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Geologic Radon Potential 

Radon arises from the breakdown of radioactive minerals in soil, such as radium, thorium and uranium. In a natural environment, radon emerging from the earth’s surface is diluted to “nothing” almost immediately.

  1. When people ‘map’ radon, the first thing to look at is the potential for radon to be generated from the sources in the soils, rocks, and water of a given area. This is called the geologic radon potential, and is often expressed as the Bq of radon generating material per kilogram (Bq/kg).
  2. It is the geological composition of top several meters of material under a given building (i.e. the ‘surficial’ geology) that matters where it comes to radon. As radon is generated, it enters soil gases or dissolves in water, and can diffuse to the surface. If this occurs outside, it will then dilute to ‘nothing’.
  3. Soil gasses are under high pressure, and will carry radon to the low pressures at the surface quickly. Radon in water is more complex, and usually only people using untreated well water will be at risk.
  4. However, just because you live in a high radon potential area does not mean that all buildings will be higher for indoor air radon, as that depends on the way those buildings capture and contain it.
What the science says:

First order estimations of radon potential are classified based on radiometric data derived from uranium and thorium content of bedrock lithology, surficial materials, groundwater, structures and anthropogenic activity.

References: Doering et al.. Modelling the dispersion of radon-222 from a landform covered by low uranium grade waste rock. J Environ Radioact 192, 498-504 (2018) and also Akerblom G. Investigations and Mapping of Radon Risk Areas. in Proceedings of the International Symposium on Geological Mapping, Trondheim 1986, in the Service of Environmental Planning 96-100 (Norges Geologiske Undersoekelse, Oslo, 1987).

Radon and the Build Environment 

Modern buildings can capture and concentrate radon to hazardous & unnaturally high levels that are not normally observed on the surface of Earth. Thus, very high radon exposure is human-made problem, and is thus very preventable.  

  1. A building over an area of geologic radon potential has the potential to have a high radon problem if it can capture and concentrate the radon to unnaturally (artificially) high levels that are hazardous to health. A building must have both factors to have high radon, as a failure to either capture or contain radon means no radon problem.
  2. Human-made buildings often operate under negative pressure at lower levels, which can actively draw radon up through foundations. You don’t have to have visible cracks in the foundation for this to take place, as radon can come up through even the normal joins between foundations and walls.
  3. Once radon is inside, it can be concentrated if the property’s air dynamics are not balanced between the amount of fresh air being brought inside (via the ‘cold air’ return) and the amount of stale air leaving the home via the roof or other vents.
What the science says: 

In a study of >10,000 people US and Canadian scientists found that the typical North American spends 93.08% of their life indoors. Thus, most of our exposures in life are a function of the indoor environment we live in.

Reference: Leech et al. It’s about time: a comparison of Canadian and American time-activity patterns. J Expo Anal Environ Epidemiol. 2002 Nov;12(6):427-32. 

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