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Keep risky rocks under wraps.

Keep risky rocks under wraps

Rock hounds beware. Those pretty crystals you collect may flood your home with radon.

Scientists at the Paul Scherrer Institute in Villigen, Switzerland, put an ad in a mineral collector's journal offering to measure radon levels in homes displaying minerals. Collecting crystals is a popular Swiss hobby, and many displays include minerals -- such as zircon, coffinite, carnotite, monazite, brannerite, titanite and pitchblende -- containing radon-emitting uranium or thorium.

The researchers placed radon detectors at five sites in each of 35 homes. In general, radon levels in rooms displaying crystals were 2.7 pCi/I higher than the already high background average of about 5.5 pCi/I, according to Reto Crameri, a molecular biologist involved in the study.

Radon-220, the isotope emitted by thorium, wasn't detected outside display cases of throium-rich minerals -- perhaps Crameri says, because this isotope decayed before it could leak out. The same was not true for uranium-bearing rocks. The radon-222 they emit has a half-life of nearly four days, more than 5,000 times longer than that of radon-220. Crameri says the Swiss data, reported in the September HEALTH PHYSICS, suggest rock collectors might consider sealing their display cases with tight-fitting rubber gaskets and venting showcase air outdoors.

The Swiss findings did not surprise Richard E. Toohey, health physics manager at Argonne (Ill.) National Laboratory. Mineral collections in some university geology departments "would have to be labeled as radiation areas if the [source of that] radiation were not naturally occurring," Toohey observes. He recommends that people consider shielding any rock collections -- including rock walls or the crushed granite used in passive solar-hearing systems -- before investing in other radon-control strategies.
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Title Annotation:radon emission
Publication:Science News
Date:Nov 11, 1989
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