Microplastics in the Human Body: Exposure, Detection, and Risk of Carcinogenesis: A State-of-the-Art Review

Abstract

Background: Humans cannot avoid plastic exposure due to its ubiquitous presence in the natural environment. The waste generated is poorly biodegradable and exists in the form of MPs, which can enter the human body primarily through the digestive tract, respiratory tract, or damaged skin and accumulate in various tissues by crossing biological membrane barriers. There is an increasing amount of research on the health effects of MPs. Most literature reports focus on the impact of plastics on the respiratory, digestive, reproductive, hormonal, nervous, and immune systems, as well as the metabolic effects of MPs accumulation leading to epidemics of obesity, diabetes, hypertension, and non-alcoholic fatty liver disease. MPs, as xenobiotics, undergo ADMET processes in the body, i.e., absorption, distribution, metabolism, and excretion, which are not fully understood. Of particular concern are the carcinogenic chemicals added to plastics during manufacturing or adsorbed from the environment, such as chlorinated paraffins, phthalates, phenols, and bisphenols, which can be released when absorbed by the body. The continuous increase in NMP exposure has accelerated during the SARS-CoV-2 pandemic when there was a need to use single-use plastic products in daily life. Therefore, there is an urgent need to diagnose problems related to the health effects of MP exposure and detection. Methods: We collected eligible publications mainly from PubMed published between 2017 and 2024. Results: In this review, we summarize the current knowledge on potential sources and routes of exposure, translocation pathways, identification methods, and carcinogenic potential confirmed by in vitro and in vivo studies. Additionally, we discuss the limitations of studies such as contamination during sample preparation and instrumental limitations constraints affecting imaging quality and MPs detection sensitivity. Conclusions: The assessment of MP content in samples should be performed according to the appropriate procedure and analytical technique to ensure Quality and Control (QA/QC). It was confirmed that MPs can be absorbed and accumulated in distant tissues, leading to an inflammatory response and initiation of signaling pathways responsible for malignant transformation.

Keywords: carcinogenesis; micro/nanoplastics; microplastic detection; microplastic exposure; microplastic pollution; microplastic toxicity.

Figure 1

Scheme showing the subsequent steps of the analysis of MPs in human samples.

Figure 2

The health impacts of NMPs. The initiation of carcinogenesis is generated by abnormal gene expression and the influence of NMPs on various signaling pathways via cytokines (AP-1), interleukin-1 family: IL-1, IL-6, IL-8, tumor necrosis factor α (TNF-α), interferons (IFNs), Toll-like receptor 4 (TLR4), T helper 17 cell (Th17), suppressor T cells (Treg cells), interferon regulatory factors (IRF), activator protein 1 (AP-1) produced by inflammatory cells or via activation of intracellular kinases, i.e., the mammalian mitogen-activated protein kinase (MAPK) family: Extracellular signal-regulated kinases (ERKs), c-Jun N-terminal kinases (JNKs), and p38 mitogen-activated protein kinases (p38s), which dysregulate proliferation, differentiation, apoptosis, and stress response.

Figure 3

KEGG map of pathways in cancer (05200 Pathways in cancer) [380]. Rectangular boxes indicate gene enzymes. Genes marked in pink are identified to be up- or down-regulated by MPs additives [380].