Based on updated research, Canada has since reduced its target to 200 Bq/m3; Evict Radon has determined 1 in 6 Canadian homes exceed this number. Canada’s reference level differs from those suggested by the United States (US) and the World Health Organization (WHO). Why are the thresholds different and at what level does your chance of getting lung cancer actually increase?

The US has set its reference level for indoor radon concentrations at 148 Bq/m3. That might seem like an oddly precise number and it is—when working with Bq/m3 units. The US measures radon in a different unit of measurement than Canada and the rest of the world: the picocurie (pCi). One pCi/L is equal to 37 Bq/m3. In 1988, Congress passed the Indoor Radon Abatement Act, which determined the target level for indoor concentrations of radon should equal that of US outdoor concentrations (0.4 pCi/L). Unfortunately, this target was not tenable; two-thirds of homes exceed that level. As a result, the US Environmental Protection Agency determined a more practicable actionable level to be 4 pCi/L (148 Bq/m3). 

The WHO has set its reference level for indoor radon concentrations at 100 Bq/m3. Unfortunately, this target is not feasible worldwide; in countries where this level is not attainable due to “prevailing country-specific conditions,” the WHO recommends a maximum level of
300 Bq/m3. According to the WHO, the risk of getting lung cancer increases by approximately 16 per cent for every 100 Bq/m3 increase in long-term radon exposure. 

While Canada, the US, and the WHO may not have the same actionable target levels, they all agree on one thing: no level of radon exposure is safe, and indoor concentration levels should be reduced as much as possible.Ready to test your home for radon? Become a citizen scientist and order your Evict Radon test kit today by clicking the yellow “Purchase my test” button at the top of the page.



“Radon: What You Need to Know.” Government of Canada, 7 May 2019, 1 May 2021.

“Safe Radon Levels. Is there such a thing?”Air Chek, Inc., 1 May 2021.

“WHO calls for tighter standards on indoor radon.” World Health Organization, 1 May 2021.