Aerosol and Air Quality Research
- OpenAccess
社團法人台灣氣膠研究學會,正常發行
選擇卷期
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During the sever pandemic of coronavirus, the development and deployment of efficient disinfection technology have attracted hospitals' attention. Chlorine dioxide (ClO_2) gas has been validated as an efficient disinfector and air pollution control due its high oxidation ability. This article reviewed the principles and application of ClO_2 gas on disinfection, sterilization and air pollutants abatement. The principles of ClO_2 gas production, chemistry and related generator issues were discussed. We also review some case studies of the application of ClO_2 gas in the medical field and food industry as a sterilizer. Oxidation of nitrogen oxide (NO_x), sulfur oxide (SO_x), mercury (Hg), and volatile organic compounds (VOCs) using ClO_2 gas has been investigated. The process chemistry and demonstration of applying ClO_2 gas for air pollutants oxidation and absorption have also been provided. In conclusion, we suggest the future priority research direction of ClO_2 gas application are included the development of smart and robust ClO_2 gas release system, the integration of an innovative robotic technology in ClO_2 sterilization for epidemic prevention, and the evaluation of ClO_2 emissions impact on indoor air quality in hospitals.
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There is a severe shortage of face masks and N95 respirators due to the current COVID-19 pandemic, particularly in countries that were not well prepared in advance. In order to help ease the supply demands of these resources, a strategy of using multiple layers of basic filtration media to construct a composite filter that can match the particle collection efficiency offered by a N95 filtering facepiece respirator (FFR) is proposed. In this study, the filtration performances of four face masks and one N95 respirator using the same test protocol (as a reference) were first compared. Composite filter samples composed of multiple layers of basic face mask and MERV13 furnace media were then constructed and the filter performance of the composite filters was investigated. As expected, the minimum particle collection efficiency of the N95 respirator media sample was higher than 95% and the efficiency of the samples from the four tested face masks varied from 71.8% to 83.6%. The Figure of Merit (FOM) values of the face mask samples were generally half that of the N95 media sample. It was found that a N95-comparable collection efficiency can be achieved by combining two/three layers of face mask media but at the expense of a higher media pressure drop. Additionally, the composite filter samples made up of three/five layers of MERV13 furnace media could approach the FOM offered by the N95 media without the increased pressure drop. It was also found that the measured collection efficiency of multiple-layered filter media was not equal to the calculated in the test particle size range. Further studies are required to identify the reason(s).
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While the novel coronavirus pandemic (COVID-19) continues to wreak havoc globally, self-protection from possible infection by wearing a mask in daily life has become the norm in many places. The unprecedented demand for masks has now attracted attention on their filtration efficiency. Furthermore, the widespread use of disposable masks has led to shortage of filter materials and problems with their haphazard disposal. In this study, a testing system that is based on standardized methods has been established and enhanced to reliably measure the particle filtration efficiency (PFE) of masks. Quality control experiments that examine the filtration efficiency of polystyrene latex (PSL) particles that are 0.1 μm in size and sodium chloride (NaCl) particles that range from 0.01-1.0 μm are conducted to determine the reliability of the testing system. Moreover, various textile materials are tested to fabricate 3-layer face masks, and the PFE of these masks is tested by using the proposed testing system to find the most suitable materials and the likelihood of their reusability. Among the tested materials, polytetrafluoroethylene (PTFE) used as the membrane in the filter layer has the highest PFE of 88.33% ± 1.80%, which is mainly due to its dense and multilayer structure. The air permeability of the self-developed masks ranges from 1.41 ± 0.04 to 1.93 ± 0.08, less breathable than the commercial masks. The reusability of a mask that uses PTFE as the membrane in the filter layer is tested by gently washing the mask 30 times and then drying the mask in air before the PFE is measured. The PFE is only reduced by 10-20% after 30 washes, thus indicating the potential reusability of the mask. The findings in this study will contribute to reducing the pressure of mask shortages and are an environmentally friendly solution to the massive use of disposable masks.
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Concentrations of primary air pollutants are driven by emissions and weather patterns, which control their production and dispersion. The early months of the year see the celebratory use of fireworks, a week-long public holiday in China, but in 2020 overlapped in Hubei Province with lockdowns, some of ＞ 70 days duration. The urban lockdowns enforced to mitigate the COVID-19 pandemic give a chance to explore the effect of rapid changes in societal activities on air pollution, with a public willing to leave views on social media and show a continuing concern about the return of pollution problems after COVID-19 restrictions are lifted. Fireworks typically give rise to sharp peaks in PM_(2.5) concentrations, though the magnitude of these peaks in both Wuhan and Beijing has decreased under tighter regulation in recent years, along with general reductions in pollutant emissions. Firework smoke is now most evident in smaller outlying cities and towns. The holiday effect, a reduction in pollutant concentrations when normal work activities are curtailed, is only apparent for NO_2 in the holiday week in Wuhan (2015-2020), but not Beijing. Lockdown in Wuhan was characterised by decreases in NO_2, along with more subtle changes in particulate matter and other pollutants. Ozone noticeably increases as there is less NO available for titration, but such change may not be widespread geographically. Beijing, where restrictions were less stringent, showed some improvement in air quality, though this is more difficult to detect, even within the 5^(th) Ring Road.
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Particle-phase air pollution is a leading risk factor for premature death globally and impacts climate by scattering or absorbing radiation and changing cloud properties. Within the Beijing-Tianjin-Hebei region of China, where there are severe air quality problems, several municipalities have begun implementing a coal-to-electricity program that bans residential coal and provides subsidies for electricity and electric-powered heat pumps. We used GEOS-Chem to evaluate two complete residential coal-to-electricity transitions-a Beijing-off scenario and Beijing-Tianjin-Hebei-off scenario-each relative to a base case. We estimate that within China, the ambient fine particulate matter (PM_(2.5)) reductions in the Beijing-off scenario could lead to 1,900 (95% CI: 1,200-2,700) premature deaths avoided annually, while the Beijing-Tianjin-Hebei-off scenario could lead to 13,700 (95% CI: 8,900-19,600) premature deaths avoided annually. Additionally, we estimate that the residential-coal-ban scenarios will result in a positive top-of-the-atmosphere aerosol direct radiative effect (DRE) (model domain average: Beijing-off: 0.023 W m^(-2); Beijing-Tianjin-Hebei-off: 0.30 W m^(-2)) and a negligible cloud-albedo aerosol indirect effect (AIE) (Beijing-off: 0.0001 W m^(-2); Beijing-Tianjin-Hebei-off: 0.0027 W m^(-2). To evaluate the uncertainty of the radiative effects, we calculated the DRE under four black-carbon mixing-state assumptions and both the DRE and AIE assuming three different black-carbon-to-organic-aerosol (BC:OA) ratios for residential-coal emissions. Although the magnitude of our radiative forcing estimates varied across sensitivity cases, the domain average remained positive. When only considering the aerosol-related effects of the aforementioned coal-ban scenarios, we predict substantial health benefits, but do not anticipate a climate ＂co-benefit＂, because removing aerosol emissions leads to a warming tendency. However, if the coal-to-electricity program results in less net greenhouse gas emissions due to the replacement heaters, the policy may be able to achieve health and climate ＂co-benefits＂.
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Cement mineral dust contains a variety of carcinogenic and non-carcinogenic substances. The study aimed to determine the probability of health risk among cement workers due to respirable silica (Si), arsenic (As), and chromium (Cr) VI dust exposure. A cross-sectional study was carried out among 123 cement workers. A personal air sampling pump was used to assess respirable cement dust exposure. Inductively coupled plasma mass spectrometry (ICP-MS) was used for As, and Cr analysis, and X-ray powder diffraction (XRD) was used for Si analysis. The Fractional Exhaled Nitric Oxide levels and lung function test were obtained by using NIOX MINO and Chestgraph H1-105 spirometer. Risk assessment was calculated by using the incremental lifetime cancer risk (ILCR) and non-cancerous hazard quotient (HQ). The geometric mean and standard deviation of respirable Si and Cr dust concentrations were 5.27 ± 2.36 mg m^(-3) and 1.53 ± 2.47 mg m^(-3), respectively, in manufacturing workers. The mean concentration for As in administrative workers was 0.07 ± 0.02 mg m^(-3). After controlling for confounders, the abnormalities of FVC% predicted and FEV_1% predicted were significantly associated with the respirable Si dust among cement workers (OR = 6.913; CI = 1.965-24.322 and OR = 18.320; CI = 3.078-109.027). FENO concentrations in administrative workers were significantly influenced by the exposure to respirable Si dust (R^2 = 0.584, p = 0.006). Manufacturing workers had a high probability of getting cancer due to Si exposure in cement respirable dust at 29.81 × 10^(-4) times compared to administrative workers at 4.14 × 10^(-4) times. After reducing for control factors, the probability of manufacturing workers reduced to 0.45 × 10^(-4) times. As and Cr (VI) dust exposures among cement workers had a probability of cancer risk of 7.49 × 10^(-4) and 44.09 × 10^(-4) times, respectively, after reducing for control factors. The non-cancerous disease risk of the workers from exposure to cement mineral dust exceeded the acceptance limit (HQ ＞ 1). Cement workers were at high risk of developing cancerous and non-cancerous diseases due to exposure while working. Cement workers were highly exposed to respirable Si, As, and Cr dust above the permissible exposure limit.
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A cross-sectional study of 470, 14-year-old students from 8 secondary schools located in sub-urban and urban areas in Hulu Langat district, Selangor, Malaysia was undertaken to determine the impact of atmospheric indoor air pollutants on atopy, asthma, respiratory symptoms and lung inflammation among school children. The students were surveyed using ISAAC and ECRHS questionnaires, their FeNO levels were measured and allergic skin prick tests were conducted. Active and passive sampling was used to measure the classroom indoor air concentration of NO_2, CO_2, formaldehyde, PM_(10), PM_(2.5), temperature and relative humidity. Linear mixed model, two-levels multiple logistic regression, PCA and SPC were applied to determine the complex relationship between respiratory symptoms, personal factors, FeNO levels and atmospheric indoor pollutants. 20.6% of students reported daytime breathlessness and 55.5% reported having rhinitis in the last 12 months. Atopy was prevalent in 57.7% of students, with predominant sensitization to Derp1 (51.9%) and Derf1 (47.9%) among doctor's diagnosed asthmatic students. Indoor air pollutants in urban area schools were significantly higher than those in sub-urban areas (p ＜ 0.001). There was a significant association between exposure to PM_(10) (OR = 2.66, 95% CI: 1.33-5.30) with skin allergy symptoms in the past 12 months. The PCA suggested that the most prominent factor associated with increasing FeNO levels was PM_(10), with 73.5% of the variation. SPC predicted the pattern of FeNO at an upper confidence limit (UCL) of 104.21 ppb with increasing PM_(10) concentration in the classroom (UCL = 40.23 μg m^(-3)). Exposure to PM_(10) and PM_(2.5) significantly influenced the inflammation of the school children's lungs. Moreover, there were associations between self-reported wheezing, daytime and nocturnal attack of breathlessness with doctor's diagnosed asthma among school children.
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Since the 1950s, awareness of the impact of air pollution on human health has been growing. Of the many recognized air pollutants, suspended particulate matter has received the most attention, as both PM_(2.5) and PM_(10) can affect humans upon inhalation. Consequently, PM monitoring is critical to linking indoor pollution and exposure, and a validated measuring instrument is essential. Portable monitors, which track temporal changes in the aerosol mass concentration in real time, are a faster alternative to offline gravimetric techniques, which provide only averaged values. Hence, this study evaluated the performance of the DustTrak DRX aerosol monitor in assessing indoor air quality and validated its ability to measure complex aerosols. Three DustTrak units were used to measure different aerosols, e.g., ambient air, polystyrene latex (PSL) spheres, and environmental tobacco smoke (ETS), and the results were compared to those obtained with the standard gravimetric method. Notably, the bias of the DustTrak relative to the gravimetric method for ETS measurements ranged from 2% to 15% when a photometric calibration factor (PCF) of 0.38 was applied. Additionally, the working range of the tested units was established, and the limits of detection and quantification were found to be 5 and 15 μg m^(-3), respectively. Finally, in order to serve as an alternative to the gravimetric method, these instruments must be accredited for PM measurement in accordance with standards such as ISO 17025.
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In this study, a new ejector-porous tube diluter was developed to accurately in situ measure particulate matter at the source, e.g., emissions at coal-fired power plants, and its dilution ratio and particle loss were compared to those of a commercial model. Whereas commercial models supply air to the porous tube diluter (PRD) using a high-pressure compressor, our device replaces the latter with a ring blower, thereby decreasing the power consumption for the same airflow rate. As a demonstration, particle size volume distributions of fly ash at a coal-fired power plant stack were determined for different dilution ratios. PRD flow rates of 10 and 20 L min^(-1) for the commercial diluter produced ~2-μm particle volume concentrations of 382 and 572 μm^3 cm^(-3), respectively, from an initial (undiluted) volume concentration of 756 μm^3 cm^(-3). However, PRD flow rates of 10 and 30 L min^(-1) for the developed device produced ~2-μm particle volume concentrations of 506 and 500 μm^3 cm^(-3), respectively, from an initial volume concentration of 532 μm^3 cm^(-3). These particle loss rates were confirmed through field testing.
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In the past few decades, the transport and deposition of aerosol in the human respiratory tract has been a crucial area of research, resulting in the identification of the toxicity pathways of inhaled pollutants and facilitating the design of efficient drug delivery systems for targeted treatment. Owing to the complexity of the tracheobronchial tree, experimental studies in vivo/in vitro have been extremely limited; hence, detailed data on the airflow and particle dynamics have been obtained predominantly through computational investigations. With rapid advances in medical imaging and computational capacities, sophisticated human tracheobronchial trees that include the 6^(th), 7^(th) or 15^(th) generation have been increasingly described in the literature. However, continued progress in anatomical reconstruction and mathematical idealized modeling, the two most frequently employed approaches to airway modeling, requires a detailed fundamental analysis on the morphology-induced sensitivity of particle-flow partitioning, and particle deposition in the airways. This study combined numerical and experimental investigations on the transport, deposition and partitioning of nanoparticles in the upper tracheobronchial airways. An anatomically realistic airway was reconstructed via CT scans, and a simplified numerical model was developed that incorporated physical irregularities in the trachea and assessed new boundary conditions to simulate air partitioning in the lobar bronchi, and flow and particle dynamics. An experiment measuring the penetration and deposition of sodium chloride (NaCl) nanoparticles in the anatomical and idealized airway models was conducted in parallel, and the results were compared with the computational predictions.