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Hazard summary

Workers who manufacture, finish and install natural stone and engineered stone countertops are at risk of lung disease resulting from exposure to crystalline silica. Crystalline silica occurs in nature as the mineral quartz. It is found in natural stone, such as:

  • granite
  • sandstone
  • quartzite
  • engineered stone, which is man-made from natural stone, resins and pigments

There is a growing worldwide concern that worker exposure to crystalline silica when working with stone countertops can rapidly lead to silicosis, an incurable, disabling and often fatal lung disease. Symptoms of silicosis can include shortness of breath, cough and fatigue.

The risk of developing severe silicosis is especially high for those workers who use hand-held tools to cut or grind engineered stone because of its much higher silica content (up to 95%) than many of the natural stones, such as marble and granite.

Carex Canada has reported that workers exposed to silica may also be at increased risk for other diseases such as lung cancer and chronic obstructive pulmonary disease (COPD).

Exposure can occur at the:

  • manufacturing facility
  • finishing facility (where stone is cut and customized)
  • jobsite during installation

Housekeeping and maintenance workers in workplaces where stone countertops containing crystalline silica are made may also be at risk of exposure.

Key legislative requirements

Under the Occupational Health and Safety Act, employers have general duties, including the duty to take every precaution reasonable in the circumstances to protect workers, including from exposure to hazards, such as crystalline silica.

Silica is a designated substance under the Ontario Occupational Health and Safety Act and exposures in Ontario workplaces are regulated under O. Reg. 490/09 – Designated Substances. Construction projects are exempt from O. Reg. 490/09. Exposures to silica on construction projects are regulated under, Regulation 833- Control of Exposure to Biological and Chemical Agents.

Industrial workplaces

In accordance with O. Reg. 490/09, employers must carry out an exposure assessment for silica in workplaces where both of the following occur:

  • silica is present, produced, processed, used, handled or stored
  • a worker is likely to be exposed to silica

Workers must not be exposed above the occupational exposure limit for crystalline silica.

The employer must develop a control program if the exposure assessment discloses (or would disclose if carried out in accordance with the regulation) that both:

  • a worker is likely to be exposed to silica
  • that the health of the worker may be affected by that exposure

A control program must include:

  • engineering controls
  • work practices
  • hygiene practices and facilities
  • air monitoring
  • record keeping
  • training program for workers and supervisors on the health effects of silica and the measures and procedures required under the control program
  • training for workers on the care, use and limitations of respirators
  • medical surveillance

Read Ontario Regulation 490/09 – Designated Substances and a guide to designated substances in the workplace for more information.


At a construction project, constructors and employers must:

  • ensure workers are not exposed above the occupational exposure limit for crystalline silica
  • control dust using methods, such as water spraying or providing ventilation
  • protect workers from exposure to silica without requiring them to use a respirator unless one of the conditions specified in ss. 7.2(2) of Regulation 833 applies, for example, engineering controls, such as dust control are not reasonable or practical to adopt
  • develop and implement a respiratory protection program, where respirators are provided

Read Regulation 833 – Control of Exposure to Biological or Chemical Agents and Ontario Regulation 213/91 – Construction Projects, section 46 for information.

Additional precautions

Additional precautions to protect workersinclude:

  • substituting crystalline silica with a less hazardous substance, if possible
  • automating processes to distance the worker from the source of dust
  • minimizing dust exposure by using local exhaust ventilation and water spraying systems
  • train workers on safe work practices and using respirators
  • ensuring equipment is maintained (including cleaning or replacing HEPA filters)
  • implement thorough housekeeping procedures to control dust (use wet methods, HEPA – filtered vacuuming)