Decabromodiphenyl ether (BDE-209) enters the food web of the River Po and is metabolically debrominated in resident cyprinid fishes.

Decabromodiphenyl ether (BDE-209), the primary constituent of a widely used flame retardant formulation, is present at relatively high levels in sediments and macroinvertebrates of the River Po. Since it was demonstrated that BDE-209 can be biotransformed to smaller and more toxic polybrominated dipheyl ethers (PBDEs), the main objective of this study was to assess whether the large quantities of BDE-209 present in the River Po are bioavailable to the higher levels of the food web and are biotransformed in feral fishes. To this aim, 23 cyprinids, mainly common carp, were analysed for the hepatic contents of PBDEs. Contrary to sediments and invertebrates of the same area, no fish sample contained detectable levels of BDE-209. All fishes contained typical PBDE representatives, e.g. BDE-47, BDE-99, BDE-100, BDE-153 and BDE-154, but more importantly they contained three congeners, i.e. BDE-179, BDE-188 and BDE-202, which are not present in any technical formulations and are known products of BDE-209 debromination in fish. The age of carps had no effects on the bioaccumulation of PBDEs. Conversely, the contents of PCBs, which also were determined in the same fish samples, showed a positive correlation with age. Both groups of chemicals displayed a tendency to a higher contamination in male fish. This study shows that BDE-209 enters the food web of the River Po contributing to the load of lower brominated PBDEs and thus to the load of chemical stressors threatening the aquatic life of the major Italian watercourse.