DU emits mainly alpha particles, which are blocked by skin, while beta particles are blocked by military clothing and boots. Gamma rays, though highly penetrating, are given off in extremely low amounts. When uranium is ingested, the kidney is the main organ that is targeted. But even wounded Gulf War veterans who have DU fragments imbedded in their bodies suffered no kidney disease attributable to uranium's chemical toxicity, according to a 1999 rand report. Nor do the men appear to show any signs of radiation effects.
Epidemiologists call it a cluster.
Cancer clusters have been identified for well over a century, and a large number involve leukemia. Some experts think leukemia may need only two. Unlike the Gulf War illnesses, the DU cases have spawned investigations shortly after the first signs of trouble. That, to soldiers and their families, officials and scientists, is an important first step. For others, the studies and guidelines on how to deal with DU material have come too late.