Characterization of Particle and Volatile Organic Compound Emissions from Material Extrusion 3D Printing Using Metal Composite Filaments

Material extrusion 3D printing has been widely used in industrial, educational and residential environments. However, the associated emissions and exposure health impacts need to be evaluated, especially for the new and emerging filament materials. This study characterized particle and chemical emissions from 3D printing using five different metal composite filaments, which contain over 90% (by weight) of metal powder blended with polymer binders. The emission characterization was conducted using an exposure chamber following a standard testing method. Real-time particle measurements showed that particle emission rates ranged from 8 × 109 to 2 × 1011 particles/h for particle number and 200 to 1400 µg/h for particle mass. Over 98% of the emitted particles were smaller than 1 µm, which poses an inhalation hazard. Inductively coupled plasma–mass spectrometry analysis detected manganese, copper, zinc, and selenium in emitted particles from all filaments. However, metal powder in raw filaments tended not to be transferred into particle emissions, resulting in the total metals (and metalloids) accounting for 0.07% to 0.95% of emitted particle mass. Sorbent tube sampling and analytical analyses showed various volatile organic compounds emitted during printing, including hydrocarbons, alcohols, aldehydes, and aromatic compounds. Overall, metal composite filaments generated lower levels of volatile organic compounds (VOCs) compared to thermoplastic polymer filaments; in addition, the emitted VOC compositions differed. Organic chemicals associated with metal composite filament emissions included formaldehyde, benzaldehyde, acetaldehyde, naphthalene, and trimethylbenzene, exposure to which may cause irritations or other adverse health impacts. This study estimated personal exposure to hazardous components assuming a person is close to the printer with low ventilation to represent an acute worst-case exposure scenario. Modeled personal exposure to emissions showed potential exceedances of exposure to fine (PM2.5) and coarse (PM10) particulate matter, arsenic, manganese, formaldehyde, caprolactam, acetaldehyde, and naphthalene compared to reference levels. A modeled office room with ventilation showed reduced exposure levels by up to two orders of magnitude, assuming the same emission source. Users can avoid close proximity to an operating printer and increase dilution through larger room volumes and higher air change rates to reduce potential inhalation exposures at given printing conditions.