Background <p>Microplastics (MP; particles &lt; 5&#xa0;mm) have emerged as contaminants of growing ecotoxicological concern in aquatic environments and are a potential threat to human health. Notably, the use of MPs markedly increased during and after the corona virus disease 2019 pandemic due to the heightened emphasis on personal hygiene and sanitation.</p> Objectives <p>Although research on MPs has intensified globally, conflicting results have led to ongoing debates and uncertainty regarding the effects of MPs on human organs and overall health.</p> Results <p>Smaller particles are of particular concern because of their increased toxicity and ability to penetrate deeply into human tissues and organs. Additionally, irregularly shaped and fragmented MPs, which are prevalent in natural environments, pose greater risks. Irregular shapes facilitate tissue penetration and promote oxidative stress, thereby exacerbating toxic effects.</p> Conclusions <p>To better understand the effects of MPs on the human body, their effects on each organ or disease state should be categorized according to MP type, size, and shape. This approach provides valuable insights into the relationship between MPs and human health, thereby enabling informed discussions on the consumption and application of plastic products to promote future healthier living.</p> Purpose of the review <p>In this review, we discuss how MP size and shape influences their effects on human health. Furthermore, we categorize the most commonly used plastics as polystyrene, polypropylene, and polyethylene, thereby highlighting the specific effects of MPs derived from each category.</p>