# Ecotoxicological Assessment of Microplastics in Freshwater Sources--A Review
###### Abstract  
High living standards and a comfortable modern way of life are related to an increased usage of various plastic products, yielding eventually the generation of an increased amount of plastic debris in the environment. A special concern is on microplastics (MPs), recently classified as contaminants of emerging concern (CECs). This review focuses on MPs' adverse effects on the environment based on their bioactivity. Hence, the main topic covered is MPs' ecotoxicity on various aquatic (micro)organisms such as bacteria, algae, daphnids, and fish. The cumulative toxic effects caused by MPs and adsorbed organic/inorganic pollutants are presented and critically discussed. Since MPs' bioactivity, including ecotoxicity, is strongly influenced by their properties (e.g., types, size, shapes), the most common classification of MPs types present in freshwater are provided, along with their main characteristics. The review includes also the sources of MPs discharge in the environment and the currently available characterization methods for monitoring MPs, including identification and quantification, to obtain a broader insight into the complex problem caused by the presence of MPs in the environment. microplastics; freshwater; ecotoxicology; (micro)organisms 2020 202  
sources identified are synthetic textiles (34%), tire wear (29%), city dust (24%), road markings/dust (7%), marine coatings (4%), microbeads (2%), and plastic pellets (0.3%) [19; 21]. MPs distribution, abundance, and occurrence in the environment are affected by various factors: type of environment, MPs properties (type, density, size, and shape), climate regions (air turbulence, waves), industrialization, urbanization (proportional to MP's concentrations), waste management, development in general, and the living standard of gravitating society [14; 15]. MPs are insoluble in water and have low susceptibility to degradation; therefore, they remain in the environment for long period [6]. MPs possess large bioaccumulation potential [17]. Studies showed that MPs exhibited harmful effects to organisms, particularly aquatic ones due to the direct contact. Hence, these may be reflected as behavioral effects, oxidative stress, neurotoxicity, genotoxicity, reproductive impairment, and hepatic damage [9; 22; 23]. MPs intake by humans is mostly through food and beverages, such as fish [17], mollus [24], sugar [25], sea salt [26], beer [27], or even tap and bottled water [7; 28]. Hence, it is not surprising that many countries recognize MPs as contaminants of emerging concern (CECs) with severe hazard potential [29; 30]. Understanding MPs' behavior in the environment and related impact on abiotic and biotic qualities of ecosystems (including the possible impact on humans) is the basis for correct risk assessment. European Chemicals Agency (ECHA) considers that current information is insufficient to derive a robust predicted non-effective MPs concentration, i.e., a threshold value that could be used as proof that risks are adequately controlled. This means that any MPs release in the environment should be considered as risk [31]. Therefore, ECHA proposed the restriction of MPs usage in different professional, agricultural, industrial, and consumer products. The 1 st restriction phase is planned for 2021 with a 5-year transition period; ECHA considered that is sufficient time for the industry to substitute MPs. The estimation is that the proposed restriction would yield a reduction of MPs emission of ~400,000 tones within the next 20 years [31]. Additional devastating fact is that developed world economies recycle < 30% of plastic-waste [32]. European Commission brought European Strategy for Plastics in a Circular Economy [33] presenting the vision for confronting MPs pollution, including better design of plastic products, a higher rate of plastic-waste recycling, and better quality recyclates--all boosting the recycled-plastics market.