Silica DustHealth and Safety Advice for Stonemasons Stonemasonry Department 2012
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.
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 yearsafter initial exposure. The main symptom is breathlessness. In severe cases death canensue. 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 HazardsPeople who experienceexceptionally high exposuresover a few months or yearscan develop acute silicosiswhich is a rapidly progressiveand often fatal condition.Exposures of 1.5mgm³ on adaily basis for a year or twoare sufficient to cause thisdisease. Death can occurwithin 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
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
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).
Protection Measures Before you consider implementing any measures to protect against inhalation ofRCS you should carry out an assessment ofpotential 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
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.
PPE and RPEPersonal Protective Equipment (PPE) andRespiratory Protective Equipment (RPE) shouldbe considered as a last resort when reducingexposure to RCS. It should also however beconsidered an essential aspect of protectingoperatives who are exposed to RCS on a dailybasis. Common forms of PPE and RPE are:Overalls – washed daily to reduce build-up ofRCSRespirators – half mask, disposable or full hood
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
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 Department City of Glasgow College 2012