So, Dean Domino (from Dead Money) survived the apocalypse. Good for him.
However, it seems to me that there's very little, if any, radiation in the Sierra Madre. Additionally, there's no other ghouls besides Dean, feral or otherwise. Just ghost people and the cloud.

So, how did this curious lack of radiation produce a ghoul? Unless Dean isn't a ghoul (he doesn't really have much of a ghoulish voice, either), but rather some kind of rational, free-willed ghost person, or perhaps a unique mutant like Harold and Talius?

Well, Dean IS clever, so perhaps he vaguely figured out to some extent what he is, and how to prevent massive rad inducing activity.

As I took it, the cloud purged the city of rads, and the cloud didn't envelop the city until after the war, so Dean could have ghoulified just after the initial mushroom cloud.

Maybe all of the other people that had been ghoulified were captured by ghost people (Dean says that they drag people into the cloud, from which they never return) or maybe they all died trying to get into the Madre.

Maybe Dean is a unique mutation. The DLC provides very few explanations. Its doubtful he's a ghost person though, as they are created by being fused with those creepy hazmat suits.

Ghooost People, Ghooost People, taste like ghosts, talk like people, Ghooost People...

Well there would've been radiation. Its just naturally faded in the 200 years since the war, as it should do.

IIRC the only radioactive areas in the Mojave are where theres an active source of Radiation nearby (like a faulty generator or leaking barrels), or in craters from bombs.

He looks like a ghoul, I just assumed that was all he was :shrug:

I too assumed he was a ghoul. But maybe.. Maybe a mutated ghoul! Radiation and The Cloud in his mixing bowl so he can survive those two harsh conditions.