Inhalation of particulate and emissions from 3 dimensional (3D) printers: Effects on the olfactory bulb (OB) and hypothalamic‐pituitary‐endocrine axes

Abstract

There is increasing concern regarding the potential health effects associated with exposure to plastic nanoparticles and the chemicals released when plastic is heated or dissolved in water. Although exposure to plastic particles and their composite chemicals can be generated by a number of different processes, 3D printers used in manufacturing, schools and homes, are sources of fumes and particulate that humans are exposed to. This study examined whether inhalation of particulate and fumes generated during 3D printing with polycarbonate (PC) affects the OB and neuroendocrine system, and if there is a dose‐response relationship between exposure levels and measures of cell function. Methods Male rats (n= 6/group, 200 – 250 g at arrival) were exposed to filtered air, or black PC particulate and fumes generated by 3 desktop 3D‐printers (exposure was 4 h/day). The 4h average particulate concentration delivered to the animals breathing space was 500 µg/m3. Animals were exposed 4 days/week until the specified number of days of exposure (1, 4, 8, 15 or 30) had been reached. The morning after the last exposure, animals were euthanized, blood was collected and circulating hormone levels were measured in serum samples using ELISAs. The OB and brain were also collected, frozen, sectioned and stored at ‐80°C until processed for immunohistochemistry. Results In the OB, exposure to 3D‐emissions resulted in reductions in tyrosine hydroxylase (TH; rate limiting enzyme in dopamine synthesis) and glial derived neurotrophic factor immunolabeling. There were also reductions in myelin basic protein and cAMP nucleotide phosphatase staining, suggesting that there was myelin damage and dysfunction in the OB. In the hypothalamus, the major effects of exposure to 3D‐emissions were reductions in immunostaining for TH and glial fibrillary acidic protein, a marker of astrocyte activation. Changes in immunostaining in the OB suggest there is cellular dysfunction and potentially an alteration in the transmission of olfactory information to the brain. Changes in activity and morphology of astrocytes in the hypothalamus have been shown to affect the release of hormones, including those regulating reproductive and metabolic processes; In the current study, exposure to 3D‐emissions also resulted in changes in circulating concentrations of follicle stimulating hormone, and thyroid stimulating hormone. Conclusions Inhalation of PC particulate and/or fumes may act through olfactory pathways and affect neuroendocrine function. Although is not clear if these changes are the result of particulate matter interfering with various cellular and physiological processes, or due to endocrine disrupting bisphenols that are present in polycarbonate plastics, the results of this study are consistent with other experiments showing that exposure to PC particulate and the composite chemicals interfere with neuroendocrine processes that regulate reproduction and metabolism.

Cytotoxicity and Characterization of Ultrafine Particles from Desktop Three-Dimensional Printers with Multiple Filaments

“…While particles were consistently emitted during each test, a mean particle diameter of 50–60 nm confirmed the majority of the particles emitted were ultrafine particles. A marked increase in emissions from the 3D printer was observed as printing began with all filaments, consistent with the emissions profile outlined in earlier studies [ 1 , 2 , 3 , 4 , 5 , 6 ].…”

“…However, the generation of UFPs and NPs is not confined to these materials alone [ 1 , 2 , 3 ]. Several in vitro and in vivo studies have indicated that NPs can induce acute lung inflammation [ 4 , 5 , 6 , 7 ]. One human case report highlighted that a 28-year-old worker developed work-related asthma ten days after operating ten FDM 3D printers with ABS filaments in a 3000 cubic feet work zone [ 8 ].…”

“…Many studies indicate that cells exposed to an ALI are significantly more sensitive than those in submerged cultures during in vitro exposure to airborne UFPs. Various studies using in vitro cellular assays with human tumorigenic lung epithelial cells (A549) and in vivo mouse exposure have demonstrated toxic responses upon exposure to PLA- and ABS-emitted particles from an FDM 3D printer [ 6 ]. However, few studies to date have explored the emission of multiple filaments with the application of new open-source technology to 3D printers.…”

“…However, few studies to date have explored the emission of multiple filaments with the application of new open-source technology to 3D printers. Even fewer filament materials have been characterized for their toxicity, specifically ABS and PLA [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. Despite prior studies providing insights into the potential health effects of 3D printers, there remain crucial gaps in our understanding of emissions from these devices.…”