Characteristics, sources, exposure, and health effects of atmospheric microplastics: a review of advances from 2021 to 2025.

Atmospheric microplastics (MPs) have emerged as ubiquitous environmental pollutants of global concern, with potential risks to ecosystems and human health. This review synthesizes 161 peer‑reviewed articles published between 2021 and 2025, providing a critical assessment of sampling and detection methodologies, physicochemical characteristics, spatiotemporal distribution patterns, human exposure pathways, and health risks. Research indicates that MPs primarily originate from textile fiber release, plastic degradation, and industrial emissions, with fibers and fragments as dominant morphologies and polymer compositions showing distinct regional variations. Distribution patterns differ markedly between indoor and outdoor environments, coastal and inland areas, and dry and wet seasons, regulated by climate, human activities, and land use types. Human exposure occurs mainly via inhalation and dermal contact, with particles < 10 μm readily penetrating respiratory barriers. Notably, this review reveals a systematic discrepancy of 1-2 orders of magnitude between active and passive sampling results, demonstrates that indoor and outdoor concentrations are significantly influenced by ventilation conditions, localized point sources, and environmental parameters, and elucidates the molecular mechanisms of key signaling pathways including oxidative stress and inflammatory responses. Current research still faces limitations in method standardization, detection of small‑sized (nanoscale) particles, and understanding long‑term exposure toxicological mechanisms. Future efforts should focus on advancing cross‑regional, multi‑media collaborative monitoring, developing highly sensitive detection technologies, investigating transport, transformation, and health hazard mechanisms, and establishing health risk‑based exposure limit standards to provide scientific support for targeted pollution prevention and control.