Copyright
2003-2006
LARCO Properties Management, LLC.
( all rights reserved )
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Radon is a gaseous radioactive element
having the symbol Rn, the atomic number 86,
an atomic weight of 222, a melting point of
-71ºC, a boiling point of -62ºC, and
(depending on the source, there are between
20 and 25 isotopes of radon - 20 cited in
the chemical summary, 25 listed in the table
of isotopes); it is an extremely toxic,
colorless gas; it can be condensed to a
transparent liquid and to an opaque, glowing
solid; it is derived from the radioactive
decay of radium and is used in cancer
treatment, as a tracer in leak detection,
and in radiography. (From the word
radium, the substance from which it is
derived.) Sources: Condensed Chemical
Dictionary, and Handbook of Chemistry
and Physics, 69th ed., CRC Press, Boca
Raton, FL, 1988.
EPA's Integrated
Risk Information System profile on Radon 222
[CASRN 14859-67-7] is located at: epa.gov/iris/subst/0275.htm
Earth and rock
beneath home; well water; building
materials.
No immediate
symptoms. Based on an
updated Assessment of
Risk for Radon in Homes,
radon in indoor air is estimated to cause
about 21,000 lung cancer deaths each year in
the United States. Smokers are at higher
risk of developing Radon-induced lung
cancer. Lung cancer is the only health
effect which has been definitively linked
with radon exposure. Lung cancer would
usually occur years (5-25) after exposure.
There is no evidence that other respiratory
diseases, such as asthma, are caused by
radon exposure and there is no evidence that
children are at any greater risk of radon
induced lung cancer than adults
Based on a national
residential radon survey completed in 1991,
the average indoor radon level is about 1.3
picocuries per liter (pCi/L) in the United
States. The average outdoor level is about
0.4 pCi/L.
There is no debate
about radon being a lung carcinogen in
humans. All major national and international
organizations that have examined the health
risks of radon agree that it is a lung
carcinogen. The scientific community
continues to conduct research to refine our
understanding of the precise number of
deaths attributable to radon. The
National Academy of
Sciences BEIR VI Report
has estimated that radon causes about 15,000
to 22,000 lung cancer deaths annually based
on their two-preferred models. Major
scientific organizations continue to believe
that approximately 12% of lung cancers
annually in the United States are
attributable to radon.
The World Health
Organization (WHO), the National Academy of
Sciences, the US Department of Health and
Human Services, as well as EPA, have
classified radon as a known human
carcinogen, because of the wealth of
biological and epidemiological evidence and
data showing the connection between exposure
to radon and lung cancer in humans.
There have been
many studies conducted by many different
organizations in many nations around the
world to examine the relationship of radon
exposure and human lung cancer. The largest
and most recent of these was an
international study, led by the National
Cancer Institute (NCI), which examined the
data on 68,000 underground miners who were
exposed to a wide range of radon levels. The
studies of miners are very useful because
the subjects are humans, not rats, as in
many cancer research studies. These miners
are dying of lung cancer at 5 times the rate
expected for the general population. Over
many years scientists around the world have
conducted exhaustive research to verify the
cause-effect relationship between radon
exposure and the observed increased
lung cancer deaths in these miners
and to eliminate other possible causes.
In addition, there
is an overlap between radon exposures
received by miners who got lung cancer and
the exposures people would receive over
their lifetime in a home at EPA's action
level of 4 pCi/L, i.e., the lung cancer risk
in miners has been documented at exposure
levels comparable to those which occur in
homes/residences.
To have a
reasonable certainty in the conclusions,
many thousands of cases are required to
detect the increased risk of lung cancer due
to radon. This is because the more things
that cause a disease the harder it is to
separate one cause from another, thus it
takes many cases to pinpoint the risk from
each separate cause. The U.S. Public Health
Service radon experts estimate that 10,000
to 30,000 cases, and twice as many controls
would be needed to conduct a definitive
epidemiologic study of residential radon
lung cancer risk. The residential studies
conducted to date have all included between
50 and 1500 cases and thus have been too
small to provide conclusive information.
Some years ago this
same process was used to detect an increased
risk of lung cancer due to cigarette
smoking. It took many years of study to make
the positive link between the cause and
effect of smoking and lung cancer. Most of
the increased lung cancer risk is
attributable to smoking through mathematical
modeling. The research process for smoking
was very laborious. However, radon's process
is even more challenging because radon's
contribution to increased lung cancer risk
(12%) is difficult to see against the large
background of lung cancer due to other
causes, which include smoking, asbestos,
some heavy metals and other types of
radiation; i.e., detecting radon-related
lung cancer is like trying to detect a 12%
increase of sand on a beach already full of
sand.
Finally, it is
difficult to accurately determine radon
exposures in residential settings since we
are estimating past exposures from current
measurements. The number of required study
participants increases with the difficulty
in determining the exposure.
There are many
factors that must be considered when
designing a residential radon epidemiology
study. It is very expensive and often
impossible to design a study that takes all
the pertinent factors into consideration.
These factors include:
- Mobility:
people move a lot over their lifetime;
it is virtually impossible to go back
and test every home where an individual
has lived;
- Housing
Stock Changes: over time, older
homes are often destroyed or remodeled,
thus radon measurements will be
non-existent or highly varied; a home's
radon level may change, higher or lower,
over time if new ventilation systems are
installed, the occupancy patterns are
substantially different, or the home's
foundation shifts or cracks appear.
- Inaccurate
Histories: often a majority of the
lung cancer cases (individuals) being
studied are deceased or too sick to be
interviewed by researchers. This
requires reliance on second-hand
information which may not be as
accurate. These inaccuracies primarily
affect:
-
Residence History: a child or
other relative may not be aware of
all residences occupied by the
patient - particularly if the
occupancy is distant in time or of
relatively short duration. Even if
the surrogate respondent is aware of
a residence they may not have enough
additional information to allow
researchers to locate the home.
- Smoking
History: smoking history
historically has reliability
problems. Individuals may
under-estimate the amount they
smoke. Conversely, relatives or
friends may over-estimate smoking
history.
- Other:
complicating factors other than
variations in smoking habits include an
individual's: genetics, lifestyle,
exposure to other carcinogens, and home
heating, venting and air conditioning
preferences.
Yes, several
residential epidemiology studies have found
an increased risk of lung cancer due to
residential exposures (i.e. Sweden, New
Jersey ) These studies are also just pieces
of a much bigger puzzle that is being put
together. The
National Academy of
Sciences' BEIR VI Report
examines in detail the available studies of
radon and lung cancer in homes, as well as
the studies of underground miners.
We already have a
wealth of scientific data on the
relationship between radon exposure and the
development of lung cancer. The scientific
experts agree that the occupational miner
data is a very solid base from which to
estimate risk of lung cancer deaths
annually. While residential radon
epidemiology studies will improve what we
know about radon, they will not supersede
the occupational data. Health authorities
like the Centers for Disease Control (CDC),
the Surgeon General
 ,
the American Lung Association, the American
Medical Association, and others agree that
we know enough now to recommend radon
testing and to encourage public action when
levels are above 4 pCi/L. The most
comprehensive of these efforts has been the
National Academy of Science's
Biological Effects of
Ionizing Radiation (BEIR VI) Report.
This report reinforces that radon is the
second-leading cause of lung cancer and is a
serious public health problem. As in the
case of cigarette smoking, it would probably
take many years and rigorous scientific
research to produce the composite data
needed to make an even more definitive
conclusion.
The NAS published
its latest analysis of health research on
radon, the
Biological Effects of
Ionizing Radiation (BEIR VI)
Report in 1999. This is the most
comprehensive review effort to date. The
Committee was charged with:
- reviewing all
current miner and residential data, as
well as all existing cellular-biological
data,
- comparing the
dose per unit exposure effects of radon
in mines and homes, and
- examining:
- interactions between radon exposure
and smoking, and
- any exposure-rate effect (alteration
of effect by intensity of exposure).
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