Last reviewed 20 August 2014

Justin Tyas examines a case of a stonemason who was exposed to high levels of silica dust while working at a school.

A stonemason was employed by a private school for nearly 12 years. The 200-year-old school required extensive repairs for wind and weather-proofing. A further two stonemasons were employed later to assist with a major project to build a new four-storey sixth-form building. The 21-month project required more than 400 tonnes of sandstone, and the stonemasons spent their time working intensively with powered hand tools, cutting, shaping, chiselling and finishing the sandstone. Two of the stonemasons regularly worked in one of the school workshops that had no windows and no way of extracting the sandstone dust.

No measures were undertaken to control or monitor exposure to respirable crystalline silica (RCS). The original stonemason was diagnosed with silicosis, a potentially life-threatening lung disease, four months before being made redundant by the school.

The stonemason has suffered serious and irreversible health effects as a result of his exposure. He has a reduced lung function, suffers from breathlessness and can no longer continue in his profession.


Silica is a natural substance that is found in most rocks, sand and clay, as well as in some building products such as bricks and concrete. When these types of materials are subjected to mechanical processes, such as cutting, carving or sanding, they produce dust particles of different sizes. Those particles that are breathed in through the nose and mouth are referred to as “inhalable dust”. Particles that are small enough to penetrate deep into the lungs are called “respirable dust”. Respirable dust is too fine to be seen with normal lighting. RCS, or “free silica”, is fine enough to be breathed deep into the lungs, and this can cause ill health and disease.

The amount of silica contained in stones and other materials varies considerably. The stone in this case — sandstone — typically contains 70–90% silica; granite contains about 30% silica, while limestone and marble typically contain about 2% silica.

Occupational exposure to RCS can occur in many industries, including:

  • construction and demolition

  • quarrying

  • slate mining and processing

  • concrete manufacture

  • pottery and ceramic industries

  • stonemasonry.

Typical activities that produce dusts containing RCS include:

  • grinding, cutting, drilling, sanding, chiselling, blasting

  • rock drilling, breaking, crushing and screening

  • fettling

  • polishing.

The Health and Safety Executive (HSE) notes that stonemasons run a higher risk of developing silicosis, a type of pneumoconiosis caused by breathing in RCS, with silicosis death rates for stonemasons 43 times greater than the average for the total UK working population. Exposure to RCS can also cause lung cancer and chronic obstructive pulmonary disease, which is an umbrella term for a number of lung diseases.

Statutory requirements

The Control of Substances Hazardous to Health Regulations 2002 (COSHH), as amended, require employers to control exposure to RCS and other materials hazardous to health.

The main duties under the COSHH regulations are summarised below. Employers are usually required “so far as is reasonably practicable” to protect employers and others from hazardous substances.

  • Regulation 6 — assessment of risks to heath of created by work involving substances hazardous to health.

  • Regulation 7 — prevention/control exposure of substances hazardous to health:

    • by following good occupational hygiene practice to achieve adequate control of exposure, such as workplace and process changes, ventilation (exhaust and general), personal protective equipment (PPE), and work methods

    • for RCS, control measures must be effective in keeping exposure as low as reasonably practicable below the Workplace Exposure Limit (WEL) (0.1mg/m respirable dust, averaged over 8 hours).

  • Regulations 8 and 9 — use of control measures and maintenance, examination and testing of control measures.

  • Regulation 10 — monitoring exposure at the workplace.

  • Regulation 11 — health surveillance (where appropriate) of employees. This could include health and working history questionnaires, lung function tests, and chest x-rays. Specialist advice may be required.

  • Regulation 12 — information, instruction and training for persons who may be exposed to substances hazardous to health.

  • Regulation 13 — arrangements for dealing with accidents, incidents and emergencies.


The school was fined £100,000 and ordered to pay £31,547.78 in prosecution costs after pleading guilty to breaching s.2(1) of the Health and Safety at Work, etc Act 1974 (HSWA) by failing to ensure the health and safety of its employees.

Section 2(1) of HSWA states: “It shall be the duty of every employer to ensure, so far as is reasonably practicable, the health, safety and welfare at work of all his employees.”


An investigation by the HSE found that the stonemasons may have been exposed to more than 80 times the workplace exposure limit (WEL) for silica dust. There was no attempt by the school to assess and manage the risks to its workers from exposure to silica dust, despite having its attention drawn to the risks by its own safety consultant some years before the stonemason was diagnosed with silicosis. It failed to take any action to monitor exposure levels, even after the stonemason had been diagnosed, until its two remaining stonemasons were made redundant.

The school failed to recognise the risks from exposure to silica dust. No equipment was provided to remove, capture or supress the dust that was created from the actions of the stonemasons’ tools on the sandstone. There were no windows in the stonemasons’ workshop, so the general ventilation would have been inferior. The stonemasons had been working adjacent to a joinery workshop that had been fitted with an extraction system: this would have been a far more suitable place to work. The stonemason who developed silicosis asked for conditions in the workshop to be improved, but reported that his request was “brushed off”.

There was also no attempt by the school to implement health surveillance, even after the first stonemason was diagnosed with silicosis.

Lessons learned

The risks to stonemasons from working with materials containing silica are well known. In addition, there is plenty of suitable guidance (see below) to assist employers in preventing or adequately controlling exposure to RCS. The school employed stonemasons for 12 years but failed to take any action to control the exposure to their employees from high levels of silica dust in that time.

Excessive inhalation of any type of respirable dust can cause disease and ill health, but some forms of dust are more harmful than others. An employer’s first priority is to try to prevent exposure to hazardous materials, and where this is not possible or practicable to do so, then they need to adequately control exposure. Control measures need to be practical, workable and sustainable in the long term. Silicosis is irreversible, can be fatal, and leads to an increased chance of other major diseases. The risks from silica dust must be taken seriously, and must be adequately controlled to protect workers from excessive occupational exposure.