From environment to body: sources and health consequences of microplastics and nanoplastics in humans

Microplastics (<5 mm) and nanoplastics (between 1 and 100 nm) have emerged as contaminants of worldwide public interest due to their widespread distribution in the environment. Increasing evidence indicates that humans are continuously exposed to these particles through various routes, raising concerns about their potential health implications. The primary sources of microplastics and nanoplastics in human exposure include fragmentation of lager plastic particles, packaging materials, cosmetics, industrial processes, synthetic textiles, and personal care products. These particles get into humans via ingestion, inhalation, and, to a lesser extent, dermal contact. Ingestion occurs through contaminated food, water, and seafood, while inhalation arises from airborne fibers and dust, and skin contact occurs when humans interact or come in contact with water or soil contaminated with particulate MNPs. Once internalized, MNPs can translocate across biological barriers, accumulate in tissues, and interact with cellular systems. Experimental and epidemiological studies suggest that MNPs may induce inflammation, immune dysfunction, infertility, genotoxicity, oxidative stress, and disruption of gut microbiome, with possible implications for reproductive, metabolic, and cardiovascular health. However, the magnitude of human health risks remains uncertain due to limited long-term data, methodological challenges in detection, and knowledge gaps concerning dose-response relationships. Understanding the sources, exposure routes, and human health effects of MNPs is crucial for risk assessment and policymaking. Addressing these challenges requires standardized analytical methods, interdisciplinary research, and strategies to mitigate plastic contamination at the source. This article highlights the current knowledge on human exposure to MNPs and underscores the urgent need for further studies to clarify their health impacts.