Continuity mistake: One of the last scenes of the movie, when Karen Silkwood is driving away from Dru they show her sitting in the car waving at him and the rearview mirror is clearly visible. Then she starts driving away, and the rearview mirror is gone. Then as she drives off, you can see the mirror has been replaced.
Factual error: Karen points out to Thelma that she should have given a nasal swab (to detect internal contamination) after being 'cooked', yet on both occasions when Karen is being scrubbed after being contaminated she has blisters all over her face - something which should be avoided when performing decontamination as this can allow contamination to enter the body.
Deliberate mistake: When they arrive in Washington D.C., they are seen in a 1976 Dodge Dart taxicab, but the movie supposedly took place in 1974. There are several scenes where many cars used in the movie are post-1974.
Continuity mistake: When Karen's house is being stripped, she is outside talking to Mr. Hurley. Dolly tells Karen that she has to leave with this man and that everything is alright. We see Dolly get in the back seat of a car to leave. When Karen starts to suspect that someone spiked her sample kit, Dolly can be seen walking behind Mr. Hurley.