Case Studies

COSHH Assessment at Salisbury Cathedral Stonemasons

Envirocare recently carried out a COSHH assessment within Salisbury Cathedral near Southampton. The main focus of the study was determination of the levels of respirable dust and respirable crystalline silica.

Respirable crystalline silica is a carcinogenic substance, examples of where this is a risk include when stonework is cut, sanded or fettled.

COSHH Assessment at Salisbury Cathedral Stonemasons


What Is Crystalline Silica?

Crystalline silica is a group of substances containing silcon and oxygen that are naturally occurring and have large rigid chemical structures. There are numerous forms of crystalline silica, with the most common forms being quartz and cristobalite, both of which we monitor for.



Quartz and Cristobalite

Quartz and Cristobalite


What Is Respirable Crystalline Silica?

The respirable fraction of dust is the dust particles that have such a small diameter that they can enter the deep lung, and are therefore beyond the body’s natural defences. These particles are generally less than 10µm in diameter (about a fifth of the diameter of a human hair)

You can read more about The Dangers of Silica Dust.


What Did Envirocare Do?

Poor Positioning of LEV

The monitoring campaign was carried out in the stonemasonry workshop where operators were observed to be shaping blocks of stone to replace ancient stones within the cathedral’s walls. The processes involved fettling, use of power tools and hand grinding tools to give stones the right finish. The work was carried out as described in MDHS 101.

There was some control measures already in place, such as capture hoods and mechanical and natural ventilation, however effectiveness of these was limited due to poor positioning. The capture hoods were a significant distance from the source of the stressor.

Levels of respirable dust ranged between 12% and 26% of the Workplace Exposure Limit (WEL) of 4mg/m3 for respirable dust, all of which are considered significant but low. All of the samples were further analysed for respirable crystalline silica by X-Ray Diffraction, and the results were between 30% and 60% of the WEL of 0.1 mg/m3 for respirable crystalline silica, two of these results fell into the “significant” category.


What Did We Recommend?

As part of the COSHH assessment we made a number of client specific recommendations including:


+ Provide information, instruction and training on correct placement of ducting.

+ Investigate alternatives to using a paint brush to remove excess.

+ Ensure that workbenches are cleaned on a regular basis.

+ Consider installation of down draught tables in the workshop.


Your COSHH Assessment Experts

Envirocare is a leading Environmental and Occupational Hygiene and Health services provider with over 20 years of experience throughout the UK.

Call us on 01274 738668 or fill out our Envirocare Enquiry Form for any queries regarding COSHH Air Monitoring, Occupational Exposure Assessments, LEV Testing or any of our many other accredited Environmental and Occupational Hygiene services.


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