World Aquaculture December 2020

WWW.WA S.ORG • WORLD AQUACULTURE • DECEMBER 2020 35 in bivalves. Although fish are eaten after removing the gut, bivalves are eaten without removing the digestive tract. Therefore, by consuming 225 g portion of mussels, up to 900 pieces of microplastic are consumed. Small microplastics and nanoplastics are reported to pass the fish intestinal barrier and to be transported in the muscle; nevertheless, because of the difficulties in assessing nanoplastics, little data is available about their presence in fish fillets, and in some cases, a revision of the same data is envisaged. Touissaint et al. (2019), in a review that analyzes peer-reviewed publications since 2010, documented the presence of MNPs in the human food chain. Along with Hantoro et al. (2019), they concluded that it is still not possible to assess human exposure to MNPs through food consumption due to a scarce availability of data and a lack of standardization of methodologies. Microplastics in Food and Feed of Farmed Seafood Being aware of the existing difficulties, a question that arises when risk management in fish and shellfish is carried out would be: Can we tackle the control of micro- and nanoplastics, at least in farmed seafood? Fish may assimilate MNP from feed and the water (Su et al. 2019). Separating micro- and nanoplastics fromwater and feed may represent an economically insurmountable problemwith existing technologies. Roch et al. (2020) compared wild-feeding fish and farmed fish when feeding on the environment. They also considered fish feeding behavior by comparing visual foraging and chemosensory foraging fish. Among farmed fish, a developed sense of taste limits the unintentional ingestion of microplastic particles. The same authors reported experimental data indicating that fish actively foraged on microplastics when no food was available. A huge difference in the content of microplastics has been reported in water from different world regions, ranging from 10 -6 to 10 4 microplastic particles/m 3 (Shim et al. 2018). Moreover, along the coast, placement of net pens in areas with major accumulation of MNPs due to the tidal currents should be avoided. Adequate feeding strategies that avoid loss of feed pellets should also be applied. Although few data are available on the micro- and nanoplastics content in fishmeal, important differences may be expected in fishmeals of different oceans of origin (Fig. 3). Moreover, a compromise between the nutritional value and the micro- and nanoplastics content in other protein sources, such as cereal grain meals, insect meals, poultry meals and in lipid sources, could possibly lead to the production of a feed in which the content of micro- and nanoplastics is reduced to a minimum. Depuration While waiting for a threshold of risk to be developed for food, a precautionary approach would suggest reducing insofar as possible the amount of plastics in the food we consume. Seafood from different world regions may be contaminated by MNPs to different degrees due to different levels of local contamination in the water and food chain (Shim et al. 2018). In contrast, the objective to exert some control over farmed fish and shellfish does sound reasonable, at least to some extent. Therefore, any tentative plan to depurate seafood that assimilated micro- and nanoplastics fromwater or from the natural food chain, or removing MNPs from the flow water used in aquaculture and from the ocean where pen cages are immersed, sounds idealistic. Nevertheless, the development of technologies to depurate mussels in a closed system such as a depuration basin and intensive water recirculation systems (RAS) for fish farming might be feasible after adequate effort is invested in research: here, preliminary results are already available from our laboratory (M. Saroglia et al. , unpublished data). The Need for a Precautionary Approach The main reviews reporting communication of the risk for humans are EFSA (2016), which reported “no evidence of risk,” and FAO (2017). The adverse effects of microplastic ingestion underscored by the FAO have only been observed in aquatic organisms under laboratory conditions, while in wild aquatic organisms microplastics have only been observed within the gastrointestinal tract, which at least in finfish is removed before eating. Plastics found in terrestrial and marine environments, nanoplastics in particular, can enter the human body, either by inhalation or ingestion, particularly of shell sh and crustaceans (Waring et al. 2018). Even if absorption across the gastrointestinal tract is relatively low, nanoplastics that are more readily absorbed may accumulate in the brain, liver and other tissues in aquatic species and other animals, suggesting that toxicity could potentially affect the central nervous and reproductive systems. Although EFSA (2016) reported “no evidence of risk,” we should bear in mind that it is different from “evidence of no risk.” Thus, together with the recommendation to dedicate financial resources to studies oriented toward the management of the MNPs risk, a precautionary approach should be applied to reduce the consumption of micro- and nanoplastics with food as much as possible. Notes This study is part of activity granted with the project AGER 4F, supported by an Italian Banks Foundations consortium. Marco Saroglia and Genciana Terova, Dept. of Biotechnology and Life Sciences, University of Insubria, Varese, Italy References Amereh, F., M. Babaei, A. Eslami, S. Fazelipour and M. Ra eeet. 2020. The emerging risk of exposure to nano(micro)plastics on endocrine disturbance and reproductive toxicity: From a ( C O N T I N U E D O N P A G E 3 6 ) FIGURE 3. Various protein and oil components of fish feed may potentially carry micro- and nanoplastics (Source: https:// analyticalscience.wiley.com/do/10.1002/gitlab.16837/full/#media -1).