102 Inhalation of nano and micro polyethylene particles induces higher lung inflammation in women compared to men

Micro- and nano-sized polyethylene plastics (PE-MPs and PE-NPs) are emerging as potential risk factors for pulmonary disease and risk assessment. This study aimed to characterize the toxicity of PE-MPs and PE-NPs after 13 wk of intratracheal instillation in Sprague-Dawley (SD) rats and to assess the reversibility of any effects during a 4-week recovery period. Exposure levels for PE-MPs and PE-NPs were set at 0, 40, 80, and 120 μg per head once a week. The results indicated that the treatment administration resulted in observable lung alterations. Inflammatory cells were present in the perivascular and peribronchiolar regions in both sexes at ≥40 μg per head in the PE-MPs and PE-NPs-treated groups, indicating a toxicological change. Additionally, thickened alveolar ducts and alveolar epithelial hyperplasia were noted in males at 120 μg per head PE-MPs, in males at ≥80 μg per head PE-NPs, and in females at ≥40 μg per head PE-MPs and PE-NPs-treated groups. Interestingly, when instilled repeatedly with both sizes of polyethylene particles, IL-1β and TNF-α secretion was significantly enhanced in female rats compared to male rats. At the same time, the pulmonary level of IL-6 increased more clearly in male rats than in female rats. The pulmonary level of C-reactive protein, a marker for acute inflammation, was increased in all treated groups. These findings suggest that the no-observed-adverse-effect level (NOAEL) for PE-MPs and PE-NPs is below 40 μg per head for both sexes. However, the toxicological data for PE-MPs and PE-NPs remain insufficient to confirm their safety, and further research is necessary to evaluate their potential risks to human health.