Contamination Status and Toxicological Implications of Persistent Toxic Substances in Avian Species

The present study reviewed the contamination status and accumulation features of persistent toxic substances (PTSs), such as polychlorinated dibenzo- p -dioxins (PCDDs), dibenzofurans (PCDFs), biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs), in avian species from Japan and open sea areas. PTSs were detected not only in Japanese coastal and inland birds but also in open sea birds, suggesting global-scale pollution by these contaminants. Higher concentrations of PBDEs were observed in Japanese raptor and omnivore species, while PCB levels in piscivorous birds were notably higher than in other species. Interestingly, relatively high concentrations of dioxins and related compounds (DRCs) such as PCDDs, PCDFs, and dioxin-like PCBs (DL-PCBs) were found in open sea birds, such as albatross species. Toxic equivalents (TEQs) of PCDDs, PCDFs, and DL-PCBs, which were calculated using toxic equivalency factors (TEFs) for birds proposed by the World Health Organization (WHO), were greater in albatross eggs than some avian toxicity thresholds, implying possible biochemical alterations by DRCs in albatross embryos. These results indicate that many avian species inhabiting Japan and the open ocean have been exposed to region-specific PTSs that may have put them at risk.