Osservazioni ed esperienze sul problema delle microplastiche nei mitili

During the last years, the presence of plastic waste dispersed in the environment has aroused concerns among the scientific community. Several studies have investigated its impact on marine and terrestrial ecosystems, with attention to those fragments small enough to be ingested by living organisms that can reach humans through the consumption of contaminated food, the so-called microplastics. While the effects of these particles on the environment have been studied in-depth, the data on their presence in food are not yet sufficient, the exposure levels are largely unknown and the potential effects on consumers are poorly understood. Furthermore, the lack of a standardized analytical protocol makes difficult to compare data available. More data is needed relating to microplastic distribution in food as well as the implementation of high-performance analytical protocols. In this regard, the research project was divided into two distinct trials: • The presence of microplastics was evaluated in 150 samples (1500 specimens) of mussels belonging to the three species most marketed in Europe, considering different commercial categories of sale, fresh and processed. In addition, a preliminary risk assessment associated with the consumption of an average meal of mussels contaminated with microplastics was performed. The mussel samples were digested using a 30% Vol. hydrogen peroxide solution and separated from undigested residues by adding a supersaturated saline solution. The filtered samples were observed under a stereomicroscope and the detected items were identified through the "hot point test" and with FTIR spectroscopy. A total of 0.14 ± 0.18 items/g was calculated. The amount of items found for Mytilus galloprovincialis was 0.25 ± 0.25 items/g, higher than that found for Mytilus edulis and Mytilus chilensis, of 0.10 ± 0.09 items/g and 0.08 ± 0.09 items/g, respectively. A higher quantity of particles was observed for fresh mussels (0.19 ± 0.21 particles / g) compared to precooked, shelled and frozen ones (0.09 ± 0.09 particles / g). FTIR spectroscopy confirmed the presence of particles in polyethylene, polypropylene, polyethylene terephthalate, polyvinyl chloride, and polystyrene. A quantity of 56 microplastics that can be ingested during the consumption of an average meal of mussels has been estimated, corresponding to 0.44 μg of plastic material. • Considering the hydrophobic nature of plastic materials, several studies have tested the effectiveness of some lipophilic dyes in identifying microplastics. Their use in biota has so far been excluded given the high amount of post-digestion organic residues that would inevitably be coloured, resulting in overestimates. The limits of use of the Nile Red dye for the identification of microplastics in marine mussels (Mytilus edulis) intended for human consumption were evaluated. The samples were subjected to experimental contamination with low density polyethylene microplastics. The mussel samples were digested using a 10% KOH solution and subsequently filtered on cellulose polycarbonate filters. The dye is absorbed on the surface of the particles, making them fluorescent when irradiated with blue light. The fluorescence of the particles was assessed by observing magnified photographs of the samples taken through an orange filter. The results obtained were validated by confirming the chemical composition of the particles found through analysis with FTIR spectroscopy. The lipophilic and solvatochromic nature of nile red has allowed the identification of plastic particles only in some cases.