exporting the vessels for shipbreaking, or dismantling. More recently, the U.S. Navy has established a program to allow ships, such as Oriskany, to be sunk in selected locations to create artificial reefs. Recycling is another option, as in the case of the United States National Defense Reserve Fleet (NDRF), the ships of which are set to be stripped of their paint, cut into pieces, and then recycled. Steel from pre-nuclear age ships either mothballed or sunk and raised, called low-background steel, is used in experimental physics when the experiment requires shielding material which is itself only extremely weakly radioactive, emitting less than present-day background radiation; materials which were manufactured after atmospheric nuclear explosions had taken place reflect the higher ambient level of radioactivity that fallout has caused. Environmental concerns The practice of exporting and dismantling ships has caused international protests as they contain toxic materials. In 2007, following studies that found that 20 tons of lead paint had flaked off the ships of the NDRF, environmentalist groups sued to have them removed. The U.S. Federal Maritime Administration agreed to remove more than 50 of the ships as a result, 25 of which have been removed by 2012 and the remainder removed at the end of 2017. See also Aircraft boneyard National Defense Reserve Fleet Suisun Bay Reserve Fleet United States Navy reserve fleets References Further reading Daniel Madsen. Forgotten Fleet. The Mothball Navy. U.S. Naval Institute Press. 1999. To Sail No More. Seven volumes. Maritime Books. United Kingdom. P.W. Singer and August Cole. Ghost Fleet. Mariner Books, Houghton Mifflin Harcourt. 2015. Naval fleets Naval ships Abandoned military projects of the United Kingdom