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)
Continuity mistake: At the coffee shop when he intercepts Lex, Phelan suddenly acquires a cup of coffee from nowhere. (00:10:00)
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)
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