WASHINGTON — The under secretary of the Army on Wednesday apologized for the military’s treatment of American service members exposed to chemical weapons in Iraq, and he announced new steps to provide medical support to those with lingering health effects and to recognize veterans who had been denied awards.

Under Secretary Brad R. Carson acknowledged that the military had not followed its own policies for caring for troops exposed to old and abandoned chemical munitions that had been scattered around Iraq, and he vowed improvement.

He also said that the Army had reversed a previous decision and approved a Purple Heart medal for a soldier burned by sulfur mustard agent, and that he expected more medals to be issued to other veterans after further review.

“To me, the scandal is that we had protocols in place and the medical community knew what they were, and yet we failed in some cases to implement this across the theater,” he said. “That was a mistake, and I apologize for that. I apologize for past actions and am going to fix it going forward.”