Assessment of current dietary intake of organochlorine contaminants and polycyclic aromatic hydrocarbons in killer whales (Orcinus orca) through direct determination in a group of whales in captivity.

We determined the levels of 16 polycyclic aromatic hydrocarbons (PAHs), 19 organochlorine pesticides (OCPs) and 18 polychlorinated biphenyls (PCBs) in the plasma of captive adult killer whales and in their food. The goal of this research was the assessment of the dietary exposure of killer whales to these pollutants to gain insight on what is the actual magnitude of the exposure in this species, which is considered among the most contaminated in the planet. Plasma median ∑OCP and ∑PCB contents were 3150.3 and 7985.9 ng g(-1)l.w., respectively. A total of 78.9% of the PCBs were marker-PCBs, and 21.1% were dioxin-like PCBs (6688.7 pg g(-1)l.w. dioxin toxic equivalents). This is the first report of the blood levels of PAHs in killer whales, and their median value was 1023.1 ng g(-1)l.w. In parallel, we also determined the levels of these contaminants in the fish species that are used to feed these animals to estimate the orcas' average daily dietary intake of pollutants. All the contaminants in the fish were detected in the plasma of the killer whales, and proportionality between the intake and the blood levels was observed in all the animals. The calculated intake was extremely high for certain contaminants, which is a concern, giving a glimpse of what possibly occurs in the wild, where exposure to these contaminants can be even higher. Therefore, although many of these chemicals have been banned for decades, even today, the levels of these chemicals could reach very toxic concentrations in the tissues of these endangered animals because of their diet.