A Comparative Study of Radon Levels in Federal Buildings and Residential Homes in Canada.

Shortly after revision of the Canadian radon guideline from 800 to 200 Bq m, Health Canada established the Federal Building Testing Program in 2007 to demonstrate federal leadership in raising awareness about radon risk and the need for testing. By the end of 2017, more than 7,600 federal workplaces had been tested for radon. As is the case in all radon surveys, radon levels vary widely; federal building results ranged from below the detection limit to more than 2,500 Bq m in a few rooms of a few buildings. Weighted by the population of federal public servants across Canada, the average radon distribution in federal workplaces has a geometric mean of 22.0 Bq m with a geometric standard deviation of 2.3. The population-weighted arithmetic mean is 34.3 Bq m, significantly lower than the population-weighted average radon concentration of 72.9 Bq m in residential homes across Canada. On average, 2% of federal workplaces have radon concentrations above 200 Bq m, which is also significantly lower than the 7% of residential homes that tested above 200 Bq m. This comparative study demonstrated clearly that radon education and awareness in Canada should focus more on residential testing and remediation actions to effectively reduce the burden of radon-induced lung cancer.

Radon mitigation in cold climates at Kitigan Zibi Anishinabeg.

Available radon mitigation results were gathered for 85 houses mainly by installing sub-slab depressurization systems (SSDS) with two types of discharge and fan locations: Above ground level discharge with the fan located in the basement (AGL) or above roof line discharge with the fan located in the attic (ARL). A comparative analysis was made of mitigation efficiency and of exhaust icing. Results show that both SSDS scenarios reduced radon levels similarly. The results of SSDS with AGL show that a sealed radon fan having proper fittings and sealed piping was able to reduce the radon to acceptable levels, and that these installations were less subject to obstructive icing of the exhaust in cold climates.

Results of simultaneous radon and thoron measurements in 33 metropolitan areas of Canada.

Radon has been identified as the second leading cause of lung cancer after tobacco smoking. (222)Rn (radon gas) and (220)Rn (thoron gas) are the most common isotopes of radon. In order to assess thoron contribution to indoor radon and thoron exposure, a survey of residential radon and thoron concentrations was initiated in 2012 with ∼4000 homes in the 33 census metropolitan areas of Canada. The survey confirmed that indoor radon and thoron concentrations are not correlated and that thoron concentrations cannot be predicted from widely available radon information. The results showed that thoron contribution to the radiation dose varied from 0.5 to 6% geographically. The study indicated that, on average, thoron contributes ∼3% of the radiation dose due to indoor radon and thoron exposure in Canada. Even though the estimated average thoron concentration of 9 Bq m(-3) (population weighted) in Canada is low, the average radon concentration of 96 Bq m(-3) (population weighted) is more than double the worldwide average indoor radon concentration. It is clear that continued efforts are needed to further reduce the exposure and effectively reduce the number of lung cancers caused by radon.

Residential radon mitigations at Kitigan Zibi Anishinabeg: comparison of above ground level (RIM JOIST) and above roof line discharge of radon mitigation SUB-SLAB depressurization systems.

Radon mitigations in nine houses were conducted by installing sub-slab depressurization systems (SSDS) with two types of discharge and fan locations: Ground level discharge with the fan located in the basement or roof-discharge with the fan located in the attic. This paper presents a detailed comparative analysis of the radon reduction efficiency, condensation problems, and the cost-effectiveness of both SSDS installation scenarios in nine houses. The mitigations from both SSDS scenarios were successful in reducing radon. The results of rim-joist installations discharging above ground level with the fans located in the basement show that a sealed radon fan with proper fittings and sealed piping were able to reduce the radon to acceptable levels in a cost-effective manner.

Uranium in drinking water: renal effects of long-term ingestion by an aboriginal community.

The authors conducted a study of an aboriginal community to determine if kidney func-tion had been affected by the chronic ingestion of uranium in drinking water from the community's drilled wells. Uranium concentrations in drinking water varied from < 1 to 845 ppb. This nonin-vasive study relied on the measurement of a combination of urinary indicators of kidney function and markers for cell toxicity. In all, 54 individuals (12-73 years old) participated in the study. Correlation of uranium excreted in urine with bio-indicators at p

Correlation of soil radon and permeability with indoor radon potential in Ottawa.

Soil gas radon and soil gas permeability measurements were conducted at 32 sites across the five most populated communities in the city of Ottawa where indoor radon measurements were available for 167 houses. A soil radon index (SRI) determined from the soil radon concentration and the soil gas permeability was used to characterise radon availability from soil to air. This study demonstrated that the average SRI in a community area correlates with the indoor radon potential (the percentage of homes above 200 Bq m(-3)) in that community. Soil gas radon concentrations together with soil gas permeability measurements can be a useful tool for the prediction of the indoor radon potential in the development of a Canadian radon risk map.

Long-term monitoring of soil gas radon and permeability at two reference sites.

The long-term monitoring of soil radon variations was conducted at two reference sites in Ottawa. The purpose of this study was to determine whether a single soil radon survey could provide a representative soil radon characteristic of the site. Results showed that during the normal field survey period from June to September in Canada, a single field survey with multiple measurements of soil gas radon concentrations at a depth of 80 cm can characterise the soil radon level of a site within a deviation of +/-30%. Direct in situ soil permeability measurements exhibited, however, large variations even within an area of only 10 x 10 m(2). Considering such large variations and the weight of the equipment, soil permeability can be determined by direct measurements whenever possible or by other qualitative evaluation methods for sites that are hard to access with heavy equipment.

Preliminary results of simultaneous radon and thoron tests in Ottawa.

Ottawa is the capital city of Canada. In the previous cross Canada radon survey, Ottawa was not included. There is great interest to know radon level as well as thoron concentration in Ottawa homes. Therefore, radon/thoron discrimination detectors developed at the National Institute of Radiological Sciences in Japan were deployed in 93 houses for a period of 3 months. As expected, thoron is present in Ottawa homes. Radon concentrations ranged from 8 to 1525 Bq m(-3) while thoron concentrations varied from 5 to 924 Bq m(-3). The arithmetic mean of radon and thoron concentrations were found to be 110 +/- 168 and 56 +/- 123 Bq m(-3), respectively.

Field evaluations of digital radon detectors.

Recently, digital radon detectors were made available on the market for homeowners at a cost comparable to that charged by some service providers for a single radon test. Digital radon detectors provide an easy and less expensive way for homeowners to monitor radon levels in their homes. In order to answer a frequently asked question regarding the performance of such low-cost electronic radon detectors, field evaluations were conducted. Evaluation results are reported here.