Veterans’ groups are demanding the military inform as many as 400,000 troops they may have been exposed to hazardous depleted uranium from shells fired by U.S. tanks and aircraft during the Persian Gulf War. The National Gulf War Resource Center, in a study released yesterday, estimates at least 400,000 servicemembers had contact with depleted uranium either during combat, while recovering contaminated weapons, or while visiting the battleground after the conflict. Paul Sullivan, executive director of the center, which oversees 45 veterans’ groups, said veterans have been left twisting in the wind for seven years. He added, “We firmly believe this is a conservative estimate of those exposed.” The Defense Department has not yet reviewed the report, but a Pentagon spokesperson on Gulf War illness issues said the amount of exposure varies greatly.