Continuity mistake: As Pete demands Chloe's keys he raises the gun on her. As he does you can hear the sound of the hammer being pulled back on the revolver. In the shot of the gun, as Chloe gives him the keys, the hammer is not pulled back.
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: Right after Ryan makes breakfast for the Kents, he leans on a chair and sets the orange juice jug down twice. (00:05:35)
Continuity mistake: When Ryan gets hit by Martha's car, his comic book goes flying out of his hand. When he falls to the ground, he's holding his comic book again.
Other mistake: When Ryan gets hit by Martha's car, you can see he has both shoes on as he's going to the ground, and we never see a shoe flying through the air during the hit. Then James and Debra find the shoe in the middle of the street as they watch Martha drive off.
Revealing mistake: As Tyler slides across the floor, after Clark knocks him out of Whitney's father's room, he hits the camera. When he does the camera has a noticeable shake to it because of it.
Continuity mistake: In the intro to the final scene there is no light beneath the loft doors, yet at the end of the scene during the pullout a light has appear beneath them and it switched on.
Continuity mistake: In the intro to the final scene, the top half of the loft doors are open with the bottom half being closed, yet at the end of the scene during the pullout, both the top half and the bottom half of the doors are open.
Plot hole: Justin's power is telekinesis, which he uses to attack the doctor at the beginning of the episode. He shows that he is targeting the doctor's hands by blacking them out on the drawing, but he has absolutely no way to see what is happening in the elevator to know the exact moment when to drop it and cut them off. (00:03:30)
Continuity mistake: As Chloe hurries to put Justin's art book back before Justin comes in there is a piece of white paper sticking out of the top and bottom, based on the way she put it back, of the folder. When Justin sees the folder has been moved there are no papers sticking out.
Continuity mistake: When Clark goes to Kwan's house the set of pathway lights on the left, the side where Justin pulled only one out, is gone. Earlier the lights ran down both sides of the driveway.
Continuity mistake: As Justin turns the spike end of the pathway light towards Principal Kwan, in the close up, the light is at a height that is just lined up with the light in front of it. After the shot change, the shot simply zooms out to include Justin on the right side of the screen, the light is now several feet higher than it was before.
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.
Revealing mistake: When the gas pipe explodes at the beginning before the credits, the camera goes to an aerial view. You can see that the explosion started from behind the gas pipes. (00:01:50)
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