Environmental Transport, Bioaccumulation, and Health Impacts of Micro- and Nanoplastics: An Integrated Review

Micro- and Nanoplastics (MNPs) are pervasive environmental contaminants with increasing concern for human health and ecosystems. Their small size, persistence, and physicochemical diversity permit bioaccumulation, long-range transport, and trophic transfer covering aquatic, terrestrial, and atmospheric systems.

This review comprehensively integrates old to recent literature on the sources (both primary and secondary), physicochemical properties (surface chemistry, shape, size, charge, and chemical composition), transport (through soil, water, air, food webs, etc.), exposure routes (dermal, ingestion, and inhalation), detection and characterization techniques, toxicity (in vertebrates, invertebrates, aquatic organisms, etc., and plants), challenges, and mitigation of toxicity of MNPs.

Worldwide, evidence-based studies have reported the presence of MNPs in soil, water, food, air, and within organisms and plants. Physicochemical properties of MNPs strongly influence their distribution, exposure, and interaction with organisms. For example, most studies reported higher toxicity of nanoplastics than microplastics. Nanoplastics trigger oxidative stress, inflammation, genotoxicity, and autophagy, and cross various biological barriers, such as the lymphatic system and the gut lining. Microscopy, spectroscopy, thermal, and hybrid techniques play a crucial role in the detection and characterization of MNPs. All studies emphasized controlling MNPs' exposure, distribution, and toxicity by adopting effective, diverse strategies and raising awareness worldwide.

Plastic pollution (especially micro- and nanoplastics) is one of the major challenges today. Moreover, micro-and nanoplastics are ubiquitous. They are heterogeneous, adsorb various other pollutants and microbes, and transport them in different ecosystems. Their physicochemical properties allow them to enter biological systems and reach the liver, kidneys, heart, and the lymphatic and gut systems. They cause oxidative stress, inflammation, DNA damage, mitochondrial damage, autophagy, necrosis, and apoptosis. Moreover, nanoplastics cause higher toxicity than microplastics. Hence, there is an urgent need for advanced and standardized detection and characterization techniques.

MNPs pose a significant threat to the health of vertebrates, invertebrates, aquatic organisms, and plants. They cross multiple biological barriers, disrupt numerous organs/systems, and trigger apoptosis. There is an urgent need for advanced detection techniques to overcome MNPs. Integrated mitigation approaches are essential for effective regulatory action.