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 The Paul Scherrer Institute (PSI) is a multi-disciplinary research institute which belongs to the Swiss ETH-Komplex covering also the ETH Zurich and EPFL. It was established in 1988 by merging in 1960 established EIR (Eidgenössisches Institut für R 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 car·no·tite n. A yellow ore of uranium and radium with composition K(UO2)2(VO4)2·3H2O. , monazite monazite (mŏn`əzīt), yellow to reddish-brown natural phosphate of the rare earths, mainly the cerium and lanthanum metals, usually with some thorium. Yttrium, calcium, iron, and silica are frequently present. , brannerite, titanite ti·tan·ite n. See sphene. and pitchblende pitchblende (pĭch`blĕnd'), dark, lustrous, heavy mineral, a source of radium and uranium. Largely natural uranium oxide, UO2 and UO3, it usually contains some lead and variable amounts of thorium and rare-earth elements. -- containing radon-emitting uranium or thorium thorium (thôr`ēəm) [from Thor], radioactive chemical element; symbol Th; at. no. 90; at. wt. 232.0381; m.p. about 1,750°C;; b.p. about 4,790°C;; sp. gr. 11.7 at 20°C;; valence +4. . 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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