Microplastics in fresh and processed mussels sampled from fish shops and large retail chains in Italy

During the last decade, the environmental impact of microplastics has aroused concerns since they are small enough to be ingested by living organisms intended for human consumption. In this study, the presence of microplastics was investigated in three mussel species sourced from various retailers in Italy, supplied as a fresh or processed product. The exposure to polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) was empirically assessed relating to the potential weight of plastic ingested with a mussel portion. The mussel samples were digested using a solution of hydrogen peroxide 30% Vol. and a density separation was performed adding a concentrated saline solution. The filtered samples were analysed under a stereomicroscope and the chemical composition of the visually sorted items was investigated by FT-IR spectroscopy. A significantly higher number of items was found in fresh mussels (0.20 ± 0.24 items/g w.w.; 0.40 ± 0.47 items/individual) than in processed ones (0.9 ± 0.10 items/g w.w.; 0.17 ± 0.19 items/individual). Several plastic polymers were identified by FT-IR and polyethylene was the dominant type. European shellfish consumers could be exposed up to ~585 MP/year and ~253 MP/year by the consumption of fresh and processed mussels, respectively. A portion of fresh and processed mussels contaminated with MPs would contribute only minimally to daily human exposure to PCBs and PAHs. The sources of microplastics in store-bought mussels may be several and related to the contamination along the food production chain. In this regard, further studies are needed to properly assess and manage the risk of microplastics in food.