Continuity mistake: While talking about what to name the dog there are several shots of the dog and the metal chain is gone. Then, right at the end of the scene, as the dog puts his paw over his nose, the chain is back.
Continuity mistake: When checking out the armored car robbery, Clark tells Lois to turn left. We then go to on out of car shot where the big red letters of the GMC that Lois is driving are visible. When the 4x4 skids to halt shot its GMC logo is covered in black tape.
Continuity mistake: Before Clark throws the two bad guys against the side of the barn there is no snow falling at this point. When the shot switches to Krypto saving Hercules you can see that now it is snowing rather heavily. This is far too fast to happen naturally.
Continuity mistake: The guide that was with Lana gets killed by soldiers. When the guide is shot you can hear that the weapon has a silencer on it. About a second later we see this still smoking gun has no silencer on it.
Continuity mistake: As Clark first gets to the bridge at Cherry Hill, the shadows establish the time as either early morning or early evening since the shadows are long. In several shots during this scene the sun suddenly jumps to around noon as the bridge shadow goes from sticking out far to one side to being almost directly under the bridge and the shadow of the semi shortens when Clark is making his super jump.
Continuity mistake: In the barn loft evil Lex has a kryptonite ring in a lead box. When the camera is in front of Lex he is holding the box so that the lid is pointed towards his thumb. When the camera is behind Lex the box is turned so that the lid is pointed towards the end of his fingers.
Continuity mistake: As the computer says "Subject seeds exposed to radiation" there is a camera shot showing the temperature monitor in the lower right of the shot. In that shot the readout shows the temperature reading is close to 100% of maximum. Then, in the next shot as the scientist says ".absorption level: as expected" the temperature monitor is now close to 90% as we see it climb up to the 98% they were trying for.
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: Jonathan reveals the kryptonite to Clark/Dawn and Clark starts to react to it. Because of the kryptonite Clark drops the tiara he took from Chloe and it hits the floor near Chloe's hand. Then, just before Dawn is forced out of Clark's body, the tiara has slid several feet away and is now close to the furnace. Clark turns his attention to Chloe, she is faking an injury at this point, but now the tiara has moved back to be near her hand.
Continuity mistake: Jason accesses Lex's computer and Lex catches him. After a discussion on an email Jason found Lex says "Burying ladies in the backyard isn't exactly a hobby of mine, Jason." Lex then just stands there staring at Jason. During their stare down the camera jumps back behind Lex and then back to behind Jason. During these camera changes the lighting on the left side of Lex's face changes. When the camera is behind Jason, Lex's left side is dark. When the cameras is behind Lex, Lex's left side is lit up.
Continuity mistake: Lana looks over the edge of the crater and there is a fire right in front of her on the inside rim of the crater. When the shot changes and pans up to an overhead view of the crater and ship that fire is missing.
Continuity mistake: Clark had been wearing his cap and gown for a while. When he takes them off while coming off stage the blue shirt he has on underneath has fresh raindrops on it like he had only put the cap and gown on a few minutes before the shot.
Continuity mistake: The raindrops on Clark's shirt disappear and reappear between shots. Clark's shirt is dry when he turns to Chloe and asks "I'm not normal?" but before and after this his shirt has raindrops on it. This happens again a few moments later as Lois starts to talk about "panicking in times of crisis", Clark turns towards Lois and his shirt is dry.
Continuity mistake: Jason Teague arrives at the Kent farm. He fires a shot into the windshield of the Kent's truck. So we obviously know the gun is loaded. Later, inside the Kent's house, Jason still has Jonathan and Martha held hostage. After Jason mentions the symbols burned into the field Martha says she doesn't know what he is talking about. Jason gets upset and racks the shotgun but when he does no shotgun shell, used or unused, is ejected. Now Jason would have had to keep the gun loaded while moving Jonathan and Martha back to the house as he would have had no time to unload and reload his gun.
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