What is the source in the Mishna for the halakha that one is not liable for the laws of notar and impurity when eating blood?

Rabbi Shimon and the rabbis disagree about whether one is liable for eating items that are not fit for consumption while in a state of impurity. Is their dispute limited to items that themselves became impure, or does it also apply to a person who is impure and eats sacrificial items that are pure?

Sacrificial offerings are slaughtered with six intentions: for a specific sacrifice, for a specific person, for God, for consumption by fire, to produce a pleasing aroma, and to be accepted by God. In addition, sin and guilt offerings must be slaughtered with intent for the specific sin they atone for.

Rabbi Yosi stated that even if the slaughterer did not explicitly have all these intentions in mind, the offering remains valid. This is due to a stipulation enacted by the court that the slaughterer should not articulate all these intentions, in order to prevent errors that could invalidate the sacrifice, as the intention is performed by the one slaughtering/offering the sacrifice, not the owner of the sacrifice.