What is radon?
Radon is a colorless, odorless radioactive gas which comes
from the natural breakdown (radioactive decay) of radium, which
is a decay product of uranium. Uranium and radium are both common
elements in the soil. The Surgeon General has warned that radon
is the second leading cause of lung cancer in the U.S. today.
Only smoking causes more lung cancer deaths. If you smoke and
your home has high radon, your risk of lung cancer is especially
high.
Where is radon found?
The major source of high levels of radon in homes is soil
surrounding and under the house, particularly soil containing
uranium. Radon is found all over the U.S. and the world. Some
areas have more radon problems than others because of varying
concentrations of radon-producing minerals in the soil, variation
of soil types from one place to another, and different characteristics
found in individual homes. Radon problems have been identified
in every state. EPA estimates that as many as 1 in 15 homes
have elevated annual radon levels.
What are the health risks?
Almost all scientists agree that radon is a health hazard
to humans and that it causes lung cancer. Risk calculation and
the action level usually raise debate. The EPA has declared
radon to be a "Class
A Carcinogen," which means that it has been shown to cause
cancer in humans.
Radon gas decays into radioactive solid particles that can get
trapped in your lungs when you breathe. As the particles break
down further, they release small bursts of energy that can damage
lung tissue and lead to lung cancer. Not everyone exposed to
elevated levels of radon will develop lung cancer. The amount
of time between exposure and the onset of disease may be many
years. Smoking combined with radon exposure is an especially
serious health risk. You can reduce your risk of lung cancer
by stopping smoking and lowering the radon level in your home.
What levels are too high?
Radon is measured in picoCuries per liter (pCi/L) of air.
A picoCurie is a measure of the amount of radioactivity of a
particular substance. A liter is about equal to a quart. The
level of radon in outdoor air is about 0.4 pCi/L. The average
indoor radon level is about 1.3 pCi/L. EPA has established 4.0
pCi/L as the action level for radon in homes, schools and workplaces.
This is a technology-based number, not a health-based level.
Current mitigation technology can generally reduce radon levels
to 3.9 pCi/L or less. Since radon is a carcinogen, no level
is completely risk-free. However, since it is a natural part
of the environment there is no such thing as a "0" level.
What is a PicoCurie?
Radioactivity is commonly measured in picocuries (pCi). This
unit of measure is named for the French physicist Madam Marie
Curie, who was a pioneer in the research of radioactive elements
and their decay. One pCi is equal to the decay of about two
radioactive atoms per minute. Because the level of radioactivity
is directly related to the number and type of radioactive atoms
present, radon and all other radioactive elements are measured
in pCi. For instance, a house having 4 pCi of radon per liter
of air has about 8 or 9 atoms of radon decaying every minute
in every liter of air inside the house. A 1,000 square foot
house with 4 pCi/L of radon has nearly 2 million radon atoms
decaying in it every minute.
How does radon get into homes?
Radon is a soil gas that typically moves up through the ground
to the air above. Air pressure inside a home is usually lower
than pressure in the soil around the home's foundation. Because
of the difference in pressure, a house acts like a vacuum, drawing
radon in through dirt floors, hollow-block walls, cracks in
the foundation floor and walls, and openings around floor drains,
pipes and sump pumps.
Any home may have a radon problem. This includes new, old, well-sealed
or drafty homes, and homes with or without basements. Radon
is generally more concentrated at lower levels, like basements,
ground floors and first floors.
My neighbor got a low reading, so I should not have a problem
... should I?
Radon test results from other homes in the neighborhood should
not be used to estimate the radon level in a particular home.
Homes which are next to each other can have different indoor
radon levels. In fact, one of the highest levels ever found
in a home (>3,000 pCi/L) was across the street from a home
which measured less than 4 pCi/L. Testing is the only way to
know.
Should every home be tested for radon?
YES. Testing is the only way to know if you and your family
are at risk from radon. The Environmental Protection Agency
(EPA) and the Surgeon General recommend testing all homes.
The EPA action level of 4 pCi/L actually represents an annual
average. Because radon levels tend to vary from day-to-day,
and season-to-season, a short-term test (days) is less likely
than a long-term test (months) to provide the year-round average
radon level. However, when results are needed quickly, a short-term
test followed by a second short-term test, or two short-term
tests placed side by side, and the results averaged, can be
used. For either approach the test should last at least 48 hours.
Should you hire an inspector to do the testing?
A trained inspector should be hired to do the test. Make certain
the person hired is - working through a certified lab.
When is the best time to test for radon?
Anytime that windows and doors are normally kept closed is
a good time to test. This is generally in the winter or summer
months, when heating or cooling systems are running. For short-term
tests, the house should be closed up for 12 hours before the
test begins and throughout the test.
If a house has been unoccupied and closed up for several months,
the result may more closely approximate what the radon levels
would be with people living in the house if the temperature
in the house is allowed to return to the normal living range.
What are the testing protocols?
EPA has issued "protocols" or guidelines for radon
testing in the home as well as for testing associated with real
estate transactions.
The testing procedures or protocols that are used when a house
is being tested in connection with a real estate sale, are listed
in the "Home Buyer's and Seller's Guide to Radon" (EPA
402-K-00-008, July 2000).
The standard protocols are provided in "A Citizen's Guide
to Radon" (EPA 402-K92-001, May 1992) This guide provides
protocols for both short and long-term radon testing.
Are the tests accurate / reliable?
NEHA certifies the companies that make and analyze test kits.
To ensure that you get reliable results, look for a test kit
from a company that has successfully completed the this certification
process.
How long does it take to get the results?
The length of time it takes to get results varies with the
manufacturer or laboratory, but generally results can be expected
within a couple of weeks. Some NEHA-certified laboratories will
fast-track the results when real estate transactions are involved.
How should the house be prepared for a radon test?
Providing "closed house conditions" during short-term
tests means that all windows are kept closed, and doors are
kept closed except for normal entry and exit. Heating and air
conditioning units can be operated as long as they do not introduce
outside air. Exhaust or attic fans should not be used. These
conditions should be maintained for twelve hours prior to initiation
of the test, then throughout the remainder of the test.
Does it matter if the house has been closed up for several
months?
It does not matter if a house has been closed up for months
when you test it. In fact, for short-term tests (2-3 days) the
house should be closed up for 12 hours before the test begins,
as well as throughout the testing period. However, to more closely
approximate what the radon levels would be when occupied, the
temperature could be allowed to return to some "normal" level
prior to testing.
What if a radon test was done in a basement which has an open
crawl space area?
Radon tests should only be done in areas which can be used
as living space. A basement connected to an open crawl space
should not be used as living space without major remodeling.
Hence it is an inappropriate test site.
EPA has not developed radon testing protocols for commercial
buildings. However, EPA has developed testing protocols for
schools. These protocols call for initial short-term measurements
to be taken simultaneously in all frequently-occupied rooms
in contact with the ground. Follow-up tests should be performed
for every room that initially tests 4 pCi/L or greater. For
follow-up tests, use a short-term test if results are needed
quickly; use a long-term test to better understand the average
radon level for a school year. See the publication "Radon
Measurement in Schools; Revised Edition" EPA 402-R-92-014.
Soil Testing?
EPA does not recommend soil testing
for radon prior to construction of new buildings. The reason
is that the radon concentrations in soil can be much different
from one point on a lot to another. Testing enough locations
at enough depths on a site would be very expensive. A much
cheaper and more reliable approach is to use radon resistant
techniques when the building is built. These techniques are
very inexpensive, help protect the home from radon, and also
help solve other problems like moisture in the home. Many
of the techniques are already used by good builders. See EPA
publications "Radon-resistant Construction
Techniques for New Residential Construction" (EPA/625/2-91/032)
and "Radon Prevention in the Design and Construction of
Schools and Other Large Buildings" (EPA/625/R-92/016) for
more information.
In municipal water systems most of the radon will escape to
the air during processing. It tends to be the smaller rural
water systems and well water which may have elevated radon in
water levels.
Radon can reach concentrations of many thousands of picoCuries
per liter in water. The major health threat is not associated
with drinking the water, but rather from breathing the radon
that escapes the water and enters the air. An example of this
is breathing the air while taking a shower. There is a very
rough 10,000 to 1 conversion factor from radon in water to radon
in air. For example, 10,000 pCi/L of radon in water would give
about 1 pCi/L in air. Similarly, 25,000 pCi/L in water gives
about 2.5 pCi/L in air.
Individual water supplies can be treated by aeration or installation
of granular activated carbon (GAC) absorbers. A GAC system is
less expensive than aeration but would still cost approximately
$1,000 to install, plus additional costs to maintain. Depending
on the initial radon levels, disposal of the carbon can become
a problem over time. There are currently no drinking water standards
for radon in water, although standards have been proposed. The
final number (in pCi/L) won't be determined until additional
studies and analyses have been completed.
EPA has developed specific testing protocols for use during
real estate transactions. They can be found in the "Home
Buyer's and Seller's Guide to Radon" (EPA 402-K-00-008,
July 2000). For passive tests the recommendation is: "Take
an initial short-term test for at least 48 hours. After the
first test has been completed, take a follow-up short-term test
for at least 48 hours." or "Take two short-term tests
at the same time in the same location for at least 48 hours." For
either approach, "Fix the home if the average of two tests
is 4 pCi/L or more." For an active test, "Test the
home with a continuous monitor for at least 48 hours. Fix the
home if the average radon level is 4 pCi/L or more."
If your home has radon, can it be fixed?
There are simple ways to fix a radon problem that aren't too
costly. Even high levels can be reduced to acceptable levels
in most cases.
For new homes, consider Radon-Resistant Construction systems
which allow for control measures to be installed cheaply and
without major renovation to your home.
How to reduce (mitigate) radon levels in existing homes?
There are two approaches to radon mitigation or reduction.
One is to prevent the radon from entering the structure and
the other is to remove the radon after it enters the structure.
Generally, the best approach is to prevent the radon from entering.
Some of the techniques used are soil depressurization, sealing
cracks and joints, pressurizing the building, or a combination
of these. Sealing foundation joints and cracks is rarely sufficient
as a stand alone mitigation technique. Soil depressurization,
the most common approach, involves running PVC pipe through
the slab (or underneath a membrane in a crawl space), then routing
it up and through the roof. A fan is attached in the attic area,
and the radon is thus drawn from below the slab (or membrane)
and vented above the roof where it is quickly diluted in outside
air. Pressurization is fairly difficult to maintain, and is
less commonly used as a mitigation approach.
What about new construction?
New homes can be built with radon-resistant features that
minimize radon entry and allow easier fixing of radon problems
that could occur later. These features cost less if installed
during construction than if added to an existing home. Materials
and labor cost for the radon-resistant techniques cost less
than $100, versus the cost of retrofitting an existing home
at $800 to $2,500. In most new homes, use of radon-resistant
features will keep radon levels to below 2 pCi/L.
In many cases, a passive system is all that is needed to effectively
reduce indoor radon levels. Nevertheless, occupants of newly
constructed homes should test their homes for radon. If the
indoor radon levels measure 4 pCi/L or higher, a fan should
be installed in the vent pipe to make the system active.
What is a passive radon resistant system?
A passive radon resistant system pulls radon from beneath
the home, carries it up through the home in a pipe, and exhausts
it above the roof. It differs from an active system in that
the active system includes a fan in the pipe as it goes through
the attic. The fan in an active system operates continuously,
pulling radon-laden air from the soil beneath the lowest floor.
In a passive system, the natural rising of warm air through
the pipe continuously exhausts a low flow of air and radon from
beneath the lowest floor of the house.
How do you install a passive radon resistant system?
First, there is a gas permeable material beneath the lowest
floor. This is usually gravel, although other materials can
be used. Plastic sheeting is placed above this, and the concrete
floor on the sheeting. A 3 to 4 inch plastic pipe runs from
the gravel through the sheeting and concrete, up through the
house and through the roof. All the penetrations below ground
level, such as the basement floor-wall joint, and plumbing and
electrical penetrations, are caulked. This allows the natural
convection of warm air moving up the pipe to create a slight
vacuum in the gravel beneath the concrete. This vacuum pulls
air and radon up the pipe and exhausts it above the roof. The
caulking helps prevent air from the living space from being
pulled below the floor, and improves the vacuum beneath the
floor.
Can a radon mitigation system contribute to backdrafting?
Backdrafting is the condition that exists when the combustion
products from a furnace or hot water heater are drawn back into
the home rather than going up the chimney. This can happen when
the air pressure in the house is so low that air is actually
sucked down the chimney and into the home. A radon system pulls
air from beneath the lowest floor. If cracks and penetrations
in that floor and the floor wall joint are not properly caulked,
the system could pull air from the lowest level of the house
and thereby lower the air pressure in that level, possibly causing
backdrafting.
If my radon level is only 4.2 pCi/L, will it help to seal
cracks in the floor? If so, with what?
If your initial test result is 4.2 pCi/L based on a short
term test, another test should be conducted as a follow-up.
It is possible that the result of such a test would be below
4.0 pCi/L.
However, if your home's actual radon concentration is 4.2 pCi/L,
sealing cracks in the floor and wall joints is a good first
step in solving the problem. A gun-grade polyurethane caulk
should be used. This should be considered a first phase, to
be followed by another short-term test, and possibly other solutions. |
