RADON, RADIATION AND LUNG CANCER for Building Scientists and

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