Isolation and characterization of microplastics from the human respiratory system: Sputum, broncho-alveolar lavage fluid, and pleural fluid simultaneously.

Microplastics (MPs) are emerging pollutants found in all ecosystems. While extensive research has focused on MP pollution across ecosystems, investigating their effect on the human body is still in its early stages. This study, conducted for the first time in Iran, specifically investigates MPs in the respiratory system, including sputum, broncho-alveolar lavage fluid (BALF), and pleural fluid. In this study, 34 patients participated after signing the consent form. Professional physicians collected 13 sputum samples, 11 BALF samples, and 10 pleural fluid samples. Patients' demographic information, lifestyle, occupation, exposed environment, and type of disease were evaluated through a questionnaire. The combination of digestion techniques, density separation, observation, Micro-Raman, and SEM/EDS analysis was performed to recognize MPs. The study results confirmed the presence of MPs in the respiratory system of all participants. MPs abundance in sputum, BALF, and pleural fluid varied between 156 and 468, 28-133, and 21-210 particles/100 mL, respectively. Generally, 22 types of MPs were identified and polyester (62-72%) was predominant. Fiber-shaped MPs were dominant in sputum (77%) and BALF (70%), and fragment-shaped in pleural fluid (63%). Particles <100 μm were the most abundant in all samples [in sputum (75.9%), BALF (50%), and pleural fluid (94.4%)]. Sampling type, occupational exposure, smoking, exposure to cigarette smoke, and wearing masks have affected the abundance of MPs (P < 0.05). Also, the shape and size of MPs affect their deposition in the respiratory system (P < 0.05). Hence, minimizing exposure to MPs is essential for safeguarding the environment and human health.