Fan Casting Toxin in The Dark Mind

On August 9th, 1945, a young boy and his mother fled to a fallout shelter to avoid an incoming nuke. Unfortunately during the rush to the shelter, the boy was separated by his mother, and before he could make it to the shelter, the big metal door shut tightly and locked. He turned to face the mushroom cloud in the distance in terror.....he felt sick. But....he survived. months passed, more atomic nukes mutating his body to the point he thrived off the radioactive, toxic air around him, and would preserve his youth. Now in the modern day, he uses toxic weaponry to wreak havoc while being supported by an oxygen mask that pumps radioactive and toxic air into his lungs.