Indoor magnetic particles: characteristics, sources and health implications – a review

Magnetic nanoparticles are recognized components of air pollution with potential health impacts. While outdoor sources and effects have been studied, the characteristics, origins, and health implications of magnetic particles indoors remain less understood. Here we review current literature on indoor magnetic particles, analyzing their physicochemical properties, sources and potential health risks inferred from related environmental studies. Although source-attribution studies show progress for outdoor emissions, only limited evidence exists for indoor sources, with combustion activities, cigarette smoke, and toner-based printing identified as contributors. Current data indicate that exogenous magnetic nanoparticles can be internalized and translocated across multiple organs, and several toxicity pathways have been described. However, key uncertainties persist regarding dose–response relationships, toxicologically meaningful magnetic metrics, and exposure thresholds. These findings highlight the need for integrated research to better characterize indoor magnetic nanoparticles, differentiate indoor and outdoor sources, and clarify their role in chronic health outcomes associated with air pollution.