Are whales such as our beloved SeaWorld friend, Shamu, soon to be a distant memory? A recent study published by Science predicts a significant decline – possibly a complete population collapse – in killer whales, stemming from PCB pollution.
Polychlorinated Biphenyls (PCBs) are a group of organic hydrocarbons that contain chlorine atoms. The specific number and location of the chlorine atoms dictates the physical and chemical properties of the compound; however, they share general physical properties including: high viscosity, low flammability, high thermal conductivity and low water solubility. They are also non-reactive and stable, even in acidic, basic or high-temperature environments, which allows them to persist and accumulate in the environment (much like PFC compounds).
These compounds started being manufactured around 1929 for use in all kinds of industrial and manufacturing processes. In the 1970s, PCBs started being recognized as a carcinogen and by 1980, all PCB manufacturing was banned. Unfortunately, roughly 2 million tons of PCBs were produced in that 50 year timespan and estimates are that 10% of those PCBs still remain today. If those estimates are correct, roughly 200,000 tons of PCBs are in our environment, accumulating in our water and food sources.
While PCBs can accumulate in the soil, air and even the biosphere (which is the fancy word we use to represent all the ecosystems around the world); however, the largest concentrations of PCBs are found in our water sources. Once in the water, a process known as biomagnification takes place. Not to be confused with bioaccumulation, this process magnifies the concentration of a toxic element or compound as it moves up the food chain. So organisms and animals at the top of the food chain (killer whales, for example) are at risk for consuming lethal doses of contaminants. While overfishing and other anthropogenic activities are contributing to the decrease in the killer whale population, the presence of PCBs is likely causing the largest impact.
This article highlights the importance in protecting our water sources. Persistent contaminants can have adverse effects on people, animals and organisms across multiple generations. Protecting our water sources requires careful extractions of these toxic compounds for targeted testing and treatment. With careful water testing and worldwide efforts in water source protection, hopefully future generations of humans, whales and other “top of the food chain” organisms will enjoy risk-free existences!