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Ontario Cancer Facts

Workplace Crystalline Silica Exposure Causes 200 Lung Cancers Annually (Special Edition)

Oct 2017


  • Workplace exposure to crystalline silica leads to approximately 200 diagnosed lung cancers each year in Ontario.
  • Reducing exposure to crystalline silica will reduce the burden of occupational cancers.
  • Regulation is needed to systemically and effectively protect all workers from silica exposure.


Each year in Ontario, it is estimated that approximately 200 cases of lung cancer are caused by exposure to crystalline silica in workplaces. These cancers amount to 2.5% of all lung cancers diagnosed each year in the province, and can be prevented with exposure reduction controls and regulations to protect workers. Silica is the second leading cause of occupational lung cancer after asbestos, and the fourth most common cause of occupational cancer in Ontario.

200 lung cancer cases: AF=2.5%

Data source: *The burden estimates are part of the Burden of Occupational Cancer Study, funded by the Canadian Cancer Society, which seeks to estimate the number of work-related cancers in Canada. For more information about the project, visit the Occupational Cancer Research Centre.
The attributable fraction (AF) is the percent of all lung cancers that are attributed to occupational crystalline silica exposure.

Industry breakdown of total lung cancers from occupational crystalline silica exposure, Ontario, 2011*
Industry Percent (%)
Construction 51
Manufacturing 28
Mining 13
Other industries 8

Crystalline silica has been classified as a human lung carcinogen by the International Agency for Research on Cancer. Silica is a common mineral that can be found in soil, sand and rocks. Silica is used for a number of purposes, including as an abrasive, insulator and filler, but it is also present in dusts that are produced in a variety of industries. Lung cancer can develop when someone inhales fine crystalline silica dusts deep into their lungs. The most common non-cancer health effect associated with silica is silicosis, an incurable condition that causes lung tissue to scar, thicken and stiffen. Other health effects include autoimmune and chronic kidney disease, as well as chronic obstructive pulmonary disease.

CAREX Canada estimates that approximately 142,000 workers are exposed to crystalline silica in Ontario. Exposure to silica occurs during activities that release fine silica dusts, such as grinding, cutting, drilling or chipping. The 3 industry sectors that contribute to the majority of silica-related lung cancer cases are construction, manufacturing and mining. The occupations with the greatest burden of lung cancer from occupational silica exposure are tradespersons and helpers (where the bulk of exposure occurs), construction labourers, and machine and heavy equipment operators (e.g., operators of excavators or bulldozers).

Policies and regulations can help foster systemic workplace health and safety changes. One regulation that could be amended to reduce the burden of silica-related lung cancer is Ontario’s Designated Substances Regulation (O. Reg. 490/09). This regulation includes substances known to be particularly hazardous to the health and safety of workers, and outlines special provisions for reducing exposure to these substances.

However, construction project employers and workers are currently exempt from the Designated Substances Regulation. This means that even though silica is listed as a designated substance, the special provisions for silica do not apply to construction workers. Given how common and widespread silica is on construction projects, amending the Designated Substances Regulation to include construction workers is expected to significantly reduce occupational silica exposure. This policy recommendation, and others, are discussed in more detail in the Burden of Occupational Cancer in Ontario: Major Workplace Carcinogens and Prevention of Exposure report.