VOC & particle emissions from 3D printers

allfrogs_3dprinter

We are but simple frogs

The development of low-cost desktop versions of three-dimensional (3D) printers has made these devices widely accessible for rapid prototyping and small-scale manufacturing in home and office settings. Many desktop 3D printers rely on heated thermoplastic extrusion and deposition, which is a process that has been shown to have significant gas and/or particle emissions in other studies in industrial environments. To date, we have conducted two major studies of emissions of gases and particles from desktop 3D printers that use plastic extrusion and deposition technologies.

Our first study in 2013

In this work in 2013, we measured size-resolved and total ultrafine particle (UFP) concentrations resulting from the operation of a common type of these commercially available desktop 3D printers inside a commercial office space in Chicago. The printers were used to print small colorful frogs (we each got to take home a frog of our own!). The resulting measured particle concentrations during each operation period are shown below:

3dprinter_concentrations

Ultrafine particle concentrations measured during operation of 3D printers in a small office space

From the data, we also estimated size-resolved (11.5 nm to 116 nm) and total UFP (< 100 nm) emission rates and compared them to emission rates from other desktop devices and indoor activities known to emit fine and ultrafine particles. Estimates of emission rates of total UFPs were large, ranging from ~2.0×1010 #/minute for a 3D printer utilizing a lower temperature polylactic acid (PLA) feedstock to ~1.9×1011 #/min for the same type of 3D printer utilizing a higher temperature acrylonitrile butadiene styrene (ABS) thermoplastic feedstock. (You can read about some differences in these two feedstocks here and here). These emission rates are on about the same order as several other devices and activities known to emit UFPs, such as cooking on a gas or electric stove, burning scented candles, operating laser printers, or even burning a cigarette! (Some of you may also be thinking, “wait, laser printers emit as many small particles as a cigarette??” Yep!).

3d_ufp_emission_rates

Estimates of total UFP emission rates from individual 3D printers using either PLA or ABS feedstock

Human exposure to UFPs appears to be pretty important from a health perspective. These small particles deposit efficiently in both the pulmonary and alveolar regions of the lung, as well as in head airways. Deposition in head airways can also lead to translocation to the brain via the olfactory nerve. The high surface areas associated with UFPs also lead to high concentrations of other adsorbed or condensed compounds. Several recent epidemiological studies have also shown that elevated UFP number concentrations are associated with adverse health effects, including total and cardio-respiratory mortality, hospital admissions for stroke, and asthma symptoms. However, we don’t know much about the composition of these particles. We have some evidence that PLA-fed 3D printers may be less harmful than ABS-fed printers not only because of differences in emission rates, but also because PLA is actually biocompatible and used in a lot of medical procedures. We also are aware of a few older studies showing toxicity of ABS fumes (both gases and particles) to rats and mice. But how these interact in our respiratory systems and any associated adverse health effects are still largely unknown.

Regardless, because most of these devices are currently sold as standalone devices without any exhaust ventilation or filtration accessories, results from this work suggest caution should be used when operating in inadequately ventilated or unfiltered indoor environments. You should probably operate these under exhaust ventilation fume hoods (like you would operate an exhaust fan in your own kitchen). Alternatively, this opens the door for fabrication of some filtration devices. Overall, we believe that more controlled experiments should be conducted to more fundamentally evaluate particle emissions from a wider range of desktop 3D printers, as we tested only one product herein.

Read the open access article on this work, published in Atmospheric Environment in 2013.

There is also some good press coverage on this work:

Our second study, 2014-2016

In 2014 we were awarded a grant by the National Institute for Occupational Safety and Health (NIOSH) to further investigate emissions from desktop 3D printers and resulting exposures in realistic indoor environments. You can read the final report to NIOSH here. As part of this work, in January 2016, we published another open access article on more controlled environmental chamber testing of a greater number and variety of desktop 3D printers and filaments, this time in Environmental Science & Technology. In this work, we measured emissions of both ultrafine particles (UFPs) and volatile organic compounds (VOCs) from 5 commercially available polymer-extrusion 3D printers using up to 9 different filaments. We worked with Dr. Neil Crain at The University of Texas at Austin to conduct the VOC analysis using thermal desorption with gas chromatography and mass spectrometry (TD-GS-MS). We found that the individual VOCs emitted in the largest quantities included caprolactam from nylon-based and imitation wood and brick filaments (ranging from ~2 to ~180 µg/min), styrene from acrylonitrile butadiene styrene (ABS) and high-impact polystyrene (HIPS) filaments (ranging from ~10 to ~110 µg/min), and lactide from polylactic acid (PLA) filaments (ranging from ~4 to ~5 µg/min). These findings are critical, as styrene is classified as a “possible human carcinogen” by the International Agency for Research on Cancer (IARC classification group 2B) and is “reasonably anticipated to be a human carcinogen” according to the National Toxicology Program. While caprolactam is classified as “probably not carcinogenic to humans,” the California Office of Environmental Health Hazard Assessment (OEHHA) maintains low acute, 8-hour, and chronic reference exposure levels (RELs) of only 50, 7, and 2.2 g per cubic meters, respectively, all of which would likely be exceeded with just one of the higher emitting printers operating in a small office.

Estimates of emission rates for the top three highest-concentration VOCs as well as sum of the top 10 detectable VOCs (?VOC) resulting from operation of 16 3D printer and filament combinations.

Estimates of emission rates for the top three highest-concentration VOCs as well as sum of the top 10 detectable VOCs (?VOC) resulting from operation of 16 3D printer and filament combinations.

Further, the median estimates of time-varying UFP emission rates ranged from ?108 to ?1011 min–1 across all tested combinations, varying primarily by filament material and, to a lesser extent, bed temperature.

Summary of time-varying UFP emission rates estimated for 16 3D printer and filament combinations. Each data point represents data from 1 min intervals, and the combination of data points represents the entire printing period (typically between 2.5 and 4 h). Boxes show the 25th and 75th percentile values with the 50th percentile (median) in between. Whiskers represent upper and lower adjacent values, and circles represent outliers beyond those values.

Summary of time-varying UFP emission rates estimated for 16 3D printer and filament combinations.

And here are a few links to press coverage of this work:

Continued emissions testing in 2016-2017

In 2016, we continued to conduct periodic VOC and UFP emissions testing of several other printers and filament combinations. Results are provided in the individual reports below:

Acknowledgments

For the first study, we are very grateful to Built Environment Research Group members Tiffanie, Parham, and Zeineb for their help in making the measurements and writing the paper. We are also grateful for former IIT CAEE graduate student Bobby Zylstra and for Julie Friedman Steele from The 3D Printer Experience and The Metaspace, respectively, for providing access to the test space.

The second study was funded by the Centers for Disease Control and Prevention through the National Institute for Occupational Safety and Health (Grant ROH010699). Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the Centers for Disease Control and Prevention or the Department of Health and Human Services.