Thursday, September 26, 2013

How to Kill a Killer Whale

PCBs, polychlorinated biphenyls, are compounds used to by the U.S. Navy years ago to coat all electrical wires as a fire retardant. The coating saved thousands of sailors by preventing electrical fires when ships were struck during battle during World War II, the Korean War, and the Vietnam War. They were banned in the United States and Canada in the mid-1970s but are still widely used in the Third World. PCBs are insoluble in water, permeate soil, accumulate in animal fat and are very slow to degrade. (http: // chemical structure of a PCB, C12H10-nCln, where n=1 to 10, includes chlorineatoms on


Today, PCBs are still detected in water due to the environmental recycling of this compound. Orca whales, also known as killer whales, are one of the many animals PCBs directly affect. PCBs do not cause outright death of marine animals, but can weaken immune systems, hinder reproduction, lower sperm count, and disrupt calf development. Most of the PCB concentration in orcas is the result of PCB build up in their primary food source, Chinook salmon. Animals with weakened immune systems are especially vulnerable to diseases and unfortunately once PCBs are in the orcas, the toxins don’t go away. PCBs are considered a Persistent Organic Pollutant (POP) because once ingested, they persistently build up in the fatty tissue of the orcas and severely decreases the orca’s lifespan. This is threatening the existing members of an already endangered species.

Orcas do not reproduce in litters or even on a consistent basis. Females begin breeding when they are around 15 years of age and give birth about every three to four years. Around age 40, most females stop breeding and their PCB levels rise at a greater rate. As a result, a small amount of the PCBs are transferred as the offspring develops. Even more toxins are transferred through the mother’s milk and is extremely rich in fat. Without these environmental setbacks, females could produce four-to-six surviving offspring during their reproductive years. Instead, orca survival rates are greatly outnumbered by mortality rates. (http://science.kqed. org/quest/2013/07/19/the-killer-affecting-killer-whale-populations/)

As a society we can be a little gentler to the environment as far as disposing of waste and trash properly, buy environmentally-friendly household supplies and help others realize how dangerous this can be to our marine life as well as our human population. ( quest/2013/07/19/the-killer-affecting-killer-whale-populations/)


  1. I found this post extremely interesting as I have a strong interest in conservation, it goes to show that people need to be more aware of the substances that they are using and their broader effects because once a chemical is synthesized it may be very difficult to naturally degrade as is clearly the case with PCB.

  2. This is very interesting topic! It even directly relates to our real lives. As Tyler mentioned in her comment, I strongly agree her that people need to be aware of the what they use. And one more interesting is...I didn't even know there is a killer whale! :)