Nuclear Deterrence

Look at the black and yellow symbol on the right. Is it a fan? A propeller? No. It's a trefoil, the international sign used to warn people away from potentially deadly sources of radiation. If you didn't recognize the degree of danger that is supposed to be conveyed by the three-bladed symbol, which represents radiation emitting from an atom, you're not alone. Over the last two decades, at least 20 people have died and more than 400 have been injured after accidentally exposing themselves to radioactive sources, such as radiography units dumped in scrap heaps. Experts believe that the final toll is probably much higher, as many incidents often go unreported or are misdiagnosed.

To help reduce these avoidable deaths, the International Atomic Energy Agency in Vienna unveiled a new warning symbol on Feb. 15 to label potentially fatal radiation sources, such as those found in food irradiators or machines for cancer treatment. Unlike the original trefoil, which was first developed by scientists at the University of California, Berkeley, in the 1940s, the new warning was tested to ensure it's universally understood. Starting in 2001, researchers showed a series of motifs to 1,650 adults and children, many of them illiterate, in 11 different countries. The red background conveys danger; a skull and crossbones and a trefoil emanating rays warns of a threat to life; a running man tells observers to keep away. "We can't teach the world about radiation," says Carolyn MacKenzie, a radiation specialist who helped develop the new symbol. "But, for the price of a sticker, we can help save lives."