2. Respirable Crystalline Silica
Crystalline silica is one of the most abundant minerals in the earths crust. There
are different crystalline forms of silica with the most common one being that of
quartz. Quartz is found in varying amounts in almost all types of rock, sands, clays,
shales and gravel. Sandstone is almost pure quartz whereas granite might contain
15-30% quartz.
Many common workplace activities such as cutting, drilling, grinding and polishing
produce fine dust containing respirable crystalline silica (RCS). The term
respirable means that the dust particles are small enough to enter the lungs when
they are inhaled. Your course tutor will play a video which shows how dust particles
adhere to the inner lining of the lungs, potentially causing long term damage.
3. Health Hazards
X-ray of the chest area of a person suffering from silicosis. False-colour x-ray of the chest area of a person suffering from
Image sourced from Science Photo Library 2011 silicosis. Image sourced from Science Photo Library 2011
Silicosis is a slow, progressive, irreversible disease that usually occurs many years
after initial exposure. The main symptom is breathlessness. In severe cases death can
ensue. Silicosis is diagnosed by chest X-Ray where the presence of rounded nodules of
scar tissue on the lungs is visible as white opacities. The highest risk of developing
silicosis is from exposure to dry, freshly fractured fine particles of RCS that are
generated during many common workplace tasks such as drilling, cutting, grinding,
polishing etc.
4. Health Hazards
People who experience
exceptionally high exposures
over a few months or years
can develop acute silicosis
which is a rapidly progressive
and often fatal condition.
Exposures of 1.5mgm³ on a
daily basis for a year or two
are sufficient to cause this
disease. Death can occur
within months of exposure.
Excessive particle distribution due to ineffectual local exhaust
ventilation system
Heavy and prolonged exposure to RCS under the conditions that produce silicosis
can cause lung cancer. Another common illness is Chronic Obstructive Pulmonary
Disease (COPD) which is an umbrella term that covers emphysema and chronic
bronchitis. It is characterised by impaired airflow within the lungs and is not fully
reversible. The symptoms are cough with phlegm, and/or wheezing and breathing
difficulties and can result in death.
Definitions taken from HSE Topic Inspection Pack 2006
5. Statistics
0.6
Exposure Risk (%)
0.5
(mg.m³)
0.4 Predicted risks of 0.02 0.25
developing silicosis
within 15 years following
0.3 exposure 0.04 0.5
15 years exposure to
0.2 respirable crystalline
silica (8 hour TWA)
mg.m3
0.1 2.5
0.1
0.3 20
0
1 2 3 4
Typically each year, since 2003, between 10 and 30 deaths have been recorded
with silicosis being an underlying cause. Despite many of these deaths being
avoidable, companies continue to ignore relevant guidelines. In 2007 a large
quarrying company in England was fined over £15,000 for exposing its employees
to excessive levels of RCS.
Source: COSHH Regulations 2002 Consultative Document
6. Legislation
Industrial Injury: Quarterly Incidence of
Pneumoconiosis Claims (UK)
2500
2000
1500
1000
Number of claims
500
0
Incidence of Pneumoconiosis Claims in UK sourced from DWP 2011
RCS is assigned a WEL of 0.1mg/m3 in Schedule 1 of the Control of Substances
Hazardous to Health Regulations 2002 (COSHH). In addition to the need to
control substances according to good practice, it is a legal requirement that the
WEL should not be exceeded. A WEL is defined as the concentration of a
hazardous substance in the air that people breath, averaged over a specified
reference period referred to as a time-weighted average (TWA). Two periods are
used: long-term exposure limit (LTEL) (8 hours) and short-term exposure limit
(STEL) (15 minutes).
7. Protection Measures
Before you consider implementing any
measures to protect against inhalation of
RCS you should carry out an assessment of
potential exposure. The following should be
considered in your assessment:
Potential for exposure
Examination of existing controls
Effectiveness of existing controls
Existing engineering controls
Use of Respiratory Protective Equipment
Maintenance, examination and testing of
engineering controls
Monitoring
Health Surveillance
Information, instruction and training of
employees
Source: Control of Respirable Silica in Quarries HSE 2008
8. Dust Control
Suppression Collection Containment
The focus on RCS should always be on elimination or substitution. Where this
is not possible we consider ways we can control the levels of RCS that
operatives are subjected to. The equipment and methods for dust control are
classified as:
Suppression – water, steam, mist or fog sprays
Collection – cyclones, scrubbers, bag fitters,
Containment – encapsulation
These control measures can be used either individually or collectively.
9. PPE and RPE
Personal Protective Equipment (PPE) and
Respiratory Protective Equipment (RPE) should
be considered as a last resort when reducing
exposure to RCS. It should also however be
considered an essential aspect of protecting
operatives who are exposed to RCS on a daily
basis. Common forms of PPE and RPE are:
Overalls – washed daily to reduce build-up of
RCS
Respirators – half mask, disposable or full hood
10. Maintaining RPE
Image showing collection of stone dust on respirator filter
It is essential that RPE is maintained in accordance with manufacturers guidelines.
Failure to maintain RPE will result in ineffective protection levels. You should
therefore:
Replace filters regularly
Clean hoods/respirators with approved cleaning wipes daily
Ensure batteries for powered respirators are fully charged
Ensure proper face fitting is achieved following cleaning
11. Activity
Use the information in this presentation to answer the following questions:
1. What do the letters RCS represent?
2. Identify two health hazards associated with RCS
3. What is the current WEL for RCS?
4. Identify three methods of dust control
5. What do the letters COSHH represent?
6. What do the letter RPE represent?
7. What methods are used to cure silicosis?
12. Activity Answers
1. What do the letters RCS represent?
Respirable Crystalline Silica
2. Identify two health hazards associated with RCS
Silicosis, acute silicosis, lung cancer, COPD
3. What is the current WEL for RCS?
0.1mg/m³
4. Identify three methods of dust control
Suppression, collection, containment
5. What do the letters COSHH represent?
Control of Substances Hazardous to Health
6. What do the letter RPE represent?
Respiratory Protective Equipment
7. What methods are used to cure silicosis?
There is no known cure for silicosis
13. References
HSC, (2006), Control of Substances Hazardous to Health Regulations 2002 (as
amended 2005): Proposal for a Workplace Exposure Limit for Respirable
Crystalline Silica, HSC
HSE, (2010), Stone Dust and You, HSE
HSE, (2008), Control of respirable silica in quarries, HSE
HSE, (2006), Topic Inspection Pack: Inspection Intervention in the Stonemasonry
Industry, Stonemasons: Exposure to Respirable Crystalline Silica (RCS), Disease
Reduction Programme (DRP) Respiratory Disease Project, HSE
14. Further Reading
Further information on all forms of construction related dusts can be found on the
Health and Safety Executive’s (HSE) website at:
www.hse.gov.uk
15. Developed by The Stonemasonry Department
City of Glasgow College
2012
