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Silica in Construction: Changes to approved methods of roof tile cutting

Roof terminology

The challenge

Where roofs meet, valley tiles need to be cut or trimmed to fit. The dust this process generates contains respirable crystalline silica (RCS) and, if breathed in, can cause severe lung diseases in workers, such as silicosis.

Impact of silicosis (video)

Dust suppression systems use water to control the generation of tile dust and reduce worker exposure, but these systems can raise the risk of other hazards, such as slips. To mitigate against these hazards, an interim agreement between HSE and industry allowed valley tiles to be cut using hand held power tools without water suppression. However, HSE needed to understand the impact of this decision on worker health.

The solution

HSE's Science Division engaged in a research project that would scientifically assess the health risks associated with cutting valley tiles without water suppression by measuring worker exposure to RCS.

The project was performed on three new-build construction sites. The work consisted of measuring exposure to RCS whilst workers were cutting tiles on site and assessing the controls they were using, such as the use of respiratory protective equipment (RPE).

As tile cutting is a quick task typically happening only once or twice per day, conventional sampling techniques were not suitable to assess worker exposure, therefore HSE researchers needed to use innovative high volume respirable dust samplers to measure exposure during the short duration workers were exposed. Additionally they used an exposure visualisation technique (ELVIZ) to create a video of the cutting process to demonstrate real time worker exposure levels.

The outcome

The exposure monitoring showed that if a worker cut two roof edges of valley tiles in a shift, equating to about fifteen minutes of work, then they would have already reached or exceeded the eight hour time weighted average RCS exposure limit.

The data also demonstrated that adjacent workers were at significant risk and that the use of other exposure controls, such as dust masks, could be improved. RPE was found not to usually provide effective exposure reduction due to poor use.

Changes to working practice

The findings provided the robust evidence required to change working practices in the construction sector. Valley tiles are now marked up at roof level and taken to a fixed location where they are cut whilst using engineering controls such as water suppression.


HSE's 'Dust Kills' campaign raises awareness of the risk to workers.


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