Health surveillance for those exposed to respirable crystalline silica (RCS)
The HSE have recently released updated guidance on health surveillance for workers exposed to silica dust that can be breathed in. This is known as respirable crystalline silica or RCS. RCS can lead to a number of health problems including silicosis and chronic obstructive pulmonary disease (COPD). Silica exposure is also linked to lung cancer.
Whilst silicosis was previously a serious problem, improved workplace conditions has seen the condition mainly disappear. However, many workers are still exposed to RCS and whilst most exposures tend to be below the Workplace Exposure Level or WEL there is still a risk of health problems particularly if exposed to RCS over many years.
The new HSE guidance requires employers to make their own assessment if employees might be exposed to RCS and if necessary to carry out health surveillance which may include a chest x-ray. A chest x-ray can detect the first stages of silicosis before it affects breathing or causes symptoms so it is a useful test.
What is respirable crystalline silica (RCS)?
Crystalline silica is a natural substance found in stone, rocks, sand and clay, as well as products like bricks, tiles, concrete and some plastic composites. When these materials are worked on, for example by cutting or drilling, the crystalline silica is released as a very fine dust which can be breathed in. This dust is one of the oldest workplace hazards – and it still causes hundreds of thousands of deaths across the world every year.
Silica dust is only harmful when it’s inhaled deep into your lungs, where oxygen is taken up into the blood. Sitting on a sandy beach won’t cause any respiratory harm because any sand particles breathed in will generally be much too big to go beyond your nose or upper airways. But as a very fine airborne dust, silica can be dangerous. It’s the respirable fraction that is hazardous. Respirable particles are typically less than around 5 micrometers in size. Compare this to the full stop at the end of the sentence, which is around 200–300 micrometers in diameter, and the finest sand on that beach, which is about 50–70 micrometers. Individual silica dust particles are so small that they are invisible to the naked eye in normal light – so you can have relatively high airborne concentrations without being aware that the dust is being inhaled.
The main focus in workplaces in developed countries is on the risk of lung cancer from exposure to respirable crystalline silica, although silicosis and other lung diseases are also a concern where control measures are poor.
WHO IS AFFECTED?
Exposure to silica dust occurs in many industries. Common scenarios where people may be exposed include:
• Breaking, crushing, grinding or milling silica-containing material such as concrete, aggregate or mortar
• Drilling, cutting, chiselling or sanding silica-containing material
• Dealing with cement
• Moving earth, e.g. excavating, mining, quarrying or tunnelling
• Abrasive blasting or sandblasting
• Laying, maintaining or replacing ballast
• Handling, mixing or shovelling dry materials that include silica
• Using silica, sand or silica-containing products in the manufacturing process of glass and other non-metallic mineral products
• Using sand as a moulding medium in foundries
• Using silica flour (a finely ground form of crystalline silica)
• Dry sweeping up after a task where silica dust has been created
Main Risk Employment Areas
• Abrasive blasting
• Brick, concrete or tile manufacturing
• Cement finishing
• Ceramics manufacturing
• Coke and other fuel manufacturing
• Cutting or grinding silica-containing material
• Drilling silica containing material
• Glass manufacturing
• Metals and machinery manufacturing
• Mining and quarrying
• Steel manufacturing
• Trades that use or fit plastic composite products
WHAT YOU NEED TO DO
The main aim should be to stop silica dust getting into the air in the first place.
You may be able to select a process that avoids or cuts down the dust being released, for example, taking into account silica dust control at the design stage of a construction project by planning buildings with pre-built recesses for plumbing, gas and electric wiring so there’s less need to cut or drill masonry and concrete, or getting materials cut to size off-site in a facility where it’s easier to control dust exposure.
Try to remove or substitute materials containing crystalline silica from the work process – it may be possible to use a different material, for example substituting olivine or another safer material for silica sand in abrasive blasting.
If it’s not possible to protect operatives from silica dust at the design stage or by changing processes or materials, then your first step is to monitor or assess the exposure and identify the jobs and tasks that need better controls. A survey by the UK’s Health and Safety Laboratory shows that when employers do this they are more likely to put in appropriate controls.
Select from a range of options available to control exposure to silica dust at work:
The most important thing is that if your workers might be exposed to RCS you must carry out exposure monitoring. This will determine whether you need to take any action to control exposures and whether you need to do any health surveillance.
In a factory or workshop environment, the best strategy is to use engineering controls like enclosures or hoods and local exhaust ventilation to extract the contaminated air at the point it’s produced, or to use water suppression on fixed machinery.
Where work with hand-held power tools generates dust, for example on construction sites, the best strategies are to use localised ventilation on the tool or suppress the dust using water spray systems.
When you buy or rent new equipment, make sure the controls are appropriate. High-value plant and equipment, for example the rock-drilling machines used in tunnelling or the crushing equipment operating at recycling plants, are now likely to have dust suppression integrated into the design. Small items may not have these controls as standard, although you can often buy an add-on control sleeve to extract the dust.
In all situations, if it’s not possible to adequately control airborne silica dust using engineering solutions, and air sampling data shows that there is still an unacceptable level of dust, then operatives should use personal respiratory protection.
As well as getting all the relevant controls in place, and checking that they’re working properly in practice, you should give people who could be at risk from silica dust exposure information about the possible risks and how exposure can be cut down. And you need to instruct or train affected employees too, including on how to use the control measures in place to protect them.
Respiratory protection is generally considered the ‘last resort’, and health and safety legislation in the UK positions it in that way. But the reality is that respirators are often necessary to achieve adequate control, either because of the difficulty of controlling exposure using another method, or because it would be impractical and costly to use engineering controls in some circumstances. In addition, respirators are often a very effective way of reducing exposure. For high-risk tasks, you shouldn’t rely on respiratory protection alone – it may not give enough protection, it only protects the person wearing it, and people make mistakes with masks, for example wearing them at the wrong time or for too long.
Who should be included in the health surveillance programme?
Based on the HSE guidance and the scientific literature, our recommendation is that you should consider health surveillance for anyone who is exposed to RCS where this can be detected through exposure monitoring even when this is below the WEL which is 0.1 mg/m3 of RCS. Even at 10% of the WEL, research suggests that there is a 2% chance of developing silicosis over a lifetime working at this exposure level.
Health surveillance for silicosis should be considered for workers who are involved in high-risk occupations, including construction, foundry work, brick and tile work, ceramics, slate, manufacturing, quarries and stonework. Where workers are regularly exposed to RCS dust and there is a reasonable likelihood that silicosis may develop, health surveillance must be provided.
Where employees are exposed to RCS they should at least have annual health surveillance including a health questionnaire and a lung function (spirometry) test which could help detect chronic obstructive pulmonary disease or silicosis. In some cases, it may be appropriate for the employee to have a chest x-ray.
If you require any occupational health advice or would like to discuss setting up a Health Surveillance programme, please contact firstname.lastname@example.org
For more information on RCS, please download the following documents from the HSE website: