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Physics Student Up for the Count

Contact: Nick Houtman, Dept. of Public Affairs, 207-581-3777,

ORONO–Paul Smitherman is counting on radon. The radioactive gas has been the subject of research at the University of Maine and elsewhere for more than 20 years, largely as a potential health risk in homes, schools and work places. No one, however, has yet to satisfactorily explain the behavior of what Smitherman, a U.S. Air Force veteran, calls “the radioactivity right outside your window.”

In June, 2004, Smitherman set up a monitoring device outside Bennett Hall on the UMaine campus to monitor radon continuously. Once an hour, day or night, rain or shine, a computer that Smitherman programmed retrieves data from the device and posts it and a graph of daily averages to a website ( His advisors are physicists Charles T. Hess and James McClymer.

As of mid-December, radon levels varied between 0.5 picocuries per liter (a measurement of radioactivity) and near 0. The U.S. Environmental Protection Agency (EPA) estimates the average outdoor radon concentration in the U.S. to be about 0.4 picocuries per liter.

“We live in a sea of (natural) radioactivity,” says Smitherman, a senior in the Dept. of Physics and Astronomy, “but radon in the atmosphere is not fully understood.” While a few continuous radioactivity monitoring stations have been established around the United States such as at Princeton, New Jersey, most such efforts have been conducted for short periods of time.

Because weather conditions are thought to influence radon measurements, Smitherman hopes to shed light on the relationship between radon and factors such as air pressure, wind speed, relative humidity, temperature and precipitation. He is taking advantage of the department’s weather station mounted on the roof of Bennett Hall. Weather data can be seen at

At 41 years old, Smitherman is what admissions offices call a “nontraditional student.” Before coming to UMaine, the father of three served a four-year stint as a radar technician in the U.S. Air Force. As a civilian, he has lost jobs in the computer and paper industries in Maine as a result of economic trends. Now, he is studying environmental radioactivity to lay the foundation for a career based in science.

“I like math and really getting into a problem in detail. I feel so lucky to have found myself in a place where I can do that,” he says.

Radon is a breakdown product of uranium-238 and exists commonly in the soil and groundwater as an inert gas. Since it doesn’t react with other soil chemicals, says Smitherman, it can move through the soil and into the air or into homes where, at high enough levels, it can pose a health risk.

According to the EPA, radon is the second leading cause of lung cancer. The agency has designated January as National Radon Action Month to encourage homeowners to test the air in their homes. A University of Maine publication, Radon in Water and Air, is available on the Internet at

Other sources of natural radioactivity include potassium-40, a common component of soil and food, and cosmic rays. Because radon emits a positively charged alpha particle as it decays, it is relatively easy to detect.

Smitherman would like to continue studying radon in graduate schools. Another challenge, he says, is detecting neutron radiation. Since they have no charge, neutrons can pass easily through most materials. Neutron radiation technology has applications in homeland security where it can be used to inspect cargo.


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The University of Maine
Orono, Maine 04469
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