COSHH Assessment for Construction: Substances You're Probably Missing
Most tradespeople know they need risk assessments. Fewer realise how many of the substances they handle every single day require a separate COSHH assessment — and even fewer actually do them properly. If you've ever cut a concrete block, mixed cement, or opened a tin of solvent-based paint, you've been exposed to a substance that's covered by COSHH. Whether you've assessed it is another question.
What COSHH Actually Is
COSHH stands for the Control of Substances Hazardous to Health Regulations 2002. It's a specific set of regulations (separate from the general risk assessment duties under MHSWR 1999) that requires employers and the self-employed to assess and control exposure to hazardous substances at work.
"Hazardous substance" doesn't just mean chemicals in labelled containers. It covers dusts, fumes, vapours, mists, gases, and biological agents. If a substance can damage your health through inhalation, skin contact, ingestion, or absorption, COSHH applies.
The penalty for getting this wrong isn't theoretical. HSE inspectors routinely check COSHH assessments on construction site visits, and fines for health and safety breaches keep climbing. More importantly, the substances covered by COSHH are responsible for thousands of occupational disease cases every year in UK construction — occupational lung disease and skin disease remain two of the biggest health problems in the industry.
If you need a refresher on how COSHH assessments fit into your wider project documentation, our risk assessment template guide for construction covers the broader picture.
Substances Most Tradespeople Miss
The substances that cause the most harm on construction sites aren't exotic chemicals. They're materials tradespeople work with so routinely they stop thinking about them.
Silica Dust (Respirable Crystalline Silica)
Cutting, grinding, drilling, or chasing concrete, brick, block, sandstone, or engineered stone releases respirable crystalline silica (RCS) dust. Silica dust causes silicosis — irreversible lung scarring — and is a Group 1 carcinogen. The WEL for RCS is just 0.1 mg/m3 (8-hour TWA) per HSE's EH40. That's extremely low. A single uncontrolled cut on a concrete slab can exceed it within minutes. No water suppression or extraction? You're almost certainly overexposing yourself and everyone nearby.
Wood Dust
Hardwood dust is classified as a carcinogen (nasal cancer). The WEL is 3 mg/m3 (8-hour TWA); softwood dust is 5 mg/m3. Machining, sanding, or routing timber without extraction means you need a COSHH assessment and you're probably overexposed. MDF is particularly bad — it releases wood dust and formaldehyde resin, and the fine particles stay airborne far longer than solid timber dust.
Cement and Wet Concrete
Ordinary Portland cement is alkaline enough to cause chemical burns on prolonged skin contact. But the hidden hazard is hexavalent chromium (chromium VI), a sensitiser that causes allergic contact dermatitis. Once you're sensitised, you're sensitised for life. Wet concrete, grout, screed, and render all carry the same risk. If your hands touch cement products without suitable gloves (nitrile, not latex), sort that out today.
Solvent-Based Paints, Adhesives, and Sealants
Any product containing organic solvents — toluene, xylene, white spirit, acetone, MEK — requires a COSHH assessment. These substances cause headaches, dizziness, and respiratory irritation at low concentrations, and liver and kidney damage at higher levels. Many have specific WELs listed in EH40.
The Safety Data Sheet (SDS) for each product tells you what solvents are present, at what concentration, and what controls are needed. If you don't have the SDS, you can't do a COSHH assessment.
Lead
If you work on buildings constructed before the 1960s, you will encounter lead — paint, pipes, flashing. Sanding, scraping, or burning lead paint generates lead fumes and dust. The WEL for lead is 0.15 mg/m3 (8-hour TWA), and there are additional requirements under the Control of Lead at Work Regulations 2002 including biological monitoring for workers with significant exposure. Lead exposure is cumulative and the damage builds over years.
Isocyanates
If you work with spray foam insulation, two-pack paints, or certain polyurethane adhesives, you're exposed to isocyanates. These are potent respiratory sensitisers — once sensitised, even trace amounts trigger asthma attacks. Workers using these products must have adequate RPE (typically supplied air for spray applications), health surveillance, and proper COSHH assessments.
A Note on Asbestos
Asbestos isn't covered by COSHH — it has its own regulations (the Control of Asbestos Regulations 2012). But tradespeople frequently confuse the two. Asbestos work falls into three categories: licensed work (highest risk, requires an HSE licence), notifiable non-licensed work (NNLW, must be notified to HSE), and non-licensed work (no notification but still requires controls). If you're working on any pre-2000 building, you need to know where the asbestos is before you start.
What a COSHH Assessment Must Contain
HSE's guidance document INDG136 ("Working with substances hazardous to health") sets out 8 steps for a COSHH assessment:
- Assess the risks — identify hazardous substances present and who's exposed
- Decide what precautions are needed — eliminate, substitute, or reduce exposure
- Prevent or control exposure — hierarchy of control: elimination > substitution > engineering controls > admin controls > PPE
- Ensure controls are used and maintained — LEV needs testing every 14 months, RPE needs fit-testing
- Monitor exposure — air monitoring for substances like silica, lead, isocyanates
- Health surveillance — legally required for silica, lead, isocyanates, wood dust
- Emergency procedures — spills, overexposure, first aid
- Information, training, supervision — workers must know the hazards and controls
This isn't a tick-box exercise. It needs to reflect what actually happens on your site with the specific products you use.
Where to Find Safety Data Sheets
You cannot complete a COSHH assessment without the Safety Data Sheet (SDS) for each product. SDSs follow a standardised 16-section format under REACH and contain the hazard data, exposure limits, and controls you need. Get them from manufacturer websites, supplier product pages (Travis Perkins, Jewson, etc.), or by direct request — suppliers are legally required to provide them. HSE's COSHH Essentials tool is also useful for matching hazards to controls.
You can use our COSHH substance lookup tool to find common construction substances, their hazard classifications, and the control measures that apply.
Common COSHH Mistakes on Small Sites
On larger sites, the principal contractor enforces compliance. On smaller jobs, standards slip. The most common mistakes:
- No assessment at all. "We've always used it and been fine" is not a COSHH assessment.
- Generic assessments that don't name the actual products or site conditions.
- Relying on PPE alone without considering elimination, substitution, or engineering controls.
- Missing health surveillance for silica, wood dust, isocyanates, or lead — it's a legal requirement, not optional.
- No SDS on site. The assessment is in a filing cabinet at the office and nobody on the ground knows the controls.
Quick Reference: Common Construction Substances
| Substance | Where Found | Main Hazard | Key Control Measures |
|---|---|---|---|
| Respirable crystalline silica | Cutting/grinding concrete, brick, stone | Silicosis, lung cancer (WEL: 0.1 mg/m3) | Water suppression, on-tool extraction, RPE (FFP3) |
| Hardwood dust | Machining, sanding timber and MDF | Nasal cancer, asthma (WEL: 3 mg/m3) | LEV/extraction, RPE (FFP3), good housekeeping |
| Cement / wet concrete | Mixing, laying, rendering | Dermatitis, chemical burns (chromium VI) | Nitrile gloves, barrier cream, minimise skin contact |
| Solvent-based paints & adhesives | Painting, gluing, sealing | CNS effects, liver/kidney damage, fire risk | Ventilation, low-solvent alternatives, RPE where needed |
| Lead dust/fumes | Sanding/burning old paint, lead pipework | Cumulative poisoning (WEL: 0.15 mg/m3) | Wet methods, RPE, biological monitoring, Control of Lead at Work Regs |
| Isocyanates | Spray foam, two-pack paints, PU adhesives | Occupational asthma (sensitiser) | Supplied air RPE, health surveillance, restrict access |
| Diesel exhaust emissions | Plant, generators in enclosed spaces | Lung cancer (WEL: 0.1 mg/m3 as elemental carbon) | Ventilation, electric alternatives, limit enclosed running |
All WELs referenced above are from EH40/2005 (Fourth Edition, 2020) published by HSE. Check the current edition for any updates.
Getting COSHH Right Without Burying Yourself in Paperwork
COSHH assessments aren't difficult once you understand the process. The hard part is doing them consistently for every substance on every job and making sure the people doing the work actually know what the controls are.
That's one of the things TradeRAMS is being built to handle — substance identification for your specific trade activities, with COSHH assessments generated alongside your RAMS so nothing gets missed. If that sounds useful, join the waitlist at traderams.co.uk and you'll get access as soon as it's ready.
Your lungs don't care whether the job was big or small. Assess the substances. Control the exposure. Do it every time.