Public Health Statement for Radon Gas

CONTENTS:

1.1 What is Radon?

1.2 How might I be exposed to Radon gas?

1.3 How can Radon gas enter and leave my body?

1.4 How can Radon gas exposure affect my health?

1.5 What levels of Radon exposure have resulted in harmful health effects?

1.6 Is there a medical test to determine whether I have been exposed to Radon?

1.7 What recommendations has the federal government made to protect human health from Radon gas?

1.8 Where can I get more information about Radon gas?

1.9 References

1.10 Environmental Alert

Who is at risk from Radon Gas?

Sources of Radon Exposure

Hazard Assessment

Respiratory Dose and Units of Measure

Risk Estimates

Table 1. Radon Risk Evaluation Chart if You Smoke

Table 2. Radon Risk Evaluation Chart if You Have Never Smoked

Radon Toxicity - Physiological Effects

Radon Toxicity - Treatment and Management

Radon Toxicity - Radon Abatement

Radon Toxicity - Standards and Regulations

Table 3. Residential Standards and Regulations for Radon

Table 4. Occupational Standards and Regulations for Radon

Radon Toxicity - Sources of Information

State Radon Contacts

State Radon Web Sites

Radon Toxicity - Suggested Reading

1.11 Complete Radon MSDS and Toxicological Information for Radon Gas

This Statement was prepared to give you information about radon and to emphasize the human health effects that may result from exposure to it. The Environmental Protection Agency (EPA) has identified 1,177 sites on its National Priorities List (NPL). Radon has been found above background levels at five of these sites. However, we do not know how many of the 1,177 NPL sites have been evaluated for radon. As EPA evaluates more sites, the number of sites at which radon is found may change. The information is important for you because radon may cause harmful health effects and because these sites are potential or actual sources of human exposure to radon. 

When a radioactive chemical is released from a large area such as an industrial plant, or from a container such as a drum or bottle, it enters the environment as a radioactive chemical, This emission, which is also called a release, does not always lead to exposure. You can be exposed to a chemical only when you come into contact with the chemical. You may be exposed to it in the environment by breathing, eating, or drinking substances containing the chemical or from skin contact with it.

If you are exposed to a hazardous substance such as radon, several factors will determine whether harmful health effects will occur and what the type and severity of those health effects will be. These factors include the dose (how much), the duration (how long), the route or pathway by which you are exposed (breathing, eating, drinking, or skin contact), the other chemicals to which you are exposed, and your individual characteristics such as age, sex, nutritional status, family traits, life style, and state of health.

Radon is a naturally occurring colorless, odorless, tasteless radioactive gas that is formed from the normal radioactive decay of uranium. Uranium is present in small amounts in most rocks and soil. It slowly breaks down to other products such as radium, which breaks down to radon. Some of the radon moves to the soil surface and enters the air, while some remains below the soil surface arid and enters the groundwater (water that flows and collects underground). Uranium has been around since the earth was formed and has a very long half-life (4.5 billion years), which is the amount of time required for one-half of uranium to break down. Uranium, radium, and thus radon, will continue to exist indefinitely at about the same levels as they do now.

Radon gas also undergoes radioactive decay and has a radioactive half-life of about 4 days. This means that one-half of a given amount of radon will be changed or decayed to other products every 4 days. When radon decays, it divides into two parts. One part is called radiation, and the second part is called a daughter. The daughter, like radon, is not stable; and it also divides into radiation and another daughter. Unlike radon gas, the daughters are metal and easily attach to dust and other particles in the air. The dividing of daughters continues until a stable, nonradioactive daughter is formed. During the decay process, alpha, beta, and gamma radiations are released. Alpha particles can travel only a short distance and cannot go through your skin. Beta particles can penetrate your skin, but they cannot go all the way through your body. Gamma radiation, however, can go all the way through your body. Thus there are several types of decay products that result from radon gas decay.

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References

Agency for Toxic Substances and Disease Registry (ATSDR). 1990. Toxicological profile for radon. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service. 

1.10 Environmental Alert

Contents:

Who is at risk from Radon Gas?

Sources of Radon Exposure

Hazard Assessment

Respiratory Dose and Units of Measure

Risk Estimates

Table 1. Radon Risk Evaluation Chart if You Smoke

Table 2. Radon Risk Evaluation Chart if You Have Never Smoked

Radon Toxicity - Physiological Effects

Radon Toxicity - Treatment and Management

Radon Toxicity - Radon Abatement

Radon Toxicity - Standards and Regulations

Table 3. Residential Standards and Regulations for Radon

Table 4. Occupational Standards and Regulations for Radon

Radon Toxicity - Sources of Information

State Radon Contacts

State Radon Web Sites

Radon Toxicity - Suggested Reading

Radon, like Asbestos, is a natural yet potentially harmful product of our planet. Hazardous Radon gas results from the decay of Uranium within Earth's crust and mantle. This radioactive decay of Uranium to Radon is a primary source of the heat which helps to turn solid rock into molten magma within our little blue marble. We are in essence living on a massive thermo-nuclear reactor thanks to the formation of Radon! It's no wonder Radon has been detected in many homes throughout all 50 U.S. states. In fact, no matter where on this world you stand, the process of Radon formation and subsequent surface emmission, is most likely occuring right below your feet!...But don't panic just yet! Instead take a deep breath and marvel at the natural environment in which we all live.

The atmosphere and weather, the plentiful oceans rivers and lakes, the varied landscapes, and all creatures great and small pretty much all owe their existance to the process of Radon formation. Really! From the Earth's internal thermal convection and resultant plate techtonics which sculpts the landmasses, to the first rain drops which fell on the cooling primordial Earth, the formation of Radon has been a "neccessary evil" for the metamorphosis to the planet as we know it today.

Radon is second only to smoking as a cause of lung cancer deaths in the U.S. It is estimated that more than 20,000 people die each year from Radon related lung cancer. However, for those who also smoke or were exposed to Environmental Tobacco Smoke (ETS or second-hand smoke), radon exposure will result in a dramaticly higher rate of lung cancer. Radon concentration and duration of exposure are also two primary factors used in Radon risk assessments.

Radon has quickly advanced up the list of harmful indoor air pollutants because as our dwellings become more and more air tight for energy efficiency sake, the gas is trapped inside and can increase in concentration with time. Worse yet, you can not see, taste, or smell Radon. Consequently, there are no obvious clues as to its presence despite it being a common airborn contaminant in the air of homes, offices, schools, and many other buildings. However, Radon breaks down into harmful radiation and paricles which can be detected in homes using a Radon test kit.

The EPA's guideline value for suggested Radon remediation is 4 pCi/L Radon, though there is no safe level of exposure concerning Radon or it's toxic by-products. The USEPA's guideline value of 4 pCi/L is the lowest concentration of Radon that could be achieved in the late 1970s when highly contaminated houses built on Uranium waste were tested after using control technologies that were 99% effective. It is now the standard level used to determine if there is a Radon safety issue needing remediation.

Approximately 1 out of every 3 Midwest homes contains Radon levels in excess of 4 pCi/L when a short term Radon test kit was used. These higher incidents seem to correlate with highly granitic soils, but not in all cases. A 3 to 6 month average Radon level is needed to get an accurate diagnosis of whether Radon remediation is needed because the EPA's guideline value of 4 pCi/L Radon is based on exposure of Radon over a one year period.

Radon gas and its by-products escape from the soil and tend to accumulate in basement or crawlspace air. Therefore, houses with basements tend to have higher concentrations of Radon compared to non-basement houses. Radon is also typically twice as concentrated in the basement compared to upstairs living areas so unless one lives in a basement area exposure to Radon is often much less than test results may indicate if Radon testing was performed in the basement. Radon testing should be performed on all levels of the dwelling below the 3rd floor.

If a short term Radon test kit indicates Radon remediation may be required several methods may reduce Radon in a home. Some Radon remediation systems can cost effectively reduce Radon levels up to 99%. Most problems with radon in the home can be fixed for between $800 and $2500.

One example, the soil suction radon reduction system involves a vent pipe system and Radon fan to evacuate contaminated air from crawlspaces or basement areas where Radon is typically in the highest concentrations. The installation of this Radon mitigation system involves no major changes to the home.

Radon fans are especially designed for radon mitigation by exhausting air outward. These Radon fans will not typically corrode as rapidly as a regular fan. Because of this, Radon fans can often be used for removing moist air from basements and crawlspaces as well as for radon removal.

Another method of Radon gas protection involves the use of air tight Radon seals where the Radon escapes from the Earth below a home. These Radon seals may be used in conjunction with Radon fans for an effective Radon removal system.

Regular Radon monitoring should be used to verify the effectiveness of any Radon mitigation system.

Radon Toxicity

Who is at Risk

• Miners in uranium and other types of underground mines are at risk of increased radon exposure.
• Petroleum Refinery workers

History of Radon

As early as the 16th century, Paracelsus and Agricola described a wasting disease of miners. In 1879, this condition was identified as lung cancer by Herting and Hesse in their investigation of miners from Schneeberg, Germany. Radon itself was discovered some 20 years later by Rutherford. Subsequently, an increase in the incidence of lung cancer among miners was linked to radon daughter exposure in mines. Underground uranium mines found throughout the world, including the western United States and Canada, pose the greatest risk because of their high concentration of radon daughters in combination with silica dust, diesel fumes, and, typically, cigarette smoke. Iron ore, potash, tin, fluorspar, gold, zinc, and lead mines also have significant levels of radon, often because of radium in the surrounding rock. In the past, it was not uncommon to use the tailings from these mines as fill on which to build homes, schools, and other structures.

Indoor radon daughters have been widely recognized as a potential problem in Europe and the Scandinavian countries since the 1970s. Public awareness in the United States was heightened in December 1984, when "Worker A" at the Limerick nuclear plant in Pennsylvania began setting off radiation alarms when he entered the plant. The cause was traced to levels of excessive radon daughters in his home-500 times the level at which the U.S. Environmental Protection Agency (EPA) recommends remediation (i.e., 4 picocuries per liter [pCi/L]). Radon daughters attach to dust particles in the air that are attracted to items such as clothing, especially when the air is cold and dry.

In 1987, the federal government allotted $10 million to the states to determine the extent of radon contamination in homes and schools, and subsequently amended the Toxic Substances Control Act to assist the states "in responding to the threat to human health posed by exposure to radon." In 1988, EPA and the Office of the Surgeon General jointly recommended that all US homes below the third floor be tested for radon. In 1990, Congress appropriated $8.7 million for grants to states to develop and enhance programs to reduce radon risk in homes and schools. It has become standard practice in some states to measure radon levels in homes at the time of real estate transactions. Radon testing is required for all government buildings.

• Approximately 6 million homes in the United States have radon concentrations above 4 pCi/L.

The amount of radon emanating from the earth and concentrating inside homes varies considerably by region and locality, and is greatly affected by the residential structure as well as soil and atmospheric conditions. Nearly every state in the United States has dwellings with measured radon levels above acceptable limits. EPA estimates that 6% of American homes (approximately 6 million) have concentrations of radon above 4 pCi/L. In Clinton, New Jersey, near a geologic formation (the Reading Prong) that is high in radium, all 105 homes tested were above the recommended guidelines; the levels in 40 homes exceeded 200 pCi/L. In the "Worker A" home, levels of 2,700 pCi/L were found in the basement.

Areas of the country that are likely to have homes with elevated radon levels are those with significant deposits of granite, uranium, shale, and phosphate, which are all high in radium content and, therefore, potential sources of radon gas. Some homes in these areas, however, might not have elevated levels of radon. Because of the many determinants of indoor radon levels, local geology alone is an inadequate predictor of risk.

The only way to determine indoor radon concentration is by testing. A home 100 feet away from the "Worker A" home did not have measured radon concentrations that required remediation, yet both houses were on the same geologic formation. Other factors that predispose homes to elevated levels of radon include soil porosity, foundation type, location, building materials used, entry points for soil gas, building ventilation rates, and source of water supply. Further research is being conducted on ways to predict which homes are most likely to have significant levels of radon.

• Exposure to excessive radon levels increases the already elevated risk of lung cancer for smokers. The primary adverse health effect of exposure to radon is lung cancer.

Several studies have shown that smokers exposed to radon are at greater risk for lung cancer than are similarly exposed nonsmokers. It is generally believed that exposure to radon and cigarette smoking are synergistic; that is, that the combined effect exceeds the sum of their independent effects. The risk of lung cancer from radon exposure is estimated to be 10 times greater for persons who smoke cigarettes in comparison with those who have never smoked. According to the National Academy of Sciences Committee on the Biological Effects of Ionizing Radiation (BEIR VI), a breakdown of the contribution of smoking and radon exposure to lung cancer deaths in the United States illustrates that of every 100 persons who died of lung cancer, approximately 93 were current or former smokers, whereas 7 had never smoked.

Data on the effects of radiation in children are limited, and even less is known about the effects of radon exposure in this age group. Cancer development in Japanese atomic bomb survivors suggests an increased susceptibility to radiation in children compared to that in adults. Children also have different lung architecture, resulting in a somewhat larger dose of radiation to the respiratory tract, and children have longer latency periods in which to develop cancer. However, no conclusive data exist on whether children are at greater risk than adults from radon.

Radon Toxicity
Exposure Pathways

Sources of Radon Exposure

• Radioactive decay of uranium through radium produces radon, which can move from soil into the air. It decays into a series of progeny, some of which are short-lived and emit alpha and beta particles and gamma rays.

Radon gas is derived from the radioactive decay of radium, a ubiquitous element found in rock and soil. The decay series begins with uranium-238 and goes through four intermediates to form radium-226, which has a half-life of 1,600 years. Radium-226 then decays to form radon-222 gas. Radon's half-life, 3.8 days, provides sufficient time for it to diffuse through soil and into homes, where further disintegration produces the more radiologically active radon progeny ("radon daughters"). These radon progeny, which include four isotopes with half-lives of less than 30 minutes, are the major source of human exposure to alpha radiation (high-energy, high-mass particles, each consisting of two protons and two neutrons). This alpha radiation produces damage that, if not repaired, results in cellular transformation in the respiratory tract, which can lead to radon-induced lung diseases or cancer.

• Radon, a colorless, odorless gas, is both chemically inert and imperceptible to the senses.
• Its infiltration into buildings is the main source of indoor radon; however, building materials and the water supply can also be sources.

Radon itself is imperceptible by odor, taste, and color, and causes no symptoms of irritation or discomfort. There are no early signs of exposure. Only by measuring actual radon or progeny levels can people know whether they are being exposed to excessive levels of radon. Radon seeps from the soil into buildings primarily through sump holes, dirt floors, floor drains, and cinder block walls, and through cracks in foundations and concrete floors (Figure 1). When trapped indoors, especially during a temperature inversion that reduces its escape from the building, radon can become concentrated to unacceptable levels. When radon escapes from the soil to the outdoor air, it is diluted to levels that offer relatively little health risk.

• Although concrete slab basements allow for less soil gas entry than do unfinished dirt-floor basements, both types of surfaces could permit entry of radon.

Radon gas can enter a building by diffusion, but pressure-driven flow is a more important mechanism. Negative pressure in the home relative to the soil is caused by exhaust fans (kitchen and bathroom), and by rising warm air created by fireplaces, clothes dryers, and furnaces. In addition to pressure differences, the type of building foundation can affect radon entry. Basements allow more opportunity for soil gas entry, but slab-on-grade foundations (no basement) allow for less. In most cases, the increase of indoor radon due to home "tightening" for energy conservation is slight compared to the amount of radon coming from the soil.

Typical building materials, such as concrete block, brick, granite, and sheet rock, contain some radium and are sources of indoor radium. Normally, these construction materials do not contribute significantly to elevated indoor radon levels. In rare cases, however, building materials themselves have been the main source of radioactive gas. Building materials contaminated with uranium and vanadium mill tailings in Monticello, Utah, and uranium mill tailings in Grand Junction, Colorado, were an important source of radon because they contained elevated concentrations of radium. (Tailings are the sandlike material remaining after minerals are removed from ore.) Also, concrete made from phosphate slag in Idaho and Montana and insulation made from radium-containing phosphate waste from the state of Washington have been found to emit high levels of radon.

Radon might enter into homes via the water supply. With municipal water or surface reservoirs, most of the radon volatilizes to air or decays before the water reaches homes, leaving only a small amount from decay of uranium and radium. However, water from private wells might be another matter. Groundwater that comes from deep subterranean sources and passes over rock rich in uranium and radium, such as that found in northern New England, might dissolve some of the radon gas produced from radium decay. As the water splashes during showering, toilet flushing, dishwashing, and laundering, radon is released into the air and can result in inhalation exposure. Radon can also be present in natural gas supplies.

Hazard Assessment

Respiratory Dose and Units of Measure

• Radon and its progeny can be detected only by testing.

Because the health effects of radon poisoning are insidious and have a long latency period, it is important to measure exposure to the gas empirically. Techniques for measuring radon are discussed in the Radon Detection section. Included here is a review of the basic unit of radon measurement and the factors that are used to estimate radiation dose from air concentration information and physical parameters. (Note that this subsection is on dose and units, and not on risk.)

The relationship between exposure to radon and the dose of radiation from decay products that reaches target cells in the respiratory tract is complex. Some factors that influence the pulmonary radiation dose include the following:

• Characteristics of inhaled air radon. Progeny that are attached to dust particles (the attached fraction) deposit much more efficiently than free or unattached progeny; of the attached progeny, only those adhering to the smallest particles are likely to reach the alveoli.
• Amount of air inhaled. The amount and deposition of inhaled radon decay products vary with the flow rate in each airway segment.
• Breathing pattern. The proportion of oral to nasal breathing will affect the number of particles reaching the airways. Oral breathing deposits more of the larger particles in the nasopharyngeal region. Regardless of the breathing pattern, the smaller the particle, the deeper it penetrates into the lung and the more likely it is to deposit there.
• Architecture of the lungs. Sizes and branching pattern of the airways affect deposition; these patterns may differ between children and adults and between males and females. Preferential deposition of larger particles occurs at all branch points because of inertial impaction.
• Biologic characteristics of the lungs. The radiation dose occurs in those areas where mucociliary action is either absent or ineffective in removing the particles. Particles moving with the mucous flow cause essentially no radiation dose to tissue because of the short range of alpha particles in fluids.

It is possible, therefore, that two environments with the same radon measurement (e.g., a dusty mine and a home environment) might cause different deposition patterns and, therefore, deliver different doses of alpha radiation to a person's lungs. Likewise, two persons in the same environment might receive differing doses of alpha radiation to the target cells in the upper portion of their lungs because of differing breathing patterns and pulmonary architecture.

• EPA recommends remediation for homes with airborne radon levels at or above 4 pCi/L.
• In early 2000, EPA proposed municipal drinking water levels tied to state plans to remediate radon in indoor air.

If particle size distribution is not known, an assumed distribution, along with the average measured air concentration, is used to estimate deposition within the lung and the resulting radiation dose. The higher the average radon level a person experiences, the higher the radiation dose. Radon gas can be collected on activated charcoal filter media, or the attached progeny can be collected on mesh filters. Radon measurements are expressed in picocuries per liter of air, where a picocurie is equivalent to the amount of progeny in which 0.037 atoms disintegrate per second. EPA has recommended that remedial action be taken to lower the amount of radon in homes if the level measured in air is 4 pCi/L or greater.

Risk Estimates

Even conservative estimates based on current knowledge suggest that radon is one of the most important environmental causes of death. EPA and the National Cancer Institute estimate that approximately 15,000 deaths annually in the United States are due to lung cancer caused by indoor radon exposure. It has also been estimated that approximately 14% of the 164,100 cases of lung cancer diagnosed annually are attributable to radon.

• For a lifetime exposure at the EPA recommended guideline of 4 pCi/L, EPA estimates that the risk of developing lung cancer is 1 to 5%, depending on whether a person is a nonsmoker, former smoker, or smoker.
• The overall risk of radon exposure is related not only to its level in the home, but also to the occupants and their lifestyles.

For a lifetime exposure at the EPA recommended guideline of 4 pCi/L, EPA estimates that the risk of developing lung cancer is 1 to 5%, depending on whether a person is a nonsmoker, former smoker, or smoker. The National Research Council estimates the risk as 0.8 to 1.4%.

Many factors influence the risk of lung cancer due to radon exposure; among these are age, duration of exposure, time since initiation of exposure, cigarette smoking, and other carcinogen exposures (Table 1 and Table 2). In assessing the risk of radon in a home or office, it is important to consider not only the average level of radon, but also the occupants and their lifestyles. Are there any smokers? Any children? How much time is spent in the home? Where do occupants sleep? The highest radon levels are typically found in the lowest level of the house. If well water is the major source of radon, upper floors can be affected more than lower floors. In colder climates, radon levels are often higher in the winter and lower in the summer.

Table 1. Radon Risk Evaluation Chart if You Smoke

Radon Level	If 1,000 People Who Smoked Were Exposed to This Level Over a Lifetime...	The Risk of Cancer From Radon Exposure Compares to...	What To Do: STOP SMOKING and...
20 pCi/L	About 250 men or 143 women  could die of lung cancer	> 100 times the risk of drowning	Consider fixing between 2 and 4 pCi/L
8 pCi/L	About 132 men or 66 women could die of lung cancer	> 100 times the risk of dyingin a home fire	Consider fixing between 2 and 4 pCi/L
4 pCi/L	About 66 men or 33 women could die of lung cancer	> 100 times the risk of dying in an airplane crash	Consider fixing between 2 and 4 pCi/L
2 pCi/L	About 33 men or 16 women could die of lung cancer	> 2 times the risk of dyingin a car crash	Consider fixing between2 and 4 pCi/L
1.0 pCi/L	About 16 men or 8 women could die of lung cancer	(Average indoor radon level)	(Reducing radon levels below 2 pCi/L is difficult)
0.4 pCi/L	About 8 men or 4 women could die of lung cancer	(Average outdoor radon level)
*pCi/L: picocuries per liter. If you are a former smoker, your risk might be lower.

Table 2. Radon Risk Evaluation Chart if You Have Never Smoked

Radon Level	If 1,000 People Who Never Smoked Were Exposed to This Level Over a Lifetime...	The Risk of Cancer From Radon Exposure Compares to...	What To Do:
20 pCi/L	About 33 men or 20 women could die of lung cancer	> 2 times the risk of being killed in a violent crime	Consider fixing between2 and 4 pCi/L
8 pCi/L	About 13 men or 8 women could die of lung cancer		Consider fixing between 2 and 4 pCi/L
4 pCi/L	About 6.4 men or 4 women could die of lung cancer	> 10 times the risk of dying in an airplane	Consider fixing between 2 and 4 pCi/L
1.0 pCi/L	About 1.6 men or 1 woman could die of lung cancer	The risk of dying in a home fire (Average indoor radon level)	(Reducing radon levels below 2 pCi/L is difficult)
0.4 pCi/L	Less than 1 person could die of lung cancer	(Average outdoor radon level)
*pCi/L: picocuries per liter. If you are a former smoker, your risk might be higher.

Radon Toxicity
Physiologic Effects

• The primary adverse health effect of exposure to radon daughters is lung cancer.

Radon exposure causes no acute or subacute health effects, no irritating effects, and has no warning signs at levels normally encountered in the environment. The only established human health effect associated with residential radon exposure is lung cancer. Epidemiologic studies of miner cohorts have reported increased frequencies of chronic, nonmalignant lung diseases such as emphysema, pulmonary fibrosis, and chronic interstitial pneumonia, all of which increased with increasing cumulative exposure to radiation and with cigarette smoking.

• The synergistic mechanism(s) of cigarette smoking and radon exposure are not known, although the adverse health effects of the combination are clear.

Epidemiologic studies and a recent study of groundwater radon and cancer mortality have found no association with extrapulmonary cancers, such as leukemias and gastrointestinal cancers. This is expected on the basis of studies of the radium-dial painter population. Evidence is also lacking that environmental radon exposure is causally associated with adverse reproductive effects.

• Radon progeny can be inhaled either as free particles or attached to dust. Attached progeny preferentially deposit in the bronchi, the site of most lung cancers.

Because of their charged state and solid nature, radon progeny rapidly attach to most available surfaces, including walls, floors, clothing (as in the case of "Worker A"), and airborne particulates. Radon progeny can be inhaled, therefore, either as free, unattached particles or attached to airborne dust. Smaller dust particles can deposit radon progeny deep in the lungs. Because they are ionized, the progeny tend to attach to the respiratory epithelium. Through mucociliary action, the progeny are eventually cleared from the respiratory tract, but because of their short half-life, they can release alpha particles before being removed. The total amount of energy deposited by the progeny is several hundred times that produced in the initial decay of radon. When these emissions occur within the lungs, the genetic material of cells lining the airways can be damaged, resulting in lung cancer.

The risk of lung cancer due to radon exposure is thought to be second only to that of smoking. The synergism between cigarette smoking and radon places the large population of current and former smokers at particularly high risk for lung cancer. Although the net consequence of cigarette smoking and exposure to radon decay products has been clearly demonstrated in smokers, the mechanism of interaction is still unclear.

Most of the lung cancers associated with radon are bronchogenic, with all histologic types represented. However, small-cell carcinoma occurs at a higher frequency among both smoking and nonsmoking populations of underground miners in the initial years after exposure, compared to the pattern of histologic types in the general population. Other types of lung cancers seen in radon-exposed miners are squamous cell carcinoma, adenocarcinoma, and large-cell carcinoma.

Radon Toxicity
Treatment and Management

• Generally, the most effective methods to reduce the risk of lung cancer are smoking cessation and radon mitigation.

No effective communitywide screening methods are available for medical prevention or early diagnosis and treatment of lung cancer (radon-induced or otherwise). Routine chest radiographs and sputum cytology are ineffective for screening lung cancer associated with cigarette smoking and would presumably be ineffective for screening lung cancer associated with radon as well. The most effective methods of prevention are reduction of radon exposure and modification of other simultaneous risk factors for lung cancer, such as smoking. The only long-term solution for reducing the risk of  lung cancer is smoking cessation, coupled with detection and mitigation of high radon levels.

• The potential risk of cancer due to radon poisoning is often underestimated by the public; this bias might discourage assessment and abatement measures in the home.

Several studies have noted optimistic biases in the public's assessment of the risk due to radon. A New Jersey study found that this bias might discourage testing and subsequent implementation of control measures. In Maine, homeowners were found to greatly underestimate the potential risk, and abatement behavior was not significantly related to potential risk.

Primary care physicians and public health professionals should promote public awareness so that the radon safety problem is seen in the proper perspective, leading to appropriate mitigation action when indicated. Physicians and public health officials should therefore test their own homes and offices to relate their experience to others and to provide guidance on how to carry out the testing.

Radon Toxicity
Radon Detection

Radon levels cannot be accurately predicted solely on the basis of factors such as location, geology, building materials, and ventilation. Measurement is the key to identifying the problem. Radon detection kits are available in most hardware stores.

Short-term testing (lasting a few days to several months) is the quickest way to determine if a potential problem exists. Charcoal canisters, liquid scintillation detectors, electret ion detectors, alpha-track detectors, and continuous monitors are the most common short-term testing devices. Short-term testing should be conducted in the lowest inhabited area of the home, with the doors and windows shut.

Long-term testing (lasting up to 1 year) will give a better reading of a home's year-round average radon level than will a short-term test. Alpha-track detectors and electret ion detectors are the most common long-term testing devices. Exposed devices are sent via mail to a certified laboratory for analysis. These devices measure radon gas levels, rather than radon progeny; thus, the units reported are in picocuries of radon per liter of air.

The charcoal canister is a small can containing charcoal and a filter to keep out radon progeny. It is inexpensive ($10 to $25) and is generally used for short-term testing (3 to 7 days). The alpha-track device contains a small piece of plastic in a filtered container. As the radon gas that has entered the container decays, the alpha particles form etch tracks. These tracks can be counted using a special technique. The cost of the alpha-track device is roughly twice that of the charcoal canister, and it can be used to measure cumulative exposure over a longer period (i.e., several weeks to a year).

Congress has mandated that each state set up an office to deal with requests for radon assistance. Many states provide radon detection kits such as the charcoal canister free of charge as a public service. A list of state radon contacts can be found in the Sources of Information section.

Radon Toxicity
Radon Abatement

Radon Abatement

• The cost of remediation to reduce radon levels in the average home is about $1,200.
  
• Available procedures to lower indoor radon levels are, dollar for dollar, very effective in saving lives.

How cost-effective is radon mitigation compared to other investments in health protection? The Swedish government plans to spend approximately $1,000 per home reducing high radon levels, resulting in about $10,000 in savings per life spared. EPA estimates that the cost of remediation in most homes is less than $1,500. The cost of radon testing and mitigation per life saved compares favorably with that of other government programs.

If excessive levels of indoor radon are found in a structure, low-cost, quick-fix methods should be implemented first. These methods include limiting the amount of time spent in contaminated areas and increasing ventilation in the areas. It is wise to consult with the state radiation protection office before implementing major abatement projects. Information on methods of reduction can be obtained from several sources listed in the Suggested Reading and Sources of Information sections.

• Subslab depressurization is one of the most effective methods of lowering radon levels in many homes.

In addition to increasing ventilation, radon control measures include sealing the foundation, subslab depressurization (creating negative pressure in the soil), pressurizing the home, and using air-cleaning devices. Methods of increasing ventilation include opening windows, ventilating basements and crawl spaces, ventilating sump-holes and floor drains to the outside of the house, and increasing air movement with ceiling fans. Ventilation must be modified properly, however, because increased ventilation can depressurize the house in some cases, causing an increase of soil gas entry to the home. Heat exchangers provide a way of bringing fresh air indoors without major heat loss, but these must be properly balanced or they can worsen the problem.

Preventing soil gas entry is more important than increasing whole-house ventilation. Prevention of soil gas entry involves sealing the foundation and depressurizing the soil. Potentially useful methods for prevention of soil gas entry include using vapor barriers around the foundation, sealing cracks and holes with epoxies and caulks, and sealing the crawl space from the rest of the house. Subslab depressurization can reduce radon levels by as much as 99%. Suction puts the soil at a lower pressure than the inside of the home, preventing inward migration of soil gas. Subslab depressurization involves sinking ventilation pipes below the foundation and continuously pumping air out. The cost to install subslab depressurization in an existing home is approximately $1,000 to $2,500; annual utility costs are about $100. The state radon office can be consulted to obtain a listing of radon mitigation contractors that have passed the EPA Radon Contractor Proficiency program. If the equipment is installed during construction of the home, however, the cost of subslab depressurization is considerably less; it is much easier to install pipes during construction than to retrofit later. Physicians and other health professionals can perform a public service by becoming acquainted with local building codes and urging local jurisdictions to include the installation of capped pipes terminating in a space under the foundation to allow for later subslab depressurization if needed.

Pipes, attached to a suction fan, are inserted into the ground below the basement floor, creating a low-pressure region under the house. Adapted from Brenner (1989).

Radon Toxicity
Standards and Regulations

Standards and Regulations

• No enforceable regulations exist to control indoor radon levels—only guidelines and a national goal.

No regulations mandate specific mimimum radon exposure levels for indoor residential and school environments—only guidelines for remediation, such as the EPA recommendations and a national goal. EPA based its guidelines not only on risk considerations, but also on technical feasibility. No level at which the risk of exposure to alpha emitters is zero is thought to exist. Many standards and guidelines for radon are being reviewed (Table 3 and Table 4), and changes might occur over time. EPA or state health departments should therefore be consulted for the most up-to-date standards.

• The national goal is for indoor radon levels to be as low as those outdoors. About 0.4 pCi/L radon is normally found in outside air.

In October 1988, the Indoor Radon Abatement Act was passed. This act states that the "national long-term goal of the United States with respect to radon levels in buildings is that the air within buildings in the United States should be as free of radon as the ambient air outside of buildings." The act mandates that EPA update its publication, A Citizen's Guide to Radon,  and provide a series of action levels indicating the health risk associated with these various levels. The guide will also provide information on the risk to sensitive populations, testing methods, and the cost and feasibility of mitigation techniques. EPA recommends remediation for homes and other buildings with levels above 4 pCi/L, with the caveat that corrective action be taken below this level on a case-by-case basis.

Table 3. Residential Standards and Regulations for Radon

Source	Focus	Level*	Comments
Indoor Radon Abatement Act	Indoor air (residential)	Indoor = outdoor (~0.4 pCi/L)	National goal
National Council for Radon Protection	Indoor air (residential)	8 pCi/L	Guideline
U.S. Environmental Protection Agency	Indoor air (residential)	4 pCi/L	Current action level
	Schools	4 pCi/L†	Guideline for action
	Water	4,000 pCi/L with state indoor air risk reduction program	Proposed regulation
		300 pCi/L without state indoor air risk reduction program
*pCi/L: picocuries per liter. †The U.S. Environmental Protection Agency recommends action below 4 pCi/L in schools on a case-by-case basis.

Table 4. Occupational Standards and Regulations for Radon

Source	Focus	Level	Comments
National Institute for Occupational Safety and Health	Occupational (mining)	1 WLM */year and ALARA†	Advisory; exposure limit
Occupational Safety and Health Administration	Occupational	4 WLM/year	Regulation
Mine Safety and Health Administration	Mining	4 WLM/year	Regulation
American Conference of Governmental Industrial Hygienists	Occupational	4 WLM/year	Advisory for radon daughters
*WLM (working-level month): a unit of measure commonly used in occupational environments. (Because WLM bears a complex relationship to picocuries per liter, physicians with responsibility for mine workers are urged to contact the National Institute for Occupational Safety and Health or the U.S. Environmental Protection Agency for further information.) †ALARA: as low as reasonably achievable.

Radon Toxicity
Sources of Information

More information on the adverse effects of radon and the treatment and management of persons exposed to radon can be obtained from the Agency for Toxic Substances and Disease Registry (ATSDR), your state and local health departments, and university medical centers. Physicians and other health professionals can obtain materials from EPA for display purposes. EPA maintains a radon hotline (1-800-SOS-RADON).

Case Studies in Environmental Medicine: Radon Toxicity is one of a series. For other publications in this series, use the order form on page 34. For clinical inquiries, contact ATSDR, Division of Toxicology and Environmental Medicine, at 770-488-3490.

State Radon Contacts

Congress has mandated that each state set up an office to deal with requests for radon testing and remedial action. Note that the 800 numbers are for in-state use only and are subject to change. An updated list is available from URL www.epa.gov/iaq/contacts.html.

Native Americans living on Indian lands should contact their Tribal Health Department of Housing Authority for assistance. (See Tribal Radon Program Offices information.)

Alabama 1-800-582-1866 334-206-5391	Idaho 1-800-445-8647 208-332-7319	Minnesota 1-800-798-9050 651-215-0909
Alaska 1-800-478-8324	Illinois 1-800-325-1245 217-785-9958	Mississippi 1-800-626-7739 601-987-6893
Arizona 602-255-4845, x244	Indiana 1-800-272-9723 317-233-7147	Missouri 1-800-669-7236 572-751-6160
Arkansas 1-800-482-5400 501-661-2301	Iowa 1-800-383-5992 515-281-4928	Montana 1-800-546-0483 406-444-6768
California 1-800-745-7236 916-324-2208	Kansas 1-800-693-5343 785-296-1561	Nebraska 1-800-334-9491 402-471-0594
Colorado 1-800-846-3986 303-692-3090	Kentucky 502-564-4856	Nevada 775-687-5394, x275
Connecticut 860-509-7367	Louisiana 1-800-256-2494 225-925-7042	New Hampshire 1-800-852-3345, x4674 603-271-4674
Delaware 1-800-464-4357 302-739-4731	Maine 1-800-232-0842 207-287-5676	New Jersey 1-800-648-0394
District of Columbia 202-535-2999	Maryland 1-800-438-2472 x2086 215-814-2086	New Mexico 505-827-4300
Florida 1-800-543-8279 850-245-4288	Massachusetts 1-800-RADON95 [1-800-823-6695] 413-586-7525 x1124	New York 1-800-458-1158
Georgia 1-800-745-0037 404-872-3549	Michigan 1-800-723-6642 517-335-8037	North Carolina 919-571-4141
Hawaii 808-586-4700	Texas 512-834-6688	North Dakota 701-221-5188
Oklahoma 405-271-5221	Utah 801-538-6734	Ohio 1-800-523-4439
Oregon 503-731-4014	Vermont 1-800-640-0601	Guam 671-475-1611
Pennsylvania 1-800-237-2366	Virginia 1-800-468-0138	Puerto Rico 787-274-7815
Puerto Rico 809-767-3563	Washington 1-800-323-9727	Virgin Islands 212-637-4013
Rhode Island 401-277-2438	West Virginia 1-800-922-1255	Tribal Radon Program Offices
South Carolina 1-800-768-0362	Wisconsin 608-267-4795	Hopi Tribe Arizona: 520-734-2442 x635
South Dakota 605-773-3351	Wyoming 1-800-458-5847	Inter-Tribal Council of Arizona: 602-307-1527
Tennessee 1-800-232-1139		Navajo Nation: 520-871-7863
		Duckwater Shoshone-Paiute Tribe: 702-863-0222 (Nevada)

• Alabama Geological Survey- Radon http://www.ogb.state.al.us/gsa/geologichazards/radon/
• Arizona State Agency of Geologic Information- Radon Information http://www.azgs.state.az.us/radon_info.htm
• California Department of Health Services - Radon http://www.dhs.cahwnet.gov/ps/ddwem/environmental/radon/radon.htm

• Colorado Department of Public Health and Environment (CDPHE) - Indoor Radon http://www.cdphe.state.co.us/lr/Radon/rn_hom.asp
• Connecticut Department of Public Health Radon Program http://www.dph.state.ct.us/BRS/radon/radmain.htm
• Florida Bureau of Environmental Toxicology - Radon Home Page http://www.doh.state.fl.us/environment/facility/radon/index.html

• Idaho - Facts About Radon http://www2.state.id.us/dhw/BEHS/radon.htm
• Illinois Dept. of Nuclear Safety http://www2.state.il.us/idns/html/radon/radon.asp
• Indiana State Department of Health - Radon http://www.in.gov/idem/air/programs/radon/facts.pdf
• Iowa Bureau of Radiological Health - Radon http://www.idph.state.ia.us/hpevh/toxicology_env_health.asp#radon

• Kansas Department of Health and Environment - Radiation Section http://www.kdhe.state.ks.us/radiation/
• Kentucky Cabinet for Health Services Department for Public Health - Radon Gashttp://chs.state.ky.us/publichealth/radon.htm
• Louisiana State Radon Web Site http://www.deq.state.la.us/laboratory/rpradon.htm
• Maine Radon Homepage http://www.state.me.us/dhs/eng/rad/hp_radon.htm
• Maryland Geological Survey http://www.mgs.md.gov/esic/brochures/radon.html
• Massachusetts Department of Public Health - Public Health Fact Sheet - Radon http://www.state.ma.us/dph/rcp/radonfq.htm
• Michigan Dept. of Environmental Quality - Drinking Water and Radiological Protection Division http://www.michigan.gov/deq/0,1607,7-135-3313_3675---S,00.html
• Minnesota Department of Health - Radon in Minnesota Homes http://www.health.state.mn.us/divs/eh/indoorair/radon/index.html

• Mississippi State Department of Health - Radon http://www.msdh.state.ms.us/msdhsite/index.cfm/11,0,100,html
• Missouri Department of Health - Radon Program http://www.health.state.mo.us/FactSheets_Reports/Radonfct.html
• Montana Department of Environmental Quality- Planning, Prevention and Assistance Division - Radon and You: Promoting Public Awareness of Radon in Montana's Air and Ground Water http://www.mbmg.mtech.edu/radon.htm
• Nebraska Health & Human Services - Radon http://www.hhs.state.ne.us/enh/radon/radon.htm
• Nevada Radiological Health Section - Radon http://health2k.state.nv.us/bhps/rhs/srha.htm
• New Hampshire Department of Health and Human Service - Radon Program http://www.dhhs.state.nh.us/DHHS/RADON/default.htm
• New Jersey Dept. of Environmental Protection - Radon Section http://www.state.nj.us/dep/rpp/radon/index.htm
• New Mexico Environmental Department - Indoor Radon Outreach Program http://www.nmenv.state.nm.us/nmrcb/radon.html
• New York - RX for Radon http://www.health.state.ny.us/nysdoh/radon/radonhom.htm
• Radon in North Carolina http://www.ces.ncsu.edu/depts/fcs/radon/
• North Dakota Department of Health - Radon http://www.health.state.nd.us/ndhd/environ/ee/rad/Radon/index.htm

• Ohio Radon Information System http://www.radon.utoledo.edu/
• Oregon Radiation Protection Services - Radon http://www.ohd.hr.state.or.us/rps/radon/index.cfm
• Pennsylvania Dept. of Environmental Protection - Radon Division http://www.dep.state.pa.us/dep/deputate/airwaste/rp/Radon_Division/Radon_Homepage.htm

• South Dakota Dept. of Environment and Natural Resources - Radon http://www.state.sd.us/denr/DES/AirQuality/aarad.htm
• Tennessee - Radon Program http://www.state.tn.us/environment/apc/radon/
• Utah Dept. of Environmental Quality - Indoor Radon Program http://www.eq.state.ut.us/eqrad/RADON.htm
• Vermont - Dept. of Health Radon Education Program http://healthvermont.gov/enviro/rad/Radon.aspx
• Virginia Virginia Radiation Protection Programs Indoor Radon Program http://www.vdh.virginia.gov/epi/publichealthtoxicology/pdf/Radon.pdf
• Washington State Department of Ecologyhttp://www.ecy.wa.gov/pubs/96503/appd.htm
• West Virginia Radon Program http:www.wvdhhr.org/rtia/pdf/radon%20facts.pdf
• Wisconsin - Radon Program http://www.dhfs.state.wi.us/dph_beh/RadonProt/index.htm
• Wyoming Radon Project http://wdhfs.state.wy.us/radon/

Radon Toxicity
Suggested Reading

General

1. Anonymous. 1986. Standard procedures for radon measurement developed by the EPA. J Environ Health 49:163-5.
2. Bierma TJ. 1989. Radon risk factors. J Environ Health 51:277-81.
3. Brenner DJ. 1989. Radon risk and remedy. New York: W.H. Freeman and Co.
4. Council on Scientific Affairs. 1987. Radon in homes. JAMA 258:668-72.
5. Kerr RA. 1988. Indoor radon: the deadliest pollutant. Science 240:606-8.
6. National Research Council. 1999. Health effects of exposure to radon, BEIR VI. Washington (DC): National Academy Press. Available from URL: books.nap.edu/books/0309056454/html/index.html. 
7. National Council on Radiation Protection and Measurements. 1984. Evaluation of occupational and environmental exposures to radon and radon daughters in the United States. Bethesda (MD): National Council on Radiation Protection and Measurement. NCRP report no. 78.
8. Nero AV, Schwehr MB, Nazaroff WW, Revzan KL. 1986. Distribution of airborne radon-222 concentrations in U.S. homes. Science 234:992-7.
9. Nazaroff WW, Nero AV Jr, editors. 1988. Radon and its decay products in indoor air. New York: Wiley.
10. Lubin JH. 1988. Models for the analysis of radon-exposed populations. Yale J Biol Med 61:195-214.

Health Effects

1. Harley N, Samet JM, Cross FT, Hess T, Muller J, Thomas D. 1986. Contribution of radon and radon daughters to respiratory cancer. Environ Health Perspect 70:17-22.
2. Samet JM, Nero AV Jr. 1989. Sounding board: indoor radon and lung cancer. N Engl J Med 320:591-4.

Related Documents

1. Agency for Toxic Substances and Disease Registry. 1990. Toxicological profile for radon. Atlanta: US Department of Health and Human Services.
2. American Conference of Governmental Industrial Hygienists. 1999. Threshold limit values for chemical substances and physical agents and biological exposure indices. Cincinnati (OH): American Conference of Governmental Industrial Hygienists.
3. Centers for Disease Control. 1985. Health hazards associated with elevated levels of indoor radon—Pennsylvania. MMWR 34:6578.
4. Centers for Disease Control. 1987. A recommended standard for occupational exposure to radon progeny in underground mines. Atlanta: US Department of Health and Human Services. Report No. (NIOSH): 88-101. Available from URL: http://www.cdc.gov/niosh/88-101.html. 
5. Centers for Disease Control. 1989. Radon exposure assessment—Connecticut. MMWR 38:713-5.
6. Centers for Disease Control. 1989. Lung cancer and exposure to radon in women New Jersey. MMWR 38:715-8.
7. US Environmental Protection Agency. 1986. Radon reduction techniques for detached houses: technical guidance. 2nd ed. Washington (DC): US Environmental Protection Agency, Office of Research and Development. Report No. EPA 625/587/019.
8. US Environmental Protection Agency. 1987. Radon reference manual. Washington (DC): US Environmental Protection Agency, Office of Radiation Programs. Report No. EPA 520/18720.
9. US Environmental Protection Agency. 1987. Removal of radon from household water. Washington (DC): US Environmental Protection Agency, Office of Research and Development. Report No. EPA87011.
10. US Environmental Protection Agency. 1989. Radon measurements in schools: an interim report. Washington (DC): US Environmental Protection Agency, Office of Radiation Programs. Report No. EPA 520/189/010.
11. US Environmental Protection Agency. 1989. Radon reduction methods: a homeowner's guide. 3rd ed. Washington (DC): US Environmental Protection Agency, Office of Research and Development. Report No. EPA89005.
12. US Environmental Protection Agency. 1992. A citizen's guide to radon: the guide to protecting yourself and your family from radon. 3rd ed. Washington (DC): US Environmental Protection Agency, Office of Air and Radiation. Report No. OPA86004. Available from URL: www.epa.gov/iaq/radon/pubs/citguide.html.  Also available in Spanish from URL: www.epa.gov/iaq/radon/pubs/elradon.html. 

13. US Environmental Protection Agency. 1992. Consumer's guide to radon reduction: how to reduce radon levels in your home. Washington (DC): US Environmental Protection Agency, Office of Air and Radiation. Available from URL: www.epa.gov/iaq/radon/pubs/consguid.html. 

14. US Environmental Protection Agency. 1993. Radon - A physician's guide. Washington (DC): US Environmental Protection Agency, Office of Air and Radiation. Available from URL: www.epa.gov/iaq/radon/pubs/physic.html. 

15. US Environmental Protection Agency. 2000. Radon in water. Washington (DC): US Environmental Protection Agency, Office of Radiation Programs. Available from URL: www.epa.gov/iaq/radon/rnwater.html. 

16. US Environmental Protection Agency. The national radon measurement proficiency (RMP) program: cumulative proficiency report. Washington (DC): US Environmental Protection Agency, Office of Radiation Programs. Report No. EPA 520/188/024. (Published twice annually for various states; lists participating vendors of radon detection equipment and services.)
17. Public Health Service. The health consequences of smoking: cancer. A report of the Surgeon General. Washington (DC): US Department of Health and Human Services; 1982. DHHS report no. (PHS) 8250179.

1.11 Complete Radon MSDS and Toxicology Information for RADON Gas

CASRN: 10043-92-2

CONTENTS:

Evidence for Carcinogenicity:

Evaluation: There is sufficient evidence for the carcinogenicity of radon and its decay products in experimental animals. There is sufficient evidence for the carcinogenicity of radon and its decay products in humans. Overall evaluation: Radon and its decay products are carcinogenic to humans (Group 1).
[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work)., p. V43 241 (1988)]**PEER REVIEWED**

Human Toxicity Excerpts:

The influence of radon and radon daughters on development of respiratory cancer is reviewed. Epidemiological studies thus far indicate that excess lung cancer mortality is connected with miners having cumulative radon daughter exposures somewhat below 100 working level month. A working level month is defined as a 170 hr working month exposure to alpha radiation from radon daughters equal to 1.3X10+5 megaelectron volts emitted in 1 liter of air. An additive rather than a multiplicative model has been gaining support to illustrate the connection between smoking and radon daughter induced lung cancer.
[Harely N et al; Environmental Health Perspectives 70: 17-21 (1986)]**PEER REVIEWED**

A case referent study on the possible association between radon emanating from the ground and bronchial cancer was carried out on 292 female lung cancer cases and 584 matched population referents. Both groups had lived for at least 30 yr in the city of Stockholm, Sweden. The cases were diagnosed during 1972 to 1980 with oat cell and other types of anaplastic pulmonary carcinomas. A sample of about 10% of the dwellings where cases and referents had lived was selected for measurements of radon and radon daughters. The measurements indicated increased radon daughter concentrations in ground level dwellings within radon risk areas where lung cancer cases had lived, suggesting that this exposure was of etiologic importance.
[Svensson C et al; Int Arch Occup Environ Health 59 (2): 123-31 (1986)]**PEER REVIEWED**

Indoor radon concentrations seem to depend on both building material and leakage of radon from the ground. This study, in a rural area, is a further attempt to elucidate the etiology of lung cancer, taking into consideration type of house and ground conditions, as well as smoking habits. Although the choice of a rural study population helped to eliminate various confounding exposures in the urban environment, it limited the size of the study because of the rareness of lung cancer in rural populations. Long term residents, 30 yr or more in the same houses, were studied, and again an association was found between lung cancer and estimated exposure to radon and radon daughters in homes. The data also seem to indicate the possibility of a multiplicative effect between smoking and exposure to radon and radon daughters in homes, but there was also some confounding between these factors in the data.
[Edling C; Scand J Work Environ Health 10 (1): 25-34 (1984)]**PEER REVIEWED**

The chief hazard is inhalation of the gaseous element and its solid daughters, which are collected on the normal dust of the air. This material is deposited in the lung and has been considered to be a major causative agent in the high incidence of lung cancer.
[Sax, N.I. Dangerous Properties of Industrial Materials. 6th ed. New York, NY: Van Nostrand Reinhold, 1984., p. 2357]**PEER REVIEWED**

Peripheral lymphocyte chromosomes from 80 underground uranium miners and 20 male controls in the Colorado plateau, USA, were studied, taking into account confounding factors such as smoking habits and diagnostic radiation. Five groups with increasing cumulative exposure to radon and radon decay products were selected. Peripheral lymphocytes were cultured for 68-72 hr. Pericentric inversions and translocations showed the most consistent pattern of increase with estimated radiation dose. All aberration categories, except dicentrics and rings, demonstrated a significant, uniform increase with dose from < 100 to 1740-2890 working level month, but not at >3000 working level month. Significantly more chromosomal aberrations were observed among workers with markedly atypical bronchial cell cytology, suspected carcinoma, or carcinoma in situ than among miners with regular or mildly atypical cells, as evaluated by sputum cell cytology.
[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work)., p. V43 212 (1988)]**PEER REVIEWED**

A case control study was carried out in Port Hope, Ontario, Canada, to evaluate the relative significance of domestic exposure to radon (Rn) in the etiology of lung cancer over a period of 10 years, with control for the effect of smoking. Twenty seven cases of lung cancer and 49 comparisons matched for age and duration of residence in the town were analyzed. Examination of the histopathological records revealed that 11 of the 27 cases (40.7%) had squamous cell carcinoma and six had adenocarcinoma (22.6%); the other ten cases were not classified. After allowing for the effect of smoking, a marginally significant association (degree of significance equal to 0.057) was established between exposure to Rn and lung cancer. Classification of exposure in terms of living or not living in a problem home demonstrated a strong confounding between Rn exposure and smoking, in that all four exposed cases were smokers while the two exposed comparisons were not. In this case also, after allowing for the effect of smoking, a marginally significant association (significance 0.050) was established between Rn exposure and lung cancer. About 90% of all lung cancer cases identified demonstrated a strong association with cigarette smoking.
[Lees REM et al; Inter J Epidemiol 16 (1): 7-12 (1987)]**PEER REVIEWED**

Uranium miners in Saskatchewan. Mean time of follow after start of work: 14 yr cut-off date for follow up: 12/31/80. Numbered studied: 8,487. Mean age at first exposure: 28 yr. Mean calendar year of first exposure: 1966. Mean exposure: 2.8 WLM for surface workers and 16.6 WLM for underground workers. Control data were taken from Canadian national male rates. Radon progeny measurements were made from 1954 to 1967. Radon gas measurements were made from 1954 to 1967. Uranium mining began in 1949 and ended in 1982. Workers with other mining experience were excluded from analysis. At exposure levels greater than 100 working level months, the number of observed cases of lung cancer, 17, was significantly greater than the expected number of 2.21 (p < 0.05). Lung cancer risk appeared to be a function of age at first exposure. Information on smoking habit was not reported.
[Howe GR et al; JNCI 77: 357-62 (1986) as cited in IL Department of Energy and Natural Resources; Risk Assessment of Exposure to Waterborne and Airborne Radon-222 in IL p.28 (1987) ILENR/RE-AQ-87/21]**PEER REVIEWED**

... The histopathological patterns of lung cancer in uranium miners in the Colorado plateau region /are described /. The cases were miners included in the US Public Health Service study and other miners who lived in the Colorado plateau area. The classification of the histopathology was based on either a single pathologist's reading or on the consensus of a panel; 312 cases of lung cancer were analyzed among uranium miners. Most of the cases occurred in cigarette smokers; the series included 14 nonsmokers. In the early reports, the majority of the cases were small cell carcinomas; however, the proportion of this cell type declined from 76% in 1954 to 22% (compared to 17% in non-mining cigarette smokers) in the late 1970s. In nonsmokers, eight cases were small cell carcinomas and the remaining six were of other cell types.
[IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work)., p. V43 236 (1988)]**PEER REVIEWED**

In all situations where an excess of lung cancer has been observed, there have been simultaneous exposure to other potentially carcinogenic substances or agents such as other metals ... or radon.
[Zenz, C., O.B. Dickerson, E.P. Horvath. Occupational Medicine. 3rd ed. St. Louis, MO., 1994, p. 604]**PEER REVIEWED**

Lung cancer is the only malignancy clearly associated with exposure to radon.
[Zenz, C., O.B. Dickerson, E.P. Horvath. Occupational Medicine. 3rd ed. St. Louis, MO., 1994, p. 409]**PEER REVIEWED**

... A higher incidence of chromosomal aberrations /was reported/ among uranium miners exposed to radon and radon daughters at cumulative exposures ranging from less than 100 to more greater than 3,000 WLM, a compared to their matched controls. A clear exposure related increase was observed for the groups exposed to 770 to 2,890 WLM with a sharp decrease at the highest dose group (greater than 3,000 WLM).
[Brandom W et al; Radiat Res 76: 159-171 (1978) as cited in U.S. Dept Health & Human Services/ATSDR; Toxicological Profile for Radon p.23 (1990) PB91-180422]**PEER REVIEWED**

Statistically significant excesses in lung cancer deaths have been reported in uranium miners in the United States.
[Archer V et al: Health Phys 25: 351-371 (1973) as cited in U.S. Dept Health & Human Services/ATSDR; Toxicological Profile for Radon p.23 (1990) PB91-180422]**PEER REVIEWED**

Among uranium miners, epidermoid, small cell undifferentiated, and adenocarcinoma were present with increased frequency, while large cell undifferentiated and other morphological types of lung cancer were seen less frequently.
[Archer V et al; Cancer 34: 2056-2060 (1974)as cited in U.S. Dept Health & Human Services/ATSDR; Toxicological Profile for Radon p.24 (1990) PB91-180422]**PEER REVIEWED**

Purpose: To clarify the relationship between domestic radon exposure and the occurrence of chromosomal aberrations, stable translocations especially, in peripheral blood lymphocytes. The study comprised a total of 84 non-smoking individuals, divided into three groups according to radon concentration measurements performed in their homes: low radon concentration (<100 Bq/cu m, mean 67 Bq/cu m), medium (200-400 Bq/cu m, mean 293 Bq/cu m) or high (>800 Bq/cu m, mean 1737 Bq/cu m). Significant correlation of translocations with age was observed, and due to the high mean age (50 years) the genome-corrected