It is unlikely that scientific advice has changed over the previous day. The only rational explanation for this turnaround is that there has been political advice to succumb to media demands. Between March and June 1999, thousands of 35mm calibre rounds, stuffed with depleted uranium, were fired over Kosovo, mainly by the American A-10 aircraft. This depleted uranium is much less radioactive than natural uranium normally present in the soil and rock. Natural uranium is in equilibrium with radioactive isotopes of radium, radon, thorium, protoactine, polonium, lead and bismuth.
Alpha particles have little penetrative power in the air and in human tissues.
The total mass of depleted uranium dispersed over Kosovo was at most 25 tons. Thus, 1cm-thick layer of soil in Kosovo contains about 300 times more natural uranium than was dispersed there by NATO, mainly American, weaponry. However, at the target sites, the local concentrations of depleted uranium may be higher than the average concentration of natural uranium in the soil. From these patches of activity depleted uranium may be re-suspended into the air, and also enter the food chain. But this should not lead to any observable medical consequences.