Silicosis PreventionSilicosis Prevention

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What is Silica?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 Why Control Crystalline Silica Exposure?Exposure?

1. Toxicity is well documented

2. Exposure control is feasible

3. Widespread worker overexposure

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Potential for Silica Potential for Silica Exposure: WidespreadExposure: Widespread

Foundries

Ceramics Industry

Abrasive Blasting

Masonry/ConcreteConstruction

Manufacturing of cleaning agents

Mining Operations

Use of Coal (e.g., electric power generation)

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Hawk’s Nest Tunnel Hawk’s Nest Tunnel (Historical Example)(Historical Example)

Gauley Mt., W. VA.

1930 – 1935

Miners at Site: – Approx. 800

Estimated Deaths:– 500 to 750

Examples of Silica Exposures Examples of Silica Exposures in Constructionin Construction

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TuckpointingTuckpointing

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Silica and MortalitySilica 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 EffectsHealth Effects

Chronic-Obstructive Lung Disease

Affects Aveolar Surface–Decreases Elasticity

–Prevents Oxygen/Carbon Dioxide Exchange

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3 Classes of Silicosis3 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 DiagnosisSilicosis Diagnosis

Made by Chest X-ray

X-ray must be read by qualified “B-Reader”

Silica Nodules are Non-Reversible

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Silicosis is not a Curable Silicosis is not a Curable DiseaseDisease

Prevention through Safe Workpractice is critical

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Silicosis Prevention ProgramSilicosis 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 ProgramSilicosis Prevention Program

Air monitoring program

Medical surveillance

Housekeeping and Regulated Areas

Recordkeeping

Controls for SilicaControls for Silica

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Types of Engineering ControlsTypes of Engineering Controls

1. Wet Methods

2. Ventilated Tools

3. Abrasive Blasting Controls:– Alternate Media– Alternate Processes

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Engineering Controls:Engineering Controls:1. Wet Methods1. Wet Methods

Water suppression of dust

Very effective method

Requires supply of water and clean up

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Wet Methods: Joint CuttingWet Methods: Joint Cutting

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Wet Methods: Portable SawWet Methods: Portable Saw

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Wet Methods: Pre-planningWet Methods: Pre-planning

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Prohibit Dry Cutting !Prohibit Dry Cutting !

8 X OSHA PEL – Time Weighted

Average (TWA)

Cut approx. 20 blocks per shift

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Mason’s Water PumpMason’s Water Pump

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Wet Methods: Block CuttingWet Methods: Block Cutting

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Wet Methods: Jack hammer, Wet Methods: Jack hammer, chipping hammer, etc.chipping hammer, etc.

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Engineering ControlEngineering Control2. Ventilation2. 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 Control by Ventilation: Slab CuttingCutting

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Control by Ventilation: Hand Control by Ventilation: Hand toolstools

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Control by Ventilation: Control by Ventilation: TuckpointingTuckpointing

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Control by Ventilation: Control by Ventilation: TuckpointingTuckpointing

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Engineering Controls: Engineering Controls: 3. Substitute Abrasives3. 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 SystemsBlast and Recovery Systems

Permits multiple cycles of abrasive

Reduces cost of more expensive abrasives

Reduces fugitive emissions to Environment