PCB congener patterns in rats consuming diets containing Great Lakes salmon: Analysis of fish, diets, and adipose tissue

As part of a multidisciplinary toxicological investigation into Great Lakes contaminants, chinook salmon were collected from Lake Huron (LH) and Lake Ontario (LO) and incorporated las lyophilized fillets) into standard rat di ets as 20 or 100% of the protein complement (5 or 20%, w/w diet-LH5, LH20, LO5, and LO20 diets). Final PCB concentrations in the experiment ranged fro m 3.15 ng/g in the control diet to 1080 ng/g in the high-dose (20%) LO diet , with maximal estimated daily consumption by the rats of 82 mu g PCBs/kg b ody wt in the LO20 dietary group. Seventeen PCB congeners, PCB 85, 99, 101, 105,110,118,128,129,132,138,149,153, 180, 187, and 199, occurred at greater than or equal to 3.0% of the total PCBs in the fish with no major site dif ferences. Cumulatively, these 17 congeners accounted for up to 75% of the t otal PCBs in the fish compared to 44 and 54% in two commercial Aroclors, 12 54 and 1260, respectively. PCB 77 was the major "dioxin-like" congener in t he fish, followed by PCB 126 and then PCB 169. All major dietary congeners bioaccumulated in the adipose tissue of the rats with the exception of PCB congeners 101, 110, 132, and 149. The group of 17 major congeners accounted for up to 71% of the total PCBs in adipose tissue samples collected from t he rats following up to 19 weeks of diet ingestion. Of the coplanar PCB con geners, PCB 77 appeared to bioaccumulate to a lesser extent compared to PCB s 126 and 169, When comparing PCBs in the rat adipose tissue to PCB congene rs in Canadian breast milk, PCBs 44, 49, 74, and 137 tended to occur in hig her amounts in the human samples (contributing together 18.4 vs. 1.4% of th e total PCB concentration), whereas PCB 129 occurred at higher levels in th e rats (3.4 vs. 0.3% of the total PCB concentration, respectively). Althoug h adipose tissue from the rats fed diets containing Great Lakes salmon had up to two orders of magnitude higher concentrations of PCBs compared to ave rage human values, with the exception of some lower chlorinated congeners, similar major congeners tended to be present in both the rats in the presen t study and humans.