COSHH for Construction Sites: A Practical Guide

Why Construction Has Some of the Highest COSHH Risks

Construction workers are exposed to more hazardous substances than almost any other sector. The HSE's annual workplace health statistics consistently rank construction among the highest industries for occupational lung disease, skin disease, and cancer linked to substance exposure.

The reason is straightforward: construction work generates hazardous substances at almost every stage. Cutting concrete produces respirable crystallite silica dust. Mixing cement exposes skin to hexavalent chromium. Painting, gluing, waterproofing, and cleaning all involve chemical products. Welding generates metal fume. Joinery creates wood dust. Even demolition work can release lead dust or other legacy contaminants.

Under the Control of Substances Hazardous to Health Regulations 2002, every employer on a construction site must assess these risks and put controls in place. That obligation does not disappear because you are a subcontractor, because the job only lasts two days, or because "we've always done it this way."

If you are new to COSHH entirely, our plain-English guide to what COSHH covers is a good starting point before reading the construction-specific detail below.

The Most Common Hazardous Substances on Construction Sites

Silica Dust (Respirable Crystalline Silica)

Generated by cutting, drilling, grinding, or demolishing concrete, brick, stone, morite, and sandstone. Silica dust is the single biggest occupational health risk in UK construction. Long-term exposure causes silicosis (irreversible lung scarring), chronic obstructive pulmonary disease (COPD), and lung cancer.

The Workplace Exposure Limit (WEL) for respirable crystalline silica is 0.1 mg/m³ over an 8-hour time-weighted average — a very low threshold that is easily exceeded by uncontrolled cutting or grinding.

Key controls:

• Water suppression on all cutting and drilling tools (most modern disc cutters and core drills have built-in water feeds)
• On-tool dust extraction where water is not practical
• RPE (minimum FFP3 disposable mask or powered respirator for prolonged work) as a backup, never as the sole control
• Segregate cutting areas from other workers where possible
• HSE's guidance note INDG463 covers the construction-specific requirements

Cement and Wet Concrete

Portland cement contains hexavalent chromium (Cr(VI)), a skin sensitiser that causes allergic contact dermatitis. Wet cement is also highly alkaline (pH 12-13), causing chemical burns on prolonged skin contact. Cement dermatitis is one of the most common occupational skin diseases in construction — and once a worker becomes sensitised, they cannot handle cement again without a reaction.

Key controls:

• Waterproof gloves for all wet cement handling (not fabric gloves, which absorb moisture and hold cement against the skin)
• Long sleeves and trousers to prevent skin contact
• Barrier cream is not a substitute for gloves — it provides some additional protection but cannot be relied upon alone
• Wash exposed skin promptly if contact occurs
• Health surveillance: regular skin checks for anyone handling cement regularly

Solvents and Solvent-Based Products

Construction sites use solvents in paints, varnishes, adhesives, sealants, cleaning agents, and bituminous products. Common solvents include white spirit, xylene, toluene, acetone, and methyl ethyl ketone (MEK). Exposure routes are primarily inhalation of vapour and skin absorption.

Short-term effects include headaches, dizziness, and nausea. Long-term repeated exposure to certain solvents can damage the liver, kidneys, and nervous system.

Key controls:

• Substitute with water-based alternatives wherever possible (water-based paints and adhesives have improved significantly and are now suitable for most construction applications)
• Ensure adequate ventilation — open windows and doors when working indoors, use forced ventilation in enclosed spaces
• RPE when ventilation alone is insufficient (organic vapour cartridge respirators)
• Nitrile gloves — latex does not provide adequate protection against most solvents
• Never use solvents in confined spaces without a specific confined space risk assessment and controls

Welding Fume

All welding processes generate metal fume — a mixture of fine metallic particles and gases. Since 2019, the HSE has reclassified all welding fume as a carcinogen (previously, only stainless steel welding fume had this classification). This means any welding on a construction site, including mild steel MIG and stick welding, requires effective fume control.

Key controls:

• Local exhaust ventilation (LEV) — on-torch extraction or mobile extraction units positioned close to the welding arc
• General ventilation as a supplement, not a replacement for LEV
• RPE (minimum FFP3 or powered air-purifying respirator) when LEV cannot adequately control exposure
• The "just open the doors" approach is explicitly not acceptable — the HSE has issued multiple enforcement notices on construction sites using this as their only control

Wood Dust

Generated by cutting, sanding, routing, and planing timber. Hardwood dust is classified as a carcinogen (causes nasal cancer). Softwood dust is a respiratory sensitiser that can cause occupational asthma. The WEL for all wood dust is 3 mg/m³ (inhalable dust fraction), reduced from 5 mg/m³.

Key controls:

• On-tool dust extraction connected to a suitable vacuum (M-class minimum for softwood, H-class for hardwood)
• Cut outdoors where possible to reduce concentration
• RPE as a backup where dust extraction alone is insufficient
• Health surveillance: lung function testing for workers regularly exposed to wood dust

Other Substances to Watch

• Isocyanates — found in spray-applied insulation foam, two-pack paints, and some flooring adhesives. Potent respiratory sensitisers; can cause occupational asthma from very low exposures
• Epoxy resins — used in structural adhesives, flooring systems, and coatings. Skin sensitisers causing allergic contact dermatitis
• Lead — in old paintwork during refurbishment and demolition. Has its own regulations (Control of Lead at Work Regulations 2002) but often overlaps with COSHH duties
• Man-made mineral fibres — loft insulation, pipe lagging, and acoustic insulation. Skin and respiratory irritant

The Subcontractor Challenge

Construction sites are rarely single-employer workplaces. A typical site might have a principal contractor, several subcontractors, self-employed trades, and agency labour — all working alongside each other and potentially creating exposures for workers who are not their own employees.

This creates a specific COSHH challenge: who is responsible for what?

Under the COSHH Regulations 2002, each employer is responsible for their own employees' exposure. But under the Construction (Design and Management) Regulations 2015 (CDM), the principal contractor has a duty to coordinate health and safety across the site, and that includes managing substance exposures that affect multiple trades.

Practical Steps for Principal Contractors

1. Require COSHH assessments as part of subcontractor vetting. Before a subcontractor starts work, ask to see their assessments for every substance they will bring to site or generate during their work. If they cannot produce them, they are not ready to start.
2. Maintain a site substance register. Keep a central record of every hazardous substance in use across the site, who brought it, and where it is being used. This is especially critical for coordinating incompatible substances (e.g., solvent use near hot works).
3. Coordinate controls for shared exposures. Silica dust from one trade's cutting work can expose workers from another trade 10 metres away. Plan work sequences to separate dusty operations from other activities, or enforce exclusion zones.
4. Include COSHH in site induction. Every worker arriving on site should know the key substance hazards, where SDSs are kept, and what to do if they are exposed.

Practical Steps for Subcontractors

1. Bring your COSHH assessments to site. They should be accessible — in your site folder, van, or on a phone — not filed in the office 30 miles away.
2. Share your SDS with the principal contractor. If you are bringing chemicals onto site, the PC needs to know what they are.
3. Assess the site conditions, not just the substance. Your COSHH assessment for a solvent-based adhesive in a well-ventilated warehouse does not cover using the same adhesive in a confined corridor with no windows. Adapt your assessment to the actual conditions on each site.

How to Write a COSHH Assessment for Construction Work

The process follows the same 8 steps as any COSHH assessment — our full step-by-step guide covers the method. But construction work has some specific considerations:

Assess by task, not just by product. A task-based assessment such as "Cutting concrete blocks using a petrol disc cutter" is more useful on a construction site than a product-based assessment for "concrete." It captures the actual exposure scenario, including how long the task takes, how often it happens, and what controls are practical.

Account for changing conditions. Unlike a factory, construction environments change week to week. An assessment written for outdoor groundworks may not cover the same substances being used inside the building once the roof goes on. Review and adapt as the project progresses.

Be realistic about PPE. RPE face-fit testing is mandatory for tight-fitting respirators (FFP3 masks). If your workers have not been face-fit tested, those masks are not a valid control measure. Arrange testing through an occupational health provider or trained in-house tester.

For worked examples that show exactly what to write in each field, see our COSHH risk assessment examples.

Health Surveillance on Construction Sites

Many construction substance exposures trigger a legal requirement for health surveillance under COSHH Regulation 11:

• Silica dust exposure — lung function testing (spirometry)
• Wood dust exposure — lung function testing
• Cement handling — skin checks for dermatitis
• Isocyanate exposure — lung function testing
• Solvent exposure — liver and kidney function monitoring where exposure is significant

Health surveillance must be carried out by a qualified occupational health professional. For construction, the HSE recommends baseline testing before exposure begins and then regular follow-up (typically annually). The results must be kept in individual health records for at least 40 years.

Getting Construction COSHH Right

A practical approach for a construction business:

1. List your core activities and the substances each one generates or uses. Most construction firms can identify their top 5-10 substance groups quickly.
2. Write task-based assessments for each one. Start with the highest-risk activities: silica-generating cutting, welding, solvent use in enclosed spaces.
3. Collect current SDS for every product you buy. Chase suppliers who have not provided them.
4. Train your workforce. Every operative should know the key hazards for the substances they work with and the controls they must follow. Toolbox talks are an effective format — 10 minutes before work starts, documented with a sign-off sheet.
5. Review when conditions change. A new site, a new product, a new task — each one is a trigger to check whether your existing assessment still applies.

Managing COSHH across multiple sites and subcontractors with paper folders and Word documents gets messy fast. COSHHmate is being built for exactly this kind of multi-site complexity — a central substance register across all your projects, a guided assessment builder for each task, and automatic review reminders so nothing slips between jobs.

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