Trivia: Tahmoh Penikett appears in this episode, and "Nemesis" as Wes Keenan, who gained super powers after being injected with the DNA of kryptonite-infected humans as part of Project Ares. Penikett also appeared in season 3 as Vince Davis, who came back to life after being given the Lazarus Serum, which was made from the blood of Clark Kent. The Lazarus Serum was a project by Lionel Luther and Project Ares was a project by Lex Luther.
Trivia: Chloe's mom in this episode is played by Linda Carter. Carter is known for playing Wonder Woman in the 1970's. Wonder Woman was one of the original members of the Justice League, but, like Batman, never appeared in "Smallville" and was only alluded to a handful of times.
Trivia: Aaron Ashmore appears for the first time as Jimmy Olsen. Aaron's twin brother, Shawn Ashmore, played Eric Summers in season 1 (and again in season 3). Aaron appeared throughout season 6,7, and 8, until Jimmy's death. Aaron would later play Jimmy's younger brother at the end of season 10. Incidentally, it was Shawn who played the superhero Iceman (Bobby Drake) in the X-Men films.
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