An overview of the toxic effects of polychlorinated biphenyls and dioxins in marine mammals and their risk assessment.

Supervisors: Hisato Iwata (Center for Marine Environmental Studies –CMES-, Ehime University, Japan).
Persistent organic pollutants (POPs) are highly lipophilic toxic compounds that are known tobioaccumulate and biomagnify within marine food webs. Marine mammals are particularly susceptibleto the accumulation of POPs due to their high trophic level, and thus act as sentinels for ecological riskassessments. This review will focus on the legacy pollutants polychlorinated biphenyls (PCBs) anddioxins, and aims to provide an overview of their toxic effects in marine mammals, as well as a riskassessment of wild populations. There was a wealth of information for this review as PCB and dioxininducedtoxicity has been of interest for over half a century. Using the search engines PubMed andGoogle Scholar, sources were selected according to their relevance to the research topic, year ofpublication, and their impact on the field. Despite a decline in the concentration of POPs in marinemammals over the past few decades, many populations are still exposed to toxicologically significantlevels, resulting in many adverse effects including Immunotoxicity, endocrine disruption, reproductivefailure, neurotoxicity, and cancer. Marine mammals at the highest trophic levels such as bottlenosedolphins (Tursiops truncates) and killer whales (Orcinus orca) often have the highest levels of POPaccumulation, and should thus be carefully monitored. Currently, there is a dearth in controlledtoxicological studies on marine mammals due to ethical and practical complications. However, recentadvances in marine mammal cell culture techniques provide an exciting avenue for toxicologicalresearch to explore in order to identify and fill in the large knowledge gaps in terms of species-specificresponses to POP exposure.