Here's a potential use for unwanted or damaged compact disks: Set them aside as home radon detectors.
Radon is a radioactive gas that can accumulate in homes as it seeps from the soil or from building material, such as stone. Some studies have suggested that the alpha particles ejected when radon decays may rank second only to tobacco smoke as a source of lung cancer (SN: 8/15/87, p. 105).
Now for the CD connection. Dobromir S. Pressyanov of the St. Liment Ohridski University of Sofia, Bulgaria, and his colleagues investigated the capability of alpha particles to mark plastic as they collide with it. In the May Health Physics, the physicists describe exposing compact disks made from polycarbonate plastic to known quantities of radon. After a day, the researchers removed each disk's surface to a depth at which only alpha particles would have left a mark. Then they chemically treated the newly exposed plastic to enlarge each mark enough to make it visible with a regular microscope.
The density of the marks accurately indicated the amount of radon exposure, whether or not the disks had been inside plastic jewel cases, the researchers report. The data indicate that if the age of a disk and average temperature of a home were known, measurements of alpha particle etching in a compact disk could indicate radiation exposure from radon with an accuracy of about 10 percent, Pressyanov and his team claim. The disks could actually record a person's cumulative exposure over at least a decade.
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Dobromir S. Pressyanov
Faculty of Physics
St. Kliment Ohridski University of Sofia
5 James Bourchier Boulevard
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