Emissions standards for desktop 3D printers are in development after a research summit this year revealed some filaments for the machines emit carcinogenic and health-affecting volatile organic compounds, ozone reaction products, and ultra-fine particles during operation.
Marilyn Black, senior technical adviser at Underwriters Laboratories (UL), volunteered her organization to write the American National Standards Institute standards after 3D printing experts convened in February for the Safety Science of 3D Printing Summit. The goal is to have ANSI standards in place by year’s end, Black said.
She stressed that the science on 3D filament emissions is in progress, and more work needs to be done, including a risk assessment. Ongoing work will contribute to developing standards for how to measure emissions and determine their acceptable levels for human exposure.
“I like to be cautious with talking about chemicals,” Black said. “We’ve seen them, we’ve measured them, and sometimes the red light went on because the level went above the recommended level for indoor exposure. But just because a chemical has been characterized as a carcinogen, the likelihood of developing an adverse effect from it is subject to the level and length of the exposure.”
Among the filament materials tested for the research presented at the summit were acrylonitrile butadiene styrene, which emitted >70 VOCs; polylactic acid, associated with >20 VOC emissions; and nylon, which emitted primarily caprolactam, an eye and respiratory irritant.
At least two summit presenters recommended using physical controls to reduce human exposure to the emissions. These can include: installing upgraded HVAC filtration with a high-efficiency, activated-carbon filter; adding a standalone air cleaner with a clean air delivery rate of 100 or 300 m3/hour; installing spot ventilation; and creating custom enclosures for printers (closing the printers’ covers had little or no effect).
“Simulation results demonstrate that high-efficiency spot ventilation systems and custom-made enclosures have the highest impacts on reducing human exposures to emitted pollutants from 3D printers in near, adjacent, and far distances from the printer,” said Parham Azimi, Illinois Institute of Technology.
The VOCs emitted included three chemicals at levels above recommended guidelines: styrene, formaldehyde and caprolactam. Styrene is reasonably anticipated to be a carcinogen, and formaldehyde is a known carcinogen, according to the Agency for Toxic Substances and Disease Registry.
Research by Aleksandr Stefaniak of The National Institute for Occupational Safety and Health reported the presence of ozone reaction products during print runs. Information attributed to him also stated that exposure to emissions from ABS filament have shown increased blood pressure and other blood vessel-related changes in mice.
Exposure to ultra-fine particles (UFP) has been linked to a variety of adverse health effects. “UFPs are detrimental because they can be inhaled deeply into the lungs and be related to different types of respiratory diseases,” Black said. “Also, if they’re small enough, they can be absorbed into the blood system.”
Deeply penetrating particles are in the size range of about 50–1000 nm in aerodynamic diameter, according to research presented at the summit by Barry Ryan, Emory University.
“3D printers emit particles primarily in the size range of 50–700 nm,” Ryan said in his presentation. “Such particles penetrate deeply into the lung, reaching the alveoli and potentially penetrating the lung epithelium. Here they can result in irritation, respiratory effects, and changes in blood chemistry that may precipitate cardiovascular effects.”
Ryan pointed out that his research to date has treated the particles as neutral. Further study is under consideration regarding applying a toxicity index to the particles, which would likely change their predicted impact, he said.
Black pointed out that while there are OSHA standards for 3D printers in an industrial setting, there are none for desktop models, only general guidelines.
The proceedings of the safety summit can be found at www.ulchemicalsafety.org.