Silicosis Prevention

What is Silica?
 Composes 15% of Earth’s Crust
 Examples:
– Sand, Granite, other “Hard” rocks
 Quartz, most common
 Crystalline Silica
– has a diagnostic X-ray diffraction pattern
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Why Control Crystalline Silica
Exposure?
 1. Toxicity is well documented
 2. Exposure control is feasible
 3. Widespread worker overexposure
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 Foundries  Manufacturing of cleaning agents
 Ceramics Industry
 Mining Operations
 Abrasive Blasting
 Masonry/Concrete
Construction
 Use of Coal (e.g., electric power generation)
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Hawk’s Nest Tunnel
(Historical Example)
 Gauley Mt., W. VA.
 1930 – 1935
 Miners at Site:
– Approx. 800
 Estimated Deaths:
– 500 to 750
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Examples of Silica Exposures in Construction
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Tuckpointing
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Silica and Mortality
 250 Worker deaths per year
– (175 deaths/yr from trenching accidents)
 Silicosis
 Tuberculosis
 Heart Disease
 Lung Cancer?
– Suspect Hum. Carcinogen –A2 (ACGIH)
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Health Effects
 Chronic-Obstructive Lung
Disease
 Affects Aveolar Surface
– Decreases Elasticity
– Prevents Oxygen/Carbon Dioxide
Exchange
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3 Classes of Silicosis
 1. Acute Silicosis (Highest Exp.)
– Latency of weeks to 5 years
 2. Accelerated Silicosis (High Exp.)
– Latency of 5 to 15 years
 3. Chronic Silicosis (Moderate Exp.)
– Latency >15 years
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Silicosis Diagnosis
 Made by Chest X-ray
 Xray must be read by qualified “B-
Reader”
 Silica Nodules are Non-Reversible
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Silicosis is not a Curable
Disease
 Prevention through Safe
Workpractice is critical
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Silicosis Prevention Program
 Engineering Control of Dust
 Training on crystalline silica
 Respiratory protection program
 Work clothes, change and wash area
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Silicosis Prevention Program
 Air monitoring program
 Medical surveillance
 Housekeeping and Regulated Areas
 Recordkeeping
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Controls for Silica

Types of Engineering Controls
 1. Wet Methods
 2. Ventilated Tools
 3. Abrasive Blasting Controls:
– Alternate Media
– Alternate Processes
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Engineering Controls:
1. Wet Methods
 Water suppression of dust
 Very effective method
 Requires supply of water and clean up
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Wet Methods: Joint Cutting
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Wet Methods: Portable Saw
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Wet Methods: Pre-planning
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Prohibit Dry Cutting !
 8 X OSHA PEL
– Time Weighted
Average (TWA)
 Cut approx. 20 blocks per shift
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Mason’s Water Pump
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Wet Methods: Block Cutting
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Wet Methods: Jack hammer, chipping hammer, etc.
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Engineering Control
2. Ventilation
 Portable tools with dust exhaust:
– Surface Grinders
– Disc Grinders (tuck pointing)
– Crack chaser
– Scarifier
– Descaler
– Power chipping tools
 Retrofit Dust hoods
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Control by Ventilation: Slab
Cutting
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Control by Ventilation: Hand tools
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Control by Ventilation:
Tuckpointing
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Control by Ventilation:
Tuckpointing
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Engineering Controls:
3. Substitute Abrasives
 Coal slag (“black beauty”)
 Steel grit & steel shot
 Aluminum oxide
 Sodium Bicarbonate
– (baking soda)
 Dust Suppressed Sand
 Frozen CO2
 Ag. Prod. (walnut shells, corn cobs)
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Blast and Recovery Systems
 Permits multiple cycles of abrasive
 Reduces cost of more expensive abrasives
 Reduces fugitive emissions to
Environment
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