High-speed train (HST) carriages feature high airtightness and passenger density, which increase the risk of airborne pathogen transmission and cross-infection among passengers. In this study, field experiments were conducted in an actual HST carriage using a 3D in vitro respiratory tract model that mimics realistic human airway morphology. Staphylococcus lentus (S. lentus) was employed as a nonpathogenic surrogate to represent airborne pathogens. Using plate culture, 16S rRNA gene sequencing, and quantitative polymerase chain reaction (qPCR), we quantified the exposure of S. lentus in different respiratory tract regions, as well as its deposition on HST interior surfaces (armrests and overhead luggage racks) under varying source strengths and seating distances. We also assessed the changes in the growth of S. lentus over time after respiratory tract deposition, in order to accurately quantify the effective dose that exerts infection. The results showed that viable bacterial exposure across airway regions at 1.2 m was quantified at 4500-5000 colony-forming units (CFU) within 15 min, decreasing to undetectable levels at 5.0 m. Surface deposition of viable S. lentus on armrests and overhead luggage racks decreased consistently with increasing distance from the infectious source. The S. lentus copy count in the oral cavity more than doubled within 12 hours after exposure (from 6.57 & times; 107 to 1.48 & times; 108 copies), and all cells lost culturability within 48 hours. The findings offer data-based support for developing airborne pathogen control strategies in HST environments.

Migrants traveling from plains to Ngari Prefecture, Tibet, China, with an average altitude of over 4500 m, may suffer serious respiratory function deterioration. Regulating the respiratory microbiome by altering residence indoor air microbiome is a potential approach to improve their respiratory health. To investigate the impact of indoor plants on the respiratory bacteria of high-altitude migrants and its effects on respiratory system health, based on 16S rRNA gene sequencing of 56 respiratory samples and 56 indoor air samples from the participants in Ngari, this study analyzed the effects of indoor plants on the respiratory bacteria of Ngari migrants, compared the effects of indoor plants on migrants and local Tibetans, and analyzed the association between plant-related respiratory bacteria changes and health protection. Migrants with different numbers of indoor plants exhibited significant difference in respiratory bacteria beta diversity. Compared to migrants with fewer plants, migrants with more plants had an approximately 23% lower cumulative relative abundance of pathogenic genera in their respiratory dominant genera, and had 10 unique indoor air-respiratory shared core OTUs, some of which belong to plant-related genera. Migrants with different numbers of indoor plants showed greater differences in respiratory bacteria diversity and specific taxa compared to local Tibetans. Migrants with more indoor plants possessed individual unique indoor air-respiratory shared core OTUs that were significantly positively correlated with inspiratory reserve volume or expiratory reserve volume. Overall, indoor plants alter the diversity and composition of migrants' respiratory bacteria, and the changes in composition positively impact on respiratory health and high-altitude adaptability.

BACKGROUND:Indoor bacterial communities may change with altitude because their major contributors, outdoor bacterial communities, vary with altitude. People's health effects from bacteria inhalation exposure can also vary with altitude because human respiratory physiology changes with oxygen content in air. Accordingly, adjusting indoor bacterial communities may help to acclimate newcomers from low-altitude environments to ultrahigh-altitude environments. To lay the groundwork for further research, we aimed to first elucidate the bacterial communities in ultrahigh-altitude residences and the effects of altitude on these communities. We collected 187 environmental samples from residential communities at ultrahigh altitudes of 3811-4651 m in Ngari, China and sequenced bacterial 16S rRNA genes. RESULTS:On one hand, when abundant genera in ultrahigh-altitude residences and those reported by previous studies on low-altitude residences were compared, nine genera were shared, whereas other five genera were abundant only at ultrahigh altitudes. On the other hand, when the bacterial communities of residences at different ultrahigh altitudes were further compared, the bacterial composition in indoor surface samples varied significantly with altitude. The relative abundance of five bacterial genera in indoor air samples and 10 genera and three phyla in indoor surface samples varied monotonically with altitude. CONCLUSIONS:Altitude may be a long-neglected factor that shapes residential bacterial communities and thus warrants attention.

The complexity of indoor particulate exposure intensifies at higher altitudes owing to the increased lung capacity that residents develop to meet the higher oxygen demands. Altitude variations impact atmospheric pressure and alter particulate dynamics in ambient air and the human respiratory tract, complicating particulate inhalation. This study assessed the fraction of PM2.5 and PM10 entering small airways. This assessment covered an altitude range from 400 m above sea level to 3650 m, and an in vitro respiratory tract model was used. The experimental results confirmed that with increasing altitude, the penetration fractions of PM2.5 and PM10 significantly increased from 0.133 ± 0.031 and 0.141 ± 0.045 to 0.404 ± 0.159 and 0.353 ± 0.132, respectively. Additionally, the computational fluid dynamics simulation results revealed that among particles with sizes of 0.1 to 10 µm, the 7.5-μm particles exhibited the most substantial reduction in deposition in the upper airway, displaying a decrease of 6.27%. Our findings underscore the health risks faced by low-altitude residents during acclimatization to higher altitudes, as they experience heightened exposure to particulate matter sources.

Indoor environment is an important repository of microbiome. Environmental microbiome can influence immune protection through changing the commensal flora of the respiratory tract. The interaction between environment airborne microbiome and human microbiome contributes to human microbial diversity, provides immunomodulatory effects, and thus reduces the risk of respiratory diseases. Lack of immune modulation acquired through microbial exposure may lead to risk of chronic respiratory diseases. Clinical parameters, such as susceptibility, progression, and severity of respiratory disease, are associated with microbial changes. Chronic obstructive pulmonary disease, cystic fibrosis, asthma, and lung cancers are associated with airway microbial dysbiosis. The changes of microbiome during the disease period are mainly characterized by a decrease in overall bacterial diversity, a decrease in the number of commensal bacteria, and an increase in the number of potential pathogenic bacteria. Based on the perception that pathogenic or conditional pathogenic microbiome is responsible for the infection and transmission of respiratory and non-respiratory diseases, public health policies have long favored keeping indoors at lower concentrations of microbiome or even absolutely sterile. However, in the past decade, an in-depth understanding of the microbiology of the environment and human health has shifted researchers’ view of indoor microbiome from a purely pathogenic and infectious negative role to a potentially protective, preventive positive role. Facing with the dual health effects of indoor airborne microbiome, the ideal control strategy should be to increase the microbial diversity and the proportion of beneficial microbiome, while reducing the concentration of pathogenic microbiome for regions, seasons, and sensitive populations. However, there is still no paradigm shift in built environment microbiology due to technical bottlenecks that prevent researchers from establishing a causal relationship between indoor microbiome and health effects. Currently, the types and properties of indoor airborne microbiome are yet to be fully screened and understood. The characteristics of indoor microbiome when they exert health effects are yet to quantify, including microbial metabolization and reproduction in the respiratory tract, corresponding protective effects, and dose-response effects and individual variation in health effects. The answer to the question “What is a healthy indoor air microbial environment”, that is, the characterization of indoor airborne microbiome based on respiratory health effects, is hindered by respiratory microbial sampling, in-depth analysis of microbial data, and the accuracy of in vitro experiments. Subsequent research needs to focus on the development of the following techniques: Microbial sampling tools with low invasiveness, high efficiency and low cost; statistical tools with complex source identification, interference factor quantification and causal relationship judgment functions; and experimental tools capable of simulating real, complex respiratory environments and revealing molecular mechanisms of action in vivo. “What is a healthy indoor air microbial environment” will gradually become clear as these questions are resolved. A clear and quantitative mechanism will serve as a scientific basis to guide the improvement of indoor microbial control standards and the rational use of practical interventions.

Particles deposited on mucosa or penetrating into lower airway are two exposure routes. Quantifying administered dose of these two routes gives us idea for future advanced individual protection. Here, we report an in-vitro method to assess the administered doses of eyes, lips, and lower airway. A CT scanning and 3D-printing based human replica is developed, and exposed in front of the 0.6-5μm monodispersed fluorescent particles. At small size particles (<2.5 μm), the administered dose intensity of penetrating into lower airway inhalation (~59.41×10-2 g/g, 0.6μm) is higher than that of eyes and lips (~5.97×10-2 g/g, 0.6μm). Conversely, the administered dose intensity of lower airway inhalation (~9.39×10-2 g/g) becomes higher than that of eyes and lips (~6.24×10-2 ) g/g at 5.0μm particles. This work provides us an effective and economical way to assess exposure risks of particulate contaminants.

Background Aerosol-generating procedures such as oesophagogastroduodenoscopy (OGD) result in infectious particles being exhaled by patients. This substantially increases the medical staff’s risk of occupational exposure to pathogenic particles via airway inhalation and facial mucosal deposition. Infectious particles are regarded as a key route of transmission of SARS-CoV-2 and, thus, represents a major risk factor for medical staff during the ongoing COVID-19 pandemic. There is a need for quantitative evidence on medical staff’s risk of multiroute exposure to infectious particles exhaled by patients during OGD to enable the development of practical, feasible and economical methods of risk-reduction for use in OGD and related procedures. This randomised controlled trial (RCT)—Personal protective EquiPment intervention TrIal for oesophagogastroDuodEnoscopy (PEPTIDE)—aims to establish a state-of-the-art protocol for quantifying the multiroute exposure of medical staff to infectious particles exhaled by patients during real OGD procedures. Method and analysis PEPTIDE will be a prospective, two-arm, RCT using quantitative methods and will be conducted at a tertiary hospital in China. It will enrol 130 participants (65 per group) aged over 18. The intervention will be an anthropomorphic model with realistic respiratory-related morphology and respiratory function that simulates a medical staff member. This model will be used either without or with a surgical mask, depending on the group allocation of a participant, and will be placed beside the participants as they undergo an OGD procedure. The primary outcome will be the anthropomorphic model’s airway dosage of the participants’ exhaled infectious particles with or without a surgical mask, and the secondary outcome will be the anthropomorphic model’s non-surgical mask-covered facial mucosa dosage of the participants’ exhaled infectious particles. Analyses will be performed in accordance with the type of data collected (categorical or quantitative data) using SPSS (V.26.0) and RStudio (V.1.3.959). Ethics and dissemination Ethical approval for this RCT was obtained from the Ethics Committee of Peking Union Medical College Hospital (ZS-3377). All of the potential participants who agree to participate will provide their written informed consent before they are enrolled. The results will be disseminated through presentations at national and international conferences and publications in peer-reviewed journals. Trial registration number NCT05321056 .

Indoor air quality is an important health factor as we spend more than 80% of our time indoors. The primary type of indoor pollutant is particulate matter, high levels of which increase respiratory disease risk. Therefore, air purifiers are a common choice for addressing indoor air pollution. Compared with traditional filtration purifiers, negative ion air purifiers (NIAPs) have gained popularity due to their energy efficiency and lack of noise. Although some studies have shown that negative ions may offset the cardiorespiratory benefits of air purifiers, the underlying mechanism is still unclear. In this study, we conducted a full-scale experiment using an in vitro airway model connected to a breathing simulator to mimic inhalation. The model was constructed using computed tomography scans of human airways and 3D-printing technology. We then quantified the effects of NIAPs on the administered dose of 0.5–2.5 μm particles in the small airway. Compared with the filtration purifier, the NIAP had a better dilution effect after a 1-h exposure and the cumulative administered dose to the small airway was reduced by 20%. In addition, increasing the negative ion concentration helped reduce the small airway exposure risk. NIAPs were found to be an energy-efficient air purification intervention that can effectively reduce the small airway particle exposure when a sufficient negative ion concentration is maintained.

Ngari Prefecture, Tibet, China, features its ultrahigh altitude above 4200 m, very little annual precipitation and extremely low relative humidity. Residents who have migrated to Tibet from the plains use indoor humidification to reduce the respiratory discomfort caused by prolonged exposure to dry indoor air. In this study, field investigations and analysis of residential indoor environments and humidification methods in Ngari Prefecture revealed that ninety-eight percent of humidifier consumers in the prefecture used low-cost ultrasonic humidifiers filled with indoor tap water. The results revealed that the arsenic (As) concentration of the tap water was 41.6 μg/L, over four times China's standards for drinking water quality (10 μg/L). The source As concentration in the air humidified by the tap water-filled ultrasonic humidifier is (619.8 ± 59.1) (ng/m3 ·air), while no As was detected in the air humidified by the evaporative humidifier. For ultrasonic humidifier with tap water-filled, the inhalation dose of a healthy adult was 45.4 ng/d. The minute ventilation volume of migrated residents who had been in Ngari for less than two years (12.5 ± 4.3 L/min) was greater than those of the long-term residents (10.0 ± 4.5 L/min), which may exacerbate the short-term inhalation exposure risk for migrated residents. To reduce the health risks associated with As exposure, evaporative humidifiers are recommended for households using domestic water. If ultrasonic humidifiers are used, the tap water must be purified with terminal filters.

建筑室内表面常见含不同微生物的液滴.已有研究往往将微生物液滴过度简化为纯水或盐溶液液滴,以体现环境湿度和组分中吸湿性盐离子等化学组分对蒸发速率的影响.本研究选择了通过测量浓度为107 CFU/ml的3种室内环境中的常见细菌所在液滴在室内常见表面上蒸发时的质量及接触角的变化,系统研究了细菌属种对液滴蒸发率、接触角等参数的量化影响.测量发现,同等条件下,在0.9％(w/v)氯化钠溶液液滴中加入不同微生物后,类干酪乳杆菌和大肠埃希氏杆菌可以降低蒸发率,延长蒸发时间约50％ ～60％;枯草芽孢杆菌提高蒸发率,缩短蒸发时间约20％.实验结果表明芽孢能够显著提高液滴的液面张力;微生物的存在使液滴在空气中的悬浮时间变长,预示着更大的空气扩散危险及室内环境的污染.

Background: Lack of quantification of direct and indirect exposure of ophthalmologists during ophthalmic diagnostic process makes it hard to estimate the infectious risk of aerosol pathogen faced by ophthalmologists at working environment. Methods: Accurate numerical models of thermal manikins and computational fluid dynamics simulations were used to investigate direct (droplet inhalation and mucosal deposition) and indirect exposure (droplets on working equipment) within a half-minute procedure. Three ophthalmic examination or treatment scenarios (direct ophthalmoscopic examination, slit-lamp microscopic examination, and ophthalmic operation) were selected as typical exposure distance, two breathing modes (normal breathing and coughing), three levels of ambient RH (40, 70, and 95%) and three initial droplet sizes (50, 70, and 100 μm) were considered as common working environmental condition. Results: The exposure of an ophthalmologist to a patient's expiratory droplets during a direct ophthalmoscopic examination was found to be 95 times that of a person during normal interpersonal interaction at a distance of 1 m and 12.1, 8.8, and 9.7 times that of an ophthalmologist during a slit-lamp microscopic examination, a surgeon during an ophthalmic operation and an assistant during an ophthalmic operation, respectively. The ophthalmologist's direct exposure to droplets when the patient cough-exhaled was ~7.6 times that when the patient breath-exhaled. Compared with high indoor RH , direct droplet exposure was higher and indirect droplet exposure was lower when the indoor RH was 40%. Conclusion: During the course of performing ophthalmic examinations or treatment, ophthalmologists typically face a high risk of SARS-CoV-2 infection by droplet transmission.

Coronaviruses are a common class of respiratory viruses that can cause human infections. 2019 novel coronavirus(2019-nCoV), a new coronavirus that has recently caused a pandemic, has affected millions of people and put tremendous pressure on the health systems of almost every country in the world. Coronaviruses are known to spread from person to person through droplets or contact. The 2019-nCoV has also been found in the conjunctival secretions and tears of some clinically diagnosed patients. To assess whether the eye is one of the transmission routes of the virus, we review literature, and summarize the anatomy of the eye-nose pathway, the expression of the virus receptor in the eye, the preclinical animal studies, and the clinical data. We analyze the possibility of eyes as a means of transmission and propose some suggestions of ocular protection. (Chin J Ophthalmol, 2021, 57: 305-310).

Exposure to particulate contaminants can cause serious adverse health effects. Deposition on the facial mucosa is an important path of exposure, but it is difficult to conduct direct dose measurement on real human subjects. In this study, we propose an in vitro method to assess the administered doses of micron-sized particles on the eyes and lips in which computed tomographic scanning and three-dimensional printing were used to create a model that includes a face, oropharynx, trachea, the first five generations of bronchi, and lung volume. This realistic model of a face and airway was exposed to monodispersed fluorescent particles released from an incoming jet. The administered dose of particles deposited upon the eyes and lips, as quantified by fluorescence intensity, was determined via a standard wiping protocol. The results show that, in this scenario, the administered doses normalized by source were 2.15%, 1.02%, 0.88%, 2.13%, and 1.55% for 0.6-, 1.0-, 2.0-, 3.0-, and 5.0-µm particles, respectively. The administered dose of large particles on the mucosa within a given exposure time has great significance. Moreover, the lips suffer a much greater risk of exposure than the eyes and account for more than 80% of total facial mucosa deposition. Our study provides a fast and economical method to assess the administered dose on the facial mucosa on an individual basis.

本文采用数值模拟方法对工业建筑中短时间散发的高温颗粒物在近壁区的扩散规律进行研究,明确了不同粒径的高温颗粒污染物的温度、速度变化,阐明了颗粒物与气流跟随性的差异.结果 表明在扩散过程部分颗粒物会与气流分离呈现出与周围气流相反的运动状态,粒径d=20 μm和30 μm的颗粒物表现的更为显著,其在运动过程中具有最大上升高度,粒径d=30 μm的颗粒物脱离气流的比例高达33.61％,粒径d=1 μm,5μm和10 μm的颗粒物可以随气流上升到厂房顶部.颗粒物在水平方向上的扩散半径随粒径的减小呈现增大趋势.扩散边缘区域的颗粒物较易脱离气流.

The efficient removal of droplets with different ventilation systems is a key scientific problem affecting an indoor environment. In this study the transport of monodispersed droplets generated from an open tank with a large length/width ratio was investigated under the influence of an upper-receiving ventilation (URV) system and a push-pull ventilation (PPV) system, based on numerical simulation. The movement of droplets under the two systems were compared. The effects of the initial diameters of the droplets and the exhaust airflow velocity on the capture efficiency and removal rate of droplets were evaluated. The results showed that the turbulence dispersion of droplets, gravity acting on the droplets and vortex interaction contributed to the different droplet behaviour under different local ventilation modes and exhaust airflow velocities. The PPV system demonstrated faster droplet removal ability than the URV system, for the same size of droplets. The URV system achieved higher capture efficiency with less energy consumption than the PPV system for droplets with an initial diameter of 10-50 mu m; for those with an initial diameter of 75-100 mu m, the PPV system prevented any droplets from escaping into the occupied zone with less energy cost. The results of this study can contribute to the design and selection of local ventilation modes and the operation conditions required to control droplets. (C) 2019 Elsevier B.V. All rights reserved.

Hot particles produced at much higher temperatures than ambient are very common in industrial production. The presence and movement of such contaminants in buildings may cause great harm both to the indoor air quality and human health. The movement characteristics and residence times of such hot particles could help us evaluate their potential to cause harm, thereby assisting the development of a precision control design. The present study focuses on investigating the movement of a single hot particle in two typical (free-falling and rising) industrial processes. A numerical model based on a function compilation and dynamic mesh is developed to perform the dynamic variation analysis. The airflow distribution around the hot particle is discussed, and the velocity and drag force for a hot particle and room-temperature particle are compared. The movement characteristics and residence time of the particle will thus become available eventually. Results show that the air flowing around the hot particle will get heated due to the temperature difference between the hot particle and its surroundings. The heated air hinders the free-falling process but plays a promoting role during the rising movement. In comparison with a particle with room temperature, the hot particle, therefore, has a larger drag force and smaller velocity during the free-falling process whereas the reverse condition is observed in the rising process. The slower velocity attenuation allows the hot particle to move further during the rising process, while the small value of acceleration leads to the particle falling slowly. The residence time for the hot particle thus gets prolonged, causing greater harm to human health.

High-temperature particles that are transiently produced at large concentrations become common contaminants in industrial buildings, and cause significant harm to worker health and indoor air quality. Along with high temperature particle movement, ambient air will be heated and the airflow velocity distribution will change accordingly. Some particles will separate with the airflow, depending on the air velocity around particles and particle diameters. Therefore, different dispersion modes will occur. This study developed a numerical model to investigate particle dispersion in industrial buildings. Three dispersion modes were studied, with a consideration of the influence of initial temperature (T-0) and particle diameter (d(p)). Particles with higher T-0 and smaller d(p) (T-0 = 673 K; and 1 mu m <= d(p) <= 10 mu m, respectively) were associated with significant horizontal diffusion. This included the movement of most particles within the upper space. Particles with either a larger a, and higher T-0, or smaller d(p) and lower T-0 (T-0 = 673 K, d(p) = 30 pm and 293 K <= T-0 <= 373 K, d(p) = 10 mu m), experienced the least horizontal diffusion. Upward transport was limited, with the majority of the particles staying at lower levels. Particles for which T-0 and d(p) ranged from T-0 = 673 K, 10 mu m <= d(p) <= 20 mu m and 473 K <= T-0 <= 573 K, d(p) = 10 gm, respectively, experienced moderate horizontal diffusion. Most particles moved in the upper-middle space and spent the longest time in the vertical direction. Our conclusions inform future studies focusing on human protection and ventilation system design.

The effects of three factors (i.e., drop height h, hopper outlet diameter do, and material temperature 7) on the dust generation rate derived from a free falling particle stream were investigated via full factorial experiments. The correlation between the three factors and dust generation rate was also analysed. Results show that T and h affect the first fugitive dust rate largely, whereas the second fugitive dust rate is mainly dominated by h and do. Through analysing the first fugitive dust percentage data, it is found that h and T should be considered first for higher temperatures and lower flow rates, whereas h and do can be considered.under contrasting conditions, and h should be controlled in the remaining two sets of conditions. Relationships between the influencing factors and total and first fugitive dust rates were developed via multiple regression to quantify the dust emission rates for different contact surfaces (rigid or water). (C) 2017 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

To illustrate the mechanism of dust emission during the industrial materials transfer process in industrial buildings,experimental investigation on the particle behavior of free falling particle stream collision process was conducted using a high speed camera.The software PCC2.14 was used to analyze the images.Results indicate that the centerline velocity of the particle stream monotonically increased from stable regime to transitive regime,increasing first and then decreasing from the transitive regime to the dispersive regime.The dimensionless dispersive diameter of the stream has a linear relationship to the dimensionless falling height and the empirical equation is obtained.The ratio between particle stream core diameter and falling disperse diameter decreased as the drop height increased,and increased as the drop outlet increased.The ratio could be used to analyze the variation of flow regimes quantitatively.The research provided initial condition for the collide process study.Thus the particle disperse could be predicted and controlled.It is important for improving the working environment condition and managing the dust from the bulk material transport system.