Micro (Nano)plastics Vitiation of Genetic Material: Systematic Review of Genotoxic Biomarkers and Model Bioindicators

Micro (nano)-plastics (MPs/NPs) are ubiquitously detected in human samples: stool, placenta, breastmilk, testes and semen, liver, lung, and blood, with their detailed toxicological profile still emerging. Numerous scientific studies are increasingly being conducted towards understanding possible deleterious effects of MPs/NPs on human, animal, plant, and environmental health. MPs/NPs rarely biodegrade, have small particle sizes, and are positively charged-features that make them dangerous to cells. They are capable of inducing oxidative stress, genotoxicity, immunological response, alteration in cellular membrane and cytoarchiture. The ability for MPs/NPs to induce DNA damage and genotoxicity may enhance genome instability, the hallmark of cancer and genetic disease syndrome. This review focused on determining the sensitivity of various biomarkers utilized to assess the DNA damage and genotoxicity potentials of MPs/NPs, the bioindicators used as models (invertebrates, vertebrates, cell lines/primary cells and plants), and the mechanisms of MPs/NPs-induced genotoxicity and DNA damage. The nature/type and size of the MP/NP polymers, concentration, and duration of exposure are determining factors considered in the DNA damage and genotoxicity assessment of MPs/NPs. Also, somatic and germ-line cells are susceptible to the genotoxic effects of MPs/NPs. Single and double DNA strand breaks assessed using the comet assay are the most used biomarker of DNA damage, while chromosome aberration is the least used. Others are sperm morphology assay, micronucleus assay, and toxicogenomics. The mechanisms of MPs/NPs-induced DNA damage include generation of free radicals and oxidative stress, induction of deleterious inflammatory cells, down-regulation of transcriptional genes related to apoptotic expressions, and increased DNA fragmentation in cells and tissues. Further studies are required to unequivocally confirm MPs/NPs as genotoxins, mutagens, and/or carcinogens.