4.1 Control of Substances Hazardous to Health (COSHH) Regulations & Exposure Limits

Introduction to COSHH Regulations 2002

Occupational health hazards in construction cause thousands of premature deaths and chronic illnesses annually across the United Kingdom. While safety management frequently focuses on immediate physical accidents such as falls or structural collapses, health hazards such as chemical exposures, toxic dusts, and biological agents cause long-term, debilitating conditions including occupational asthma, dermatitis, central nervous system damage, and fatal cancers. The primary statutory framework governing chemical and biological safety in the UK construction industry is the Control of Substances Hazardous to Health Regulations 2002 (COSHH) (as amended).

Under COSHH, employers, main contractors, site managers, and self-employed persons have clear legal duties to protect workers and others from the harmful effects of hazardous substances arising from work activities. Site managers must ensure that no work is undertaken involving hazardous substances until a suitable and sufficient COSHH risk assessment has been completed, suitable control measures are fully implemented, and workers are trained in safe operating procedures.

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Scope and Classification of Hazardous Substances

COSHH applies to a vast range of substances found or generated on construction sites. Understanding what falls within the scope of COSHH is critical for effective site health management:

Substances Covered by COSHH

• Chemical substances: Solvents, adhesives, paints, resins, brick acid, formwork release agents, sealants, curing compounds, and chemical anchors.
• Dusts generated by site activities: Concrete dust, brick dust, mortar dust, wood dust (hardwood and softwood), sandstone dust, tile dust, and plaster dust.
• Fumes, gases, and mists: Welding fumes, soldering flux fumes, diesel engine exhaust emissions (DEEEs), asphalt/bitumen fumes, and paint spraying mists.
• Biological agents: Bacteria, viruses, and fungi encountered during groundworks, demolition, or refurbishment, such as Leptospira bacteria causing Weil's disease (leptospirosis) from rat urine, Legionella bacteria in stagnant pipework, and bird/bat guano containing fungal spores.

Substances Excluded from COSHH

Certain severe health hazards are governed by dedicated statutory regulations rather than COSHH. Specifically, asbestos (covered by the Control of Asbestos Regulations 2012), lead (covered by the Control of Lead at Work Regulations 2002), and radioactive substances or ionising radiation are excluded from COSHH because they have specialized, highly specific legal codes.

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Safety Data Sheets (SDSs) and the CLP Framework

Under the European CLP Regulation (Classification, Labelling and Packaging) retained in UK law, chemical manufacturers and suppliers are legally required to classify, label, and package hazardous chemicals correctly. They must also provide a Safety Data Sheet (SDS) for every hazardous product supplied to a construction project.

An SDS contains 16 mandatory sections outlining the chemical composition, health hazards, emergency first-aid measures, fire-fighting protocols, handling and storage rules, exposure controls, and disposal requirements.

Critical Site Management Rule: An SDS is not a COSHH assessment! An SDS is a product information document provided by the manufacturer. A COSHH assessment is a site-specific risk assessment created by the contractor that evaluates how that product will be used in a specific location, by specific workers, using specific tasks and methods.

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Workplace Exposure Limits (WELs)

The Health and Safety Executive (HSE) publishes guidance document EH40: Workplace Exposure Limits, which contains the legal statutory limits for airborne concentrations of hazardous substances. Employers must ensure that airborne exposure to any substance with a WEL does not exceed the published limit.

WELs are measured using standard reference periods:

1. 8-hour Time-Weighted Average (8-hr TWA): Designed to protect workers against long-term, chronic health effects over a standard working day and 40-hour working week.
2. 15-minute Short-Term Exposure Limit (15-min STEL): Designed to prevent acute health effects, irritation, or toxic spikes resulting from brief, intense exposures.

Compliance Duties under EH40

• Substances with WELs: Exposure must be reduced below the WEL, and for carcinogenic, mutagenic, or asthma-causing substances, exposure must be reduced to As Low As Reasonably Practicable (ALARP) below the limit.
• Air Monitoring: Where exposure levels are uncertain, or where controls might fail, employers must conduct formal personal air monitoring to quantify exposure against EH40 limits.

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The Eight Steps of COSHH Risk Assessment

Site managers must follow a systematic 8-step process when completing and implementing COSHH assessments:

1. Gather Information: Identify all hazardous substances used, generated, or encountered on site, and obtain SDSs.
2. Evaluate Health Risks: Determine who might be harmed, how exposure can occur (inhalation, skin contact, ingestion), and the severity of potential health effects.
3. Determine Control Measures: Select appropriate controls following the statutory COSHH Hierarchy of Controls.
4. Implement Controls: Ensure controls are installed, commissioned, and made fully available before work commences.
5. Maintain and Test Controls: Establish inspection regimes, maintenance logs, and mandatory testing schedules for control equipment.
6. Monitor Exposure: Conduct air sampling or workplace exposure monitoring where required to demonstrate compliance with WELs.
7. Conduct Health Surveillance: Provide routine health checks (e.g. lung function tests, skin checks) where appropriate.
8. Inform, Instruct, and Train: Deliver site inductions, toolbox talks, and task-specific training to all exposed operatives.

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The COSHH Hierarchy of Control Measures

COSHH Regulation 7 explicitly requires employers to apply control measures in a strict hierarchical order. Personal Protective Equipment (PPE) is strictly the last line of defense.

1. Elimination: Completely remove the hazard (e.g. purchasing pre-cut brickwork or off-site fabricated concrete elements to eliminate on-site cutting dust).
2. Substitution: Replace the hazardous substance with a safer alternative (e.g. substituting solvent-based paints with water-based paints, or replacing toxic chemical anchors with mechanical fixings).
3. Engineering Controls: Control the hazard at source using physical plant or isolation (e.g. Local Exhaust Ventilation [LEV] on power tools, water suppression systems on masonry saws, total enclosure of mixing operations).
4. Administrative Controls: Modify work practices and management systems (e.g. limiting the number of exposed workers, job rotation, restricting access to hazardous zones, establishing clear cleaning routines).
5. Personal Protective Equipment (PPE) & Respiratory Protective Equipment (RPE): Provide suitable protective clothing, gloves, eye protection, and respirators only as a last resort or supplementary measure alongside engineering controls.

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Maintenance, Examination, and Testing of Controls

Under COSHH Regulation 9, employers must maintain all control measures in efficient working order, good repair, and proper state.

• Local Exhaust Ventilation (LEV): All LEV systems (such as dust extraction units connected to saws or grinders) must undergo a thorough examination and performance test by a competent engineer at least once every 14 months.
• Inspection Records: Records of LEV examinations, maintenance, and repair work must be retained for at least 5 years.
• RPE Maintenance: Non-disposable respiratory equipment must be inspected visually before each use and thoroughly examined monthly (or every 3 months if used infrequently).

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Common Construction Chemical and Biological Hazards

Site managers must recognize key workplace health hazards specific to construction:

• Portland Cement & Wet Concrete: Contains hexavalent chromium (Chromium VI), causing severe irritant contact dermatitis, allergic contact dermatitis, and chemical burns.
• Solvent Vapors: Solvents in paints, thinners, and adhesives cause central nervous system depression, dizziness, headaches, and long-term organ damage.
• Wood Dust: Hardwood dust is a classified Category 1 human carcinogen (causing sino-nasal cancer), while both hardwood and softwood dust cause occupational asthma.
• Leptospirosis (Weil's Disease): Contracted through skin contact or ingestion of water contaminated with rat urine during excavations, sewer work, or riverbank construction. Causes flu-like symptoms leading to liver and kidney failure.