Microplastics and cancer.

The pervasive spread of microplastics (MPs) in the environment (including air, water, and food) has raised concerns regarding human health. These pollutants have been detected in various human tissues such as lungs, colon, blood, placenta, tumors, and body fluids. MPs may act as vectors for toxic and carcinogenic substances, including heavy metals and persistent organic pollutants. They can induce oxidative stress, inflammation, and genotoxicity, thereby altering cellular and metabolic processes, mechanisms implicated in cancer pathogenesis. Recent studies highlight the presence of MPs in human tumor tissues, often at higher concentrations than in adjacent healthy tissues. A relation between MPs exposure and increased risk of colorectal cancer has been observed, where MPs may promote lipid absorption and suppress pyroptosis, contributing to chemoresistance. In the lung, metal-microplastic complexes have been associated with reduced overall survival and disease-specific survival in patients with lung adenocarcinoma. MPs may influence tumor progression, metastasis, and drug resistance. While oncogenic mechanisms are biologically plausible and supported by experimental studies, no clinical nor epidemiological evidence supporting the causal association between MPs and cancer is available.