Ecotoxicological effects of microplastics on aquatic organisms: a review

Microplastics   ( <5 mm), which are classified based on primary or secondary sources, are widely distributed in the environment and exert significant effects on aquatic life forms; however, evidence regarding the ecotoxicological effects of microplastics on aquatic organisms is still limited. This research aims at filling a knowledge gap regarding generation sources, distribution, physicochemical properties, and biological behavior of microplastics (MP) in aquatic environments and their interaction with aquatic organisms. The literature indicates that concentrations of MPs observed in such environments are higher than the threshold for safe concentration (6650 buoyant particles/m³). MPs having large specific surface area, low polarity, and hydrophobic properties have been shown to absorb dichlorodiphenyltrichloroethane (DDT), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbon (PAHs), bisphenol A (BPA), polyfluoroalkyl substances (PFAS), antibiotics, and heavy metals. MPs adsorb large amounts of toxic organic chemicals (18,700 ng/g PCBs; 24,000 ng/g PAHs) and heavy metals (0.21-430 μg/g Cr; 0.0029-930 μg/g Cd; 0.35-2.89 μg/g As; 0.26-698,000 μg/g Pb). MPs originating from polystyrene (PS), polypropylene (PP), and polyvinylchloride (PVC) show greater toxicity toward aquatic organisms, with effects on the immune system, reproductive system, nervous system, and endocrine system. Thus, elucidating the cumulative toxic expression of MPs in different polluted environments is critical.