COSHH Assessments in Construction: A Practical Guide

Construction workers are exposed to hazardous substances every day. Silica dust from cutting concrete and stone. Cement that causes dermatitis and chemical burns. Solvents in paints and adhesives. Asbestos in refurbishment and demolition projects. Diesel exhaust fumes from plant and vehicles. The Control of Substances Hazardous to Health Regulations 2002 (COSHH) require employers to assess and control these exposures, yet COSHH compliance on construction sites remains patchy at best. This guide provides a practical, step-by-step approach to COSHH assessments that actually works on a busy construction site.

What Is COSHH and Why Does It Matter?

COSHH stands for the Control of Substances Hazardous to Health Regulations 2002. These regulations require employers to prevent or adequately control workers' exposure to hazardous substances. In construction, this is not a niche concern. The HSE estimates that approximately 500 construction workers die each year from occupational cancers caused by past exposure to hazardous substances, particularly asbestos and silica dust. That is more than ten times the number killed in construction accidents.

Occupational lung disease, skin disease, and cancer do not happen immediately. A bricklayer cutting blocks without dust suppression today may not develop silicosis for 15-20 years. This long latency period means the true cost of poor COSHH management is hidden from current site teams. But it is real, and it is devastating.

What Does COSHH Cover?

COSHH applies to virtually all hazardous substances, including:

• Substances with workplace exposure limits (WELs) -- chemicals with defined maximum exposure concentrations (listed in HSE publication EH40)
• Substances classified as hazardous under CLP Regulation -- products with hazard pictograms on their labels (skull and crossbones, exclamation mark, health hazard, etc.)
• Biological agents -- bacteria from contaminated soil or water (e.g., Weil's disease from rat urine in excavations)
• Dust of any kind when present in substantial concentrations (the general WEL for inhalable dust is 10 mg/m3 and for respirable dust is 4 mg/m3)
• Any substance that can harm health through inhalation, skin contact, ingestion, or injection

COSHH does not cover asbestos (which has its own regulations -- the Control of Asbestos Regulations 2012), lead (Control of Lead at Work Regulations 2002), or radioactive substances. However, on a practical level, the assessment process for these is very similar.

Common Hazardous Substances on Construction Sites

Silica Dust (Respirable Crystalline Silica -- RCS)

Silica dust is generated whenever concrete, morite, sandstone, granite, or brick is cut, drilled, ground, or demolished. The workplace exposure limit for RCS is 0.1 mg/m3 -- an extremely low concentration that is easily exceeded during dry cutting. Prolonged exposure causes silicosis (irreversible lung scarring) and lung cancer. The HSE has made silica dust a priority enforcement area.

Cement

Wet cement is a strong alkaline substance (pH 12-13) that can cause chemical burns on prolonged skin contact. Cement also contains hexavalent chromium (chromium VI), a known carcinogen. EU regulations limit chromium VI content, but exposure should still be minimised. Allergic contact dermatitis from cement is one of the most common occupational skin diseases in construction.

Wood Dust

Hardwood dust is classified as a carcinogen (can cause nasal cancer). Softwood dust is a respiratory sensitiser. The workplace exposure limit for all wood dust is 3 mg/m3 (previously 5 mg/m3, reduced in 2020). Cutting, sanding, and routing timber all generate wood dust.

Solvents and Adhesives

Products containing toluene, xylene, acetone, and other organic solvents are widely used in construction -- paints, varnishes, adhesives, sealants, and cleaning products. Exposure can cause headaches, dizziness, and liver damage. In confined spaces, solvent vapours can reach concentrations that cause unconsciousness and death.

Diesel Exhaust Emissions (DEE)

Diesel exhaust is classified as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC). Construction workers operating or working near diesel-powered plant are exposed to DEE, particularly in enclosed or poorly ventilated areas. This is an emerging area of concern with increasing regulatory attention.

COSHH Assessment: Step by Step

Step 1: Identify Hazardous Substances

Walk your site and list every substance or process that could generate hazardous exposures. Check product labels and safety data sheets (SDS) for chemical products. Consider dust generated by cutting and demolition activities. Think about biological hazards in excavations and refurbishment work.

Common mistake: focusing only on chemical products in containers and ignoring process-generated hazards like dust and fumes. The most significant COSHH hazards on construction sites are typically silica dust, wood dust, and welding fumes -- none of which come in a container with a label.

Step 2: Assess the Risks

For each substance or process, determine:

• What is the substance and what harm can it cause?
• How are workers exposed (inhalation, skin contact, ingestion)?
• Who is exposed and for how long?
• What is the likely level of exposure compared to the WEL?
• Are existing controls adequate?

Safety data sheets provide essential information about the hazards of chemical products, but they are not COSHH assessments. An SDS tells you what a substance can do. A COSHH assessment tells you what it will do in your specific work situation and what controls you need.

Step 3: Implement Controls

COSHH requires employers to follow a hierarchy of control:

1. Elimination -- can you avoid using the substance entirely? For example, using mechanical fixings instead of solvent-based adhesives.
2. Substitution -- can you use a less hazardous alternative? Water-based paints instead of solvent-based. Pre-cast concrete elements instead of in-situ cutting.
3. Engineering controls -- local exhaust ventilation (LEV), water suppression for dust, enclosed systems for mixing.
4. Administrative controls -- reducing exposure time, restricting access to contaminated areas, providing training.
5. PPE -- respiratory protective equipment (RPE), gloves, overalls. Always the last resort, never the first response.

Step 4: Record the Assessment

The assessment must be written down and kept accessible. It should include the substances identified, the risks assessed, the controls implemented, and the date of assessment. Assessments should be reviewed regularly (at least annually, or whenever the work changes).

Step 5: Train Workers

Workers must be told what substances they are working with, what the health risks are, what controls are in place, what PPE they must use, and what to do in an emergency (spill, splash, excessive exposure). This training should be part of site induction and reinforced through toolbox talks.

Silica Dust Control: Getting It Right

Given the seriousness of silica dust exposure, this section provides specific guidance on dust control measures for the most common dust-generating activities on construction sites:

• Block cutting -- use a water-suppressed bench saw. Never dry cut concrete, brick, or stone blocks on site. If a water supply is not available, use a battery-powered wet saw or pre-cut blocks off-site.
• Chasing walls -- use a chaser with integrated dust extraction connected to an M-class (minimum) vacuum. H-class is preferable for silica dust.
• Drilling concrete -- use a drill with dust extraction or water suppression. For SDS drilling, a drill-mounted extraction unit is available.
• Demolition -- water suppression (damping down) to prevent dust becoming airborne. Consider enclosure for internal demolition.
• Sweeping -- never dry sweep areas contaminated with silica dust. Use an M-class vacuum or damp mopping.

The HSE's "No Time to Lose" campaign provides extensive guidance on controlling silica dust exposure. Their enforcement approach is clear: dry cutting of concrete, brick, or stone on construction sites will result in enforcement action. There is no defence for dry cutting when water suppression and extraction technologies are readily available.

COSHH Health Surveillance

Health surveillance is required where workers are exposed to substances with specific health surveillance requirements, exposure is above the WEL or action level, or there is a reasonable likelihood that exposure will cause an identifiable disease or adverse health effect.

For construction workers, the most common health surveillance requirements are:

• Lung function testing (spirometry) -- for workers exposed to silica dust, wood dust, or other respiratory sensitisers
• Skin checks -- for workers exposed to cement, solvents, or other skin sensitisers
• Audiometry -- technically under Noise Regulations rather than COSHH, but often conducted as part of the same programme

Health surveillance records must be kept for at least 40 years. This long retention period reflects the latency of occupational diseases -- a worker exposed to silica dust in their 20s may not develop silicosis until their 50s or 60s.

COSHH Record Keeping

Good record keeping is essential for COSHH compliance. You should maintain COSHH assessments for every substance and process, safety data sheets for all chemical products used on site, training records showing that workers have received COSHH training, health surveillance records, air monitoring results (if exposure monitoring has been carried out), and equipment maintenance records for LEV systems and RPE.

Using digital documentation tools makes COSHH record keeping significantly easier. A digital system allows quick retrieval of assessments, automated review reminders, and easy sharing with the HSE during inspections. FORGE Command supports comprehensive digital site management including safety documentation.