Management

HSE advances dust exposure investigation

28 February 2020

Report on power tools raises concerns about worker exposure levels to respirable crystalline silica.

The Health & Safety Executive (HSE) has completed an investigation into construction dust risks, publishing a report on power tool dust extraction systems which shows wide variations in worker exposure levels.

The report, which has been shared with CM, follows laboratory tests of three tool manufacturers’ dust extraction systems for hand-held electric diamond cutters, to examine exposure levels to respirable crystalline silica (RCS). In January, the HSE recognised RCS as a carcinogen.

The tests (see box) on the first manufacturer’s system – the best performing of the three – recorded respirable dust levels of 0.85 mg.m-3. This jumped nine-fold to 7.65 mg.m-3 for the second manufacturer’s system, while the third manufacturer’s tests were 18 times higher at 15.65 mg.m-3.

The HSE’s Workplace Exposure Limit stands at 0.1 mg.m-3, though this is across an eight-hour working day.

“As there is a high health risk, this means that a high level of exposure control should be applied when using diamond cutters.”

HSE report

The tests were carried out at the HSE’s Health and Safety Laboratory (HSL) last year and the report has been authored by HSE scientists Dominic Pocock, John Saunders and Adam Clarke.

Exposure control

“Diamond cutters are often used to cut concrete and natural stone, both of which can contain high levels of crystalline silica, in the case of concrete up to 70%. Using power tools to abrade materials containing silica releases dust that contains RCS [which] has been classified as carcinogenic to humans,” the report explains.

“The Control of Substances Hazardous to Health (COSHH) regulations state, ‘control exposure by measures that are proportionate to the health risk’.

“As there is a high health risk, this means that a high level of exposure control should be applied when using diamond cutters. 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.”

The tests follow last year’s HSE dust campaign, with inspectors visiting construction sites to examine worker exposure levels.

The HSE estimates that past occupational exposure to known and probable carcinogens accounts for about 8,000 cancer deaths each year – and the construction industry has the largest proportion of these deaths, around 3,500. The majority are linked to asbestos and silica.

How the tests were carried out

The HSL tests examined the effectiveness of three manufacturers’ dust extraction system solutions for hand-held electric diamond cutters. Each test followed European standards BS EN 50632-1:2015 and BS EN 50632-2-22:2015.

Tests were performed at the HSL by trained and experienced operators who were independent of the three tool manufacturers. Three systems were tested, each consisting of a hand-held electric diamond cutter and a matching vacuum unit as recommended by the manufacturer.

All tools were operated as per the manufacturers’ guidance and using the manufacturers’ recommended circular blades. Three repeat tests were performed with each system with operators changed for each test to minimise the effects of their behaviour.

The efficacy of the dust control systems was assessed by measuring the concentration of respirable and inhalable dust in the breathing zone of the operator while using the tools to make cuts to a depth of 40mm in concrete paving slabs, meeting the requirements as specified in BS EN 50632-2-22.

Inhalable dust is the fraction that is inhaled through the nose and mouth. Respirable dust is the key value because this fraction can penetrate the deepest parts of the lung and cause diseases like lung cancer, asthma, chronic obstructive pulmonary disease (which includes emphysema and other breathing difficulties) and silicosis.

When using the first manufacturer’s system, the levels recorded were 0.85 mg.m-3 for respirable dust and 2.45 mg.m-3 for inhalable dust. For the second manufacturer’s system, the results rose to 7.65 mg.m-3 and 16.55 mg.m-3 for respirable and inhalable dust respectively, while the third manufacturer tests reported even higher dust concentrations of 15.65 mg.m-3 for respirable and 38.90 mg.m-3 for inhalable dust.

The full results of the tests can be found online at: https://bit.ly/2OO1r4H.

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