Arctic orcas have so high concentration of contaminants in their blubber, that they are referred to as most toxic organisms of Arctic. How do you think the toxicants accumulated in its body?

Biomagnification refers to increase in concentration of the toxicant at successive trophic levels. PCBs break down slowly and are drawn to the molecules of living animals, and so became part of food chain and web. Arctic orcas are an apex predator—they sit at the top of the food web, may eat fish, seals, sea lions, sharks, or whales, and have no natural predators. So the carcinogens build up in their blubber. Arctic orcas have so high concentration of contaminants in their blubber that they are referred to as most toxic organisms of Arctic. Polychlorinated Biphenyls (PCBs) are organic compounds that were once used in capacitators, oil paints and coolants. They were banned for the toxicity. But Scientists discovered traces of these in many organisms for three reasons: their persistence and high lipid solubility, PCBs tend to bioaccumulate in fatty tissues. They also are semi-volatile and therefore can vaporize or absorb onto atmospheric particles. This permits the global transport of these chemicals in air and water.