
What is radon? Radon is a cancer-causing
radioactive gas. You cannot see, smell, or taste radon, but it could
be a problem in your home. When you breathe air containing radon,
you increase your risk of getting lung cancer. In fact, the Surgeon
General has warned that radon is the second leading cause of lung
cancer in the United States today. If you smoke and your home has
high radon levels, your risk of lung cancer is especially high.
Radon: A More Scientific Description
Radon is a gaseous, highly radioactive element. It was discovered by
English physicist Ernest Rutherford in 1899. Although the discovery
is *also* credited to German physicist Friedrich Ernst Dorn in 1900,
it may be fairer to say that Rutherford discovered radon's alpha
radiation and that Dorn found that radium was giving off a gas. (We
welcome input from anyone with additional documentation concerning
this issue.)
Radon is a colorless, chemically un-reactive inert gas; it is the
densest gas known. The gas and its highly radioactive (radioactivity
described) metallic daughter products emit alpha and beta
particles and gamma rays. It has been used in the treatment of
cancer by radiotherapy. In homes and other buildings, in some areas
of the world, radon produced by the radioactive decay of uranium-238
present in soil and rock can reach levels regarded as dangerous.
(Chemical Symbol/Element Number: Rn222)

SHOULD YOU TEST FOR RADON?
Testing is the only way to know your home’s radon levels. There
are no immediate symptoms that will alert you to the presence of
radon. It typically takes years of exposure before any problems
surface and then it is too late.
The U.S. Environmental Protection Agency, Surgeon General,
American Lung Association, American Medical Association, and
National Safety Council all recommend testing your home for radon.
Click
here for a map of Radon Zones in North Carolina.
CAN YOU FIX THE PROBLEM?
If you find that your home has high radon levels, there are ways
to reduce the concentrations. Even very high levels can be reduced
to acceptable levels. Most radon problems can be fixed by a
do-it-yourselfer.
RADIATION AND RISK FACTS
The alpha radiation emitted by radon is the exact same alpha
radiation that is emitted by any other alpha generating radiation
source, like plutonium.
A family whose home has radon levels of 4 pCi/l is exposed to
approximately 35 times as much radiation as the NUCLEAR REGULATORY
COMMISSION allows if they were standing next to the fence of a
radioactive waste site. (25 mrem limit, 800 mrem exposure)
An elementary school student that spends 8 hours per day and 180
days per year in a classroom with 4 pCi/l of radon will receive
nearly 10 times as much radiation as the NUCLEAR REGULATORY
COMMISSION allows at the edge of a nuclear power plant.(25 mrem
limit, 200 mrem exposure)
Most United States Environmental Protection Agency (EPA) lifetime
safety standards for carcinogens are established based on a 1 in
100,000 risk of death. Most scientists agree that the risk of death
for radon at 4 pCi/l is approximately 1 in 100. At the 4 pCi/l EPA
action guideline level radon carries approximately 1000 times the
risk of death as any other EPA carcinogen.
Radon-induced lung cancer costs the United States over $2 Billion
dollars per year in both direct and indirect health care costs.
(Based on National Cancer Institute statistics of
14,400 annual radon lung cancer deaths)
(Oster, Colditz & Kelley, 1984)
CANCER AND SCIENTIFIC FACTS
CARCINOGENICITY
Radon's primary hazard is caused from inhalation of the gas and
its highly radioactive heavy metallic decay products (Polonium,
Lead, and Bismuth) which tend to collect on dust in the air. The
problem arises when these elements stick to the delicate cells
lining the passageways leading into the lungs.
There is sufficient evidence for the carcinogenicity of radon and
its isotopic forms, radon-222 and radon-220, in experimental
animals. When administered by inhalation, preceded by a single
exposure to cerium hydroxide dust, radon induced pulmonary adenomas,
adenocarcinomas, invasive mixed adenosquamous carcinomas, and
squamous cell carcinomas in male rats. Extrapulmonary metastases
occurred in only one animal. Most or all of the tumors were believed
to be bronchiolar or bronchio-alveolar in origin. Radon decay
products in combination with uranium-ore dust induced a progression
of activity from single basal cell hyperplasia in bronchioles to
malignant tumors in male hamsters when exposed by inhalation. Lung
tumors observed were adenomas, adenocarcinomas, and squamous cell
carcinomas; bronchiolar and alveolar metaplasia, adenomatous
lesions, fibrosis, and interstitial pneumonia were also observed.
When administered by inhalation in combination with decay products,
uranium-ore dust, and cigarette smoke, radon-induced nasal
carcinomas, epidermoid carcinomas, bronchio-alveolar carcinomas, and
fibrosarcoma were observed in dogs of both sexes. In general, a
significant increase was observed in respiratory tract tumors in
rats and dogs in comparison with unexposed animals. A dose- response
relationship was noted in those experiments with rats in which radon
was tested. In most instances, tumors at sites other than the lung
were not reported, but in one study, mention was made of tumors of
the upper lip and urinary tract in rats.
An IARC Working Group reported that there is sufficient evidence
for the carcinogenicity of radon and its decay products in humans.
Increased incidences of lung cancer have been reported from numerous
epidemiologic studies of groups occupationally exposed to high doses
of radon, especially underground hard rock miners. These include
particularly uranium miners, but also groups of iron-ore and other
metal miners, and one group of fluorspar miners. Strong evidence for
exposure response relationships has been obtained from several
studies, in spite of uncertainties that affect estimates of the
exposure of the study populations to radon decay products. Several
small case-control studies of lung cancer have suggested a higher
risk among individuals living in houses known or presumed to have
higher levels of radon and its decay products than among individuals
with lower presumed exposure in houses. The evidence on the
interaction of radon and its decay products with cigarette smoking
with regard to lung cancer does not lead to a simple conclusion. The
data from the largest study are consistent with a multiplicative or
sub-multiplicative model of synergisms and reject an additive model.
In many studies of miners and in one of presumed domestic exposure,
small cell cancers accounted for a greater proportion than expected
of the lung cancer cases. In one population of uranium miners, this
proportion has been declining with the passage of time. Because of
the limited scale of epidemiologic studies of non-occupational
exposure to radon decay products available at the time reviews were
made, quantification of risk has been based only on data of miners'
experience. An IARC Working Group considered that the epidemiologic
evidence does not lead to a firm conclusion concerning the
interaction between exposure to radon decay products and tobacco
smoking. Most of the epidemiologic studies involve small numbers of
cases, and the analytical approaches for assessing interaction have
been variable and sometimes inadequate.
PROPERTIES
Radon was discovered in 1900 by Friedrich Ernst Dorn, (Germany).
Named after the element "radium" (radon was called niton
at first, from the Latin word "nitens" meaning
"shining") but has been called radon since 1923. It is an
essentially inert, colorless, odorless gas at ordinary temperatures.
Its melting point is 202 degrees K and the boiling point is 211
degrees K. When cooled below the freezing point radon exhibits a
brilliant phosphorescence which becomes yellow as the temperature is
lowered and orange-red at the temperature of liquid air.
The atomic radius is 1.34 angstroms and it is the heaviest known
gas, being nine times denser than air. Because it is a single atom
gas (unlike oxygen, O2, which is comprised of two atoms) it easily
penetrates many common materials like paper, leather, low density
plastic (like plastic bags, etc.) most paints, and building
materials like gypsum board (sheetrock), concrete block, mortar,
sheathing paper (tarpaper), wood paneling, and most insulation.
Radon is also fairly soluble in water and organic solvents. Although
reaction with other compounds is comparatively rare, it is not
completely inert and forms stable molecules with highly
electronegative materials. Radon is considered a noble gas that
occurs in several isotopic forms. Only two are found in significant
concentrations in the human environment: radon-222, and radon-220.
Radon-222 is a member of the radioactive decay chain of uranium-238,
and radon-220 is formed in the decay chain of thorium-232. Radon-222
decays in a sequence of radionuclides called radon decay products,
radon daughters, or radon progeny. It is radon-222 that most readily
occurs in the environment. Atmospheric releases of radon-222 results
in the formation of decay products that are radioisotopes of heavy
metals (polonium, lead, bismuth) and rapidly attach to other
airborne materials such as dust and other materials facilitating
inhalation.
USE
Radon is a noble gas. Only two of its isotopic forms are found in
significant concentrations in the human environment: radon-222 and
radon-220. Their decay products are not gases and occur as
unattached ions or atoms, condensation nuceli, or attached to
particles. This decay product of uranium-238 is commonly found in
uranium mines. Radon has been used in some spas for presumed medical
effects. In addition, radon is used to initiate and influence
chemical reactions and as a surface label in the study of surface
reactions. It has been obtained by pumping the gases off of a
solution of a radium salt, sparking the gas mixture to combine the
hydrogen and oxygen, removing the water and carbon dioxide by
adsorption, and freezing out the radon.
PRODUCTION
Radon is not produced as a commercial product. Radon is a
naturally occurring radioactive gas and comes from the natural
breakdown (radioactive decay) of uranium. Most soils contain varying
amounts of uranium. It is usually found in igneous rock and soil,
but in some cases, well water may also be a source of radon.
EXPOSURE
The primary routes of potential human exposure to radon are
inhalation and ingestion. Radon in the ground, groundwater, or
building materials enters working and living spaces and
disintegrates into its decay products. In comparison with levels in
outdoor air, the concentrations of radon and its decay products to
which humans are exposed in confined air spaces, particularly in
underground work areas such as mines and buildings, are elevated.
Although high concentrations of radon in groundwater may contribute
to human exposure through ingestion, the radiation dose to the body
due to inhalation of radon released from water is usually more
important. Concentrations of radon decay products measured in the
air of underground mines throughout the world vary by several orders
of magnitude. In countries for which data were available,
concentrations of radon decay products in underground mines are now
typically less than 1000 Bq/m3 EEC Rn (approx. 28 pCi/l). The
average radon concentrations in houses are generally much lower than
the average radon concentrations in underground ore mines. Workers
are exposed to radon in several occupations. Underground uranium
miners are exposed to the highest levels of radon and its decay
products. Other underground workers and certain mineral processing
workers may also be exposed to significant levels. Exhalation of
radon from ordinary rock and soils and from radon- rich water can
cause significant radon concentrations in tunnels, power stations,
caves, public baths, and spas. Peripheral lymphocyte chromosomes
from 80 underground uranium miners and 20 male controls in the
Colorado plateau were studied. Taken into account were confounding
factors such as cigarette smoking and diagnostic radiation. Groups
that were increasingly exposed to radon and its decay products were
selected. Significantly more chromosomal aberrations were observed
among miners with 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.
The Environmental Protection Agency (U.S. EPA) and the Surgeons
General's Office have urged widespread testing for radon. They
estimated that as many as 20,000 lung cancer deaths are caused each
year by radon. Next to smoking, radon is the second leading cause of
lung cancer. EPA says that nearly 1 in 3 homes checked in seven
states and on three Indian lands had screening levels over 4 pCi/L,
the EPA's recommended action level for radon exposure.
Radon is a national environmental health problem. Elevated radon
levels have been discovered in virtually every state. The EPA
estimates that as many as 8 million homes throughout the country
have elevated levels of radon. State surveys to date show that 1 out
of 5 homes has elevated radon levels. Radon seeps into homes from
the surrounding soil through cracks and other openings in the
foundation. Indoor radon has been judged to be the most serious
environmental carcinogen to which the general public is exposed and
which the EPA must address. Based on current exposure and risk
estimates, radon exposure in single-family houses may be a causal
factor in as many as 20,000 of the total lung cancer fatalities
which occur each year. Radon decay products (polonium- 218 and
polonium-214, solid form) can attach to the surface of aerosols,
dusts, and smoke particles which may be inhaled, and become deeply
lodged or trapped in the lungs. Once lodged, they can radiate and
penetrate the cells of mucous membranes, bronchi, and other
pulmonary tissues.
Some scientific studies of radon exposure indicate that children
may be more sensitive to radon. This may be due to their higher
respiration rate and their rapidly dividing cells, which may be more
vulnerable to radiation damage.
RADIOACTIVITY - SUMMARY
The spontaneous disintegration or decay of the nucleus of an atom
by emission of particles, usually accompanied by electromagnetic
radiation. Natural radioactivity is exhibited by several elements,
including uranium, radium, radon gas, and radon's daughters. The
radiation produced is of three types: the alpha particle with
relatively weak penetration power, which is a nucleus (two protons
and two neutrons) of an ordinary helium atom; the beta particle with
moderate penetration power, which is a high-speed electron or, in
some cases, a positron (the electron's antiparticle); and gamma
radiation, which is a type of electromagnetic radiation with very
short wavelengths resulting in very high penetration power. The rate
of disintegration of a radioactive substance is commonly designated
by its half-life, which is the time required for one half of a given
quantity of the substance to decay.
For example, if you had a two liter bottle (think of the large
soda bottle in the fridge) that was filled with radon gas and then
tightly sealed, at the end of one half-life (approximately 92 hours
or almost 4 days) there would only be one liter left in the bottle.
Another issue to consider is the *unusual* property of the
radioactive decay chain of uranium/radium/radon. What makes this
seem unusual is that a gas is produced from a radioactive solid
element (a rock) and then the radioactive gas changes back into
radioactive heavy metallic particles. This process and their atomic
size (extremely small) makes possible the transport of radioactive
atoms through a relatively static environment. In other words,
radon's extended half-life (it takes about a month for a specific
amount of it to decay to almost nothing) provides enough time for
the gas to migrate through cracks and crevices in building
foundations, then into the internal air volume where it changes into
the more harmful radioactive heavy metals.
This gas and the resulting very small metallic particles (so
small that they will float in air) move quickly through a building
or home, contaminating the air. An analogy that makes this easier to
understand is to think how easily some can detect the presence of a
smoker in another part of the building or the cooking of coffee or
bacon in the kitchen on Sunday morning. In other words, almost
nothing will stop this gas from moving from the basement to other
parts of a house if it makes its way into the basement in the first
place. Contact us for more information: EagleEye@ee-hi.com

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