Construction Dust Toolbox Talk

The dust that damages your lungs is the dust you cannot see

The visible cloud settles in a minute. The respirable fraction hangs in the air for hours and travels deep into the lung, and it is still there long after the job looks finished.

HSE attributes more than 500 construction worker deaths a year to silica dust alone. The workplace exposure limit for respirable crystalline silica is 0.1 mg per cubic metre averaged over eight hours, an amount you would never notice on a bench. Wood dust is its own problem: hardwood dust causes nasal cancer, and carpenters and joiners are four times more likely to develop asthma than other UK workers.

Nothing about this shows up on the day

Silicosis takes at least ten years to develop. COPD creeps up as breathlessness you put down to age. Lung cancer arrives decades later. By the time you notice, the damage is done and none of it reverses, which is exactly why the controls have to be applied on days when everything feels fine.

What the law requires

Dust is a substance hazardous to health, so the Control of Substances Hazardous to Health Regulations 2002 apply in full. COSHH works on assess, control, review. Asbestos and lead sit under their own regulations and are not covered by this talk.

• Assess first. Assess the risk before work starts, for the actual material being cut and the actual method. COSHH 2002, reg. 6.
• Prevent, then control at source. Prevent exposure where reasonably practicable; where it is not, control it adequately at source. Respiratory protection comes last, not first. COSHH 2002, reg. 7.
• Keep the controls working. Local exhaust ventilation must be thoroughly examined and tested at least every 14 months, and the report kept. COSHH 2002, reg. 9.
• Health surveillance and training. Provide health surveillance where exposure could cause disease, and give everyone information, instruction and training. COSHH 2002, regs. 11 and 12.

How much silica is in what we cut

HSE publishes typical crystalline silica content by material. It is worth knowing which jobs are the bad ones:

• Engineered stone up to 95 per cent, the highest of any common material
• Sandstone, gritstone and quartzite over 70 per cent
• Concrete and mortar 25 to 70 per cent
• Granite around 30 per cent, slate 20 to 40 per cent
• Limestone and chalk under 2 per cent

Source: HSE, Control of exposure to silica dust (INDG463); COSHH 2002; HSE, EH40/2005 Workplace exposure limits.

How people get exposed on site

• Cutting and grinding masonry. A disc cutter with no water is the worst tool on most sites.
• Engineered stone worktops. Up to 95 per cent silica, and cases of severe silicosis in young fabricators are rising.
• Chasing and drilling. Wall chasers and breakers produce huge quantities of respirable dust in enclosed rooms with no ventilation.
• Wood dust. Hardwood causes nasal cancer. MDF is no safer.
• Dry sweeping and compressed air. The two habits that take settled dust and put it straight back in the air at head height.
• Demolition and soft strip. Everything at once, often in a confined space, often with nobody wearing anything.
• Cutting fibre cement and roof sheets. High silica content, usually done outdoors where people assume it disperses.
• Dust that travels. The person cutting may be masked up. The three trades downwind are not.
• Extraction that is not working. A full vacuum, a blocked filter, a missing shroud, or LEV that has never been examined.
• Water that runs out. A one-litre bottle on a cut-off saw lasts about a minute. After that you are cutting dry.
• Cleaning at the end of the shift. Often the dustiest twenty minutes of the day, and almost always done without RPE.

Controls to brief your crew on

• Design the dust out first. Order blocks, kerbs and slabs cut to size. Use pre-drilled and pre-formed materials. A block splitter makes no dust at all.
• Use water properly. Enough flow, running before the blade touches, and kept running. A trickle or a squirt bottle is not suppression.
• On-tool extraction of the right class. M-class as a minimum for silica, correct shroud for the tool, checked and emptied.
• Never dry sweep and never use compressed air. M-class vacuum, or damp down first.
• Keep other people out. Enclose or screen the work, sign it, and time dusty work so other trades are not alongside it.
• Ventilate enclosed spaces before, during and after.
• Check the LEV works, daily. Airflow indicator, hoses, filters, seals. Thorough examination at least every 14 months.
• RPE that is right and fits. Correct assigned protection factor, face fit tested, clean shaven at the seal, filters changed on schedule.
• Clean as you go so settled dust never gets the chance to become airborne again.
• Take up the health surveillance if it is offered. Lung function changes show on a test long before you notice them on the stairs.
• Report a control that is not working rather than working round it. A blocked vac is a job stopper, not an inconvenience.

Source: HSE, Controlling construction dust with on-tool extraction; HSE, Respiratory protective equipment at work (HSG53); COSHH 2002, regs. 7 and 9.

Who is competent to do this work

• Anyone using a dusty tool needs training on the extraction or suppression fitted to it, how to check it is working, and what to do when it is not.
• Whoever selects RPE must understand assigned protection factors. A disposable mask is not equivalent to a powered hood, and the task decides which is needed.
• LEV thorough examination must be done by a competent examiner, typically P601 qualified or equivalent, at least every 14 months.
• Health surveillance is set up on the advice of an occupational health professional, not designed by a site manager alone.

Paperwork that should be in place

• COSHH assessments for each dusty task, naming the material, the method and the controls, briefed to the people doing the work.
• LEV thorough examination reports, at intervals not exceeding 14 months, with defects closed out.
• Face fit test records for every tight-fitting facepiece, naming the exact make, model and size.
• Health surveillance records where exposure warrants it.
• Training records covering the tools, the controls and the health risks.
• Any exposure monitoring carried out, and what was done about the results.

Five questions to get the crew talking

1. What are we cutting or grinding on this site this week, and what is stopping the dust?
2. Is the water actually running for the whole cut, or is the bottle empty after the first one?
3. When was the vacuum last emptied, and when was its filter last checked?
4. Who is working downwind or in the next room while that is going on?
5. Is anyone coughing in the mornings, or more out of breath on the stairs than they used to be?

How to run this toolbox talk

1. Read it first and add your site-specific detail: which materials, which tools, which rooms.
2. Pick the moment. Start of shift, at the workface, ten minutes maximum.
3. Show the kit. Hold up the vac, the shroud and the water feed. Check them together in front of everyone.
4. Write down what came up. Notes and actions are on page 3 of the PDF.
5. Record who attended on the free toolbox talk sign-in sheet.
6. Close the actions out. Especially anything about equipment that is not working.

Frequently asked questions

What is the workplace exposure limit for silica dust?

0.1 mg per cubic metre of respirable crystalline silica, averaged over an eight-hour period. It is a legal maximum rather than a safe level, and exposure should be reduced as far below it as reasonably practicable.

Is a dust mask enough when cutting concrete?

Not on its own. COSHH requires exposure to be controlled at source first, which in practice means water suppression or on-tool extraction. RPE is the last layer, and it only works if it is the right protection factor, fit tested and worn against a clean-shaven seal.

How often does LEV have to be tested?

Local exhaust ventilation must be thoroughly examined and tested at least once every 14 months under regulation 9 of COSHH, by a competent examiner, with the report kept. Some equipment requires more frequent examination.

Can you sweep up construction dust?

Dry sweeping should not be used, because it puts settled respirable dust straight back into the air. Use an M-class vacuum, or damp the area down first. Compressed air should never be used for cleaning dust off surfaces or clothing.

Is wood dust really a serious risk?

Yes. Hardwood dust is a known cause of nasal cancer, and the workplace exposure limits are 3 mg per cubic metre for hardwood and 5 mg for softwood over eight hours. Where the dusts are mixed, the hardwood limit applies to all of it.