Continuity mistake: Lana was found shot in her upper left shoulder but at the end of the show she has a sling on her right arm. (00:42:00 - 00:43:05)
Continuity mistake: When Chloe and Jimmy find Lana shot in the elevator, there is a gun on the floor beside her, with a small pool of blood beside in the gun. In the next closeup shot on the floor, the small pool of blood is gone. (00:42:00)
Audio problem: When Jimmy is in the 1940s Talon we can hear the sound of a saxophone in the number before Lois arrives. Nevertheless, as we can see on the stage, there are only three instrument: a drum, a piano, and a bass. (00:52:00)
Audio problem: When Noir-Lois comes out to sing, the microphone picks up her voice before she's anywhere close enough for it to do so. (00:52:30)
Continuity mistake: When Lana hands the gun to Jimmy, she hands it to him aimed away from her. When Jimmy takes it, it is aimed towards her. (00:59:00)
Continuity mistake: When Chloe shows the newspaper to Jimmy with his photo on it. The photo is not the same when it is shown in the close-up.
Continuity mistake: At the beginning of the episode, we see that the clock reads 2 o'clock. Jimmy then takes Chloe into the back room to his set-up movie date. A little into the scene, they then hear a gunshot. When they rush out, the clock now reads 4:15. However Chloe and Jimmy were not in the back room for this long. At 4:15 they find Lana shot, and call 911. Then after the credits, we return to the scene, but now the police have arrived. But now the clock reads 2:15. There is no way the police would have taken so long, that the clock would have jumped all the way around from 4:15 to 2:15, therefore the continuity on this clock is mixed up.
Other mistake: When Jimmy wakes up in 1940, on his desk calendar it's Saturday the 3rd. The newspaper says it's May 3rd, 1940, but that was a Friday.
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