Polypropylene (PP)    Translucent and High melting point    Ketchup bottles, 
Polystyrene (PS)     Brittle and affected by fats and solvents     Egg boxes
Other(7) NylonAcrylonitrile butadiene styrene (abs) Polycarbonate (pc) layered or multi-material mixed polymers

2 Microplastics

The term ‘microplastics’ and ‘microlitter’ has been defined differently by various researchers. Gregory and Andrady (2003) defined microlitters as the barely visible particles that pass through a 500 μm sieve but retained by a 67 μm sieve (∼0.06–0.5 mm in diameter) while particles larger than this were called mesolitter. Others(Fendall and Sewell, 2009, Betts, 2008, Moore, 2008), including a recent workshop on the topic (Arthur et al., 2009) defined the microparticles as being in the size range <5 mm (recognizing 333 μm as a practical lower limit when neuston nets are used for sampling.) Particles of plastics that have dimensions ranging from a few μm to 500 μm (5 mm) are commonly present in seawater (Ng and Obbard, 2006, Barnes et al., 2009). For clarity, this size range alone is referred to as ‘microplastics’ here; the larger particles such as virgin resin pellets are referred to as ‘mesoplastics’ after Gregory and Andrady (2003). Persistent organic pollutants (POPs) that occur universally in seawater at very low concentrations are picked up by meso-/microplastics via partitioning. It is the hydrophobicity of POPs that facilitates their concentration in the meso-/microplastic litter at a level that is several orders of magnitude higher than that in seawater. These contaminated plastics when ingested by marine species present a credible route by which the POPs can enter the marine food web. The extent of bioavailability of POPs dissolved in the microplastics to the biota (Moore, 2008) and their potential bio-magnification in the food web (Teuten et al., 2007) has not been studied in detail.
Microplastic (less than 5 mm was commonly defined) pollution, identified as an important emerging threat by a horizon scan of global conservation issues for 2010 (Sutherland et al., 2010), has been a particularly concern in recent years because of its prevalence in the ocean and potential ingestion by marine organisms (Andrady, 2011). The occurrence and distribution of microplastics to the global marine environment include both primary sources (derived from hand and facial cleansers, cosmetic preparations, scrubbers in air-blasting, and production waste from plastic processing plants) and secondary sources (derived from fragmentation of larger plastics as a result of physical and chemical effects) (Zitko and Hanlon, 1991, Gregory, 1996, Barnes et al., 2009).
Microplastics are compositional complex containing a wide range of additives such as plasticizers, fillers and stabilizers. They also provide the surface area for the adsorption of various chemicals in the environment including drugs and hydrocarbons, which complicate their ecotoxicological effects (Tang, 2020, 2021). Together with nano plastics which have the potential to enter cells and disrupt cellular functions, their removal from the environment has been a primary concern(Tang, 2020). As long-term solutions to microplastics elimination from the environment have yet to be framed, water and  provide an immediate and feasible means of microplastic removal.  
Microplastics can be transported by the hydrodynamic process, winds, and ocean currents, and have been found abundant in almost every corner of our oceans over the past few years, ranging from the coastline (Claessens et al., 2011; Martin et al., 2017), the Irish continental shelf (Martin et al., 2017), the Atlantic Ocean(Cózar et al., 2017; Law et al., 2010), the Pacific Ocean(Eriksen et al., 2013; Law et al., 2014), European coastal areas (Interwies et al., 2013) and the Indian Ocean(Reddy et al., 2006), even to the polar regions(Bergmann et al., 2016; Waller et al., 2017) and the deep-sea (Taylor et al., 2016; Van Cauwenberghe et al., 2013; Woodall et al., 2014). As pointed out by the G20 Action Plan on Marine Litter (2017), it is an arduous task to reverse the far-reaching impact of marine pollution, which will take 67 ships one year to clean up less than 1% of the garbage in the North Pacific Ocean. Tracks of microplastics even extend to terrestrial environments inland (McCormick et al., 2016) , threatening access to clean water and the sustainable management of water in freshwater systems.   
2.1 Categories of microplastics
Microplastics encountered in the marine matrices are broadly classified into 2 types; 1) Primary Microplastics and 2) Secondary Microplastics.
1. Primary microplastics are originally and intentionally manufactured in the size range of 1 nm to 5 mm and have applications in personal care products like toothpaste, shower gel, scrubs, cosmetics, and air-blasting (Fendall and Sewell, 2009). 
2. Secondary microplastics result from the breakdown of large plastic items, e.g from fishing gears, ships, aquaculture, recreational activities, and transport of plastic products into finer particles (Gesamp, 2015 ; Fendall et al., 2009 ; Bowmer et al., 2010). The formation of microplastics in the ocean.     

3 Management of microplastics in the marine environment

Microplastics in marine waters and their adverse effects have been reported since the early 1970s, giving rise to research based on microplastics in aqueous environments (Carpenter and Smith, 1972).  A sustainable approach to both production and consumption of plastic materials with global efforts has been geared towards the management of marine debris via prevention. The upstream measures of preventing the sources of plastic materials in the marine environment are more cost-effective than the focus on downstream clean-up exercises (Kershaw, 2016). Risk assessments of various regions can be used to predict global hotspots of plastic/microplastics’ prevalence in the marine environment, and well-defined protection goals can be meted out, especially for the sustenance of biodiversity (Gall et al.,2015 ; Löhr et al., 2017).
The social slogan of “3Rs: reduce, reuse, and recycle”, used in the management of most wastes found in the environments, has continuously been implemented in the case of plastic wastes, more so to traditional plastics, whose long carbon chains make them difficult to degrade or be broken down by microorganisms (Schuyler, et al., 2016 ). The 3Rs are what (Lohr et al., 2017) reported as a circular economy approach, as a means of a sustainable long-term solution, from the existing linear economy. Upcycling (reuse), which is the art of recycling to improve a material’s value, and redesigning of products to make them less hazardous, as well as improved producer responsibility, are also means of sustainable management of plastic waste (Callister et al., 2008 ). Open landfills and dumpsites seat a considerable amount of plastic waste that is often flushed into the ocean during rains. Recycling and reusing plastic products are some of the most effective actions to reduce the volumes of plastic wastes that must be flushed into the ocean. In improving recyclable plastic material wastes, chemical recycling has been considered as a sustainable alternative in the past decade, i.e., the collection of used plastics and chemically recycling them into raw materials for brand-new plastic production of the same properties as the original, and avoiding the incidence of new monomer feedstock (Singh et al., 2017).
The quest for (marine) environment-friendly plastics gave rise to green plastics (green chemistry) (Thompson et al., 2009). Green plastics involve the use of biodegradable plastics. Among the considered perspectives toward sustainable plastic production and curbing plastic wastes, commodity polymers can be made through the use of monomers from plant sources or by producing an alternative to fuel-based products from plant-based polymers (García et al., 2014).

4 Recommendations and conclusions

4.1 Recommendations:

4. 2 Conclusions

The absence of statutory law formulations, as well as being weak and poorly enforced with inadequate compliance in most developing countries, contributes to the continuous discharge of plastics and microplastics into the coastal waters. As there exist environmental regulations to monitor different environmental pollutions, there should be specific environmental guidelines and standards that would guide plastic discharge and non-compliance of policies in countries.  Therefore, in-depth knowledge of the environmental fate and potential adverse effects of microplastics in aquatic environments is needed. With the increase in microplastics and its effects on marine ecosystems, it is suggested that community and public vanguards could be initiated to develop a feasible platform for microplastics’ mitigation and ecosystem balance.

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