RADON, RADIATION AND LUNG CANCER for Building Scientists and
RADON, RADIATION AND LUNG CANCER for Building Scientists and Design Professionals. Why all the fuss? We have likely all heard about radon at some point in our professional career. I have heard many different views about the severity of the risk associated with radon. Far too often the opinion is that radon is not a problem in our geographical area and can’t be a problem with the way we design and build today. Nothing could be farther from the truth. In 2012 Health Canada completed a cross country study aimed “to obtain an estimate of the proportion of the Canadian population living in homes with radon gas levels above the guideline of 200 Becquerels per cubic meter of air (Bq/m3) and to identify previously unknown areas where radon gas exposure may constitute a health risk”1 The study comprised of approximately 14,000 homes with a 77% participation rate. From this study it has been determined that about seven per cent of Canadians, roughly 2.4 million people, are living in homes above the guideline which puts them at an elevated risk of lung cancer. Although the study focused on residential dwellings it does not mean that commercial, institutional and industrial buildings are not also affected. If someone lives in a home that is high in radon and is employed in the same area they are also likely overexposed at work to. The study demonstrates that the “designated areas” listed in the Ontario Building Code (OBC) and the Supplemental Standard SB-9 do not necessarily have the highest percentage of homes or buildings which exceed the acceptable standard. A recently completed radon potential map of Canada indicates that a vast portion of southern Ontario has a high relative radon hazard. It is clear that Radon problems do exist in Canada and they are not as isolated as once believed. This discovery warrants a closer look by building and design professionals as we strive to construct greener and healthier buildings. Radon, a radioactive, colourless and odourless gas, is the number one cause of lung cancer among non-smokers and the second leading cause of lung cancer overall. Radon is created from the radioactive decay of uranium and uranium-bearing rock which makes up a large amount of the Earth's crust. Inevitably radon from soil will enter buildings, driven by stack effect through cracks in basements, floors, drains, sump pits, exposed soil, construction joints, floor slab cold joints, etc. Once radon has entered a building it tends to concentrate and can easily be inhaled deeply into the lungs. This internal radiation exposure increases an individual's risk of lung cancer. Today we strive to “build tight and ventilate right” but due to imperfections, no matter how well designed or constructed are buildings are they will have air leakage and soil 1 Health Canada, Cross-Canada Survey of Radon Concentrations in Homes.: Final Report. Ottawa: Publications Health Canada March 2012 gas connectivity. It is because of this that we can’t keep radon out by sealing alone. Keeping radon out by sealing requires the perfect air barrier or in this case soil gas barrier. Since this is not attainable in practicality we cannot rely solely on the efficacy of a barrier system to stop radon intrusion. We also need to ensure our LEED green building features do not cause a radon issue. Earth-air heat exchangers (EAHE or EAHX) commonly known as earth tubes, if designed, installed or maintained improperly can become a very effective radon collection system. Design details for these systems explain joints connecting the components must be tight to prevent gas infiltration and that porous materials like uncoated concrete tubes cannot be used. Care must also be taken with the drainage of these systems. If the drains gas lock system is insufficient radon can and will be actively drawn from the soil and pumped into the buildings breathing air. In theory, if there is adequate air changes with these systems the radon will be effectively diluted. The problem with this is that we cannot estimate the radon concentration in the building or be absolutely sure that the system is not drawing radon until construction is complete. We have to test after occupancy to know if the limits are exceeded. I have asked designers about radon and earth tube systems they have implemented. The typical response I get is “we haven’t found it to be a problem”. Out of interest I have asked to see the post occupancy radon tests. Needless to say I am still waiting. As a registered industrial hygiene professional and indoor air quality specialist I have been pleased to see the LEED indoor air quality testing program as a positive step to ensuring healthy indoor air. If one takes the testing route for LEED credits, formaldehyde is one of the specific compounds sampled for. This is undoubtedly due to its high prevalence in building materials and its carcinogenicity (ability or tendency to produce cancer). Radon is virtually everywhere and is carcinogenic (cancer causing) but unlike formaldehyde, which will off-gas within a few months to a year of construction and leave no source in the building; radon comes from uranium that has a nuclear halflife of 4.5 billion years. It would take 45 billion years for radiation source affecting the building to be depleted. I have tested and mitigated my home for radon but in the six years I have lived in it I have never once considered testing for formaldehyde. Of an interesting note, I had an HRV installed and properly balanced when my home was constructed, however, this mechanized air exchange system failed to control the radon to safe levels. Since Tarion recognizes radon as a warrantable claim for new home builds within the 7 year major structural period, I am lucky to be in a position to recoup my mitigation costs. With all this in mind we can clearly see why Health Canada is taking a very active role in promoting radon awareness and reducing Canadians exposure to radon. Bill 96 - An Act to raise awareness ab out radon, provide for the Ontario Radon Registry and reduce radon levels in dwellings and workplaces, is a Private Members Bill currently under review and awaiting third reading by the Ontario Legislature. If passed, the Bill will define a workplace as having the same meaning as the Ontario Occupational Health and Safety Act and will place duties on owners of workplaces to test for radon and mitigate where levels exceed 200 Bq/m3. A deadline for completion testing has been stipulated as December 31, 2016. Failure for an individual to conduct the testing is a contravention of the Act and upon conviction carries a maximum fine of $25,000 or imprisonment for a maximum term of 12 months. If a corporation is convicted of an offence a maximum fine of $500,000 can be imposed. The Bill also carries provision to amend the Building Code Act by “requiring any building that will be used as a dwelling to be constructed in a manner and using materials that minimize radon entry and facilitate post-construction radon removal”. Bill 96 and Health Canada’s Radon Guidelines prescribe that testing be conducted by a "radon measurement specialist." Experts in the United States and Canada have shown that predicting a building’s indoor radon concentration based purely on geographic location (a map) is inaccurate and unsafe. The only way to know what the radon concentrations in a building are is to test it after occupancy. The conditions present due to occupant behaviour and their operation or alteration of the HVAC systems can influence the radon concentrations so pre-occupancy testing is not representative of occupant exposures. How to Test for Radon Air testing, as prescribed by Health Canada, is conducted by deploying a small sampling detector in the lowest lived-in level of a building and leaving it undisturbed for a period of time. Depending on the sampling method used, sample durations can range from 48 hours to one year. Health Canada recommends sample durations of three to 12 months and never less than one month. The reason for such long sample durations is to compensate for fluctuations in radon concentrations from daily and seasonal weather, occupant activity, and other inherent variables. Once sampling is complete the results are compared to the 200 Bq/m3 annual exposure criterion. If the building has elevated radon concentrations, mitigation measures to reduce the concentration should be implemented within a reasonable time frame. These time frames are stipulated in Health Canada’s documents. Table 1: Health Canada recommended remedial action time lines Radon Concentration > 600 Bq/m3 200 Bq/m3 to 600 Bq/m3 Recommended Remedial Action Time In less than 1 year In less than 2 years <200 Bq/m3 No Action Required How to Mitigate Radon Levels There are several ways to mitigate radon levels in a building as each building is unique. The method used also requires careful consideration of the cost versus benefits, optimizing health and safety with available funds. The most effective and perhaps preferred method of mitigation is sub-slab depressurization (SSD). A typical SSD system involves coring holes through the basement floor slab and installing draw piping and an air tight in-line fan that exhausts outdoors. A small fan generates a slight negative air pressure relative to the building interior under the floor slab. This prevents the radon from entering the building and vents it outdoors for dissipation where it is diluted to an acceptable level. Designing a building with this system roughed in is simple and makes retrofitting a radon mitigation system less expensive and much more aesthetically pleasing. For a single family residential dwelling, a properly predesigned system could be fully integrated into the building and made active for under $1000. A post construction mitigation system will cost between $3000 to $4500. One can scale the dollar value up based on square footage and complexity to give an idea of industrial, commercial or institutional buildings. Post mitigation testing is required to ensure the system has reduced radon to below the applicable levels. Most agencies recommend a building be retested every two years after a mitigation system is implemented to ensure it is operating properly. Regardless of whether or not a mitigation system is installed, retesting should be conducted whenever major renovations are performed. The author knows of at least one improperly designed passive system that actually increased radon concentrations by six fold. So doing it right the first time with radon certified professionals is the best option. Radon Professionals Designation Radon measurement specialists and mitigation contractors must meet an acceptable level of competence to be granted proficiency status. The National Radon Safety Board / Canadian National Environmental Health Association (NRSB / C-NRPP) is proof that an individual possesses the skills and knowledge to conduct radon testing, assessment and/or mitigation. With the radon landscape quickly changing building scientists and design professionals need to be aware of the reality of radon and what appears to be its eventual legislated control. Threshold criteria for indoor radon levels and typical outdoor levels World Health Organization 100 Bq/m³ 2.7 pCi/L U.S. EPA 150 Bq/m³ 4.0 pCi/L Health Canada 200 Bq/m³ 5.4 pCi/L 5 to 15 Bq/m³ 0.1 to 0.4 pCi/L Outdoor Ambient Range Bq/m3 = Becquerel per cubic metre of air (1 becquerel = 1 disintegration per second) – SI Unit pCi/L = Picocurie per litre of air (1 Picocurie = 0.037 disintegrations per second) American Unit For more information on radon, please contact: Bruce Decker, C.E.T., ROHT, BSSO References An Act to raise awareness ab out radon, provide for the Ontario Radon Registry and reduce radon levels in dwellings and workplaces. May 2011 (2nd Reading) Bill -182 Canadian Nuclear Safety Commission, Uranium Mines and Mills in Canada, http://nuclearsafety.gc.ca/eng/about/regulated/minesmills/#Section4 Natural Resources Canada, Canadian Minerals Yearbook (CMY) - 2008: Uranium, http://www.nrcan.gc.ca/minerals-metals/business-market/canadian-mineralsyearbook/2008-review/commodity-reviews/3853 - 2008. Oster, Colditz & Kelley. “Statistics of 14,400 annual radon lung cancer deaths” National Cancer Institute. 1984 Statistics Canada, http://www.statcan.gc.ca/pub/12-581-x/2012000/pop-eng.htm US Environmental Protection Agency, Health Risks - Radon http://www.epa.gov/radon/healthrisks.html June 26, 2012 Health Canada, Guide for Radon Measurements in Residential Dwellings (Homes). Ottawa: Publications Health Canada, 2010 Health Canada, Guide for Radon Measurements in Pub lic Buildings (Schools, Hospitals, Care Facilities, Detention Centres). Ottawa: Publications Health Canada, 2008 Health Canada, Reducing Radon Levels in Existing Homes: A Canadian Guide for Professional Contractors to provide direction on proper assessment and mitigation of radon. Ottawa: Publications Health Canada, 2010 Health Canada, Cross-Canada Survey of Radon Concentrations in Homes.: Final Report. Ottawa: Publications Health Canada March 2012 World Health Organization (WHO) - Radon and cancer http://www.who.int/mediacentre/factsheets/fs291/en/index.html
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