The Urban Exposome: Genomic, Epigenomic, and Evolutionary Consequences Across Species

Urban environments bring together air pollution, heat, noise, artificial light, changing dietary habits, and inequalities in access to green space. This narrative review examines how these exposures relate to molecular changes in humans, microbial communities, and wildlife, presenting an interspecies urban genomics framework. Findings from human studies mainly concern changes in gene regulation, development, and health across the life course. Responses in microbial communities include shifts in composition and horizontal gene transfer. In some wildlife populations, genetic and experimental evidence support heritable adaptation across generations. Oxidative stress, DNA damage, inflammation, circadian disruption, and epigenetic regulation provide recurring mechanistic links, although their roles vary by exposure and species. Because most human studies are observational, the molecular associations identified do not, on their own, establish that a particular exposure causes disease. A better understanding of these relationships requires longitudinal cohorts, intervention studies, representative data from low- and middle-income countries, and coordinated monitoring across species. Urbanization also provides health benefits through sanitation, access to services, and well-designed infrastructure. This framework aims to guide research and help policymakers assess these risks and benefits together. Further validation is needed before molecular biomarkers can be used in clinical practice and urban planning.