Silica (Hazards & Controls)

1. S I L I C A
HAZARDS
&
CONTROLS

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

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

4. 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
SILICOSIS
HIGH RISK JOBS

5. 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.
Where’s it come from?

6. Crystalline Silica
• Quartz
• Cristobalite
• Tridymite

7. What Are Dusts?
• Solid particles suspended in air
• Generated by blasting, drilling,
crushing, grinding, etc.

8. 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)

9. 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
• it is present in high enough
concentrations
bronchiole
alveoli

10. 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

11. Silicosis : Severity of Disease
• Depends on:
Dust Concentration
Percent of free silica
Duration of exposure
Size of particles (respirable??)

12. Chronic Silicosis
• Most common form
• Occurs after 20 - 45 years of exposure
• Inhaled dust causes scarring
• After years of exposure - massive
fibrosis (scarring)

13. Accelerated Silicosis
• Develops 5 - 10 years after start
of exposure
•May lead to massive
fibrosis and death

14. Acute Silicosis
• Occurs where silica concentrations
are very high
• Can cause symptoms within a few
weeks to 4 or 5 years
•Rapidly FATAL

15. WARNING!!
Even when affected workers
are removed from exposure,
silicosis may continue to
progress

16. Development of Silicosis is:
• More Likely With:
• Inadequate dust control measures
• Inadequate respiratory protection
• Lack of medical screening
• Lack of air monitoring

17. 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

18. Mine Operators Must
Report
• Silicosis cases for which award of
compensation or medical
diagnosis is received by miner

19. Evaluate Worker Exposures By:
• Doing work area inspections
• Sampling, monitoring workers
• Observing work practices

20. •Monitoring: Personal Exposures

21. PEL = 10 mg / m
3
% Quartz + 2
PERMISSIBLE EXPOSURE LIMIT
(PEL)

22. 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)