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Why is Radon Dangerous?

When radiation of all types interacts with the cells in your body, it can cause damage to how the cell replicates. Usually, this makes the cell unable to replicate as the cell’s instructions are damaged. However, if the damage is done just the right way, it can cause the cell to replicate uncontrollably, becoming cancer. Typically, your body is very good at catching and dealing with these mutations, but they can go unnoticed and unchecked by the body’s natural systems, allowing the damage to worsen progressively.


Lung cancer is especially concerning as there are very few outward symptoms for the affected person or medical professionals until it’s very advanced. This, combined with the fact that Radon is colourless, odourless, and relatively undetectable without specific testing methods, means that it’s very easy not to know there is a problem until it’s too late. According to Public Health Ontario, there are about 850 deaths per year related to Radon-induced lung cancer, equivalent to over two people per day dying in the province due to this invisible cause.

Thankfully, we can all test for Radon through professional services and do-it-yourself kits that you can purchase through our website or your local hardware store.

Once you know your Radon level, you can decide whether to consider a home mitigation. As it is radiation, there is no such thing as a “safe” level as it is inherently bad. There are various thresholds that various groups suggest you take action at; all are determined by the same dose calculations, with slightly different variables used.


When discussing Radon, you will see numbers expressed in Bequerel’s (Bq/m³) or picoCuries (pCi/L). Both are a measurement of radioactivity (how often a material radioactively decays in a given volume), not the dose (how much radioactive energy is deposited in the body).

Becquerels are the standard scientific unit (SI), defined as one radioactive disintegration per second (in a cubic meter) and used everywhere but in the USA. The USA or imperial unit is the picoCurie or one trillionth of a Curie. This is 2.2 disintegrations per minute, or 0.037 disintegrations per second (in a litre, or 0.001 m³), based on how often a pound of radium emits radiation. 

The conversion between the two is 37 Bq/m³ = 1 pCi/L (pCi/L x 37 = Bq/m³). Both units are named after prominent radiation scientists, namely Henri Becquerel, who first discovered evidence of radioactivity, and Marie and Pierre Curie, who pioneered the “theory of radioactivity.” All three share the 1903 Nobel Prize in Physics.

Health Canada’s action level is 200 Bq/m³, the USA’s EPA’s action level is 150 (technically 4.8 pCi/L), and the World Health Organization’s is 100 Bq/m³. As the health risks from radiation increase exponentially, these action levels are where the various health organizations have calculated that your risk begins to increase more dramatically and, as such, where you should consider taking action.

Radon Potential Map

This map was constructed by Radon Environmental, who combined indoor Radon testing, geological surveys, soil surveys, aerial radiological flyover data, and several other datasets to be as accurate as possible. 


This map uses unusual names for its areas. Typically, one would expect such a map to use “Low,” “Medium,” and “High” as labels to describe the zones being showcased here. Unfortunately, it came to light that many people associate the term “Low” with a “Zero” likelihood of Radon being found in that area, which is not the case.


To more accurately understand this map, you have to understand the terminology being used in it since it’s not using the normal “Low-High” label that one would expect. In this case, what’s known as a Guarded zone usually has approximately one in seven homes above the Health Canada action level of 200 Bq/m³. An Elevated zone varies heavily between the Guarded and High zones as a median or middle grounding. Homes in the High zone are about 40% more likely to have Radon levels above the action level, meaning approximately one in five homes require remediation.

While Health Canada has done a cross-country survey, only a few municipalities have done more detailed surveys in their areas. Kingston, Guelph, Hamilton, and Ottawa are the municipalities we know that have done more detailed surveys that have tested at least 1 in 5 homes above 200 Bq/m³. If you are concerned about the Radon levels in your local area and would like an official survey taken, you can join us in our fight against Radon by contacting your local municipality or health unit and inquiring about this.


It is important to note here that the homes with the highest levels of Radon that we’ve mitigated have been found in the Guarded zones, with homes testing at over 10,000 Bq/m³! It’s one of the reasons for the industry phrase, “Everyone should test for Radon!”

A map of Ontario that shows the different levels of radon in different areas of Ontario
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