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Respirable Crystalline Silica (RCS) Dust

Aliases: Silica Dust Crystalline Silica

RCS dust is airborne crystalline silica dust that is respirable to those in close proximity to the source.

Silica is the second most common mineral on earth. It consists of silicon and oxygen atoms which makes up nearly all of what we call "sand" and "rock". Quartz is the most common form of crystalline silica and is found in varying amounts in almost all types of rocks, sands, clays, shales and gravel. Cristobalite and tridymite are found in volcanic rocks. Crystalline silica is also a major constituent of construction materials such as bricks, tiles and concrete.

Crystalline silica is hazardous when it becomes airborne through disturbing the material through common operations such as cutting, sawing, drilling or crushing. CAREX Canada estimates that approximately 48,000 workers in BC are occupationally exposed to RCS each year. More workers in BC workplaces are exposed to RCS dust than to asbestos or lead.

In BC, the RCS dust exposure limit is 0.025 milligrams per cubic metre (mg/m3). This is a concentration to which nearly all workers could be exposed for eight hours a day, five days a week, without adverse health effects. The OHSR requires exposures be controlled below this limit.

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