What is silica & how does respirable crystalline silica arise?

Silica is a natural substance found in most rocks, sand and clay and products made from these materials, such as bricks and concrete. In the workplace (including construction sites) these materials create dust when they are cut, drill, sanded, polished, etc. Preparation of concrete floors, such as through bead blasting or shot blasting may lead to substantial quantities of airborne respirable crystalline silica. Some of this dust may be fine enough to reach deep inside the lung, this is known as respirable crystalline silica (RCS) and can cause harm to health. Significant exposure to respirable crystalline silica can cause silicosis and lung cancer.

Exposure levels for respirable crystalline silica

Respirable crystalline silica has a workplace exposure limit (WEL), which contains exposure below a set limit, preventing excessive exposure.

The WEL for RCS is 0.1 mg per cubic metre, expressed as an 8-hour time-weighted average (TWA).

How to control exposure to respirable crystalline silica

The starting point for controlling worker exposure to respirable crystalline silica is a COSHH Assessment. As a substance hazardous to health,  respirable crystalline silica is covered by the COSHH Regulations.

Stop or reduce the dust – Before work starts, look at ways of stopping or reducing the amount of dust you might make. Use different materials, less powerful tools or other work methods. By way of eaxamples, you could use:

• the right size of building materials so less cutting or preparation is needed;
• silica-free abrasives to reduce the risks when blasting
• a less powerful tool – eg a block splitter instead of a cut-off saw
• a different method of work altogether – eg a direct fastening system.

Stop the dust getting into the air – Even if you stop some dust this way, you may do other work that could still produce high dust levels. In these cases, the most important action is to stop the dust getting into the air. There are two main ways of doing this:

• Water – water damps down dust clouds. However, it needs to be used correctly. This means enough water supplied at the right levels for the whole time that the work is being done. Just wetting the material beforehand does not work.
• On-tool extraction – removes dust as it is being produced. It is a type of local exhaust ventilation (LEV) system that fits directly onto the tool. This ‘system’ consists of several individual parts – the tool, capturing hood, extraction unit and tubing. Use an extraction unit to the correct specification (ie H (High) M (Medium) or L (Low) Class filter unit). Don’t just use a general commercial vacuum.

Respiratory protective equipment (RPE) – Water or on-tool extraction may not always be appropriate or they might not reduce exposure enough. Often RPE has to be provided as well. In this case, you should ensure that the RPE is:

• adequate for the amount and type of dust – RPE has an assigned protection factor (APF) which shows how much protection it gives the wearer. The general level for construction dust is an APF of 20. This means the wearer only breathes one twentieth of the amount of dust in the air
• suitable for the work – disposable masks or half masks can become uncomfortable to wear for long periods. Powered RPE helps minimise this. Consider it when people are working for more than an hour without a break
• compatible with other items of protective equipment
• fits the user. Face fit testing is needed for tight fitting masks
• worn correctly. Anyone using tight-fitting masks also needs to be clean shaven.

RPE is the last line of protection – If you are just relying on RPE you need to be able to justify your reasons for this.

Other controls – Depending upon the work you are doing you may have to combine these measures with other controls. consider the following:

• limiting the number of people near the work
• rotating those doing the task
• enclosing the work to stop dust escaping. Use sheeting or temporary screens
• general mechanical ventilation to remove dusty air from the work area (eg in enclosed spaces such as indoors)
• selecting work clothes that do not keep hold of the dust

You must also ensure that workers are doing the job in the right way and that they are using controls properly. You should train workers:

• about dust risks and how this can harm their health
• how to use the dust controls and check that they are working
• how to maintain and clean equipment
• how to use and look after RPE and other personal protective equipment (PPE)
• what to do if something goes wrong

RCS and Construction Cancer Risk, and other ill health arising from exposure to respirable crystalline silica

Exposure to respirable crystalline silica can lead to a range of lung diseases:

• Silicosis: Silicosis makes breathing more difficult and increases the risk of lung infections. Silicosis usually follows exposure to RCS over many years, but extremely high exposures can lead rapidly to ill health. Silicosis causes small hard nodules of scar tissue to develop in the lungs that are seen on a chestX-ray. Silicosis usually takes some years to develop. There is also an acute form of silicosis that occurs at very high exposures. This can start within a short time and can kill within a few months of first exposure.The main symptoms are a cough and difficulty in breathing. Workers with silicosis are at increased risk of tuberculosis and lung cancer and may also develop kidney disease and arthritis and related diseases.

• Chronic obstructive pulmonary disease (COPD): COPD is a group of lung diseases, including bronchitis and emphysema, resulting in severe breathlessness, prolonged coughing and chronic disability. It may be caused by breathing in any fine dusts, including RCS. It can be very disabling and is a leading cause of death. COPD interferes with air movement in and out of the lungs and causes breathlessness, often with a chronic cough and sputum (phlegm). Smoking cigarette can make the situation worse.

• Lung cancer: Heavy and prolonged exposure to RCS can cause lung cancer. When someone already has silicosis, there is an increased risk of lung cancer.

Lancashire boarding school has been fined £100,000 after a stonemason exposed to silica dust

A historic private school in Clitheroe has been fined £100,000 over health and safety failings after one of its stonemasons developed a potentially fatal lung disease. Stonyhurst College has been fined after a stonemason developed an incurable lung disease following work to undertake repairs of the 200-year-old buildings, he was diagnosed with silicosis in 2011 from silica dust found in stones. According to the HSE, he may have been exposed to silica dust more than 80 times the daily limit. The school admitted a Health and Safety breach and said it was “remorseful”.

As its buildings needed repairs for wind and weather proofing, Stonyhurst College had employed the 55-year-old worker from June 1999. According to the HSE, he was diagnosed with silicosis in July 2011,  four months before being made redundant by the school. During that period, a couple of other stonemasons were employed to help build a new four-storey, sixth form building. It is understood that the project required more than 400 tonnes of sandstone and the stonemasons worked with powered hand tools cutting, shaping, chiselling and finishing the sandstone.

The HSE investigation found that Stonyhurst College failed to monitor or reduce the exposure to silica dust, despite sandstone containing between 70% and 90% of those particles. The stonemason with silicosis has suffered severe and irreversible health effects as a result of his exposure. He has a reduced lung function, suffers from breathlessness and can no longer continue with his profession.

Stonyhurst College was fined £100,000 and ordered to pay over £31,500 in costs.

After the trial, HSE Inspector Mike Mullen said:

There was no attempt by the college to assess and manage its workers’ exposure despite having their attention drawn to the risks by its own health and safety consultant in 2008.

A worker who was previously very active now struggles to play outside with his grandchildren, and will suffer breathing difficulties for the rest of his life.