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Q: We are in the market for a new home. A work colleague
recently mentioned that, given the area where we’re looking, we should be
careful about radon in the soil around any house we’re considering. What is
radon, how does it get into buildings, and is it harmful enough that we should
A: Radon is – as its name might suggest – a radioactive gas
resulting from the natural breakdown of uranium. As radon decays, it produces
something called “radon daughters.” Two of these – polonium-218 and polonium-214
– decay rapidly themselves, and emit alpha particles. When alpha particles
interact with an object, the energy in them is absorbed by the surface of the
Human skin is thick enough to not be affected, but if you breathe in alpha
particles, they can be absorbed by and damage bronchial and lung tissue. When
lung cells are damaged, they have the potential to result in cancer when they
reproduce. Until recently, research into the dangers of radon exposure were
focused on uranium miners. But two independent scientific studies in Europe and
North America have shown that lung cancer risks extend to levels that are found
in some homes.
In confined spaces like a house basement (or a uranium mine), radon can
accumulate and be dangerous. A non-smoker exposed to elevated levels of radon
over a lifetime has a one in twenty chance of developing lung cancer. That
estimate increases to a one in three chance if a smoker is also exposed to
elevated levels of radon over a lifetime.
A 2010 report, Reducing Environmental Cancer Risk: What We Can Do Now
by U.S. President Obama’s Cancer Panel has some of the most strongly-worded
recommendations ever in regard to radon exposure. The report notes that the
cancer risk attributable to residential radon exposure has been underestimated
but is clearly demonstrated, and urges government to better address the risk.
According to the report, radon is the second leading cause of lung cancer in the
United States and the leading cause of lung cancer among people who have never
R. William Field, a University of Iowa professor of occupational and
environmental health and epidemiology, says, “Radon is likely our leading
environmental cause of cancer mortality in the United States. During the past
fifty years, over a million people have died nationwide from radon-related lung
In 2008, Field testified before the President’s Cancer Panel regarding
environmental factors in cancer. At that meeting, he discussed ever-increasing
exposure to radon due to new homes being built without radon-resistant features
faster than existing houses are mitigated to reduce radon.
The Canadian government is also concerned about residential levels of radon.
It says that in 2006, an estimated 1,900 lung cancer deaths in Canada were due
to radon exposure. As part of its National Radon Program, Health Canada is
currently conducting a multi-year residential radon survey in an effort to gain
a better understanding of radon concentrations in houses across Canada.
Thousands of houses will be tested and many more residents will complete phone
Testing for Radon
Predicting the level of radon in a building is difficult. Radon testing is
the only way to be sure if the gas is present in your home. Experts recommend
that homeowners periodically check their homes for radon levels and that
homebuyers conduct a radon test in any home they are considering buying.
The cancer risk attributable to residential radon exposure has
been underestimated. It is the second leading cause of lung cancer and the
leading cause among people who have never smoked.
You can either hire a company to do the testing or do it yourself. The
typical cost for a test is between $50 and $100, according to the Canadian Lung
Association. Radon detectors are available at hardware stores, building supply
centers, and online, and through some health departments. The detector is
exposed to the air in a house for an indicated period of time. (Some kits
suggest a few days but several months is the preferable term.) After testing is
completed, the home test kit is returned to the manufacturer for laboratory
Testing should be conducted with the doors and windows closed, during the
cooler months. The test kit should be placed in the lowest lived-in level of the
house, and away from drafts, high heat, high humidity, and exterior walls.
The concentration of radon in the air can be measured in two different ways.
The international community uses the becquerel per cubic meter of air
measurement, while the USA uses picocuries per liter. One pCi/L is equivalent to
In 2009, the World Health Organization set its recommended radon reference
level to 100 Bq/m³, for residential structures, with an upper limit that should
not exceed 300 Bq/m³. Canada’s guideline for maximum exposure to radon in indoor
air is 200 Bq/m³ (updated in 2007 from 800). The reference level in the USA is 4
pCi/L or approximately 150 Bq/m³. Reference levels for individual countries in
the EU range from 200 to 400 Bq/m³.
Radon is colorless and odorless, and can seep into your
home from the surrounding soil.
How Radon Gets Into A Home
Radon is colorless and odorless, and can seep into your home from the
surrounding soil. If your home is in an area where the soil and rocks contain
uranium, granite, shale, or phosphate, you’ll likely find radon. It may also be
found in soils contaminated with certain types of industrial waste such as the
by-products of uranium or phosphate mining.
In fact, at one time, some houses were built using the sand-like uranium
tailings (pulverized rock) as construction material. As a result, some houses
contain levels of radon gas and radon daughters even higher than those in mines.
However, radon can be a problem in buildings of all types. It seeps through
small spaces in the soil and rock on which a house is built. It enters through
dirt floors, gaps in suspended floors and around pipes, cracks in concrete
walls, sump pumps, joints, basement drains, under the furnace base, and jack
posts if the base is submerged in the floor.
Reducing Radon Levels
If testing indicates that high levels of radon are present in your home, you
should act quickly to reduce the levels. According to the U.S. Environmental
Protection Agency (EPA), high levels of radon can be solved at a price
comparable to having a hot water heater installed or the house painted. A
trained contractor with experience in radon mitigation can examine your house,
locate the source of radon, and make repairs.
There currently is no certification program in Canada for radon mitigation
contractors, although Health Canada is developing one. In the U.S.,
certification programs are offered through the National Environmental Health
Association and the National Radon Safety Board. Canadian contractors who have
undergone that training are recognized by Health Canada.
Renovations to basement floors, particularly dirt ones, sealing cracks and
openings, and sub-floor ventilation can prevent radon from entering. Two coats
of paint followed by a sealant are recommended for cement basement floors and
foundation walls. Levels of radon three feet below the ground level can be a few
hundred percent higher than the levels inside a basement, so it’s important to
ensure that all cracks are filled.
Soil depressurization ventilates the soil surrounding the house so that radon
is drawn away before it can enter. This system can be installed in an existing
house and is increasingly being put in place during construction of new houses.
Increasing the ventilation within your home will also help lower the levels
Wendy Priesnitz is Natural Life's editor and a
journalist, author, and former broadcaster with over 35 years of experience.