Revealing mistake: Once Victoria has drawn her bath, we see her get in, and then lean back into the water. However she is already wet on her chest and her hair is damp already. This is probably due to previous takes of the same scene.
Revealing mistake: When Lana throws a glass bottle at Lex (in the Talon) it smashes against the wall. But if you look closely Lana drops the bottle just before she throws it.
Revealing mistake: As Tyler slides across the floor, after Clark knocks him out of Whitney's father's room, he hits the camera. When he does the camera has a noticeable shake to it because of it.
Revealing mistake: While Lana is listening to her Mother's graduation speech she reaches up to her neck for her meteor rock necklace. Her hands do not reach far enough back to unclasp the necklace yet the necklace comes off anyway.
Revealing mistake: In the early scene with the baby, there are a few overhead shots of the parents and child. It is clear that in these shots a fake baby was used - he is completely motionless, even though he was moving arms and legs before and after and is crying. (00:02:00 - 00:03:15)
Revealing mistake: As Tina/Clark tries to run over Martha, there is a shot of Tina/Clark up close in the truck, and the gear shift is still in park.
Revealing mistake: The Smallville Torch that Clark looks at online is the exact same one last seen by Lex two episodes ago in "Craving." This wouldn't be a problem, but Clark remarks that this Torch is "another scathing editorial," indicating that it is new, and Principal Kwan complains that parents have been calling all morning, which means that this issue of the Torch was published either this day or the day before. Prop department must have been saving money. (00:08:40)
Revealing mistake: When the gas pipe explodes at the beginning before the credits, the camera goes to an aerial view. You can see that the explosion started from behind the gas pipes. (00:01:50)
Revealing mistake: At the command center outside Martha is watching a monitor with the hostages on it and she asks "Where's Clark?". The next shot is one of Clark running down a hallway, inside the plant, using his super-speed. As he is running the red lights along the ceiling are revolving faster than they normally do and return to normal once Clark stops using super-speed.
Revealing mistake: In "Rogue," just after Jonathan has been arrested, Clark walks into the house and punches a wooden beam. If you look closely, you can see the crack in it where it has already been broken. (00:26:35)
Revealing mistake: When Clark gets hits by lightning whilst trying to save Eric, you can see that Eric is a stunt double.
Answer: The kryptonite only creates mutations when it reacts with the environment and an individual. Remember, the FDA and several environmental groups did check out Smallville after the meteor shower, but found no danger in the rocks. Obviously they're not always emitting mutating rays, or all the flora and fauna of the surrounding area would be horribly mutated.
Phoenix