<\/span>This is a summary of the international collaborative study between Canada and Sweden on radon incidence in buildings in these two countries. We encourage readers interested in the subject to consult the full study.<\/span><\/span><\/p>
The study focused on a large cohort of buildings, including single-family homes, semi-detached, and townhouses built from 1945 onward. The number of buildings included was 25,489 in Canada and 35,596 in Sweden.<\/span><\/p>
The comparative study of these two countries is interesting as both are northern countries. The smoking rate, which is decreasing, is similar in both countries. However, the curve of inherent radon presence in buildings varies over time, with a consistent decrease in Swedish buildings since the 1980s, while it is steadily increasing in Canada. For non-smokers, the cancer rate is currently 163% higher in Canada, a significant figure. The study found that newly built buildings tested immediately after construction show lower radon levels that increase over the following 2 to 3 years. These buildings were excluded from the study to avoid bias.<\/span><\/p>
Buildings in Sweden before 1970 had higher radon levels than those in Canada, but buildings from the 1970s to 1980s are comparable (93–103 Bq\/m³). Afterward, levels increased in Canada and decreased in Sweden. For buildings from 2010 to 2020, levels were 28 Bq\/m³ in Sweden and 131 Bq\/m³ in Canada, which is 467% higher. Several parameters were integrated into a predictive model, and multiple simulations were conducted to better understand this large dataset. Projections indicate a decrease in Sweden to levels > 15 Bq\/m³, whereas in Canada an increase to > 175 Bq\/m³ is forecasted by 2050 if no drastic changes are made in home construction methods.<\/span><\/p>
In Sweden, the significant decrease in inherent radon occurred nationwide without regional distinction. In Canada, the increase also occurred across the country, with a higher proportion in the Prairie region. The most significant reduction period in Sweden followed the implementation of air exchanger installation after 1980. In Canada, this addition has been significantly used only since 2010.<\/span><\/p>
Analysis of building codes shows that Sweden has no specific radon standards<\/span>, and building code enforcement is immediate upon publication, leading to immediate changes. In Canada, the risk is addressed by requiring the installation of a basic mitigation infrastructure. Since building codes are subject to provincial and municipal approval, a typical implementation lag of about 5 years is known. In both countries, the downward and upward trends coincide with the adoption of performance-based building codes and various energy efficiency provisions. Based on these observations, where inherent radon exposure risks have taken opposite trends, it is not suggested that adopting this energy performance-based design philosophy is related to these trends.<\/span><\/p>
Energy efficiency concerns coincided with changes in building ventilation. These concerns produced tighter buildings, requiring mechanical ventilation to maintain healthy indoor air balance. While the use of heat recovery ventilators in Sweden coincides with radon reduction, the opposite occurred in Canada. It became clear during the study that there was no correlation between the use of heat recovery ventilators and the increase of radon in Canada.<\/span><\/p>
Modeling predicts a bleak future for Canada over the next 30 years unless drastic changes occur.<\/strong> Most global strategies are limited and rely on convincing individuals to test and personally invest in radon mitigation solutions after construction if administrative levels are deemed too high. The overall effectiveness of this strategy is limited because it depends on many psychological, sociological, economic, and behavioral variables to persuade individuals to test for radon, understand results, and mitigate if necessary. This process is neither inclusive nor equitable. A systemic approach to eliminate radon from properties could be to require all buildings constructed after a certain date to be equipped with a mitigation system. Installation costs would be reduced by standardization, making it more inclusive and equitable.<\/span><\/p>
A major difference exists between heating methods in the two countries.<\/strong> In Canada, forced-air natural gas heating is present in 57% of buildings, and 2% use electric heating. In Sweden in the 2010s, district heating accounted for 70% of heating, and 10% used forced-air natural gas furnaces. District heating consists of a thermal plant producing steam distributed via a network of pipes to buildings. Forced-air systems significantly affect air dynamics and pressures within a building. While using a heat exchanger can reduce radon impact by 25% to 75%, the opposite appears true with forced-air natural gas systems. The prevalence of this heating type, especially in the Prairies where forced-air natural gas heating represents 77% to 94% of all heating types, is notable.<\/span><\/p>
A more detailed study should focus on these specific aspects, including heating methods, forced-air systems, and also parameters such as air conditioning use in summer, presence or absence of a chimney, wood stove, insulation, building age, and occupant lifestyle habits.<\/span><\/p>
Considering that 70% of the housing stock will still be built over the next 30 years, the future for our children looks bleak.<\/strong> The increase of radon in Canadian homes risks causing significant harm to non-smokers if no concrete measures are adopted. Therefore, the study suggests including in the future 2025 National Building Code the obligation to install a complete level 3 mitigation system at construction. Level 1 represents basic infrastructure with a standard conduit under the slab connected to a closed conduit above the slab. Level 2 adds a roof vent without mechanical ventilation, relying on the chimney effect to reduce radon levels. Level 3 adds a mechanical fan to the level 2 installation.<\/span><\/p>
We recommend readers consult the full study <\/span><\/p>
https://www.nature.com/articles/s41598-021-96928-x<\/a><\/span><\/p>
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