radon under house


Last review/updated:  October 26, 2023

What is radon?

Radon is a naturally occurring, radioactive gas that comes from the breakdown of uranium found in rocks and soil. You can’t see, smell, or taste radon.

Radon Factsheet – 2023

What are the health effects of radon?

Breathing in high levels of radon for many years can lead to lung cancer. Smokers are at a higher risk of developing radon-related lung cancer than non-smokers. In Canada, radon is the second leading cause of lung cancer after tobacco smoke. You can read more about the health effects of radon at Canadian Lung Association.

The health risk from radon exposure is long term and often dependent on three things:

  1. the level of radon in your home,
  2. the length of time (in years) you have been exposed, and
  3. smoking habits or exposure to secondhand smoke.

Average annual doses of ionizing radiation by source (worldwide)

radiaotion by source pie chart
Source: Wild CP, Weiderpass E, Stewart BW, editors (2020). World Cancer Report: Cancer Research for Cancer Prevention. Lyon, France: International Agency for Research on Cancer. Available from: http://publications.iarc.fr/586. Licence: CC BY-NC-ND3.0 IGO.

How does radon get into my home?

Radon gas can enter buildings through cracks in the foundation, gaps around pipes, open floor drains or any other area of exposed soil. When radon mixes with the air outside, it’s not a health risk as the air outside dilutes the radon concentrations. But when radon seeps into confined spaces like a house, it can build up to high levels and become harmful. You and your family can breathe in high levels of radon without knowing.

Is there radon in my home?

Every house contains some amount of radon. The likelihood of high radon levels cannot be predicted by the age or location of a home; all homes are at risk. The only way to know how much radon is in your home is to test.

Radon Factsheet (Canadian Cancer Society, 2016)

Health Canada Radon Website

Canadian Lung Association

Canadian Cancer Society
Canadian Association of Radon Scientists and Technologists
Canadian Radiation Dose Calculator
CARex Website
Canadian Real Estate Association (CREA) – A Homeowner’s Guide to Radon

Canadian Environmental Law Association

MacHealth’s Accredited Radon Course for Health Care Professionals

Canadian Partnership For Children’s Health and Environment

Health Canada Pamphlets:

(the following pamphlets can be ordered in bulk by emailing radon@canada.ca)