Assessment of pulmonary toxicity of inhaled polycarbonate 3D printer emissions in rats

This study investigated the potential pulmonary toxicity of polycarbonate (PC) emissions from fused filament fabrication (FFF) three-dimensional printing (3DP) via inhalation in Sprague Dawley rats. Previously, our results demonstrated no significant pulmonary effects following exposure to a 0.5 mg/m³ PC. A new exposure apparatus was developed that exposed animals at a concentration of 2.5 mg/m³. Sixty rats were randomized into control (filtered air) and exposure groups (<i>n</i> = 30/group). Each group was further divided into five subgroups (<i>n</i> = 6/subgroup) with exposure durations of 1, 4, 8, 15, or 30 days (4 hr/day, 4 days/week). Following a 24-hr post-exposure period, body weight was measured, and blood samples were collected for hematological and biochemical analysis. Bronchoalveolar lavage fluid (BALF) was obtained from the right lung for cytology. The left lung and head/nasal tissues were preserved for histopathological evaluation. Lung deposition was estimated using the Multiple-Path Particle Dosimetry model, electron microscopy, and enhanced darkfield microscopy. In addition, filter samples were collected to measure bisphenol A. Exposure resulted in an estimated deposition of 0.28 µg/day within the alveoli and small airways. Microscopy indicated limited evidence of macrophage uptake. No significant changes were observed in BALF cell counts, lactate dehydrogenase activity, or hematological parameters. BALF levels of tissue inhibitor of metalloproteinases-1 and protein were elevated in the 30-day exposure group, although histopathology revealed no exposure-related changes in the lungs. In conclusion, this study found no marked pulmonary inflammation or toxicity in rats exposed to 2.5 mg/m³ of PC 3D printing emissions for up to 30 days (4 hr/day).