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Plastic in Marine Litter
LI WAI CHIN1 AND TSE HIN FUNG
ABSTRACT
Anthropogenic litter is found in marine environments from the beach, beach sediment and surface water to the seafloor. Plastic can persist and accumulate in the marine environment for a long period because of its light weight and degradation-resistant properties. The global production of plastic increased from 230 tonnes in 2005 to 322 tonnes in 2015. It has been estimated that plastic production will increase to 330 tonnes in 2017. Mismanaged plastic waste can enter the marine environment via both land-based sources and oceanic-based sources. Ocean gyres, oceanic convergence zones and even polar regions are regarded as plastic waste accumulation hotspots. Over 690 species including seabirds, turtles, and fish have been reported to ingest plastic debris. Additionally, large plastic debris, especially derelict fishing gear and packing bags, pose a plastic entanglement risk to marine organisms. Plastic debris can act as vectors for the accumulation of hydrophobic organic pollutants and heavy metals or metalloids, and thus potentially cause harmful effects to marine organisms, such as endocrine system disruption, liver and kidney failure, hormone alterations and teratogenicity. This chapter summarizes the sources, distributions and fates of plastic debris in the marine environment, as well as the physical and chemical effects induced by plastic debris. Finally, recommendations including legislation reinforcement, better management of waste collection systems and landfills, raising the awareness of different stakeholders and the application of advanced technology are suggested to reduce the amount of plastics in the marine environment.
1 Introduction
Despite several types of litter being reported in the marine environment, plastics are of particular concern and the most commonly recorded materials.1–3 Plastics Europe4 reported that the global plastic production increased from 230 tonnes in 2005 to 322 tonnes in 2015. The most commonly used type of plastic is polypropylene (PP) (19.1% of total production) (see Table 1), which is mainly used for food packaging, containers, and pipes. Plastic debris has been widely reported in the marine environment, including in surface waters,5 on beaches and shorelines6 and on the seafloor.7 The amount and accumulation of plastic can be attributed to several factors such as ocean currents, winds and tides, which could transport plastic to remote regions far from the original sources.8 Plastic debris tends to accumulate and persist in the marine environment because of its degradation-resistant properties.9 Therefore, plastic tends to degrade and break down into small pieces, which are regarded as microplastics. There is no internationally agreed definition of the size below which a small piece of plastic should be called a microplastic. In this literature, microplastics are defined as plastic particles that are less than 5 mm in diameter, which can be divided into primary microplastics and secondary microplastics, while macroplastics are defined as greater than 5 mm in diameter. Due to the large surface-area to volume ratio of plastic debris, particularly microplastics, a wide variety of marine organisms, such as fish,10 seabirds,11 sea turtles,12 and other marine mammals,13 are highly prone to plastic ingestion and entanglement. The physical properties and surface hydrophobicity of plastic debris make them a vector for the adsorption of hydrophobic organic contaminants or heavy metals and metalloids; thus, they pose a risk to marine organisms. In this chapter, the sources, occurrence, fates and potential impacts of plastic debris will be reviewed. Finally, recommendations are provided to reduce and control the potential sources of plastic debris.
Table 1 Types of plastic commonly found in the natural environment.4,14–17
| Type | Specific gravity | Use/application |
| Polyethylene terephthalate (PET) | 1.37 | 7.1% | Bottles for water, soft drinks, juices and cleaners |
| Polyurethane (PUR) | 1.07 | 7.5% | Building insulation, pillows and mattresses and insulating foams for fridges |
| High-density polyethylene (HDPE) | 0.94 | 12.1% | Toys, milk bottles, shampoo bottles, pipes and houseware |
| Polyvinyl chloride (PVC) | 1.38 | 10.1% | Window frames, profiles, floor and wall covering, pipes, cable insulation, garden hoses and inflatable pools |
| Low-density polyethylene (LDPE) | 0.91–0.93 | 17.3% | Reusable bags, trays and containers, agricultural film and food packaging film |
| Polypropylene (PP) | 0.85–0.83 | 19.1% | Food packaging, sweet and snack wrappers, hinged caps, microwave-proof containers, pipes, automotive parts and bank notes |
| Polystyrene (PS) | 1.05 | 6.9% | Packaging foam, food containers, plastic tableware, disposable cups, plates, cutlery, CDs, cassette boxes, tanks, jugs and building materials (insulation) |
| Others |
| High impact polystyrene (HIPS) | 1.08 | 19.9% | Refrigerator liners, food packaging, vending cups and electronics |
| Polyamides (PA) (nylons) | 1.13–1.35 | | Fibres, toothbrush bristles, fishing line, under-the-hood car engine moldings and making films for food packaging |
| Acrylonitrile butadiene styrene (ABS) | 1.06–1.08 | | Electronic equipment cases (e.g., computer monitors, printers, keyboards), drainage pipe and automotive bumper bars |
| Polycarbonate (PC) | 1.20–1.22 | | Compact discs, eyeglasses, riot shields, security windows, traffic lights, lenses and construction materials |
| Polyester (PES) | 1.40 | | Fibres and textiles |
| Polyethylene (PE) | 0.91–0.96 | | Wide range of inexpensive uses including supermarket bags and plastic bottles |
2 Plastic in Marine Litter
Marine litter is regarded as “any persistent, manufactured or processed solid material discarded, disposed or abandoned in the marine and coastal environment including all materials discarded into the sea, on the shore, or brought indirectly to the sea by rivers, sewage, storm water, waves, or winds”.18 Man-made objects that are unable to naturally degrade in a short period of time could become marine litter if they are mismanaged. According to UNEP,19 common marine litter items are paper, wood, textiles, metal, glass, ceramics, rubber and plastic abandoned by people. A recent study estimated that 2.5 billion metric tonnes of municipal solid waste was generated in 2010 from 192 coastal countries (93% of the global population), and 11% of the generated waste was plastic (275 million metric tonnes).20 Approximately 1.7–4.6% of the generated plastic waste was mismanaged, which leads to approximately 4.8–12....
