Life Cycle of a Plastic Bottle Part 4: Decomposition/Breakdown Process

published on

January 25, 2016

One of the key reasons that plastic is such a popular material used to manufacture gazillions of products, utilized in every sector and industry, is its durability. However, because plastic is so long-lasting, it takes a very long time to break down in the environment, and consequently it persists for a very long time -- as long as 600 years in the ocean!1


Plastic is photodegradable — it breaks down into pieces that become smaller and smaller when it is exposed to UV radiation from the sun. This break-down process is very slow, and instead of dissolving the plastic, it breaks it down into plastic fragments that become smaller and smaller over time, eventually becoming tiny bits of plastic suspended in freshwater aquatic systems, estuaries and the ocean, that can end up washed ashore where they are often found littering once pristine beaches. These tiny bits of plastic — called microplastic — are extremely detrimental to wildlife of all forms, and take a heavy toll with marine life.


Because oceanic temperatures are typically much lower than temperatures plastics are exposed to on land, they tend to break down much more slowly in the ocean than they do when exposed to sunlight on land. But what compounds this problem further is that while plastic floating around the ocean is gradually breaking down into smaller and smaller fragments, plastic is continually being added from multiple sources all over the world. Because the rate that it is being added is far greater than the rate at which it is breaking down, the amount of plastic in the ocean is growing exponentially.


An estimated 90% of all marine debris consists of plastic and styrofoam, with food and beverage packaging being the most abundant items found during beach cleanups and coastal surveys. During the 2015 International Coastal Cleanup 988,965 plastic beverage bottles were collected off coastal beaches around the world, together with 811,871 plastic bottle tops and 519,911 plastic straws. In addition 396,121 glass beverage bottles and 382,608 beverage cans were also collected.2 That is just the amount collected (many, many items, for example on remote beaches, would not have been collected), in a single coastal cleanup initiative over a limited time-frame.

Effect of Plastics on Wildlife

Scientists have now recognized that microplastics pose a real threat to both environmental and human health. Recent scientific surveys have shown that microplastics are abundant in all our oceans,3,4 and are impacting marine life, including top predators such as seabirds, marine mammals, and even humans who depend on seafood as a primary source of protein.4 Plastics are also taking their toll on organisms living in freshwater systems and subalpine lakes.5


Because plastic is light, it tends to float around on the surface of the ocean or suspended in the water column as it is breaking down into smaller pieces of plastic. These suspended and floating plastic bits are often mistaken for prey by marine animals such as fish and turtles, as well as seabirds, who unwittingly feed these plastic pellets to their hungry chicks. This causes high mortality of chicks at seabird colonies, and on a large scale can be detrimental to seabird populations, particularly vulnerable species such as albatross that are already threatened by other factors (e.g. harmful long-lining fishing practices).1


Because microplastic pellets are not readily digested, they tend to accumulate within the gut of marine organism that consume them. This can cause the animal to feel full, and as a result, it will stop feeding. It will slowly become emaciated and weak, and will ultimately die from starvation if it is not preyed on first. Plastics within the gut can also block the digestive tract, which will also result in the death of the animal. But the problem doesn't end there… If a predator consumes a fish whose stomach is full of plastic, this gets passed up the food-chain to the predator who will usually also struggle to digest it.


Additionally, plastics are manufactured from petroleum and other harmful chemicals, which can be released in the digestive tract as gastric acids try in vain to digest the plastic. These toxins are then absorbed into the organisms tissues. They can also leach out into the surrounding water as plastics float around in the water column, and contaminate filter feeders such as mussels. But that is only part of the problem; plastics also absorb harmful persistent organic pollutants (POPs), including DDT and  polychorinated Biphenyls (PCBs) that are known endocrine disrupters. These harmful toxins accumulate within the bodies of animals that ingest them, and also get passed up the food-chain to predators that consume them. These toxins can impair the animal's ability to breed successfully and can weaken their immune system, making them more susceptible to diseases. Because they are stored in body tissue, they become more concentrated in animals further up the food-chain, with long-living apex predators such as polar bears and whales being most affected.1

Health Effects on Humans

Like whales and polar bears, humans are top predators that consume a variety of shellfish, fish and other products that come from our oceans. We are exposed to the same toxins as other top predators in the ocean, and therefore the same health risks. When fish are gutted by the fishmonger, any sign of plastic lingering in the gut is removed. However, the toxins from those plastics are still contained in the tissue. So that freshly caught fish fillet lightly grilled in lemon and garlic butter may not be nearly as healthy as you think.

Eco-friendly Solutions

The only way to reduce the amount of plastic entering our ocean is to reduce the amount of plastics we use in our day-to-day activities. Considering that food and beverage containers makes up such a high percentage of plastic debris, it just makes sense to start looking for environmentally-friendly alternatives to throw-away plastic bottles (plus plastic bottle tops and straws). Opting for refillable beverage containers is not only a cost effective solution, it is also an environmentally sound solution.





  1. Ecology Matters. Marine Debris: The Environmental Effects of Plastic and Polystyrene Packaging.
  2. International Coastal Cleanup. 2015 Trash Free Seas Report: By the Numbers. A collection of infographics from our 2015 report.
  3. Moore, C.J., Moore, S.L., Leecaster, M.K., and Weisberg, S.B., 2001. A Comparison of Plastic and Plankton in the North Pacific Central Gyre. Marine Pollution Bulletin 42, 1297-1300. DOI:1016/S0025-326X(01)00114-X
  4. Plastic Debris in the World's Oceans
  5. Hannes K. Imhof, Natalia P. Ivleva, Johannes Schmid, Reinhard Niessner and Christian Laforsch. Contamination of beach sediments of a subalpine lake with microplastic particles. Current Biology, 2013 DOI:1016/j.cub.2013.09.001
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