COSHH is sometimes treated on construction sites as a system for managing tins, bottles and products stored in a chemical cabinet. That is only part of its scope. The Control of Substances Hazardous to Health Regulations apply to substances that can damage health, including materials brought onto site and hazardous dusts, fumes, vapours, mists, gases and biological agents created or encountered during the work.
This distinction matters because some of the most serious occupational-health exposures in construction do not arrive with a product label. Silica dust is released by cutting concrete and masonry. Welding produces fume. Diesel plant creates exhaust emissions. Damp buildings, contaminated water, sewage and bird droppings can expose workers to harmful micro-organisms. A suitable COSHH assessment must therefore examine the task and exposure route, not simply the supplier's paperwork.
COSHH covers more than purchased chemicals. It can apply to any substance hazardous to health that is used, produced or encountered during construction work, unless it is governed by a separate specific regime such as asbestos, lead or radioactive-substance legislation.
What Does COSHH Mean?
COSHH stands for the Control of Substances Hazardous to Health. The regulations require employers to assess health risks arising from hazardous substances and to prevent exposure where reasonably practicable. Where prevention is not possible, exposure must be adequately controlled.
The central question is not simply whether a material is called a chemical. The practical question is whether its chemical or toxicological properties, combined with the way it is used, generated or present at the workplace, could harm health. Exposure may occur by breathing a substance in, through skin or eye contact, by swallowing it or through injection into the skin.
Which Substances Are Covered by COSHH on Construction Sites?
HSE guidance identifies chemicals, products containing chemicals, fumes, dusts, vapours, mists, nanotechnology, gases, asphyxiating gases and biological agents as forms of substances that can fall within COSHH. In construction, these categories appear across routine activities from mixing and spraying to drilling, cutting, cleaning, demolition and work in confined or contaminated environments.
| COSHH Category | Construction Examples | What the Assessment Must Consider |
|---|---|---|
| Chemicals and products containing chemicals | Adhesives, resins, sealants, cement products, coatings, solvents, cleaning agents, release oils, curing compounds, grouts and two-part paints. | Hazard classification, concentration, quantity, application method, skin and eye contact, ventilation, storage, mixing, spills and disposal. |
| Dusts | Respirable crystalline silica from concrete and masonry, wood dust, cement dust, gypsum dust and dust generated during drilling, cutting, sanding, chasing or demolition. | Material composition, dust-generation rate, task duration, enclosure, water suppression, on-tool extraction, cleaning method, nearby workers and respiratory protection. |
| Fumes and exhaust emissions | Welding and thermal-cutting fume, soldering fume, diesel engine exhaust emissions and fumes released by heated or hot-applied materials. | Source capture, local exhaust ventilation, work location, process, metal or material involved, plant operation, accumulation in enclosed spaces and exposure duration. |
| Vapours, sprays and mists | Solvent vapours, paint and coating spray, isocyanate-containing foams or coatings, cleaning aerosols and mists produced during application or mechanical processes. | How far the contaminant travels, airborne concentration, ventilation, exclusion zones, clearance time, skin exposure and whether spraying can be replaced by a lower-emission method. |
| Gases and asphyxiating gases | Carbon monoxide from combustion equipment, gases released in confined spaces, and inert gases such as nitrogen or argon used in some work processes. | Oxygen displacement, ventilation, gas detection, equipment condition, emergency arrangements, confined-space controls and the possibility of rapid exposure. |
| Biological agents | Bacteria, fungi and other harmful micro-organisms associated with sewage, contaminated soil or water, stagnant systems, mould, animal waste and bird droppings. | Likely organism, route of infection, vulnerable workers, hygiene, welfare, decontamination, sharps or splash risks, waste handling and emergency response. |
| Nanomaterials | Engineered nanomaterials incorporated into specialist coatings, additives, insulation products or advanced construction materials. | Available supplier information, particle release during cutting or sanding, uncertainty in exposure, containment, extraction and precautionary controls. |
COSHH Includes Substances Created by the Work
One of the most important construction lessons is that a substance does not need to be delivered in a labelled container to require control. A concrete slab is not normally treated as a chemical product during use, but drilling, chasing, scabbling or dry cutting can release respirable crystalline silica. Timber becomes a different occupational-health risk when sawing or sanding produces airborne wood dust. Welding transforms metal, coatings and process consumables into a fume exposure requiring control.
This is why a product register alone cannot define the COSHH scope of a project. The assessment must also examine the work sequence, materials disturbed, tools used and contaminants generated. LCM's earlier analysis of silica exposure during dry cutting of engineered stone illustrates how a familiar material can become a severe health risk once the work method releases fine respirable dust.
Are Hazard Labels Enough to Decide Whether COSHH Applies?
No. Hazard labels and safety data sheets are essential sources of information for supplied products, but they do not capture every harmful substance present on a construction site. Dust, welding fume, exhaust emissions, mould and contaminated water may have no container and no label at the point of exposure.
A safety data sheet is therefore the starting point for a product assessment, not the completed COSHH assessment. The site team must still consider how much is used, how it is applied, who may be exposed, the route and duration of exposure, existing controls, foreseeable failures, cleaning, waste and emergency arrangements. A generic manufacturer's recommendation cannot replace an assessment of the actual task and work environment.
What Substances Are Not Covered by COSHH?
HSE identifies three principal exclusions because they are governed by their own specific regulatory regimes: lead, asbestos and radioactive substances. Their exclusion from COSHH does not mean they present less risk. It means the applicable assessment, competence, control, licensing, monitoring and record requirements must be identified under the relevant legislation.
This distinction is especially important during refurbishment and demolition. Suspect asbestos-containing material must not be placed into an ordinary COSHH register as though it were simply another product. It requires asbestos-specific management. LCM's examination of asbestos risk during London retrofit and demolition work explains how concealed materials can affect intrusive surveys, soft strip, sequencing, access and site isolation.
Can the Same Substance Fall Under COSHH and Other Regulations?
Yes. A substance can create more than one type of risk. Solvents, paints, fuels, gases and combustible dusts may create health risks from inhalation or skin contact while also creating fire or explosion risks. COSHH addresses risks to health from exposure. The Dangerous Substances and Explosive Atmospheres Regulations address safety risks from fire, explosion and substances corrosive to metal.
The practical response is not to choose one framework and ignore the other. The project must assess each relevant risk. A flammable solvent may require exposure controls, suitable storage, ventilation, ignition control and emergency arrangements. A gas may create toxicity, oxygen-displacement and fire risks at the same time.
Who Must Be Considered in a Construction COSHH Assessment?
The assessment should not stop with the operative carrying out the task. Exposure can affect labourers, supervisors, adjacent trades, cleaners, maintenance workers, delivery drivers, visitors and members of the public. Dust and vapour can travel beyond the immediate workface. Contaminated gloves, tools, clothing and waste can also spread exposure after the primary task has finished.
The assessment should consider normal work, short-duration high-exposure activities, maintenance, breakdowns, spills, cleaning and foreseeable emergencies. It should also recognise people who may be particularly vulnerable because of health conditions or other individual factors, using competent occupational-health advice where required.
What Should Construction Teams Do Once a Substance Is Identified?
Identification is only the first stage. The employer must decide whether exposure can be prevented by removing the substance, changing the specification or using a safer process. Where exposure cannot be prevented, controls should follow the hierarchy and act at source wherever possible. Examples include enclosure, segregation, water suppression, local exhaust ventilation, on-tool extraction, restricted access, safe handling procedures and suitable cleaning methods.
Personal protective equipment and respiratory protective equipment may still be necessary, but they should not automatically become the first or only control. The system must also ensure that controls are used correctly, maintained and checked; workers receive information, instruction and training; and monitoring or health surveillance is introduced where the assessment shows it is required.
Common COSHH Scope Errors on Construction Sites
Only assessing products in the chemical store: this misses dusts, fumes, emissions and biological agents generated or encountered during the work.
Using the safety data sheet as the full assessment: the sheet describes the product, but the COSHH assessment must describe the real task, exposure and controls.
Copying a generic assessment between projects: quantities, work methods, ventilation, programme, workforce and adjacent activities can change the exposure significantly.
Relying on a disposable mask without source control: high-dust tasks may require water suppression, extraction, segregation and correctly selected, face-fit-tested RPE.
Forgetting cleaning and waste: dry sweeping, uncontrolled filter changes, contaminated clothing and poor waste handling can create a second exposure after the main task.
Failing to update the assessment: a new product, revised method, design change, enclosed work area or new subcontractor can make the existing controls unsuitable.
Why the Scope Matters for Compliance Evidence
A COSHH document is useful only when it connects the hazardous substance to the actual work and proves how exposure will be controlled. Principal contractors and subcontractors should be able to show that process-generated hazards have been identified, controls are present at the workface, operatives understand them and supervision is checking that they remain effective.
The enforcement lesson is wider than paperwork. LCM's review of repeated failures appearing in HSE prosecution releases found that known hazards continue to cause serious harm where they are not converted into physical controls, safe systems of work, supervision and verifiable site evidence.
The Practical Answer
COSHH covers hazardous substances used, produced or encountered during UK construction work. This includes chemical products, dusts, fumes, vapours, mists, gases, asphyxiating gases, biological agents and nanomaterials. On a construction project, the scope may therefore include everything from resin, sealant and cement products to silica dust, wood dust, welding fume, diesel exhaust, isocyanate spray, carbon monoxide, mould and contaminated water.
Lead, asbestos and radioactive substances sit outside COSHH because they have specific regulatory regimes. The most reliable approach is to assess the work activity rather than the chemical cupboard: identify what is brought onto site, what the process creates, how people may be exposed and whether the controls will work under the actual site conditions.
Sources and methodology: This guidance was prepared using the Health and Safety Executive's current information on substances hazardous to health, COSHH risk assessment, construction hazardous substances, construction dust and DSEAR. It is general construction-industry guidance and does not replace a task-specific COSHH assessment, occupational-hygiene advice, safety data, exposure monitoring or competent legal and health-and-safety advice.
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Expert Verification & Authorship: Mihai Chelmus
Founder, London Construction Magazine | Construction Testing & Investigation Specialist |
