Biology #2

PCBs and the Orcas

From the 1930s to the 1970s PCBs or polychlorinated biphenyls were used in industrial products. In 1977 they were banned in North America as concerns about what the PCBs were doing to the environment were growing. But synthetic chemicals, such as PCBs, bioaccumulate, biomagnify, and have a long half-life. PCBs stay in organisms, suppress the immune system, and may cause cancer in humans. But aquatic ecosystems have taken a hard hit with the PCBs

The animal that was hit the hardest was the orcas. A study found that PCBs will interfere with the orcas reproductive system until at least 2030. Though the chemicals have been banned for decades, the orcas retain high levels of PCBs, especially the calves. The figure shows how biomagnification occurs in orcas. PCBs enter the food chain at a low level in the microscopic plants and algae, but by the time the PCBs reach the orca, they are highly concentrated in the blubber. When the salmon population gets low, magnification is increased, since blubber is burned for energy. The PCBs are then released into the bloodstream where they interfere with the immune function, making the orca more susceptible to disease.

Not only does this show my knowledge of half-lives, which relates back to the chemistry unit, it also shows how pollutants climb up the food chain, as well as bioaccumulation and biomagnification.