Health and Safety Laboratory tests on three tool systems designed to reduce workers’ exposure to respirable crystalline silica (RCS) have revealed large variations in their effectiveness.
None of the systems – which were tested by HSL operators who were independent of the three tool manufacturers – came below the Workplace Exposure Limit (WEL) for RCS, which is 0.1 mg/m3 respirable dust, averaged over 8 hours. But a worker would be twenty times more exposed, depending on which tool they used.
The study was commissioned by Hilti which approached HSL. Three systems were tested, each consisting of a circular blade, saw and a matching vacuum unit as recommended by the manufacturer.
Tests took approximately one hour, repeated three times, in an airtight 200m² room. The task involved using the diamond blade insert to make a minimum of 13.2m long, 40mm deep cuts into concrete slabs. The inhalable and respirable dust concentrations were measured in the breathing zone of the operator and the mean average was calculated.
The mean of respirable dust, which is the deadliest form of RCS because it can penetrate the deepest parts of the lung, was 0.85 mg/m³ (milligrams per cubic metre) for Hilti’s system. Makita’s system (system two) came in next highest at 7.65m³ and Husqvarna’s system (system three) was 15.65m³.
Walid Hussain, national tool hire manager at Hilti, told Safety Management: “We created the project as we wanted to see whether all dust extraction systems perform equally – as is the general consensus in the marketplace – or whether there are variations between different manufacturers.”
“To do this we selected an important construction site task which is synonymous with the amount of dust it creates, and we selected the other manufacturers’ products on the basis they are two of the leading diamond cutting tools by sales volume in the professional UK construction sector.”
He added that the results show the limitations of any tool to reduce dust exposure. But that having the figures to hand on any tools’ effectiveness could help make better choices: “As of today – as far as both Hilti and the HSE are aware – there is not a diamond cutting tool which can meet the UK’s WEL dust exposure limits.”
“However, with RCS now classed as a carcinogen, the user needs to reduce the exposure to as low as reasonably practicable in-line with The Control of Substances Hazardous to Health Regulations 2002 (COSHH) regulations.”
Silica dust is a hazardous substance. The dust can be very fine and if it gets deep into the lungs, it can cause serious lung diseases such as lung cancer, silicosis and chronic obstructive pulmonary disease.
The report by lead author Dominic Pocock, a scientist at HSL, says: “There is a legal duty for employers to prevent or adequately control worker exposure to construction dust. On-tool extraction is an effective control for this dust and will reduce the risk of ill health.”
It adds the disclaimer: “This report and the work it describes were undertaken by the Health and Safety Laboratory under contract to Hilti. Its contents, including any opinions or conclusions, do not necessarily reflect policy or views of the Health and Safety Executive.”
Assessment of dust extraction system solutions on hand-held electric diamond cutters to BS EN 50632: bit.ly/2vuno2y
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