Microplastiche e nanoplastiche nell’ambiente marino e potenziali ripercussioni sulla salute dell’uomo: fonti di contaminazione, presenza, distribuzione e accumulo lungo la rete trofica.

This thesis investigated the occurrence, abundance, and composition of microplastics potentially present in six different species of marine invertebrates from the Mediterranean Sea, sampled from the refrigerated counters of various local markets in the Sicily region. The aim was to assess the potential ecotoxicological and food safety risks associated with the ingestion of microplastic-contaminated food. A total of 775 specimens belonging to six species were analyzed, representing different trophic and ecological strategies: two species of gastropod mollusks (Patella caerulea, Bolinus brandaris), two species of filter-feeding bivalve mollusks (Mytilus galloprovincialis, Ruditapes decussatus), and two species of crustaceans (Squilla mantis and Callinectes sapidus). Microplastics were extracted from the samples through chemical digestion of the edible parts of each specimen, using a 10% KOH solution at 40 °C for 48 hours. The digestate was then filtered through cellulose ester filters with a pore size of 8 μm. Filter surfaces were examined under a stereomicroscope to detect particles morphologically compatible with plastic materials. Suspected particles were counted and classified by size, shape, and color. A representative portion of the visually identified particles was then analyzed using Fourier-transform infrared spectroscopy (FT-IR) to identify and confirm their polymeric nature. Based on the detected concentrations and identified polymer types, estimates were made of the annual per capita intake of particles related to the consumption of the analyzed species, along with a preliminary toxicological risk assessment. Potential plastic particles were detected in 52% of the analyzed samples, with an average of 1.40 ± 2.08 particles/sample and 0.15 ± 0.22 particles/gram. Fibers, predominantly blue and gray, were the most common form, with the size range between 501 and 1000 μm being the most represented. Although statistical analyses did not reveal significant differences between species in terms of particle abundance, filter-feeding bivalve mollusks showed the highest levels of contamination in absolute terms, suggesting a possible correlation between trophic strategy and likelihood of ingestion. However, in this type of sample collected directly from markets, post-capture contamination could significantly influence the number of particles detected, potentially contributing even more than the amount accumulated in the marine environment. FT-IR analysis revealed the predominance of polyethylene (PE), polyethylene terephthalate (PET), and polystyrene (PS)—polymers commonly associated with coastal anthropogenic activities. Chemical risk assessment was conducted using the Microplastic Hazard Index (PHI) proposed by Lithner et al. (2011). The overall PHI was 7747 (class IV, high risk), but this value was heavily influenced by the presence of a single highly toxic particle, identified as an epoxy copolymer—Poly[(2,3-epoxypropyl methacrylate):Styrene:Ethylene Dimethacrylate]—with an individual score of 7139 (class V). This result highlights the distorting effect that can arise from the low frequency of highly hazardous polymers, emphasizing the importance of a qualitative as well as quantitative approach in risk assessment. The results confirm that microplastic contamination in seafood intended for human consumption is a widespread and complex phenomenon, influenced by multiple factors ranging from the environment of origin to post-harvest handling. The presence of potentially toxic polymers, even in limited quantities, and the predominance of fibers suggest that not only the quantity but also the chemical composition and origin of the particles are key elements for risk evaluation. In this context, the need to standardize analytical protocols and to consider the entire food supply chain—from catch to plate—clearly emerges in order to realistically estimate human exposure. This study contributes to enriching the body of knowledge essential for critically and effectively addressing the issue of microplastics in food safety and public health.