Particles from PLA were chemically similar to filament monomers, whereas the highest emitting ABS filament produced particles chemically dissimilar to the bulk filament. Toxicity tests indicated that particles were largely insoluble, since filtration of particle liquid extracts removed all toxic responses. All toxicity tests showed responses to FDM-emitted particles, with contrasting responses on a per surface area or mass basis for filaments of different composition.
However, particles emitted from ABS were more toxic than those emitted by PLA on a per unit print time or per print object mass (or filament consumed) basis. VOC emissions varied depending on filament material; total VOC emission rates were higher for ABS than PLA. Among the various detected VOCs, many have known potential hazards, such as styrene from ABS filaments and caprolactam from nylon filaments.
Concentrations of certain hazardous substances may exceed recommended levels when printing in small spaces with minimal outdoor air exchange. Therefore, strategies to reduce exposure include printing with low-emitting filaments, lowering extrusion temperature, enhancing outdoor air ventilation rates or providing a local exhaust, the study suggested. Emission results indicate that steps should be taken to minimize exposure in indoor environments.