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The Risks of Exposure to Indoor Radon

The Risks of Exposure to Indoor Radon

Latest Epidemiological Research

This site is sponsored by the American Society of Radon Scientists and Technologists
(AARST) and provides a link to the latest published research from around the
world on the health risks of indoor radon exposure. 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 weblink to view and
print the study in its entirety.

If you have 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 peterhendrick@earthlink.com.

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;156:548–55.

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

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

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

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

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

Doses to Organs and Tissues >From Radon and its Decay Products UK National
Radiological Protection Board, Published in Journal of Radiological Protection

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

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 arguments regarding 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 5–10% 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

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
human–hamster 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)


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