Radon Survey of Workplaces in Ontario


This project investigates the levels of radon in a variety of Ontario workplaces, including public buildings and small to medium sized businesses. The main objective of this study is to collect data to assess where hazardous levels of radon are present in Ontario workplaces in order to target prevention efforts.

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Radon is a naturally-occurring radioactive gas formed by the breakdown of uranium in soil, rock and water. It is invisible and detected only by radon measurement devices and can accumulate to high levels in enclosed spaces. Radon is responsible for approximately 13% of lung cancer deaths in Ontario and is the second leading cause of lung cancer after smoking. The World Health Organization recommends that radon exposure remain below 100 Bq/m3, while the Health Canada Guideline is 200 Bq/m3.

Radon testing in workplaces has been inconsistent across Canada. A Health Canada study of radon in federal buildings found that approximately 3.8% of the buildings had average radon concentrations above the Health Canada Guideline. In Quebec, radon testing in schools found that 17% of the schools tested above the Guideline. In British Columbia, a study that tested for radon in schools, daycares, hospitals and long-term care facilities and caves was published in 2009. Other than in Uranium mines, research on radon exposure in Ontario workplaces has been very limited. While radon testing was completed in the late 1990s in Ontario fish hatcheries, these results are now outdated and no other large-scale study of radon in workplaces in the province has been undertaken.


Ontario Health Regions with low and high background radon levels were identified using results from the residential Cross-Canada Survey of Radon. Radon samples will be collected in public buildings and small to medium sized businesses in six Health Regions with high background levels of radon. Additional samples will be collected in workplaces with potentially high radon risk (e.g. underground workplaces) in four Health Regions with low background levels of radon. In particular, samples will be collected from: Brantford, Chatham-Kent, Windsor, Toronto, Guelph, Elliot Lake, Sudbury, Ottawa, Kingston, and Woodstock. The total number of workplaces involved in this study will be dependent on workplace participation. Furthermore, the total number of samples collected per workplace will depend on workplace size as some workplaces housed in larger rooms of buildings may require the deployment of multiple measurement devices. In total, it is hoped that at least 800 radon measurements in approximately 500 workplaces will be collected.

Radon monitoring kits will be deployed for 3 months over the winter months, which is when radon levels are expected to be the highest. Results will be analyzed to identify potentially high hazard areas and to model radon levels in workplaces across Ontario. The data will also be used to produce radon maps. Workplaces with elevated levels will be provided with free educational materials and connected with remediation and mitigation informational resources.


This research will help fill crucial gaps in knowledge by generating new data on radon exposures and identifying regions in Ontario where levels of radon are elevated in the workplace. The results from the study can be used to identify groups of workers who may be at increased risk of lung cancer due to radon exposure, and to target prevention efforts in regions with the greatest potential for improvements in occupational health and safety. The research project will also increase radon awareness and health and safety knowledge among workers. The study’s findings may be further used by governments and health professionals to help prioritize radon outreach and education efforts, and to encourage workplace testing and remediation where necessary.

Progress (updated January 2024)

Recruitment is now complete and all deployed radon monitors have been retrieved. Thank you to all who participated!


This study is funded by a grant from the Ontario Ministry of Labour, Training and Skills Development’s Research Opportunities Program:

Demers PA, Boksman L, McIntosh T, Nicol AM. Radon Survey of Workplaces in Ontario. 2017-2019.

For more information

If you would like more information on the study, please contact Lily Yang (

Research Team
Paul A Demers
OCRC and University of Toronto
Laura Boksman
Radiation Safety Institute of Canada
Anne-Marie Nicol
CAREX Canada, Simon Fraser University
Lily Yang
Tammy Khuc
Carmel Hilal
Prathna Patel