The availability of low cost desk-top size three dimensional (3D) printers has increased due to easy availability and their ability to customize object printing to exact specifications based on CAD drawings. This availability for use in non-industrial settings (offices and homes) may create an environment where poor ventilation and limited health and safety controls exist; thus, there may be an increased risk for adverse health effects, particularly if the user is in close proximity to emissions, the zone of highest exposure. While 3D printers are becoming more accessible and widely used in professional and personal applications, studies depicting the potential health effects and indoor air quality implications are still emerging. When reviewing regulatory limits on particle exposure, the United States Occupational Safety & Health Administration (OSHA) defines nuisance dust, Particulates Not Otherwise Regulated (PNOR), into two categories: total dust (Permissible Exposure Limit (PEL), 15 mg/m 3 as 8-hour TWA) and respirable dust (50% cut point of 4 microns) (PEL 5 mg/m 3 as 8-hour TWA). 1 These classifications are mass based and apply to particulates that do not have a specific OSHA regulation. The United States Environmental Protection Agency has promulgated the National Ambient Air Quality Standards for PM 2.5 (35 ug/m 3 of particulate matter less than 2.5 microns, measured as a 24 hour average). 2Initial studies of 3D printers classified particulate emissions primarily in the ultrafine range. 3,4,5 Ultrafine particles (UFD) are defined as those with a diameter less than 0.1 microns. Ultrafine particles contribute negligibly to PM2.5 mass but contribute significantly to the particle number concentration. 6 Therefore mass based measurements may not be appropriate to measure exposure, and subsequent exposure assessment to 3D printer emissions.Ultrafine particulate air pollution is associated with a variety of adverse health effects in the scientific literature. 7,8 Ultrafine particles cause more respiratory system inflammation than larger particles in rodent studies and UFP surface properties greatly influence toxicity. 8 Mass based measurements do not consider number count or surface properties of particulates. Further, epidemiological studies have associated increased
An eddy diffusion model using data from a desktop three-dimensioanl (3D) printer was developed under laboratory conditions and then coupled with Monte Carlo analysis to estimate the potential range of particulate concentrations in and around various industrial-size 3D printers, in this case large additive manufacturing processes using acrylonitrile−butadiene−styrene polymer feedstock. The model employed mass emission estimates determined from thermal gravimetric analysis and printer enclosure particle loss rates. Other model inputs included ranging terms for extrusion rate, temperature, print time, source-to-receiver distance, printer positions, particle size fraction, and environmental diffusivity estimates based on air changes per hour. Monte Carlo analysis bracketed measured environmental particulate concentrations associated with large-scale additive manufacturing processes (3D printing). Statistically, there was no difference between the average near-field particle concentrations measured and that of the model-derived average. However, the model began to vary more statistically, if not practically, from air-monitoring results in the far field. Diffusivity and extrusion rate emerged as the two most important variables in predicting environmental concentrations. This model can be used to estimate air concentrations over a range of varying conditions, such as one might employ in a "what if" type of evaluation to estimate employee exposure, for example, as a compliance effort with OSHA standard 29 CFR Part 1910.132, requiring a formal hazard assessment for work environments as a "before exposure" effort to determine if respiratory protection is needed.
3D printing or more specifically fused deposition modeling is the process of using a computer-aided design to extrude filament through a heated nozzle into an object, in which particulates and chemicals are released. Many universities are constructing fabrication laboratories to provide students access to 3D printers, laser cutters, and other tools. In university fabrication processes (3D printing and laser cutting), particulates and volatile organic compound (VOC) emissions were evaluated. The use of NIOSH's hierarchy of controls and traditional industrial hygiene air monitoring was employed to determine if particulate and chemical exposure was controlled. Results of a VOC, acrylate, and aldehyde scan revealed that all chemical constituents were below OSHA and ACGIH limits. The mass of particulates emitted is of limited concern; however number count or surface area may be more important to measure from a toxicological perspective. Particulate concentrations were significantly lower when local exhaust ventilation was on (Mann−Whitney, U = 553 026, p = 0.00). NIOSH's hierarchy of controls is effective for university fabrication laboratories; however, special note should be taken to install local exhaust ventilation and ensure flexibility in workspaces, employing isolation when possible.
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