Depleted uranium is an extremely dense, man-made, radioactive heavy metal that is left over after natural uranium is enriched to produce fuel for nuclear reactors and weapons. It has a number of military uses and the Army has acknowledged it is present on at least two of its installations in Hawaii: Schofield Barracks on Oahu and the Pohakuloa Training Area on the Big Island. It’s unclear exactly what the health and environmental implications are of having this material on the Islands, and therein lies the controversy.