A Hazard Index of Microplastics Contamination in Commercial Marine Fish Species and Mussels in the Southern Marmara Sea, Turkey

Microplastic (MP) pollution is an increasing concern in marine ecosystems due to the risk it poses to marine organisms and human health. This study aims to investigate the type, abundance, and properties of MPs in five commercially important fish species ( Engraulis encrasicolus , Trachurus trachurus , Sardina pilchardus , Sarda sarda , and Dicentrarchus labrax ) and Mediterranean mussels ( Mytilus galloprovincialis ). In the study, samples were collected from five different regions in the Southern Marmara Sea of Turkey. In addition, the polymer composition of MPs identified in the study was determined and evaluated according to the associated hazard index to determine the potential risks to marine life and human consumers. A total of 1734 MPs were identified in the gastrointestinal tracts (GITs) of fish samples ( n = 660), while 650 MPs were identified in mussel samples ( n = 50). The analyses revealed that there was significant interspecific and spatial variability in MP abundance, size, shape, and color. The most common MPs are those smaller than 0.3 mm in diameter. These are predominantly in the form of lines and beads in all species. Fourier transform infrared (FTIR) spectroscopy was used to identify the types of polymers present. The types of polymers identified in the study were polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and ethylene vinyl acetate (EVA). The most common polymers were PE and PP, which showed hazard indices classified as “hazard” and “high risk,” respectively. The study identifies potential health risks associated with MPs, particularly in marine organisms, including apex predators such as D. labrax and filter feeders such as mussels. These findings highlight the need for effective waste management strategies, stricter regulations, and increased public awareness to reduce pollution of marine environments with plastic.