Silica DustHealth and Safety Advice

Respirable Crystalline SilicaCrystalline 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.

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.

Health Hazards

False-colour x-ray of the chest area of a person suffering from silicosis. Image sourced from Science Photo Library 2011

X-ray of the chest area of a person suffering from silicosis. Image sourced from Science Photo Library 2011

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.

Health Hazards

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

Statistics

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.

1 2 3 40

0.1

0.2

0.3

0.4

0.5

0.6

Predicted risks of developing silicosis within 15 years fol-lowing exposure15 years exposure to respirable crystalline sil-ica (8 hour TWA) mg.m3

Exposure (mg.m³)

Risk (%)

0.02 0.25

0.04 0.5

0.1 2.5

0.3 20

Source: COSHH Regulations 2002 Consultative Document

Legislation

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).

Q2 2002

Q4 2002

Q2 2003

Q4 2003

Q2 2004

Q4 2004

Q2 2005

Q4 2005

Q2 2006

Q4 2006

Q2 2007

Q4 2007

Q2 2008

Q4 2008

Q2 2009

Q4 2009

Q2 2010

Q4 20100

500

1000

1500

2000

2500

Industrial Injury: Quarterly Incidence of Pneu-moconiosis Claims (UK)

Number of claims

Incidence of Pneumoconiosis Claims in UK sourced from DWP 2011

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 exposureExamination of existing controlsEffectiveness of existing controls

Existing engineering controlsUse of Respiratory Protective EquipmentMaintenance, examination and testing of

engineering controlsMonitoring

Health SurveillanceInformation, instruction and training of

employees

Source: Control of Respirable Silica in Quarries HSE 2008

Dust Control

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 spraysCollection – cyclones, scrubbers, bag fitters,Containment – encapsulation

These control measures can be used either individually or collectively.

Suppression Collection Containment

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

Maintaining RPE

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 regularlyClean hoods/respirators with approved cleaning wipes dailyEnsure batteries for powered respirators are fully chargedEnsure proper face fitting is achieved following cleaning

Image showing collection of stone dust on respirator filter

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?

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

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

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

Developed by The Stonemasonry DepartmentCity of Glasgow College

2012