P-487 Investigation of Lung Disorder by Microplastic; Short-Term Inhalation Exposure of Polypropylene in Rats

Background Workers who handle plastics and workers engaged in waste disposal may be exposed to microplastics through the respiratory tract. However, there have been few reports on the biological effects of microplastics in the lungs. In this study, we conducted a short-term inhalation exposure study using rats to evaluate lung disorders with microplastics. Methods Inhalation exposure was conducted using 8-week-old male Fischer 344 rats at a low concentration of 2 mg/m3 and a high concentration of 10 mg/m3 of polypropylene fine powder for 6 hours a day, 5 days a week for 4 weeks. Rats were dissected at 3 days, 1 month, and 3 months after inhalation exposure, and bronchoalveolar lavage fluid (BALF) and lung tissue were collected to analyze lung inflammation and lung injury. Results An increase in the percentage of neutrophils in BALF was observed at both low and high concentrations 3 days after exposure, and the observation of lung histopathology specimens showed an influx of inflammatory cells in the alveolar space. In the high-concentration group, the number of neutrophils in BALF increased even at 1 month, and lactate dehydrogenase activity, an indicator of lung injury, also showed a sustained increase up to 1 month. Discussion/Conclusion In this study, a short-term inhalation exposure to microplastics was conducted. The results showed inflammatory changes in a dose-dependent manner, and inflammatory changes were observed at the exposure of 2 mg/m3 after 3 days of exposure but were very mild. These suggest that the exposure concentration of 2 mg/m3 is close to the threshold for acute effects.