COSHH Assessment for Silica Dust: What It Has to Cover

Pro Site Docs · Guide

Silica dust is the second biggest killer of construction workers in the UK after asbestos, and it is the hazard most likely to be missing from a small firm's paperwork. If your people cut kerbs, chase walls, grind concrete, core drill or dry-sweep, you need a COSHH assessment that deals with it specifically.

Why silica gets its own assessment

The Control of Substances Hazardous to Health Regulations 2002 (COSHH) require a suitable and sufficient assessment of the risk from any hazardous substance before work starts. Respirable crystalline silica (RCS) has a workplace exposure limit (WEL) of 0.1 mg/m³ averaged over 8 hours. HSE research shows that cutting a single kerb dry with a petrol saw can produce many times that in a few minutes.

A generic 'dust' line in a RAMS does not meet the duty. The assessment has to name the substance, the task, the people exposed and the controls that bring exposure below the limit.

The tasks that nearly always breach the limit

• Cutting kerbs, blocks, paving and roof tiles with a petrol or electric cut-off saw
• Chasing out walls for services
• Grinding, scabbling or bush-hammering concrete
• Core drilling and breaking out
• Dry sweeping any of the above
• Demolition and soft-strip in masonry buildings

If a task on your site is in that list and the assessment does not mention silica, the assessment is not suitable and sufficient.

What the assessment has to record

• The substance and its hazard — RCS, WEL 0.1 mg/m³, the health effects (silicosis, COPD, lung cancer)
• The task and how long it takes — exposure is about time as well as concentration
• Who is exposed — the operator, and anyone working downwind or in the same room
• Controls in order — eliminate (pre-cut off site, block splitter), then water suppression or on-tool extraction, then RPE as the last layer
• RPE detail — the assigned protection factor needed, face-fit testing, and that it is worn for the whole task
• Maintenance of controls — COSHH regulation 9 requires local exhaust ventilation to be thoroughly examined and tested at least every 14 months, with records kept
• Health surveillance — regulation 11 requires it where there is a reasonable likelihood of disease; for regular silica exposure HSE expects it
• Information and training — what the workers have been told, and when

Controls that actually work on site

HSE's construction dust guidance (CIS36) is blunt: water or on-tool extraction, plus RPE. Water on the blade cuts RCS dramatically but only if the flow is right and continuous. On-tool extraction needs an M-class vacuum, not a domestic one. Dry sweeping is the single easiest habit to stop — wet it down or vacuum it.

RPE on its own is not a control. A disposable FFP3 mask on an unshaven face with no fit test gives a fraction of its rated protection.

Review it, and brief it

The assessment is reviewed when the task, the material or the kit changes, and at least periodically. The controls are only real if the people doing the cutting know them — a five-minute toolbox talk on silica, signed, is the evidence.

Get the documents ready-made

Our COSHH Pack includes a ready-made silica dust assessment alongside cement, diesel, bitumen and other common site substances, or take individual COSHH templates.

General guidance only. This article explains how the rules generally work in UK construction. It is not advice for your specific site, task or project, and it is not legal advice. Your own risk assessment, method statement and arrangements must be prepared and checked by a competent person for the actual work being done.