Seawater contains about 3.3 parts per billion of uranium by weight as uranium (VI) forms soluble carbonate complexes. Extraction of uranium from seawater has been considered as a means of obtaining the element. Because of the very low specific activity of uranium the chemical effects of it upon living things can often outweigh the effects of its radioactivity. Additional uranium has been added to the environment in some locations, from the nuclear fuel cycle and the use of depleted uranium in munitions.