Silica Exposure

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

crystalline silica

? 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

? Smoking

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.