Microplastics and colorectal cancer: presence in human colorectal tissues and associations with tumor biology

The incidence and death rates of colorectal cancer (CRC), one of the world’s largest health issues, are rising. These days, environmental contaminants such microplastics (MPs) are believed to play a role in the development of colorectal cancer. Small plastic particles (less than 5 mm) are referred to as MPs because they are persistent and may build up in human tissues, raising questions about their potential involvement in tumour biology. The objective is to systematically assess the prevalence of microplastics found in human colorectal membranes and their connections to biological processes and tumour type indicators in colorectal cancer. A systematic review was carried out using the Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA). Peer-reviewed study sources published between January 2019 and December 2025 were located in MEDLINE, EMBASE, Web of Science, and the Cochrane Library. The studies had to assess MPs in human colorectal tumours or surrounding tissues, as well as their associations with tumour biology, such as clinical, inflammatory, or molecular markers, according to the inclusion criteria. Two reviewers worked independently on the screening, selection, and data extraction processes. Thirteen papers make up the final qualitative synthesis, which is screened for full text and title/abstract. Study design, sample size, tissue type, MP detection techniques, polymer type, particle size, and tumour biology outcomes were among the data that were extracted. Particularly, MPs were detected in colon tissues, and their concentration was greater in tumour tissues than in nearby or control tissues. The most common polymers were polyethylene, polypropylene, and polystyrene, the majority of which were less than 100 μm. The advanced tumour stage, limited differentiation, elevated pro-inflammatory cytokine levels, signs of oxidative stress, disrupted immune infiltration, and disrupted epithelial barrier function were all associated with higher MP loads. According to mechanistic research, MPs can induce oxidative stress, inflammation, and immunological homeostasis, all of which can result in a pro-tumorigenic environment. MPs can affect the development of colorectal cancer (CRC) because they are found in human colorectal tissues and are preferentially accumulated in tumours. Multicenter studies with typical application are required to clarify causal processes and clinical consequences.