As a person who actually owns some plutonium (it occurs naturally in beryllium-uranium deposits, and can thus be owned), I'm not all that afraid of it. As a part of periodictabletable.com, we have perhaps a microgram or more of it, as part of a rock, in foam, sealed, behind lead. I check the whole area around the table with the geiger counter regularly, just to make sure nothing is above background levels. The element we are most afraid of is actually our non-radioactive Cesium sample. It's also the most beautiful, a wonderful liquid gold. If it even broke loose of the capsule it was in, we would have to deal with fantastically corrosive Cesium Hydroxide after the fires and explosions had stopped. We keep it locked up under Lexan plate. If you want radioactive danger, look no further than a smoke detector. The Americium inside is just as lethal as Plutonium. You can top that, though, by getting a static brush from a photography shop. The key ingredient of a static brush is Polonium. It's the most toxic thing you can buy in a store -- 250,000,000,000 times more lethal than hydrogen cyanide. Theo does extra research on the table, and he looked up the government standards at the NRC for many elements, including polonium, about various shipping standards. The NRC recommended that no more than 22 grams of polonium be shipped at a time. A calculation showed that they had erred... the actual safe shipping amount is a 1000th of that. Polonium is so radioactive that a 0.50 gram sample will reach temperatures greater than 500 degrees all by itself. The NRC sent Theo a nice note of thanks for catching the error in their official standards. On the other end of the scale, there are radioactive elements that have very, very long half lives. Bismuth was recently added to this list. Carbon and Potassium are much more radioactive. (John Walker wrote a nice article on Potassium at http://www.fourmilab.ch/documents/k40.html) Calcium 48 .187% 6E+18 yr http://chemlab.pc.maricopa.edu/periodic/Ca.html Chromium 50 4.3% 1.8E+17 yr http://chemlab.pc.maricopa.edu/periodic/Cr.html Zinc 70 .6% 5E+14 yr http://chemlab.pc.maricopa.edu/periodic/Zn.html Selenium 82 8.73% 1.08E+20 yr http://chemlab.pc.maricopa.edu/periodic/Se.html Krypton 78 .35% 2.0E+21 yr http://chemlab.pc.maricopa.edu/periodic/Kr.html Rubidium 87 27.8% 4.75E+10 yr http://chemlab.pc.maricopa.edu/periodic/Rb.html Zirconium 96 2.8% 3.9E+19 yr http://chemlab.pc.maricopa.edu/periodic/Zr.html Molybdenum 100 9.63% 1.2E+19 yr http://chemlab.pc.maricopa.edu/periodic/Mo.html Cadmium 113 12.22% 9.3E+15 yr http://chemlab.pc.maricopa.edu/periodic/Cd.html Indium 115 95.71% 4.41E+14 yr http://chemlab.pc.maricopa.edu/periodic/In.html Tellurium 128 31.6% 7.7E+24 yr http://chemlab.pc.maricopa.edu/periodic/Te.html Xenon 136 8.9% 9.3E+19 yr http://chemlab.pc.maricopa.edu/periodic/Xe.html So ... Tellurium 128 31.6% 7.7E+24 yr ... that isn't very radioactive at all. However, if tiny amount gets into your system, you'll suffer from months of dreadful smelling breath and appalling body odor if the dose is sublethal. So many things to worry about. Still, the next time you're near a blazing building, and the smoke detector has stopped going off, don't run into the flames! The cloud of vaporized Americium might kill you. --Ed Pegg Jr, www.mathpuzzle.com