Micro- and nano-plastics in the global cryosphere: sources, transport, distribution, and impacts

Micro- and nano-plastics (MNPs) are persistent contaminants now detected across the global cryosphere, including alpine snow, Himalayan glaciers, Arctic sea ice, and Antarctic snow. This review synthesises evidence from 2010-2026 on occurrence, sources, transport pathways, and hazard-relevant impacts of MNPs in snow and ice systems. Current observations indicate that atmospheric deposition is the dominant delivery route to remote cryospheric regions, supported by trajectory analyses and deposition measurements from polar and high-mountain sites. Ocean circulation and sea-ice processes provide additional pathways and temporary storage. Reported concentrations and polymer profiles vary widely among regions and studies, reflecting differences in sampling design, contamination control, and analytical detection limits. The cryosphere functions both as a sink and a delayed secondary source: seasonal and long-term melt can remobilise historically stored particles to downstream aquatic ecosystems. Emerging evidence indicates potential effects on food webs and snow/ice albedo. Priority needs include harmonised methods, improved nanoplastic quantification, long-term monitoring, and integrated cryosphere-plastic mass-balance modelling to strengthen environmental risk assessment.