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Occupational Exposure Occupational
exposure to crystalline silica occurs by
breathing silica-containing dusts
present in many industries, such as:
mining and quarrying; steel, iron, and
other metal foundries; abrasive
blasting; construction; glass and
ceramics; paint and pigments; and,
quarrying and crushing stone.
Silicosis A commonly known health hazard
which has been associated historically
with the inhalation of silica-containing
dusts is silicosis. Silicosis is a fibrotic lung disease (development of
scar tissue in the lungs) which can be
progressive and disabling; it can lead
to death. It is the primary health risk
from breathing silica and the oldest
known occupational disease. To pose a
danger to the lungs, a dust particle
must be respirable. A dust particle is
considered respirable if it is smaller
than 10 micrometers, about four-ten
thousandths of an inch. Dust particles
that are respirable are capable of being
inhaled into the conducting airways and
gas exchange regions of the lungs. Dust
particles larger than 10 micrometers are
not capable of penetrating the defense
mechanisms of the lung to produce injury
to the important lower regions of the
lung where oxygen transfer takes place.
There are three different types of
silicosis. Chronic silicosis may result
from prolonged inhalation of excessive
levels of respirable silica dust, and
may take many years of exposure to
develop. A second type, accelerated
silicosis, may occur in a relatively
shorter period of time from the
inhalation of intense excessive levels
of respirable silica dust. Acute
silicosis, the third type, develops
rapidly and has been reported in
occupations such as sand blasting and
drilling through silica-containing rock.
Cases of acute silicosis and complicated
cases of chronic silicosis and
accelerated silicosis can be fatal.
The number of cases of silicosis can be
reduced by implementing measures to
reduce exposure to silica-containing
dusts. Such measures include engineering
controls, improved work practices,
training programs, and respiratory
protection programs.
Workplace Safety
Safety and health programs, policies,
and procedures should be implemented and
enforced to control silica hazards in
the workplace. These programs, policies,
and procedures must be designed to fit
the specific needs of the workplace.
In order to improve safety in the use of
industrial sand, exposure to airborne
silica-containing dusts should be kept
below the exposure limit. A program to
protect the respiratory health of
workers who use crystalline
silica-containing materials should
include:
* Warning and training workers
concerning hazards;
* Crystalline silica dust sampling;
* Engineering controls;
* Good housekeeping; and
* Medical surveillance of workers
focusing on respiratory health.
If engineering controls or
administrative procedures cannot keep
the respirable silica dust level below
the exposure limit, then respiratory
protective equipment is necessary. The
respiratory protection program should be
custom-designed for the workplace by a
qualified industrial hygienist following
a full assessment of workplace conditions.
Silica Usage
Ferrosilicon alloys are used to improve
the strength and quality of iron and
steel products. Tools, for instance, are
made of steel and ferrosilicon.
In addition to tool steels, an example
of “alloy steels,” ferrosilicon is used
in the manufacture of stainless steels,
carbon steels, and other alloy steels
(e.g., high-strength, law-alloy steels,
electrical steels, and full-alloy
steels).
An alloy steel refers to all finished
steels other than stainless and carbon
steels. Stainless steels are used when
superior corrosion resistance, hygiene,
aesthetic, and wear-resistance qualities
are needed.
Carbon steels are used extensively in
suspension bridges and other structural
support material, and in automotive
bodies, to name a few. Silicon is also
added to aluminum to create a stronger
alloy. The largest consumers of silicon
metal are the aluminum and chemical
industries.
Silicon is used in the aluminum industry
to improve cast ability and weld
ability, not to add strength as noted in
the text. Silicon-aluminum alloys tend
to have relatively law strength and
ductility, so other metals, especially
magnesium and copper, are often added to
improve strength.
In the chemicals industry, silicon metal
is the starting point for the production
of silicones, fumed silica, and
semiconductor-grade silicone the used to
make silicone resins, lubricants,
anti-foaming agents, and water-repellent
compounds. Silicones are used as
lubricants, hydraulic fluids, electrical
insulators, and moisture-proof
treatments.
Semiconductor-grade silicon is used in
the manufacture of silicon chips and
solar cells. Fumed silica is used as
filler in the cement and refractory
materials industries, as well as in heat
insulation and filling material for
synthetic rubbers, polymers and grouts.
Other silicon materials are used in the
production of advanced ceramic
materials, including silicon carbide,
silicon nitride. Silicon carbide is also
used as an abrasive material, a
refractory agent, and in steel
manufacturing.
Recommended Filled of Application
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Mica |
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Red Iron oxide |
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