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Radon Gas


Radon is a naturally occurring, inert, radioactive gas, derived from naturally occurring uranium deposits in the earth. It is colorless, odorless, and tasteless


Radon-222 is the environmentally important form or radon. Radon-222 is a decay product of uranium-238 and is the immediate daughter of radium-226. It has a physical half-life of 3.82 days.

Radon-222 decays by alpha emission into several short-lived daughters, most notably polonium-218 and polonium-214, which have half-lives of 3.1 minutes and 0.164 milliseconds, respectively. Both polonium daughters are highly reactive alpha emitters. Most radiation received by the body comes from the alpha articles. The ultimate decay product is stable lead-206.

Radon itself is not particularly harmful, but some of its alpha-emitting polonium radioactive decay products may heavily irradiate bronchial epithelial cells for many months or years. Therefore, radon is believed to be a risk factor for lung cancer.


Radon-222 enters the indoor environment from the soil by penetration of a building's foundation or by release from well water. The equilibrium levels that are achieved depend on rates of replenishment, radioactive decay and ventilation.

Although the average indoor domestic radon level in North America is small, great variations exist. Some houses have radon levels higher than the control levels in underground mines. A survey of 11,600 homes in ten states indicates that as many as 21 percent of homes may exceed the maximum radon level suggested by the U.S. Environmental Protection Agency (EPA).

Many of these homes are in areas known to have high background levels of natural radiation. However, not all of the homes in such regions are affected, and not all of the affected homes are located in those regions.

Cumulative domestic exposure levels, therefore, can be quite variable, depending on the amount of time spent in the home and the percentage of that time spent in the high-radon areas of the home. Outdoors, the concentrations of radon gas are trivial.


Like all sources of ionizing radiation, radon gas is odorless and thus not easily detected.

Although there are more than 700 U.S. companies that offer radon-measuring devices, no national legal standard exists for these devices. Many are, however, certified by the Radon Measurement Proficiency Program of the Environmental Protection Agency.

The detection device is placed in the lowest livable level of the house (normally not the basement), left there for the prescribed length of time, and then sent to the manufacturer, who sends you a report.

Because radon levels vary from place to place in the house and from time to time during the year, it is recommended you buy at least two detectors, place them in the living room and bedroom, and take two readings - one in midsummer and one in midwinter. The average of the total readings is then a good estimate of year-round exposure.

Finding a radon testing kit may not be easy. Even so, University of Iowa researchers have found that the reliability of the available services varies widely. The two companies who services the Iowans found to be most reliable (there may be many others, since they tested only six systems in all) are Air Chek, Inc. (1-800-247-2435) and American Radon Services, Ltd. (1-800-272-3668). Individual state departments of health can also supply the names of reliable companies.


What are some of the symptoms of radon poisoning?

How do you test for radon?

Can the results be read easily, or do they need to be sent to a lab?

What can be done to reduce a high level of radon in the house?

Are there certain rooms in the house that are more likely than others to contain high levels of radon?

The most cost-effective way to reduce the incidence of radon-induced lung cancer appears to be to reduce the number of smokers (there appears to be some synergism between smoking and radon exposure).

Additional measures that might be considered include improving the ventilation systems in existing homes (particularly in parts of the country where risk has been identified) and modifying the requirements for the ventilation systems for new constructions.

Educating the population to do simple things, such as avoiding the use of basements as major living areas and discouraging the improper handling of actinide-containing mineral collections displayed in living areas, are further examples of potentially cost-effective intervention.