Whole Body Inhalation of Polycarbonate Emissions Generated During 3D-Printing Process Alters Metabolism and Redox Status in Rat Liver

Details

• Personal Author:
  Bodas, M. ; Guppi, S. ; Mandler, W. Kyle ; McKinney, Walter G. ; Knepp, Alycia K. ; Keeley, Sarah ; Battelli, Lori A. ; Qian, Yong ; Stueckle, Todd A.
• Description:
  Background and Purpose: Three-dimensional printing (3D Printing), i.e. additive manufacturing, is a burgeoning technology which has applications in various industries, such as healthcare, education, consumer goods, and personal care products. It has also found great utility in industrial manufacturing applications in the automobile, aerospace, and construction sectors. Fused filament fabrication (FFF) is a widely used 3D printing method that works by melting and extruding plastic filament layer by layer. Polycarbonate (PC) filament-based FFF process is known to release ultrafine particles (UFPs) and volatile organic compounds (VOCs), which might pose an inhalation hazard. Recent studies from our group have found that rats exposed to inhaled 3D printer emissions at a concentration of 2.5 mg/m3 using PC filament demonstrated systemic adverse effects on various components of the neuroendocrine system, but no significant pulmonary toxicity. The present study was designed to examine whether whole body inhalation of emissions generated during the PC FFF printing process leads to metabolic and redox changes in the liver. Methods: Six to seven weeks old male Sprague-Dawley rats, each weighing about 200-225 grams, were purchased from Hilltop Lab Animals and housed in ventilated polycarbonate cages. The rats were housed in a facility that provided a controlled environment with HEPA-filtered air and acclimated for at least seven days before study initiation. Rats were fed a standard irradiated diet and filtered tap water ad libitum. The study protocol was reviewed and approved by the CDC-Morgantown Institutional Animal Care and Use Committee, which is accredited by AAALAC International. Whole body inhalation exposure of rats was performed using an in-house 3D-printer emissions inhalation exposure system. Briefly, rats were exposed to either filtered air (air control group) or 3D printer-PC filament emissions (2.5 mg/m3, 63 nm mean particle electric mobility diameter; 3D-PC group), for a time course of 1, 4, 8, 15 and 30 days (4 hours per day; 4 days per week). Twenty-four hours after the last exposure, rats were euthanized by intraperitoneal injection of pentobarbital. Liver tissue was harvested and stored in RNAlater for quantitative real-time PCR (qPCR) or immediately frozen at -80 degrees C for biochemical analyses. Total RNA was used to perform qPCR to quantify the changes in expression of genes related to inflammation, oxidative stress, and metabmetabolism. Homogenized liver tissue lysates were prepared and used to evaluate changes in markers of redox status including reduced and oxidized glutathione, glutathione S-transferase (GST), and lipid peroxidation. Differences between treatments were assessed using 2-way analysis of variance followed by post-hoc student t-tests. Nonparametric data were compared using Wilcoxon multi-comparison tests. Results: The genes selected for qPCR were grouped into five categories, namely (1) inflammation, (2) oxidative stress, (3) glucose/glycogen metabolism, (4) fatty acid metabolism, and (5) sterol metabolism. The data suggests that Day 1 exposed rats had elevated expression of genes related to inflammation (e.g. TNFa), glucose (e.g. Slc2a3), fatty acid (e.g. PPARa/y, Thrsp), and sterol metabolism compared to air controls. The rats exposed for 8 days showed comparable levels of gene expression (or suppression in some genes, e.g. Scd1) in fatty acid and sterol metabolism-related genes as compared to air controls, while genes related to inflammation remained elevated. In rats exposed for 30 days, the expression of IL-1â remained elevated while other inflammation-related genes were similar to air controls. Moreover, Thrsp, Hmgcs1, and Hmgcr still retained elevated levels while all other genes showed no difference from air controls. GST activity significantly increased 5-fold for all Day 4 animals compared to Day 1 animals. At Day 8 PC-exposed animals had significantly lower GST activity as compared to air controls. All animals in remaining exposure days showed similar GST activity compared to Day 1 animals. Total glutathione levels in all animals at Day 4 were significantly lower than Day 1 animals, while PC-exposed animals at Day 8 had significantly lower total glutathione than time-matched air controls. All remaining time points and treatments possessed comparable total glutathione as Day 4 animals. Reduced glutathione showed an exposure time-dependent decrease starting at Day 4. By Day 8 reduced glutathione had decreased by 10-fold in both PC and air control animals and remained low in all later time points. Lipid peroxidation did not change in all animals with increasing exposure time until a significant increase in all Day 15 and 30 animals. Conclusions: Collectively, whole body PC FFF exposure at 2.5 mg/m3 induced rat liver biomarkers associated with inflammation, oxidative stress, glucose, fatty acid, and sterol metabolism, which partially resolved with repeated exposure over time. PC exposure depleted total glutathione stores and subsequent GST activity faster than air control animals over 8 days of repeated exposure, potentially subjecting long term exposed animals to xenobiotic-induced metabolic changes, damage, and redox stress. Description provided by NIOSH
• Subjects:
  • Liver
  • Occupational Health
  • Polycarbonates
  • Printing, Three-Dimensional
  • Rats
  • Respiratory System
  • Safety
• Keywords:
  • Additive manufacturing; Three dimensional printing; 3D printing; Inhalation; Laboratory animals; Metabolic effects; Liver function
• Source:
  Toxicologist 2025 Mar; 204(S1):253
• ISSN:
  1096-6080
• Document Type:
  Text
• Genre:
  Abstract or Summary
• Place as Subject:
  Philadelphia Region OSHA ; West Virginia
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  HELD - Health Effects Laboratory Division
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  2 pdf pages
• Volume:
  204
• NIOSHTIC Number:
  nn:20071579
• CAS Registry Number:
  • Polycarbonates (CAS RN 25766-59-0)
• Federal Fiscal Year:
  2025
• NORA Priority Area:
  Manufacturing
• Peer Reviewed:
  False
• Download URL:
  https://stacks.cdc.gov/view/cdc/259354/cdc_259354_DS1.pdf
• File Type:
  [PDF - 260.08 KB]
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:704ac964c0d966c825794b64401901b7e4bab2c6effafbddfb58a74987d0496bc0253573d37dba1f095e4d8fb4fcf96e419e53f233fca7a1e932045b57008206