A new study has concluded that polychlorinated biphenyls (PCBs), a group of man-made organic chemicals, are playing a role in declining killer whale populations around the world.
PCBs were originally discovered in coal tar in the 1800s and were ultimately used in a wide range of ways from hydraulic fluids in heavy machinery to dyes and pigments in carbonless copy paper. Though banned in 1979, the list of products that may contain PCBs that the EPA provides is staggering. It's no wonder that they've seeped into the environment to devastating effects.
Scientists linked PCBs to cancer and immune system, reproductive, and endocrine related health problems in both people and animals, which led the United States to ban them in 1979. Globally they weren't banned until 2004. From there, PCB levels dropped. But these chemicals don't break down easily and considering that they're found in a wide range of products from electrical transistors to floor finishing, it's no surprise that PCBs flood landfills to this day. That means they leak into the environment.
From there, microbes feed on the toxic substances. PCBs then make their way up the food chain, along the way being stored in the blubber of animals, especially at the top of the chain in apex predators like killer whales. Over the past several years surveys have revealed that killer whale populations are dropping, while others have documented high PCB levels in the creatures. So, a team of scientists has put together a series of tests and models to find out more about the correlation.
The tests concluded that more than half of the 19 killer whale populations studies will decline because of PCBs' effects. In the next 50 years, the PCBs will impair reproduction enough that these specific groups could disappear entirely.
Other apex predators, such as sharks and seals likely have high PCB levels. It's also likely that other long lived chemicals which are showing up in wildlife will prove to be extremely deadly.
Read more: http://www.sciencemag.org/news/2018/09/long-banned-toxin-may-wipe-out-many-killer-whales