Revealing mistake: While there was a close up on Clark while he was asleep, you could see a small cut right above his eye, which is impossible if he can't be hurt.
Revealing mistake: Lana and Clark are supposed to be skinny dipping at Crater Lake. When Clark pops up out of the water and goes "boo" to Lana she spins around and splashes Clark for making her worry. As she starts to splash Clark her body comes out of the water far enough to see she is wearing a tan tube top instead of actually skinny dipping.
Revealing mistake: When Nicholas throws the lighter it is supposed to be lit so that it will light the gas and kill Lana but as it flips through the air, before Clark grabs it, the lighter has no flame at all.
Revealing mistake: At the beginning of this episode Lana is supposedly naked. However, when she dives off of the pier, she is wearing a pair of red shorts.
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