are moderate to high. The risk scales with how energetically you work it (cut-off saws, grinders and breakers are the worst), how long the task lasts, how confined the space is, and whether the dust can clear. Indoor and enclosed work concentrates exposure dramatically — the same task that's risky outdoors can be far worse in a small bathroom or kitchen.

The hierarchy of control under COSHH

COSHH does not let you jump straight to a mask. The legal order is:

1. ELIMINATE   – can you avoid cutting? (order pre-cut/sized materials,
                 use cable routes instead of chasing, buy pre-mixed)
2. SUBSTITUTE  – lower-silica material? low-dust product?
3. ENGINEERING – water suppression OR on-tool M-class extraction
                 (this is the workhorse control for RCS)
4. WAYS OF WORKING – keep others away, limit task time, rotate, enclose,
                     good housekeeping, no dry sweeping
5. RPE         – FFP3 or powered hood, face-fit tested, as the LAST layer

If you find yourself relying only on step 5, the control is non-compliant.

Water suppression

Feeding water to the cutting point captures dust before it becomes airborne. It must be a continuous, adequate supply (pressurised bottle or mains feed), not a quick wetting. Check the water keeps running for the whole cut, deal with the slurry, and remember water and electricity need an RCD and sensible cable management. Wet cutting can reduce RCS exposure by an order of magnitude but only if maintained throughout.

On-tool extraction (LEV)

Where wet working isn't practical, capture dust at source with on-tool extraction: a shroud or guard connected to a dust extractor. For RCS the extractor must be at least M-class (medium hazard) — H-class for higher-risk work. The system (tool shroud + hose + extractor + filter) must be matched, maintained, and the extractor's filter-cleaning function used. LEV needs a thorough examination and test at least every 14 months under COSHH Reg 9, and HSG258 sets out how to design and check it.

Respiratory protective equipment (RPE)

RPE is the last line, never the only line. For RCS:

• Minimum FFP3 disposable or reusable half-mask with P3 filters.
• For long-duration, high-exposure, or wearers who can't get a tight-mask seal, use a powered air-purifying respirator / air-fed hood (TH2/TH3).
• Tight-fitting RPE must be face-fit tested for each individual and worn against bare skin at the seal — beards/stubble break the seal and void protection.
• RPE must be stored clean, inspected, and disposables changed as required.

Health surveillance and monitoring

Where exposure is significant despite controls, COSHH requires health surveillance — usually a baseline and periodic respiratory questionnaire and spirometry, escalating to chest imaging where indicated, overseen by an occupational health provider. Records must be kept for at least 40 years because silica disease can take decades to appear. Air monitoring (personal sampling) may be needed to demonstrate the 0.1 mg/m³ WEL is not exceeded and that controls work.

Housekeeping and waste

Settled RCS dust becomes airborne again the moment it's disturbed. Never dry sweep and never blow down with compressed air. Clean using an M-class or H-class vacuum or wet methods. Damp down, bag waste, and keep welfare/eating areas separate and dust-free so workers aren't ingesting silica.

Frequently Asked Questions

Is an FFP2 or "nuisance" dust mask enough for cutting concrete?

No. RCS requires a minimum of FFP3 (or a powered hood), and only after water or extraction is in use. FFP1/FFP2 and comfort/nuisance masks do not give adequate protection against respirable crystalline silica.

Do I really need health surveillance if I only cut occasionally?

It depends on whether exposure is "significant" after controls. Brief, well-controlled, occasional cutting may not trigger it, but regular cutting/grinding/chasing of masonry usually does. Do a COSHH assessment; if there is residual significant exposure, surveillance is required. When in doubt, get occupational-health advice.

Can I just wear a good mask and skip the water or extraction?

No — that inverts the COSHH hierarchy and is non-compliant. Engineering controls (water/LEV) must come first; RPE only mops up the residual risk. Relying on RPE alone is one of the most commonly enforced silica failings.

Is quartz/engineered stone worktop work especially dangerous?

Yes. Engineered/quartz worktops can be very high in crystalline silica, and dry fabrication has caused severe accelerated silicosis internationally. Use water-fed tools, fixed LEV, FFP3/powered RPE, and rigorous housekeeping, and consider health surveillance as standard.

How often must on-tool/LEV extraction be tested?

LEV (including on-tool extraction systems) requires a thorough examination and test at least every 14 months under COSHH Regulation 9, plus regular user checks and filter maintenance.

Regulations & Standards

• Control of Substances Hazardous to Health Regulations 2002 (COSHH) — duty to assess, prevent or adequately control exposure; hierarchy of control; health surveillance (Reg 11); LEV testing (Reg 9); monitoring (Reg 10).

• Health and Safety at Work etc. Act 1974 — overarching duty to protect employees and others.

• Construction (Design and Management) Regulations 2015 (CDM) — design out and plan for silica/dust risk; principal contractor control on site.

• HSE EH40/2005 Workplace Exposure Limits — RCS WEL 0.1 mg/m³ 8-hr TWA.

• HSG258 — Controlling airborne contaminants at work (LEV guidance) — design, use and testing of extraction.

• HSE Construction Dust guidance (CIS36 and construction dust pages) — practical control of silica, wood and general construction dust.

• Personal Protective Equipment at Work Regulations / RPE fit testing (HSE OC 282/28, INDG479) — face fit testing requirements.

• HSE — Construction dust (silica) guidance — primary UK regulator guidance

• HSE EH40/2005 Workplace Exposure Limits — RCS WEL 0.1 mg/m³ 8-hr TWA

• HSE — COSHH and respirable crystalline silica — control duties and hierarchy

• HSE HSG258 — Controlling airborne contaminants at work — LEV design and testing

• HSE INDG479 — Guidance on RPE fit testing — face fit testing for tight-fitting RPE

• dust control — general construction dust controls and on-tool extraction

• control of substances hazardous coshh — the COSHH framework these duties sit under

• ppe selection guide — choosing and face-fitting RPE correctly

• vibration havs — the companion power-tool health risk on the same tasks