COSHH Awareness Overview Toolbox Talk (UK Construction)

COSHH affects everyday construction activities involving dust, fumes, liquids, vapours, gases and biological agents. It belongs among essential toolbox talk topics for UK construction because harmful exposure can occur during routine work, even when no container displays an obvious hazard symbol.

This guide explains how substances enter the body, why safety data sheets are only part of the assessment, where controls fail and what supervisors should check before work begins or conditions change.

What is COSHH in construction?

COSHH stands for the Control of Substances Hazardous to Health. It covers the assessment and control of health risks from substances used, handled, stored or created by work. These may include chemicals, products containing chemicals, dusts, fumes, mists, vapours, gases and harmful micro-organisms.

A COSHH assessment considers the substance in the context of the actual task. It must account for its form, quantity, duration of use, location, people exposed and route into the body. Exposure may occur through breathing contaminated air, contact with or absorption through the skin, swallowing contamination transferred from hands or entry through damaged skin. Lead, asbestos and radioactive substances are subject to separate specific legislation.

Why it matters on UK construction sites

Depending on the substance and exposure, health effects may include irritation, chemical burns, dermatitis, breathing difficulties, asthma, poisoning, lung disease or cancer. Some effects are immediate, while others develop after repeated exposure without an obvious warning. Uncontrolled substances can also contaminate tools, welfare areas, clothing, vehicles and completed work, spreading exposure beyond the original task.

Who is exposed and how

Trades using the product or creating the contaminant face the most direct exposure, but they are not the only people at risk. Nearby workers may breathe drifting dust, fumes or vapours. Labourers, cleaners and maintenance teams may disturb residues or contaminated filters. Storekeepers, delivery drivers, supervisors, visitors and members of the public may also be affected by leaks, poor storage or substances moving beyond the controlled area.

Typical site tasks where this comes up

COSHH applies to supplied products and contaminants created by construction processes.

• Mixing or applying cement, mortar, grout, resin, sealant, adhesive and waterproofing products.
• Cutting, chasing, drilling, grinding or sanding masonry, concrete, timber and board materials.
• Painting, spraying, cleaning, degreasing or using solvents and surface treatments.
• Welding, thermal cutting and other activities that generate fume, smoke or gases.
• Working with sewage, contaminated land, stagnant water, bird fouling or other biological contamination.

Common failure modes

Weak arrangements often focus on paperwork while missing how exposure occurs during the task.

• The register lists purchased chemicals but excludes dust, fume, vapour or biological agents created by the work.
• A safety data sheet is filed as the assessment without considering the method, location, quantity or duration.
• Products are decanted into unlabelled containers or mixed without checking incompatibilities and supplier instructions.
• Extraction, water suppression or enclosure is available but incorrectly positioned, blocked, damaged or not used.
• Gloves or masks are treated as the first control without confirming suitability, compatibility, fit or limitations.
• Nearby trades, cleaners and maintenance workers are omitted from the assessment and briefing.
• Changes to the product, process, work area or programme occur without reviewing the controls or emergency arrangements.

Pre-start checks

These checks are a starting point only. They do not replace the project's risk assessment, method statement or task-specific controls.

• ☐ Substance: Identify supplied products and contaminants that the process may generate.
• ☐ Assessment: Confirm it matches the task, quantity, duration, location and people exposed.
• ☐ Information: Check current labels, safety data sheets and relevant task guidance are available.
• ☐ Controls: Verify suppression, extraction, enclosure and other specified controls are ready and effective.
• ☐ Work area: Confirm ventilation, segregation, storage, access and waste arrangements are suitable.
• ☐ People: Brief everyone affected and check required PPE, RPE and hygiene facilities.
• ☐ Emergency: Confirm spill, first-aid, decontamination and reporting arrangements.

How incidents happen and how to prevent them

Exposure often starts when a task is treated as routine. The product may be familiar, but a change in application, ventilation or duration alters the risk. The contaminant then escapes into the work area because controls are absent, poorly positioned or not maintained. Workers continue because there may be no immediate smell, irritation or visible sign that exposure is occurring.

Prevention begins by eliminating the substance or process where practicable, or choosing a safer product, form or method. Where exposure cannot be prevented, control it at source through enclosure, suitable extraction, suppression or closed handling. Restrict access, maintain good hygiene, verify that controls work and provide suitable PPE or RPE for the remaining risk.

⚠️ Hypothetical site example: A worker begins dry-cutting concrete blocks inside a partly enclosed room. The delivered blocks do not carry a chemical label, so the task is assumed to present no COSHH risk. Cutting creates airborne dust, nearby trades remain inside and no extraction is fitted. Reassessing the process-generated dust, changing the cutting method, controlling it at source and isolating the area would break this chain.

When risk increases

Review the assessment when the substance, task, environment or people affected change.

• A new product, supplier, formulation or substitute is introduced.
• Brushing changes to spraying, hand tools change to powered cutting or quantities increase.
• Work moves indoors, underground or into another poorly ventilated location.
• Extraction, suppression, containment or washing facilities become unavailable or ineffective.
• Other trades enter the area or residues spread through footwear, clothing, tools or ventilation.
• Workers report symptoms, a spill occurs or monitoring indicates that controls may not be effective.

UK regulations and compliance

In Great Britain, The Control of Substances Hazardous to Health Regulations 2002 require employers to assess health risks from hazardous substances before work liable to expose employees begins. Exposure must be prevented where reasonably practicable or adequately controlled where prevention is not reasonably practicable.

The HSE Guidance on How to Carry Out a COSHH Risk Assessment explains that assessments must include contaminants created by processes, such as wood dust, silica dust and welding fume. They should consider how exposure occurs, how often and for how long, who else may be affected and whether existing controls are sufficient.

The HSE Guidance on Control Measures for Hazardous Substances prioritises preventing or adequately controlling exposure through suitable equipment, procedures, supervision, training and worker behaviour. Controls must be used correctly, maintained and checked so they continue to work.

A supplier's HSE Chemical Safety Data Sheet Guidance provides useful information about hazards, handling, storage and emergencies. HSE makes clear that a safety data sheet is not itself a risk assessment. Its information must be applied to the actual site task and exposure conditions.

Northern Ireland has parallel duties under The Control of Substances Hazardous to Health Regulations (Northern Ireland) 2003. These include requirements covering assessment, prevention or control, maintenance of controls, monitoring, health surveillance in specified circumstances, information, training and emergency arrangements.

Practical controls that make the difference

Effective control starts with the task and follows the contaminant from its source to every person who could be exposed.

• Remove the hazard: Avoid the substance or process where practicable, such as ordering materials cut to size or using pre-mixed products.
• Choose a safer option: Consider a less hazardous product, lower-dust form or application method that produces less mist or vapour.
• Control it at source: Use suitable enclosure, on-tool extraction, local exhaust ventilation, suppression or closed transfer systems.
• Separate people: Restrict access, plan the sequence and prevent contamination spreading into adjacent work or welfare areas.
• Store and clean safely: Keep containers labelled, separate incompatible materials and use the planned spill, waste and dust-free cleaning methods.
• Check effectiveness: Inspect, maintain and test control measures as required, then review symptoms, monitoring results, defects and worker feedback.
• Manage remaining exposure: Provide suitable PPE, RPE, hygiene and health surveillance where the assessment identifies they are required.

FAQs

Is a safety data sheet the same as a COSHH assessment?
No. A safety data sheet describes a supplied product, but the COSHH assessment must apply that information to the actual task, exposure routes, people and controls.

Does COSHH apply only to products with hazard symbols?
No. It can also cover substances created by work, including dust, fume, vapour, gas and harmful biological agents, even where no labelled container is involved.

When should a COSHH assessment be reviewed?
Review it regularly and whenever the product, process, quantity, location, workforce or control measures change, or evidence suggests the existing controls may no longer be effective.

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