Evaluation of nanoparticle emissions from a laser printer in an experimental chamber and estimation of the human particle dose

Effect of spraying air freshener on particulate and volatile organic compounds in vehicles

People in these days spend approximately 6 % of their time in a means of transport. Air fresheners are frequently used in vehicles to mask odors; however, they can cause adverse health effects such as cardiovascular disease, systemic inflammation and autonomic dysfunction. This study aimed to identify the effects of air fresheners on the concentrations of particulate and volatile organic compounds (VOCs) in different vehicle cabins. Scanning mobility and optical particle sizers were used for the particle measurements. VOCs (e.g., BTEX and d-limonene) were collected using a Tenax TA. The products were sprayed for less than a minute. The study assessed three spray products (all trigger types), vehicle size (small, medium, and large), cabin temperature (10 °C, 20 °C, and 25 °C), and in-vehicle ventilation mode (all-off, recirculation, and external inflow modes). The particle concentration increased rapidly during the 1-min spraying of the products. The proportion of nanoparticles in the front seat (67.2 % ± 2.2 %) was 11.1 % ± 2.2 % lower than that in the rear seat (75.6 % ± 2.1 %). The spray product and vehicle size did not significantly affect the particle or VOC concentrations. With an increase in the temperature of the front seat, the proportion of nanoparticles increased by 25.3 % ± 3.2 %. Moreover, the maximum total VOC concentrations (front seat: 364.3 μg/m3; back seat: 241.3 μg/m3) were observed at 20 °C. Under in-vehicle ventilation, recirculation effectively reduced the overall particle concentration within the cabin; however, the generated VOCs circulated. The external inflow proved effective in cabin air purification by reducing the total VOC concentration to 56.0-57.2 % compared with other ventilation modes. These findings provide substantial insight into the persistence of particles and the dynamics of their dispersion, thereby enabling informed decision-making for particle-related risk management.

A case study on occupational exposure assessment and characterization of particles in a printing shop in China

Printers can release numerous particles to contaminate indoor environments and pose health risks. Clarifying the exposure level and physicochemical properties of printer-emitted particles (PEPs) will help to evaluate the health risks of printer operator. In our study, the particles concentration in the printing shop was monitored in real time for a long time (12 h/day, total 6 days), and the PEPs were collected to characterize their physicochemical properties including shape, size and compositions. The result showed that the concentration of PEPs is closely related to the printing workload and the highest particle mass concentration of PM₁₀ and PM_2.5 was 212.73 μg m^-3 and 91.48 μg m^-3, respectively. The concentration of PM₁ in the printing shop was in the range of 11.88-80.59 μg m^-3 for mass value, and 174.83-1348.84 P cm^-3 for count value which changed with the printing volume. The particle sizes of PEPs were less than 900 nm, 47.99% of PEPs was less than 200 nm, and 14.21% of the particles were at the nanoscale. PEPs contained 68.92% organic carbon (OC), 5.31% elemental carbon (EC), 3.17% metal elements, and 22.60% other inorganic additives, which contained more OC and metal elements than toners. Total polycyclic aromatic hydrocarbons (PAHs) levels were 18.95 ng/mg in toner and 120.70 ng/mg in PEPs. The carcinogenic risk of PAHs in PEPs was 1.40 × 10^-7. These findings suggested future studies should pay more attention to the health effects of printing workers exposed to nanoparticles.

Short-term associations of PM2.5 and PM2.5 constituents with immune biomarkers: A panel study in people living with HIV/AIDS

Studies on associations of fine particulate matter (PM_2.5) with immunity in people living with HIV/AIDS (PLWHA) were absent. We aimed to explore whether changes of immune biomarkers were associated with short-term exposure to PM_2.5 in PLWHA. Based on a panel study in Wuhan, we selected 163 PLWHA as participants with up to 4 repeated visits from March 2020 to January 2021. Immune biomarkers, including CD4⁺T cell count, CD8⁺T cell count, HIV viral load (VL) and CD4⁺T/CD8⁺T ratio were tested for all participants at each visit. Residential exposures of PM_2.5 and PM_2.5 constituents for each participant were assessed using spatial-temporal models. Linear mixed-effect models and general linear mixed models were applied to evaluate the associations between PM_2.5 and immune biomarkers. To estimate the combined effect of PM_2.5 constituents, weighted quantile sum regression and Bayesian kernel machine regression were employed. Each 10 μg/m³ increase of 7-day average PM_2.5 concentrations was associated with an 8.75 cells/mm³ (95%CI: -15.55, -1.98) decrease in CD4⁺T cell count and a 92% (OR: 1.92, 95%CI: 1.43, 2.58) increased odds ratio of detectable HIV VL. However, the odds ratio of inverted CD4⁺T/CD8⁺T was only positively associated with PM_2.5 concentrations at lag2 day (OR:1.27, 95%CI:1.02, 1.57). CD4⁺T may be a potential mediator between PM_2.5 and detectable HIV VL with 3.83% mediated proportion. Besides, the combined effect of PM_2.5 chemical constituents indicated that NO₃^- and SO₄^2- were the main constituents in reducing CD4⁺T cell count and increasing odds ratio of detectable HIV VL. Our finding revealed that short-term exposure to PM_2.5 was negatively associated with CD4⁺T cell count but positively related to the odds ratio of detectable HIV VL in PLWHA. This research may provide new evidence in associations between PM_2.5 and immune biomarkers as well as improving prognosis of PLWHA.

Transient and continuous effects of indoor human movement on nanoparticle concentrations in a sitting person's breathing zone

Particle concentration in a sitting person's breathing zone can be influenced by human movement around the person, and the transient and continuous effects may differ. In this study, a set of full-scale experiments was conducted to sample the nanoparticle concentration in the breathing zone of a sitting thermal breathing manikin (STBM). The transient fluctuation of the nanoparticle concentration was recorded continuously and analyzed. The results showed that when a manikin moved (at 1 m/s) past the STBM, the nanoparticle concentration in the STBM's breathing zone decreased and reached its lowest after the standing manikin had passed, decreasing 37.6 (±5.7) % compared with the peak value. The average concentration in the STBM's breathing zone during influence periods was 5.18 (±0.99) % less than that during non-influence Periods (NP). This finding reflected the fact that the transient inhalation (over several seconds) of the STBM may be reduced by manikin movement. On the other hand, the exposure of the STBM increased 2.88 (±1.24) % when there was a continuously moving manikin compared with the stable state in a 10-min observation. This finding may be explained by the fuller mix of indoor air and nanoparticles caused by manikin movement, as well as the increase of nanoparticle suspension time. The difference in the transient and continuous effects of the manikin movement on the STBM's exposure shows the importance of considering these effects separately in different scenarios.

Review of the characteristics and possible health effects of particles emitted from laser printing devices

Many studies have shown that the use of laser printing devices (LPDs) contributes to the release of particles into the indoor environment. However, after more than two decades of research, the physicochemical properties of LPD-emitted particles and the possible health effects from exposure to particles are still heavily debated. We therefore carried out a critical review of the published studies around emissions and health effects of LPD-emitted particles, aiming at elucidating the nature of these particles and their potential health risks. Realizing the varying methodologies of the studies, a classification of the reviewed studies is adopted, resulting in three categories of emission studies (chamber experiment, office/room measurement, and photocopy shop measurement), and three types of health studies (in vitro/animal studies, human studies in the real world, and human studies in controlled settings). The strengths and limitations of each type of study are discussed in-depth, which in turn helps to understand the cause of divergent results. Overall, LPD-emitted particles are mainly condensed or secondary-formed semi-volatile organic compounds (SVOCs), while solid toner particles account for a very small fraction. The health risk from exposure to LPD-emitted particles is small compared with the health risk from exposure to ambient particles.