It’s been known for several years that desktop 3D printers, and presumably any extrusion 3D printer operating in an open environment, can be potentially dangerous due to the creation of ultrafine particles (UFPs) and volatile organic compounds (VOCs). The studies thus far, however, have been fairly limited in nature.
UL Chemical Safety and Georgia Institute of Technology (Georgia Tech) have now published two of the most extensive studies on the topic to date. Focusing on desktop 3D printers, the partners found that the machines produce UFPs during operation that can be inhaled and brought deep into the pulmonary system. They also found over 200 VOCs, including irritants and carcinogens.
Naturally, this information could affect how and where a 3D printer is used, what sort of materials might be printed with and how suitable this technology might be in a classroom setting.
To get a better understanding of what this means and how to deal with this information, engineering.com has looked further into the research and provided some context here.
Previous Studies
3D printing journalist and professor Mark Lee has documented the history of safety research in desktop 3D printers. He pointed out that in 2007, it was discovered that 2D laser printers emit UFPs. The particulate matter was five times greater during working hours, which resulted in a public relations issue for HP, which ultimately remedied the issue.
In 2013, it was discovered by the Illinois Institute of Technology that UFPs were emitted by desktop 3D printers using filament extrusion technology. In thermal plastic processing, gases and particles are emitted, as well. Using two printers printing with the cornstarch-based polylactic acid (PLA) and three printing with acrylonitrile butadiene styrene (ABS), the team found that the amount of UFPs in a closed room increased 15 times the background rate when the machines were operating.
In 2015, researchers at Seoul National University conducted a study with two different plastic extrusion printers using PLA and ABS inside of a 1-square-meter test chamber, looking for both UFP and VOC emissions. PLA produced UFP rates that were 21 to 26 times higher than the background and some VOCs, including formaldehyde emissions 5.2 times higher than outside air concentrations.
ABS was much worse with UFP particle counts 345 greater than the background rate and various vapors, including ethylbenzene levels “16.4 times higher than outdoor air concentrations, isovaleraldehyde at 11.9 times higher, acetaldehyde at 3.2 times higher,” according to Lee.
In 2016, a new study from the Illinois Institute of Technology examined different plastic filament types and both UFPs and VOCs. ABS produced the most UFPs and VOCs, but the team notably found that “only three chemicals made up over 70 percent of all VOC emissions; namely styrene from ABS and HIPS, caprolactam from Nylon, PCTPE, Laybrick and Laywood, and lactide from PLA.”
To learn more about these previous studies, it’s worth reading Lee’s full article.
UL and Georgia Tech’s Research
UL Chemical Safety and Georgia Tech published two papers, "Characterization of particle emissions from consumer fused deposition modeling 3D printers” and “Investigating particle emissions and aerosol dynamics from a consumer fused deposition modeling 3D printer with a lognormal moment aerosol model,” in Aerosol Science and Technology. The partners also have two more papers under review.
Rodney J. Weber, a professor at the School of Earth and Atmospheric Sciences at Georgia Tech, explained in a video abstract for the first paper (below) that the team’s attempt was to characterize the emissions of desktop 3D printers using a standardized approach developed for use with 2D laser printers. In particular, a 1 × 1 × 1m steel insulated chamber was used, based on ASTM standards.
The first paper saw researchers test six different 3D printers with three different materials— ABS, PLA and nylon—from different material makers at various extrusion and build plate temperatures. This resulted in “52 combinations of printer brand, filament material, filament brand, filament color and extruder temperature.”
The researchers found that such features as filament color, brand and material, as well as printer brand, can affect emissions. Whereas PLA had relatively stable emissions across filament variables, emissions did vary with printer manufacturer. ABS saw more variations across filament brand, followed by printer brand, and least by color.
PLA was not affected greatly by extruder temperature, but printing with ABS at higher temperatures resulted in greater emissions. High build-plate temperatures resulted in increased particle sizes.
Recommendations
With an industry standard, Weber hopes that companies can “self-regulate” by testing their systems and aiming to meet the standard. Manufacturers can then label their machines as “green” or “low-emission” 3D printers.
He confirmed that PLA emits the least amount of aerosols, though third-party filament makers could have higher emissions than materials made by the printer manufacturers themselves or a name brand. The cheapest brands are the most suspect, according to Weber, so he suggests printer manufacturers recommend their own brands of filaments.
While PLA may be safer for school settings, the material does emit UFPs and VOCs. For this reason, UL and Georgia Tech recommend that:
- 3D printers only be operated in well-ventilated areas
- Nozzle temperature be set at the lower end of the suggested temperature range of a given material
- Stand away from machines under operation
- Use systems and materials that have been tested and verified to have low emissions
Industry Implications
Clearly, emissions from any equipment is a problem, but desktop 3D printers need to be carefully considered before purchased for a classroom and the above precautions must be taken. UL and Georgia Tech will continue to test materials, as new filaments are always being released. This study is only examining the desktop arena and doesn’t take into account the use of HIPA filters on some desktop systems or the potential hazards of industrial equipment.
It also doesn’t take into account the future of the plastics industry. Europe is already on track to ban single-use plastic due to widespread pollution and even ingestion of the materials. Also, as countries begin to react to the latest special report from the Intergovernmental Panel on Climate Change—which projects that we have 12 years to cut greenhouse gas emissions by 45 percent in order to avoid cataclysmic climate change—petroleum-based plastics like ABS may have a limited market life.
In the short-term these studies may urge greater caution when using 3D printing, but, in the long-term we may need to find non-toxic materials to use altogether.