Toxicity and persistence of low-level PCB in adult wistar rats, fetuses, and young.

Aroclor 1254 was fed to female and male rats daily for 9 weeks at a dose of 6.4 mg/kg in their drinking water. Control animals received plain tap water plus the emulsified (0.15% Tween 80). Elevated mixed function oxidase (MFO) activity appeared to be due to 2,4,5,2',4',5'- and 2,4,5,2'3'4'-hexachlorobiphenyls, since only these compounds were present to any degree in the tissues of the animals when MFO activity persisted after termination of exposure. The placenta apparently is an effective barrier to PCB transfer.