The Chemical Insights Research Institute (CIRI), an arm of safety research specialist UL Research Institutes, has published a study highlighting the health risks associated with material extrusion 3D printing. Said to be the most comprehensive database of 3D printing emissions in scientific literature, CIRI conducted over 500 exposure studies over five years.
The researchers found that FFF 3D printing emits ultrafine particles (UFP) and volatile organic compounds (VOC). These emissions can be harmful and include chemicals known to be carcinogens, irritants, and developmental and reproductive toxins.
Titled “Exposure hazards of particles and volatile organic compounds emitted from material extrusion 3D printing: Consolidation of chamber study data,” these findings were published in the December 2023 edition of Environment International. The primary authors of this study were Qian Zhang and Marilyn S. Black.
“3D printing emits a complex mixture of ultrafine particles and various hazardous chemicals, exposure to which may exceed recommended exposure limits and potentially induce acute, chronic, or developmental health effects,” the researchers claim. “Users should be aware of the potential hazards of emissions and take appropriate practices to mitigate exposure,” the researchers commented in the paper.
Recommended precautions include 3D printing in spacious environments, improving ventilation, and avoiding high-emitting materials such as those possessing styrene monomers.
Investigating 3D printing emissions
Material extrusion 3D printing is the most widely used 3D printing technology in non-industrial environments, such as office settings and educational institutions. The growing use of 3D printers in domestic environments has reportedly led to public health concerns, with users experiencing headaches, irritation and respiratory symptoms.
To fully assess these health risks, the researchers conducted 447 3D print runs to measure particle emissions, and 58 3D print runs for VOC emissions. The researchers tested 14 FFF 3D printers from six unnamed manufacturers.
45 filaments of different colors and materials, from 13 different manufacturers, were assessed. These materials included widely available polymers such as ABS, PLA, nylon, HIPS, PVA, PETG, ASA, and TPU. Composite materials such as polycarbonate (PC), flame retardant (FR), bronze powder, chopped carbon fiber, and glass fiber, which were blended with ABS, PLA and nylon polymers, were also assessed. The researchers also analyzed metal composite filaments.
Following the testing, statistical analysis was used to evaluate the correlation between particle and VOC emissions and 3D print conditions. These conditions include 3D printer design, setup, and filament material and properties.
The findings of CIRI’s study
The researchers found that ABS, HIPS, and nylon materials produced the highest particle emissions. Particles emitted during 3D printing are mainly ultrafine in size, and can penetrate deeply into human lungs, bloodstream and the brain. As such, these emissions are associated with respiratory and cardiovascular diseases. Metal composite material tended to emit larger particles, and produce higher mass emissions.
Moreover, carcinogens such as formaldehyde, styrene, and acetaldehyde were detected from 80% of the filaments studied. The researchers identified an extensive list of VOCs emitted during 3D printing, including aromatics, aldehydes, alcohols, ketones, esters and siloxanes.
The emissions of harmful chemicals were found to exceed the NAAQS recommended air quality limits. Benzene, styrene, formaldehyde, benzaldehyde, acetaldehyde, and caprolactam were the VOCs of most concern.
ABS and HIPS materias were highlighted as posing the most concern in terms of both particle and VOC exposure. Nylon presented high particle and caprolactam exposure, whilst ASA was found to emit substantial amounts of hazardous VOCs. The researchers found that PLA showed generally low VOC and particle emissions, despite some outliers.
Altering 3D printer and filament conditions created large variations in emission levels. Interestingly, particle emissions were found to be more sensitive to 3D printing conditions than VOC emissions.
For ABS, filament color was found to be an important variable for particle emissions. Black colored filament tended to be a lower emitting material, while all other colors possessed positive coefficients.
Increasing the extrusion temperature increased ABS particle emissions, but decreased PLA emissions in this study. What’s more, increasing 3D printing speed was found to significantly increase particle emissions from ABS, whereas “no significant association was found with PLA.”
Ultimately, the researchers concluded that FFF 3D printing poses a health concern due to the mixture of UFPs and hazardous chemicals emitted. Particles emitted from ASB, PLA, and nylon materials have been shown to induce inflammatory responses, cell deaths and oxidative stress, indicating adverse health impacts after inhalation.
As such, the researchers believe that users should be aware of the potential health hazards associated with 3D printing, and take necessary precautions to limit these risks.
The health impacts of 3D printing
This is not the first time the CIRI has conducted research into the negative health impacts of 3D printing. Last year, a CIRI toxicity study found that fumes created when printing ABS or PLA filaments, can “contribute to airway cellular injury and inflammation.”
The study found that high doses of ABS 3D printing fumes resulted in a 49.5% decline in lung cell viability. What’s more, the researchers found that PLA and ABS emissions can result in a decline in oxidative stress, increase DNA damage, and create high levels of metabolites. Ultimately, ABS was found to possess higher toxicity than PLA.
In 2021, BOFA International, a developer of fume and particle extraction technology, published a research paper reviewing the health impact of gasses and particulates emitted during 3D printing.
This report focused on FFF and vat polymerization 3D printing, and found that the temperature of the nozzle dramatically influences the volume of particles generated by FFF 3D printing. In terms of vat polymerization, the report found that photoreaction caused by heating liquid material can emit damaging nanoparticulate airborne matter.
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Featured image shows a 3D printer inside a CIRI emissions chamber. Photo via CIRI.
