Plastic pollution, its degradation and why we should care

Introduction:

Nowadays it is fairly common knowledge that plastics take a long time to degrade after they are discarded.  However, the actual mechanisms of this degradation are poorly understood by most of us.  Also, the time that this degradation takes is also not common knowledge.  Most importantly, few people seem to have a good understanding of why we should care about this at all.

Background on plastic degradation and biodegradation:

What’s the difference between degradation and biodegradation?  Simple: degradation is any process that wears a material down and biodegradation is the breakdown a material by biotic processes (example: digestion).  Non-biotic degradation can occur in nature mechanically (example: wave action; Figure 1) or chemically (examples: limestone dissolution, photodegradation of plastics).

A black bottle on a beach
Figure 1: A plastic bottle that has been partially degraded by wave action. Credit: RaceforWater. License: CC 4.0.

Some seemingly well-meaning companies claim that plastic “never biodegrades” (example: Brush with Bamboo).  Plastic certainly degrades, so this claim is verging into the realm of bullshit.  However, these companies are not necessarily peddling bullshit, which highlights the fact that this type of hyperbolic claim is beneath them.  Also, many academic studies document and examine the biodegradation of some types of plastics (e.g. Leja and Lewandowicz, 2010; Russell et al., 2011; Ghosh et al., 2013).  This renders claims of plastic immutability even more absurd.

Of course, plastics (like everything else) do degrade over time.  Here are a few examples of degradation times, according to the US National Parks Service:

  • Glass bottle = 1,000,000 years
  • Plastic bottle = 450 years
  • Aluminum can = 80-100 years
  • Paper towel = 2-4 weeks

Some ways plastic impacts the environment:

Plastic waste tends to choke, strangle or entangle wildlife.  (If you are unaware of this phenomenon, let me just say how honored I am that my website is the first non-porn thing you have seen on the interwebs.)  This is most common in marine settings (Derraik, 2002; Figure 2).

A beach that is covered in plastic pollution
Figure 2: A beach that is covered in plastic pollution. License: CC0.

When plastic is degraded into smaller pieces, monomers or chemicals, it can become concentrated in the groundwater supply (Teuten et al., 2009).  These micro-plastics can also be concentrated within the food chain (Hollman et al., 2013).

The chemical degradation of some plastics releases large amounts of methane gas (Levis and Barlaz, 2011).  This is a powerful greenhouse gas that contributes to climate change.

Why should I care if I’m not a turtle or otherwise hungry for plastic?

First of all, you should care what happens to the other animals that scurry around on this planet with you.  Also, it is in your own best interest to live within a robust and diverse ecosystem.  (Yes, humans are still part of the ecosystem.)

But sad polar bears and tangled-up sea gulls aren’t the only reasons for concern over plastic pollution.  Us humans don’t often get caught in six pack rings or mistake plastic bags for delicious jellyfish.  However, we do need clean groundwater and BPA leachates (stuff that leaks from a landfill) cause decidedly dirty conditions.  These conditions include detrimental effects on vertebrate embryos and hormonal levels (Canesi and Fabbri, 2015).  Furthermore, plastic degradation has been found to be one of the worst sources of these contaminants (Teuten et al., 2009).

Thirdly, climate change through increased greenhouse effects is greatly exacerbated by plastic degradation.  This climate warming is not good for humans (McMichael, 2013).  This detriment is almost certainly real—despite the opinions of some of the politicians we keep electing (feel free to peruse the mouth turds in the Scienceosaurus quote archive).  However, even if you discount the overwhelming scientific consensus on this subject, taking steps toward climate change mitigation makes good sense from economic and public health standpoints as well (Shindell et al., 2012).

References:

Canesi, L., & Fabbri, E. (2015). Environmental Effects of BPA: Focus on Aquatic Species. Dose-Response, 13(3), 1559325815598304. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4674185/

Derraik, J. G. (2002). The pollution of the marine environment by plastic debris: a review. Marine pollution bulletin, 44(9), 842-852. http://www.sciencedirect.com/science/article/pii/S0025326X02002205

Ghosh, S. K., Pal, S., & Ray, S. (2013). Study of microbes having potentiality for biodegradation of plastics. Environmental Science and Pollution Research, 20(7), 4339-4355. http://link.springer.com/article/10.1007/s11356-013-1706-x

Hollman, P. C., Bouwmeester, H., & Peters, R. J. B. (2013). Microplastics in aquatic food chain: sources, measurement, occurrence and potential health risks (No. 2013.003). Rikilt-Institute of Food Safety. http://library.wur.nl/WebQuery/wurpubs/440009

Leja, K., & Lewandowicz, G. (2010). Polymer biodegradation and biodegradable polymers—a review. Polish Journal of Environmental Studies, 19(2), 255-266. https://www.researchgate.net/profile/Katarzyna_Leja/publication/230793131_Polymers_Biodegradation_and_Biodegradable_Polymers__a_Review/links/0fcfd504731fddbdb6000000.pdf

Levis, J. W., & Barlaz, M. A. (2011). Is biodegradability a desirable attribute for discarded solid waste? Perspectives from a national landfill greenhouse gas inventory model. Environmental science & technology, 45(13), 5470-5476. http://pubs.acs.org/doi/abs/10.1021/es200721s

McMichael, A. J. (2013). Globalization, climate change, and human health. New England Journal of Medicine, 368(14), 1335-1343. http://www.nejm.org/doi/full/10.1056/NEJMra1109341#t=article

Russell, J.R., Huang, J., Anand, P., Kucera, K., Sandoval, A.G., Dantzler, K.W., Hickman, D., Jee, J., Kimovec, F.M., Koppstein, D. & Marks, D.H. (2011). Biodegradation of polyester polyurethane by endophytic fungi. Applied and environmental microbiology, 77(17),.6076-6084. http://aem.asm.org/content/77/17/6076.short

Shindell, D., Kuylenstierna, J.C., Vignati, E., van Dingenen, R., Amann, M., Klimont, Z., Anenberg, S.C., Muller, N., Janssens-Maenhout, G., Raes, F. and Schwartz, J. (2012). Simultaneously mitigating near-term climate change and improving human health and food security. Science, 335(6065), pp.183-189. http://science.sciencemag.org/content/335/6065/183

Teuten, E. L., Saquing, J. M., Knappe, D. R., Barlaz, M. A., Jonsson, S., Björn, A., Rowland, S. J., Thompson, R. C., Galloway, T. S., Yamashita, R. and Ochi, D. (2009). Transport and release of chemicals from plastics to the environment and to wildlife. Philosophical Transactions of the Royal Society B: Biological Sciences, 364(1526), 2027-2045. http://rstb.royalsocietypublishing.org/content/364/1526/2027.short

Jared Peters

Jared Peters

Jared Peters, PhD, is a geoscientist who specialises in marine sedimentology, marine palaeoglaciology and climate change.
Jared Peters
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Jared Peters, PhD, is a geoscientist who specialises in marine sedimentology, marine palaeoglaciology and climate change.