**3. Sources of microplastics emission into the marine ecosystem**

General littering, plastic waste mismanagement, tires, synthetic textiles, marine coatings, road markings, personal care products, plastic pellets, city dust, and release of wastewater from sewage treatment plants have been the main sources of microplastic pollution in the marine ecosystem [30]. Marine litter results from the indiscriminate disposal of refuses that are either directly or indirectly transferred to our seas and oceans [22, 31]. Whilst the emphasis of this study is on microplastics, in this section, we also consider the indiscriminate disposal of macroplastics, as with time, they eventually degrade into mesoplastics and microplastics. Plastic litter from land [terrestrial] sources contributes 80% of the plastics found in marine litter [26]. Such plastics include primary microplastics used in cosmetics and air-blasting, improperly disposed "user" plastics, and plastic leachates from refuse sites. With approximately half the world's population residing within 50 miles away from the coast, these kinds of plastic have a high likelihood of entering the marine ecosystem via rivers and wastewater systems, or by being blown off-shore [16, 32]. Plastic microbeads are utilized as components in cosmetic and personal care products for a range of functions, including an adsorptive state for active substance distribution, exfoliating, and viscosity control. Some products carry quite so much plastic as ingredients in which they are packaged [33]. These account for up to 10% of the product weight and thousands of microbeads per gram of product [34]. Microplastics used both in these cosmetics and as air-blasting media can easily enter waterways through domestic or industrial drainage systems [21]. The traditional use of products for

**Figure 3.** *Microplastic and garbage pollution present in the ocean [35].*

personal care culminates in the direct input of microplastic into industrial wastewater from homes, hotels, hospitals, and sports facilities, such as beaches. Cosmetic microbeads have been detected in field investigations conducted in many parts of the world (**Figure 3**) [36].

Tourism and recreational activities had contributed to the discarded plastics left along beaches and coastal resorts [21], as well as those from marine debris, observed on beaches arising from the beaching of materials carried on in-shore and ocean currents [32]. Whilst wastewater treatment plants will trap macroplastics and some small plastic debris within sewage sludge, a greater percentage of microplastics will pass through such filtration systems [13, 37, 38]. Plastics that enter river systems either directly or indirectly—will then be transported out into the ocean. A couple of studies conducted have shown how the high single-directional flow of freshwater systems drives the movement of plastic debris into the oceans [39, 40]. Another common marine source of plastic debris is fishing gear [26]. Discarded or lost fishing gear, including plastic monofilament line and nylon netting, which is typically buoyant and can therefore drift at variable depths within the oceans. This is particularly problematic due to its inherent capacity for causing entanglement of marine organisms, known as "ghost fishing" [31]. Historically, marine materials have been a great contributor to marine litter, with estimates indicating that during the 1970s the global commercial fishing fleet dumped over 23,000 tons of plastic packaging materials in the ocean [41]. Additionally, the manufacture of plastic products that use granules and small resin pellets, known as "nibs," as their raw material is another source of plastic debris [microplastics] [41–43]. Many plastics are introduced into the marine as pellets (usually 2–5 mm in diameter) or powders. Pellets are discharged into the marine environment through little or big occurrences along the entire plastic value chain during manufacturing, processing, transport, and recycling [44]. In the US alone, production rose from 2.9 million pellets in 1960 to 21.7 million pellets by 1987 [41].
