Continuity mistake: After Lois pins the sketch of the Green Arrow, the pushpin changes position. In some shots, it's across the top of the paper and in others it's in between the top of the sketch and top of the paper.
Continuity mistake: Lana was found shot in her upper left shoulder but at the end of the show she has a sling on her right arm. (00:42:00 - 00:43:05)
Continuity mistake: When Chloe and Jimmy find Lana shot in the elevator, there is a gun on the floor beside her, with a small pool of blood beside in the gun. In the next closeup shot on the floor, the small pool of blood is gone. (00:42:00)
Continuity mistake: When Lana hands the gun to Jimmy, she hands it to him aimed away from her. When Jimmy takes it, it is aimed towards her. (00:59:00)
Continuity mistake: When Chloe shows the newspaper to Jimmy with his photo on it. The photo is not the same when it is shown in the close-up.
Continuity mistake: At the beginning of the episode, we see that the clock reads 2 o'clock. Jimmy then takes Chloe into the back room to his set-up movie date. A little into the scene, they then hear a gunshot. When they rush out, the clock now reads 4:15. However Chloe and Jimmy were not in the back room for this long. At 4:15 they find Lana shot, and call 911. Then after the credits, we return to the scene, but now the police have arrived. But now the clock reads 2:15. There is no way the police would have taken so long, that the clock would have jumped all the way around from 4:15 to 2:15, therefore the continuity on this clock is mixed up.
Continuity mistake: When Lionel is watching the video and drawing Kryptonian symbols, some of the symbols change in between shots. For example, when he draws "minion" one of the dots is touching the square. When he writes the word, everything is nice and neat and the dots aren't touching anything.
Continuity mistake: When Clark looks at Phillipe's police report, there is a photo of Phillipe facing sideways. In the next shot the photo has changed, so that now he is facing forward. (02:21:10)
Continuity mistake: When Lois attack the guard down in the dam, she hits his face, which causes the black cap that the guard is wearing to begin to fall off. Yet in the next shot the hat is firmly back on his head, before it is completely knocked off by Lois' next hit. (02:23:00)
Continuity mistake: When Chloe finds Lois stabbed in the dam, we see Lois on the floor with her arm hanging so that her hand is right beside the stab wound. However in the next close up of the wound, her hand isn't there. It's back beside it in the next shot. (02:28:20)
Continuity mistake: When the Phantom child kills the doctor and drags him over to the fingerprint scanner to open the door, we see the doctor has no glove on his hand when it is placed on the scanner. But when his arm drops to the floor, there is a glove on his hand now. (02:32:35)
Continuity mistake: Shortly after their cell phone conversation, Lionel sees Lana and gets out of his car. In the next shots of Lionel, his car has moved position from behind him.
Continuity mistake: When Lois is at the dam, looking at the card she previously tore, the numbers and markings are written differently than before.
Continuity mistake: When Kara and Clark get off the elevator, there's no-one around them as they're walking away. In the next shot of Kara and the elevator, 3 people have suddenly gathered to look at the broken elevator. The elevator was off camera for less than 2 seconds, not enough time for 3 different people to get into the position they're in when they weren't close by to begin with.
Continuity mistake: During the scene where Clark and Knox fight, Knox smashes his blue container with his weapon. Shortly after this, there is a shot where he is looking in horror at what he'd done and behind him, Chloe is struggling with her ankle cuffs. She appears to be wearing shoes in this frame, whereas before and after, she is barefoot.
Continuity mistake: Season 7, episode "Persona". When Lana walks in from the balcony her hair swaps from being in front of her shoulder to behind it, then back again. Then when she sees Bizzaro's face in the reflection of the glass, her hair is styled differently again.
Continuity mistake: When Lana comes in with her brown bag of groceries, she puts the vegetables and wine bottle on the counter. During the rest of the scene these items move their positions a few times.
Continuity mistake: When Phantom Clark finds Lana on the balcony with her phone pressed against her ear, she lowers the phone down to her waist twice between shots.
Continuity mistake: When Lex starts learning about Veritas he sees the symbol on his office window, but that was never there in all the 6 previous seasons.
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