Characteristics of ultrafine particles emitted from 3D-pens and effect of partition on children's exposure during 3D-pen operation

A three-dimensional (3D) printing pen is a popular writing instrument that uses a heated nozzle, and is similar to a 3D-printer. Processing thermoplastic filaments with a 3D-pen can emit ultrafine particles (UFPs). 3D-pen education sessions were held with "Pi"-shaped partitions for the prevention of coronavirus disease (COVID-19). This study aimed to characterize UFP emissions from two types of 3D-pens and evaluate the influence of "Pi"-shaped partitions on UFP exposure. Measurements of UFP emission rates and the size distribution of particles emitted from 3D-pens were conducted in a chamber (2.5 m(3)). The partition's influence on UFP exposure was evaluated with and without a "Pi"-shaped partition on a desk. A scanning mobility particle sizer (SMPS) and an optical particle spectrometer (OPS) were used to measure the particle number concentration (PNC) and size distribution. For both 3D-pen A and B, the average emission rates were statistically significantly highest for acrylonitrile butadiene styrene (ABS) filament (8.4 x 10(6) [3.4] particles/min and 1.1 x 10(6) [1.8] particles/min), followed by polylactic acid (PLA) (2.8 x 10(5) [1.5] particles/min and 4.8 x 10(4) [1.8] particles/min) and polycaprolactone (PCL) filaments (1.4 x 10(4) [2.8] particles/min and 2.0 x 10(4) [2.8] particles/min). For all filaments, particles in the Aitken mode (30-100 nm) accounted for the highest proportion. In 3D-pen A, PNCs were higher with the partition than without it for ABS (1.2 x 10(6) [1.15] particles/cm(3) vs. 1.4 x 10(5) [1.29] particles/cm(3)) and PLA (6.2 x 10(5) [1.38] particles/cm(3) vs. 8.9 x 10(4) [1.12] particles/cm(3)), whereas for 3D-pen B, they were higher with the partition for ABS (9.6 x 10(5) [1.13] particles/cm(3) vs. 4.9 x 10(5) [1.22] particles/cm(3)) only. With the partition installed, PNCs decreased to the background level after the operation ended, whereas it took 2-6 min without the partition. However, the mass concentrations of PLA and PCL with 3D-pen A were not statistically significantly different with respect to the partition status. The use of 3D-pens with a partition can lead to high UFP exposure. Therefore, guidelines are required for the safe use of 3D-pens and partitions.