Page - 86 - in Freshwater Microplastics - Emerging Environmental Contaminants?

1 Introduction Plastics are the most versatile materials invented by man. The use of plastic materials has brought great convenience to our daily lives but notwithout down- sides [1]. Inappropriatedisposalofwastedplasticshascausedseriousenvironmen- tal problems. The presence of plastic debris in the environment not only affects the aesthetical and recreational values of ecosystems but may also present a persistent pollution problem that will continue to accumulate into future genera- tions [2–4].Onceentering the environment, plastics are subject tophysical, chem- ical, andbiologicalweatheringprocesses,whichact toslowlybreak largepiecesof plastic into smaller fragments. Plastics less than 5 mm are considered as “microplastics” [5]. However, no universally accepted definition in terms of the size rangeformicroplastics iscurrentlyavailable [6].Microplasticscanbeingested byaquaticorganisms,whichmight causepotential adverseeffects andarouse food safety concerns [7–10].As a result,microplastic pollution has become an issue of emerging concern and is drawing increasing attention from both the public and scientific community. Microplastic pollution in the marine environment has received widespread attention.Microplasticsarefoundubiquitouslyinbenthicandpelagicenvironments in theoceans [11, 12]. In oceans, the high abundanceofmicroplastics observed in the large-scale subtropical convergence zones is attributed to the circulation of ocean currents [13–15].Accumulation ofmicroplastics in shoreline sediments has also been observed worldwide [16–19]. Themajority of plastic debris in oceans originates from land, althoughdischarges fromoceanvessels,military operations, and general shipping activities cannot be discounted [20]. It was estimated that 275millionmetric tonsofplasticwastesweregenerated in192coastalcountries in 2010, and about 4.8–12.7millionmetric tons are estimated to endup in the ocean [20]. Based on this estimation, over 95% of the plastic wastes will remain on continents to be either recycled, disposed of in landfills, go for incineration (with orwithoutenergy recovery),orotherwisebediscardedandstayoncontinents [21]. Only a few studies have addressed the issue ofmicroplastic pollution in terres- trial environments and inlandwaters in contrast to the vast amount of research in marine environments. These studies suggest inland waters are facing similar microplastic accumulation problems as found in the oceans [22, 23].Many inland watersarehabitats foraquatic species thathave importantecologicalandeconomic value and provide services for recreation, aquatic products, and water resources. Therefore, it is important to understand the occurrence, fate, and effects of microplastics in inlandwaters [24–26]. Asia is the largest and themost populous continent in the world. Asia covers about 30% of Earth’s total land area and supports about 60% of the world’s population. There are about a 1,000 ethnic groups with diverse languages and cultures. Nearly all countries in Asia are developing countries, which are under rapiddevelopmentwhile facinggrowingenvironmentalproblemsat thesametime. In this chapter, we reviewed the available literature onmicroplastic pollution in inlandwaterswith a specific focus onAsia.Aconsiderable lackof data for inland 86 C.Wuet al.