What is the UK exposure limit for silica dust?
Updated · UK law and HSE guidance
Short answer
The UK workplace exposure limit for respirable crystalline silica is 0.1 mg/m³ as an eight-hour time-weighted average. It is a maximum, not a safe target: employers must prevent exposure where reasonably practicable or adequately control it. Use lower-dust methods, water suppression or extraction, then suitable face-fit-tested RPE where needed.
| RCS WEL | 0.1 mg/m³ |
|---|---|
| Averaging period | 8-hour time-weighted average |
| Classification | Carcinogen |
| Main control law | COSHH Regulations 2002 |
| Control principle | Prevent or adequately control exposure |
| RPE | Last/additional line; tight-fitting types require fit testing |
Where respirable silica comes from
Respirable crystalline silica can be released when stone, concrete, mortar, brick, tile and similar silica-containing materials are cut, drilled, ground or otherwise disturbed. The respirable fraction is fine enough to reach deep into the lungs. Exposure can cause serious lung disease, so visible dust is not a reliable measure and the legal limit should never be treated as a desirable working level.
- Identify material, silica content, task and duration
- Include people nearby and dust carried into other areas
- Consider cleaning and maintenance exposure
Control at source
Avoid the dusty process or use pre-cut material where possible. Choose suitable lower-energy methods and tools with effective water suppression or on-tool extraction designed for the task. Maintain extraction, use compatible dust collection and prevent dry sweeping or compressed-air cleaning. Separate the area and limit access while prioritising engineering control over exposure-time restrictions.
- Check water or extraction is working before cutting
- Use suitable dust-class extraction and safe disposal
- Monitor the work to verify controls remain effective
RPE, assessment and monitoring
Where engineering controls cannot adequately control the remaining exposure, select respiratory protective equipment with suitable protection and compatibility. Tight-fitting masks require face-fit testing for the wearer and must be clean-shaven at the seal. A competent COSHH assessment should decide whether exposure monitoring and health surveillance are required. Record maintenance, examination and test arrangements for every control. SitePaper can generate a silica COSHH assessment for competent review.
- Train wearers to check the seal each time
- Do not rely on disposable masks alone for uncontrolled cutting
- Review after process, material, control or exposure changes
Sources
- HSE: Controlling exposure to stone dust
- HSE: How to carry out a COSHH assessment
- HSE: RPE fit-testing basics
- HSE: COSHH frequently asked questions
This guide summarises UK law and HSE guidance for small businesses. It is not legal advice; check the sources and your own circumstances.