International Journal of Marine Science, 2025, Vol.15, No.5, 245-254 http://www.aquapublisher.com/index.php/ijms 249 with pollutants, the toxic substances on the plastic can be desorbed and released under the media conditions of the biological digestive tract, causing composite pollution exposure. For example, an experiment exposed fish to clean microplastics, microplastics adsorbed with heavy metal cadmium and cadmium ion solutions, and found that the cumulative amount of cadmium and oxidative stress in the bodies of fish that were ingested at the same time were higher than those in the exposed group alone (Saikumar et al., 2024). This shows that the coexistence of microplastics and heavy metals can produce synergistic toxicity, causing organisms to withstand greater pressure. The interaction mechanism between microplastics and pollutants involves surface adsorption, complex bonding and carrier transport. Aging microplastics in the environment may lead to higher combined toxicity due to rough surfaces and increased oxygen-containing functional groups. 4.3 Investigation on the pollution of microplastics in the body of Mediterranean mussels As a semi-enclosed sea area, the Mediterranean has dense population along the coast and frequent tourism and fishery activities, and its microplastic pollution situation has attracted much attention. Among them, investigations of filter-feeding shellfish such as mussels are often used as a classic case to indicate Mediterranean microplastic pollution. The study pointed out that the presence and type of microplastics in mussels is related to the degree of pollution in the collected sea areas, and the amount of microplastics contained in mussels near cities and ports is significantly higher than that in remote clean sea areas (Gedik and Eryaşar, 2020). In addition, the microplastic loads in the aquaculture mussels and wild mussels also differ slightly, which may be related to the water exchange conditions and bait source in the aquaculture area. Another survey on Mediterranean mussels further analyzed the distribution of microplastics in organisms. Through detection of mussel digestive glands, gills and other tissues, it was found that microplastics mainly gather in the digestive system, and a small amount can cross the epithelium and enter the gill tissue. This shows that most of the microplastics enter the digestive tract through feeding, and some of them will be excreted with the feces. Those that are not excreted may be embedded in the intestine or transferred to other tissues, causing continuous irritation and inflammation. The microplastic pollution in Mediterranean mussels has caused concerns about food safety, because mussels are seafood commonly consumed by local residents, and the daily shellfish consumed by people may bring a certain amount of microplastic into the human body (Gedik et al., 2022). 5 Potential Risks of Microplastics to Human Health 5.1 Food chain transmission and seafood safety hazards Ocean microplastics are subtly entering human dining tables through the food chain, becoming a new food safety hazard. Microplastic particles have been detected in all seafood widely consumed by humans. Especially for the entire shellfish and small fish that are eaten, the human body cannot remove the digestive tract when ingested, and the microplastic accumulated in the body will directly enter the human digestive system. Research review shows that the average number of microplastic particles per gram of soft tissue sold on the market contains 0.2~0.3 microplastic particles; a typical seafood dieter may consume tens of thousands of microplastics from aquatic products every year. Although most of the microplastics can be excreted from the body through human feces, some small-sized particles may pass through the digestive tract mucosa and enter the blood circulation, and accumulate in the body (Marszałek et al., 2024). This has raised concerns about human health risks: the chemical components of microplastics themselves, their additives and adsorbed contaminants, may cause potential toxicity to the human body. 5.2 Test results of microplastics in drinking water and salt In addition to seafood, microplastics may also enter the human body through daily dietary channels such as drinking water and salt. In recent years, investigations from many countries have reported microplastics detected in drinking water sources such as tap water, bottled water, and well water. For example, a study has sampled 11 brands of bottled water worldwide and found that 93% of the samples contain microplastic particles, with an average of more than 10 particles per liter of water. Although a 2019 report by the World Health Organization (WHO) believes that the current concentration of microplastics in drinking water is at a low risk to human health, it also emphasizes that due to limited evidence, further research on the long-term effects of smaller particles of
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