Visible crew/equipment: When Lex is driving out of the dam and the police arrive, Lex exits his car and two crew members heads are reflected in the glass window of his door. (02:35:30)
Continuity mistake: When Clark looks at Phillipe's police report, there is a photo of Phillipe facing sideways. In the next shot the photo has changed, so that now he is facing forward. (02:21:10)
Continuity mistake: When the Phantom child kills the doctor and drags him over to the fingerprint scanner to open the door, we see the doctor has no glove on his hand when it is placed on the scanner. But when his arm drops to the floor, there is a glove on his hand now. (02:32:35)
Continuity mistake: When Lois attack the guard down in the dam, she hits his face, which causes the black cap that the guard is wearing to begin to fall off. Yet in the next shot the hat is firmly back on his head, before it is completely knocked off by Lois' next hit. (02:23:00)
Continuity mistake: Shortly after their cell phone conversation, Lionel sees Lana and gets out of his car. In the next shots of Lionel, his car has moved position from behind him.
Continuity mistake: When Chloe finds Lois stabbed in the dam, we see Lois on the floor with her arm hanging so that her hand is right beside the stab wound. However in the next close up of the wound, her hand isn't there. It's back beside it in the next shot. (02:28:20)
Continuity mistake: When Lois is at the dam, looking at the card she previously tore, the numbers and markings are written differently than before.
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