DU or depleted uranium commonly used as armor piercing tips to bombs/rounds that need penetration such as bunker busters/armor piercing incendiaries, also causes quite a bit of environmental problems bro.

"In nature, uranium is found as uranium-238 (99.2739–99.2752%), uranium-235 (0.7198–0.7202%), and a very small amount of uranium-234 (0.0050–0.0059%).[4] Uranium decays slowly by emitting an alpha particle. The half-life of uranium-238 is about 4.47 billion years and that of uranium-235 is 704 million years,[5] making them useful in dating the age of the Earth."

[link to en.wikipedia.org]


How long does it take to clean up oil? I'm no rocket scientist but I don't think it's near 4.47 billion years.