Mutants exist to some degree. While normal radiation would kill a person slowly, experimental medication to cure radiation was introduced into many water supplies by some unknown being. The medication stopped the radiation from killing the people, but began to grant them power. Slight abilities, heightened senses, weak precognition, nightvision and other useful talents would exist in a mutant, making them fairly normal. Many people fear mutants, but can not identify them, and many mutants hate people just for being normal.