Hazard summary

Workers who manufacture, finish and install natural and manufactured stone countertops are at risk of exposure to crystalline silica. Crystalline silica occurs in nature as mineral quartz. It is found in granite, sandstone, quartzite, various other rocks and sand.

There is a growing worldwide concern that working with stone countertops and exposure to crystalline silica can rapidly lead to severe disease. This may be because of:

  • the high amount of crystalline silica in these countertops
  • lack of proper controls in workplaces where this exposure occurs

Airborne silica dust particles can become trapped in the lungs resulting in permanent damage (silicosis). Carex Canada has reported that workers exposed to silica may also be at increased risk for other diseases such as lung cancer, chronic obstructive pulmonary disease (COPD), and kidney disease.

Exposure can occur at the:

  • manufacturing facility
  • 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.

Employers must assess workplace exposures to ensure workers are not exposed above the occupational exposure limit for crystalline silica. Where required, employers must develop a control program that includes:

  • engineering controls
  • work practices
  • hygiene practices and facilities
  • air monitoring
  • record keeping
  • medical surveillance
  • training for workers on the care, use and limitations of respirators

Read Ontario Regulation 490/09 – Designated Substances for more information.


At a construction project, constructors must:

  • ensure workers are not exposed above the occupational exposure limit for crystalline silica
  • develop and implement a respirator program
  • ensure workers installing or making alterations to stone countertops are provided with – and use – the right respirator if it is not possible to provide proper natural or mechanical ventilation

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

Related requirements


An industrial establishment must have enough ventilation so that the air quality is not a danger to workers’ health and safety under section 127 of Regulation 851 – Industrial Establishments.


Under section 130 of Regulation 851 – Industrial Establishments if a worker may be exposed to a biological, chemical or physical agent that could endanger their safety, they must be trained to:

  • take precautions and follow proper procedures when handling, using and storing equipment
  • use and care for personal protective equipment
  • use emergency measures and procedures


Employers and supervisors must make sure workers have everything they need to work safely while manufacturing, finishing and installing countertops containing crystalline silica.

To help protect workers, as an employer:

  • consider substituting silica with a less hazardous substance
  • make sure workers are aware of the hazards of crystalline silica
  • minimize dust exposure by using local exhaust ventilation
  • train workers on safe work practices and using respirators
  • ensure equipment is maintained (including cleaning or replacing HEPA filters)
  • implement thorough housekeeping procedures to control dust (wet methods, HEPA – filtered vacuuming)

Contact us

If you need more information about safety requirements please contact the Ministry of Labour, Training and Skills Development Health & Safety Contact Centre at 1-877-202-0008 on Monday to Friday, from 8:30 a.m. to 5:00 p.m., or webohs@ontario.ca.

This resource does not replace the Occupational Health and Safety Act (OHSA) and its regulations, and it should not be used as or considered legal advice. Health and safety inspectors apply the law based on the facts in the workplace.