User blog comment:Miskos3/Fairy Tail Chapter 486: The Fourth Guest, Review/@comment-7418318-20160525151848/@comment-5894890-20160526172714

Thing is, no matter how much he says he's made of iron, there's no way he can be fully iron. He's a human after all; he bleeds. The fact that his lung's are made of iron shouldn't even matter, the lungs simply help the oxygen enter the cells in the blood. Unless, it some how acts as a filter, the MBP stuff will still enter his body/ his bloodstream. His fight with Torafusa some-what made sense, he was able to block out all the particles from entering his body by sealing his mouth, and I assume, his outer body acts as an outer-protective iron shell itself, so it's not absorbing stuff. So, some resistance there. Right now, he's simply saying his lungs are made of iron, which for who knows how, correlates with it not entering his body. I agree, that this isn't something that really focus on, but it's also these little things that bother me.