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Radon



Radon - A Brief Discussion

Caoimhín P. Connell
Forensic Industrial Hygienist

Prelude

A large portion of the general population is under the misconception that the frequently published risks associated with radon are well accepted scientific facts. In reality, the vast majority of well designed studies do not support US EPA policies or Radon Industry positions that exposures to indoor radon pose a significant threat to health.

One often hears: "Radon is a proven carcinogen." This is a true statement. Also one often hears: "All houses contain radon." This too is a true statement. Similarly, two related sentences are : "Benzene is a proven carcinogen." (True) And: "All houses contain benzene." (Also true).

So why is the comment about benzene pertinent to the conversation about radon? Because both radon and benzene are proven carcinogens, both are ubiquitous in residential indoor air, and both are present at concentrations too low to be a health hazard.

In the 1980s, the US Environmental Protection Agency began a radon scare campaign that used false information, strict mental reservations and broad mental reservations.82

The scare campaign received world-wide condemnation from the Global Scientific community. The EPA intentionally fabricated some of its information, and formally requested that authors refrain from providing all the pertinent information to the US Public. Although the EPA scaled back on its heavy handed rhetoric, to this very day, it has made it clear that Public Policy and Federal grants and financial allocations are much more important than facts. It is almost exclusively the US EPA that drives the multi-billion dollar "radon fright" train in the US.

In toxicology, we have a paradigm known as "The Wisdom of Paracelsus." According to this paradigm, "the dose makes the poison" and for many compounds, as the exposure increases, so too increases the dose, and therefore, so too increases the probability of a deleterious effect. This is known as the "dose-response curve." Sometimes the dose-response curve is a simple function of dose, and sometimes the dose-response curve is convoluted. A simple example would be a life saving prescription medication. Taken at too low a dose, the medication may have no effect; taken within the therapeutic window, the medication has a beneficial effect and when overdosed, the medication may have a lethal effect. Toxicologically, "dose" is the amount of material taken into the body, per unit body weight per day. For all compounds, there is a dose (and therefore a concentration), below which there is no known effect. This is known as the "No Observable Effect Level" (the NOEL is sometimes stated as the "No Observable Adverse Effect Level, or NOAEL.)

Some entities, such as the essential vitamin, niacin, have a convoluted dose-response curve. Without a certain amount of niacin, humans fail to flourish. At the right amount, niacin is beneficial, and at levels too high, niacin can kill.

Radon is not magical. There is a dose above which we begin to see the risk of lung cancer increase, and as we increase that dose, the risk too increases. Paradoxically, however, at very high doses, the risk goes down, not up. Similarly, there is a dose at which there is an apparent beneficial effect, and the risk of lung cancer is less than those people with "no" radon exposure. This effect is known as "hormesis." As it turns out, the concentrations of radon normally encountered in residential settings is in this category, and the best of scientific studies show that residential radon is not only not harmful, but appears to impart an hormetic effect.1 To date (in 2021), there are no epidemiological studies that reliably demonstrate a positive dose - response relationship between normal residential radon concentrations and the incidence of lung cancer. 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12

Furthermore, the majority of reliable studies that have thus far been performed indicate that, at concentrations typically seen in homes, as the level of radon increases, the risk of lung cancer goes down, not up. 13, 14, 61,

Ultimately what we do know is that, at the concentrations of radon typically seen in residences, the risk is roughly the same for radon as it is for other indoor air contaminants15 and if residential radon does increase the risk of lung cancer, then between 90% and 92% of those deaths are in smokers16, 17, 18 whose overwhelming probability of contracting lung cancer is from cigarette smoking. There is almost no scientifically valid evidence to indicate that radon concentrations, as typically observed in homes poses a measurable risk to nonsmokers.

The following section is a brief discussion of how radon occurs and the science-based risks associated with radon exposure.

In a separate discussion, we have also reviewed some of the commonly cited literature and you can read those reviews by clicking, here. At the end of this discussion, there are links to a two-hour lecture on radon in four parts.


Contents

Radon Occurrence

Radon And Health

Radon And Risk

Radon And Smoking

EPA Guidelines And Regulations

Radon Entry Into Buildings

Analysis Techniques

Charcoal Canisters

Alpha-Track Monitors

Continuous Working Level Meters (CWLMS)

Mitigation Techniques

Ventilation

Filtration Devices

Air Movement Device: Ceiling Fans

Sealing Floor And Foundation Wall Cracks

Positive Pressure

Sub-Slab Depressurization (SSD)

Educational Videos


Radon Occurrence

Throughout the entire Earth, the naturally occurring element uranium is found in at least trace amounts. This element is naturally radioactive and with time, the uranium decays into several other elements (called "daughters"), one at a time. Each time a transformation into a new element takes place, the atom is said to undergo "decay." During each decay, energy is released from the atom. The released energy is collectively given the term "ionizing radiation" and the atom is said to exhibit "radioactivity." The list of subsequent daughter products is known as the "decay chain."

Along this decay chain, one of the elements that is produced is the naturally occurring material called radon. Radon is unique from the other uranium decay products because it is a gas and as a gas, it is capable of migrating from the location of the original uranium atom into the surrounding soil gas. Worldwide, an average of about two radon atoms are emitted from every square centimeter of soil everywhere on the Earth every second of every day19. It is for that reason that virtually every house on the planet always has had radon, and will always have radon occurring in the home. Humans have been breathing radon gas since the dawn of Man.

Radon and Health

When radon decays, it too produces a decay chain, with its own daughters. During its decay, it releases a "large" atomic alpha particle and the atom is transmuted into polonium. An alpha particle is essentially an helium atom stripped of its electrons. It is at this point that the real hazards associated with radon are encountered. For it is not the radon which is responsible for the health problems, but rather the short lived radon daughters (SLRDs) and their decay products, such as the alpha particles. The radon may be thought of merely a source and a vehicle for the SLRDs.

There are several different kinds (isotopes) of naturally occurring radon. Typically, when we speak of radon, we are speaking of radon 222 which has an half life of 3.8 days. This means that if a volume of radon is sealed into a container and left on its own, half of the radon will decay into SLRDs and be gone in four days. After eight days, only 25% of the original will remain and after 12 days just 12.5% of the original ... and so forth, until, after an appropriate time, just a few atoms remain. However, because of a peculiar trick of physics, proving that God has a sense of humor, the last radon atom may never decay and there exists a finite probability that it could last indefinitely...

Once the radon atom decays, it subsequently undergoes four rapid decays starting with polonium 218 which decays into lead 214, which decays into bismuth 214, which decays into polonium 214. Each of these daughters has a half life of less than 30 minutes (the polonium 214 has a half life of only 0.00016 seconds). Furthermore, the daughters are electrically charged. The SLRDs are measured in units called Working Levels (WL). The significance of these units will be discussed later.

During each decay, at least one of three types of ionizing radiation are emitted by the SLRDs: alpha, beta and gamma. The alpha particle is easily stopped by a single piece of paper or layer of clothing. The fact that it is easily stopped speaks to the issue of its "linear energy transfer" (or LET). Since the alpha particle is large and easily stopped, the alpha particle transfers virtually all of its energy to the material which has stopped the particle. Beta particles have less probability of being stopped and impart less energy into the stopping material. The gamma radiation is similar to X-rays and has an even lower probability of being stopped.

Since the radon is airborne, these daughters have a high probability of being airborne. If the daughters are inside the lung when they decay, the lining of the lung wall becomes the stopping material. Since the alveolar cells of the lung wall do not have a significant protective coating, an alpha particle can collide with the live cell, imparting an enormous amount of energy to the cell, possibly disrupting the DNA within the cell. If the body's DNA repair mechanisms fail, the cell may encode improper information or may "dedifferentiate"; this is the interaction which is thought to initiate the cancers associated with the SLRDs.

When a daughter is airborne, it has an electrical charge associated with it and it has an higher probability to adhere to other airborne particulates and dust. When the daughters adhere to airborne particulates, it is said to be "attached." An inhaled attached daughter has only about a 3% chance of adhering to the lung lining. An inhaled unattached daughter, on the other hand, has a 50% chance of striking and adhering to the lung wall19; increasing the chances of a an alpha particle/cell collision. Ironically, where dust levels are high, the risks from elevated radon are lower than in dust free areas with the same radon level. It is for this reason, home-based air filters may remove the attached SLRD from the breathable air, but ironically increase the risk associated with newly introduced SLRDs (that sounds contradictory at first, but give it some thought).

Airborne SLRDs are constantly becoming attached to a walls, tables, chairs, carpets and other non-respirable objects. When this occurs, it is said the SLRDs "plate-out." Plate-out effectively removes the SLRD from inhalation exposure and thereby reduces the hazard (and risk) associated with a specific radon concentration without reducing the radon itself. This phenomena is the basis of one of the lesser known "radon" reduction techniques.

Radon and Risk

Industrial Hygienists, in general, are engaged in protection of humans against the harmful effects of ionizing (and nonionizing radiation). The specialized field of managing ionizing radiation is known as "Health Physics" and the job of the Health Physicist is to manage the beneficial use of ionizing radiation while protecting workers and the public from potential hazards. Although political organizations (such as the US EPA) publish a variety of statements of elevated risk, to date there are no scientific studies that have ever actually shown that radon gas, as typically seen in houses, increases the risk of cancer to nonsmokers, and there is questionable data related to smokers. To be clear: There are NO valid studies that have conclusively demonstrated that typical residential exposures to radon increase the risk of cancer at all. In fact, all of the valid studies performed thus far show one of two things: 1) No risk and/or 2) a decreasing risk of cancer.

This view is reflected in a position statement issued by the Health Physics Society, the premier Health Physics organization in the US. According to the position statement issued by the Health Physics Society21, for doses below 100 mSv (10 rem)

. ..risks of health effects are either too small to be observed or are non-existent."

In a May, 2016 revision 22 the HPS reiterates that

Substantial and convincing scientific data show evidence of health effects following high-dose exposures (many multiples of natural background). However, below levels of about 100 mSv above background from all sources combined, the observed radiation effects in people are not statistically different from zero.

So, just how hazardous is radon? Well, the above referenced document notes that the average US annual equivalent dose from natural background radiation is only about 3 mSv.

We have to remember that there are degrees of exposure, ranging from massive doses seen in miners who also inhale other contaminants, to minimal, negligible doses seen in residential scenarios. The "hazard" (risk) is incumbent on the dose received, and the duration of the received dose, not on some absolute "harm" associated with the radioactive gas at any dose. Elevated levels of radon (and thus the SLRDs) are unquestionably a significant health hazard, but similarly, we simply do not see those kinds of elevated levels in homes, and at concentrations of radon seen in residences, there appears to be no elevated risk (and many studies show the risk of cancer is actually is lower in an house with a little radon than in an house with no radon.)

So the question really is not "Is radon dangerous" but rather, how "high" is "elevated"? Unfortunately, as so often happens in the realm of public policy, the science has been perverted in an effort to promote a political agenda. A more detailed discussion of how science gets high-jacked can be found by clicking here.

Further, is the total accumulative life-time dose or the dose rate more important? Recent studies are answering these questions and demonstrating that radon in residential settings is not nearly the cause for alarm originally proffered by politically motivated governmental agencies or financially motivated radon testing and mitigation practitioners.

In the EPA and National Research Council (NRC) risk estimates, the units of exposure are Working Level Months (WLM). One Working Level is defined as any combination of short lived daughters in one liter of air which will ultimately release 1.3E5 MeV (million electron volts) of alpha by decay through polonium 214. Therefore a known concentration of radon has a specific "potential alpha energy concentration" (called the PAEC).

A somewhat more simple version (although less precise) is that a Working Level is a measurement of SLRDs which are in equilibrium with 100 pico Curies per liter of air (pCi/l); in this context, one pCi/l is not equal to one pCi/l in a house. That is a radon concentration expressed in pCi/l derived from WLs in risk estimates are not the same as radon concentrations expressed in pCi/l when measured by a home inspector or other "radon mitigation" service.

Equilibrium is said to have been reached when the maximum concentration of SLRDs has been reached. The ratio of the activity of the SLRDs to the activity of the radon gas is called the Equilibration Ratio (ER). Equilibrium usually occurs in about three to four hours. When an individual receives a dose of one WL in 170 hours (a miner's month), the exposure then becomes called a "working level month" or WLM.

The EPA guidelines for measuring radon were aimed primarily at homeowners (and cannot actually measure radon exposures), and therefore, a more simple version of WLs was needed to communicate radon concentrations to the general public. Therefore, the EPA invented a new unit of measurement and rather complicated the radon issue by using existing units, but applying different meanings to those units.

The EPA evaluated actual ERs between radon gas and SLRDs. By actually measuring the radon gas (which is very difficult, expensive and never done by residential radon measurement services), one can derive the PAEC, an upper limit for the SLRDs. Typically, ERs range from 0.3 to 0.7 23. An ER of exactly 1.0 is never seen because: 1) radon daughters are removed from buildings at different rates; 2) some SLRDs will plate-out while the radon remains airborne; and 3) newly infiltrated radon has not yet decayed.

The EPA arbitrarily decided that an ER of 0.5 represented what it felt would be a typical ER for a home and this became the basis upon which the EPA "pCi/l" was derived (which is why the EPA "pCi/l" cannot necessarily be compared with real pCi/l units). Although this selection has been heavily criticized by many scientists and in some journals such as the Journal of the American Industrial Hygiene Association, the ER of 0.5 is still used by the radon mitigation industry. Therefore, assuming an ER of 0.5, one WL is equal to about 200 pCi/l and not 100 as previously referenced.

Therefore, one begins to see the games that can be played by adjusting the numbers, but keeping the units of expressing the concentrations the same. This "numbers game" is at the heart of EPA risk models.

An unusually low ER in a home (say 0.3) would indicate a particularly dusty area (such as would be found in a home by a dirt road, for example) or a home that burned candles; an high ER (say 0.7) may indicate a particularly still area, an area filtered by a filtration system or particularly "dead" areas such as those rooms found in basements or storerooms.

The ultrafine particle faction of indoor air will significantly alter the ER, and indoor ultrafine particle concentrations are typically much higher in urban areas than suburban areas.

In one study 24, upon which the US EPA heavily relies, evidence involving miners indicated that at levels as low as 80 WLM, the risk of death from lung cancer was very high and the risk increased to 50% chance of death from lung cancer at even higher levels. In that study, the lowest measured exposure was 80 WLM. In fact, in that very important study, the EPA didn't actually measure a very large percentage of the exposed population or miners to determine what their exposure actually was. Instead the EPA states 25

Exposure in the U.S. cohort is poorly known; cumulative WLM (CWLM) are calculated from measured radon levels for only 10.3 percent of the miners...and guesswork is used for about 53.6 percent of the miners.

Guesswork? Let's look at that again:

Exposure in the U.S. cohort is poorly known; cumulative WLM (CWLM) are calculated from measured radon levels for only 10.3 percent of the miners...and guesswork is used for about 53.6 percent of the miners.

That's right, guesswork formed the basis of the majority of the estimates. The "numbers game" gets messier and messier. If one is allowed to use guesswork without challenge, where could this lead?

Philosophy and Science

Sit down before a fact as a little child, be prepared to give up every preconceived notion, follow humbly wherever and to whatever abysses nature leads, or you shall learn nothing. - Thomas Huxley, 1860 57

Undeniably, the very underpinnings of "science" is a philosophical position, tacit or expressed. Never in history has science not been driven by a philosophical position. However, scientists should be committed to allowing the data to speak for itself, and following that data where it may lead. In the real world, this seldom happens.58 and scientists are particularly notorious for resisting science.59.

Before the EPA got into the radon game, the US Department of Energy was the US's leading research group on radon exposures. Through political chicanery, the DOE was left out in the cold, and the Federal Government put the EPA in the driver's seat. This marked a paradigm shift away from valid science into the murky waters of politically motivated public policy and the DOE knew it:74

The CDC is included by the EPA to add credibility on the health protection issues. On the other hand, DOE and other active radon research agencies, e.g. The National Institutes of Environmental Health Science and (NIEHS) and the National Cancer Institute (NCI), disagree with the EPA/CDC position. All involved federal agencies should participate in policy review and review of the science, if any, supporting the EPA policies.

It is an objective fact that the risk associated with SLRDs is a complex relationship with dose. However, the US EPA 60 and trade organizations, such as the "Canadian Association of Radon Scientists and Technologists" reject science in favor of a dogmatic policy statement and a philosophical proposition that there is no known safe level of exposure to radon. There is no foundational science to support the dogmatic philosophy.

To satisfy the unsupported philosophical end adopted by the US EPA (and many other groups), they accepted a model known as the "Linear, No-Threshold, Dose-Response Curve." This model begins with the a priori rule, that even one solitary atom of radon, present in a room the size of the Earth will carry a quantifiable risk of dying from lung cancer. To say that the proposition is laughable, would be an insult to comedians. The model is graphically represented below, wherein the dose-risk curve is artificially forced through "zero" at one atom of radon, on the planet Earth.

Linear, NT, Dose-Response Curve
It has been argued elsewhere 61 that the linear, no threshold dose response presumption was developed in the 1930s in the absence of supporting data as a conservative approach to safety. However, over the last 90 years, we have made huge advances in our understanding of radiation, Health Physics, biology and epidemiology, and it make little sense to dogmatically cling to a 90 year old philosophy as the basis of a public health policy.

We now better understand programmed cell death, DNA repair mechanisms, and an host of other pathways by which the body fights cancer, maintains homeostasis and health. Accordingly, we also understand the adaptive nature of the body to insults, including radiation. As a result of this better understanding, we now better understand why the objective science does not support the EPA model predictions - simply put, the Linear, No Threshold, Dose-Response Curve is a myth. In fact, even from the early 1970s, we have known it was a myth, and the scientific world has been battling the policy world of the EPA (who always knew it was a myth) ever since.

William D. Ruckelshaus was the first Administrator of the newly formed EPA in 1970 and he returned to that position in 1983 as the fifth Administrator of the EPA. Immediately after he left the EPA he wrote a profoundly revealing essay78 which revealed the almost religious aspect of the new "environmentalist" movement which was not based on science. Ruckelshaus notes that:

It became clear very early in the history of the EPA, however, that that our scientific base was sorely inadequate.

Ruckelshaus acknowledged that through sheer self-righteous certitude he and others in the movement were driven by ideology, not facts, and there was considerable tension between the regulators who were cock-sure of their opinions and the scientists who were invited to participate in confirming those desired outcomes:

Policy makers, including me, have often deplored the tendency of scientific panels to engage in interminable debate rather than reach the agreement that was clearly indicated on the invitation.

Lacking the support of the scientific community, the EPA needed something that would take its place. In his discussion he laments that the EPA recognized that fear was a key component of the movement to manipulate the public:

People are afraid of these environmental risks, and fearful people have too often traded freedom for the promise of security.

Ruckelshaus admits that the "Linear, no-threshold, dose response" curve was adopted to satisfy the philosophical ends of the environmentalist movement but:

The environmentalist ethos, which is reflected in many of our environmental laws, and which requires that zero-risk levels of pollutant exposure be established, is thus shown to be an impossible goal for an industrial society as long as we retain the no-threshold model of carcinogenesis.

The inability of the no-threshold linear dose response to properly predict toxicological outcomes was similarly known to other areas of science. As chemophobia swept the societies of the northern hemisphere, Rodericks and Taylor acknowledged the problems of the linear no-threshold model in their 1983 paper on food safety.79

The effect of these conservative policies is to produce carcinogenic risk assessments that consistently overstate the true risk, sometimes substantially.

Although the EPA and other radon industry proponents continue to use the linear no-threshold model, (without which we would not see a risk), other researchers and organizations are becoming more vociferous and intolerable to the idea of continuously using "outdated science".80

In a 2019 letter from the EPA Science Advisory Board81 to the EPA's Administrator, the Science Advisory Board cautioned the Administrator that the Health Physics Society once again made its position on the no-threshold linear dose response explicitly clear:

"As a scientific organization of professionals who specialize in radiation safety, the HPS believes the EPA's reliance on the LNT model, especially at very low doses and dose rates, is inappropriate and can exaggerate the risk. Of most concern to the HPS is the EPA's extrapolation of the LNT model to calculate collective dose and the use of collective dose as a metric for risk." (Kirner 2017, Ring et al. 2017)(emphasis added) "The Health Physics Society advises against estimating health risks to people from exposures to ionizing radiation that are near or less than natural background levels, because statistical uncertainties at these low levels are great.

Accordingly, then as now, we have a better idea of how the body responds to radiation doses as shown in the idealized graph below:

Non Linear Dose-Response Curve

Adopted from Scott (2009) 62



In the above graphic, Scott et al, have identified the "X" axis as "dose" and the "Y" axis as "relative risk." A "RR=1" means there are no observed lung cancer cases above the normal expected occurrence; below that line there are fewer than expected lung cancer cases, and above the RR=1 line, the lung cancer incidence increases with increasing dose. Importantly, the doses in the range of "Zone of Maximal Protection" are those most typically seen in residential settings.

The "Phantom Risk" zone, is where the EPA and Radon Mitigation Industry operates.

Non Linear Dose-Response Curve

Adopted from Scott (2009) 62



In Scott's paper, the radon concentrations were expressed in Becquerels per cubic meter (Bq/m3). The "Adjusted Odds Ratio" for lung cancer was derived from the data presented in Thompson, 2008.63 The dashed curves represent the 95% confidence values reported by Thompson (ibid). The horizontal line marks an adjusted odds ratio of unity (no excessive cases for the study data set). Furthermore, it is well known (but poorly understood why) at even higher levels of radon than shown on either graph, (or more precisely SLRDs) the risk of death begins to actually decrease again26. The LNT model27 was issued in 1988 by the National Research Council and is called the BEIR IV report. BEIR is an acronym for "Biological Effects of Ionizing Radiation".

In fact, the linear model has long been known to be invalid28, and the EPA has long recognized that the linear model is invalid, but decided to use it anyway. In their 2003 risk estimates 29

The BEIR VI committee stated it adopted the linear no-threshold assumption "based on our current understanding of the mechanisms of radon-induced lung cancer," but even then the BEIR Committees recognized that this "understanding" is incomplete and that therefore the evidence for the assumption was not conclusive.

In fact, the linear model was not based on "current understanding of the mechanisms of radon-induced lung cancer," rather it is based on a voluntary adoption of a philosophical position that is traditionally used in risk estimation where there is no evidence of harm at the doses received.

Indeed, in the previously referenced position statement by the Health Physics Society, the authors explicitly state that qualitative assessments should NOT be made (since no risk is observed when this is done), and that, instead, a subjective philosophically-based risk assessment should be made exclusively based on the assumption of a linear model.

The assumed model has never been shown to be correct, and is scientifically accepted as incorrect. The Health Physics Society at the University of Michigan made the following observation: 29

There is, however, substantial scientific evidence that this model is an oversimplification of the dose-response relationship and results in an overestimation of health risks in the low dose range.

The statement continues with:

Radiogenic health effects (primarily cancer) are observed in humans only at doses in excess of 10 rem delivered at high dose rates. Below this dose, estimation of adverse health effects is speculative. Risk estimates that are used to predict health effect in exposed individuals or populations are based on epidemiological studies of well-defined populations (e. g. the Japanese survivors of the atomic bombings in 1945 and medical patients) exposed to relatively high doses delivered at high dose rates. Epidemiological studies have not demonstrated adverse health effects in individuals exposed to small doses (less the 10 rem) delivered in a period of many years.

This position is repeated throughout legitimate science, including US Governmental Laboratories such as the University of California, Lawrence Berkley National Laboratory which concluded: 30

Despite being widely accepted as a guideline in setting standards for protecting public health, the linearity hypothesis is not firmly established as an expression of scientific knowledge.

Other authors have been more succinct:30.

The linear no-threshold model of radiogenic cancer is false. Because it fails empirically against superior empiricism, it becomes misinformation and opinion, not knowledge, but it is still advocated because it lends contentment to believers. We can no longer tolerate the universal application of LNT misinformation when, as people of science, we are about helping, not harming, humanity.

Therein lies the crux of the "controversy:" On one side of the controversy are political lobbyists who want to show a risk to help out the multi-billion dollar radon testing and mitigation industry arbitrarily using invalid risk models, and on the other side of the "controversy" we have scientists saying "There is no evidence of risk."

The EPA, being a political organization, ignored the science behind the biological effects and used an unsupported assumption that the health effects from the radon could be extrapolated in a linear fashion from the lowest radon concentration in the study (2,720,000 pCi/l-hour) to those levels found in homes. This linear "dose-response" assumption was made even though there was considerable uncertainty for the validity of the extrapolation at lower levels of SLRDs.

The lowest radon concentration in the BEIR IV study (2,720,000 pCi/l-hour) was typically received by the miners over a five year period 31. Yet the EPA and NRC take this five year exposure and spread it out over the course of 70 years, and assume that an individual will spend 18 hours per day in their home, 365 days per year for 70 years. They also assume the "home" is situated in an underground mine, and that the occupants smoke cigarettes in their underground home.

This equates to an accumulative radon concentration of about 6 pCi/l in the home. It is not known, at this time, if it is valid to assume that only the accumulative dose, rather than the dose rate is the sole factor for determining risk. In its model, the EPA, eliminated the "dose-rate-effectiveness factor" from the quality factor which is usually attributed for alpha particles.

Although it is a generally held industrial hygiene principal, that fractionation of the dose over a long period of time lessens the overall effect, this concept is not always accepted for carcinogens (tumor initiators), such as ionizing radiation. For carcinogens, fractionation of the dose may actually increase the overall risk 32.

The NRC understood the limitations of the study and concluded 33...

In summary, a number of sources of uncertainty may substantially affect the committee's risk projections; the magnitude of uncertainty associated with each of these sources cannot readily be quantified. Accordingly, the committee acknowledges that the total uncertainty in its risk projections is large.

A later study 34 (referred to as the Cohen Study), which is one of the largest studies, incorporated about 33% of the counties in the U.S. and looked at the issue of the linear, no-threshold dose-risk relationship used by the EPA. In this study, a least squares linear regression of lung cancer rates vs. mean radon levels gave a negative correlation between death and exposure levels. In other words, the higher the radon level in the county, the lower the death rate from lung cancer was for the community. The result was not due to questionable interpretation of shaky statistics; each of the studies showed a negative correlation with slopes of not less than seven standard deviations (and sometimes greater than 10 standard deviations) greater than zero.

This study, known as an "ecological" epidemiological study, looks at relationships between exposure groups and mortality rates. Ecological epidemiological studies carry less weight than studies based on individuals where the actual exposures are known and the study cohort is compared to an unexposed group. In an ecological study, the person who dies may not have been the person who was exposed to the insult. Additionally, ecological studies tend to be more susceptible to confounders. Nevertheless, the author of the Cohen Study maintained that in a study on linear no-threshold relationships, this limitation is not considered to be applicable since the mortality rate depends directly on the average exposure.

Several other independent studies also looked at mortality rates vs. mean radon concentrations and have found similar negative correlations.

Indeed, buried deep within the US EPA documents, and worded in a very complex way, the EPA recognizes that as residential radon concentrations go up, the cancer rates go down. However, the casual reader, thumbing through the EPA risk discussion, would not likely recognize this admission since the EPA made the statement in a purposely very convoluted and confusing manner wherein they state:

Unlike what was found with the more limited BEIR IV and ICRP analyses, the BEIR VI committee was able to conclude that the ERR per WLM increased with decreasing exposure rate or with increasing exposure duration (holding cumulative exposure constant).

We begin to see that the "numbers game" works best when we use language and syntax that no rational member of the general public can actually understand.

At least five U.S. State sponsored projects have performed similar ecological epidemiological studies; four have concluded that low levels of radon, such as those found in the average home, are not harmful (show a negative correlation) and the sixth study indicated a very slight (less than one standard deviation) positive slope, indicating some risk at low level.

Epidemiological studies in other radiological settings have similarly observed evidence contrary to fear-based public health policies. For example, an epidemiological study was conducted for a total of 95,673 workers in combined nuclear industry facilities (Hanford, Oak Ridge, and Rocky Flats, three for sites in the UK, and one in Canada).

60% of the workers, whose radiological exposures were very well defined, received doses greater than 10 mSv (1 rem). The comprehensive results for all cancers taken together showed a very slight decrease in cancer rate with increasing dose. As with all studies, statistical issues can be raised, regarding the results, however, unquestionably was the fact that even at these doses, a clear-cut unambiguous risk was not observed, and the risk appeared to decrease with increasing dose, or decreasing dose rate.

In a US Government Publication 35concerning radon, the following statement is made:

Currently there is very little information about...the health effects associated with exposures to radon at levels believed to be commonly encountered by the public. The only human data available for predicting the risks to the public are studies examining the health effects of exposure to radon and its progeny in underground miners. This information would be appropriate for predicting the risks to the public if everyone was a miner, everyone lived in mines, and a large fraction of the general population smoked cigarettes.

Clearly, then, the models used for the estimation of risk are inappropriate since the average American, Canadian, or Western European is not a miner, we do not live in mines, and we do not have similar exposures. The same document then goes on to state:

Depending on the set of assumptions used, the estimated values for lung cancer rates from environmental exposure to radon currently range from quite small to as large as 25% of the total annual lung cancer deaths in the United States.

Ongoing studies that employ more realistic models fail to find any evidence that the risk of death from cancer induced by residential radon exposure is even noteworthy. Furthermore, in modern science, it has been generally assumed that virtually all effects of ionizing radiation result in detrimental effects. However, over the past decades, reports in scientific literature seem to suggest that that low-dose ionizing radiation is not only a harmless agent but often has a beneficial or "hormetic" effect.

The same uncertainties plague chronic-exposure risk assessments for other forms of low level radiation; and the concept of ALARA (As Low As Reasonably Achievable) is used to control those forms of radiation. The definition of ALARA is found in the United States Code of Federal Regulations, 36 and is essentially defined as follows:

A policy of reducing personal and environmental radiation exposures to the lowest level commensurate with sound economics, available technology, and good operating procedures.

Radon And Smoking

Not normally discussed is the overwhelmingly important association of cigarette smoking and radon exposure.

Emphasized everywhere in the Scientific World and the World in general is that fact, the effects of radon, even using the worst-case scenario of the US EPA, is almost exclusively a smoking problem, not a radiation problem. There is only one place where this important association is not emphasized - in the US Environmental Protection Agency.

In fact, the US EPA has explicitly and repeatedly advised it's "partners" to intentionally provide misleading information. For example, in 1991, John Garrison, the Managing Director of the American Lung Association addressing its "partnership" with the US EPA stressed the importance to "...speak with one voice to the public..." 64 along with the EPA, by hiding important information. Speaking to the various scientists, physicians and journalists at the symposium, Mr. Garrison said: "...in your communications with the media and with the public, I urge you not to dwell on the doubts over radon, but on the legitimate dangers of long term exposure." The problem is, of course, that there is no demonstrable legitimate danger, and in fact, one of the great ironies of Mr. Garrison's revealing statement is that it was at this very symposium, that Dr. Bernard Cohen with the University of Pittsburgh, presented his paper which discussed the uncomfortable fact that the EPA's model epidemiological predictions were not just failing to materialize, they were in fact exactly the opposite of what was being observed.

Dr. Cohen's mathematical analysis65 of the EPA model showed that it was completely wrong, and that as residential radon concentrations went up, lung cancer deaths went down.

In summary, we find a gross and statistically undisputable discrepancy between the predictions of BEIR-IV and observed lung cancer rates in U.S. counties; the theory predicts a substantial increase in lung cancer mortality with increasing radon exposure, while observations corrected for smoking and a wide variety of potential socioeconomic confounding factors indicates a decrease...

Holding to honest science instead of policy philosophies, Dr. Cohen rightfully concluded:

If this discrepancy between theory and observation cannot be explained, the only rational alternative is to abandon the linear-no threshold theory, recognizing that it grossly over-estimates the cancer risk from low level radon.

Quoting nuclear physicist Philip Abelson, (co-discoverer of neptunium), 66 citing the EPA's document "Radon Media Campaign" the EPA recommended that the Ad Council "Eliminate unnecessary information" and "use strong and unsettling messages." In other words, says Dr. Abelson, "...don't inform them, scare them."

So why would Mr. Garrison with the American Lung Association say such things? Regarding the "partnership" with the American Lung Association it is important to note that in the US Department of Energy draft memorandum 73 the DOE addressed the problem of the Radon Reauthorization Act handing out monies to the EPA to provide financial assistance to non-profit interest groups to encourage radon testing and mitigation. In the memo, the Department of Energy notes:

This is a major and troubling provision - under this section EPA will continue to fund millions of dollars of "advocacy" money to the American Lung Association, the National Association of Counties, the radiation control officers, etc. Funds are provided for t-shirts, bumper stickers, media events, scare tactics, legislative support, and advocacy of EPA programs. This allows advocates to be quoted as "supporting EPA" position in radon press releases. These advocates also attack EPA critics.

The concern of the use of scare tactics by the EPA was echoed by Gun Astri Swedjemark, of the Swedish Radiation Protection Institute. Ms. Swedjemark, who has dedicated most of her life to the radon issue was appalled by the EPA's scare-campaign: "I have seen the campaign material by the Ad Council, and I found it terrible. You should not frighten people.67

One of the ways to "scare them" is to pretend that radon impacts children more than adults (not true), and that radon impacts smokers and non-smokers equally (also not true). Probably the biggest lie the EPA peddles is "...having radon in your home is like exposing your family to hundreds of chest X-Rays yearly." And that was said at a time when exposure from medical X-Ray machines was considerably greater than at the present time. But it was a lie when the EPA said it, and they knew it. The second biggest lie was that a radon concentration of 4 pCi/l was equivalent to smoking half a pack of cigarettes per day. Again, there was no science behind this claim.

In fact, the impact of radon on the public (if any at all), is associated almost exclusively with smokers.

William Nazaroff (Lawrence Berkley Laboratory) and Kevin Teichman (US EPA, Office of Research and Development), used the US EPA models and estimates and concluded that if one eliminates smoking, there is virtually no radon problem.68 They found that, using the EPA estimate of (1990) radon deaths of 16,000 only 3% of those deaths occurred in never-smokers. They stated that "Thus, according to these predictions, more than 90% of the lung cancer risk associated with radon could be controlled by eliminating smoking without any changes in radon concentrations."

So, we know that radon risk is primarily a risk of smokers69 and in fact, according to Epidemiologist Geoffrey Kabat, "A corollary of the overwhelming importance of smoking as the dominant cause of lung cancer is the fact that lung cancer occurring in lifetime non-smokers is so rare that it is difficult to determine how much of a risk, if any, average levels of domestic radon pose to those who have never smoked."70 Although the EPA has almost exclusively used the mining cohort for its death estimates from radon (most of whom smoked), we have virtually no data on low-level exposed miners who didn't smoke.71 With such scanty data, some researchers have turned to meta-analyses to look at the possible effects of radon on non-smokers. Darby-Hill et al72, for example, found that for never-smokers the cumulative absolute risk of lung cancer from radon by age 75 is virtually indistinguishable from zero (see below).

Cumulative absolute risk of death from lung cancer by age 75 years versus usual radon concentration at home for cigarette smokers and lifelong non-smokers.

For the above graphic, the authors state: "Cumulative absolute risk of death from lung cancer by age 75 years versus usual radon concentration at home for cigarette smokers and lifelong non-smokers. Plotted values calculated using relative risks for smoking from men in all studies combined, and absolute risks in lifelong non-smokers from US data for men and women combined. Areas of circles proportional to numbers of controls with usual radon levels in ranges <200, 200-399, 400-599, and [greater than or equal to] 600 Bq/m3."

Sometimes the EPA documents predicts 16,000 lung cancer deaths per year from radon, sometimes the EPA predicts 20,000 deaths per year from radon, and sometimes the EPA has predicted 30,000 deaths per year from radon. No one has been able to explain why this keeps changing.

But let's look at some simple math. Let's use the figure given in the 1986 "A Citizen's Guide to Radon: What It Is and What to Do About It" In the Citizen's Guide the EPA predicted 20,000 radon deaths. For the year the claim was made, 1986, there was an expected total of 130,000 lung cancer deaths. The Citizen's Guide noted that 85% of those 130,000 lung cancer deaths would be due to smoking; therefore 110,500 deaths due to smoking. That leaves 19,500 people from which 20,000 are going to die from radon. There aren't enough bodies. How can we have more deaths than people? Furthermore, even if the balance of deaths was 19,500 then that leaves no available deaths from lung cancer due to other causes such as asbestos, occupational exposures to carcinogens, genetic malformations, etc. The EPA just makes things up, and hopes the American People don't look too closely and don't ask questions.

EPA Guidelines and Regulations

When the EPA established its radon exposure levels, it actually was attempting to establish limits on the Working Level of the SLRDs. The "real" EPA guideline is 0.02 WL; assuming an ER of 0.5 (which, as we have already seen, is a made-up figure), this would equate to 4 pCi/l of radon. However, an ER of 0.5 may not be appropriate for all buildings.

As mentioned above, the EPA selection of the 0.02 WL limit was not based on health effects or other risk assessment models but rather on a general agreement that 0.02 WL was the lowest technically feasible level of reduction.

The EPA guideline is not law in the U.S., it pertains only to residential homes, and does not carry force of law (although it is a de facto standard upon which litigation may be supported). It is merely one political group's recommended level of reduction. The EPA does not have mandatory limits for radon for other types of buildings and does not prohibit levels of radon in excess of the 4 pCi/l threshold.

As already mentioned, the EPA homeowner's guidelines for measuring "radon" do not actually measure radon at all. An Industrial Hygienist or an Health Physicist would be laughed into obscurity if they used the EPA guidelines to perform actual human radiation exposure studies. This is because the EPA measurement guidelines have an extremely low confidence level in being able to actually determine a useable exposure value.

Individuals wishing to retain their EPA accreditation in the Radon Contractor Proficiency Program must comply with the EPA's politically derived position on radon (facts and good science notwithstanding), or face forced removal from the program by the EPA. Providing factual discussions on risk are not viewed by the EPA in a favorable light.

During an international scientific gathering, an internationally recognized health physicist was presenting his data that showed that lung cancer rates went down with increasing radon concentrations. The work was funded by the US EPA. A violent shouting match ensued when a U.S. EPA representative began throwing wads of paper at the scientist shouting "We didn't authorize you to say that!!"75

In fact, as already discussed, the data being presented by the scientist was exactly the same data now admitted in the 2003 EPA risk estimates. But the scientist wasn't presenting the findings in appropriate confusing language - and he wasn't playing the required "numbers game."


Radon Entry into Buildings

Most soil gas reaching the surface is quickly diluted by the surrounding air. In the event that a structure is built in or on top of the soil, the dilution of the radon does not take place as quickly, and the radon in the structure may accumulate.

Several factors govern the extent of how much radon will enter a building. The single most important factor is the local geology and surrounding soils. The immediate precursor to most radon gas is radium. (A very small contributor to the radon concentration is radon 226, also called thoron. The contribution of thoron is generally insignificant and will be ignored in this discussion).

The existence of even a small deposit of radium under a building will greatly influence the concentration of radon gas within the building. Micro geological formations such as local disturbances during construction, micro faults and rock out-croppings can significantly alter the radon concentration at the surface. An example of the extreme variability of radon was seen in one study 37 where one soil gas sample contained 250 pCi/l and a second sample taken at 10 meters distance contained 86,000 pCi/l. "Normal" indoor levels in the U.S 38 are typically about 1 pCi/l (using the EPA pCi/l, not the real pCi/l) which is 10 times greater than the outdoor concentrations of about 0.15 pCi/l.

When a building is constructed, pressure differentials between the interior of the building and the exterior of the building are inadvertently created, especially when there is a significant temperature difference between the interior of the building and the outdoors. This pressure differential, delta P (DP) is mostly due to a phenomenon known as the "Stack Effect". The building mimics an exhaust stack and is under negative pressure with regard to the surrounding environment including the atmosphere and the soil gas below the slab. Typically, the DP is greater toward the bottom portion of the building and is equalized near the top of the building.

To satisfy the negative pressure in the building, the net air movement toward the bottom of the building is from the outside of the building to the inside of the building. It has been estimated 39that as much as 20% of this infiltration comes from below ground level. This 20% infiltration accounts for between 80% and 90% of the total radon which enters the building.

In the early days of radon investigations, it was assumed that drafty houses would have less radon than "tight" houses. Additionally, it was assumed that houses with high exchange rates would have lower radon concentrations than houses with few air changes per hour. Contrary to expectations, studies performed thus far show that there is no correlation between "tightness" of a building and the radon concentration 40,41. Very low radon concentrations are commonly seen in very tight buildings and high levels are often seen in the leakiest of houses.

Therefore, the second most important factor in radon entry into buildings is the DP. Several studies have shown that a very strong correlation between DP and radon concentration exists. All things being equal, the greater the pressure differential, the higher the radon level.

Since most commercial buildings fitted with industrial heating, ventilation and air conditioning (HVAC) systems are designed to keep the structure at positive pressure, excessive radon levels in commercial buildings in the U.S. are rare even in "high radon" areas. Typically, the most successful radon reduction techniques are those which address the driving forces of the pressure differential.

Weather can also effect the DP. Generally speaking, when the outside air is cold and the interior of the building is warm, the DP is greater. When the wind blows, the DP is greater. Additionally, when the water table rises, such as following a recent rain, the soil gas pressure rises, increasing the DP. Other meteorological factors such as snow cover can also effect the radon concentrations in a building by creating a "cap" under which the radon can accumulate.

In the U.S., Britain and Sweden, the majority of the radon which enters a building is from the presence of radon in the soil gas. However, there are two other significant sources of radon- well water and building materials. For structures, which are serviced by well water, a significant contribution of indoor radon can be from the radon in well water. Worldwide 42, the average concentration of radon in surface water is about 10 pCi/l. In the U.S., the average private well-water contains about 750 pCi/l. Levels exceeding 20,000 pCi/l are not uncommon and this author (Connell) has seen references to levels exceeding 1.6 million pCi/l.

Due to radon's very high Henry's Law Constant, radon will quickly evolve from water when it is aspirated or exposed to the air. For this reason, processed city water is rarely seen as a contributing factor to the overall radon concentration in a building, since essentially all the radon has left the water in the predistribution processing. However, in well water, the water is not subject to the chlorination and aspiration processes and can be a significant contributor to the building's burden of radon. It is commonly quoted that a water radon concentration of between 6,000 and 10,000 pCi/l will increase the airborne radon concentration in a building by 1 pCi/l.

In a few isolated cases, decorative stone and other building materials have also been identified as being the single largest significant contributors to indoor radon concentrations. The building construction material called "granite" is usually a similar material called granodiorite. The granodiorite has been shown in some cases to be the sole source of radon in a structure. However, no studies have ever demonstrated that the radon contributed by these materials pose an health hazard.

ANALYSIS TECHNIQUES

The most common question we receive is "My radon level was measured at ___.___. How reliable is the number?"

It is important to begin by saying that none of the devices used in home inspection or real estate transactions actually measure radon. Each of the devices used by home inspectors and radon consultants measures some particular aspect associated with radon and then, using various assumptions and mathematical machinations, a "radon equivalent" number is generated. The protocols were not designed to be used to estimate annual human exposures to radon, and cannot, with validity or confidence produce radon exposure estimates.

The number reported during a short term test has a very low probability of actually representing the annual radon concentration in the home, and has virtually no utility in estimating the actual human exposure to radon or its SLRDs. Long term testing has a lower sampling error, but depending on the method, similarly cannot be used to estimate human exposures.

The interday and intraday variability of airborne concentrations of airborne contaminants exhibits a geometric standard deviation of between 1.2 and 2.5 GSD.43. This means that a single short term reading is virtually incapable of estimating the true annual radon concentration. The uncertainty for attempting to extrapolate the yearly radon concentration from a three to seven day sample, such as that probably used for the vast majority of "radon tests" is huge: about +/- 90% (at the 90% confidence level).44.

The error is due to the large fluctuations seen in radon concentrations at any point in time. The result of a "radon test" can change dramatically when any of the following parameters change:

A cycling air conditioner goes on or off
A cycling forced air furnace goes on (or off)
Barometric pressure fluctuations
Differences in indoor to outdoor temperatures
External doors in the structure are opened or closed
Internal doors in the structure are opened or closed
Macro-airborne particle changes (such as dust from a dirt road)
Phases of the moon
Recent rain
Relative humidity
Snow cover
Soil porosity at the time of the test
Solar loading on the structure
The amount of radon exposed in the underlying soil
Time of day
Time of year
Ultrafine airborne particle loading (such as burning a candle)
Water table levels
Wind direction changes
Wind speeds change
Windows in the structure are opened or closed

As such, the short term "radon" measurements have a huge error associated with them in extrapolating the long term concentrations. Depending on the type of device used by the home inspector, the result may only integrate the last 12 hours of a multiple day test.

To illustrate the sampling error of the short-term methods employed today let's imagine a single family, single structure two storey home with a partial dug-out basement, on city water, and with a forced air heating system.

Imagine our home has an actual true annual radon concentration of 47 pCi/l. Now, let's hire an home inspector to randomly test the property 21 times over the course of the year. The inspector produces 21 separate "lab reports" with the following results (expressed in pCi/l):


20
6
89
75
3
90
16
45
22
87
69
9
91
11
12
56
7
45
22
5

If we now analyze the validity of the results, we find that there is no statistically significant difference between the results of the tests. That is, each of the test results are valid and are all within the upper and lower 95% confidence intervals for the short term method employed. Therefore, based on the short term method used in real estate transactions, an house with a yearly "radon" concentration of say 47 pCi/l (as that given above) can give a reading of anywhere between 91 pCi/l and 2 pCi/l and still be "correct."

This author (Connell) purposely selected 47 pCi/l since that allows us to illustrate the variance without the use of decimal points. For example, if the house contained 4.7 pCi/L, the range of readings would be from 0.2 to 9.1; but as explained below, the number to the right of the decimal point is meaningless.

However, the example is borne out in real life. For example, Brenner (1989) reports76 a home where a living room sample yielded 6 pCi/L, and the same location 3 days later was 140 pCi/L. Even 90 day readings are not much better. 77

Since the number to the left of the decimal lacks confidence, how could the number to the right of the decimal have meaning? Imagine an agricultural inspector was asked to estimate the annual average weight of cows in a barn by measuring the cows over a three day period using the same precision as "radon" methodologies. Although during the three day period, there were 100 cows, the rancher moves cattle in and out, some of the cows are calves whose weight will increase rapidly over the next few months, and some are full grown, some are dairy and some are breeders, etc. But using the "radon method" of estimation, inspector reports that the annual average weight of 100 cows was EXACTLY 125,234.2392 pounds.

The inspector simply has no chance of being correct with such precision. Since the number to the left of the decimal point has low precision, to try to pretend that ANY number to the right of the decimal has any meaning is nonsense. At best, and with valid confidence and precision, one could estimate the annual weight of the cows as follows "You have about 60 tons of cows."

And so it is with radon readings. When we hear someone describe their "average" radon concentration as some value followed by a decimal point and another value, (such as five POINT two) it is meaningless. When someone has a reading of, say, 5.2 pCi/l it means just one thing: The actual yearly average radon concentration in the house is probably somewhere between 0.01 pCi/l and 20 pCi/l.

If the methods used cannot, with confidence, distinguish an annual exposure concentration of 91 pCi/l from a reading of 2 pCi/l how could they possibly be able to distinguish a reading of say 3.6 versus 4.2 pCi/l This misplaced trust in magical laboratory reports is what we call the "CSI effect."

Charcoal Canisters

The charcoal canister (CC) method of radon concentration estimation is the most widely used method of screening. Like virtually all other "radon measurement devices" the CC method does not actually measure radon but rather it measures the gamma radiation associated with the SLRDs. Several assumptions as to relative humidity, equilibration ratio, transient peaks and others are then incorporated in the final analysis.

There are several advantages of using the CC method. They are relatively cheap, usually costing about $25.00 to $40.00 The placement of charcoal canisters need no special training. Although the sampling error associated with the CC is very high, the analytical precision associated with the CC is very good. The charcoal canisters are inconspicuous, which allows for undisturbed sampling; and they are fast; sample periods can be a little as three days and results can be obtained within three or four hours.

There are some disadvantages associated with the CC as well. The uncertainty for attempting to extrapolate the yearly radon concentration from a five to seven day sample is huge: about +/- 90% (at the 90% confidence level) 45. For this reason, a single CC reading (or indeed several) cannot be used to estimate the annual radon exposure in a house. Also, charcoal canisters are susceptible to humidity changes. Often, the analyzing laboratory will assume a standard percent relative humidity and use that in their calculations.

The CCs are erroneously thought to integrate the radon concentration over the sample period (usually three to five days), but this is not quite true. The CC will bias the results to reflect the last 10 to 12 hours of sample time. Therefore, if during the last 12 hours of sampling time a rain storm has occurred, or the outside temperature has dropped or the wind was particularly strong, then it is likely that the results will be biased high. If on the other hand, the day was calm, unusually dry and warm, the results may be biased low.

Alpha-Track Monitors

Alpha-track monitors are typically small cylindrical containers (about 5 cm high) which contain a piece of plastic film. The opening to the cylinder is often covered with a dust cover. Filtered alpha-track devices always bias the results high.

During the decay of the radon and its SLRDs, the alpha radiation strikes the film and creates microscopic areas of damage which mark the path of the alpha particle. These paths are referred to as "alpha-tracks". After a period of not less than one month (shorter if the radon is particularly high), the film is removed and etched with a solvent to enhance the tracks and the tracks are optically counted under a microscope (there are some automated counting devises). The number of alpha tracks is a function of the radon concentration.

The advantages for alpha-track include simplicity, cost and inconspicuousity. They are slightly more expensive than the charcoal canisters. The alpha-tracks are as easy to use as charcoal canisters and are small and unobtrusive. They are not affected by either temperature or humidity.

Alpha-tracks can be used for long periods of time, integrating the exposure over that time. Typically, they are set for a period of three months to one year.

One disadvantage of the alpha-track method is the fact that they are slow. Generally, they should be exposed for periods not less than one month. Also, the analysis is more subjective than that of charcoal canisters. A +/- 50% uncertainty must be applied to a three month alpha-track measurement (at the 90% confidence level) when extrapolating the mean annual concentration.

Some studies 46 have shown that in using the alpha-track principal some materials may be capable of "remembering" their alpha exposure over the course of several decades. One method uses the glass found in windows, picture frames, and even old spectacles from a building's occupant. A long term decay product of radon is lead-210 which in turn decays to polonium 210. The polonium 210 becomes embedded in the glass via recoil processes and can be analyzed using alpha spectroscopy. The method provides an excellent opportunity to evaluate what the historical radon concentration of the building has been.

Continuous Working Level Meters (CWLMs)

In a CWLM, air is drawn through a filter which traps and retains the SLRDs but allows the radon to pass. The alpha from the SLRDs is counted in a preselected energy window (typically 2 to 8 MeV) over a specified period of time. The counts are automatically converted to WL by means of a calibration factor.

The advantages of the method include the ability to determine the actual extent of the true hazard; i.e. the SLRDs. The method can evaluate the efficacy of mitigation techniques which aim at reducing the SLRDs but do not address radon gas. Sources of radon such as showers, floor drains, sumps et cetera can be determined using CWLM. The results are relatively quick, and are obtained on-site without need for laboratory analysis allowing for real-time monitoring of SLRDs.

Some of the disadvantages include the high initial cost of the instrument or rental fees. The instruments are not simple black-boxes and require the use of a trained operator and the instruments need to be site calibrated.

MITIGATION TECHNIQUES

Mitigation techniques are divided mostly into three groups: 1) those that address reduction of radon gas; 2) those that address the reduction of SLRDs; and 3) those that address the DP.

The average 47 radon gas reduction, as of 1989, from mitigation techniques is 70%. However, it is more practical to speak of absolute reductions rather than per cent reductions. For example, it is easy to get a 98% reduction when reducing the radon in a building from 500 pCi/l to 10 pCi/l but it is extremely difficult to get a 20% reduction when attempting to reduce the radon from 5 pCi/l to 4 pCi/l.

The life time effectiveness of the mitigation techniques is still under review.

Ventilation

Ventilation as a radon reduction technique usually addresses reduction of the radon gas rather than the DP, because usually when a contractor is referring to ventilation, they are referring to ventilation of a crawl space, not a living area. When this is the case, the radon contractor usually refers to "isolation and ventilation".

Passive ventilation of a working or living area is typically considered to be an inappropriate technique for buildings in temperate climates because of the difficulty of maintaining comfort zone temperatures during the winter months. An additional problem with passive ventilation is that one does not have good control of the ventilation. A window may be open one minute until someone else feels cold and closes the window.

Additionally, it has been shown 48 that if other than the very lowest level of the building is passively ventilated (say by opening a window) then winds blowing through the building can create a venturi effect and actually increase the radon concentration. As discussed earlier, there is no correlation between air changes per hour and radon concentration, but there is a strong correlation between DP and radon concentration.

Passive ventilation of some heating cellars where the pipes are insulated and the room contains a sump may be a viable option. Ventilation systems designed for radon reduction are often fitted with heat recovery devices to help reduce the loss of heated air to the outside. Passive ventilation is obviously cheap, and easy but it has met with rather checkered results. It is most appropriate for small buildings with very low levels of radon.

Active ventilation, on the other hand, is usually in the form of HVAC systems and are not specifically designed as radon reduction systems. Nonetheless, because the HVAC systems are designed to maintain the building at slightly positive pressure, they address the DP issue. By maintaining a slight positive pressure, HVAC systems overcome the negative pressures of the stack effect and prevent radon from entering a building. The system should be capable of maintaining a positive pressure of at least 0.02 inches of water column (5 Pa) above the ambient pressure.

Filtration Devices

Filtration devices address the SLRDs without addressing the radon problem or the DP problem. Filtration devices circulate the room air through a filter which scrubs out the SLRDs.

On the surface, this type of technique appears to be an excellent solution, however, the filters will also remove the airborne particulates (ultrafine particles, dust, pollen, etc.) thus increasing the ratio of unattached daughters and actually increasing the bronchial radiological dose49. As mentioned earlier, the unattached daughters have a much higher probability of adhering to the lining of the lung wall. Therefore, the sole use of filtration devices is not considered to be an appropriate mitigation technique.

Air Movement Device: Ceiling Fans

This type of a system addresses neither the DP problem nor the radon entry problem, but rather the SLRDs themselves.

Unlike a filtration device, a ceiling fan does not remove the desirable airborne particulates but rather encourages the plate-out of the SLRDs. Since this type of technique can be installed by the homeowner (as a rather attractive addition to a living room or dining room), radon contractors do not have an incentive to disclose this technique to the general public.

Remarkably good reductions (as high as 95%) of SLRDs have been achieved 50 by simply placing a "Casablanca" type ceiling fan in a room. The fan should be capable of complete air movement within the room. Where the desired reduction is on the order of 50%, the ceiling fan alone can correct most of the problems.

Where a reduction of 80% or better is needed, the a ceiling fan in conjunction with a positive-ion generator may correct the problem. The ceiling fan/positive-ion generator combination has been tested in the U.S., Denmark, Finland and Canada 51 with similarly excellent results. The reduction in SLRDs has been consistently as high as 95% and where bronchial doses have been measured 52, the reduction in bronchial dose has been as high as 87%.

The positive ion generator should not be confused with an electrostatic precipitator (ESP). Using an ESP could result in the removal of airborne particulates and an increase in unattached daughters. Also, negative ion generators have been shown to be less effective than the positive ion generators 53. While the fan speed is not critical, the fan should be placed in the center of the room and be large enough to effectively move the air in the room.

A disadvantage to this type of reduction technique is that post-mitigation monitoring would have to involve a continuous working level monitor, instead of the charcoal canisters. Nonetheless, the savings achieved by the technique over some other mitigation methods would nearly off-set the cost of purchasing such an instrument (not to mention renting one).

Another disadvantage to this technique is that it can be readily turned off if not properly installed. The fan and the positive ion generator should be wired such that it cannot be deactivated by unauthorized personnel. The system should be labeled as a "radon reduction" system and allowed to run continuously.

Sealing Floor and Foundation Wall Cracks

Since some 90% of the radon 54 comes from sub-slab infiltration, one of the earliest mitigation techniques involved simply sealing floor and foundation wall cracks to prevent entry. The advantages of this method are its relative ease and low cost.

The disadvantages of the technique include its poor record of success, its limitation to only unfinished basements and the fact that it does not address DP, or SLRDs.

It has been shown that where high levels of radon are present, sealing alone is a very poor mitigation technique. However, sealing of floor and foundation wall cracks is often a necessary supplement to sub-slab depressurization (this will be discussed below).

When such sealing is required, the crack needs to be properly routed out first and then sealed back in with an appropriate material, such as backer-rod and foam.

Where high levels of radon are present, this technique is not recommend as a sole corrective action.

Positive Pressure

In some mitigation cases, the technique was to positively pressurize the basement. This technique has a poor record of success because it involves upsetting the normal use of the basement. It has a potential ability to blow out pilot lights and can be noisy. It is no longer generally considered to be an acceptable mitigation technique.

Sub-slab Depressurization (SSD)

Approximately 90% of the reduction techniques used in the U.S. today are SSD 55.

The idea of SSD is to address the driving force of the radon entry; the DP between the slab and soil gas. Instead of increasing the pressures within the building, SSD reduces the soil gas pressure below the slab. This author has measured in-house/sub-slab pressure differentials of as high as 89 Pa.

The SSD technique involves penetrating the slab with a 7cm to 20cm inside diameter PVC pipe and running the pipe up through the structure and exhausting to above the roof line. A centrifugal fan capable of developing high static pressure is mounted at the exhaust (outside the shell of the structure) to depressurize the slab. The fan should be capable of maintaining a pressure of at least 5Pa below the highest DP recorded or expected.

In some cases, 56 a passive turbine has been used with encouraging results. The driving force for the depressurization is the stack effect and a wind driven turbine at the exhaust.

SSD has a proven track record of achieving 80% to 90% reduction in radon gas levels in favorable structures. SSD works best when the soil type is a sand or a loam. Additionally, the slab should be in good condition; slab cracks and expansion joints will limit the extent of the pressure field. If the slab is damaged or the soil has a high clay content, then SSD can still be used by inserting more and more collection pipes in the slab to extend the pressure field.

Prior to SSD, soil communication tests should be performed. Pilot holes are drilled into the slab and a vacuum cleaner is used to create a negative pressure field below grade. The DP is measured at each of the pilot holes. If the DP at each of the holes is acceptable (5 Pa or greater) then only one hole is needed. If the DP at any one of the pilot holes is less than 5 Pa, then that hole should be enlarged and incorporated as a collection point. Typically, one collection point is needed for every 65 m2.

SSD works well for recessed floating slabs, slab-on-grade and floating slab-on-grade structures.

The are several important variations on the SSD theme. The first is perimeter drain depressurization whereby the pressure field is created using the existing exterior perimeter footing drain.

Block wall depressurization is used when the foundation wall consists of hollow block construction on a poured concrete footer. The foundation wall is penetrated with PVC piping and suction is applied to the wall. Prior to block wall depressurization, a block wall communication test should be performed to ensure uniformity in the depressurization. The block wall communication test is similar to the soil communication test. Doors, fire walls and other anomalies will disrupt the pressure field within the wall and require additional collection points. The block wall may be depressurized from the interior of the building or the exterior of the building.

In addition to the block wall depressurization technique, the same concept may be used for stem wall depressurization. Baseboard depressurization may be appropriate where there is a french drain present. Sumps may be used to depressurize the sub-slab soil.

Another important variation is the membrane suction technique used in crawl spaces. Since the earthen floor in the crawl space is incapable of allowing for an extended pressure field to develop, an impermeable membrane is placed over the entire floor of the crawl space. In some studies and case histories, the membrane is anchored to the floor using furring strips, and in other cases, the membrane is simply allowed to rest on the earthen floor.

Once the membrane is in place, a suction point is cut into the membrane roughly in the central portion and the soil gas is evacuated in the normal fashion.

One of the disadvantages of the SSD type systems is the cost. The initial cost of the installation is higher than most other techniques. The operating costs and the maintenance costs are also higher. The system can become noisy, prompting complaints from the building occupants and even prompting the occupants to deactivate the system.

The radon levels at the exhaust can be quite high and care must be taken to ensure that the radon is not reintrained back into the building shell.

Some contractors have experienced water vapor build-up from improperly installed systems. As the water vapor is extracted from the soil gas beneath the slab, it can condense within the pipes of the system. When this happens, the fan may be incapable of overcoming the back pressure and the pressure field below grade is disrupted. In some cases, the water vapor has condensed in the fan housing causing fan failure. The system must be designed to ensure that water build-up can safety be drained back into the slab, or to the out-of-doors.

The systems need to be installed with elaborate control panels which indicate the total pressure on both sides of the fan. Alarms are recommended to alert the building occupant in the event of fan failure, unacceptably high static pressure in the up-stream side of the fan or other problems which may develop.

If the SSD type systems are installed improperly, they can greatly increase the overall radon concentration in the building. Common faults include:

1) Placing the fan in the shell of the structure; if the fan leaks the radon is exhausted into the building.

2) Placing the fan in such a position that the radon is pushed along the exhaust pipe rather than pulled through the exhaust pipe. That is to say, the exhaust is under positive pressure with regard to the ambient pressure of the structure, if the pipe has a leak, the radon will enter the building.

3) Placing the exhaust too close to the plane of neutral pressure. During the stack effect, the lower portion of the building is under greater negative pressure than the top of the building; at a certain point, the pressure within the shell of the structure will equal the pressure outside and the DP will be zero. This point is called the plane of neutral pressure and is typically located 5cm to 8cm below the top most ceiling in the structure. If the exhaust of the SSD system is located at or below the plane of neutral pressure, the radon can be reintrained into the building.

Furthermore, improperly installed systems can result in exposing passers-by to the exhausting radon. The following criteria should be met:

1) The discharge point must be at least 3.5 meters above ground level.

2) The discharge point must be at least 3.5 meters (line-of-site) from any door, window or other structure openings that are less than 0.75m below the discharge point.

3) The discharge point must be at least 3.5 meters away from any private or public access.

4) The discharge point must be at least 3.5 meters away from any opening into an adjacent building.

The SSD systems have also been associated with back drafting problems whereby the exhaust from other sources of combustion (fireplaces, gas fired heaters and water heaters, etc.) within the building are disrupted. Therefore, following the installation of any depressurization system a test must be performed on any building which contains combustion appliances.


Educational Videos

FACTs provides on-site training in several areas including radiation and radiation toxicology. Below is a four-part series on a 90 minute presentation on the myths of residential radon. The talk is a simple, fact-based discussion regarding the myths of residential radon. Enjoy!

Radon: An Introduction to Radiation


Radon: An Introduction to Toxicology




Radon: An Introduction to Epidemiology and Testing


Radon: Three Minute Wrap-up


The information on this discussion is continuously updated whenever significant or materially new information becomes available. Those who have concerns about the dates of the studies and references may be interested in reading this discussion. This discussion was last updated on October 19, 2021

References:

1 Thompson RE, "Epidemiological Evidence For Possible Radiation Hormesis From Radon Exposure: A Case-Control Study Conducted In Worcester, MA Dose-Response, 9:59–75, 2011

2 Blot WJ, Xu ZY, Boice JD, et al. Indoor radon and lung cancer in China Journal of the National Cancer Institute, Volume 82, Issue 12, 20 June 1990, Pages 1025–1030

3 National Council on Radiation Protection and Measurements Report No. 78, Evaluation of Occupational and Environmental Exposures to Radon and Radon Daughters in the United States (1984) ISBN 0-913392-68-5

4 Jane E. Brody Some Scientists Say Concern Over Radon Is Overblown by E.P.A. (New York Times interview with Dr. Bernard L. Cohen, professor of physics and radiation health at the University of Pittsburgh), Jan. 8, 1991

5 Cole LA, Interview with Nobel Prize Winning Laureate (Physiology/Medicine) Dr. Rosalyn Yalow, "Element of Risk - The Politics of Radon" 1993 Dr. Yalow boasts no fewer than 47 honorary doctorates from universities around the world.

6 High Background Radiation Research Group, China "Health Survey in High Background Radiation Areas in China SCIENCE (22 Aug 1980) Vol 209, Issue 4459, pp. 877-880, DOI: 10.1126/science.7403855

7 Bodansky D, Jackson K, Geraci J "Calculated Lung Cancer Mortality Due to Radon op. cit. Bodansky D, Indoor Radon and Its Hazards" University of Washington Press, 1987.

8 New Jersey State Department Of Health, "A Case-Control Study Of Radon And Lung Cancer Among Mew Jersey Women Technical Report - Phase I, August, 1989

9 Castren O, "Dealing with Radon in Dwellings: The Finnish Experience Op. cit. Cole LA, "Element of Risk - The Politics of Radon" 1993

10 Lubin JH, Boice JD, Lung cancer risk from residential radon: meta-analysis of eight epidemiologic studies, J. Natl. Cancer Inst. 1997 Jan 1;89(1):49-57. doi: 10.1093/jnci/89.1.49.

11 Sandler DP, Weinberg CR, Shore DL, et al "Indoor Radon And Lung Cancer Risk In Connecticut And Utah J. Toxicol Environ. Health, Vol. 69(7), April 2006, doi: 10.1080/15287390500261117.

12 Ruosteenoja E, Indoor Radon And Risk Of Lung Cancer: An Epidemiological Study in Finland (STUK The Finnish Centre for Radition and Nuclear Safety)

13 Thompson RE, "Epidemiological Evidence For Possible Radiation Hormesis From Radon Exposure: A Case-Control Study Conducted In Worcester, MA Dose-Response, 9:59–75, 2011

14 Leonard A. Cole quotes Philip H Ableson (former editor of Science and recipient of the National Academy of Science Public Welfare Medal) that the statistics "seem to demonstrate that, if anything, moderate levels of radon are beneficial to the public health.", Elements of Risk: The Politics of Radon. AAAS Press, 1993. 77.

15 Nazaroff WW, Teichman K, Indoor Radon Exploring US Federal Policy for Controlling Human Exposures Environ. Sci. Tech. Vol. 24 No. 6, 1990, pp 774-782

16 Nazaroff WW, Teichman K, Indoor Radon Exploring US Federal Policy for Controlling Human Exposures Environ. Sci. Tech. Vol. 24 No. 6, 1990, pp 774-782

17 Kabat GC, Hyping Health Risks- Environmental Health Risks is Daily Life and the Science of Epidemiology, 2008

18 Darby S, Hill D, Auvinen A et al Radon in homes and risk of lung cancer: collaborative analysis of individual data from 13 European case-control studies doi:10.1136/bmj.38308.477650.63 (published 21 December 2004)

19Cohen, Bernard, L., D.Sc. "Correlation Between Mean Radon Levels And Lung Cancer Rates in U.S. Counties: A Test of the Linear-No Threshold Theory. Given at the 1988 USEPA Symposium on Radon and Radon Reduction Technology, Denver, Colorado

20 Cohen, Bernard, D.Sc. "Radon, A Homeowner's Guide to Detection and Control" Pub. Consumer's Union, New York 1987, ISBN 0-89043-227-9

21 Mossman KL, Goldman M, Mass F, Mills WA, Schiager KJ, Vetter RJ. "Radiation risk in perspective, Health Physics Society position statement" Health Physics Newsletter 24: 3, 1996.

22 "RADIATION RISK IN PERSPECTIVE" POSITION STATEMENT OF THE HEALTH PHYSICS SOCIETY PS010-3, May 2016

23United States Environmental Protection Agency, Office of Radiation Programs, "Radon Technology for Mitigators" 1989.

24 National Research Council, "Health Risks of Radon and Other Internally Deposited Alpha Emitters, BEIR IV", National Academy Press, Washington, DC., 1988

25 Risk Assessment Methodology, Environmental Impact Statement, NESHAPS for Radionuclides, Background Information Document- Volume 1. EPA/520/1-89-005, September, 1989

26 Risk Assessment Methodology, Environmental Impact Statement, NESHAPS for Radionuclides, Background Information Document- Volume 1. EPA/520/1-89-005, September, 1989

27 National Research Council, "Health Risks of Radon and Other Internally Deposited Alpha Emitters, BEIR IV", National Academy Press, Washington, DC., 1988

28 Braüske-Hohlfeld, I; Rosario, AS; Wilke, G; et al. Lung Cancer Risk among Former Uranium Miners of the WISMUT Company in Germany Health Physics March 2006, Volume 90, Number 3

28EPA Assessment of Risks from Radon in Homes (United States Environmental Protection Agency; Air and Radiation (6608J) EPA 402-R-03-003, June 2003)

29 The Health Physics Society at the University of Michigan Radiation Risk in Perspective

29 Appendix F - Nuclear Science—A Guide to the Nuclear Science Wall Chart ©2018 Contemporary Physics Education Project (CPEP), Lawrence Berkeley National Laboratory Berkeley, CA 94720

30 Pennington C.W. Siegel JA A failed ontology: The Linear No-Threshold model of radiogenic cancer - Nuclear Engineering International, July 2017

31 Cohen, Bernard, D.Sc. "Radon, A Homeowner's Guide to Detection and Control" Pub. Consumer's Union, New York 1987, ISBN 0-89043-227-9

32Casarett and Doull's Toxicology: The Basic Science of Poisons, Fourth Edition, Edited by Amdur, Mary O., PhD, Doull, John PhD, MD, Klaassen, Curtis D. PhD.

33U.S. Department of Energy "Radon- Radon Research Program, FY 1989, DOE/ER-448P., March 1990

34 Cohen, Bernard, L., D.Sc. "Correlation Between Mean Radon Levels And Lung Cancer Rates in U.S. Counties: A Test of the Linear-No Threshold Theory. Given at the 1988 USEPA Symposium on Radon and Radon Reduction Technology, Denver, Colorado

35U.S. Department of Energy "Radon- Radon Research Program, FY 1989, DOE/ER-448P., March 1990

36Title 10 Code of Federal Regulations 20.1003

37 Michals, L., et al, "Development and Demonstration of Indoor Radon Reduction Measures for 10 Homes in Clinton New Jersey" 1986

38United States Environmental Protection Agency, Office of Radiation Programs, "Radon Technology for Mitigators" 1989.

39Hubbard L. et al, "Radon Entry into Detached Dwellings: House Dynamics and Mitigation Techniques", Radiation Protection Dosimetery, 1987

40Harris, J. "Radon and Formaldehyde Concentrations as a Function of Ventilation Rates in Residential Buildings in the Northwest" Proceedings of the 1987 APCA Annual Meeting.

41United States Environmental Protection Agency, Office of Radiation Programs, "Radon Technology for Mitigators" 1989.

42United States Environmental Protection Agency, Office of Radiation Programs, "Radon Technology for Mitigators" 1989.

43NIOSH Occupational Exposure Sampling Strategy Manual, HEW Publication Number 77-173 (1977)

44 Mose, Douglas, G. et al "Realistic Uncertainties for Charcoal and Alpha-Track Monitors" Given at the 1988 USEPA Symposium on Radon and Radon Reduction Technology, Denver, Colorado.

45 Mose, Douglas, G. et al "Realistic Uncertainties for Charcoal and Alpha-Track Monitors" Given at the 1988 USEPA Symposium on Radon and Radon Reduction Technology, Denver, Colorado.

46 Samuelsson, Christer. Department of Radiation Physics, Lund University Hospital, Lund Sweden "Glass as a Retrospective Radon Detector" Given at the 1988 USEPA Symposium on Radon and Radon Reduction Technology, Denver, Colorado

47 United States Environmental Protection Agency, Office of Radiation Programs, "Radon Technology for Mitigators" 1989.

48 Tappan, J. Tell, "Passive Radon Reduction Techniques for Existing and New Structures" Given at the 1988 USEPA Symposium on Radon and Radon Reduction Technology, Denver, Colorado

49 Jonassen, Niels and Jensen, Bent Laboratory of Applied Physics, Technical University of Denmark "Removal of Radon Daughters by Filtration and Electrical Plateout"

50 Moeller, Dade, W. and Rudnick, Stephen N., Harvard School of Public Health, Boston Mass and Maher, Edward, F. Occupational and Environmental Health Laboratory, Brooks Air Force Base, Texas "Application of Air Cleaning Methods for the Removal of Radon Decay Products.

51 Moeller, Dade, W. and Rudnick, Stephen N., Harvard School of Public Health, Boston Mass and Maher, Edward, F. Occupational and Environmental Health Laboratory, Brooks Air Force Base, Texas "Application of Air Cleaning Methods for the Removal of Radon Decay Products.

52 Moeller, Dade, W. and Rudnick, Stephen N., Harvard School of Public Health, Boston Mass and Maher, Edward, F. Occupational and Environmental Health Laboratory, Brooks Air Force Base, Texas "Application of Air Cleaning Methods for the Removal of Radon Decay Products.

53 Moeller, Dade, W. and Rudnick, Stephen N., Harvard School of Public Health, Boston Mass and Maher, Edward, F. Occupational and Environmental Health Laboratory, Brooks Air Force Base, Texas "Application of Air Cleaning Methods for the Removal of Radon Decay Products.

54 United States Environmental Protection Agency, Office of Radiation Programs, "Radon Technology for Mitigators" 1989.

55 Personal conversation between the author and Dr. Milton Lammering, Region VIII EPA, Radiation and Air Programs Branch, Denver, Colorado, 1994.

56 Tappan, J. Tell, "Passive Radon Reduction Techniques for Existing and New Structures" Given at the 1988 USEPA Symposium on Radon and Radon Reduction Technology, Denver, Colorado

57 Thomas Huxley in a letter to Charles Kingsley, Sep. 23, 1860

58 Kuhn TS The Structure of Scientific Revolutions,1962, University of Chicago Press

59 Barber B, Resistance by Scientists to Scientific DiscoveryScience Vol. 134, p 596, 1961

60 What is EPA's Action Level for Radon and What Does it Mean? https://www.epa.gov/radon/what-epas-action-level-radon-and-what-does-it-mean (October 20, 2021)

60 Cole LA, "Element of Risk - The Politics of Radon" 1993, p. 77

61 Scott BR, Belinsky SA, Leng S, et al: "Radiation-Stimulated Epigenetic Reprogramming of Adaptive-Response Genes in the Lung: An Evolutionary Gift for Mounting Adaptive Protection Against Lung Cancer.Dose Response, Vol 7, No 2 (2009), pp. 104–131.

62 Scott BR, Belinsky SA, Leng S, et al: "Radiation-Stimulated Epigenetic Reprogramming of Adaptive-Response Genes in the Lung: An Evolutionary Gift for Mounting Adaptive Protection Against Lung Cancer.Dose Response, Vol 7, No 2 (2009), pp.

63 Thompson RE, Nelson DF, Popkin JH, Popkin A. "Case-control study of lung cancer risk from residential radon exposure in Worchester County, Massachusetts. Health Phys. 2008;94(3):228 -241.

64 Keynote address by John R. Garrison, at the US Environmental Protection Agency's The 1991 International Symposium on Radon and Radon Reduction Technology, Philadelphia, PA

65 Cohen BL, Expanded and Upgraded Tests of the Linear-No Threshold Theory for Radon-Induced Lung Cancer "The 1991 International Symposium on Radon and Radon Reduction Technology," Session #2, Paper Number 7, Philadelphia, PA

66 Cole LA, Interview with Philip Abelson, "Element of Risk - The Politics of Radon" 1993

67 Cole LA, Interview with Gun Astri Swedjemark, "Element of Risk - The Politics of Radon" 1993

68 Nazaroff WW, Teichman K, Indoor Radon, Environ. Sci. Tech. Vol. 24, Number 6, 1990

69 Leary, WE "13,000 Deaths a Year Indicated ByScience Academy Radon Study" New York Times interview with Dr. Jacob I. Fabrikant, professor of Radiology and Biophysics at the University of California at Berkeley (Jan 6, 1988).

70 Kabat GC, Hyping Health Risks- Environmental Health Risks is Daily Life and the Science of Epidemiology, 2008, p. 119

71 Reynolds T, Experts Debate Radon's Cancer Risks Journal of the National Cancer Institute, Volume 83, Issue 12, 19 June 1991, P. 810

72 Darby S, Hill D, Auvinen A, Barros-Dios JM, Baysson H, Bochicchio F, Deo H, Falk R, Forastiere F, Hakama M, Heid I, Kreienbrock L, (plus 15 others)... " Radon in homes and risk of lung cancer: collaborative analysis of individual data from 13 European case-control studies, British Medical Journal, doi:10.1136/bmj.38308.477650.63 (published 21 December 2004)

73 The May 20, 1992 draft memorandum was the DOE's observations on the "Indoor Radon Abatement Reauthorization Act of 1992. The excerpt in this discussion was found in the reproduction of the memo in Cole LA, "Element of Risk - The Politics of Radon" 1993

74 The May 20, 1992 draft memorandum was the DOE's observations on the "Indoor Radon Abatement Reauthorization Act of 1992. The excerpt in this discussion was found in the reproduction of the memo in Cole LA, "Element of Risk - The Politics of Radon" 1993

75 The violent exchange occurred at the 1988 EPA International Symposium on Radon and Radon Reduction Technology. This author (CP Connell) was present during the exchange and witnessed the outburst first hand. The violent outburst from the EPA staffer demonstrated that for radon advocates, the issue is messianic in nature and is a fanatical religion that rejects science.

76 Brenner DJRadon: Risk and Remedy 1989, Op cit, Supra Cole

77 Harley NH, Harley JH, Potential Lung Cancer Risk from Indoor Radon ExposureCA: A Cancer Journal for Clinicians, V 40, N 5, 1990

78 Ruckelshaus WD, "Risk, Science, and Democracy Issues in Science and Technology, Vol. 1, No. 3, pp 19-38 (1985).

79 Rodricks J, Taylor MR, "Application of Risk Assessment to Food Safety Decision Making Regulatory Toxicology and Pharmacology, Vol. 3, 1983

80 Cardarelli JJ, Ulsh BA, It Is Time to Move Beyond the Linear No-Threshold Theory for Low-Dose Radiation Protection Dose-Response: An International Journal (July-September 2018:1-24)

81Letter from Dr. Michael Honeycutt, Chair EPA Science Advisory Board and Dr. Hugh A. Barton, Chair SAB Chemical Assessment Advisory Committee to The Honorable Andrew R. Wheeler, Administrator, U.S. Environmental Protection Agency Consultation on Updating EPA Guidelines for Carcinogen and Non-Cancer Risk Assessment (EPA-SAB-19-003, July 15, 2019)

82 An example of the formal subterfuge employed by the EPA is the paper by Johnson FR, Fisher A, Smith VK, Desvousges WH "Informed Choice or Regulated Risk? Lesson from a Study in Radon Risk Communication" (Environment Vol 30, No. 4, May, 1988) The paper is entirely based upon broad mental reservations, and linguistic confusion specifically designed to mislead.

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