The Risks of Exposure to Indoor Radon
Latest Epidemiological Research
The index below provides a brief description of the type of study conducted and a short summary of the researcher’s findings. Following each summary is a link to view and print the study in its entirety. If you would like to submit additional studies for consideration and posting, please email a PDF file of the paper to AARST Executive Director Peter Hendrick at firstname.lastname@example.org.
Exposure to Residential Radon and Lung Cancer in Spain:
A Population-based Case-Control Study Juan Miguel Barros-Dios, María Amparo Barreiro, Alberto Ruano-Ravina, and Adolfo Figueiras (May 2002)
The authors conducted a population-based case-control study in northwest Spain to determine the risk of lung cancer associated with exposure to residential radon. The study covered a total of 163 subjects with incident lung cancer and a population sample of 241 cancer-free subjects since 1992 1994.
Odds ratios for radon were estimated using logistic regression adjusted for sex, age, lifetime tobacco use, family history, and habitat. The adjusted odds ratios for the second, third, and fourth quartiles of radon (breakpoints: 37.0, 55.2, and 148.0 Bq/m 3) were 2.73 (95% confidence interval (CI): 1.12, 5.48), 2.48 (95% CI:1.29, 6.79), and 2.96 (95% CI: 1.29, 6.79), respectively.
An additive synergic effect between radon and tobacco was found. The results from this study suggest that, even at concentrations far below official guideline levels, radon may lead to a 2.5-fold rise in the risk of lung cancer. Furthermore, the synergy found between smoking and radon may prove useful when it comes to drafting public health recommendations. AmJEpidemiol 2002;156:54855.
Click link to view entire study: (Link to PDF)
Iowa Residential Radon Lung Cancer Study
American Journal of Epidemiology, 151(11): 1091-1102, (2000)
“UI Study Finds Residential Radon Exposure Poses a Significant Lung Cancer Risk”
This is a five-year study for which data collection began in 1993. Over 1000 Iowa women took part in the study. Four hundred and thirteen of the participants were women who had developed lung cancer; the remaining 614 participants were controls who did not have lung cancer. The study was limited to women, because they historically tend to spend more time at home and they have less occupational exposure to other lung carcinogens.
Researchers found excess risks to be 50% higher for exposures that are roughly equivalent to 15-years spent at an average radon exposure of 4 pCi/L. The results suggest that residential radon exposure is a significant risk factor for lung cancer.
The Iowa Radon Lung Cancer Study has several strengths. First, independent pathologic review was performed for 96 percent of the cases. Second, the study was carried out in Iowa, which has the highest mean radon concentrations in the United States. Third, the high radon concentrations in conjunction with a strict quality assurance protocol contributed to accurate and precise radon measurements. Fourth, the IRLCS criteria requiring occupancy in the current home for at least the last 20 years eliminated the need to impute radon measurements from missing homes. Fifth, the linkage between radon measurements and retrospective participant mobility allowed for a refined exposure estimate. The IRLCS risk estimates are in general agreement with the National Research Council's predicted cancer risk associated with indoor radon exposure. Overall, the risk estimates obtained in this study suggest that cumulative radon exposure in the residential environment is significantly associated with lung cancer risk.
Click link to view entire study: http://www.cheec.uiowa.edu/misc/radon.html
Radiation Risk To Low Fluences of Alpha Particles May Be Greater Than We Thought
Center for Radiological Research, College of Physicians and Surgeons and Environmental Health Sciences, School of Public Health, Columbia University August 2001
This study provides clear evidence that a single alpha particle can induce mutations and chromosome aberrations in cells that received no direct radiation exposure to their DNA. These findings imply that the target for radiation-induced genetic damage is larger than an individual cell. The observation is important in formulating risk assessment models because, for alpha particles, a cell cannot receive a dose lower than a single traversal and these hit cells are a minority population in lung tissue exposed to environmental radon.
The observation that irradiation of as few as 10% of a cell population results in a mutagenic yield similar to that when all of the cells in the population are hit indicates that low dose alpha particle irradiation can induce a huge bystander mutagenic response in neighboring cells not directly traversed by alpha particles. These results are of considerable importance in reassessing the potential genotoxic effect of low dose radiation and suggest that the assumption of direct proportionality in radiation may significantly underestimate the risk.
Click link to view entire study: (Link to PDF Risk of Low Alpha Hei 2002)
Residential Radon Exposure and Lung Cancer: Variation in Risk Estimates Using Alternative Exposure Scenarios
Journal of Exposure Analysis and Environmental Epidemiology 12, 197-203 (2002)
The BEIR VI Committee concluded (NRC, 1999) that the power of a residential radon study to detect an excess risk could be augmented by targeting populations that have high radon exposures and low residential mobility. The ability of the IRLCS to detect an association was enhanced by a study population characterized by low residential mobility and the potential for high radon exposure (Field et al., 2000).
However, the findings of this paper indicate that the power of a residential radon study to detect an excess risk is also enhanced by linking spatially disparate radon concentrations with the subject’s retrospective mobility, especially when live subjects can supply mobility information. In addition, our findings suggest that the dosimetry model used by some of the previous residential radon studies may have underestimated the true risk posed by radon progeny exposure.
Click Link to View Entire Study: (Link to PDF “2002 Iowa U Follow-up Study)
A Review of Residential Radon Case-Control Epidemiologic Studies Performed in the United States
College of Public Health, Dept. of Epidemiology, University of Iowa (2001)
Lung cancer is the leading cause of cancer death in the United States for both men and women. Although most lung cancer deaths are attributable to tobacco usage, even secondary causes of lung cancer are important because of the magnitude of lung cancer incidence and its poor survival rate.
This review summarizes the basic features and major findings from the published U.S. large-scale residential radon case-control studies performed in New Jersey, Iowa, and Missouri (two studies). The methodology from an unpublished study covering Connecticut, Utah, and Southern Idaho is also presented.
Overall, the higher categorical risk estimates for these published studies produced a positive association between prolonged radon exposure and lung cancer. Two studies (Missouri-II and Iowa) that incorporated enhanced dose estimates produced the most compelling evidence suggesting an association between prolonged residential radon exposure and lung cancer.
The prevailing evidence suggests that the statistically significant findings may be related to improved retrospective radon exposure estimates. The general findings from the U.S. studies, along with extrapolations from radon-exposed underground miners, support the conclusion that after cigarette smoking, prolonged residential radon exposure is the second leading cause of lung cancer in the general population.
Click Link to View Entire Study: (Link to PDF Review of Epidemiologic Studies 2001)
Doses to Organs and Tissues >From Radon and its Decay Products
UK National Radiological Protection Board, Published in Journal of Radiological Protection (2002)
Under normal circumstances, the largest dose from radon and its decay products will be that to the lung, delivered by the decay products rather than radon gas. This suggests that, when considering the radiological impact of radon and its decay products, the conventional focus on the risk of lung cancer from inhaled radon decay products is appropriate.
Nevertheless, calculations suggest that the dose to the basal layers of the skin may also be high, with a consequent possible risk of skin cancer. Unless countermeasures are taken, a smaller number of people may also run a significant risk of stomach cancer from radon ingested in drinking water. Doses to other organs and tissues are smaller, though not necessarily negligible. The results presented here allow these risks to be quantified and compared.
Click Link to View Entire Study: (Link to PDF Radon Doses to Organs & Tissues 2002)
Topics Under Debate: Does Exposure to Residential Radon Increase the Risk of Lung Cancer?
Radiation Protection Dosimetry, Vol. 95, No. 1, pg. 75-81 (2001)
The Biological Effects of Ionizing Radiation (BEIR) VI Report The Health Effects of Exposure to Indoor Radon, concluded that radon exposure represents a significant cause of lung cancer which was second only to cigarette smoking. Humans as a species have been exposed to various concentrations of radon for about as long as they have existed on Earth. Certain parts of our planet, because of their geology, have rather high naturally occurring concentrations of radon, and many people have been immersed in those high concentrations with seemingly little deleterious effect.
On the other hand, it is well known that mineworkers exposed to high concentrations of radon do indeed suffer health effects. When modern homes are constructed they are quite well sealed against air infiltration, thus by symmetry they are also resistant to the outflow of gases. In situations where homes are constructed in areas of high natural radon concentrations, it is logical to ask whether residents may or may not experience serious health effects. Our two participants have considered this question and have divergent views. They are both well qualified to present their argumentsregarding this topic, and we are fortunate to have them share those views with us in this debate.
Click link to view entire study: (Link to PDF Topics Under Debate 2001)
ATSDR Radon Toxicity -Case Studies in Environmental Medicine Course
U.S. Dept. of Health & Human Services, Agency for Toxic Substances and Disease Registry
Division of Health Education & Promotion, June 2000
The goal of this CSEM is to increase the primary care provider’s knowledge of hazardous substances in the environment and to aid in the evaluation of potentially exposed patients. After completion of this educational activity, the reader should be able to discuss the major exposure route for radon, describe two potential environmental and occupational sources of exposure to radon, state two reasons why radon is a health hazard, describe three factors that contribute to radon toxicity, identify evaluation and treatment protocols for persons exposed to radon, and list two sources of information on radon.
Click link to view entire course material: (Link to PDF)
Induction of a Bystander Mutagenic Effect of Alpha Particles in Mammalian Cells
Center for Radiological Research, College of Physicians and Surgeons and Environmental Health Sciences, School of Public Health, Columbia University October 1, 1999
Using a precision charged particle microbeam, we show here that irradiation of 20% of randomly selected AL cells with 20 alpha particles each results in a mutant fraction that is 3-fold higher than expected, assuming no bystander modulation effect. Furthermore, analysis by multiplex PCR shows that the types of mutants induced are significantly different from those of spontaneous origin. Pretreatment of cells with the radical scavenger DMSO had no effect on the mutagenic incidence. In contrast, cells pretreated with a 40 mM dose of lindane, which inhibits cell cell communication, significantly de-creased the mutant yield. The doses of DMSO and lindane used in these experiments are nontoxic and nonmutagenic.
We further examined the mutagenic yield when 510% of randomly selected cells were irradiated with 20 alpha particles each. Results showed, likewise, a higher mutant yield than expected assuming no by-stander effects.
Our studies provide clear evidence that irradiated cells can induce a bystander mutagenic response in neighboring cells not directly traversed by alpha particles and that cell to cell communication process play a critical role in mediating the by-stander phenomenon.
Click link to view entire study: (Link to PDF Bystander Mutagenic Effect)
1998 National Academy of Sciences- Biological Effects of Ionizing Radiation (BEIR) VI Report: “The Health Effects of Exposure to Indoor Radon”
Radon is one of the most extensively investigated human carcinogens. On the basis of the epidemiologic evidence from miners and understanding of the genomic damage caused by alpha particles, the committee concluded that exposure to radon in homes is expected to be a cause of lung cancer in the general population.
According to the committee's two preferred risk models, the number of lung-cancer cases due to residential radon exposure in the United States was projected to be 15,400 (exposure-age-duration model) or 21,800 (exposure-age-concentration model). Although these represent the best estimates that can be made at this time, the committee's uncertainty analyses using the constant relative risk model suggested that the number of cases could range from about 3,000 to 32,000. (The 95% upper confidence limit for the exposure-age-concentration model was approximately 38,000, but such an upper limit was highly unlikely given the uncertainty distributions.) Nonetheless, this indicates a public-health problem and makes indoor radon the second leading cause of lung cancer after cigarette smoking.
Click link to view entire study: http://www.epa.gov/iaq/radon/beirvi1.html
Targeted Cytoplasmic Irradiation With Alpha particles Induces Mutations in Mammalian Cells
Center for Radiological Research, College of Physicians and Surgeons and Environmental Health Sciences, School of Public Health, Columbia University January 21, 1999
The availability of the microbeam at the Radiological Research Accelerator Facility of Columbia University made it possible to target and irradiate the cytoplasm of individual cells in a highly localized spatial region. By using dual fluorochrome dyes (Hoechst and Nile Red) to locate nucleus and cellular cytoplasm, respectively, thereby avoiding inadvertent traversal of nuclei, we show here that cytoplasmic irradiation is mutagenic at the CD59 (S1) locus of humanhamster hybrid (AL) cells, while inflicting animal cytotoxicity. The principal class of mutations induced is similar to those of spontaneous origin and are entirely different from those of nuclear irradiation. Furthermore, experiments with radical scavenger and inhibitor of intracellular glutathione indicated that the mutagenicity of cytoplasmic irradiation depends on generation of reactive oxygen species.
These findings suggest that cytoplasm is an important target for genotoxic effects of ionizing radiation, particularly radon, the second leading cause of lung cancer in the United States. In addition, cytoplasmic traversal by alpha particles may be more dangerous than nuclear traversal, because the mutagenicity is accomplished by little or no killing of target cells.
Click link to view entire study: (Link to PDF)
Radon Occurrence and Health Risk Frequently Asked Questions by R. William Field, PHD (June 1999)
Residential epidemiologic case-control studies examining the relationship between contemporary 222Rn gas concentrations and lung cancer have been performed in Canada, China, Finland, Germany, Spain, Sweden, the United Kingdom, and the United States. A meta-analysis of eight studies using weighted linear regression found a summary excessive risk of 14% at an average indoor 222Rn gas concentration of 4 pCi/L. The excess risk at 4 pCi/L in recent studies in Germany and the United Kingdom was in close agreement with risk estimates obtained from the meta-analysis. The meta-analysis risk estimate was also consistent with the risk estimate extrapolated from miner studies. Additional residential case-control studies currently in progress in the United States (Missouri and Iowa) and Europe incorporate improved estimates of retrospective exposure to 222Rn progeny. In addition, the pooling of data from published and ongoing case-control studies is currently in progress.
Click link below to view entire document:
National Radon Results: 1985-1999
Gregory, Jalbert, U.S. Environmental Protection Agency (2002)
Since the mid-1980s the United States has made significant progress in reducing the risk from exposure to radon. This progress is the result of a long-term effort between EP A, citizens, non-profit organizations, state and local governments, the business community, and other Federal agencies working together. More adult Americans are knowledgeable about radon than at any time since the mid-1980s, when radon became a National health concern. Approximately two-thirds (66%) of Americans are generally aware of radon, and of those three-quarters (75%, on average) understand that radon is a health hazard. Since the mid-1980s, about 18 million homes have been tested for radon and about 500,000 of them have been mitigated. Approximately 1.8 million new homes have been built with radon-resistant features since 1990.
EPA will continue to focus its efforts, and those of its partners, on achieving actual risk reduction through the mitigation of existing homes and the building of new homes to be radon-resistant. EPA’s estimates of risk reduction are predicated upon mitigation systems being properly installed, operated and maintained. As a result of these actions to reduce radon levels in homes through 1999, EPA estimates that approximately 350 future lung cancer deaths will be prevented each year. This annual rate is expected to rise as radon levels are lowered in more new and existing homes.
Click link to review entire document: (Link to PDF)
Smokers Most at Risk from Radon Gas in European Homes
From Environmental News Service, Jan. 3, 2005: Effect of Radon Gas on Smokers Discussed)
BRUSSELS, Belgium - Exposure to radon in homes leads to an increased risk of lung cancer, in particular among smokers, according to a new study of risk from exposure to radon gas in European homes. The first study to examine radon risk to smokers separately from risk to nonsmokers, it found that for any given level of radon, smokers have about 25 times the risk of developing lung cancer as non-smokers.
Radon can also cause lung cancer in non-smokers but the risk is low. Recent ex-smokers were also found to be at higher risk from radon than non-smokers.
The results show that radon in homes is responsible for about 20,000 lung cancer deaths in the European Union each year. This is about nine percent of the total lung cancer deaths in the EU and about two percent of cancer deaths overall.
The risk increases in proportion to the concentration of radon gas in the home and is apparent at concentrations below current remedial action levels used in most European countries.
The study, co-funded by the European Commission, combines information and analysis from 13 smaller case-control studies across Europe covering 7,148 cases of lung cancer and 14,208 controls. The cases studied come from nine European countries.
It is the largest study ever into the effects of radon exposure in European homes. Previous such studies have not been large enough to assess the risks reliably. By comparison, in the United States, the National Academy of Sciences estimates that radon causes 19,000 cancer deaths each year. The "Annual Report on Carcinogens 2000" attributes to radon 20,000 lung cancer deaths per year.