Transcript Occupational Exposure to Silica - Georgia Tech OSHA Consultation

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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Potential for Silica
Exposure: Widespread
 Foundries
 Ceramics
 Manufacturing
of
cleaning agents
Industry
 Mining
 Abrasive
Operations
Blasting
 Use
 Masonry/Concrete
Construction
of Coal (e.g.,
electric power
generation)
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Hawk’s Nest Tunnel
(Historical Example)
 Gauley
 1930
Mt., W. VA.
– 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
must be read by qualified “BReader”
 X-ray
 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
Training
on crystalline silica
Respiratory
Work
area
Control of Dust
protection program
clothes, change and wash
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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
Very
suppression of dust
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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