Continuity mistake: In the kitchen, Martha collapses and Clark catches her just in time. Jonathan then rushes to his wife and puts his right hand on her cheek and his left hand on Clark's shoulder. Cut to a close up of Martha as Jonathan calls her name but now he has both his hands on Martha's face.
Continuity mistake: As Clark walks into his grandfather's motel room, his hands are behind his back. He turns to face his grandfather and both hands are now in front of him holding the photo album. The next shot shows him in the foreground raising his left arm from his side to hold the album. (00:31:30)
Continuity mistake: For several shots during the early scene with the baby in the crib, the blanket changes back and forth from tucked up to the chin, up to the shoulders, and up to the stomach in different angles. (00:01:55)
Continuity mistake: When Bad Lex is beating up Good Lex in the cellar right before their bodies are joined again, he repeatedly hits him on the right side of his face. However, when the two are finally fused back together, there is a bruising on the left side of Lex's face.
Continuity mistake: When Chloe is kissing Justin the shot is behind him and her hands are not on his neck. The shot switches to behind Chloe and she does have her hands on his neck.
Continuity mistake: After Lex tells Martha that he'll do whatever he can to help Jonathan, she goes into Jonathan's hospital room. As she goes through the door, the blinds next to the door are closed. When the shot switches to show Clark standing at the other window, the blinds next to the door are open. Then, as Lex goes over to Clark, the blinds next to the door are closed again.
Continuity mistake: When Jonathan shoots Clark with the shotgun, in the slow motion shot of Clark as he first starts to take the hit there is nothing coming out of the gun or on his chest. When the shot moves to Clark's left he now has red hot shot fragments on his chest.
Continuity mistake: After the encounter in the meat locker, Lex and Clark talk outside Fordman's store. As Lex turns to leave there is a truck driving down the street in Clark's direction. When the camera switches to Clark, the truck, which should be in this shot going behind Clark, is nowhere to be seen.
Continuity mistake: Lex whispers into his father's ear something about keeping secrets. At first the view is of him less than an inch away from his ear. In the next shot he's at least six inches away.
Continuity mistake: At the beginning, as the mother tucks the blanket up to the child's neck, she changes from both hands on the infant to one hand on the crib. (00:01:55)
Continuity mistake: When Ian is dragging Lana towards the dam, his double can be seen in the background dragging Chloe. The double is on Chloe's right side pushing her. Cut to a close up as Chloe says "Ian you need help" but now the double is behind Chloe and is pulling her.
Continuity mistake: In the CG shot of the shotgun shot flying in slow motion towards the camera, the blue florescent light that was swinging in the previous shots is gone.
Continuity mistake: When Clark sees that Jeremiah is in the loft, Clark stands up and closes the book he was reading as he says "What are you doing here?". The very next shot from behind Clark shows that the book is back to being open.
Continuity mistake: Martha asks Clark to come out after he gets glasses. In the shot showing all three of them, Clark comes into view on the left side of the screen and is turned toward his parents. The very next shot shows he is just walking through the door of the optometrist and turned away from his parents as he closes the door.
Continuity mistake: As Emily lies on the ground unconscious after being hit with the water, she is first shown lying there with her right arm bent up and her hand up by her head. After a quick shot of Clark she now has her right hand down by her side.
Continuity mistake: As Clark says "Eve Andrews was wearing two earrings when she died," during the line there is a camera change. Before the change Lionel has both arms on the table, but after the change he has one arm up examining the earring.
Continuity mistake: As Jonathan and Martha drive away in the truck, we see Rachel for the very first time and she has both her hands in her coat pockets. Cut to a close up but now her hands are outside the coat pockets.
Continuity mistake: When Sean is in the nurses office, having his temperature taken, the light on his left side is on. After the nurse wants to retake the temperature the light is now off.
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