The United States will provide depleted uranium tank ammunition to Ukraine as part of a $175 million aid package, the Pentagon said on September 6. The 120-millimeter rounds are for the U.S. M1 Abrams, the Pentagon said, referring to tanks that Washington has promised to Kyiv. The density of uranium -- about 1.7 times that of lead -- helps such ammunition punch through heavy armor. But depleted uranium is controversial due to its association with health problems such as cancer and birth defects, though the munitions have not been definitively proven as the cause.