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A Calculated Risk: Radon Exposure in Indoor Environments

Dr. Jing Chen is a Health Canada scientist who’s come up with an innovative way to calculate Canadians’ risk of exposure to radon according to where we spend most of our time. Radon is an odourless, colourless radioactive gas produced by the natural decay of uranium in soil and rock. By understanding where we are exposed to radon indoors, we can target reduction strategies that will have the most impact.

“Radon is radioactive gas that comes from the ground, it is around us almost everywhere in varying concentration,” Dr. Chen explains. “There is sufficient evidence indicating that radon is the second leading cause of lung cancer, after tobacco smoking. Even though it is invisible and odourless, there are simple ways to test for it, and simple techniques to reduce its concentration in the air we breathe.”

Radon poses a risk to human health when it accumulates in closed, indoor environments, so Dr. Chen reviewed the radon levels found in over 7,866 homes, 1,132 school buildings, and 1,668 public buildings across Canada to calculate Canadians’ radon exposure. On average, Canadian homes were found to have radon levels twice as high as school buildings and almost three times as high as public buildings.

Next, Dr. Chen used data generated by Statistics Canada on how much time Canadians spend indoors at home, indoors away from home, outdoors, and in vehicles, according to their age. Cross referencing this data with radon levels found in homes, schools, and other buildings away from home produced a time-activity data set showing Canadians’ risk of radon exposure, broken down by age. This means that Canadians who spend the highest proportion of their time at home, such as infants and seniors, are at a higher risk of radon exposure.

“The result on risk distribution did surprise me,” Dr. Chen said. “Due to relatively higher radon concentration in homes and longer time spent indoors at home, the exposure at home contributes to 90% of the radon-induced lung-cancer risk.”

The good news is that it is easy to test the radon levels in your home and to take action to reduce it. Dr. Chen tested her home for radon in 2005, and even though the amount of radon she found was half the amount that is harmful to human health (200 Bq/m3), she still sealed gaps she found in her basement to further reduce the amount of radon that would otherwise accumulate.

“We spend much more time at home than in any other indoor environment. Since most of Canadians’ radon exposure is in the home, it is important to test our homes for radon and take action as necessary,” urged Dr. Chen.

For more information on radon, how to test for it, and how to reduce it in your home, please visit

To read Dr. Chen’s study, visit: (seulement disponible en anglais).

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