Continuity mistake: As Clark walks up to Lex you can see the tip of Lex's cue stick is 3-4 inches away from the rail. Before Clark picks it up the stick is now right up against the rail.
Continuity mistake: In the shot where Clark picks up Lex's cue stick, the balls on the table are spread out in an arch consisting of 4 balls. The shot switches to a low level shot looking at Lex and the balls at Lex's end, where the arch should be, are no longer forming an arch.
Continuity mistake: When Clark and Lex were talking about Helena while playing billiards, Clark picks up the stripped blue ball. They then continue to talk as he plays with the ball in his hand. He then puts it back on the table allowing it to roll but now its has changed into the cue (white) ball and the stripped blue ball can be see in the foreground right next to the side pocket and a stripped red ball.
Continuity mistake: Lex and Clark are playing pool. Lex misses his shot on the 12 ball and scratches which leaves the 12 ball near the pocket. After Clark gets the cue ball, he makes his shot on a different ball and the 12 ball that was next to the pocket is gone without it being knocked into the pocket.
Other mistake: When the Marine officer comes to Whitneys house, he introduces himself as Lt. McNulty, but he is wearing the insignia of a Captain.
Audio problem: While talking about Tina Greer's suicide after Chloe says "lit a match" you can hear Pete say "okay" but you see his mouth doesn't move with the word.
Revealing mistake: When Tina puts the necklace on Clark to disable him, he falls to the ground of his barn. As he is lying there, his collar is very dark, and his shoulder is lit up. Since the source of the green light is supposed to be the necklace, his collar should be the brightest lit.
Audio problem: When Whitney is tearing up the bathroom, he throws the door and we don't hear it land. I saw this on the DVD, so it was not a transmission problem.
Continuity mistake: After Clark sees Whitney and realizes that he may be Tina Greer the next scene is at the school newspaper The Torch. The first shot of the computer, as the camera pans past it, has a story about Whitney's return up front with the story about Tina Greer's "suicide" behind it. Even though nobody touches the computer in the time between shots the next shot of the screen has just the story on Tina Greer and Whitney's story is completely gone.
Visible crew/equipment: When Tina, disguised as Lana, throws Pete against the lockers, you can easily see that it's Pete's 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