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Recent 3D Printer Emissions Research at EPA
Citation:
Byrley, P., A. Wallace, A. Jarabek, W. Boyes, AND K. Rogers. Recent 3D Printer Emissions Research at EPA. Society for Risk Analysis, NA, Virtual, December 13 - 17, 2020.
Impact/Purpose:
Fused Deposition Modeling (FDM) 3D printers have been shown to produce emissions that consist of both particles and volatile organic compounds (VOCs) that are released from the heated feedstock material as it is pushed through the printer's nozzle to create a 3D object. The majority of these particles have been consistently found to be ultrafine in size (less than 100 nm in physical diameter) and released on the order of millions to billions of particles per minute. This presentation summarizes two studies conducted at EPA that investigated emissions from 3D printer technology. The first study investigated emissions from a 3D printer filament extruder. To reduce the filament cost, 3D printer filament extruders are being used in residential and small business settings to create filaments for 3D printers and customized compositions. Given the similarity in processes and materials used by 3D printers and filament extruders, we hypothesized that filament extruders may also release ultrafine particle emissions and VOCs. An off-the-shelf filament extruder was operated in a 2 m3 chamber using three separate feedstocks: acrylonitrile butadiene styrene (ABS) pellets, pulverized poly-lactic acid (PLA), and PLA pellets. Ultrafine particle emissions were measured in real-time using a scanning mobility particle sizer and thermal desorption tubes were used for both non-targeted and targeted analysis of VOCs present in emissions. Ultrafine particle number concentrations were comparable to those found in 3D printer studies with the greatest to least concentrations from ABS pellets, pulverized PLA, and PLA pellets, respectively. A variety of VOCs were identified using the ABS feedstock, including styrene and ethylbenzene. Exposure to particles and VOCs from the use of these devices may pose a risk to users particularly in confined spaces. Given the increasing use of these processes, program or regional partners, general public, and local communities will likely find this study of interest. The second study predicted inhaled deposited dose of particles from exposure to a 3D printer. A 3D printer was operated in a 2 m3 chamber using two separate feedstocks: acrylonitrile butadiene styrene (ABS) and poly-lactic acid (PLA). Ultrafine particle emissions were measured in real-time using a scanning mobility particle sizer. The deposition of these particles in the respiratory system was then predicted using the Multiple-Path Particle Dosimetry (MPPD) model (version 3.04) for Caucasian adult males versus females and children of various ages. As shown for ultrafine particles from other sources, the majority of particle mass was predicted to deposit in the pulmonary (PU) region. Differences were predicted in the total inhaled mass and surface area of particles deposited in the 3 major regions of the respiratory tract, and across different age groups and between male and female adults. These results demonstrate that translation to internal dose should be carefully evaluated when characterizing exposure concerns for 3D printer emission particles, especially when considering the potential exposure for young users.
Description:
Rationale: Numerous studies have confirmed the release of ultrafine particles (UFPs) and volatile organic compounds (VOCs) from Fused Deposition Modeling (FDM®) 3D printers. There is now opportunity to broaden the scope of 3D printing emissions research, beyond detection of 3D printer emissions, to understand emissions from accessory technologies such as filament extruders, and to translate exposure to 3D printing emissions through dosimetry modeling to inhaled deposited dose. Methods: This presentation will describe recent studies performed at EPA on 3D printer filament extrusion and inhalation dosimetry modeling. A 3D printer filament extruder was run inside of a test chamber using three different plastic feedstocks. In addition, the Multiple Path Particle Dosimetry (MPPD) model version 3.04 was applied to 3D printer emissions from a separate test chamber study. Results and Discussion: The filament extrusion process was found to release UFPs and VOCs with particle number emission rates comparable to 3D printer studies. Results of the MPPD modeling study predicted higher mass deposition per pulmonary surface area in 3-month-old, 23-month-old, 3-year-old, and 9-year-old subjects compared to older subjects. Ongoing work is further characterizing the organic and metal composition of 3D printer emissions. Conclusion and Implication: This research shows that use of filament extruder technology may present additional exposures comparable to those from 3D printers. The higher deposition in the pulmonary region of children compared to adults predicted by the dosimetry model suggests a potentially susceptible population due to both exposure and status of respiratory tract development. The views expressed in this abstract do not necessarily represent the views and policies of the U.S. Environmental Protection Agency.