Science & Technology

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Organic pollutants: human habits haunt oceans

Organic pollutants: human habits haunt oceans

Tarik Haiga considers the implications of a recent study that has found persistent organic pollutants (POPs) in the world’s deepest ocean trenches.


It’s not news that air, land and water pollution have been one of the main side effects of human technological and industrial progress. We’ve seen it happen in the ozone layer, due to the discharge of chemicals such as CFCs. Now a study led by Dr. Alan Jamieson of Newcastle University has revealed that two kinds of persistent organic pollutants – PCBs, used as electrical insulators, and PBDEs, used as flame retardants – have been found, in high levels, in the Pacific Ocean’s Mariana and Kermadec trenches, which are over 10km deep and separated by 7000km.

It is estimated that 80% of marine pollution comes from land-based pollutants. This is caused by multiple factors: pollutants such as fertilizers or oil released by vehicles eventually make their way into water, in addition to polluted coastal air that stems from industrial activity in seaside regions. Oil spills are another damaging factor that can degrade or destroy entire marine ecosystems and elevate concentration of toxic elements: and sadly, these events only comprise 12% of the amount of oil discharged into the seas yearly.

Toxic chemicals have contaminated almost every marine organism, from giant whales to microscopic plankton. Dumping toxic chemicals in the marine environment, however, has been banned since the 1972 London Dumping Convention. Examining one kind of those planktons that are called amphipods, the study was carried out using deep-sea landers to collect samples from the trenches, some of the world’s most extreme environments. The researchers found PCBs and PBDEs in the organisms’ fatty tissue.

This shows that even after decades of the ban, toxic material has not bio-degenerated and in fact was moved to further places we thought previously unspoiled. As lead author Dr. Jamieson states: “We still think of the deep ocean as being this remote and pristine realm, safe from human impact, but our research shows that, sadly, this could not be further from the truth. In fact, the amphipods sampled contained levels of contamination similar to that found in Suruga Bay, one of the most polluted industrial zones of the northwest Pacific.” These findings may indicate that contamination has made its way to many other ecosystems that may have also been believed pristine, and throws into question the data available regarding global pollution rates.

The study suggests that deep-sea organisms may have become contaminated via the sinking of plastic debris, and the bodies of the marine life that consume them, down to the ocean floor, where they in turn are consumed by amphipods and other planktons. These smaller creatures are then themselves consumed by the larger organisms, a cycle of pollution which models the natural food chain. Katherine Dafforn, of the University of New South Wales, emphasises that the pollution of the deep ocean is clear evidence of the strong connection between surface and sea.

Insidious pollutants like POPs threaten a large number of living organisms, including human beings. The fact that tiny contaminated organisms can be consumed by larger ones in a pattern that extends right up to the top of the food chain means that we could potentially become contaminated through eating fish, seafood or animal fats. This is no small danger: contamination with POPs has been shown to cause numerous diseases including cancer, damage to the immune system and behavioural-neurological disorders.

It is our duty to understand how much our individual responsibility could help to overcome these challenges. This is manifested in the lifestyle we follow, the vehicles we drive, and how we deal with our waste.


Featured Image: Pixabay

Tarik Haiga

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