First, players don't know don't know that. Second there are a number of short lived isotopes that do have Cherenkov glow. And it'll probably be the last thing a player ever sees. :-)

Silly thought. Maybe radiation damage is why trolls evolved regeneration.

As for evil, I try. I once had a spur of the moment opportunity to mess with the players. and they didn't catch it until they heard the story circulating in the taverns a month later.