Microplastics in Different Tissues of a Commonly Consumed Fish, Scomberomorus guttatus, from a Large Subtropical Estuary: Accumulation, Characterization, and Contamination Assessment

SIMPLE SUMMARY: It is evident that microplastics can enter the human body via dermal contact, inhalation, and food intake and pose a significant threat to human health. Therefore, understanding microplastics is essential for protecting the environment and human health. This study identified 48.7 MPs on average in each fish of king mackerel, with varying concentrations in different tissues, such as the digestive tract, gills, and muscle. The size and characteristics of these MPs varied but many were <0.5 mm in size (97.74%) and fiber-like, with a lot in the muscle tissue, which raises concerns for human consumption. Three types of plastic polymers were identified in the MPs, likely from things like food packaging and plastic waste. The fish’s muscle and digestive tract were significantly contaminated with MPs, indicating a high level of pollution. ABSTRACT: Microplastics (MPs) ingestion by fish signifies a worldwide threat to human health but limited research has examined their existence within the consumable portions (muscle) of fish. Thus, this study was undertaken to unveil the prevalence, characterization, and contamination extent of MPs across various body tissues, including the muscle of the king mackerel (S. guttatus) from the lower Meghna estuary in Bangladesh—a pioneering investigation in this region. In our analysis, we identified a total of 487 MPs, with an average abundance of 48.7 ± 20.3 MPs/individual. These MPs were distributed across different tissues, with respective concentrations of 0.84 ± 0.45 items/g in the digestive tract, 2.56 ± 0.73 items/g in the gills, and 0.3 ± 1.72 items/g in the muscle tissue. The observed variations among these tissue types were statistically significant (p < 0.05). Moreover, a significant positive correlation indicated that fish with higher weight had higher MPs in their gills and DT (digestive tract). The majority were <0.5 mm in size (97.74%) and exhibited a fiber-like shape (97.74%), with a notable prevalence of transparent (25.87%) and a pink coloration (27.92%). Remarkably, the majority of MPs were discovered within the size range of <0.5–1 mm (100%), particularly in the muscle tissue, signifying a substantial transfer of MPs into the human diet. Besides, we discovered only three polymer types of microplastics which could be attributed to the extensive use of food packaging, plastic containers, wrapping plastics, residential garbage, and plastic pipes that end up in the aquatic environment via river discharges. The contamination factor (CF) values of fish muscle (5.75) and the digestive tract (5.50) indicated that these fish organs were considerably contaminated (3 < CF < 6) with MPs. The pollution index of MPs (PLI > 1) indicated a high contamination level for MPs pollution of S. guttatus in the lower Meghna River estuary.