The deep ocean is not a safe place, as shown by new research finding evidence of high levels of persistent organic pollutants (POPs) in marine animals in the Mariana and Kermadec Trenches, two of the deepest marine trenches in the world.
Based on recent analyses, tiny crustaceans thriving in the trenches’ dark waters are laced with toxic chemicals already banned decades ago: polychlorinated biphenyls (PCBs) and polybrominated diphenyl (PBDEs). These highly toxic industrial chemicals, banned in the late 1970s, do not break down in the environment and were previously discovered at high amounts in marine creatures in Western Europe as well as the Inuit people in Canadian Arctic.
Get to know the sources and adverse effects of these two pollutants.
PCBs: From Electronics To The Environment
Belonging to a broad family of man-made organic chemicals called chlorinated hydrocarbons, PCBs were manufactured in the United States from 1929 until their ban in 1979 out of health and environmental concerns. They may be found in transformers and capacitors, electrical equipment like voltage regulators, oil in motors and hydraulic systems, cable insulation, adhesives and tapes, and plastics, to name a few.
Since PCBs do not easily break down in the environment, they can stay for long periods of time cycling among air, water, and soil, the U.S. Environmental Protection Agency (EPA) noted. They can be brought long distances and even detected in snow and sea waters far from where they were released.
These chemicals can accumulate in leaves and elevated parts of food crops and plants, as well as ingested by small organisms and fish. PCBs bioaccumulating in fish may also be harming people consuming the food.
In the new research, crustaceans in the Mariana Trench were seen contaminated with PCBs 50 times the amount in crabs located in one of the most polluted rivers in China. They were also found in higher concentrations in the Mariana Trench than in Kermadec, potentially due to the proximity of the former to the Great Pacific Garbage Patch.
PBDEs: Flame Retardant Chemicals
PBDEs, on the other hand, are flame-retardant chemicals added to plastics and foam products to make them difficult to burn. Since they are mixed into plastics and foams instead of being bound to them, these chemicals can leave the products containing them and enter the environment.
According to the U.S. Centers for Disease Control and Prevention (CDC), PBDEs enter water, air, and soil while being manufactured and used in consumer products. While they can be degraded by sunlight, they do not easily dissolve in water, and they stick to particles and thus settle to the bottom of lakes or rivers.
In studies, rats and mice ingested food with moderate amounts of this chemical for a few days exhibited thyroid gland effects. Evidence suggests that high concentrations of PBDEs — already in blood, breast milk, and umbilical cord blood — may lead to neurobehavioral changes and immunity problems in animal models.
“PBDEs are chemical similarity to dioxins and PCBs, although far less studied from a toxicological perspective,” stated OurStolenFuture.org, a website dedicated to research on endocrine disruption. “What is clear is that they are potent thyroid disruptors, 7x more powerful than human thyroxine at binding with human transthyretin.”
Several U.S. states have passed legislation to ban certain PBDEs, but the government is still being pushed to enforce a national ban on the chemicals while companies are urged to replace them with safer alternatives and disclose flame retardant information on their products.