Controlling Silica exposures to prevent lung disease (Respirable mine dust)
Quartz is the common form of crystalline silica. It is the second most common surface material on the Earth’s crust. The issue is airborne respirable mine dust produced by blasting, milling, cutting, crushing, shovelling, conveying, tunnelling.
The fact is respirable mine dust or respirable particulate produced at quarries or construction sites or at any earthwork where there is fugitive emission of these invisible particles. The main hazard to worker health is prolonged exposure to airborne respirable particles with a diameter that is less than 5 microns in size as these can travel to the deep tissue of the lung.
Breathe-Safe submits the following points to maintain a safe breathing zone for operators at mineral processing sites, construction sites and tunnels.
• Site management must use a multitude of controls for respirable dust within a dust management plan
• Operators with enclosed cabs can reduce their exposure tight against particulate
• To be effective the cabin/enclosure must be well sealed and ventilated (HVAC-climate control)
• Doors and windows must be closed always. All seals, windows and doors must be intact (Replace worn our seals immediately)
• Fresh air pressuriser with HEPA filters to effectively control respirable mine dust
• HEPA return air filter to capture particulate contamination from shoes and clothes
• Plan hygiene maintenance: vacuum (HEPA) cabin equipment daily/weekly in hazardous environments
An international survey demonstrated that by spending time inside the operator further reduced his exposure by up to 76 percent when compared to wet drilling alone (Zimmer, 1997). [1]
The issues surrounding the health of operators at mine/constructions/tunnels sites in Queensland has placed a large target in the control respirable dust.
To compare the diameter of a human hair is 60 microns
Particles with a diameter of less than 2.5 micron can enter the blood stream
The Queensland select committee inquiry into Coal Worker Pneumoconiosis has heard evidence that there may be no “safe limits” for respirable mine dust particles. [2]
While, there will be cases that workers may be genetically sensitive to freshly produced Silica. There has been calls for scientific research to find out the exposure level that is safe if any. [3]
Silica is a class 1 human carcinogen and by itself is 20 times more toxic than coal dust. Apart from causing Silicosis it has been linked to cause renal disease and autoimmune diseases like rheumatoid arthritis. [4]
The cost of fitting a Breathe-Safe HEPA system will in fact reduce maintenance costs over time by keeping the HVAC system free from fine dust contamination.
Breathe-Safe system components:
• Pre-cleaner (Extend the life of HEPA filter by ejecting coarse airborne particles)
• HEPA primary air filter (Efficient to control respirable mine dust)
• HEPA return air filter (Efficient at capturing contamination from shoes and clothes)
• Display / Controller with analytics (Operator awareness – Mine site remote monitoring)
The best practice is a fresh air pressuriser filtered with HEPA filter media for respirable dust with a digital display for operator to know that system is working. Other important functions are data logging and warning/alerts for operator and for site management alerts via remote monitoring.
Contact Breathe-Safe to discuss long term solutons.
[1] Zimmer (1997). Comparative evaluation of dust control technologies on percussion rock-drilling rigs. Applied Occupational and Environmental Hygiene 12(12):782-788.
[2] Dr Brian Plush, CWP public hearing transcript, 12 December 2016, pp 2-3
[3] Dr Brian Plush, CWP public hearing transcript, 12 December 2016, pp 4
[4] Dr Robert Cohen, QLD CWP public hearing, 15 March 2017, pp 20
