Killer whales, as apex predators, are highly contaminated due to the accumulation of Persistent Organic Pollutants (POPs) from their prey. These toxins are difficult to eliminate and are stored in the thick blubber of cetaceans. Studies have found that killer whales are among the most contaminated marine mammals globally, with Bigg's (transient) killer whales, which feed on marine mammals, having the highest levels of PCBs. PCB concentrations and other pollutants increase with age in both resident and transient killer whales. The transfer of contaminants from female to calf occurs during gestation and nursing, with the first-born calf receiving the highest load. This transfer reduces the contaminant load in females, but it means that juveniles can have higher POP levels than their mothers. The foraging location also affects the contaminant load, with southern resident killer whales having higher toxin levels due to consuming Chinook salmon from near-urban waters with higher pollution. Even in the Arctic, seemingly untouched by human activities, top predators and baleen whales accumulate large amounts of contaminants. Limited prey availability exacerbates the issue, as fat stores containing POPs are mobilized during food shortage, leading to higher concentrations of toxins in the body. This situation affects the survival and reproductive success of cetaceans, such as southern resident killer whales.