Silica Dust: What COSHH Requires When Cutting Stone

Silica dust is one of the most dangerous substances regulated under COSHH. It's invisible, odourless, and produced by ordinary jobs like cutting stone or sanding concrete. It also carries one of the lowest workplace exposure limits of any substance in COSHH.

In June 2026, HSE issued Prohibition Notices to four companies over dry-cutting practices on engineered stone that generated dangerous dust levels, its first use of this enforcement tool in a campaign specifically targeting this material. The underlying hazard and the legal duties around it existed long before that case and will remain the same regardless of what happens next with it.

Here's what actually matters if your business cuts, grinds, drills, or otherwise disturbs silica-containing material.

Who Does This Actually Affect?

Silica dust is a risk wherever stone, concrete, brick, mortar or engineered worktop material gets cut, ground, drilled or polished. In practice that covers a wide range of trades: kitchen and bathroom fitters installing worktops, construction workers cutting paving or breaking out concrete, stonemasons, demolition crews, and anyone chasing walls for cabling or pipework.

Many of these tasks are short, routine, and don't look like the kind of work that needs a formal hazard assessment, which is exactly why silica exposure is so often under-managed. The dust fine enough to do real harm, respirable crystalline silica (RCS), is too small to see under normal lighting, so a five-minute dry cut into a worktop offcut can generate dust levels far above the safe limit without anyone in the room realising it's happening.

What Is Silica Dust, and Why Is It So Dangerous?

Silica is a natural substance found in sandstone, granite, concrete, brick, mortar, slate, and, notably, engineered stone products used for worktops, where silica content can run far higher than in natural stone. Granite typically contains 15-30% crystalline silica by composition, though the figure varies by quarry source and the specific stone in question. Cutting, grinding, drilling, or polishing these materials releases dust, and the fraction of that dust small enough to penetrate deep into the lungs is the respirable crystalline silica described above.

RCS is classified as a Group 1 carcinogen by the International Agency for Research on Cancer, the same category as asbestos and tobacco smoke. Long-term exposure causes silicosis, an irreversible scarring of the lung tissue, alongside an increased risk of lung cancer and chronic obstructive pulmonary disease. None of this damage is reversible once it sets in, which is precisely why control has to happen before exposure, not after symptoms appear.

Where the SDS Comes In

Here's the part a general COSHH guide can't tell you: how much silica is actually in the specific product on your site. Silica content varies enormously by material, sandstone is almost pure quartz, while granite typically sits in the 15-30% range noted above, and engineered stone worktops can carry an even higher percentage than either. A COSHH assessment built on a general assumption ("stone contains silica") rather than the actual figure for your product can badly under- or over-estimate the real exposure risk.

This is exactly the information a Safety Data Sheet is built to provide. The SDS for a specific cement, mortar, engineered stone product, or abrasive blasting material will state its crystalline silica content, its hazard classification, and the precise H-phrases and P-statements that apply. The detail a COSHH assessment actually needs to be accurate rather than approximate. As an example, the Fine Silica Test Dust SDS on ISDSS shows exactly how silica content, hazard classification and precautionary statements are presented for a specific silica-containing product. If your business works with any silica-containing material, checking the current SDS for that exact product, not a generic guide, is the necessary first step before the assessment can be written properly.

What Is the Workplace Exposure Limit for Silica Dust?

HSE sets the workplace exposure limit (WEL) for respirable crystalline silica at 0.1 mg/m³, averaged over an 8-hour period. This is one of the lowest limits set for any substance under COSHH, reflecting how little exposure it takes to cause lasting harm. A single dry cut into engineered stone with no suppression or extraction can generate dust levels many times above this limit within minutes, not hours.

What Does a COSHH Assessment for Silica Need to Cover?

There's no minimum threshold that exempts a task from assessment. If the work could expose someone to silica dust, a COSHH risk assessment is required, covering what's being cut, how often, for how long, and what controls are already in place. The assessment should then drive the actual control measures, applied in the standard COSHH hierarchy:

• Elimination — stop using silica-containing materials where a genuine alternative exists. For some jobs this isn't practical, but where a lower-risk material does the same job, removing the hazard entirely beats controlling it.
• Substitution — switch to a lower-silica or silica-free product. Some engineered stone manufacturers now offer reduced-silica formulations specifically because of the scrutiny this hazard has attracted.
• Engineering controls — on-tool water suppression and local exhaust ventilation, both proven to cut airborne dust significantly when used properly and consistently, not just on the first cut of the day.
• Administrative controls — changing how and when the work happens, such as limiting how long any one worker spends on dust-generating tasks in a shift, to reduce total exposure time.
• Respiratory protective equipment (RPE) — face-fit tested masks or powered respirators, used as the last line of defence, not the first. RPE that doesn't fit properly, or isn't worn correctly for the whole task, offers far less protection than the rating on the box suggests.

Why Dry-Cutting Engineered Stone Is a Particular Risk

Engineered stone can contain a much higher percentage of crystalline silica than many natural stones, and cutting it dry, without water suppression or extraction, produces visibly heavy dust clouds that carry RCS concentrations far above the WEL. This is the specific practice targeted in HSE's engineered stone enforcement campaign, and it's worth being direct about why: dry-cutting looks like ordinary fabrication work, but it can expose a worker to a lifetime's worth of harmful dust in a single shift if no controls are in place.

What Happens If HSE Finds Uncontrolled Silica Exposure?

HSE inspectors have two main enforcement tools, and the difference between them matters. An Improvement Notice identifies a breach and gives a deadline, usually a minimum of 21 days, to fix it, while the activity can continue in the meantime. A Prohibition Notice is more serious: it's issued where an inspector believes the activity involves a risk of serious personal injury, and it requires the work to stop immediately, with no minimum notice period and no automatic suspension if the recipient appeals.

This is the category of notice HSE used in the engineered stone case referenced earlier: the dry-cutting practices found on inspection were judged serious enough to warrant stopping the work on the spot, not giving a window to fix it first. Beyond the immediate notice, both Improvement and Prohibition Notices are published on HSE's public enforcement register for at least several years, which can affect insurance renewal, client due diligence, and a business's standing in any future inspection or tender process.

What Health Surveillance Is Required?

Under COSHH Regulation 11, health surveillance is required where there's an identifiable disease linked to the substance, a reasonable likelihood it could occur under the actual conditions of work, and valid techniques exist to detect it early. Silica meets all three: silicosis and related lung damage are well documented, the risk is real wherever uncontrolled exposure happens, and lung function testing can catch early changes well before symptoms become noticeable to the worker themselves.

HSE's own guidance on health surveillance for those exposed to respirable crystalline silica (G404) sets out what this should actually involve: a baseline health questionnaire, lung function testing (spirometry), and periodic chest examination at intervals an occupational health professional can advise on. This isn't a box-ticking exercise. The results need to be interpreted by a qualified professional and fed back into the COSHH assessment itself, since a pattern of declining lung function across several workers on the same task is a clear signal that the existing controls aren't working and need to be reviewed, not just documented.

Health surveillance records for silica exposure must be kept for a minimum of 40 years, reflecting how long it can take for silicosis and related conditions to become apparent after exposure, a retention period set out in the same HSE guidance referenced above. This is a meaningfully longer retention period than most routine workplace records, and it's a duty that sits with the employer, not something that lapses if a worker changes job or the business changes hands.

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