How to Write a COSHH Assessment

Compile a complete inventory of all substances used in, produced by, or arising from the work activity. This includes: raw materials (cleaning products, adhesives, paints, solvents, acids, alkalis, lubricants); substances produced during the work (welding fumes, wood dust, silica dust, exhaust fumes); waste products; and biological agents where relevant (healthcare settings, waste handling, agriculture).

Do not limit the inventory to products with obvious hazard labels. Many common workplace substances — including some paints, adhesives, and cleaning agents — are hazardous. Also consider substances produced by work processes that may not come in labelled containers: welding fumes, rubber fume from moulding operations, engine exhaust, and biological aerosols from water systems.

Obtain the current Safety Data Sheet (SDS) for every substance. Suppliers are required by the CLP Regulation to provide an SDS for all hazardous substances. Section 2 of the SDS identifies the hazards; section 8 gives exposure limits and recommended protective equipment. If an SDS is not available, request it from the supplier before any work involving the substance begins.

The SDS is the starting point for the COSHH assessment but not the whole assessment. The SDS tells you what the hazards of the substance are; the COSHH assessment tells you whether workers in your workplace are actually exposed to those hazards and at what level.

From the SDS, identify: the health hazards (section 2) — is the substance toxic, carcinogenic, a sensitiser, a reproductive toxicant?; the WEL or OEL (section 8) — what is the legal maximum airborne concentration?; the recommended control measures (section 8) — what engineering controls and PPE does the manufacturer recommend?; and first aid measures (section 4) and emergency spill procedures (section 6).

Note any substances that are classified as carcinogens (category 1A or 1B), mutagens, or reproductive toxicants — these require prevention of exposure (not just control) under COSHH reg 7(1). Note any substances that are skin or respiratory sensitisers — once sensitised, a worker may react to very low concentrations and may need to be removed from the work activity.

For each substance, assess which workers (and which non-workers, such as contractors or members of the public) may be exposed, and through what route and at what level. Routes of exposure include: inhalation (the most significant route for most workplace substances); skin absorption (important for solvents, pesticides, and some reactive compounds); skin and eye contact (corrosives, irritants); and ingestion (typically from poor hygiene practices, not deliberate).

Assess the likely level of exposure: how long and how often are workers exposed? What is the physical form of the substance during use (vapour, mist, dust, fume)? Is it used in an enclosed space or in the open? Is there existing ventilation, local exhaust ventilation (LEV), or enclosure? Comparison with the WEL (EH40) requires either measurement by occupational hygiene sampling or a justifiable engineering assessment.

COSHH reg 7 requires the hierarchy of controls to be applied in order: first, prevent exposure by not using the substance or by substituting it with a less hazardous alternative; if prevention is not reasonably practicable, control exposure adequately using measures other than PPE — engineering controls (LEV, enclosure, general dilution ventilation), administrative controls (reduced exposure time, health surveillance, work procedures); and PPE only as a last resort or in addition to other controls.

For carcinogens and sensitisers, prevention by elimination or substitution must be achieved if it is reasonably practicable. If not, LEV is typically required; PPE alone is not adequate control for carcinogens under COSHH reg 7(1). For substances with a WEL, compliance must be demonstrated — either by measurement showing concentrations are below the WEL, or by engineering assessment showing that control measures are sufficient to achieve this.

Record the COSHH assessment for each substance. The record should cover: the substance name and SDS reference; the hazards identified; who is exposed and how; the current controls; the adequacy of current controls (including whether the WEL is met); additional controls required; the residual risk; and the health surveillance requirement.

Maintain the assessment records for at least 5 years (COSHH reg 18). Where health surveillance is carried out, the records must be retained for 40 years. Make assessments available to workers and their representatives — this is both a legal requirement (COSHH reg 12) and good practice.

COSHH reg 11 requires health surveillance where workers may develop a work-related disease or adverse health condition from exposure, and where valid techniques exist to detect it. Mandatory health surveillance exists for specific substances and processes listed in COSHH Schedule 6 (including rubber fume, coal dust, and work with ionising radiation). Beyond Schedule 6, health surveillance should be arranged where there is a reasonable likelihood of disease — for example, lung function tests for workers exposed to respiratory sensitisers, audiometric testing for noise exposures, and skin inspection for workers using skin sensitisers.

Health surveillance records must be kept for 40 years after the last entry. Workers have a right to access their own health surveillance records.