Table 5.

Toxicity studies related to 3D printer generated emissions and 3D printed objects

Material	Study type	Experimental regimen	Toxicological implications (examples)	Reference
ABS, PLA	Human clinical exposure	1-hour exposure to 26 healthy adults (13 female and 13 male) with average age 25 years in a single-blinded, randomized, cross-over design with median ([25th; 75th percentiles]; min; max) average LDSAa (μm2/cm3) values of 81.0 ([47.1; 113]; 25.7; 358) for ABS and 7.2 ([4.8; 10]; 2.9; 17) for PLA; spirometry, questionnaire, FeNOb and urine sample immediately post exposure and nasal secretion, FeNO and urine sample at 2–3 h post exposure. Specific inflammatory cytokines were measured in nasal and 8-isoprostaglandin F2α (8-isoPGF2α) in urine samples.	Slight increase in FeNO suggesting possible eosinophilic inflammation in ABS exposed	(Gumperlein et al., 2018)
ABS and PLA	Human case report	28-year-old self-employed adult with a history of asthma in childhood reported respiratory symptoms 10 days after using printers	Respiratory problems, asthma demonstrated with MeCh challenge; symptom worse with ABS than PLA	(House et al., 2017)
Not specific	Self-reported health and occupational exposure survey	Questionnaire administered to 46 workers across 17 companies.	Working more than 40 h per week with 3D printers was significantly associated (P < 0.05) with having been given a respiratory-related diagnosis (asthma or allergic rhinitis).	(Chan et al., 2018)
Black ABS	In Vivo, Male, Sprague-Dawley rats	3-hour nose-only exposure 0.9 ± 0.1 mg/m3 mean aerodynamic diameter (ELPIc): 70 ± 2 nm	Microvascular dysfunction, elevated mean arterial pressure	(Stefaniak et al., 2017a)
ABS (2 different filaments), PLA, and Nylon	In Vivo, Male C57BL/6 mice	Single 50 μL intra-tracheal instillation Particle diameters estimated roughly from SEM images were 71 ± 20 nm (mean ± standard deviation) for “ABS d”, 106 ± 20 nm for “ABS c”, and 14 ± 25 nm for PLA. Concentrations varied by assay performed.	Strong inflammatory response, increase neutrophils number	(Zhang et al., 2019)
ABS	In Vivo, Male, Sprague-Dawley rats	Whole-body exposure for 4 h/day, 4 days/week and five exposure durations (1, 4, 8, 15, and 30 days) at 240 ± 90 mg/m3 average geometric mean particle mobility diameter of 85 nm and geometric standard deviation 1.6 nm.	Minimal and transient pulmonary toxicity: Increased cytokines (IFN-γ and IL-10)d in BALFe at days 1 and 4 post-exposure with peak of IL-10 on day 15; increased macrophages at day 15. Increased serum biomarkers of renal and hepatic function on day 1. No significant histopathology.	(Farcas et al., 2020)
ABS (2 different filaments), PLA, and Nylon	In Vitro epithelial cells (A549), rat alveolar macrophages (NR8383)	Submerged culture Particle diameters estimated roughly from SEM images were 71 ± 20 nm (mean ± standard deviation) for “ABS d”, 106 ± 20 nm for “ABS c”, and 14 ± 25 nm for PLA. Concentrations varied by assay performed; duration of incubation not provided.	Cell death, oxidative stress, inflammatory responses	(Zhang et al., 2019)
Black ABS, Black PC	In Vitro Human SAECf	Cells exposed as undiluted (0%), 25% dilution, and 50% dilution in serum-free SABM™, resulting in six doses for each filament type Mean particle sizes in cell culture medium were 201 ± 18 nm and 202 ± 8 nm for PC and ABS	24-hour post exposure increase in cytotoxicity, oxidative stress, apoptosis, necrosis, and production of pro-inflammatory cytokines and chemokines	(Farcas et al., 2019)
Multiple 3D printed or molded materials	In Vitro, bovine embryo and ER activation in BG1Luc4E2 cell line	Submerged co-cultured with leachate from printed or molded parts for 20–22 h	Inhibited embryo cleavage	(de Almeida Monteiro Melo Ferraz et al., 2018)
SLA-3D printed material	In Vivo Zebrafish	Fish embryo toxicity assays performed with wild type, double transgenic and single transgenic lines incubated with leachate for 48 h at various dilutions	Developmental toxicity correlated with in situ generation of reactive oxygen species (ROS),g an increase in lipid peroxidation and protein carbonylation markers and enhanced activity of superoxide dismutase (SOD)h and glutathione-S-transferase (GST)i in embryos exposed to concentrations as low as 20% v/v for plastic extracts; ROS- induced cellular damage led to induction of caspase-dependent apoptosis; significantly decreased acetylcholinesterase (AChE)j activity with lack of any CNS-specific apoptotic phenotypes as well as lack of changes in motor neuron density, axonal growth, muscle segment integrity or presence of myoseptal defects	(Walpitagama et al., 2019)

^a.LDSA - Lung deposited surface area.

^b.FeNO - fractional exhaled nitric oxide; PGF2α Prostaglandin 2α.

^c.ELPI- Electrical Low-Pressure Impactor.

^d.(IFN-γ and IL-10)- Interferon gamma and interleukin 10.

^e.BALF-Broncho-alveolar lavage fluid.

^f.SAEC-Small airway epithelial cells.

^g.ROS- reactive oxygen species.

^h.SOD- superoxide dismutase.

^i.GST- glutathione-S-transferase.

^j.AChE- acetylcholinesterase.