Workers Health & Safety Centre

Members Login

Low-level, prolonged exposure to radon leading cause of lung cancer

Evidence linking prolonged exposure to low levels of radon with lung cancer highlights need for enhanced prevention measures in workplaces, public buildings, and homes. 
A recent study, published in the journal Environmental Health Perspectives, builds on prior research focused almost exclusively on high levels of radon exposure experienced by those mining uranium and other ores prior to 1960. This study, entitled Lung Cancer and Radon: Pooled Analysis of Uranium Miners Hired in 1960 or Later, involved a pooled analysis of cohort studies of lung cancer mortality among more than 57,000 uranium miners in Canada, Czech Republic, France, Germany, and the United States. The results found the relative rate of lung cancer increased in a linear fashion with prolonged exposure to low levels of radon.
“Mining operations today tend to involve lower exposures than in the past, but our study shows that these lower exposures still increase a person’s lung cancer risk,” says Dr. David B. Richardson, lead author and professor of environmental and occupational health, University of California--Irvine. “Reducing radon exposure in our workplaces and homes remains an important way to reduce lung cancer.”

Workers and public at risk

Radon is an odourless, invisible, tasteless gas formed by the radioactive breakdown of uranium naturally found in rock and soil. When this gas escapes from the ground into outdoor air it dissipates to levels too low to be a health concern. However, when radon concentrates in enclosed spaces like underground mines, it can become a risk to health.
Radon can also enter and concentrate in buildings and homes. In these built environments, air and other gases, including radon, is drawn inside through cracks in foundations, construction joints, gaps around pipes and windows, sump pumps and drains, or cavities inside walls. 
Inhaling radon can damage cells lining the lungs and with long-term exposure can lead to lung cancer. In fact, inhalation of radon is the number one cause of lung cancer in non-smokers. According to Health Canada, 16 per cent of lung cancer deaths are the result of exposure translating into more than 3,300 lung cancer deaths annually. Smokers exposed to radon are at an even higher risk for lung cancer.
Radon has long been recognized as a significant lung cancer risk to workers in underground mining. Though it can also be a significant risk in a wide range of other occupational settings ranging from construction sites and underground parking garages to elementary and secondary schools and public administration buildings. According to CAREX Canada, almost 200,000 Canadians in these and other workplaces are exposed, including 34,000 in Ontario.
Accumulation of radon in homes is also a public health issue. A Canada-wide survey conducted by Health Canada in 2009 to 2011 found almost seven per cent of homes tested had indoor radon concentrations above the current Canadian guideline of 200 Bq/m3 (more on this below). More recently, a study published in the journal Scientific Report in 2021 suggested average radon levels in new Canadian homes would increase by 25 per cent by 2050. This same study highlights the fact the current Canadian levels are third highest in the world.

Regulatory and policy protections lagging

The existing research supports the need for urgent policy and regulatory reform addressing radon in our workplaces, public indoor spaces, and homes.
Across Canada a patchwork of laws and guidelines currently exist to address radon. Health Canada’s Radon Guideline calls for mitigation action if the average annual radon level exceeds 200 Bq/m (Becquerels per cubic metre) in many workplaces, public buildings, and homes.  
The workplace-focused Naturally Occurring Radioactive Materials (NORM) Guidelines prepared for a Working Group of the Federal-Provincial-Territorial Radiation Protection Committees recommends the same radon reference level.  
Despite these guidelines, the current reference level under the Canada Labour Code applicable to federal government employees and federally regulated workplaces is 800 Bq/m [Occupational Health and Safety Regulations, s. 10.26(4)].
Ontario’s Occupational Health & Safety Act (OHSA) imposes a general duty on employers to protect workers including identifying and controlling exposure to physical hazards like radon. When enforcing the general duty clause, Ontario’s Ministry of Labour, Immigration, Training, and Skills Development’s Radiation Protection Service considers the NORM guidelines.
More specific requirements with respect to radon in underground mines are outlined in sections 289 to 293 of Regulation 854 (Mines and Mining Plants), made under the OHSA.
Alarmingly, the radon reference levels mentioned above are multiple times higher than the 100 Bq/mlevel recommended by the World Health Organization (WHO). And, according to WHO, the relative lifetime risk of lung cancer increases by about 16 per cent for every 100 Bq/mincrease in long-term average radon concentration. Furthermore, WHO and Health Canada are clear there is no safe level of exposure to radon
To this point, the Canadian Lung Association recommends efforts to lower your home’s radon level as much as possible, even if it’s already below 200 100 Bq/m3.

Testing and better protection needed 

Health, safety and environmental advocates, researchers, concerned citizens and many others suggest taking effective action on radon requires efforts on many fronts including:
  • establishing a system for mandatory radon testing in workplaces,
  • launching new public awareness campaign including the need to test all homes for radon levels and implement retrofit and new build mitigation solutions (e.g. sealing cracks in building foundation and walls, properly sealed sump pump, adding under-floor ventilation along with improving overall building ventilation),
  • providing financial incentives to encourage radon retrofit mitigation solutions, including a radon mitigation tax credit championed by the Canadian Environmental Law Association,
  • revising exposure limits in the Canada Occupational Health and Safety Regulation from 800 Bq/mto 200 Bq/m3,
  • develop an explicit and specified regulation for radon (in Ontario and other jurisdictions), and
  • expanding protection under Building Codes (requiring radon mitigation systems in new builds, for instance).

Furthermore, Ontario’s OHSA requires employers and supervisors to identify workplace hazards, including radon, and take every precaution reasonable for the protection of a worker. Of course, testing is an important first step.
To learn more
Lung Cancer and Radon: Pooled Analysis of Uranium Miners Hired in 1960 or Later
Rising Canadian and falling Swedish radon gas exposure as a consequence of 20th to 21st century residential build practices
Canadian Environmental Law Association
Radon Guideline (residential homes and many workplaces)
Canadian Guidelines for the Management of Naturally Occurring Radioactive Materials (NORM)
Take Action on Radon (Health Canada)
Government of Ontario: Radon in the workplace
CAREX CANADA radon profile
Radiation Safety Institute of Canada
WHO Radon and Health
More from WHSC
Radon exposure in Canadian Schools focus of new research
Occupational cancer prevention in Ontario focus of groundbreaking new report
The Workers Health & Safety Centre (WHSC) also assists workplaces through training programs and information services aimed at raising awareness about hazardous exposures, including those which can contribute to the burden of cancer such as radon, and targeting prevention in the workplace and community. In fact, WHSC is Ontario’s official occupational health and safety training centre and is approved to provide mandatory Certification Training for joint health and safety committee (JHSC) members who possess the legal authority to identify hazards and help resolve health and safety issues. Similar training is available for worker health and safety representatives in smaller workplaces who possess these same rights to participate in pursuit of safer, healthier work.
WHSC Supervisor Training helps employers and supervisors meet and exceed awareness and competency requirements critical to their significant obligation to protect workers.   

Need more information?
Additional training: Check out all WHSC programs
Contact a WHSC training services representative in your area.
Connect with and follow us on TwitterFacebookLinkedInInstagram and YouTube.