MicroRNA expression in response to environmental hazards: Implications for health

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression post-transcriptionally and are increasingly recognized as sensitive biomarkers of environmental exposure. This review explores how various environmental hazards-including radiation, air pollutants, heavy metals, pesticides, phthalates, and pathogens-alter both cellular and circulating miRNA expression, influencing phenotypic plasticity and contributing to disease development. Environmental hazards can induce epigenetic modifications in miRNA profiles, disrupting key biological processes such as inflammation, oxidative stress, apoptosis, and DNA repair. These alterations are associated with a wide range of diseases. The review outlines miRNA biogenesis, function, and extracellular transport, highlighting their stability and tissue specificity as biomarkers of exposure and disease. It also examines the complexity of exposure-specific miRNA signatures, shaped by factors such as genetic background, co-exposures, and exposure duration, and discusses current challenges in their validation and clinical application. Overall, this review underscores the pivotal role of miRNAs in cellular responses to environmental hazards and their potential as diagnostic and therapeutic tools, with broad implications for environmental health and disease prevention.