Bioavailability of soil-borne polybrominated biphenyls ingested by farm animals.

Concentrations of polybrominated biphenyl (PBB) were measured in the fat of livestock on several farms on which soil-borne PBB in confinement areas was the only source of residue. Ratios of concentrations in fat to concentrations in soil were 0.37 for dairy heifers, 0.27 for primaparous dairy cows, 0.10 for multiparous dairy cows, 0.27 for beef cows, 0.39 for beef calves, 0.37 for ewes, and 1.86 for swine. Multiparous dairy cows had lower ratios because of the excretion of PBB in milk during long-term lactation, and swine had higher ratios because they ingest greater amounts of soil than other species. Diets containing 5% PBB-contaminated soil, or 5% contaminated soil amended with activated carbon, were fed to lambs for 56 d. Accumulation of soil-borne PBB in fat, when adjusted for intake, did not differ significantly from accumulation of PBB from a diet in which PBB was added to cornmeal. Amending soil with activated carbon had no effect on residue accumulation. About 70% of PBB in a control diet with PBB added to cornmeal was absorbed, as measured by using titanium as an unabsorbed marker. Absorption of soil-borne PBB was 65% from unamended soil, 57% from soil amended with 0.3% activated carbon, and 56% from soil amended with 0.6% activated carbon. The differences were not great enough to be of practical importance. These results with PBB may be useful in assessing and managing risks of other soil-borne contaminants that have chemical characteristics similar to those of PBB.