Updated 5 March 2026
Comprehensive guide to the Control of Substances Hazardous to Health Regulations 2002 for UK construction. Covers assessments, exposure limits, PPE, and health surveillance.
The Control of Substances Hazardous to Health Regulations 2002 (COSHH) require employers to prevent or adequately control exposure to hazardous substances in the workplace. In construction, COSHH is particularly relevant because workers are routinely exposed to dust (including silica), cement, solvents, paints, adhesives, diesel exhaust fumes, asbestos (in refurbishment and demolition), timber dust, welding fumes, and numerous other hazardous substances.
Under COSHH, a hazardous substance includes any substance that is: listed as dangerous in the approved supply list, has a workplace exposure limit (WEL), is biological agent, is dust of any kind at concentrations above the WEL, or creates a risk to health because of its chemical or physical properties. In construction, the most commonly encountered hazardous substances are:
A COSHH assessment must be carried out for every hazardous substance used or generated on site. The assessment must identify: the hazardous substance, who is exposed and how, the duration and level of exposure, the existing control measures, the workplace exposure limit (if one exists), and the additional controls required. The assessment must be reviewed regularly and whenever work practices or substances change.
COSHH requires controls to be applied in a specific hierarchy:
1. Elimination: Can you avoid using the substance entirely? Use a non-hazardous alternative.
2. Substitution: Can you use a less hazardous substance? Water-based paint instead of solvent-based.
3. Engineering controls: Enclose the process, use local exhaust ventilation, use wet cutting methods to suppress dust.
4. Administrative controls: Reduce exposure time, rotate workers, restrict access to affected areas.
5. PPE: Respiratory protective equipment (RPE), gloves, goggles. PPE is the last resort, not the first.
Key WELs for construction substances: respirable crystalline silica (RCS). 0.1 mg/m3 (8-hour TWA); inhalable dust. 10 mg/m3; respirable dust. 4 mg/m3; hardwood dust. 3 mg/m3; softwood dust. 5 mg/m3. These limits are legal maximums, not safe levels. exposure should always be reduced as far below the WEL as reasonably practicable.
COSHH Regulation 11 requires health surveillance where employees are exposed to substances linked to specific diseases or adverse health effects. In construction, this most commonly applies to: workers exposed to silica dust (lung function tests), workers exposed to asbestos (medical examination), workers handling cement (skin checks for dermatitis), workers exposed to noise (audiometry. under Noise Regulations, but often coordinated with COSHH), and workers using vibrating equipment (HAVS checks. under Vibration Regulations).
The most frequent COSHH enforcement actions relate to: no COSHH assessment for silica-generating activities (cutting, grinding), dry sweeping of dust instead of wet methods or vacuum, incorrect or missing RPE for dusty activities, no face-fit testing for RPE users, safety data sheets not available on site, and failure to provide skin protection for cement handling. Site Manager AI can generate COSHH assessments for common construction activities, referencing current WELs and recommending appropriate controls.
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