Micro- and Nanoplastics in the Atmosphere

Dear Colleagues,

Micro- and nanoplastics (MNPs), once thought to be confined to marine environments, are now recognized as emerging airborne pollutants with far-reaching impacts on both human health and the environment. While traditional marine microplastics (MMPs) are primarily within the 0.3–5 mm range, airborne microplastics (AMPs) are typically <100 µm and often go undetected due to their invisibility and measurement challenges.

In previous studies, the terms “airborne microplastics” and “atmospheric microplastics” have often been used interchangeably, leading to conceptual ambiguity. In this Special Issue, we draw a clear distinction between the two to better define their environmental contexts and transport characteristics. Airborne microplastics refer specifically to plastic particles suspended in the atmosphere, either as aerosols or within cloud droplets. In contrast, atmospheric microplastics is used as a broader term that also includes plastic particles in deposition media such as rainwater, snowfall, surface snow, and dry deposition. This distinction is essential for understanding their atmospheric behavior, transport mechanisms, and implications for climate and health. For simplicity, we refer to both categories as “AMPs,” with contextual clarification provided throughout the manuscript.

Furthermore, although their measurement is challenging, airborne nanoplastics, once taken into the body, can penetrate biological barriers and circulate throughout the body, thereby raising serious concerns.

Recent studies have revealed the presence of MNPs in human lungs, placenta, blood, sputum, and even the brain and cardiovascular tissues, suggesting their potential role in respiratory, neurological, and cardiovascular diseases. Furthermore, MNPs often carry hazardous additives (e.g., phthalates, flame retardants) and adsorb environmental toxins (e.g., PAHs, heavy metals), raising concerns about reproductive and carcinogenic risks. Among the pathways of exposure, inhalation is considered the dominant route, especially for particles smaller than 2.5 µm (PM₂.₅) and airborne nanoplastics (PM₁), which can reach the alveoli and enter systemic circulation.

Beyond health risks, AMNPs also influence climate and ecosystem dynamics. Under intense ultraviolet radiation, airborne plastic particles degrade rapidly and may emit greenhouse gases such as methane. Through surface aging and biofilm formation, AMNPs can become more hydrophilic, acting as cloud condensation or ice nuclei, potentially altering radiative balance and water cycles. Their long-range atmospheric transport further threatens fragile polar ecosystems.

Despite these concerns, standardized sampling, pretreatment, and analysis methods are lacking, hindering data comparability across studies. Additionally, the aerodynamic size distributions essential for modeling atmospheric behavior and health impacts remain poorly understood.

This Special Issue cordially invites novel contributions related to the source–transport–sink dynamics of AMNPs; interactions with terrestrial and marine systems; degradation and fragmentation mechanisms; methodological advancements in sampling and analysis; and health risk assessments and toxicological evaluations.

In addition, we warmly welcome Technical Notes from instrument manufacturers. Such contributions should be technical in nature, strictly non-promotional, and adhere to rigorous academic standards. We believe that including insights from the industry will be highly valuable in bridging research and practical applications, thereby fostering stronger collaborations between academia and the industrial sector.

We hope this collection will foster interdisciplinary collaboration and stimulate advances toward global standardization and risk mitigation of airborne plastic pollution.

Prof. Dr. Hiroshi Okochi
Prof. Dr. Yasuhiro Ishihara
Dr. Masaki Takeuchi
Dr. Mizuo Kajino
Guest Editors

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• airborne microplastics
• airborne nanoplastics
• sampling and analysis methods
• health risk
• climate impact