Interfacial transport and synergistic toxicity of soil-borne micro- and nanoplastics: Mechanistic insights from plants to mammals

Soil-borne micro- and nanoplastics (MNPs) have emerged as pervasive terrestrial pollutants that intricately interact across soil-plant-animal interfaces. Yet, the mechanisms enabling their translocation across biological barriers and subsequent systemic toxicity remain elusive. This review consolidates current understanding of their physicochemical behaviors, interfacial transport pathways, and multidimensional toxic effects of soil-borne MNPs, and examines their synergistic interactions with co-occurring contaminants. MNPs can bypass plant rhizosphere defenses via endocytosis, apoplastic transport, and crack entry, ultimately accumulating in aerial tissues. In soil mesofauna, MNP ingestion causes physical injury and oxidative stress, though partial biodegradation may occur through host-microbe cooperation. In mammals, MNPs penetrate intestinal barriers, enter systemic circulation, and provoke inflammatory and metabolic disorders that disrupt digestive, immune, and reproductive systems. Moreover, MNPs act as vectors for co-occurring pollutants such as heavy metals and antibiotics, amplifying ecological and health hazards through synergistic toxicities. Collectively, this review provides an integrated framework for understanding the environmental behaviors, biological interactions, and combined toxicities of soil-borne MNPs, and identifies critical directions for future research and risk assessment.