Toxicity of nano- and microplastics on marine and freshwater fish: A multi-scale perspective from organ systems to cells

Abstract

Nano- and microplastic pollution is increasingly recognized as a global threat to aquatic organisms and human health. These plastics are widespread in both marine and freshwater environments and pose significant risks to fish health. This review explores the routes of exposure, accumulation, and adverse effects of nano- and microplastics on fish, from the organ system to the cellular level. The primary routes of exposure are through ingestion and uptake via the gills. Once inside the body, these plastics accumulate in the gut and gills, penetrate the bloodstream, and bioaccumulate in other tissues. Exposure leads to intestinal and hepatic damage, disrupts digestive enzyme activity, induces oxidative stress, alters gut microbiota and metabolism, and causes digestive tract dysfunction. In the respiratory system, plastic accumulation in the gills induces hyperplasia, excessive mucus secretion, and impairs oxygen exchange. Small-sized particles can enter the bloodstream and reach the heart, causing cardiotoxicity, altered heart rate, and changes in cardiac sarcomeres, along with disruptions in blood biochemical parameters. Upon reaching the nervous system, nano- and microplastics cause neurotoxicity, oxidative stress, cellular damage, and neuroinflammation. Tissue damage and oxidative stress also activate immune responses, including pro-inflammatory reactions and increased expression of immune proteins and molecules. At the cellular level, nanoplastics may accumulate in lysosomes or cross cell membranes, leading to elevated oxidative stress, potential genotoxicity, and membrane damage. The severity of these effects depends on particle size, type, concentration, and duration of exposure. This review aims to enhance understanding of the systemic and cellular toxicities of nano- and microplastics in fish, providing a foundation for future ecological risk assessments and the development of mitigation strategies.