Micro- and Nanoplastic Toxicity in Upper Respiratory Tract: A Scoping Review

Objectives: To review the current literature findings dedicated to the toxicity of nano- and microplastics (NMPs) in the upper respiratory tract. Data Sources: PubMED, Cochrane Library and Embase databases. Review Methods: Three independent investigators conducted the literature search for the documentation and toxicity of NMP in the upper respiratory tract according to the PRISMA statements. Primary outcomes included NMP types, shape, density, sizes, the environment (air, mask wearing, plasticdevice), and the histological and physiological modifications associated with the deposit of NMP. Results: The scoping review included 12 studies (10 clinical, 2 experimental) with 356 human subjects. NMPs were detected in all samples, predominantly as fragments (10–500 μm), except in mask-wearers where fibers predominated. Polypropylene, polycarbonate, and polyurethane were the most common. Clinical studies showed higher NMP density in patients with nasal disorders with an increased permeability of mucosa (rhinosinusitis and allergic rhinitis) than in healthy controls. Mask wearing and nasal lavage devices contributed to NMP deposition. Experimental studies demonstrated NMP cellular internalization with potential physiological disruption, including oxidative stress, autophagy dysfunction, and respiratory microbiome alterations. There was substantial heterogeneity across studies for NMP detection methods. Conclusions: The current clinical and experimental studies demonstrate that both exposed and unexposed humans have nasal NMP detected in their nasal tissues and fluids. Mask wearing and the use of old plastic nasal lavage devices can contribute to this deposition. While experimental studies suggest changes in tissue and cell physiology, the toxicity of NMP in nasal tissue remains poorly investigated and has not been conclusively demonstrated.