COSHH assessments are one of the most commonly neglected pieces of documentation on construction sites. It is not that people do not know they need them -- it is that the process seems complicated, so they either ignore it or produce generic assessments that are not worth the paper they are printed on. Here is a practical guide to doing COSHH assessments properly.
What COSHH Covers on Construction Sites
The Control of Substances Hazardous to Health Regulations 2002 (COSHH) apply to any substance that can harm health through inhalation, skin contact, ingestion, or injection. On construction sites, this includes a surprisingly wide range of materials that many workers handle daily without thinking about the health risks.
COSHH covers:
- Chemicals: Adhesives, sealants, solvents, paints, cleaning agents, concrete admixtures, waterproofing compounds
- Dust: Silica dust (from cutting concrete, brick, stone), wood dust, plaster dust, insulation fibres
- Fumes: Welding fumes, soldering fumes, diesel exhaust emissions
- Biological agents: Leptospirosis (Weil's disease from rat urine in waterways), tetanus, mould in refurbishment work
- Construction materials: Cement (causes cement dermatitis and burns), lime, resin systems (epoxies, polyurethanes)
COSHH does not cover lead (covered by the Control of Lead at Work Regulations 2002), asbestos (covered by the Control of Asbestos Regulations 2012), or radioactive substances. These have their own separate regulations.
Common Hazardous Substances on Construction Sites
These are the substances you will encounter most frequently:
Cement and Concrete
Wet cement is strongly alkaline (pH 12-13) and causes serious skin burns with prolonged contact. Cement dust causes eye irritation and, with repeated exposure, respiratory sensitisation. Chromium VI in cement is a major cause of occupational dermatitis. Every worker who handles wet concrete or mortar needs to understand the risks.
Silica Dust
Respirable crystalline silica (RCS) is produced when cutting, grinding, or drilling concrete, brick, sandstone, granite, and mortar. It causes silicosis (progressive, incurable lung disease), lung cancer, and chronic obstructive pulmonary disease. The current UK workplace exposure limit is 0.1 mg/m3 (8-hour TWA). This is exceeded within seconds of dry-cutting concrete without dust suppression.
Isocyanates
Found in polyurethane paints, spray foam insulation, and some adhesives. Isocyanates are one of the most common causes of occupational asthma. Once sensitised, even tiny exposures can trigger severe asthma attacks. Health surveillance is required for all workers who may be exposed.
Wood Dust
Hardwood dust is classified as a carcinogen (causes nasal cancer). Softwood dust causes asthma and respiratory irritation. The workplace exposure limit for hardwood dust is 3 mg/m3. Proper extraction at the point of cutting is essential.
Welding Fumes
Reclassified as a carcinogen by the International Agency for Research on Cancer. All welding fumes, regardless of the material being welded, must now be controlled. This means local exhaust ventilation or RPE for all welding operations, including those outdoors.
Step-by-Step COSHH Assessment Process
- Identify the hazardous substances: Walk the site. Check what products are being used. Collect the safety data sheets (SDS) for every product. Do not forget process-generated substances like silica dust from cutting and welding fumes.
- Identify who is exposed: Not just the person using the product. Consider workers nearby, passers-by, and people who might enter the area later. Think about cleaners, other trades, and visitors.
- Assess the risk: Consider the hazard level (from the SDS), the exposure route (inhalation, skin contact, ingestion), the duration and frequency of exposure, the quantity used, and any existing controls. Is the current risk acceptable?
- Determine the controls needed: Apply the hierarchy of control (see below). Document exactly what controls will be used.
- Record your findings: The assessment must be in writing if you have five or more employees. In practice, always write it down regardless of workforce size.
- Implement the controls: An assessment is worthless if the controls are not actually put in place. Ensure the right PPE is available, extraction equipment is set up, and workers are informed.
- Monitor and review: Check that controls are working. Carry out exposure monitoring where required. Arrange health surveillance for workers exposed to substances known to cause specific diseases.
Selecting Control Measures
COSHH regulation 7 requires controls to be applied in order of priority:
- Eliminate: Can you remove the hazardous substance entirely? Use a water-based product instead of a solvent-based one. Use mechanical fixings instead of adhesives.
- Substitute: Use a less hazardous substance. Low-chromate cement instead of standard cement. Pre-cut materials delivered to site instead of cutting on site.
- Enclose: Contain the substance or process. Enclosed cutting systems with dust extraction. Sealed mixing systems for two-part products.
- Local exhaust ventilation (LEV): Extract the substance at source. On-tool dust extraction for power tools. Welding fume extraction. Spray booth ventilation.
- General ventilation: Dilute airborne concentrations with fresh air. Less effective than LEV but may be appropriate for low-risk exposures in enclosed spaces.
- Safe systems of work: Procedures to reduce exposure. Wet cutting instead of dry cutting. Restricting access during spraying operations. Rotating workers to limit individual exposure time.
- PPE: Personal protective equipment is the last resort. Gloves, respirators, eye protection, overalls. RPE must be face-fit tested and maintained.
- Silica dust: Exposure monitoring where there is doubt about compliance with the WEL. Health surveillance (lung function testing) for workers regularly exposed.
- Isocyanates: Health surveillance (lung function and symptom questionnaire) for all potentially exposed workers. Baseline before first exposure, then annually.
- Wood dust: Health surveillance for workers regularly exposed above the action level.
- Hand-arm vibration: While not COSHH, the principle is the same. Health surveillance for workers regularly exposed to vibrating tools.
- Welding fumes: Lung function testing for regular welders.
- The substance name and manufacturer
- The hazard classification and risk phrases (from the SDS)
- How the substance is used and the exposure route
- Who is exposed and for how long
- The control measures in place
- Emergency procedures (first aid, spill response)
- PPE requirements with specification (type, standard, replacement frequency)
- Monitoring and health surveillance requirements
- Review date and assessor's name
- Generic assessments: A COSHH assessment that says "various chemicals" or "construction dust" is not adequate. Each substance and exposure scenario needs its own assessment.
- Missing process-generated substances: People remember to assess the tin of paint but forget about the silica dust generated by cutting the wall the paint goes on.
- Relying on PPE alone: Every COSHH assessment should explain why higher-level controls (elimination, substitution, engineering controls) are not reasonably practicable before specifying PPE.
- No SDS available: You cannot assess a substance without its safety data sheet. If you do not have the SDS, stop using the product until you get one.
- Assessments not communicated: An assessment locked in a filing cabinet is useless. Workers must be informed of the hazards and the controls. This is usually done through toolbox talks and site inductions.
- Never reviewed: Assessments should be living documents. Review them when substances change, work methods change, or monitoring shows controls are inadequate.
Key point: PPE should be your last line of defence, not your first. If your COSHH assessment says "wear a dust mask" but does not explain why dust suppression or extraction is not being used, it is inadequate. The HSE will challenge this.
Monitoring and Health Surveillance
For certain substances, COSHH requires workplace exposure monitoring and health surveillance:
Health surveillance records must be kept for 40 years. This is not a typing error. The latency period for diseases like mesothelioma and silicosis can be decades.
Documentation Requirements
A proper COSHH assessment should include:
Site Manager AI can generate COSHH assessments tailored to specific substances and work activities on your site. It pulls the right hazard information, suggests appropriate control measures, and formats the assessment to meet regulatory requirements. What used to take 30 minutes per substance can be done in under 5 minutes.
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