World Aquaculture December 2020

WWW.WA S.ORG • WORLD AQUACULTURE • DECEMBER 2020 33 food, monitoring small plastic particles in the nanometer range still represents a problem. Effects of Microplastics on Humans According to recommendations of the FAO andWHO, a risk analysis should involve three steps: 1) risk assessment, 2) risk management and 3) risk communication. Risk assessments for humans are generally based on studies carried out with rodents. As such data are incomplete or lacking for plastics, a formal hazard characterization of plastic particles for human health is not yet possible (FAO 2017); therefore, more accurate studies are required. Nevertheless, some assumptions may be made according to existing literature. MNP contamination occurs mainly through food, drinking water and respiration, but other routes are also possible in humans. For instance, Pazzaglia et al. (1987) showed TEM electronic microscopy images of eroded polyethylene joint prostheses, in which eroded nanoparticles had evidently interacted with macrophage cells in patients, possibly representing harm to the innate immune system. This may be an example of so-called “frustrated phagocytosis,” which is the failure of macrophages to engulf their targets and remove or destroy them, leading to a prolonged inflammatory response and possible tissue damage (van Raamsdonk et al. 2020). It is estimated that 39,000-52,000 microplastic particles per capita per year are ingested with food by the American population, depending on sex and age (Cox et al. 2019); nevertheless, more than 90 percent of microplastics entering the intestine are released (EFSA 2016). Intestinal tight junctions can stop nanoparticles >1.5 nm in size but particles 0.1-150 μ m in size may be absorbed via the lymphatic system (M cells of Peyer plaques) and then found in plasma, internal organs and urine (Galloway 2015); polyvinyl chloride (PVC) particles from 5 to 110 μm have been detected in the portal vein of dogs (Volkheimer 1975). Results from in vitro trials carried out utilizing intestinal models as well as in rodents in vivo indicate that only 0.04-0.3 percent of particles 2 μm in size are retained in the system, although nanoplastics 50 nm in size account for only 0.2-7.0 percent of this total (FAO 2017). Gut inflammatory diseases increase the percentage of microplastics assimilated, as particles 3 μm in size were present in 0.20-0.45 percent of the administered dose of drugs used in treatments (Schmidt et al. 2013). Even with an absorption below 0.3 percent of S ome of the twentieth century’s revolutions have greatly contributed to reducing the specter of world hunger. Among them are the industrial process for producing ammonia, which is indispensable for fertilizing agriculture fields and resulted in two Nobel Prize awards for chemistry (Fritz Haber in 1918 and Carl Bosch in 1931), and Norman Borlaug’s studies on the genetics of cereals (Nobel Peace Prize in 1970). Then, a number of scientific findings and technological solutions, mainly after the Kyoto FAO Conference in 1975, promoted the exponential development of aquaculture all around the world. Nevertheless, a new problem has arisen. The food produced after the “Green Revolution” as well as the food generated by the subsequent “Blue Revolution” might be threatened by the industrial products developed after another Nobel Prize for chemistry awarded to Giulio Natta and Karl Ziegler in 1963 for their study on polymers. Being artificially created by humans, no microorganisms have been naturally developed to digest it. Therefore, the presence of micro- and nanoplastics in apparently any water source and agricultural food product, as well as in food products from fisheries and aquaculture, potentially represents one of the main food problems that science and technology should tackle in the twenty-first century. Plastic materials are released from different sources (e.g. industrial and personal care products) into the aquatic environment (Fig. 1). The action of UV radiation, abrasion and aquatic organisms slowly fragment macroplastics into micro- and nano-size particles (Dawson et al. 2018). Small plastic particles may be defined as either microplastics (0.1 μm - 5 mm) or nanoplastics (<100 nm) (micro- and nanoplastics, MNP). Plastic particles are now ubiquitous in the environment, dispersed through the action of wind, waves and water currents. Even if the release of plastics would cease immediately, it is assumed that those already present in the aquatic environment would form a greater number of smaller particles and several centuries will be required for them to decay naturally. Therefore, there is a need to gain knowledge of how to manage, control and detect the presence of these substances in food and to define an analysis of the risk that includes a still unknown threshold for humans. This is even more important considering the need to keep the human body capable of facing other threats that come from outside, such as infectious disease pandemics. Despite improvements in the analytical methods for detecting microplastics in water and Plastic is on the Table: Can We Manage to Reduce Micro- and Nanoplastics in Aquaculture Products? Marco Saroglia and Genciana Terova ( C O N T I N U E D O N P A G E 3 4 ) FIGURE 1. The magnitude of microplastic pollution around the world (Source: Hurley et al . 2018).