Character mistake: While Clark and Chloe are at Daily Planet, Clark asks her what is wrong with her mother. Chloe responds that her mother left when she was twelve years old. In the episode Lineage, Chloe and Clark are looking for Rachael Dunleavy and Chloe says her mother left when she was five.
Plot hole: Clark uses his X-Ray vision to see the remains of the girl in the wall, which seems to establish the wall is not made with lead. However, he only reacts to the Kryptonite bracelet inside until he is aware it is there, despite the fact he should have been able to feel its effects long before that.
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