Microplastics in ports worldwide: Environmental concerns or overestimated pollution levels?

Plastic pollution, a pervasive environmental crisis, arises from the improper disposal of non-biodegradable plastics, endangering species and ecosystems worldwide. While microplastics (MPs) have been extensively studied in various ecosystems, they have received scant attention in port environments, despite their pervasive presence. This review selected published articles conducted in ports worldwide between 2010 and 2024 to determine the concentration, accumulation characteristics, and driving factors. A total of 57 studies across 78 ports met the selection criteria, examining water, sediment, and biota in 49, 51, and 23 ports, respectively. The average concentrations of MPs in water collected by net and grab sampling, sediment, fish, and invertebrates were approximately 39.2 +/- 68.4 items/m(3), 4100.7 +/- 5761.8 items/m(3), 243.6 +/- 240.2 items/kg, 26.1 +/- 21.1 items/individual, and 9.4 +/- 8.1 items/individual in ports worldwide, respectively. Asia and the Americas exhibited the highest concentration of MPs in ports across all media. The dominant MP morphotypes included fibers, fragments, films, foams, pellets, and spheres, with sizes frequently between 1 and 1000 mu m in biota and water and between 1 and 5 mm in sediments. Port structures and the presence of rivers are key drivers of MP accumulation. MP pollution in ports poses potential ecological and health risks. Among the studied ports, 23% had MP numbers in sediment greater than the predicted no effect concentration (PNEC). The presence of MP in biota and the capability of MP to adsorb other contaminants pose a threat to human health.