by Jeni Bone
A recent UN Environment Program, report, known as 'Yearbook for 2011', described marine plastics as the world's new toxic time-bomb. According to UN scientists, in addition to entangling wildlife, or being mistaken for food, floating plastics accumulate and concentrate chemicals such as polychlorinated biphenols (PCBs) and the pesticide DDT, which make their way in to the food chain and affect all living creatures, marine and man.
If plastic doesn’t biodegrade, what does it do? It 'photo-degrades' – a process in which it is broken down by sunlight into smaller and smaller pieces, all of which are still plastic polymers, eventually becoming individual molecules of plastic, still too tough for anything to digest. For the last fifty-odd years, every piece of plastic that has made it from our shores to the Pacific Ocean, has been breaking down and accumulating in the central Pacific gyre. Oceanographers like Curtis Ebbesmeyer, the world’s leading flotsam expert, refer to it as the great Pacific Garbage Patch. The problem is that it is not a patch, it’s the size of a continent, and it’s filling up with floating plastic waste.
According to the UN report, around 80% of marine debris is from land-based sources and the remaining 20% is from ocean based sources.The sources can be categorised into four major groups:
• Tourism related litter at the coast: this includes litter left by beach goers such as food and beverage packaging, cigarettes and plastic beach toys.
• Sewage-related debris: this includes water from storm drains and combined sewer overflows which discharge waste water directly into the sea or rivers during heavy rainfall. These waste waters carry with them garbage such as street litter, condoms and syringes.
• Fishing related debris: this includes fishing lines and nets, fishing pots and strapping bands from bait boxes that are lost accidentally by commercial fishing boats or are deliberately dumped into the ocean
• Wastes from ships and boats: this includes garbage which is accidentally or deliberately dumped overboard. Huge volumes of non-organic wastes, including plastics and synthetics, are produced in more developed, industrialised countries. Conversely, in less developed and more rural economies, generally a much smaller amount of these non-biodegradable persistent wastes are produced. However, in the future, as less developed countries become more industrialised, it is likely that they will also produce more plastic and synthetic wastes and this will increase further the threat of pollution of the marine environment.
Says Captain Charles Moore who ventures frequently into that part of the Pacific aboard Oceanographic Research Vessel, Alguita (Alguita.com, Algalita.org) 'It’s not just entanglement and indigestion that are problems caused by plastic debris. There is a darker side to pollution of the ocean by ubiquitous plastic fragments.
'As these fragments float around, they accumulate the poisons we manufacture for various purposes that are not water-soluble. It turns out that plastic polymers are sponges for DDT, PCBs and nonylphenols -oily toxics that don’t dissolve in seawater. Plastic pellets have been found to accumulate up to one million times the level of these poisons that are floating in the water itself. These are not like heavy metal poisons which affect the animal that ingests them directly. Rather, they are what might be called 'second generation' toxic waste.
Animals have evolved receptors for elaborate organic molecules called hormones, which regulate brain activity and reproduction. Hormone receptors cannot distinguish these toxics from the natural estrogenic hormone, estradiol, and when the pollutants dock at these receptors instead of the natural hormone, they have been shown to have a number of negative effects in everything from birds and fish to humans.
'The whole issue of hormone disruption is becoming one of, if not the biggest environmental issue of the 21st Century. Hormone disruption has been implicated in lower sperm counts and higher ratios of females to males in both humans and animals. Unchecked, this trend is a dead end for any species.'
So why not just clean it all up? Captain Moore says it would be easier to vacuum every square inch of the entire United States.
'The plastic patch is larger and the fragments are mixed below the surface down to at least 30 metres. Also, untold numbers of organisms would be destroyed in the process. Besides, there is no economic resource that would be directly benefited by this process.
'We have not yet learned how to factor the health of the environment into our economic paradigm. We need to get to work on this calculus quickly, for a stock market crash will pale by comparison to an ecological crash on an oceanic scale.'
More at http://www.unep.org/regionalseas/marinelitter/publications/docs/plastic_ocean_report.pdf