By Pat Brown, Rising Fish & Fish for Garbage Intern
Anthropogenic litter is becoming an increasingly important issue. As growing economies continue to expand industrial production and consumption, waste will inevitably continue to be generated at a similar rate. A large amount of this waste ends up in the environment due to poor waste management practices, lack of awareness, and organizations not taking the health of wildlife and ecosystems into consideration. Once anthropogenic waste finds its way into natural ecosystems it can cause serious disruptions, create public health concerns, and throw off the delicate balance that allows ecosystems to properly function. According to the EPA, almost half of the rivers and streams and over a third of all lakes in the United States are so polluted that drinking from and recreating in the waters is unhealthy (EPA, 2009). If these waters are unfit for humans to use and consume, they are certainly also unfit as a habitat for aquatic species to thrive.
Image Source: Opelika Observer
Perhaps the most serious problems resulting from anthropogenic litter come from the negative ecological effects associated with plastics. Plastics are problematic because they are manufactured at incredibly high rates and the majority of them tend to be non-biodegradable, allowing them to persist in nature for hundreds of years, if not eternally in a smaller form (NPS, 2016). Over 300 million tons of plastic is manufactured every year, and the vast majority is non-biodegradable. (Horton et al, 2017; Zheng et al, 2005). To make matters worse, almost half of the plastics produced are manufactured for single-use purposes, such as plastic ware, plastic bags, beverage bottles or product packaging (Hoellein, 2017). This causes an abundance of plastic waste to collect in landfills, where it can cause ecological harm by leaching toxic substances into the soil and groundwater surrounding the area (EU, 2018). A significant amount is also lost to the environment where it tends to collect in the most vulnerable areas such as freshwater and marine ecosystems. It is estimated that 8 million tons of plastic waste find its way into the ocean every year (Rochman, 2018). 80% of these plastics come from land sources, indicating that terrestrial, riparian, and freshwater ecosystems are also quite vulnerable to the harmful effects associated with plastic pollution (Rochman, 2018).
Image Source: Our World in Data
One of the most significant environmental concerns regarding plastic pollution is its inability to readily biodegrade in landfills and natural environments. This is due to its unique molecular identity, which is also what makes it so versatile and durable. Plastics are manufactured in one of two different processes which create either thermoplastics or thermoset plastics. Almost all plastics employed for packaging and daily use are some type of thermoplastics, including polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyesters which account for products like plastic bags, food and product packaging, disposable cups, tires and bumpers, garden hoses and much more (Shah et al, 2008). Thermoplastics are created in a polymerization process that results in long polymer chains held together entirely by carbon-carbon bonds (Zheng, 2005). This unique molecular structure of thermoplastics creates viscoelastic properties that allow for a high degree of versatility and increased popularity for industrial and manufacturing purposes. The viscoelasticity of plastics allows them to be manipulated into different formations and levels of hardness through the appropriate combination of changes in temperature, strain, rate, and time. The molecular structure is also one of the main reasons plastic pollution is so harmful in the environment, as it makes these plastics extremely resistant to decomposition. The long carbon chains found in thermoplastics contain bonds that cannot be broken by organic substances, limiting the plastics’ capability to chemically react with or breakdown from the organic compounds found in nature. (Jansen, 2016; Zheng, 2005). While the molecular structure of these plastics makes them very stubborn in terms of biodegradation, however, it also gives them their viscoelastic properties, which makes them very easy to recycle.
The majority of plastic pollution existing in natural ecosystems is found as microplastics, which are any plastic particles less than 5mm in size. Microplastics can result from two different sources, considered primary and secondary microplastics. Primary microplastics come in the form of tiny plastic beads or pellets, which are used in the construction of consumer plastics. When plastics are manufactured, they are initially created as small beads or pellets, which are then distributed to the manufacturers of consumer products. Due to the viscoelastic properties of plastic, these pellets can then be molded into just about anything, while beads are most often used as an exfoliating agent in hygiene or cleaning products (Hoellein, 2017; Jansen, 2016). These tiny beads and pellets can persist in the environment for long after the material begins decomposing, which is why we have begun to find these in our oceans and washed up on marine and freshwater beaches (Hoellein, 2017; OceanCare, 2016).
Image Source: Challenges and Treatment of Microplastics in Water (Research Gate)
While leaching toxic chemicals and resisting degradation, microplastics present further ecological concerns because they are extremely difficult to remove from ecosystems, and they are often mistakenly ingested by wildlife such as fish and birds. Once ingested, microplastics have been shown to bioaccumulate, contaminating the food chain with toxins and causing intestinal damage in wildlife (Hoellein, 2017). It is estimated that over 5 trillion pieces of microplastic exist in the world’s oceans, weighing over 250,000 tons (Ocean Care, 2016). Because of their abundance and biological impacts, microplastics have become a major focus of scientific research relating to pollution.
Plastics are also known to consist of harmful chemical compounds that are capable of leaching into the environment. Plastic toxicity can come from the ingredients in the plastic itself, byproducts of the manufacturing process, or chemicals that are adsorbed in nature. Some of the most harmful chemicals known to be associated with plastic are polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), heavy metals and pesticides, all of which are recognized by the EPA as “priority pollutants” and strictly regulated due to their highly toxic properties (EU, 2016). Priority pollutants have been shown to be harmful to ecosystem processes and wildlife by bioaccumulating in food chains and causing reproductive concerns and disease in some species (EU, 2016). Additives such as flame-retardants, UV stabilizers, and plasticizers are also often used in the production of plastics and can have adverse environmental impacts. Some flame-retardants often used in plastic production have been proven to accumulate in the fat tissue of aquatic species causing neurological damage and contaminating the food chain, while plasticizers such as phthalates have been shown to cause reproductive issues in wildlife (EU, 2016). One of the most common ways these chemicals and additives from plastic make their way into species and ecosystems is through the process of leaching. Most stabilizers and additives are capable of being released from the plastic during the breakdown process and absorbed by the surrounding soil or water, whether in a landfill or in nature.
Image Source: Center for International Environmental Law (CIEL); Read the Plastic & Health: The Hidden Costs of Plastic Planet report here.
The challenge regarding global plastic pollution is that it could be easily avoidable by prioritizing better recycling practices within waste management systems. Non-biodegradable plastics account for 92% of all plastics manufactured for human use (Zheng, 2005). When these plastics are not properly disposed of, they persist in the environment leaching toxic chemicals, creating ecosystem disruptions, and impairing wildlife. If plastics are collected and properly disposed of, they can easily be heated, remolded, and repurposed as brand new products. If they are littered, there are serious and long-term ecological consequences felt by all living organisms.
REFERENCES
Environmental Protection Agency. National rivers and streams assessment 2008-2009 technical report, National rivers and streams assessment 2008-2009 technical report
European Union. (2016) TOXICITY OF PLASTICS. Retrieved from https://www.blastic.eu/knowledge-bank/impacts/toxicity-plastics/
National Park Service (2016). Things Stick Around. Retrieved from https://www.nps.gov/teachers/classrooms/things_stick_around.htm
Hoellein, T. (2017, June). Emerging Contaminants in the Aquatic Environment Conference. Loyola University, Chicago.
Horton, A. A., Walton, A., Spurgeon, D. J., Lahive, E., & Svendsen, C. (2017). Microplastics in freshwater and terrestrial environments: Evaluating the current understanding to identify the knowledge gaps and future research priorities. Science of The Total Environment, 586, 127–141. doi: 10.1016/j.scitotenv.2017.01.190
Jansen, J. A. (2016). Plastics - Its All About Molecular Structure. Plastics Engineering, 72(8), 44–49. doi: 10.1002/j.1941-9635.2016.tb01587.x
OceanCare (2016, July) MICROPLASTIC FACTSHEET. Retrieved from https://oceancare.org/wpcontent/uploads/2016/07/Factsheet_Mikroplastik_EN_2015.pdf
Rochman, C. M. (2018). Plastic Pollution in Aquatic Ecosystems. Retrieved from https://torontorap.ca/app/uploads/2017/08/Rochman-Jan-2018.pdf
Shah, A. A., Hasan, F., Hameed, A., & Ahmed, S. (2008). Biological degradation of plastics: A comprehensive review. Biotechnology Advances, 26(3), 246–265. doi: 10.1016/j.biotechadv.2007.12.005
Zheng, Y., Yanful, E. K., & Bassi, A. S. (2005). A Review of Plastic Waste Biodegradation. Critical Reviews in Biotechnology, 25(4), 243–250. doi: 10.1080/07388550500346359