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Crystalline silica

Quartz is the most common form of crystalline silica. Quartz is found in brick, mortar, plain pavement, concrete, rock and granite. Activities such as demolishing, crushing, drilling, sawing, grinding, sanding and sweeping materials containing crystalline silica expose workers to its dust.

Exposure to crystalline silica dust can cause respiratory disorders ranging from shortness of breath on exertion to severe respiratory failure, which are symptoms of silicosis. It can also lead to asthma, emphysema, silicosis, lung cancer and death, among others. The employer is responsible for implementing measures to control crystalline silica emissions at source. Where necessary, they must also put a respiratory protection program in place and train workers on the wearing, maintenance and storage of respiratory protective equipment.

For their part, workers must wear respiratory protective equipment, in addition to having a means of control at source, for zero tolerance activities. Respiratory protective equipment must be as stipulated in the Guide des appareils de protection respiratoire utilisés au Québec. It must be selected, adjusted, used and cared for in accordance with CSA Standard Z94.4-93, “Selection, Use and Care of Respirators”.

Safety rules

 Zero tolerance 

If any of these rules are not followed, the CNESST will stop the work and those at fault will be liable to criminal prosecution.

zero tolerance sheet: Crystalline silica

To reduce exposure to crystalline silica dust, the employer must provide workers with appropriate respiratory protective equipment and make sure they wear it.

Activities targeted by this rule

Targeted activities are activities known to expose workers to higher than standard concentrations of respirable crystalline silica. They include activities such as sawing, jackhammering, drilling, grinding, sanding, roughening, abrasive blasting, polishing, manual chipping and cutting. Specific requirements apply during abrasive blasting work.

Other mandatory preventive measures

Depending on the tasks to be performed, one or more of the following measures must be taken by the employer to control the risks associated with crystalline silica:

  • implement measures to ensure that crystalline silica emissions are controlled at source. For example:
  • develop and implement a respiratory protection program and train workers on the wearing, care and storage of respiratory protective equipment
  • train and inform workers on the risks associated with exposure to crystalline silica and on the use of means to control silica emissions
  • make sure that the equipment used to prevent the emission of silica dust is in working order and operating optimally during operating hours
  • inspect mechanical ventilation systems at least once a year
  • ensure proper maintenance of the premises by limiting dust
  • replace silica-containing materials where possible

Protective measures