DETROIT (AP) — As the Takata air bag saga drags on, concerns are growing that tens of millions of U.S. drivers with cars that haven't been recalled could be at risk of death or injury from the potentially defective devices. Federal safety regulators last month confirmed that a South Carolina man's death in December was caused by a driver's air bag inflator that wasn't under recall. Since 2008, 14 automakers have recalled 24 million vehicles to replace the inflators, which can rupture in a crash, shooting metal shards at the driver and passengers. According to a law firm representing Knight's family, the crash was moderate and otherwise survivable. Knight's death fits into one prevailing theory about the cause of the ruptures: his truck was an older model, and spent a long period of time in a region with high humidity. Scott Upham, who runs a Rochester, New York, research firm that tracks air bag sales, estimates there are 50 million unrecalled Takata inflators on U.S.