Elements having atomic numbers greater than that of uranium are called transuranic. Elements within TRU are typically man-made and are known to contain americium-241 and several isotopes of plutonium. Because of the elements' longer half-lives, TRU is disposed of more cautiously than low level waste and intermediate level waste. In the U.S. it is a byproduct of weapons production, nuclear research and power production, and consists of protective gear, tools, residue, debris and other items contaminated with small amounts of radioactive elements (mainly plutonium).