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Most people have their first experience with radon when buying or selling a home. Indeed, radon is a home seller's nightmare!  Visualize it... thousands of homeowners lay sweating in their beds, wondering if the sale of their home may be jeopardized by the whims of a little charcoal canister the realtor placed in their basements... the radon detector!!  If the readings are too high, a fear-filled buyer may take his money and run... or demand expensive repairs to the home.  Let's investigate radon and find out where the middle road is... and who is on it!

What is radon, and where does it come from?  In a nutshell...

Prior to 1984, radon gas was considered a health risk only for workers in uranium mines.  That changed in 1984, when a nuclear engineer by the name of Stanley Watras was leaving work at the new Limerick Nuclear Power Plant in Pottstown, PA.  Radiation warningAs was the routine, all workers were required to pass through radiation monitors at the exit doors of the plant.  As Stanley stepped through, the alarms went off!   There was no sign of a leak in the plant which eventually led safety officials to his home in Boyertown.  They found radiation levels in the Watras' home more than 100,000 times the normal background level!  Apparently, the house was located over a natural radon "vent", pumping massive amounts of radon into the Watras' basement.

Radon fits the classic pattern for sneaky building dangers.  It is odorless, colorless, tasteless... and doesn't bring a brass band when it drifts into your home!  It is a natural gaseous byproduct of the decay of uranium, a radioactive mineral that exists at various concentrations in the crust of the earth.  Radon normally rises from the depths of the earth and disperses into the atmosphere harmlessly.  Well, that is if there's not a building in the way!

If there is an enclosed structure in radon's path... say a nice old residential home with a dirt basement or crawlspace... the radon enters the enclosed area through the soil and begins to accumulate within it.  Having a cement floor in the basement can reduce radon gas infiltration but only to the degree that the floor is solid, nonporous and crack-free.  A water sump hole or drainage system can be a Welcome mat for radon.

But you never go into the basement?  That doesn't necessarily mean you are "home-free".  Radon can also rise into the living space through cracks in the floor, around chimneys, around plumbing pipes and through the ducts of forced air heating systems. And there are other sources of radon besides the bowels of the earth.  That stone foundation or massive fireplace can also be emitting radon gas.  Natural building materials such as wallboard, concrete and even wood are "emitters".  One large contributor to radon gas in some geographical areas is the water supply.  Deep wells draw radon-contaminated water into your home which is released when the water is used to bathe, cook or drink.  Even public water supplies can bring radon into the home, though at lower levels than "air tight" well systems.

Where you live can be more important than how you live when it comes to total radon exposure.  Certain areas of the country have naturally greater soil radon levels, as shown in the map below (courtesy US Geological Survey).  Some of the causes of these elevated radon levels are the amount of uranium in the bedrock, fault lines and fissures in the bedrock allowing easy movement of radon from deep in the earth and residual soil from uranium mining.

Radon map

There is no lack of geographic radon information available.  USGS publishes "geologic radon potential" books which give thorough information on local radon conditions.  They can be ordered online at   These books are available for each of the EPA's 10 regions, each region covering from 3 to 8 states.

Click HERE to view the United States and State-by-State Radon Maps

The health effects of radon are obvious... but not the risks.  The truth is out there... but where?

Most of the information gleaned about radon's effects on the human body have come from studies of workers in uranium mines. Unusual levels of lung cancer among workers with otherwise low total radiation exposure led to the discovery that this mildly radioactive gas was more dangerous than had been believed.

The risk to the human body from radon gas is primarily to the lung, but the danger is not simply through breathing in the gas.  In fact, radon gas is not absorbed by the body and is exhaled immediately!  The process is a little more complicated.  Like other radioactive substances, radon decays or splits into smaller particles over time, simultaneously releasing dangerous ionizing radiation. These particles, called radon "progeny", can attach themselves to airborne dust due to their electrical charge.  When this radioactive dust is inhaled, the dust may remain in the lungs for long periods of time, especially in people with decreased lung function such as smokers and the breathing impaired.  Delicate lung tissues are bathed in radiation as the radon progeny decompose releases bursts of ionizing radiation.   There is absolutely no doubt that radon causes cancer!

But don't go out and raise your house onto posts just yet!   Evaluating risk is... well... risky. Here is a quote from the summary statement from the 1994 EPA report Facts Concerning Environmental Radon...

"To date the EPA has had little success in stimulating home owners to measure levels in their homes which would be the first step in the process of deciding on a course of action if a high radon level is found. This is partly because it is difficult to get people concerned that their home, a place that one looks to for security, is a potential source of hidden danger. Also, it has not yet been possible to generate convincing data on increased risk at or below 4-8 pCi/liter (emphasis added)."

Current EPA guidelines suggest that action be taken if the radon level in any occupied part of your home reaches or exceeds 4 pCi/L.  Radon is measured in picocuries per liter of air (pCi/L). To understand the relative amounts you may be exposed to, the average indoor level is 1.3 pCi/L, and about 0.4 pCi/L is normally found in the outside air.  Curiously, there are no Federal regulations concerning maximum allowable radon levels in residences.  I was troubled by this, perhaps because the Feds are zealous regulators... that is their job and purpose.   Perhaps the aforementioned lack of  "convincing data", and maybe their experience with failed asbestos control regulation in the courts, have produced this uncharacteristic lack of regulatory zeal.

Furthermore, the EPA's proclamation of radon's status as the number two cause of lung cancer... next to smoking, of course... is somewhat misleading, to say the least.   Take as an example these two somewhat confusing quotes from the public summary of the EPA report, Biological Effects of Ionizing Radiation VI (BEIR VI)...

"The BEIR VI committee's preferred central estimates... are that about 1 in 10 or 1 in 7 of all lung cancer deaths-amounting to ... about 15,400 to 21,800 per year in the United States- can be attributed to radon among ever-smokers and never-smokers together."

"The number of radon-related lung cancer deaths resulting from (our analysis) could be as low as 3000 or as high as 32,000.  Most of the radon-related lung cancers occur among ever-smokers, and because of the synergism between smoking and radon, many of the cancers in ever-smokers could be prevented by either tobacco control or reduction of radon exposure."

No smoking sign"Ever-smokers" is a group that includes anyone who has ever smoked, regardless how long they smoked or how long ago they quit.  The "never-smokers" are... never smokers.  The first quote uses obviously higher average numbers and is a gift to the radon abatement industry.  This is a frightening figure, and given without explanation could be used as a tool to empty homeowner's wallets.  However, the second quote brings the first into perspective.  It indicates that most radon cancer deaths can be laid at the feet of "big tobacco", not "big radon".  The fact that the first quote would never lead you to believe that even the researchers doubted 15,400 as the low estimate for deaths.  The oddest thing about these quotes, however, is that they appear within the same paragraph!

Even the studies concerning uranium miners and their exposure to radon are not realistically applied to homeowners.  First, the miners were engaged in heavy physical labor, causing labored breathing and the commensurate deeper inhalation of radioactive dust.  Secondly, the levels of dust in the mines were far above the common dust levels in homes, making exposure comparisons difficult if not impossible.

As I see it, the obvious but unstated conclusion of the EPA's BEIR VI report is clear... they really don't know if there is a quantifiable risk to healthy people from the levels of radon they suggest are dangerous!  But the truth continues to be elusive, as the more easily accessible statements on radon's effects are more dire, with no equivocation. Here, for example, are two  quotations from Sources of Information on Indoor Air Quality: Radon...

"There is no scientific doubt that Radon gas is a known human lung carcinogen. Prolonged exposure to high levels of Radon gas can cause lung cancer. Millions of homes and buildings contain high levels of radon gas. EPA's efforts are directed at locating the homes with high levels and encouraging remediation of them."

"(Radon is) estimated to contribute to between 7,000 and 30,000 lung cancer deaths each year. Smokers are at higher risk of developing radon-induced lung cancer."

It is almost as if the EPA is disturbed that it hasn't been able to get enough of the "goods" on radon to enact full-fledged regulation, so instead it uses fear by overstating the importance of skimpy evidence.  Unlike carbon monoxide, asbestos and lead, there is no "smoking gun"... firm biological evidence to unequivocally demonstrate low level radon exposure to be a meaningful hazard when separated from cigarette smoking.

One thing is unequivocal... radon does cause cancer.  Since the government has been unable to act specifically and/or forcefully... offering only guidelines... it is up to you to judge the risks based on your own length of exposure, your smoking habits and your overall lung health.  So it would be wise to know the truth... test your home for radon!!

Facing the truth... how to test your home for radon

The method of choice for both the professional and the homeowner is the simple radon test kit.  The kit, a charcoal-filled canister, is placed in the lowest level of the home.  The testing should be done in the lowest "living area" of the home.  However, in most cases the basement is the room tested since it is the most susceptible to radon infiltration, even if it is not used as living space.   Because air movement affects the results of the test, the test kit should be located away from doors and windows where the air is mostly still.  Once the test time period is over, the kit is sent to the manufacturer for evaluation.  The results are returned to the homeowner by mail.

There are different types of radon test kits for different circumstances.   For example, the standard test kit is placed for 4 to 7 days, though some kits can be used for up to 90 days to obtain a better average reading.  The longer the testing period, the more accurate the results!  If this short-term test is positive... over 4 pCi/L, a longer follow-up test of from 90 days to one year is recommended.  There is also a special testing protocol for realtors who need a quick turnaround in their tests for prospective buyers.  These kits consist of two charcoal canisters and shortens the testing time to under 4 days.

Discount-priced radon kits are available online or, if you prefer, at most hardware and home stores. For those of you into high technology, there are sophisticated electronic radon testing monitors designed for continuous professional use.  They provide the professional inspector with sophisticated printouts of radon infiltration over time.   Some of these monitors can even fax the test results directly from the testing location to the inspector for evaluation!

Mitigation... removing radon from your home

Once you have tested your home, you will have to make a decision as to what type of action you will take. That is why you should have some basic knowledge of the types of radon mitigation (removal) techniques available.  As you will see, some are inexpensive and some are costly.

Knowing that the data relating radon to disease at the Federal threshold of 4 pCi/L is not very strong may not help you escape the financial consequences of a marginally high radon level in your home.   As mentioned at the beginning of this article, many long-time homeowners' first contact with the radon controversy is when they sell their home.  If a home inspector finds a level of over 4 pCi/L in your home, his recommendations for radon mitigation will be taken very seriously by your prospective home buyer.  Even if this disclosure doesn't immediately nix the sale, it will require you to take some action to save the deal... either mitigation or negotiation!

There are a number of methods of lowering radon levels depending on the design of your home, the existing level of radon in the air and the soil type around your foundation.  They vary widely in cost and complexity but many can be done by the homeowner... provided you have access to parts and equipment.  All radon mitigation techniques are based on three principles... keeping the radon out, removing it once it gets in, or diluting it with fresh air.

Sealing radon out can be the simplest solution.  Caulking basement floor cracks, coating basement walls or floors with waterproofing compounds, sealing the tops of open drains, installing caps on sump pump holes and covering bare crawlspace floors with plastic are a few techniques that can dramatically lower radon levels.   Curiously enough, the same methods that lower moisture levels in basements and crawlspaces can also lower radon levels.

Removing radon is a bit more complex and can have a greater effect on your home's environment.  One popular mitigation method uses a low volume ventilation fan which pumps air from beneath the basement floor or slab (via plastic pipe) to a vent located at the roof line.  Another method increases the pressure of the air beneath the basement concrete floor using a fan to blow outside air beneath it.  This additional pressure drives the radon gas away from the slab and foundation.  Both of these methods can be effective but both can cause increased air infiltration into the home from the outside due to negative pressure produced by the fan.  In other words, the air forced out by the fan must be replaced from somewhere... usually by outside air leakage around windows and doors.  Increased fuel costs for heating and cooling are often an unwelcome side effect of these methods.

Some variations include drawing radon from beneath plastic tarps laid across unfinished dirt floors, letting existing basement drainage pipes or sump holes double as radon collectors by attaching exhaust fans to them, and installing powered vents in the air spaces within concrete block foundations.  Again, the extent of the radon problem, the entry point and the design of the home will dictate the best solution.

Diluting the radon gas is the third method of mitigation.  This is not an economical whole-house solution because of increased heating or cooling costs.  It is well suited to unused basements and crawlspaces that can be isolated from the living area of your home by the deft use of vapor barriers and insulation.

After the mitigation is completed, a retest of the area is necessary to determine if the method chosen was successful.

Do-it-yourself vs. professional radon mitigation

The National Radon Proficiency Program was established by the EPA to certify radon specialists in testing and mitigation.  Unfortunately, this program has lapsed due to lack of funding, and the last incarnation of the list will be available online only  until September of 1999.  In my opinion, there is no reason why you could not install mitigation equipment yourself and save yourself a small fortune.  Equipment manufacturers will supply all the information you need to install the equipment properly.  However, it may be wise to get a specialist to evaluate your problem and make recommendations so that you don't make any expensive mistakes.

By the way, I never finished the Stanley Watras story. He eventually started a radon testing company out of his home in Boyertown PA.  Reports indicate that he considers his work "therapeutic".

There is a lot more information on-line...

If I have only whetted your appetite, feel free to visit these highly informative sites.  Be prepared for a lot of technical data. However, the reports are well written and should answer most of your remaining questions.

Radon in Earth, Air, and Water is supported by the US Geological Survey at   They have links to most of the major radon sites, and also a larger version of the geological map of the US showing average radon levels throughout the United States.

Facts Concerning Environmental Radon, from the Journal of Nuclear Medicine, Vol. 35, No. 2; Feb 1994, at   This is a very balanced research effort that covers all facets of radon research, with plenty of technospeak and tables!

Radon Mitigation Strategies, reproduced in part from The Journal of Nuclear Medicine, Vol. 35, No. 2; Feb 1994 and appearing on the Idaho State University Physics Department Web site, lists various mitigation methods, with both estimated costs and effectiveness.  Find it at .

Biological Effects of Ionizing Radiation (BEIR) VI Report: "The Health Effects of Exposure to Indoor Radon" Unfortunately, the full report is not available online.  A good summary of the report is available at

Sources of Information on Indoor Air Quality: Radon gives the official EPA position on the radon issue.  Read it yourself and make up your own mind... at, at  is a commercial site that has lots of valuable radon information, especially concerning testing and mitigation.  They also have a line of very reasonably priced radon test canisters for do-it-yourself testing.

Infiltec, at is an online supplier of just about any radon related product you will ever need.   Just visiting their site is a radon mitigation education in itself!

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