This has been brought up recently because of Snyder's current work and a line from Amanda Waller in Suicide Squad.
Waller referred to Batman as a Meta human.
Snyder is writing about a metal that when in the bloodstream makes someone more skilled than they previously were (mentioned with Batman) or have powers (Duke/Signal.) Bruce apparently got the metal into his system when he was brought back to life. It's been said to be in the Lazarus Pits meaning everyone that used them are Metas too? Then why does Ra's always need to go back? That sounds more like a drug unless the body can keep the metal in the system.