Keeping it clean

Respirable crystalline silica dust kills. Exposure to it can be reduced with dust extraction or using water-guzzling machinery, which has its own environmental impact. NSS explores some of the issues of dust and water in masonry workshops

In spite of being targeted by the Health & Safety Executive in 2006 when new, lower dust exposure limits came into force, the stone industry is still far from providing ideal protection against respirable crystalline silica for the people working in it.

As the reports on court cases in the November and December issues of this magazine last year illustrate, masons are still working in atmospheres containing much more than the legal workplace exposure limit of 0.1mg of respirable crystalline silica (RCS) in a cubic metre of air – and all stone contains silica, although sandstone (and quartz composites) are more than 70% silica while limestones and marble are usually less than 2%. Granite typically has around 30%.

One of the companies prosecuted last year faced fines and costs of nearly £12,000, the other of more than £13,000. And there is a bill currently going through Parliament that will enable magistrates to impose fines of up to £20,000 (the current limit is £5,000) and, for the first time, impose prison sentences on directors for health & safety offences. It should come into force next year.

In one of last year’s cases the company had failed to report to the HSE a diagnosed case of silicosis that was so bad the man subsequently had a lung transplant.

As an industrial disease there is a legal requirement for companies to report all cases of silicosis. (See the information panel below for ways of doing so).

And fines are only the tip of the iceberg. When HSE discover infringements of exposure limits they can close a business down until the problem is rectified. And there can be claims for hundreds of thousands of pounds in compensation by those affected with the disease.

Although compensation should be covered by insurance, Phil Smith, who now has responsibility for the stone industry at the HSE, says the increase in insurance premiums following a claim is likely to be painful.

He cites a case where compensation of just £500 awarded to a person whose arm was burnt on a space heater resulted in the company’s insurance premiums doubling to £25,000.

There should be no excuse now for companies to be unaware of the dangers of RCS or their responsibility to protect their masons from it. If you are still unsure, the information panel on the left provides some sources of information.

There may be a cavalier attitude towards the dangers of dust from some masons themselves – there are, after all, those who have worked in the industry for decades without apparently suffering the ill effects of RCS. But it is rather like smoking – you only meet the ones who survive.

According to estimates used by HSE, at the old exposure limit of 0.3mg of RCS in a cubic metre of air over an eight-hour day, one in every five (20%) of those exposed for 15 years will develop silicosis. At the new 0.1mg exposure level that is reduced to one in every 40 (2.5%).

That is still too high for HSE, who are now pushing for exposure limits to be reduced to 0.05mg, when the number of silicosis cases would be reduced to one in 200 (0.5%), or possibly fewer as some argue that RCS becomes increasingly less toxic at low levels.

The underlying message is simple, though: don’t expose people to dust. And that relates not just to dust while working, but also when cleaning clothes and work areas afterwards, when emptying dust collected, and from contamination of the surrounding environment in which other people are working.

It is all very well if a person using an angle grinder, for example, has personal protective equipment (PPE), but if the dust is still going into the atmosphere, colleagues, possibly even those in a nearby office, could be affected by the RCS equivalent of passive smoking.

And, as with cigarettes, it is not the easily visible pollution that is the main problem. Large particles of dust will be prevented from reaching the lungs by the body’s own defence systems. It is the particles of around 5microns that cause the problems because they can reach the lungs and stay there.

Everyone selling dust control systems to the stone industry reports that interest in them is high and many are being sold. Yet the Silica Baseline Survey by the HSE, the results of which are due to be published shortly, identifies the significant exposure risks in stone workshops. It suggests that even where dust extraction systems have been installed masons can still be exposed to levels of RCS above the legal limit because not enough care is taken over the use of elements such as dust capture hoods and the positioning of work in front of water walls (see John Holmes’ Expert Advice on the previous page).

There can also be problems of systems being installed that are inadequate for the amount of work they are required to do. Because expenditure on dust extraction does not increase productivity it can be a reluctant purchase and companies try to minimise the cost of it.

Because the nature of stone working means that masons are likely to be exposed to at least some RCS, it is sensible for companies to have their masons medically examined regularly. And because there can be claims for compensation, it is also sensible to have masons who have worked for other companies checked before employing them to see if they exhibit any symptoms of lung disease.

It can be time consuming keeping up with health & safety regulations and putting systems in place to safeguard the company against prosecution and compensation. But there is help available from occupational hygienists. You can find one close to you using the British Occupational Hygiene Society website (see the information panel on the previous page).

Stephen Barnes of Oak Environmental Solutions ( is one such occupational hygienist. He is happy to carry out exposure monitoring for RCS, but says it is often not necessary in the first instance. “You can often go to a site and see there’s a problem. You don’t need to test for it.”

He says once improvements have been made the tests can be carried out to prove the systems are working properly.

A day’s visit from an occupational hygienist and a subsequent report is likely to cost about £1,500, so, says Stephen, it would be sensible for a company not to treat RCS in isolation from other health & safety issues such as vibration and noise.

Leila Kirk of Workforce First ( is another occupational hygienist. She says she set herself up in business specifically to help small businesses because small business does not mean small risk. “It’s trying to get people to understand the risk,” she says. “With silica you get scars on the lungs. It’s like asbestos. It can take 20 years to show up.”

She says the first thing she would ask stonemasons is if they could change any dry processing over to wet processing so that less dust is produced to be left hanging in the air.

The HSE has warned masonry companies to be aware that wet processing is not the answer to all ills as crystalline silica particles can be carried in the aerosol sprays produced by wet processing. Nevertheless, it is a good start.

One way of avoiding exposure to RCS is to remove people from the work area and let machines take over the processing. It is a direction a lot of companies have taken over the past few years, albeit to achieve productivity improvements rather than in the pursuit of health & safety improvements.

That, of course, leads to another environmental concern – water. And if The Sun was concerned earlier this month about Starbucks pouring 25million litres of water a day down the sink with the continuously running taps in the dipper wells of their 10,000 outlets worldwide, how much more concerned might they be about the 100million or so litres the stone industry in the UK alone uses each day to run CNC workcentres, saws and polishers of various kinds.

Of course, there are not many people in the stone industry these days who are just pouring used water down the drains – it’s too expensive and the Environment Agency tends to disapprove of untreated water entering the sewers.

On the other hand, there are fewer people all the time who have enough space and time simply to wait for gravity to clean used water in settlement tanks, not to mention the disruption and expense of cleaning the sludge out every few months.

Investment in new, water-guzzling machinery is often accompanied by investment in water recycling equipment at the same time.

With a CNC workcentre typically using around 80litres of water a minute, a 450 or 500mm bridge saw anywhere from 30litres a minute to 60, and a multi-headed edge polisher more than 100litres a minute, the volume of water needing to be filtered and recycled can quickly mount up. And as companies are likely to continue to invest in machinery in the future, it probably makes sense in most cases to choose a recycling system that allows for future expansion.

There are water recycling systems that simply filter the water, others that include presses and still more that separate solids out using flocculants. They all have their protagonists and their detractors, so it’s a question of listening to the arguments and deciding what is best for you. A useful first step might be to carry out a water audit to find out how much water is being used where.

Recycling is not the complete answer, because unless it filters down to better than 600microns there could be problems with using the filtered water down the central spindle of a CNC workcentre. Masons who have found wear increasing 60-70% when they use recycled water have tended to revert to using fresh water.

Joe Rotherham, who has a lot of CNC equipment in his factory in Yorkshire (see the previous issue of NSS), reckons the £20,000 he has spent on getting the required permissions and sinking a bore hole at his factory will be recovered in just two years.

Other companies are collecting rain water from their roofs, and not always just for use with machinery but also for flushing toilets, cleaning up the yard and washing vehicles.

The Environment Agency would like to see more companies cutting down on their use of water and finding alternative sources. Advice is available from the Environment Agency and NetRegs, a partnership between the UK environmental regulators that provides free environmental guidance for small and medium-sized businesses throughout the UK.


Information panel

  • Reporting industrial diseases such as Silicosis and Hand Arm Vibration Syndrome (white finger) to the Health & Safety Executive (HSE) is a legal requirement. HSE make it easy to report cases by filling in a form on-line at or by telephoning a hotline on 0845 300 9923.
  • There is plenty of information about respirable crystalline silica on the HSE website at, where the drop-down menu under the heading of ‘Your Industry’ includes a section for stonemasons. Click on ‘Local Exhaust Ventilation Systems’ for guidance on the design and installation of dust extraction systems. You can use the ‘Search’ facility on the website to find HSG201, Control of Dust for Stonemasons, although It is currently being updated and the existing version still refers to the previous exposure limit of 0.3mg/m3.
  • Further information on best practice for controlling dust and health surveillance of people exposed to it is available on the European Network on Silica website,
  • Qualified occupational hygienists can help with setting up systems and monitoring dust exposure. To find a hygienist near to you visit the website of the British Occupational Hygiene Society at
  • More on saving water on and


Expert advice by Jon Holmes, Health & Safety Manager of Pisani

Dust is everywhere. It’s something we can’t avoid in our everyday lives. To most people it’s just a minor irritation. But to stonemasons it can be an extremely serious hazard.

The very nature of stonemasonry means that dust will be produced. And, depending on the material being crafted, a proportion of that dust will contain crystalline silica of a particle size that will be respirable – ie it will pass through the body’s normal defence systems and reach the lungs.

Once the Respirable Crystalline Silica (RCS) reaches the deepest parts of the lungs it can cause scarring and hardening of the lung linings which, in turn, decreases the lung’s ability to pass oxygen into the body and absorb moisture from the body.

This can lead to a condition called silicosis, and then to pneumonia, chronic obstructive pulmonary disorder, or cancer. All these conditions are severely disabling and can lead to premature death.

Under the COSHH (Control of Substances Hazardous to Health) regulations, suitable control measures must be used to eliminate or control the amount of RCS employees are exposed to.

Elimination is always the first option. However, stonemasons work with stone and stone contains silica.

Reduction (ie use stone with lower proportion of RCS) and isolation (segregated areas or contained booths) are both sometimes impractical for various reasons, so the main option is usually to control the exposure.

This can be done in a variety of ways using all sorts of equipment. The extent of the control measures required will depend on individual circumstances, so there is never a ‘one size fits all’ approach. Equipment available varies from on-tool extraction to really quite extensive (and expensive) extraction systems. Dust booths, waterwalls, downdraught tables and capture hoods all fall in the mid range.

On-tool extraction is effective as it extracts close to the source. But it can sometimes be cumbersome or awkward, which usually means the employee removes it.

Dust booths are useful as they extract dust from a small work area where the employee is free to move about. However, the dust plume must be directed in the direction of the capture area.

Downdraught tables are also useful and provide a work bench, although dust produced on top of the workpiece may not be effectively captured and will be in the breathing zone.

Capture hoods (usually part of a larger extraction system) are extremely effective when used 30-60cm from the workpiece but do rely on constant re-adjustment or moving the workpiece to ensure the dust plume is directed correctly. Again, this is sometimes seen as a bind and is not always carried out fastidiously.

It’s important that the control measure selected is right for the job and that it is used properly, maintained and regularly inspected.

Chances are that no one piece of equipment will solve your dust problems on its own, but all have their merits and drawbacks and should be used as part of your overall control strategy.

Although it’s possible to control the levels of dust so exposure is below the 0.1mg/m3 limit, it is highly likely that some sort of respiratory protection equipment (a mask) will also be required to ensure employees are protected.


HSE guidance on local exhaust ventilation (LEV) dust extraction

Duties of employers

  • Ensure appropriate system is installed with commissioning data, instruction manual and log book
  • Schedule daily / weekly / monthly checks and log
  • Train employees in correct working procedures with the LEV and keep training records
  • Arrange annual statutory examination of system by a competent person
  • Immediately remedy any faults or failures identified, or stop production, or provide alternative protection against dust

Duties of employees

  • Make daily / weekly / monthly checks
  • Follow correct working procedures
  • Report faults
  • Identify problems

Duties of examiners

  • Provide evidence of competency
  • Compare test data with commissioning data
  • Critically examine the capture area for evidence of degree of control
  • Identify capture points that are failing and label as failed with a red sticker
  • Make recommendations for improvements as applicable


admereWEST offer booth technology

A company new to the stone industry, Staffordshire-based AdmereWEST, believe the best way of dealing with dust extraction is with dust booths.

AdmereWEST are sole European distributors for Americans MicroAir Inc. They say their CABs (Clean Air Booths) offer the correct air flow rates and capture velocities to protect both masons working in them and the surrounding environment.

With air both blown and sucked through the chamber a flow rate of 1-1.8m/sec is achieved. Dust cannot leave the booth and there is sufficient capacity to pull the dust into the filter system, which is self cleaning to maintain efficiency.

AdmereWEST believe this dust extraction product, coupled with their breathing protection products, provides the optimum safety for stonemasons.

The CAB system has a modular construction so that it can accommodate more than one mason and be tailored to fit the needs of any company.

AdmereWEST, with roots going back to 1974, are extensively involved in the metal working sectors. They were recently approached to look at a stonemasonry application. The company’s Russell Godden says the dust patterns showed few differences and as a result four installations have now been successfully supplied into stonemasons.

He says AdmereWEST offer a new concept of air scrubbing and filter cleaning with forced air flow patterns that offer the best protection and safety for both operators and bystanders within stonemasonry.

He concedes that with an application like the one pictured here costing about £18,000, this is not a cheap alternative. But, he says: “Booths are definitely the way forward.” Tel: 08700 346 226

Tel: 01229 480800

Tel: 08700 346 226

Combined Masonry Supplies
Tel: 01274 730100

Tel: 01388 605363

AJ Lopez & Co
Tel: 0208 544 9980

National Masonry
Tel: 01388 488900

New Stone Age
Tel: 01535 647222

Tel:01629 823481

The Waters Group
Tel: 0845 658 5758