Exposure to Respirable Crystalline Silica (RCS) – Who is at risk? Part 1


In the next 6 articles, Morag McWilliam takes a look at employees’ exposure to Respirable Crystalline Silica and who might be at risk. Morag details what employers must do to manage the health risks, control measures which should be applied, exposure limits, the use and maintenance of Local Exhaust Ventilation (LEV) systems, health surveillance, exposure monitoring and training.   

In their document ‘Health and safety at work – Summary statistics for Great Britain, 2022’* the UK’s Health and Safety Executive (HSE) gives the following stark statistics:

  • 13,000 deaths each year are estimated to be linked to past exposure at work, primarily to dust and chemicals.
  • Occupational lung diseases account for 12,000 of these deaths.
  • On average during the past three years, there have been an estimated 19,000 new cases of respiratory problems caused or made worse by work each year.

To put these figures into perspective, an average double-decker bus holds approximately 100 passengers, and the average passenger plane that takes us on holiday holds around 400 passengers…….Just imagine 120 busloads or 30 planeloads of passengers losing their lives every year, because of exposure to something which is often man-made and always preventable.

Silica is just one substance associated with lung diseases.


Silica is a naturally occurring substance found in stone, rocks, sand and clay.

It is a major component of many construction materials including bricks, tiles, concrete and some plastic composites.

Silica is found in two forms – a crystalline form which includes quartz and cristobalite and the so-called ‘amorphous’ form which includes diatomaceous earth and silica gel.

The amount of crystalline silica contained in materials varies greatly. Examples of approximate crystalline silica content of some materials commonly used in industry are given in the table below.

Material Approximate crystalline silica content of different materials (% w/w)
Sandstone, gritstone, quartzite. Above 70%
Mortar, concrete. 25 – 70%
Shale. 40 – 60%
China stone. Up to 50%
Granite. 20 – 45%
Slate. 20 – 40%
Ironstone. Up to 15%
Basalt, dolerite. Up to 5%
Limestone, chalk Up to 5%
Marble. Up to 5 % (Can contain veins of crystalline silica, so actual content may be much higher).



Crystalline silica is at its most toxic when it is freshly fractured through processes such as cutting, drilling or polishing.

During these and other processes where high energy is applied to the crystalline silica, a very fine dust is released which can be breathed in. This dust is known as Respirable Crystalline Silica (RCS), and it is so fine that once breathed in, it can reach the deep lung where it remains.

RCS particles are not visible to the naked eye in normal light, so high concentrations can be inhaled without a person being aware of it.

The respirable particles are typically less than around 5 micrometres in size. Compare this to the full stop at the end of this sentence, which is around 200–300 micrometres in diameter, and the finest sand on a beach, which is about 50–70 micrometres.

Exposure to RCS over an extended period can cause serious, irreversible long-term health effects, beginning with fibrosis (hardening or scarring) of the lung tissue with a consequent loss of lung function.

Sufferers are likely to have severe shortness of breath and may find it difficult or impossible to walk even short distances or upstairs. The effect continues to develop after exposure has stopped and is irreversible. Sufferers usually become house- or bed-bound and often die prematurely due to heart failure.

Acute silicosis is a rare complication of short-term exposure to very large amounts of RCS. This condition is life-threatening and associated with very significant clinical consequences.

Silica may also be linked to lung cancer. Precautions taken to control the risk of fibrosis will also control the risk of lung cancer. Workers with silicosis are at an increased risk of tuberculosis, kidney disease and arthritis. Exposure to RCS may also cause chronic obstructive pulmonary diseases (COPD) such as emphysema.

RCS dust is also abrasive and drying when in contact with the skin and can give rise to contact dermatitis.

Lung disease case study:


  • Common workplace activities where people may be exposed to RCS include:
  • Breaking, crushing, grinding or milling silica-containing material such as concrete, aggregate or mortar.
  • Drilling, cutting, chiselling or sanding silica-containing material.
  • Working with cement.
  • Moving earth, e.g., excavating, mining, quarrying or tunnelling.
  • Abrasive blasting or sandblasting.
  • Handling, mixing or shovelling dry materials that contain 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) for example as an abrasive additive to polishes and cleaning products.
  • Working with natural and artificial/engineered stone e.g. Stonemasonry activities or kitchen worktop manufacture.
  • Dry sweeping up after a task where silica dust has been created.
  • Contamination of clothing with dust containing silica.
  • People or vehicular movement causing accumulated dust to be raised from the ground.

*Health and Safety at Work – Summary statistics for Great Britain 2022.

Health and Safety Executive, 2022.

This is the first in a series of articles of raising awareness of the dangers of RCS. The next article focuses on what employers must do to manage the health risks associated with exposure to RCS to ensure that your people and businesses are protected. If you would like to talk further please email [email protected].

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