Radon is a radioactive gas which occurs in nature.
You cannot see it, smell it, or taste it.
Radon comes from the natural breakdown (radioactive
decay) of uranium. Radon can be found in high concentrations in soils
and rocks containing uranium, granite, shale, phosphate, and pitchblende.
Radon may also be found in soil contaminated with certain types of industrial
wastes, such as the byproducts from uranium or phosphate mining.
In outdoor air, radon is diluted to such low
concentrations that it is usually nothing to worry about. However, once
inside an enclosed space (such as a home) radon can accumulate. Indoor
levels depend both on a building's construction and the concentration
of radon in the underlying soil.
The only known health effect associated with
exposure to elevated levels of radon is an increased risk of developing
lung cancer. Not everyone exposed to elevated levels of radon will develop
lung cancer, and the time between exposure and the onset of the disease
may be many years.
Scientists estimate that from about 5,000 to
about 20,000 lung cancer deaths a year in the United States may be attributed
to radon. (The American Cancer Society expects that about 130,000 people
will die of lung cancer in 1986. The Surgeon General attributes around
85 percent of all lung cancer deaths to smoking.)
Your risk of developing lung cancer from exposure
to radon depends upon the concentration of radon and the length of time
you are exposed. Exposure to a slightly elevated radon level for a long
time may present a greater risk of developing lung cancer than exposure
to a significantly elevated level for a short time. In general, your
risk increases as the level of radon and the length of exposure increase.
With exposure to radon, as with other pollutants,
there is some uncertainty about the amount of health risk. Radon risk
estimates are based on scientific studies of miners exposed to varying
levels of radon in their work underground. Consequently, scientists
are considerably more certain of the risk estimates for radon than they
are of those risk estimates which rely solely on studies of animals.
To account for the uncertainty in the risk estimates
for radon, scientists generally express the risks associated with exposure
to a particular level as a range of numbers. (The risk estimates given
in this booklet are based on the advice of EPA's Science Advisory Board,
an independent group of scientists established to advise EPA on various
scientific matters.)
Despite some uncertainty in the risk estimates for
radon, it is widely believed that the greater your exposure to radon,
the greater your risk of developing lung cancer.
Radon, itself, naturally breaks down and forms
radioactive decay products. As you breathe, the radon decay products
can become trapped in your lungs. As these decay products break down
further, they release small bursts of energy which can damage lung tissue
and lead to lung cancer.
Radon has always been present in the air. Concern
about elevated indoor concentrations first arose in the late 1960's
when homes were found in the West that had been built with materials
contaminated by waste from uranium mines. Since then, cases of high
indoor radon levels resulting from industrial activities have been found
in many parts of the country. We have only recently become aware, however,
that houses in various parts of the U.S. may have high indoor radon
levels caused by natural deposits of uranium in the soil on which they
are built.
No, most houses in this country are not likely
to have a radon problem; but relatively few houses do have highly elevated
levels. The dilemma is that, right now, no one knows which houses have
a problem and which do not. You may wish to call your state radiation
protection office to find out if any high levels have been discovered
in your area.
Many states, as well as the federal government,
are sponsoring work to identify areas of the country which are likely
to have indoor radon problems. However, early results from this work
are inconclusive. If you are concerned that you may have an indoor radon
problem, you should consider having your home tested.
Radon is a gas which can move through small
spaces in the soil and rock on which a house is built. Radon can seep
into a home through dirt floors, cracks in concrete floors and walls,
floor drains, sumps, joints, and tiny cracks or pores in hollow-block
walls.
Radon also can enter water within private wells
and be released into a home when the water is used. Usually, radon is
not a problem with large community water supplies, where it would likely
be released into the outside air before the water reaches a home. (For
more information concerning radon in water, contact your state's radiation
protection office.)
In some unusual situations, radon may be released
from the materials used in the construction of a home. For example,
this may be a problem if a house has a large stone fireplace or has
a solar heating system in which heat is stored in large beds of stone.
In general, however, building materials are not a major source of indoor
radon.
Since you cannot see or smell radon, special
equipment is needed to detect it. The two most popular commercially-available
radon detectors are the charcoal canister and the alpha track detector.
Both of these devices are exposed to the air in your home for a specified
period of time and sent to a laboratory for analysis.
There are other techniques-requiring operation
by "- trained personnel-which can be used to measure radon levels, but
such techniques may be more expensive than the devices shown above.
Your measurement result will be reported to
you in one of two ways. Results from devices which measure radon decay
products are reported as "Working Levels" (WL). Results from devices
which measure concentrations of radon gas are reported as "picocuries
per liter" (pCi/I).
Homeowners in some areas are being provided
with detectors by their state or local government. In many areas, private
firms offer radon testing. Your state radiation protection office may
be able to provide you with information on the availability of detection
devices or services.
The U.S. Environmental Protection Agency conducts
a Radon Measurement Proficiency Program. This voluntary program allows
laboratories and businesses to demonstrate their capabilities in measuring
indoor radon. The names of firms participating in this program can be
obtained from your state radiation protection office or from your EPA
regional office.
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