New study shows that the current concentrations of PCBs in the oceans are threatening the world’s population of killer whales

( Natural News ) Killer whales, or orcas, are one of the most widespread mammals on our planet, living in oceans from pole to pole. Part of the dolphin family, they are extremely social and smart creatures. Sadly, these enormous predators may one day be wiped off the face of the earth, however, thanks to pollution from polychlorinated biphenyls (PCBs). According to a new study that was published in Science , half of the world’s killer whales could disappear within the next 30 to 50 years as a result the concentrations of PCBs seen in oceans. The international team of researchers say that 10 out of the 19 populations they studied showed a rapid decline in numbers , and they’ve warned that the species could disappear completely from some areas in the next few decades. The problem is that the orcas tend to feed on large fish like sharks and tuna, as well as seals, that accumulate pollutants like PCBs from successive levels of the food chain. As the last link in a very long food chain, killer whales are the mammals that have the highest PCB levels in their tissues. In fact, researchers have found concentrations as high as 1300 mg per kilo within the blubber of killer whales. That is far greater than the 50 mg per kilo threshold at which infertility and serious immune system impacts can be seen. There are some places, however, where they feed mostly on smaller fish like mackerel and herring, and their lower PCB content places the orcas in these areas at a lower risk of disappearing . Why are PCBs so dangerous? After being introduced in the 1930s, more than a million tons of PCBs were created for making goods like plastics and electrical components. They’ve been spreading in oceans […]

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