09 May Silica Dust Hazards

Silica Dust Hazards

Crystalline silica is a naturally occurring mineral found in materials such as sand, stone, concrete, mortar, brick, block, and granite. When these materials are cut, drilled, ground, crushed, demolished, or otherwise disturbed, they can generate extremely small particles known as respirable crystalline silica.

These particles are small enough to travel deep into the lungs. Repeated or high-level exposure can cause silicosis, an incurable lung disease, and is also associated with lung cancer, chronic obstructive pulmonary disease (COPD), and kidney disease.

Guide for Discussion

Activities That May Generate Silica Dust

Construction and industrial activities that can create respirable crystalline silica include:

• Cutting, sawing, or grinding concrete, brick, block, stone, or tile.
• Drilling or coring concrete and masonry.
• Jackhammering or chipping concrete.
• Crushing or handling rock and stone.
• Tuckpointing and mortar removal.
• Demolishing concrete or masonry structures.
• Mixing or handling dry materials containing crystalline silica.
• Abrasive blasting using silica-containing materials or blasting surfaces that contain silica.

Do not assume that a small amount of visible dust means the exposure is safe. The respirable particles of greatest concern may be too small to see.

Control Dust at the Source

The preferred method of protection is to prevent silica dust from becoming airborne.

Depending on the task, controls may include:

• Using water-delivery systems to suppress dust at the point where it is generated.
• Using tools equipped with commercially available shrouds and dust-collection systems.
• Using HEPA-filtered vacuum systems where appropriate.
• Maintaining dust-control equipment according to manufacturer instructions.
• Positioning employees away from dust-generating operations when possible.
• Restricting access to areas where significant silica exposure may occur.
• Following the company’s written exposure-control procedures.

For construction activities covered by OSHA’s silica standard, required engineering and work-practice controls must be followed. OSHA’s permissible exposure limit (PEL) for respirable crystalline silica is 50 micrograms per cubic meter of air (50 µg/m³) as an 8-hour time-weighted average, with an action level of 25 µg/m³.

Respiratory Protection

Respirators may be required when engineering and work-practice controls cannot adequately control exposure or when specified for a particular task.

When respiratory protection is required:

• Use the type of respirator specified by the silica exposure assessment, applicable OSHA requirements, or established task controls.
• Employees must be medically evaluated, fit tested, and trained as required by the company’s Respiratory Protection Program.
• Inspect respirators before use.
• Use only approved respirators and filters appropriate for the hazard.
• Facial hair or other conditions must not interfere with the respirator’s sealing surface.

Respirators are not a substitute for required engineering and work-practice controls.

Abrasive Blasting

Abrasive blasting can create extremely high concentrations of respirable dust from both the blasting media and the material being blasted.

• Use less hazardous blasting media whenever feasible.
• Evaluate both the blasting abrasive and the surface being blasted for silica and other hazardous substances.
• Use appropriate containment and ventilation.
• Restrict access to the blasting area.
• Wear the respiratory protection and other PPE required for the operation.
• Use a Type CE abrasive-blasting respirator when required for abrasive-blasting operations.

Blasting may also expose employees to lead, cadmium, chromium, or other hazardous substances depending on the coating or surface being removed.

Housekeeping

Improper cleanup can put settled silica dust back into the air.

Do not dry sweep or dry brush silica-containing dust when those methods could increase employee exposure unless wet sweeping, HEPA-filtered vacuuming, or other exposure-minimizing methods are not feasible.

Compressed air must not be used to clean clothing or surfaces where it could contribute to silica exposure unless the compressed air is used with a ventilation system that effectively captures the dust cloud or no alternative method is feasible.

Use:

• HEPA-filtered vacuums.
• Wet sweeping or other wet-cleaning methods.
• Other approved methods that minimize airborne dust.

Personal Hygiene

Good hygiene practices help prevent unnecessary exposure and the transfer of silica dust to vehicles, homes, and other locations.

• Wash hands and face before eating, drinking, smoking, or leaving the work area.
• Do not eat, drink, smoke, or use tobacco products in areas contaminated with silica dust.
• Keep contaminated clothing separate from clean clothing.
• Change into clean clothing when appropriate.
• Do not use compressed air to blow silica dust from clothing.
• Follow established procedures for cleaning contaminated work clothing and PPE.

Know the Signs and Take Exposure Seriously

Silicosis may develop gradually, and employees can be exposed without immediately feeling sick. Symptoms of advanced disease can include:

• Shortness of breath
• Persistent cough
• Fatigue
• Chest discomfort

The absence of symptoms does not mean that an exposure is safe.

Employees covered by OSHA’s medical-surveillance requirements must be provided the required examinations according to the silica exposure-control program.

Remember

The best protection from respirable crystalline silica is to keep the dust out of the air and out of your lungs.

Recognize tasks that generate silica dust, use required water or dust-collection systems, follow established work practices, wear required respiratory protection, and never create additional exposure through improper cleanup methods.