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Predicting global killer whale population collapse from PCB pollution

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Science  28 Sep 2018:
Vol. 361, Issue 6409, pp. 1373-1376
DOI: 10.1126/science.aat1953

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  • Orcas and PCBs
    • Giovanni Di Guardo, Associate Professor, University of Teramo, Faculty of Veterinary Medicine, Teramo, Italy
    • Other Contributors:
      • Antonio Fernández, Full Professor, Universidad de Las Palmas, Instituto Universitario de Sanidad Animal y Seguridad Alimentaria, Las Palmas, Gran Canaria, Spain

    The dramatic population decline which has been predicted to affect killer whales (Orcinus orca) on a global scale by the end of this century is of concern, with the levels of polychlorinated biphenyls (PCBs) in tissues from free-ranging orcas having been estimated to be among the highest in the animal kingdom (1).
    As in other cetacean and non-cetacean “top predators”, in fact, lipophilic PCBs may heavily accumulate in killer whales’ subcutaneous blubber, thereafter undergoing ad hoc “biomagnification” processes. Since these bioaccumulation and biomagnification dynamics are shared by many other persistent environmental pollutants - either “classical” (i.e. DDTs, dioxins, heavy metals, etc.) or “emerging” (i.e. PBDEs, PFAS, micro- and nanoplastics, etc.) -, that almost unvariably form “mixtures” to which aquatic organisms are chronically exposed via the marine food web(s) (2), one could wonder how the biological effects of PCBs may be effectively “dissected” from those of the other contaminants present in the aforementioned mixtures. Furthermore, the “endocrine disrupting” and the additional pathogenic activities of PCBs on host’s reproductive and immune functions are also known to be exerted by other organochlorine (OC) pollutants, the entry of which into exposed animals’ cells is mediated by aryl hydrocarbon receptors (AHRs) (3). This implies that the susceptibility of a given species to PCBs and, more in general, to OC contaminants could “ideally” result from the “s...

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    Competing Interests: None declared.