Silica dust from cutting concrete and block on site
A cut off saw on a concrete block with no water produces silica dust hundreds of times over the exposure limit. This example covers a groundworker cutting blocks and paving slabs outdoors with a petrol saw. Draft, not yet reviewed.
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Why these controls
Water suppression is the primary control. HSE's expectation is that no cutting of concrete, block or stone is done dry. The assessment records the water feed on the saw and what happens if it fails: stop work.
RPE is still required with water suppression for this task because the dust levels are so high. An FFP3 disposable or a powered hood with a P3 filter, face fit tested for tight fitting masks.
Regular exposure to silica requires health surveillance, including a chest X ray programme through an occupational health provider. The assessment names the provider and the interval.
This document is a starting point. The employer must check it against the actual workplace, the product safety data sheet and current HSE guidance before relying on it. It is not an HSE approved document.
COSHH assessment
Control of Substances Hazardous to Health Regulations 2002, regulation 6
| Company or site | Hartwell Groundworks Ltd |
|---|---|
| Location | External works area on a housing site |
| Assessor | Mark Ellison, Site Manager |
| Reviewed by | Mark Ellison, Site Manager |
| Approved by | — |
1. Substance
| Name | Respirable crystalline silica (silica dust, RCS, concrete dust) |
|---|---|
| CAS number | 14808-60-7 |
| Supplier | — |
| Quantity held on site | — |
| Physical form | dust |
| Safety data sheet | Not attached. Obtain the current sheet from the supplier and keep it with this assessment. |
| Signal word | None |
| Pictograms | No pictograms |
2. Hazards
Listed as a carcinogen in EH40 Table 1. HSE expects water suppression or on-tool extraction plus RPE (at least FFP3) for cutting and grinding. Health surveillance is required for regular exposure.
This substance is a carcinogen or mutagen. Under COSHH regulation 7(7) exposure must be reduced as low as is reasonably practicable, not just kept below any workplace exposure limit. Health surveillance and exposure records are expected.
| Routes of exposure | inhalation |
|---|---|
| Workplace exposure limit | 8 hour TWA: 0.1 mg/m³, Respirable fraction. The Carc notation applies where the silica is generated by a work process.. Carcinogen notation (Carc) (EH40/2005) |
3. How the substance is used
| Task | Cutting concrete blocks and paving slabs with a petrol cut off saw |
|---|---|
| Who is exposed | One groundworker cutting. Labourers and other trades within 10 m |
| At particular risk | None identified |
| Frequency | Daily |
| Quantity used | Up to 50 cuts per day |
| Duration | 1 to 2 hours per day |
| Ventilation | Outdoors |
| Spray, heat or mist | No |
| Storage | Not applicable |
| Store away from | — |
4. Risk rating
| Before controls | High, 25 out of 25 (likelihood 5 × severity 5) |
|---|---|
| With controls in place | Medium, 10 out of 25 (likelihood 2 × severity 5) |
5. Control measures in place
Substitution
- We use a low dust or ready diluted form. Paste, pellet, gel, dust free powder or ready to use product instead of loose powder or concentrate, so less gets into the air.
Engineering controls
- Water suppression or on-tool extraction is used for cutting and grinding. Water fed tools, or tools connected to an M or H class vacuum, so dust is captured before it reaches the air.
Working practices
- Staff are trained on this assessment and the safe method. Everyone who uses it has been told the hazards, the safe way to use it, the controls and what to do if something goes wrong. Training is recorded. Required by COSHH regulation 12.
- The safety data sheet is available to staff. The current data sheet is kept where staff and first aiders can find it, and is checked when the product or supplier changes.
- It is stored safely. Original labelled containers, closed, upright, in a cool ventilated place away from incompatible substances, food and public access.
- Only trained staff use it, for as short a time as possible. Use is limited to the people who need to do the task, exposure time is kept short and tasks are rotated where practical.
- We clean up with a vacuum or wet methods, never dry sweeping. An M or H class vacuum or wet cleaning is used. Dry sweeping and compressed air are not used because they put settled dust back into the air.
- Health surveillance is in place. Skin checks, or a breathing questionnaire and lung function tests through an occupational health provider, as COSHH regulation 11 requires for this hazard.
- Exposure is monitored. Air monitoring has been done, or is scheduled, to check exposure stays below the workplace exposure limit (COSHH regulation 10).
Personal protective equipment
- Staff wear eye protection. Goggles to EN 166 where there is a risk of splashing. Safety glasses are not relied on for corrosive liquids.
- Staff wear respiratory protection. RPE with the filter type in the data sheet. Tight fitting masks have been face fit tested. Follows HSE guidance HSG53.
6. Decisions
| Substitution considered | — |
|---|---|
| Exposure adequately controlled | — |
| Health surveillance | — |
| Exposure monitoring | — |
7. Further action required
None identified at this revision.
8. First aid, spillage and disposal
Inhaled: fresh air. Persistent cough or breathlessness needs medical assessment. In an emergency call 999. For advice call NHS 111.
| Spillage | Follow section 6 of the safety data sheet. |
|---|---|
| Disposal | Follow section 13 of the safety data sheet. Waste leaves site as hazardous waste through a licensed carrier. |
9. Notes
Blocks ordered to size where possible to reduce cutting. Saw with water feed only; no water, no cutting. FFP3 fit tested. Others kept upwind and 10 m away. Health surveillance through the site occupational health provider.
Hazard data from the ECHA classification and labelling inventory and HSE EH40/2005. Check the supplier safety data sheet for the exact product and concentration you use. Review by the next review date, and sooner if the product or supplier changes, the task or the people doing it change, there is a spill or incident, anyone reports symptoms, or new information arrives from the supplier or HSE. This assessment is a starting point; the employer must review it against the actual workplace before relying on it.
