Audio problem: Near the end, when Clark is surprised by the woman coming to say good bye, as he is working on the tractor the distinct sound effect heard is that of a ratchet wrench, but what he puts down is a normal wrench, not a ratchet wrench.
Audio problem: When Clark and Manhunter are in his Barn talking about how to stop Bizarro and figuring out the yellow sun can heal Clark, there is a beep of a watch or someting similar in the background, but neither Clark nor the Manhunter react to it, which means it happened off screen and unintentionally.
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