RR689 - Silica baseline survey

The Silica Baseline Survey (SBS) has established baseline intelligence on employee exposures and the control of respirable crystalline silica (RCS) in 4 UK industry sectors: brick- and tile-manufacture, stonemasonry, quarrying and construction.

The objectives were:

  1. to establish whether engineering controls and the use of respiratory protective equipment (RPE)) were adequate to reduce exposures below the Workplace Exposure Limit (WEL) for RCS;
  2. to assess the reliability of the exposure controls (termed "competence");
  3. to identify common causes of failures of exposure controls, and
  4. to provide data against which the effect of HSE interventions can be assessed in future.


Assessments had not always been made as required by the Control of Substances Hazardous to Health ("COSHH") Regulations for tasks that cause RCS exposure, and there was an almost universal lack of adequate RPE training and face-fit testing. In general, the measured exposures and the effectiveness of exposure controls reflected the expertise applied to the COSHH assessments for silica. Engineering controls often failed to deliver the desired exposure reductions because of either poor design or neglected maintenance.

At brickworks, where Local Exhaust Ventilation might have been practicable, better-specified and engineered systems would have been necessary if the full benefits of such investment were to be realised.

The construction activities assessed revealed that effective exposure control was achieved where risk assessments hade been performed, but uncommon in their absence.

Nearly half of the measurements of exposures at stonemasons exceeded the 2006 WEL for RCS. Engineering controls were usually either completely lacking or of limited effectiveness, the latter due either to the selection of unsuitable equipment or inadequate design and installation.

RCS exposure was generally adequately controlled in quarries. Large quarry groupings were well-equipped in terms of health and safety expertise, but exposure control regimes failed if neglected.

This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the author alone and do not necessarily reflect HSE policy.

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Updated 2021-04-23