CHICAGO — Three-dimensional printers using the fused deposition molding (FDM) process could pose a health risk to operators, according to researchers from the Illinois Institute of Technology in the U.S. and the National Institute of Applied Sciences in Lyon, France.
Writing in the journal Atmospheric Environment, Brent Stephens, Parham Azimi, Zeineb El Orch and Tiffanie Ramos note that “heated thermoplastic extrusion and deposition … is a process that has been shown to have significant aerosol emissions in industrial environments.
“Because most of these devices [consumer FDM 3-D printers] are currently sold as standalone devices without any exhaust ventilation or filtration accessories, results herein suggest caution should be used when operating in inadequately ventilated or unfiltered indoor environments.”
The researchers carried out their tests at a 3-D printing bureau in Chicago, The 3D Printing Experience. The experiments were conducted using five identical desktop FDM machines, two using polylactic acid feedstock and three using ABS.
The researchers acknowledge that the size of the experiment, and the limited time of the study (approximately 2½ hours) were not sufficient to draw absolute conclusions. But the indications are that consumer/hobbyist 3-D printers could pose a significant risk to human health from the inhalation of ultrafine particles (UFPs).
The paper notes that thermal decomposition of ABS has been shown to have toxic effects in both rats and mice.
The test was conducted in a 1,600-cubic-foot office space using a machine that measures the size of nanoparticles in the atmosphere. After background measurements were tested, a first test was conducted with two identical 3-D printers using PLA feedstock and a second test with two identical 3-D printers using PLA feedstock and a further three identical 3-D printers using ABS feedstock. The printers were programmed to print stock 3-D files of small plastic frogs and a plastic chain link.
The first test, with just PLA being used, resulted in increased concentrations of UFP larger than 20 nm. The second test, where two printers using PLA were supplemented by three printers using ABS, resulted in “substantial increases in all UFP sizes.”
The PLA-only test showed UFP concentrations were almost three times higher than background concentrations. When all five printers were in operation, this concentration elevated to nearly 15 times higher than background conditions.
The researchers' fears are founded on earlier research that suggests that UFPs deposited in both the pulmonary and alveolar regions of the lung, and in the head airways (possibly leading to direct translocation to the brain via the olfactory nerve). These UFPs also can bring with them high concentrations of other adsorbed compounds.
When PLA is used in an FDM printer, the baseplate is usually at room temperature (around 64°F) with the feedstock extruded from the nozzle at approximately 356°F. ABS, on the other hand, requires the baseplate to be at approximately 176°F with the feedstock extruded from the nozzle at around 428°F.
The higher temperature required for printing in ABS is thought to be a factor in the increased concentrations of UFPs. The researchers again note the toxicity of ABS during thermal decomposition whilst citing evidence to suggest PLA is relatively benign “PLA is known for its biocompatibility and PLA nanoparticles are widely used in drug delivery.
The researchers concluded that caution should be observed: “Emission rates of total UFPs were … an order of magnitude higher for 3-D printers utilizing an ABS thermoplastic feedstock relative to a PLA feedstock … However both can be characterised as ‘high emitters' of UFPs. These results suggests [sic] caution should be used when operating some commercially available 3-D printers in unvented or inadequately filtered indoor environments.”