Silica Risk Assessment
Monitoring · Monitoring overview
A silica risk assessment is the structured COSHH review of every task, material and control in a workplace that could expose a worker to respirable crystalline silica. It defines who is exposed, by how much, under which controls, and what residual silica exposure remains — the basis on which silica compliance is judged adequate or not under COSHH.
What a silica COSHH assessment covers
A silica COSHH assessment — silica risk assessment, silica hazard assessment or silica exposure assessment in common usage — covers four linked questions. Which tasks generate respirable crystalline silica? Which materials and processes drive that exposure? Which silica controls are in place at the task, and how well are they performing? What residual silica exposure remains for each operator, expressed against the silica WEL?
The assessment is not paperwork in isolation. It is the document that defends decisions about substitution, water suppression, on-tool extraction, enclosure, silica LEV, RPE selection and health surveillance scope. If those decisions cannot be traced back to the silica risk assessment, the assessment is incomplete.
Building the silica exposure profile
The first practical step is to map silica-generating tasks across the workplace: cutting, chasing, grinding, drilling, breaking, scabbling, polishing, blasting, sweeping, tipping, demolition and any process that re-entrains previously generated silica dust. Each task is paired with its materials (concrete, brick, mortar, sandstone, granite, engineered stone, blasting media) and the typical duration and frequency per operator.
Where personal silica air sampling data exists for similar tasks, materials and controls, it is used to anchor the exposure profile. Where it does not, the silica risk assessment will normally trigger silica dust monitoring to provide that anchor rather than rely on assumption. A silica workplace risk that has no exposure data behind it is a silica workplace risk that cannot be defended.
- Map every silica-generating task to materials, duration and frequency.
- Identify the operators routinely exposed and the wider population affected.
- Anchor the profile to personal silica air sampling data where available.
- Commission silica monitoring where no representative data exists.
- Account for re-entrainment from sweeping, compressed-air cleaning and demolition.
Reviewing silica controls against the COSHH hierarchy
Each silica-generating task is reviewed against the COSHH hierarchy in the order that hierarchy demands. Can the silica-bearing material be substituted (for example, lower-silica engineered stone, alternative blasting media)? Can the task be eliminated (pre-cut units delivered to size)? Can water suppression be applied at the cut? Can on-tool extraction be fitted and maintained at M-class? Can the task be enclosed? Is silica LEV in place with adequate capture velocity and a current Regulation 9 thorough examination? Is RPE used only as a residual control, with fit testing and assigned protection factor recorded?
The assessment then judges whether the combination of controls actually in place is adequate to keep silica exposure below the silica WEL. Adequacy is judged against measured silica exposure data wherever possible, not against intent.
Documenting residual silica exposure
Residual silica exposure — the exposure remaining after controls — is documented per similar exposure group, with reference to the personal silica air sampling results that support it. The silica risk assessment makes explicit where exposure sits comfortably below the WEL, where it sits near an in-house action level and warrants closer monitoring, and where it approaches or exceeds the WEL and requires control improvement.
It also documents the assumptions made: RPE assigned protection factors used in the residual exposure judgement, the representativeness of the sampling dataset, and any tasks that could not be sampled and have therefore been assessed by analogy.
Linking to health surveillance and review triggers
Operators who are routinely exposed to respirable crystalline silica are expected to be brought into health surveillance proportionate to the exposure profile. The silica risk assessment defines who falls inside that population and at what frequency surveillance should run. Surveillance findings — symptom reports, lung function changes — feed back into the assessment.
The assessment also defines its own review triggers: new tasks or materials, changes to water suppression, on-tool extraction or silica LEV, new operators, monitoring results above the in-house action level, health surveillance findings of concern, workplace inspections, or simply the elapsed time since the last review. Silica compliance is judged on whether reviews are actually triggered when those conditions are met.
When to commission a silica risk assessment
A silica risk assessment is normally commissioned when introducing new silica-generating processes, switching materials (engineered stone is a common trigger), redesigning workshop layout or extraction, responding to a workplace inspection or enforcement notice, supporting a tender or insurance requirement, or refreshing an out-of-date COSHH assessment.
It is also commissioned proactively where a workplace has grown beyond the assumptions of its existing COSHH paperwork — additional cutting equipment, additional operators, additional shifts, or higher throughput than the original silica control system was designed for.
Frequently asked questions
What is the difference between a silica risk assessment and a generic COSHH assessment?
A silica risk assessment is a COSHH assessment focused specifically on respirable crystalline silica — silica-generating tasks, silica-bearing materials, silica controls and residual silica exposure against the silica WEL. A generic COSHH assessment that mentions silica in passing is rarely sufficient where silica is a primary exposure on the site.
How often should a silica risk assessment be reviewed?
A silica risk assessment should be reviewed whenever tasks, materials or controls change in a way that could plausibly alter silica exposure, whenever monitoring or health surveillance findings suggest exposure has changed, and otherwise at a defined periodic interval proportionate to the silica workplace risk. Engineered stone, abrasive blasting and high-volume concrete cutting workplaces typically warrant shorter review intervals.
Do I need silica monitoring data before completing a silica risk assessment?
In most cases, yes. A silica risk assessment that judges adequacy of controls without measured silica exposure data is making assumptions. Personal silica air sampling for representative operators and tasks is usually the practical way to anchor the exposure profile against the silica WEL.
Does a silica risk assessment cover RPE selection?
It should. The silica risk assessment defines the residual silica exposure after engineering controls, which in turn defines the assigned protection factor needed from RPE and therefore the RPE class. It also flags where RPE is being used to compensate for inadequate engineering control — a common gap that the assessment is supposed to surface.
Who carries out a silica risk assessment?
Silica risk assessments are normally carried out by, or with the support of, a competent occupational hygienist familiar with respirable crystalline silica, personal silica air sampling and the COSHH control hierarchy. The duty to ensure the assessment is suitable and sufficient rests with the employer.
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