The misuse and improper disposal of plastic products have led to a series of environmental issues, with Microplastics (MPs) gaining widespread attention this year. Microplastics refer to small plastic particles with dimensions ranging from 1 μm to 5 mm, exhibiting various shapes such as beads, particles, fibers, sheets, and fragments. In the natural environment, micrometer-sized plastic particles can further degrade into plastic particles ranging from 1 nanometer to 100 nanometers, known as Nanoplastics (NPs). The sources of microplastics include primary and secondary origins, namely personal care products, cosmetics, pharmaceutical carriers, and plastic debris lingering in the environment. They undergo degradation through physical processes (mechanical abrasion), chemical processes (UV radiation and temperature), and biological processes (microbial degradation).

There is still a gap in research regarding the potential health risks of microplastics to the human body, including a lack of sufficient quantitative assessments of microplastic toxicity and human exposure data. The impact of microplastics on human health remains inconclusive. In studies investigating the effects of microplastics on the human body, there is still a gap in toxicity research due to the potential hazards and ethical considerations associated with microplastics. Current research on humans primarily focuses on the detection of microplastics in human tissues, body surfaces, or feces, with limited in-depth studies available.

To further explore the toxicity of microplastics, recent research has predominantly included in vitro and in vivo studies, utilizing cell experiments, animal experiments, and organ model experiments. A substantial amount of research has been conducted, leading to a series of significant findings. This article compiles and reviews recent studies on human exposure to microplastics, in vitro experiments, rodent experiments, and other studies related to human toxicity. It discusses the current limitations in this field of research and suggests future directions, aiming to provide assistance and a foundation for further investigating the potential harm of microplastics to human health.

Summarized relevant data from studies on human exposure to microplastics, including parameters such as the locations of microplastic exposure, types of microplastics, concentrations, etc., and briefly documented in Table 1.

Cell-level studies contribute to a better understanding of the toxicity of microplastics and help identify the mechanisms of adverse effects. This section primarily focuses on in vitro experiments using human cells and rodent cells as experimental materials. Table 2 provides a brief summary of the microplastic parameters, exposure data, and toxic effects obtained from these studies. Based on these experiments, the cell toxicity of microplastics and their impact on different types of cells are summarized, allowing for an analysis of the harm caused by microplastics at the cellular level. It is worth noting that, in order to understand cell toxicity, the concentrations of microplastics in in vitro experiments are often much higher than those found in the real in vivo environment. This may not accurately reflect the cytotoxic effects at low doses.

Table 3 provides a brief summary of some recent studies on microplastics in the bodies of mice and rats. Experimental data, including the types of microplastics, exposure doses, and exposure durations, are recorded, and significant toxic effects observed in the studies are briefly summarized. It is important to note that the exposure concentrations used in the experiments are much higher than those encountered in real-life situations. In studies using mice and rats as animal models, major toxic effects are primarily observed in the digestive, nervous, respiratory, reproductive, and cardiovascular systems.

This article provides a comprehensive overview of recent research on human exposure to microplastics, in vitro cell experiments, rodent experiments, and in vitro model experiments. It thoroughly analyzes the potential toxic effects of microplastics on the human body. The potential toxic processes of microplastics on the human body are outlined as follows: firstly, microplastics enter the human body through three exposure routes—by inhalation through the respiratory system, ingestion through the digestive tract, and contact with the skin. Some microplastics are directly released, while others, varying in size and properties, diffuse into different tissues of the human body. Microplastics induce cell toxicity by causing oxidative stress, cell membrane and organelle damage, immune reactions, genetic toxicity, and other toxic effects. In turn, this affects tissues and organs of the digestive, nervous, respiratory, reproductive, and cardiovascular systems, leading to diseases and impacting human health.