BBC News reports the US is set to destroy its largest remaining cache of chemical-laden artillery shells, bringing it closer to complying with an international treaty. The Pueblo Chemical Depot in Colorado will begin neutralizing mustard agent in 780,000 shells in March. The 1997 Chemical Weapons Convention set a 2012 deadline to eradicate chemical weapons. Russia, Libya and Iraq are the only other countries with chemical weapons that have missed the deadline. Libya expects to finish in 2016 and Russia in 2020, according to the Organization for the Prohibition of Chemical Weapons. Iraq has no clear timeline.