S I L I C A

HAZARDS & CONTROLS

What are the hazards associated with exposure to silica dust, as well as basic preventive and control measures

Each year more than one million miners and other workers are exposed to dangerous levels of the dust -

SILICA

SILICOSIS

HIGH RISK JOBS

DRILLERS CRUSHER OPERATORS BINSETTERS QUALITY CONTROL TECH SANDBLASTERS PLANT HELPERS MAINTENANCE PERSONNEL MOBILE EQUIP. OPERATORS (without environmental cabs) CHANGING SCREENS, BAG REPLACEMENT, BAGGING (without environmental booths) CONFINED SPACE ENTRY

Where’s it come from?

Silica (Silicon Dioxide or SiO2) is found mainly as quartz in nearly all mineral deposits. It is found in common rocks such as granite, sandstone, limestone, and is the principle component of sand.

Crystalline

Silica

• Quartz • Cristobalite • Tridymite

What Are Dusts ?

• Solid particles suspended in air • Generated by blasting, drilling, crushing, grinding, etc.

The Body Defends Against Dust By:

•

Trapping larger particles in the nasal passages, throat, trachea, larynx

•

Trapping particles in mucous and carrying them up the airways where they are coughed out or swallowed ( mucociliary escalator )

Silica dust may be a hazard, if...

• it is in the

respirable

range: small enough to get into the air sacs (

alveoli

) --- basically less than 10 microns in size

bronchiole

• it is present in high enough concentrations

alveoli

How Does Silica Affect The Body?

• Silica particles build up in the lungs leading to a type of dust disease (

pneumoconiosis

) called

silicosis

• Makes affected workers more susceptible to TB • Causes cancer

Silicosis

:

Severity of Disease

•

Depends on

:



Dust Concentration



Percent of free silica



Duration of exposure



Size of particles (respirable??)

Chronic Silicosis

•

Most common form

•

Occurs after 20 - 45 years of exposure

•

Inhaled dust causes scarring

•

After years of exposure - massive fibrosis (scarring)

Accelerated Silicosis

•

Develops 5 - 10 years after start of exposure

•

May lead to massive fibrosis and death

Acute Silicosis

•

Occurs where silica concentrations are very high

•

Can cause symptoms within a few weeks to 4 or 5 years

•

Rapidly FATAL

WARNING!!

Even when affected workers are removed from exposure, silicosis may continue to progress

Development of Silicosis is:

•

More Likely With:

•

Inadequate dust control measures

•

Inadequate respiratory protection

•

Lack of medical screening

•

Lack of air monitoring

Medical Exams Include:

• Medical and work history • Checkup to detect early signs of lung disease • Chest x-ray (reviewed by “B” reader) • Breathing test • TB examination

Mine Operators Must Report

•

Silicosis cases for which award of compensation or medical diagnosis is received by miner

Evaluate

Worker Exposures By:

•

Doing work area inspections

•

Sampling, monitoring workers

•

Observing work practices

•

Monitoring: Personal Exposures

PERMISSIBLE EXPOSURE LIMIT

(PEL)

PEL = 10 mg / m 3 % Quartz + 2

REDUCE

Silica Exposures:

• Assess potential for exposure • Use engineering controls, such as: 

Dust Collectors



Environmental cabs and booths



Water Sprays



HEPA Filters and Vacuum (Don’t cleanup with brooms/shovels)