Emission of particulate and gaseous pollutants from household laser processing machine.

Indoor air quality (IAQ) directly affects the health of occupants. Household manufacturing equipment (HME) used for hobbies or educational purposes is a new and unexplored source of air pollution. In this study, we evaluated the characteristics of particulate and gaseous pollutants produced by a household laser processing equipment (HLPE). Various target materials were tested using a commercial HLPE under various operating conditions of laser power and sheath air flow rate. The mode diameters of the emitted particles gradually decreased as laser power increased, while the particle number concentration (PNC) and particle emission rate (PER) increased. In addition, as the sheath air flow rate quadrupled from 10 to 40 L/min, the mode diameter of the emitted particles decreased by nearly 25%, but the effect on the PNC was insignificant. When the laser induced the target materials at 53 mW, the mode diameters of particles were <150 nm, and PNCs were >2.0 × 104 particles/cm3. Particularly, analyses of sampled aerosols indicated that harmful substances such as sulfur and barium were present in particles emitted from leather. The carcinogenic gaseous pollutants such as acrylonitrile, acetaldehyde, 1,3-butadiene, benzene, and C8 aromatics (ethylbenzene) were emitted from all target materials. In an actual indoor environment, the PNC of inhalable ultrafine particles (UFPs) was >5 × 104 particles/cm3 during 30 min of HLPE operation. Our results suggest that more meticulous control methods are needed, including the use of less harmful target materials along with filters or adsorbents that prevent emission of pollutants.

Water-Repellent TiO2-Organic Dye-Based Air Filters for Efficient Visible-Light-Activated Photochemical Inactivation against Bioaerosols.

Recently, bioaerosols, including the 2019 novel coronavirus, pose a serious threat to global public health. Herein, we introduce a visible-light-activated (VLA) antimicrobial air filter functionalized with titanium dioxide (TiO2)-crystal violet (CV) nanocomposites facilitating abandoned visible light from sunlight or indoor lights. The TiO2-CV based VLA antimicrobial air filters exhibit a potent inactivation rate of ∼99.98% and filtration efficiency of ∼99.9% against various bioaerosols. Under visible-light, the CV is involved in overall inactivation by inducing reactive oxygen species production both directly (CV itself) and indirectly (in combination with TiO2). Moreover, the susceptibility of the CV to humidity was significantly improved by forming a hydrophobic molecular layer on the TiO2 surface, highlighting its potential applicability in real environments such as exhaled or humid air. We believe this work can open a new avenue for designing and realizing practical antimicrobial technology using ubiquitous visible-light energy against the threat of infectious bioaerosols.

Continuous Surveillance of Bioaerosols On-Site Using an Automated Bioaerosol-Monitoring System.

Real-time on-site monitoring of bioaerosols in an air environment is important for preventing various adverse health effects including respiratory diseases and allergies caused by bioaerosols. Here, we report the development of an on-site automated bioaerosol-monitoring system (ABMS) using integrated units including a wet-cyclone bioaerosol sampler, a thermal-lysis unit for extracting adenosine triphosphate (ATP), an ATP-detection unit based on the immobilization of luciferase/luciferin for bioluminescence reactions, and a photomultiplier tube-based detector. The performance of the bioaerosol detection system was verified using Escherichia coli (E. coli) as a model source. Each unit was optimized to process ∼9.6 × 105 times the concentrated ratio of collected bioaerosol samples, using a 3 min lysis time to extract ATP, and has a detection limit of ∼375 colony-forming units (CFUs)/mL with more than 30 days of stability for the immobilized-luciferase/luciferin detection unit supported by a glass-fiber conjugation pad. After the integration of all units, the ABMS achieved E. coli bioaerosol monitoring with continuous detection at 5 min intervals and a minimum detection limit of ∼130 CFU/mair3. Furthermore, the rapid responsivity and stable operation performance of the ABMS under test-bed conditions and during a field test demonstrated that the ABMS is capable of continuously monitoring bioaerosols in real-time with high sensitivity. The monitoring system developed here with immobilization strategies for bioluminescence reactions triggered by ATP extracted from collected bioaerosol samples using a simple heat-lysis method may help establish sustainable platforms to obtain stable signals for the real-time detection of bioaerosols on-site.