Citation:

Hasan, F., Phillip M. Potter, Souhail R. Al-Abed, J. Matheson, AND S. Lomnicki. Investigating environmentally persistent free radicals (EPFRs) emissions of 3D printing process. Chemical Engineering Journal. Elsevier BV, AMSTERDAM, Netherlands, 480:148158, (2024). https://doi.org/10.1016/j.cej.2023.148158

Impact/Purpose:

The emissions from 3D printers have been shown to include particulate matter, including PM2.5, and volatile organic compounds (VOCs). The results from this study also show the presence of Environmentally Persistent Free Radicals (EPFRs) on the particulate emitted from 3D printers. EPFRs are surface-bound radical species that result from the interaction of metals and certain organic compounds. EPFRs are known to generate reactive oxygen species (ROS) in biological media. These results represent a previously unknown harmful component of 3D printer emissions and should be considered in all future emissions testing and assessments.  

Description:

In recent years, the emission of particles and gaseous pollutants from 3D printing has attracted much attention due to potential health risks. This study investigated the generation of environmentally persistent free radicals (EPFRs, organic free radicals stabilized on or inside particles) in total particulate matter (TPM) released during the 3D printing process. Commercially available 3D printer filaments, made of acrylonitrile–butadiene–styrene (ABS) in two different colors and metal content, ABS-blue (19.66 µg/g Cu) and ABS-black (3.69 µg/g Fe), were used for printing. We hypothesized that the metal content/composition of the filaments contributes not only to the type and number of EPFRs in TPM emissions, but also impacts the overall yield of TPM emissions. TPM emissions during printing with ABS-blue (11.28 µg/g of printed material) were higher than with ABS-black (7.29 µg/g). Electron paramagnetic resonance (EPR) spectroscopy, employed to measure EPFRs in TPM emissions of both filaments, revealed higher EPFR concentrations in ABS-blue TPM (6.23 × 1017 spins/g) than in ABS-black TPM (9.72 × 1016 spins/g). The presence of copper in the ABS-blue contributed to the formation of mostly oxygen-centered EPFR species with a g-factor of ∼2.0041 and a lifetime of 98 days. The ABS-black EPFR signal had a lower g-factor of ∼2.0011, reflecting the formation of superoxide radicals during the printing process, which were shown to have an “estimated tentative” lifetime of 26 days. Both radical species (EPFRs and superoxides) translate to a potential health risk through inhalation of emitted particles.

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