What is Silica?
Free silica exists in two main forms; amorphous silica and crystalline silica. Crystalline silica is one of the most common minerals found on the surface of the earth. It may be found in a variety of forms the most common of which is quartz. Other types of crystalline silica include tridymite and cristobalite. Amorphous silica is the term used to describe forms which have no regular crystal structure. It includes a wide range of different types of which fossilized skeletal remains of marine organisms is the most common. While there is some scientific evidence that amorphous silica may occasionally cause adverse health effects, most silica-related disease has been a result of breathing of crystalline silica.
Where are WHERE ARE WORKERS POTENTIALLY
EXPOSED TO SILICA?
Workers are possibly exposed to crystalline silica dust
in many trades and industries, including mining, tunnelling,
quarrying, masonry, metal foundries and ship and bridge
repair. Activities that can produce significant amounts of
crystalline silica include:Workers are possibly exposed
to crystalline silica dust in many trades and industries,
including mining, tunnelling, quarrying, masonry, metal
foundries and ship and bridge repair. Activities that can
produce significant amounts of crystalline silica include:
? AbiliDrilling, chipping and hammering of rock or
materials containing silica
? Blasting, crushing, loading, shovelling and dumping
of rock or materials containing crystalline silicaty
to document a job in a non-discriminatory manner;
? Abrasive blasting using crystalline silica or material
containing crystalline silica
? Demolition of materials containing crystalline silica
? Dry sweeping of materials containing crystalline silica
? Using compressed air to clean material containing
? Removal of alumino-silicate based ceramic fiber
insulation that has been subjected to high temperature
It should be noted that even materials containing silica
in small amounts can be a hazard if they are used in
ways that produce high dust levels.
WHY IS SILICA A HEALTH HAZARD?
Breathing dust containing free crystalline silica is a
potential health hazard because it may allow some of
the smaller particles of silica to deposit in the lungs.
The body tries to break down the particles to remove
them from the lung. While the body tries to remove the
particles, tissue may be damaged. The damaged tissue
forms hard inelastic scar tissue in the lungs which may
lead to a disease known as silicosis. The accumulated
dust and scar tissue form small masses that are scattered
throughout the lungs. These small masses may join
together forming large masses of scar tissue. These
scars make the lungs stiff and interfere with the transfer
of oxygen into the blood. The heart must work harder to
pump blood through the stiff lungs. This added strain
may lead to failure of the right side of the heart.
The damage to the lungs depends on:
? The type of silica inhaled
? Amount of dust inhaled
? Length of time exposed to the silica dust
? Length of time the silica was permitted to react
with the lungs
? Individual susceptibility
? Presence of pulmonary infections
? How freshly sawed, hammered or treated in a way
that produces airborne dust the silica particles are
Silicosis may be chronic, accelerated or acute.
WHAT IS CHRONIC SILICOSIS?
Chronic silicosis develops after many years of exposure.
Symptoms may not appear until 10 to 20 years, or
more, after the first exposure has occurred.