The Control of Substances Hazardous to Health Regulations 2002 require an employer to assess the health risks from hazardous substances before work starts, and to prevent exposure or, where prevention is not reasonably practicable, adequately control it.
Most construction COSHH assessments cover the tins in the store: solvents, adhesives, sealants, cleaning products. Those are the easy ones, because they arrive with a safety data sheet. The substances that actually cause the greatest harm in construction are generated by the work itself, and they arrive with nothing.
The substances that get missed
Respirable crystalline silica
Produced whenever concrete, stone, brick, block, mortar, tile or sand is cut, drilled, ground, chased or swept. It causes silicosis, chronic obstructive pulmonary disease and lung cancer, and HSE identifies it as the biggest risk to construction workers after asbestos. The workplace exposure limit is 0.1 mg/m³ as an eight-hour time-weighted average — a quantity of dust far smaller than most people picture. A few minutes of dry cutting can exceed a day's limit.
Wood dust
Hardwood and softwood dust both have workplace exposure limits, and hardwood dust is a recognised cause of nasal cancer. Sanding, sawing and routing all generate it, and it is routinely absent from carpentry RAMS.
Welding fume
Following a change in the scientific evidence, HSE now treats all welding fume — including from mild steel — as a carcinogen, and requires effective engineering controls for all indoor welding, with RPE where controls cannot bring exposure below an adequate level. Outdoor welding also requires RPE where engineering controls cannot adequately control exposure. Any RAMS covering welding that relies on natural ventilation is out of date.
Cement and wet concrete
Highly alkaline and abrasive. Causes irritant and allergic contact dermatitis, and prolonged skin contact with wet concrete causes chemical burns severe enough to require grafting — most often to knees through soaked trousers. Skin protection and prompt washing are the controls, and the assessment should say so.
Exhaust emissions
Diesel engine exhaust emissions are carcinogenic. Plant, generators and vehicles running in enclosed or partially enclosed spaces — basements, tunnels, ground floors before the openings are formed — need ventilation, engine positioning, or electric alternatives.
Asbestos
Not covered by COSHH but by the Control of Asbestos Regulations 2012, and mentioned here because it is the reason refurbishment RAMS need to reference the survey. Any building constructed or refurbished before 2000 may contain ACMs. The duty is to identify before disturbing, and licensed work must be carried out by a licensed contractor.
What the assessment must do
- Identify every hazardous substance used or created by the work, including dusts, fumes, gases and biological agents.
- Establish who could be exposed, how, for how long and how often — including other trades in the area and anyone cleaning up afterwards.
- Compare likely exposure against the workplace exposure limit in EH40 where one exists.
- Decide on control measures using the hierarchy: eliminate, substitute, engineer, administer, and RPE last.
- Record the significant findings, the controls and who is responsible for them.
- Set out monitoring, health surveillance, training and emergency procedures.
- Review when anything changes, or when there is reason to think it is no longer valid.
A COSHH assessment is not a safety data sheet. The data sheet is manufacturer information about a product; the assessment is your evaluation of what happens when your people use it in your conditions. Filing the sheets and calling it a COSHH assessment is one of the most common findings on a construction site, and it belongs on the same list as the faults in twelve RAMS mistakes that fail inspection.
Controls that work
- Elimination and substitution first: order materials cut to size, buy pre-formed components, use a less hazardous product, switch to a water-based system.
- Water suppression on cutting and grinding, with an adequate flow rate rather than a token spray.
- On-tool extraction with an M or H class vacuum, checked and emptied properly — an unmaintained extractor is a control on paper only.
- Local exhaust ventilation for welding and fixed processes, subject to thorough examination and test at least every 14 months.
- Segregation and enclosure so dust does not travel to other trades, plus restricted access during the task.
- Job rotation and scheduling to limit exposure time, as an administrative control rather than a primary one.
- RPE last: the right protection factor for the exposure, face-fit tested to the individual by a competent tester, incompatible with beards for tight-fitting masks, stored clean and maintained. Face-fit records should be available on site.
- Never dry sweeping. Vacuum with the appropriate class of machine, or wet methods.
The order matters as much as the content. An assessment whose only control for silica is an FFP3 mask has skipped four levels of the hierarchy, and a reviewer will treat it exactly as they treat PPE-first controls anywhere else — see how to write control measures that actually work.
Health surveillance
Where exposure to a substance linked to an identifiable disease or health effect is likely and there are valid techniques for detecting it, COSHH requires health surveillance. In construction that commonly means skin checks for dermatitis where there is wet work or cement contact, and respiratory questionnaires or lung function testing where there is significant exposure to silica, wood dust or isocyanates. Records are kept for 40 years where exposure is to a carcinogen, mutagen or asthmagen.
How it connects to the RAMS
Every hazardous substance named in the method statement needs a COSHH assessment reference in the materials section, and every control from the assessment needs to appear in the control measures against the relevant hazard. The most common structural failure is a method statement describing an activity that obviously creates dust — chasing, coring, cutting kerbs — with a materials list containing only purchased products.
That cross-reference is mechanical, which means it is checkable: any substance in the method with no assessment reference is a finding. If you are submitting the COSHH assessment alongside the RAMS, which documents can be reviewed together covers how the pair is handled, and the cross-document check is the point of submitting them together.
This article is general guidance on UK construction documentation practice. It is not legal advice, a compliance certification or a substitute for review by your own qualified health and safety personnel, who remain responsible for deciding whether any particular document is adequate. See our disclaimer.