No abstract

Settled house dust (SHD) is a reservoir for various contaminants, including endocrine‐disrupting chemicals (EDCs), trace metals, and house dust mite allergens. This study aimed to characterize various chemical and biological contaminants in SHD and identify determinants governing the indoor contaminants. In total, 106 SHD samples were collected from 106 houses in Seoul and Gyeonggi Province, Korea, in 2021. Bedding dust samples were collected from 30 of these 106 houses. All participants completed a questionnaire comprised of housing and lifestyle‐related factors. The samples were analyzed for 18 organophosphate flame retardants (OPFRs), 16 phthalates, five alternative plasticizers (APs), seven trace metals, and two house dust mite allergens (Dermatophagoides farinae type 1 [Der f1] and Dermatophagoides pteronyssinus type 1 [Der p1]). A multiple regression analysis was conducted to identify the determinants governing the concentrations and profiles of various contaminants. OPFRs, phthalates, APs, and trace metals were detected in all SHD samples, indicating ubiquitous contamination in indoor environments. Among the three EDC groups, APs were detected at the highest concentrations (geometric mean [GM] (geometric standard deviation, [GSD]): 1452 (1.6) μg/g in total), followed by phthalates (GM (GSD): 676 (1.4) μg/g in total) and OPFRs (GM (GSD): 10 (1.4) μg/g in total). Der f1 was detected in all bedding dust samples with significantly higher levels than Der p1 (GM (GSD): 0.1 (1.8) μg/g vs. 1.4 × 10−3 (2.3) μg/g). The concentrations of OPFRs, plasticizers, and trace metals in SHD were significantly associated with the type and number of electronic appliances and combustion activities. Der f1 was significantly associated with the number of occupants and water penetration. Ventilation, vacuum cleaning, and wet cleaning or dry mopping significantly reduced the levels of most contaminants in SHD. As residents are persistently exposed to a wide array of pollutants, comprehensive and adequate measures are required to prevent potential exposures.

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 "∏"-shaped partitions for the prevention of coronavirus disease . This study aimed to characterize UFP emissions from two types of 3D-pens and evaluate the influence of "∏"-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 "∏"-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 × 10 6 [3.4] particles/min and 1.1 × 10 6 [1.8] particles/ min), followed by polylactic acid (PLA) (2.8 × 10 5 [1.5] particles/min and 4.8 × 10 4 [1.8] particles/min) and polycaprolactone (PCL) filaments (1.4 × 10 4 [2.8] particles/min and 2.0 × 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 × 10 6 [1.15] particles/cm 3 vs. 1.4 × 10 5 [1.29] particles/cm 3 ) and PLA (6.2 × 10 5 [1.38] particles/cm 3 vs. 8.9 × 10 4 [1.12] particles/ cm 3 ), whereas for 3D-pen B, they were higher with the partition for ABS (9.6 × 10 5 [1.13] particles/cm 3 vs. 4.9 × 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.