The dark matter in water, air and land: from microplastic to invisible nanoplastics

Microplastic is well known and has been the subject of many review articles. In recent years, an increasing number of reports have documented the presence of nanoplastics-plastic particles smaller than 1 µm-in various environments, from the ocean to the human brain. In this article, I focus on nanoparticles and what we do and do not understand about their effects on our health. After an introduction to nanoplastics and their size relative to a single polymer chain, the degradation process that produces nanoplastics, similar to microplastics, is briefly summarized. Due to their high surface area, nanoplastics can behave differently in solution because they tend to aggregate. After reviewing the presence of microplastics and nanoplastics in humans, insights from the established field of nanomedicine are used to explore how nanoplastics may enter the bloodstream and reach the brain. This also includes the topic of protein corona formation, which influences the fate of nanoplastics in the body. Finally, a brief summary on the impact of plastic particles on health is provided, focusing on reports comparing nano- and microplastics. This article concludes with how materials scientists and chemists can contribute to addressing the rising plastic pollution problem.