Microorganisms associated particulate matter: a preliminary study

Impact of haze on potential pathogens in surface bioaerosol in urban environments

Air quality considerably affects bioaerosol dynamics within the atmosphere. Frequent haze events, with their associated alterations in bioaerosol composition, may pose potential health risks. This study investigated the microbial diversity, community structure, and factors of PM2.5 within an urban environment. We further examined the impact of haze on potentially pathogenic bacteria in bioaerosols, and analyzed the sources of haze pollution. Key findings revealed that the highest levels of microbial richness and diversity were associated with lightly polluted air conditions. While the overall bacterial community structure remained relatively consistent across different air quality levels, the relative abundance of specific bacterial taxa exhibited variations. Meteorological and environmental conditions, particularly sulfur dioxide, nitrogen dioxide, and carbon monoxide, exerted a greater influence on bacterial diversity and community structure compared to the physicochemical properties of the PM2.5 particles themselves. Notably, haze events were observed to strengthen interactions among airborne pathogens. Stable carbon isotope analysis suggested that coal combustion and automobile exhaust were likely to represent the primary source of haze during winter months. These findings indicate that adoption of clean energy alternatives such as natural gas and electricity, and the use of public transportation, is crucial to mitigate particle and harmful pollutant emissions, thereby protecting public health.

Bioaerosols in the atmosphere: A comprehensive review on detection methods, concentration and influencing factors

In the past few decades, especially since the outbreak of the coronavirus disease (COVID-19), the effects of atmospheric bioaerosols on human health, the environment, and climate have received great attention. To evaluate the impacts of bioaerosols quantitatively, it is crucial to determine the types of bioaerosols in the atmosphere and their spatial-temporal distribution. We provide a concise summary of the online and offline observation strategies employed by the global research community to sample and analyze atmospheric bioaerosols. In addition, the quantitative distribution of bioaerosols is described by considering the atmospheric bioaerosols concentrations at various time scales (daily and seasonal changes, for example), under various weather, and different underlying surfaces. Finally, a comprehensive summary of the reasons for the spatiotemporal distribution of bioaerosols is discussed, including differences in emission sources, the impact process of meteorological factors and environmental factors. This review of information on the latest research progress contributes to the emergence of further observation strategies that determine the quantitative dynamics of public health and ecological effects of bioaerosols.

An Assessment of Human Opportunistic Pathogenic Bacteria on Daily Necessities in Nanjing City during Plum Rain Season

The plum rain season is a special climatic phenomenon in east Asia, which is characterized by persistent rainfall, a high temperature, and humidity, providing suitable environmental conditions for certain pathogenic bacteria, thus increasing the incidence of respiratory, gastrointestinal, and urinary diseases. However, studies on human opportunistic pathogenic bacteria communities during the plum rain season are still limited. In this study, the characteristics of human opportunistic pathogenic bacterial communities on daily necessities during the non-plum and plum rain seasons were investigated using high-throughput sequencing technology. The results revealed that the relative abundance of human opportunistic pathogenic bacteria was higher in the plum rain season (cotton cloth: 2.469%, electric bicycles: 0.724%, rice: 3.737%, and washbasins: 5.005%) than in the non-plum rain season (cotton cloth: 1.425%, electric bicycles: 0.601%, rice: 2.426%, and washbasins: 4.801%). Both temperature and relative humidity affected human opportunistic pathogenic bacterial communities. Stochastic processes dominated the assembly process of human opportunistic pathogenic bacterial communities, and undominated processes prevailed. The stability of the co-occurrence network was higher in the non-plum rain season than that in the plum rain season. In addition, the proportion of deterministic processes showed the same trend as the complexity of the co-occurrence network.

Clearing the Air: Understanding the Impact of Wildfire Smoke on Asthma and COPD

Wildfires are a global natural phenomenon. In North America, wildfires have not only become more frequent, but also more severe and longer in duration, a trend ascribed to climate change combined with large fuel stores left from modern fire suppression. The intensification of wildfire activity has significant implications for planetary health and public health, as exposure to fine particulate matter (PM2.5) in wildfire smoke is linked to adverse health effects. This review focuses on respiratory morbidity from wildfire smoke exposure. Inhalation of wildfire PM2.5 causes lung injury via oxidative stress, local and systemic inflammation, airway epithelium compromise, and increased vulnerability to infection. Wildfire PM2.5 exposure results in exacerbations of pre-existing asthma and chronic obstructive pulmonary disease, with an escalation in healthcare utilization, including emergency department visits and hospitalizations. Wildfire smoke exposure may be associated with asthma onset, long-term impairment of lung function, and increased all-cause mortality. Children, older adults, occupationally-exposed groups, and possibly women are the most at risk from wildfire smoke. Future research is needed to clarify best practices for risk mitigation and wildfire management.

Environmental determinants and demographic influences on global urban microbiomes, antimicrobial resistance and pathogenicity

Urban microbiome plays crucial roles in human health and are related to various diseases. The MetaSUB Consortium has conducted the most comprehensive global survey of urban microbiomes to date, profiling microbial taxa/functional genes across 60 cities worldwide. However, the influence of environmental/demographic factors on urban microbiome remains to be elucidated. We collected 35 environmental and demographic characteristics to examine their effects on global urban microbiome diversity/composition by PERMANOVA and regression models. PM10 concentration was the primary determinant factor positively associated with microbial α-diversity (observed species: p = 0.004, β = 1.66, R2 = 0.46; Fisher's alpha: p = 0.005, β = 0.68, R2 = 0.43), whereas GDP per capita was negatively associated (observed species: p = 0.046, β = -0.70, R2 = 0.10; Fisher's alpha: p = 0.004, β = -0.34, R2 = 0.22). The β-diversity of urban microbiome was shaped by seven environmental characteristics, including Köppen climate type, vegetation type, greenness fraction, soil type, PM2.5 concentration, annual average precipitation and temperature (PERMANOVA, p < 0.001, R2 = 0.01-0.06), cumulatively accounted for 20.3% of the microbial community variance. Canonical correspondence analysis (CCA) identified microbial species most strongly associated with environmental characteristic variation. Cities in East Asia with higher precipitation showed an increased abundance of Corynebacterium metruchotii, and cities in America with a higher greenness fraction exhibited a higher abundance of Corynebacterium casei. The prevalence of antimicrobial resistance (AMR) genes were negatively associated with GDP per capita and positively associated with solar radiation (p < 0.005). Total pathogens prevalence was positively associated with urban population and negatively associated with average temperature in June (p < 0.05). Our study presents the first comprehensive analysis of the influence of environmental/demographic characteristics on global urban microbiome. Our findings indicate that managing air quality and urban greenness is essential for regulating urban microbial diversity and composition. Meanwhile, socio-economic considerations, particularly reducing antibiotic usage in regions with lower GDP, are paramount in curbing the spread of antimicrobial resistance in urban environments.

Indoor particulate matter induces epigenetic changes in companion atopic dogs

The prevalence of atopic dermatitis (AD) is increasing and environmental factors are receiving attention as contributing causes. Indoor air pollutants (IAPs), especially particulate matter (PM) can alter epigenetic markers, DNA methylation (DNAm). Although DNAm-mediated epigenetic changes have been reported to modulate the pathogenesis of AD, their role at high risk of exposure to PM is still unclear. The study investigated the effects of exposure to IAPs in the development of AD and epigenetic changes through DNAm in companion atopic dogs that share indoor environment with their owners. Dogs were divided into two groups: AD (n = 47) and controls (n = 21). The IAPs concentration in each household was measured for 48 h, and a questionnaire on the residential environment was completed in all dogs. Eighteen dogs with AD and 12 healthy dogs were selected for DNAm analysis. In addition, clinical and immunological evaluations were conducted. The concentrations of PM2.5, PM10, and volatile organic compounds (VOCs) were significantly higher in the AD group. Moreover, there were more significant methylation differences in the LDLRAD4, KHSRP, and CTDSP2 genes in connection with PM10 in AD group compared to the controls. The degree of methylation of the LDLRAD4 and CTDSP2 genes was also correlated with related protein productions. The present study revealed that exposure to high indoor PM can cause epigenetic development of AD by methylation of the LDLRAD4, KHSRP, and CTDSP2 genes in dogs. Under the concept of "One Health," improving indoor environments should be considered to prevent the development of AD.

Differential Pattern of Cell Death and ROS Production in Human Airway Epithelial Cells Exposed to Quinones Combined with Heated-PM2.5 and/or Asian Sand Dust

The combined toxicological effects of airborne particulate matter (PM), such as PM2.5, and Asian sand dust (ASD), with surrounding chemicals, particularly quinones, on human airway epithelial cells remain underexplored. In this study, we established an in vitro combination exposure model using 1,2-naphthoquinones (NQ) and 9,10-phenanthroquinones (PQ) along with heated PM (h-PM2.5 and h-ASD) to investigate their potential synergistic effects. The impacts of quinones and heated PM on tetrazolium dye (WST-1) reduction, cell death, and cytokine and reactive oxygen species (ROS) production were examined. Results revealed that exposure to 9,10-PQ with h-PM2.5 and/or h-ASD dose-dependently increased WST-1 reduction at 1 μM compared to the corresponding control while markedly decreasing it at 10 μM. Higher early apoptotic, late apoptotic, or necrotic cell numbers were detected in 9,10-PQ + h-PM2.5 exposure than in 9,10-PQ + h-ASD or 9,10-PQ + h-PM2.5 + h-ASD. Additionally, 1,2-NQ + h-PM2.5 exposure also resulted in an increase in cell death compared to 1,2-NQ + h-ASD and 1,2-NQ + h-PM2.5 + h-ASD. Quinones with or without h-PM2.5, h-ASD, or h-PM2.5 + h-ASD significantly increased ROS production, especially with h-PM2.5. Our findings suggest that quinones, at relatively low concentrations, induce cell death synergistically in the presence of h-PM2.5 rather than h-ASD and h-PM2.5 + h-ASD, partially through the induction of apoptosis with increased ROS generation.

Air pollution-associated shifts in the human airway microbiome and exposure-associated molecular events

Publications addressing air pollution-induced human respiratory microbiome shifts are reviewed in this article. The healthy respiratory microbiota is characterized by a low density of bacteria, fungi and viruses with high diversity, and usually consists of Bacteroidetes, Firmicutes, Proteobacteria, Actinobacteria, Fusobacteria, viruses and fungi. The air's microbiome is highly dependent on air pollution levels and is directly reflected within the human respiratory microbiome. In addition, pollutants indirectly modify the local environment in human respiratory organs by reducing antioxidant capacity, misbalancing proteolysis and modulating inflammation, all of which regulate local microbiomes. Improving air quality leads to more diverse and healthy microbiomes of the local air and, subsequently, residents' airways.

Fog-Induced Alteration in Airborne Microbial Community: a Study over Central Indo-Gangetic Plain in India

Fog supports an increase in airborne microbial loading by providing water with nutrients and protecting it from harmful incoming solar radiation. To improve our present understanding of fog-induced alteration in an atmospheric microbial community, a study was conducted during 1 to 14 January 2021 for continuous investigation of airborne bacteria over a rural site, Arthauli (25.95°N, 85.10°E), in central Indo-Gangetic Plain (IGP) in India. An increase of 36% ± 0.4% in airborne bacterial loading was noticed under fog versus prefog conditions, and a decrease of 48% ± 0.4% was noticed under the postfog condition. Airborne bacterial loading had a strong correlation with RH (R2 = 0.56; P < 0.05), temperature (R2 = -0.55, P < 0.05), and wind speed (R2 = -0.52, P < 0.05). Unique types of bacteria, representing about 29% of the whole community, were detected only under foggy conditions, likely by a continuous supply of nutrients and water from a cold, calm, and humid atmosphere. As a result, no significant diurnal variation of bacterial loading was noticed on a foggy day, with a higher daily mean concentration of about (8.4 ± 1.7) × 105 cells · m-3 than that on a typical winter day [(6.3 ± 3.8) × 105 cells · m-3]. A typical winter day experienced about a 60% decrease in bacterial loading in the afternoon in comparison to that in the morning. A 3-day back-trajectory analysis suggests a slow movement of airmass along with the wind blowing from west to central IGP. Fog pauses wind movement, which reduces continuous transportation of urban sources while increasing airborne bacteria from local sources. The abundances of Gp6 (14.8% ± 8.6%), Anaeromyxobacter (7.1% ± 2.8%), and Gp7 (6.8 ± 2.6%) have been observed to increase due to occurrences of fog over central IGP. IMPORTANCE Fog was investigated in the present study as a cause of alteration in the airborne microbial community. Occurrences of fog were responsible for an increase in airborne microbial loading (36%) over central IGP in India due to the easy availability of nutrients and water in the air and dimming of harmful solar radiation. More than 90% of unique bacteria were detected under fog (64%) and postfog (28%) conditions. A few bacteria, like Gp18 (0.5% ± 0.3%), Alicyclobacillus (0.5% ± 0.1%), Sinomonas (0.4% ± 0.2%), and Phenylobacterium (0.4% ± 0.2%), were detected only under foggy conditions. A strong correlation between meteorological parameters and bacterial loading was found in the current research work. The present study provides additional support toward a new direction in interdisciplinary science for the detailed investigations of the effects of meteorological conditions on airborne bacteria and their implications for society.

Association between ambient air pollution exposure during pregnancy and gestational diabetes mellitus: a meta-analysis of cohort studies

Numerous studies have evaluated the association between air pollution and gestational diabetes mellitus (GDM), but the findings were inconsistent. This meta-analysis aimed to provide higher grade evidence on the association of air pollution with GDM based on previous studies. PubMed, Web of science, China National Knowledge Infrastructure (CNKI), and Wanfang Data Knowledge Service Platform (Wanfang) were searched comprehensively up to September 2021. Totally, 20 eligible cohort studies were finally included, for which the pooled RR and 95% CIs were estimated. Stratified analyses by study regions and units of pollutant increase were conducted for further investigation. Sensitivity analyses were also performed to assess the robustness. The finding showed that PM_2.5, PM₁₀, NO₂, and SO₂ exposure increased the risk of GDM, while O₃ exposure reduced GDM risk. Specifically, PM_2.5 exposure in the first and second trimesters, NO₂ and SO₂ exposure in the first trimester significantly increased the risk of GDM, with the RR ranging from 1.015 to 1.032. In addition, the elevation of GDM risk induced by PM_2.5, PM₁₀, and O₃ exposure was more pronounced in Asian subjects than in American subjects. The meta-analysis provides high-quality evidence on the effect of maternal air pollution exposure on GDM in each exposure period.

Levels, distributions and influential factors of residential airborne culturable bacteria in 12 Chinese cities: Multicenter on-site survey among dwellings

Residential airborne culturable bacteria (RAB) are commonly used to assess indoor microbial loads, which is a very effective and recognized indicator of public concern about residential air quality. Many countries and organizations have set exposure limits for residential bacteria. Nevertheless, few studies have been conducted in multicenter cities about the distribution and influencing factors of RAB. It is a challenge to investigate the distribution of RAB and identify the association between indoor influencing variables and RAB in China. The current finding implied the comparative results from a one-year on-site survey of 12 cities in China. The concentration of RAB ranged from 0 CFU/m³ to 18,078 CFU/m³, with an arithmetic median of 350 CFU/m³. RAB concentrations were more in the warm season than those in the cold season, and were more in the bedrooms than those in the living rooms. Indoor environmental indicators (including PM_2.5 and PM₁₀) showed the mediating role in the process of temperature and relative humidity effects on RAB. . Influential factors including family-related information (income), architectural characteristics (house type, building history, living floor, the layers of window glass, and decoration) and lifestyle behaviors (heating, new furniture, incense-burned, insecticides-used, air condition-used, and plants-growed) were related with the concentration of RAB. This study presents essential data on the distribution of RAB in some Chinese cities, and reveals the residential influential factors that might minimize health risk from RAB.

Characteristics and health effects of particulate matter emitted from a waste sorting plant

Solid waste components can be recycled in waste paper and cardboard sorting plants (WPCSP) through a multistep process. This work collected 15 samples every six days from each of the 9 points selected to study the processes taking place in a WPCSP (135 particulate matter samples total). Examining the concentration and size fraction of particulate matter (i.e., PM₁, PM_2.5 and PM₁₀) in WPCSP is an essential issue to notify policy makers about the health impacts on exposed workers. The major activities for increasing of the concentration of PM in various processing units in the WPCSP, especially in hand-picking routes I and II were related to manual dismantling, mechanical grinding, mechanical agitation, and separation and movement of waste. The results of this work showed that a negative correlation between temperature and particulate matter size followed the order PM₁₀ > PM_2.5 > PM₁. Exposure to PM_2.5 and PM₁₀ in the WPCSP lead to possible risk (HI = 5.561 and LTCRs = 3.41 × 10^-6 to 9.43 × 10^-5 for PM_2.5 and HI = 7.454 for PM₁₀). The exposure duration and the previous concentrations had the most effect on the ILCRs and HQs for PM_2.5 and PM₁₀ in all sampling sites. Hence, because WPCSP are infected indoor environments (I/O ratio > 1), the use of control methods such as isolation of units, misting systems, blower systems equipped with bag houses, protective equipment, a mechanical ventilation system, and additional natural ventilation can reduce the amount of suspended PM, enhance worker safety, and increase the recycling rate.

Association of Chemical Aggregates and Fungal Moieties Affecting Native Environmental Films

Fungi are prevalent microorganisms in environmental films. Their impacts on the film chemical environment and morphology remains poorly defined. Here we present microscopic and chemical analyses fungi impacts to environmental films over long- and short-time scales. We report bulk properties of films accumulated for 2 months (February and March 2019) and 12 months to contrast short and longer-term effects. Bright field microscopy results show that fungi and fungal-associated aggregates cover close to 14% of the surface after 12 months and include significant numbers of large (tens to hundreds of μm in diameter) particles aggregated with fungal colonies. Data acquired for films accumulated over shorter times (2 months) suggest mechanisms that contribute to these longer-term effects. This is important because the film's exposed surface will determine what additional material will accumulate over the ensuing weeks or months. A combination of scanning electron microscopy and energy dispersive X-ray spectroscopy provides spatially resolved maps of fugal hypha and nearby elements of interest. We also identify a "nutrient pool" associated with the fungal hypha which extend orthogonally to the growth direction to ca. 50 μm distances. We conclude that fungi have both short-term and long-term effects on the chemistry and morphology of environmental film surfaces. In short, the presence (or absence) of fungi will significantly alter the films' evolution and should be considered when analyzing environmental film impacts on local processes.

Air- and dustborne fungi in repositories of the National Archive of the Republic of Cuba

This study has as objectives to determine the concentration and diversity of the air- and dustborne mycobiota in seven National Archive of the Republic of Cuba repositories, and to assess the potential risk of biodeterioration that isolated taxa may have. In the indoor and outdoor environmental microbiological samplings a SAS biocollector was used and the indoor/outdoor (I/O) ratio was determined for each repository. The settled dust was collected during six months. Sørensen's coefficient of similarity (QS) was calculated to compare the isolated taxa among the three studied niches (indoor air, dust, outdoor air). The biodegradation potential of the isolated taxa was determined by semi-quantitative tests. The concentrations in the air of repositories with natural cross-ventilation ranged from 225.2-750.3 CFU m-3, while in the Map library with air-conditioning the concentration was significantly lower. The I/O ratios ranged from 0.1-1.7 revealing different environmental qualities. The maximum settled dust load was 22.8 mg/m2/day with a top fungal concentration of 6000 CFU g-1. 14 and eleven genera were detected in the air and dust respectively with predominance of the genera Aspergillus, Cladosporium and Penicillium. A QS of 0.8 was obtained between the indoor and the outdoor environments with eleven taxa similar evidencing the incidence of outdoors on the indoor mycobiota. The isolated taxa showed several biodeteriogenic attributes highlighting twelve and 14 taxa from indoor air and dust respectively with positive results for the five tests performed. This demonstrates the potential risk that fungal environmental represent for the preserved documentary heritage.

Microbial Activity and Community Structure in PM2 .5 at Different Heights in Ground Boundary Layer of Beijing Atmosphere under Various Air Quality Levels

The outbreak of the COVID-19 epidemic is a reminder that aerosols have important health effects as a potential route for disease transmission. Biological components in aerosols (especially PM_2.5 ) may pose potential threats to humans as pathogens and allergens. Research on PM_2.5 and biological components currently focuses mainly on polluted conditions, with less emphasis on clean environments. Sampling has also been primarily based on a single point with a lack of data at different positions. In this study, a modified fluorescein diacetate hydrolysis method was used to measure microbial activity in PM_2.5 at different altitudes over a year in Beijing, China. A high-throughput sequencing method was used to study the microbial community. Results showed that microbial activity 1.5 m (0.0465 ng m^-3 ) above the ground was higher than 31.5 m (0.0348 ng m^-3 ). There was higher microbial activity at both heights during spring. Furthermore, a positive correlation was observed between microbial activity and relative abundance of dominant species. Microbial activity increased during autumn and winter increased alongside the pollution level, but in spring higher levels of microbial activity were observed in excellent or good weather conditions. The results from this study are valuable for further research regarding the biological components of atmospheric PM, the prevention of biological pollution, and establishing a comprehensive air quality evaluation system. This article is protected by copyright. All rights reserved.

Long-Term Studies of Biological Components of Atmospheric Aerosol: Trends and Variability

Background: Biological components of atmospheric aerosol affect the quality of atmospheric air. Long-term trends in changes of the concentrations of total protein (a universal marker of the biogenic component of atmospheric aerosol) and culturable microorganisms in the air are studied. Methods: Atmospheric air samples are taken at two locations in the south of Western Siberia and during airborne sounding of the atmosphere. Sample analysis is carried out in the laboratory using standard culture methods (culturable microorganisms) and the fluorescence method (total protein). Results: Negative trends in the average annual concentration of total protein and culturable microorganisms in the air are revealed over more than 20 years of observations. For the concentration of total protein and culturable microorganisms in the air, intra-annual dynamics is revealed. The ratio of the maximum and minimum values of these concentrations reaches an order of magnitude. The variability of concentrations does not exceed, as a rule, two times for total protein and three times for culturable microorganisms. At the same time, for the data obtained in the course of airborne sounding of the atmosphere, a high temporal stability of the vertical profiles of the studied concentrations was found. The detected biodiversity of culturable microorganisms in atmospheric air samples demonstrates a very high variability at all observation sites. Conclusions: The revealed long-term changes in the biological components of atmospheric aerosol result in a decrease in their contribution to the atmospheric air quality index.

Role of air pollutants in airway epithelial barrier dysfunction in asthma and COPD

Chronic exposure to environmental pollutants is a major contributor to the development and progression of obstructive airway diseases, including asthma and COPD. Understanding the mechanisms underlying the development of obstructive lung diseases upon exposure to inhaled pollutants will lead to novel insights into the pathogenesis, prevention and treatment of these diseases. The respiratory epithelial lining forms a robust physicochemical barrier protecting the body from inhaled toxic particles and pathogens. Inhalation of airborne particles and gases may impair airway epithelial barrier function and subsequently lead to exaggerated inflammatory responses and airway remodelling, which are key features of asthma and COPD. In addition, air pollutant-induced airway epithelial barrier dysfunction may increase susceptibility to respiratory infections, thereby increasing the risk of exacerbations and thus triggering further inflammation. In this review, we discuss the molecular and immunological mechanisms involved in physical barrier disruption induced by major airborne pollutants and outline their implications in the pathogenesis of asthma and COPD. We further discuss the link between these pollutants and changes in the lung microbiome as a potential factor for aggravating airway diseases. Understanding these mechanisms may lead to identification of novel targets for therapeutic intervention to restore airway epithelial integrity in asthma and COPD.

Exposure to air pollution induces airway epithelial barrier dysfunction through several mechanisms including increased oxidative stress, exaggerated cytokine responses and impaired host defence, which contributes to development of asthma and COPD. https://bit.ly/3DHL1CA

Isolation, Characterization, and Antimicrobial Activity of Bacterial and Fungal Representatives Associated With Particulate Matter During Haze and Non-haze Days

Particulate matter (PM) has been a threat to the environment and public health in the metropolises of developing industrial countries such as Beijing. The microorganisms associated with PM have an impact on human health if they are exposed to the respiratory tract persistently. There are few reports on the microbial resources collected from PM and their antimicrobial activities. In this study, we greatly expanded the diversity of available commensal organisms by collecting 1,258 bacterial and 456 fungal isolates from 63 PM samples. A total of 77 bacterial genera and 35 fungal genera were included in our pure cultures, with Bacillus as the most prevalent cultured bacterial genus, Aspergillus, and Penicillium as the most prevalent fungal ones. During heavy-haze days, the numbers of colony-forming units (CFUs) and isolates of bacteria and fungi were decreased. Bacillus, Paenibacillus, and Chaetomium were found to be enriched during haze days, while Kocuria, Microbacterium, and Penicillium were found to be enriched during non-haze days. Antimicrobial activity against common pathogens have been found in 40 bacterial representatives and 1 fungal representative. The collection of airborne strains will provide a basis to greatly increase our understanding of the relationship between bacteria and fungi associated with PM and human health.

Elemental and microbiota content in indoor and outdoor air using recuperation unit filters

This paper presents the results of a twelve-month measurement campaign conducted at a rural single-family house in Poland. The external and internal filters of a recuperator used to mechanically ventilate the building were used to separate the total suspended particles (TSPs), and the concentrations of fifteen elements and abundance of fungi and bacteria were determined. Lower annual mean concentrations were observed indoors, and the concentrations of most elements did not significantly change between seasons. There were some differences between winter and summer, which may have resulted from changes in the ventilation regimes in the house. The number of bacteria was similar outdoors and indoors, while the amounts of fungi were higher indoors (p < 0.05). The order of metal concentrations outdoors agreed well with observations in other countries, while indoors the metal concentrations order indicated the individual characteristics of the building. The species diversity of fungi was higher than that of bacteria, and different species were found indoors and outdoors, while bacteria were typically present both indoors and outdoors. Different TSP sources were identified indoors and outdoors, suggesting limited penetration between the two environments. However, both environments were affected by traffic. Mechanical ventilation systems with built-in filters (such as recuperators) were useful in assessing the air quality within the building, and the changeable recuperation filters offer an approach to assess the air quality in several houses without any additional cost or discomfort to the residents.

Exploring common factors influencing PM2.5 and O3 concentrations in the Pearl River Delta: Tradeoffs and synergies

Particulate matter with an aerodynamic equivalent dimeter less than 2.5 μm (PM_2.5) and ozone (O₃) are major air pollutants, with coupled and complex relationships. The control of both PM_2.5 and O₃ pollution requires the identification of their common influencing factors, which has rarely been attempted. In this study, land use regression (LUR) models based on the least absolute shrinkage and selection operator were developed to estimate PM_2.5 and O₃ concentrations in China's Pearl River Delta region during 2019. The common factors in the tradeoffs between the two air pollutants and their synergistic effects were analyzed. The model inputs included spatial coordinates, remote sensing observations, meteorological conditions, population density, road density, land cover, and landscape metrics. The LUR models performed well, capturing 54-89% and 42-83% of the variations in annual and seasonal PM_2.5 and O₃ concentrations, respectively, as shown by the 10-fold cross validation. The overlap of variables between the PM_2.5 and O₃ models indicated that longitude, aerosol optical depth, O₃ column number density, tropospheric NO₂ column number density, relative humidity, sunshine duration, population density, the percentage cover of forest, grass, impervious surfaces, and bare land, and perimeter-area fractal dimension had opposing effects on PM_2.5 and O₃. The tropospheric formaldehyde column number density, wind speed, road density, and area-weighted mean fractal dimension index had complementary effects on PM_2.5 and O₃ concentrations. This study has improved our understanding of the tradeoff and synergistic factors involved in PM_2.5 and O₃ pollution, and the results can be used to develop joint control policies for both pollutants.

Microbial degradation of pyrene in holm oak (Quercus ilex) phyllosphere: Role of particulate matter in regulating bioaccessibility

In this study we first measured the mineralization of pyrene on leaves of urban holm oak (Quercus ilex) by autochthonous microorganisms and an inoculated PAH degrading bacterium (i.e., Mycobacterium gilvum), selected as a model phyllosphere species, as well as the leaf-water (K_LW) and leaf-air (K_LA) partition coefficients for this chemical. Mineralization was investigated in two different experimental systems in terms of leaf and microorganism environment. Additionally, the influence on pyrene partitioning and mineralization when particulate matter (PM) was present on the leaf surface or removed was studied. Mineralization of ¹⁴C-labeled pyrene by autochthonous microorganisms was lower than 1% after approximately two weeks, while M. gilvum mineralized 5% to 17% of pyrene. These extents corresponded to mineralization half-lives that ranged between ~30 to ~200 days. We proposed that PM present at the leaf surface reduced the accumulation of pyrene by inner compartments (cuticle) distantly located from microbial cells and enhanced the bioaccessibility of pyrene, speeding up microbial activity and therefore mineralization. These results highlight that plant-phyllosphere microorganism interaction is more complex than currently established and deserves additional studies to further comprehend the air purification ecosystem service of phyllosphere microorganisms.

Concentrations, Size Distribution, and Community Structure Characteristics of Culturable Airborne Antibiotic-Resistant Bacteria in Xinxiang, Central China

Antimicrobial resistance is considered an important threat to global health and has recently attracted significant attention from the public. In this study, the concentrations and size distribution characteristics of culturable airborne total bacteria (TB) and four antibiotic-resistant bacteria (tetracycline-resistant bacteria (TRB), ciprofloxacin-resistant bacteria (CRB), erythromycin-resistant bacteria (ERB), and ampicillin-resistant bacteria (ARB)) were investigated for approximately one year to explore their variations under different seasons, diurnal periods, and air quality levels. The concentrations of TB and four antibiotic-resistant bacteria in winter and night were higher than during other seasons and diurnal periods. Their maximum concentrations were detected from air under moderate pollution or heavy pollution. PM2.5, PM10, SO2, and NO2 were positively related to TB and four antibiotic-resistant bacteria (p < 0.01), whereas O3 and wind speed were negatively related to them (p < 0.05). The particle size of TB and four antibiotic-resistant bacteria were mainly distributed in stage V (1.1–2.2 µm). Bacillus was the dominant genus of ARB (75.97%) and CRB (25.67%). Staphylococcus and Macrococcus were the dominant genera of TRB (46.05%) and ERB (47.67%), respectively. The opportunistic pathogens of Micrococcus, Sphingomonas, Enterococcus, Rhodococcus, and Stenotrophomonas were also identified. This study provides important references for understanding the threat of bioaerosols to human health.

Advances on the immunotoxicity of outdoor particulate matter: A focus on physical and chemical properties and respiratory defence mechanisms

Particulate matter (PM) is acknowledged to have multiple detrimental effects on human health. In this review, we report literature results on the possible link between outdoor PM and health outcomes with a focus on pulmonary infections and the mechanisms responsible for observed negative effects. PM physical and chemical properties, such as size and chemical composition, as well as major emission sources are described for a more comprehensive view about the role played by atmospheric PM in the observed adverse health effects; to this aim, major processes leading to the deposition of PM in the respiratory tract and how this can pave the way to the onset of pathologies are also presented. From the literature works here reviewed, two ways in which PM can threaten human health promoting respiratory infectious diseases are mostly taken into account. The first pathway is related to an enhanced susceptibility and here we will also report on molecular mechanisms in the lung immune system responsible for the augmented susceptibility to pathogens, such as the damage of mechanical defensive barriers, the alteration of the innate immune response, and the generation of oxidative stress. The second one deals with the relationship between infectious agents and PM; here we recall that viruses and bacteria (BioPM) are themselves part of atmospheric PM and are collected during sampling together with particles of different origin; so, data should be analysed with caution in order to avoid any false cause-effect relation. To face these issues a multidisciplinary approach is mandatory as also evident from the ongoing research about the mechanisms hypothesized for the SARS-CoV-2 airborne spreading, which is still controversial and claims for further investigation. Therefore, we preferred not to include papers dealing with SARS-CoV-2.

PM2.5 Exacerbates Oxidative Stress and Inflammatory Response through the Nrf2/NF-κB Signaling Pathway in OVA-Induced Allergic Rhinitis Mouse Model

Air pollution-related particulate matter (PM) exposure reportedly enhances allergic airway inflammation. Some studies have shown an association between PM exposure and a risk for allergic rhinitis (AR). However, the effect of PM for AR is not fully understood. An AR mouse model was developed by intranasal administration of 100 μg/mouse PM with a less than or equal to 2.5 μm in aerodynamic diameter (PM_2.5) solution, and then by intraperitoneal injection of ovalbumin (OVA) with alum and intranasal challenging with 10 mg/mL OVA. The effects of PM_2.5 on oxidative stress and inflammatory response via the Nrf2/NF-κB signaling pathway in mice with or without AR indicating by histological, serum, and protein analyses were examined. PM_2.5 administration enhanced allergic inflammatory cell expression in the nasal mucosa through increasing the expression of inflammatory cytokine and reducing the release of Treg cytokine in OVA-induced AR mice, although PM_2.5 exposure itself induced neither allergic responses nor damage to nasal and lung tissues. Notably, repeated OVA-immunization markedly impaired the nasal mucosa in the septum region. Moreover, AR with PM_2.5 exposure reinforced this impairment in OVA-induced AR mice. Long-term PM_2.5 exposure strengthened allergic reactions by inducing the oxidative through malondialdehyde production. The present study also provided evidence, for the first time, that activity of the Nrf2 signaling pathway is inhibited in PM_2.5 exposed AR mice. Furthermore, PM_2.5 exposure increased the histopathological changes of nasal and lung tissues and related the inflammatory cytokine, and clearly enhanced PM_2.5 phagocytosis by alveolar macrophages via activating the NF-κB signaling pathway. These obtained results suggest that AR patients may experience exacerbation of allergic responses in areas with prolonged PM_2.5 exposure.

Survey of background microbial index in inhalable particles in Beijing

As a potential transmission route for diseases, aerosols have an important impact on human health. At present, research concerning the biological components of atmospheric particulate matter (PM) is of increasing interest. However, previous research has mainly focused on serious pollution conditions, creating a knowledge gap regarding background atmospheric microbes. In this study, we observed the atmosphere of Huairou in Beijing for one year, analyzed the characteristics of the physiological metabolic activity of the microorganisms as an index to determine the air quality, and further explored the microbial communities. From January 2018 to January 2019, a total of 157 days of microbial activity data for PM_2.5 and PM₁₀ were obtained through the use of a modified fluorescein diacetate (FDA) hydrolysis method. Our results showed that there was no significant difference between the microbial activity of PM_2.5 and PM₁₀, even though there was significant seasonal variation. At increasing pollution levels, the results showed that the microbial activity decreased at first, and then increased as the conditions worsened. The microbial community of PM_2.5 was analyzed using the high-throughput sequencing method. There were significant seasonal differences in species richness and community diversity of bacteria in PM_2.5, whereas there was variation only in its fungi species richness. Notably, the microbial community dominated by bacteria has a significant influence on microbial activity. From the perspective of microbial community composition, this study uncovered the possible causes of microbial activity variation and identified the key bacteria and fungi. These results will provide a theoretical basis for both improving air biological pollution predictions and ambient air quality evaluations.

Ambient viral and bacterial distribution during long-range transport in Northern Taiwan

Long-range transport (LRT) reportedly carries air pollutants and microorganisms to downwind areas. LRT can be of various types, such as dust storm (DS) and frontal pollution (FP); however, studies comparing their effects on bioaerosols are lacking. This study evaluated the effect of LRT on viral and bacterial concentrations in Northern Taiwan. When LRT occurred and possibly affected Taiwan from August 2013 to April 2014, air samples (before, during, and after LRT) were collected in Cape Fugui (CF, Taiwan's northernmost point) and National Taiwan University (NTU). Reverse-transcription quantitative polymerase chain reaction (RT-qPCR) was applied to quantify influenza A virus. qPCR and qPCR coupled with propidium monoazide were, respectively, used to quantify total and viable bacteria. Types and occurrence of LRT were confirmed according to the changing patterns of meteorological factors and air pollution, air mass sources (HYSPLIT model), and satellite images. Two Asian DS and three FP cases were included in this study. Influenza A virus was detected only on days before and during FP occurred on January 3-5, 2014, with concentrations of 0.87 and 10.19 copies/m³, respectively. For bacteria, the increase in concentrations of total and viable cells during Asian DSs (17-19 and 25-29 November 2013) was found at CF only (from 3.13 to 3.40 and from 2.62 to 2.85 log copies/m³, respectively). However, bacterial levels at NTU and CF both increased during FP and lasted for 2 days after FP. In conclusion, LRT increased the levels of influenza A virus and bacteria in the ambient air of Northern Taiwan, particularly at CF. During and 2 days (at least) after LRT, people should avoid outdoor activities, especially in case of FP.

A Landscape Study of Sediment Formation and Transport in the Urban Environment

Background: Sediment deposition in the urban environment affects aesthetic, economic, and other aspects of city life, and through re-suspension of dust, may pose serious risks to human health. Proper environmental management requires further understanding of natural and anthropogenic factors influencing the sedimentation processes in urbanized catchments. To fill the gaps in the knowledge about the relationship between the urban landscape and sedimentation, field landscape surveys were conducted in the residential areas of the Russian cities of Ekaterinburg, Nizhniy Novgorod, Rostov-on-Don, Tyumen, Chelyabinsk, and Murmansk. Methods: In each city, six elementary urban residential landscapes were chosen in blocks of multi-story apartment buildings typical for Russian cities. The method of landscape survey involved delineating functional segments within the elementary landscapes and describing each segment according to the developed procedure during a field survey. Results: The complexity of sedimentation processes in the urban environment was demonstrated. The following main groups of factors have significant impacts on sediment formation and transport in residential areas in Russian cities: low adaptation of infrastructure to a high density of automobiles, poor municipal services, and bad urban environmental management in the course of construction and earthworks. Conclusion: A high sediment formation potential was found for a considerable portion of residential areas.

PM2.5-associated bacteria in ambient air: Is PM2.5 exposure associated with the acquisition of community-acquired staphylococcal infections?

Particulate matter (PM), a major component of air pollution, is an important carrier medium of various chemical and microbial compounds. Air pollution due to PM could increase the level of bacteria and associated adverse health effects. Staphylococci as important opportunistic pathogens that cause hospital- and community-acquired infections may transmit through air. This study aimed to obtain knowledge about the concentration of airborne bacteria as well as staphylococci associated with particulate matter with a diameter of less than 2.5 micrometers (PM_2.5) in ambient air. The impact of meteorological factors including ultraviolet (UV) index, wind speed, temperature, and moisture on microbial concentrations was also investigated. Quartz filters were used to collect PM_2.5 and associated bacteria in ambient air of a semiarid area. Airborne bacteria were quantified by culture method and Staphylococcus species identified by molecular methods. The mean (SD) concentration of PM_2.5 and airborne bacteria was 64.83 (24.87) µg/m³ and 38 (36) colony forming unit (CFU)/m³, respectively. The results showed no significant correlation between the levels of PM_2.5 and concentrations of bacteria (p < 0.05). Staphylococcus species were detected in 8 of 37 (22%) samples in a concentration from 3 to 213 CFU/m³. S. epidermidis was detected with the highest frequency followed by S. gallinarum and S. hominis, but S. aureus and methicillin-resistant Staphylococcus aureus (MRSA) were not detected. No significant correlation between the concentrations of bacteria with meteorological parameters was observed (p < 0.05). Our finding showed that, although the study area is sometimes subject to air pollution from PM_2.5, the concentration of PM_2.5- associated bacteria is relatively low. According to the results, PM_2.5 may not be a source of community-associated staphylococcal infections.

Airborne bacterial communities of outdoor environments and their associated influencing factors

Microbial entities (such bacteria, fungi, archaea and viruses) within outdoor aerosols have been scarcely studied compared with indoor aerosols and nonbiological components, and only during the last few decades have their studies increased. Bacteria represent an important part of the microbial abundance and diversity in a wide variety of rural and urban outdoor bioaerosols. Currently, airborne bacterial communities are mainly sampled in two aerosol size fractions (2.5 and 10 µm) and characterized by culture-dependent (plate-counting) and culture-independent (DNA sequencing) approaches. Studies have revealed a large diversity of bacteria in bioaerosols, highlighting Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes as ubiquitous phyla. Seasonal variations in and dispersion of bacterial communities have also been observed between geographical locations as has their correlation with specific atmospheric factors. Several investigations have also suggested the relevance of airborne bacteria in the public health and agriculture sectors as well as remediation and atmospheric processes. However, although factors influencing airborne bacterial communities and standardized procedures for their assessment have recently been proposed, the use of bacterial taxa as microbial indicators of specific bioaerosol sources and seasonality have not been broadly explored. Thus, in this review, we summarize and discuss recent advances in the study of airborne bacterial communities in outdoor environments and the possible factors influencing their abundance, diversity, and seasonal variation. Furthermore, airborne bacterial activity and bioprospecting in different fields (e.g., the textile industry, the food industry, medicine, and bioremediation) are discussed. We expect that this review will reveal the relevance and influencing factors of airborne bacteria in outdoor environments as well as stimulate new investigations on the atmospheric microbiome, particularly in areas where air quality is a public concern.

Assessing the relationship between ground levels of ozone (O3) and nitrogen dioxide (NO2) with coronavirus (COVID-19) in Milan, Italy

This paper investigates the correlation between the high level of coronavirus SARS-CoV-2 infection accelerated transmission and lethality, and surface air pollution in Milan metropolitan area, Lombardy region in Italy. For January-April 2020 period, time series of daily average inhalable gaseous pollutants ozone (O3) and nitrogen dioxide (NO2), together climate variables (air temperature, relative humidity, wind speed, precipitation rate, atmospheric pressure field and Planetary Boundary Layer) were analyzed. In spite of being considered primarily transmitted by indoor bioaerosols droplets and infected surfaces or direct human-to-human personal contacts, it seems that high levels of urban air pollution, and climate conditions have a significant impact on SARS-CoV-2 diffusion. Exhibited positive correlations of ambient ozone levels and negative correlations of NO2 with the increased rates of COVID-19 infections (Total number, Daily New positive and Total Deaths cases), can be attributed to airborne bioaerosols distribution. The results show positive correlation of daily averaged O3 with air temperature and inversely correlations with relative humidity and precipitation rates. Viral genome contains distinctive features, including a unique N-terminal fragment within the spike protein, which allows coronavirus attachment on ambient air pollutants. At this moment it is not clear if through airborne diffusion, in the presence of outdoor and indoor aerosols, this protein "spike" of the new COVID-19 is involved in the infectious agent transmission from a reservoir to a susceptible host during the highest nosocomial outbreak in some agglomerated industrialized urban areas like Milan is. Also, in spite of collected data for cold season (winter-early spring) period, when usually ozone levels have lower values than in summer, the findings of this study support possibility as O3 can acts as a COVID-19 virus incubator. Being a novel pandemic coronavirus version, it might be ongoing during summer conditions associated with higher air temperatures, low relative humidity and precipitation levels.

A Review on Airborne Microbes: The Characteristics of Sources, Pathogenicity and Geography

Microbes are widespread and have been much more studied in recent years. In this review, we describe detailed information on airborne microbes that commonly originate from soil and water through liquid–air and soil–air interface. The common bacteria and fungi in the atmosphere are the phyla of Firmicutes, Proteobacteria, Bacteroides, Actinobacteria, Cyanobacteria and Ascomycota, Basidiomycota, Chytridiomycota, Rozellomycota that include most pathogens leading to several health problems. In addition, the stability of microbial community structure in bioaerosols could be affected by many factors and some special weather conditions like dust events even can transport foreign pathogens to other regions, affecting human health. Such environments are common for a particular place and affect the nature and interaction of airborne microbes with them. For instance, meteorological factors, haze and foggy days greatly influence the concentration and abundance of airborne microbes. However, as microorganisms in the atmosphere are attached on particulate matters (PM), the high concentration of chemical pollutants in PM tends to restrain the growth of microbes, especially gathering atmospheric pollutants in heavy haze days. Moreover, moderate haze concentration and/or common chemical components could provide suitable microenvironments and nutrition for airborne microorganism survival. In summary, the study reviews much information and characteristics of airborne microbes for further study.

Concentration, viability and size distribution of bacteria in atmospheric bioaerosols under different types of pollution

Bacteria are important components of bioaerosols with the potential to influence human health and atmospheric dynamics. However, information on the concentrations and influencing factors of viable bacteria is poorly understood. In this study, size-segregated bioaerosol samples were collected from Aug. 2017 to Feb. 2018 in the coastal region of Qingdao, China. The total microbes and viable/non-viable bacteria in the samples were measured using an epifluorescence microscope after staining with the DAPI (4', 6-diamidino-2-phenylindole) and LIVE/DEAD® BacLight™ Bacterial Viability Kit, respectively. The concentrations of non-viable bacteria increased when the air quality index (AQI) increased from <50 to 300, with the proportion of non-viable bacteria to total microbes increasing from (11.1 ± 12.0)% at an AQI of <50 to (18.4 ± 14.7)% at an AQI of >201. However, the concentrations of viable bacteria decreased from (2.12 ± 2.04) × 10⁴ cells·m^-3 to (9.00 ± 1.72) × 10³ cells·m^-3 when the AQI increased from <50 to 150. The ratio of viable bacteria to total bacteria (viability) decreased from (31.0 ± 14.7)% at 0 < AQI<50 to (8.6 ± 1.0)% at 101 < AQI<150 and then increased to (9.6 ± 5.3)% at an AQI of 201-300. The results indicated that the bacterial viability decreased when air pollution occurred and increased again when pollution became severe. The mean size distribution of non-viable bacteria exhibited a bimodal distribution pattern at an AQI<50 with two peaks at 2.1-3.3 μm and >7.0 μm, while the viable bacteria had two peaks at 1.1-2.1 μm and >7 μm. When the AQI increased from 101 to 300, the size distribution of viable/non-viable bacteria varied with an increased proportion of fine particles. The multiple linear regression analysis results verified that the AQI and PM₁₀ had important effects on the concentrations of non-viable bacteria. These results highlight impacts of air pollution on viable/non-viable bacteria and the interactions between complex environmental factors and bacteria interactions, improving our understanding of bioaerosols under air pollution conditions.

Indoor PM2.5, tobacco smoking and chronic lung diseases: A narrative review

The lung is one of the most important organs exposed to environmental agents. People spend approximately 90% of their time indoors, and risks to health may thus be greater from exposure to poor air quality indoors than outdoors. Multiple indoor pollutants have been linked to chronic respiratory diseases. Environmental tobacco smoke (ETS) is known as an important source of multiple pollutants, especially in indoor environments. Indoor PM_2.5 (particulate matter with aerodynamic diameter < 2.5 μm) was reported to be the most reliable marker of the presence of tobacco smoke. Recent studies have demonstrated that PM_2.5 is closely correlated with chronic lung diseases. In this paper, we reviewed the relationship of tobacco smoking and indoor PM_2.5 and the mechanism that underpin the link of tobacco smoke, indoor PM_2.5 and chronic lung diseases.

Feedback of airborne bacterial consortia to haze pollution with different PM2.5 levels in typical mountainous terrain of Jinan, China

Polluted air is as harmful as polluted water sources to public health. As air living organisms, the research on microbial consortia under haze stress with different PM_2.5 levels in a mountainous environment remains very limited. This study investigated the dynamic changes in bacterial cell counts, apoptosis, human pathogens, consortia characteristics, metabolic pathways, and the biochemical functions under haze conditions with various degrees of pollution (leading pollutant PM_2.5) from August to December 2017 in a typical mountainous terrain of Jinan, China. Samples were evaluated with flow cytometry and 16S rRNA gene amplicon sequencing. Results indicated that cell counts ranged from 6.83 × 10⁵ ± 1.27 × 10⁴ (non-polluted air, NP) to 2.32 × 10⁶ ± 3.56 × 10⁴ (heavily polluted air, HP) cell m^-3 air. The proportion of viable apoptotic and necrotic cells were positively correlated to PM_2.5. Burkholderia cenocepacia (36.6%) was the most abundant human pathogen found in HP; this gram-negative bacterium is associated with potentially lethal respiratory infections in cystic fibrosis patients. The relative abundance of the phylum Proteobacteria (63.8%) in NP first decreased in lightly polluted (LP) (41.3%) and moderately polluted air (MP) (26.3%) then increased in HP (81.0%). Cupriavidus (22.9%) and BTEX-degrading bacteria (0.6%, Pseudomonas) were found in HP. Metabolic pathways with significant differences included cell motility and endocrine and immune diseases that exhibited increasing relative abundance as pollution levels increased. The diversity of biochemical functions was found to be decreased in hazy air.

Anemochory of diapausing stages of microinvertebrates in North American drylands

1. Dry, ephemeral, desert wetlands are major sources of windblown sediment, as well as repositories for diapausing stages (propagules) of aquatic invertebrates. Zooplankton propagules are of the same size range as sand and dust grains. They can be deflated and transported in windstorm events. This study provides the evidence that dust storms aid in dispersal of microinvertebrate propagules via anemochory (aeolian transport). 2. We monitored 91 windstorms at six sites in the southwestern U.S. over a 17-year period. The primary study site was located in El Paso, Texas in the northern Chihuahuan Desert. Additional samples were collected from the Southern High Plains region. Dust carried by these events was collected and rehydrated to hatch viable propagules transported with it. 3. Using samples collected over a six-year period, 21 m above the ground which included 59 storm events, we tested the hypothesis that transport of propagules is correlated with storm intensity by monitoring meteorological conditions such as storm duration, wind direction, wind speed, and PM₁₀ (fine dust concentration). An air quality monitoring site located adjacent to the dust samplers provided quantitative hourly measurements. 4. Rehydration results from all events showed that ciliates were found in 92% of the samples, rotifers in 81%, branchiopods in 29%, ostracods in 4%, nematodes in 13%, gastrotrichs in 16%, and tardigrades in 3%. Overall, four bdelloid and 11 monogonont rotifer species were identified from rehydrated windblown dust samples. 5. PCA results indicated gastrotrichs, branchiopods, nematodes, tardigrades, and monogonont rotifer occurrence positively correlated with PM₁₀ and dust event duration. Bdelloid rotifers were correlated with amount of sediment deposited. NMDS showed a significant relationship between PM₁₀ and occurrence of some taxa. Zero-inflated, general linear models with mixed-effects indicated significant relationships with bdelloid and nematode transport and PM₁₀. 6. Thus, windstorms with high particulate matter concentration and long duration are more likely to transport microinvertebrate diapausing stages in drylands.

The association of PM2.5 with airway innate antimicrobial activities of salivary agglutinin and surfactant protein D

Fine particulate matter ≤2.5 μm (PM_2.5) is a prominent global public health risk factor that can cause respiratory infection by downregulating the amounts of antimicrobial proteins and peptides (AMPs). Both salivary agglutinin (SAG) and surfactant protein D (SPD) are important AMPs in respiratory mucosal fluid, providing protection against airway pathogen invasion and infection by inducing microbial aggregation and enhancing pathogen clearance. However, the relationship between PM_2.5 and these AMPs is unclear. To better understand the relationship between PM_2.5 and airway innate immune defenses, we review the respiratory antimicrobial activities of SAG and SPD, as well as the adverse effects of PM_2.5 on airway innate antimicrobial defense. We speculate there exists a dual effect between PM_2.5 and respiratory antimicrobial activity, which means that PM_2.5 suppresses respiratory antimicrobial activity through downregulating airway AMPs, while airway AMPs accelerate PM_2.5 clearance by inducing PM_2.5 microbial aggregation. We propose further research on the relationship between PM_2.5 and these AMPs.

The distribution variance of airborne microorganisms in urban and rural environments

Microorganisms are ubiquitous in the atmosphere, where they can disperse for a long distance. However, it remains poorly understood how these airborne microorganisms vary and which factors influence the microbial distribution in different anthropogenic activity regions. To explore the regional differences of bacteria and fungi in airborne particles, PM_2.5 and PM₁₀ samples were collected in the urban and rural areas of Hangzhou. The bacterial and fungal communities in the urban atmosphere was more similar to each other than those in the rural atmosphere. Analyses conducted by the concentration weighted trajectory model demonstrated that the local environment contributed more to the similarity of airborne bacteria and fungi compared with the atmospheric transport. The concentrations of local air pollutants (PM_2.5, PM₁₀, NO₂, SO₂ and CO) were positively correlated with the similarity of the bacterial and fungal communities. Additionally, the concentrations of these air pollutants in the urban site were about 1.5 times than those in the rural site. This implicated that anthropogenic activity, which is the essential cause of air pollutants, influenced the similarity of airborne bacteria and fungi in the urban area. This work ascertains the outdoor bacterial and fungal distribution in the urban and the rural atmosphere and provides a prospective model for studying the contributing factors of airborne bacteria and fungi.

Chemical and Biological Components of Urban Aerosols in Africa: Current Status and Knowledge Gaps

Aerosolized particulate matter (PM) is a complex mixture that has been recognized as the greatest cause of premature human mortality in low- and middle-income countries. Its toxicity arises largely from its chemical and biological components. These include polycyclic aromatic hydrocarbons (PAHs) and their nitro-derivatives (NPAHs) as well as microorganisms. In Africa, fossil fuel combustion and biomass burning in urban settings are the major sources of human exposure to PM, yet data on the role of aerosols in disease association in Africa remains scarce. This review is the first to examine studies conducted in Africa on both PAHs/NPAHs and airborne microorganisms associated with PM. These studies demonstrate that PM exposure in Africa exceeds World Health Organization (WHO) safety limits and carcinogenic PAHs/NPAHs and pathogenic microorganisms are the major components of PM aerosols. The health impacts of PAHs/NPAHs and airborne microbial loadings in PM are reviewed. This will be important for future epidemiological evaluations and may contribute to the development of effective management strategies to improve ambient air quality in the African continent.

Air pollution during the winter period and respiratory tract microbial imbalance in a healthy young population in Northeastern China

In order to investigate the relationship between air pollution and the respiratory tract microbiota, 114 healthy volunteers aged 18-21 years were selected during the winter heating period in Northeast China; 35 from a lightly polluted region (group A), 40 from a moderately polluted region (group B) and 39 from a heavily polluted region (group C). Microbial genome DNA was extracted from throat swab samples to study the oral flora composition of the volunteers by amplifying and sequencing the V3 regions of prokaryotic 16S rRNA. Lung function tests were also performed. The relative abundance of Bacteroidetes and Fusobacteria were significantly lower and Firmicutes Proteonacteria and Actinobacteria higher in participants from polluted regions. Within bacteria classes, Bacterioida abundance was lower and Clostridia abundance higher in polluted areas, which was also reflected in the order of abundance. In samples from region C, the abundance of Prevotellaceae, Veillonellaceae, Porphyromonadaceae, Fusobacteriaceae Paraprevollaceae and Flavobacteriaceae were lowest among the 3 regions studied, whereas the abundance of Lachnospiraceae and Ruminococcaceae were the highest. From group A to group C, the relative class abundances of Prevotella, Veillonella, Fusobacterium, Camphylobacter and Capnocytophaga Porphyromonas, Peptostreptococcus and Moraxella became lower in polluted areas. Pulmonary function correlated with air pollution and the oropharyngeal microbiota differed within regions of high, medium and low air pollution. Thus, during the winter heating period in Northeast China, the imbalance of the oropharyngeal microbiota might be caused by air pollution and is likely associated with impairment of lung function in young people.

Biological Composition of Respirable Particulate Matter in an Industrial Vicinity in South Africa

There is a growing concern that exposure to particulate matter of aerodynamic diameter of less than 2.5 µm (PM2.5) with biological composition (bioaerosols) may play a key role in the prevalence of adverse health outcomes in humans. This study determined the bacterial and fungal concentrations in PM2.5 and their inhalation health risks in an industrial vicinity in South Africa. Samples of PM2.5 collected on a 47-mm glass fiber filter during winter and summer months were analysed for bacterial and fungal content using standard methods. The health risks from inhalation of bioaerosols were done by estimating the age-specific dose rate. The concentration of bacteria (168⁻378 CFU/m³) was higher than fungi (58⁻155 CFU/m³). Bacterial and fungal concentrations in PM2.5 were lower in winter than in the summer season. Bacteria identified in summer were similar to those identified in winter: Staphylococcus sp., Bacillus sp., Micrococcus sp., Flavobacterium sp., Klebsiella sp. and Pseudomonas sp. Moreover, the fungal floras identified include Cladosporium spp., Aspergillus spp., Penicillium spp., Fusarium spp. and Alternaria spp. Children inhaled a higher dose of bacterial and fungal aerosols than adults. Bacteria and fungi are part of the bioaerosol components of PM2.5. Bioaerosol exposure may present additional health risks for children.

Jumping on the bed and associated increases of PM10, PM2.5, PM1, airborne endotoxin, bacteria, and fungi concentrations

Jumping on the bed is a favorite behavior of children; however, no study has investigated the increased air pollutants resulting from jumping on the bed. Therefore, we aimed to investigate the elevated concentrations of particulate matter (PM) and bioaerosols from jumping on the bed and making the bed. Simulation of jumping on the bed and making the bed was performed at sixty schoolchildren's houses in Taiwan. PM₁₀, PM_2.5, PM₁ (PM with aerodynamic diameter less than 10, 2.5, and 1 μm, respectively) and airborne bacteria, fungi and endotoxin concentrations were simultaneously measured over simulation and background periods. Our results show the increase of PM₁₀, PM_2.5, PM₁, airborne bacteria and fungi through the behavior of jumping on the bed (by 414 μg m-3, 353 μg m-3, 349 μg m-3, 6569 CFU m-3 and 978 CFU m-3, respectively). When making the bed, the PM₁₀, PM_2.5, PM₁, airborne bacteria and fungi also significantly increased by 4.69 μg m-3, 4.09 μg m-3, 4.15 μg m-3, 8569 CFU m-3, and 779 CFU m-3, respectively. Airborne endotoxin concentrations significantly increased by 21.76 EU m-3 following jumping on the bed and making the bed. Moreover, when jumping on the bed, higher PM_2.5 and PM₁ concentrations in houses with furry pets rather than no furry pets, and less airborne fungi in apartments than in townhouses were found. For making the bed, lower airborne fungi was found in houses using essential oils rather than no essential oils using. The airborne endotoxin concentrations were positively associated with furry pets and smokers in the homes and negatively correlated to the home with window opening with a statistical significance during the periods of jumping on the bed and making the bed. In conclusion, significant increases of PM and bioaerosols during jumping on the bed and making the bed may need to be concerned.

Study on the relationship between the concentration and type of fungal bio-aerosols at indoor and outdoor air in the Children's Medical Center, Tehran, Iran

Fungal bio-aerosols are of concern due to their adverse health effects, especially in indoor environments. The aim of this study was to evaluate the relationship between the concentration and type of fungal bio-aerosols in the indoor and outdoor of Children's Medical Center in Tehran, Iran. In the present descriptive-analytical study, the fungal bio-aerosols' concentrations in both indoor and outdoor of the hospital air were measured. The measurements were carried out by the Anderson method using a Quick Take 30 pump at 28.3 L min^-1 and 2.5 min sampling that was placed on a Sabouraud dextrose agar with chloramphenicol. The average concentrations of total fungal bio-aerosols in the hospital indoor and outdoor air were 40.48 and 119.6 CFU/m³, respectively. Onco-hematology and bone marrow transplantation wards were the most and least contaminated units, respectively (11.09 CFU/m³ vs 1.47 CFU/m³). The most common fungi isolated from the indoor environment were Penicillium spp. (45.86%) which was followed by Cladosporium spp. (31.92%), Aspergillus section Nigri (6.26%), sterilized mycelia (5.05%), and Aspergillus section Flavi (2.83%). Cladosporium spp. (61.10 CFU/m³) and Penicillium spp. (18.56 CFU/m³) had the highest mean concentrations in outdoor and indoor air, respectively. The indoor-to-outdoor ratio of fungal aerosols was < 1 at most sampling sites, indicating that the indoor fungal bio-aerosols may have originated from the outdoor environment.

Street Dust-Bound Polycyclic Aromatic Hydrocarbons in a Saudi Coastal City: Status, Profile, Sources, and Human Health Risk Assessment

Polycyclic aromatic hydrocarbons (PAHs) in street dust pose a serious problem threatening both the environment and human health. Street dust samples were collected from five different land use patterns (traffic areas TRA, urban area URA, residential areas REA, mixed residential commercial areas MCRA and suburban areas SUA) in Jeddah, a Saudi coastal city, and one in in Hada Al Sham, a rural area (RUA). This study aimed to investigate the status, profile, sources of PAHs and estimate their human health risk. The results revealed an average concentration of total PAHs of 3320 ng/g in street dust of Jeddah and 223 ng/g in RUA dust. PAHs with high molecular weight represented 83.38% of total PAHs in street dust of Jeddah, while the carcinogenic PAH compounds accounted 57.84%. The highest average concentration of total PAHs in street dust of Jeddah was found in TRA (4980 ng/g) and the lowest in REA (1660 ng/g). PAHs ratios indicated that the principal source of PAHs in street dust of Jeddah is pyrogenic, mainly traffic emission. Benzo(a)anthracene/chrysene (BaA/CHR) ratio suggests that PAHs in street dusts of Jeddah come mainly from emission of local sources, while PAHs in RUA might be transported from the surrounding urban areas. The estimated Incremental Lifetime Cancer Risk (ILCR) associated with exposure to PAHs in street dusts indicated that both dermal contact and ingestion pathways are major contributed to cancer risk for both children and adults. Based on BaPequivalence concentrations of total PAHs, ILCRIngestion, ILCRdermal and cancer risk values for children and adults exposed to PAHs in street dust of different areas in Jeddah were found between 10-6 and 10-4, indicating potential risk. The sequence of cancer risk was TRA > URA > MCRA > SUA > REA. Only exposure to BaP and DBA compounds had potential risk for both children and adults.

Effects of haze pollution on microbial community changes and correlation with chemical components in atmospheric particulate matter

In this study, particulate matter (PM) with aerodynamic diameters of ≤2.5 and ≤10 μm (PM_2.5 and PM₁₀, respectively), which was found at different concentrations in spring, was collected in Beijing. The chemical composition and bacterial community diversity of PM were determined, and the relationship between them was studied by 16S rRNA sequencing and mathematical statistics. Chemical composition analysis revealed greater relative percentages of total organic compounds (TOC) and secondary ions (NO₃^-, SO₄^2-, and NH₄⁺). The concentrations of Ca²⁺, Na⁺, Mg²⁺, K⁺ and SO₄^2- increased in high-concentration PM, which was associated with the contribution of soil, dust and soot. Microbiological analysis revealed 1191 operational taxonomic units. Microbial community structure was stable at the phylum level. The most abundant phyla were Proteobacteria, Actinobacteria, Firmicutes, Bacteroidetes and Cyanobacteria. Community clustering analysis at the genus level showed that the difference in bacterial community structure between different PM concentrations (clean air vs. smog) was greater than that between different particle sizes. The dominant genera varied in different concentrations of PM. An unclassified genus of Cyanobacteria and Comamonadaceae were most abundant in low- and high-concentration PM, respectively. The microbial community structure was dynamic at the genus level due to different environmental factors. The dominant bacteria in high-concentration PM were widely distributed in soils, indicating that the soil contributed more to the increase in the PM. The individual microbes that were detected did not increase significantly as the PM concentration increased. The bacterial community structure was strongly correlated with K⁺, Ca²⁺, Na⁺, Mg²⁺, SO₄^2- and TOC in high-concentration PM and had a good correlation with NO₃^-, Cl^-, NH₄⁺ and TIC in low-concentration PM. Soil and dust contributed to the increase in the concentration of the particles, and the relevant chemical components also produced differences in the bacterial community structure in different concentrations of PM.

Concentration and Community of Airborne Bacteria in Response to Cyclical Haze Events During the Fall and Midwinter in Beijing, China

Since 2013, severe haze events frequently have occurred in Beijing between October and March, which have created a significant public health threat. Although variations in the chemical composition of these haze events have been studied widely, information pertaining to airborne bacteria in such haze events remains limited. In this study, we characterized the concentration, community structure, and composition of the airborne bacteria in response to nine haze events that occurred between October 1, 2015, and January 5, 2016. We also analyzed the correlations of airborne bacteria (concentration, community structure, and composition) with pollution levels and meteorological factors. The results indicated that airborne bacterial concentration showed a positive cyclical correlation with the haze events, but the bacterial concentration plateaued at the yellow pollution level. In addition, we found particulate matter (PM₁₀) and relative humidity to be key factors that significantly affected the airborne bacterial concentration and community structure. Moreover, Halomonas and Shewanella were enriched on haze days for all nine of the haze events. Finally, the correlations between haze pollution and airborne bacteria in midwinter were weaker than those in fall and early winter, indicating an obvious staged distinction among the effects of haze on airborne bacteria. Our study illuminated the dynamic variation of bioaerosols corresponding to the cyclical haze events and revealed the interactions among air pollution, climate factors (mainly relative humidity), and airborne bacteria. These results imply that different strategies should be applied to deal with the potential threat of airborne bacteria during haze events in different seasons.

Structural Variation in the Bacterial Community Associated with Airborne Particulate Matter in Beijing, China, during Hazy and Nonhazy Days

The structural variation of the bacterial community associated with particulate matter (PM) was assessed in an urban area of Beijing during hazy and nonhazy days. Sampling for different PM fractions (PM_2.5 [<2.5 μm], PM₁₀ [<10 μm], and total suspended particulate) was conducted using three portable air samplers from September 2014 to February 2015. The airborne bacterial community in these samples was analyzed using the Illumina MiSeq platform with bacterium-specific primers targeting the 16S rRNA gene. A total of 1,707,072 reads belonging to 6,009 operational taxonomic units were observed. The airborne bacterial community composition was significantly affected by PM fractions (R = 0.157, P < 0.01). In addition, the relative abundances of several genera significantly differed between samples with various haze levels; for example, Methylobacillus, Tumebacillus, and Desulfurispora spp. increased in heavy-haze days. Canonical correspondence analysis and permutation tests showed that temperature, SO₂ concentration, relative humidity, PM₁₀ concentration, and CO concentration were significant factors that associated with airborne bacterial community composition. Only six genera increased across PM₁₀ samples (Dokdonella, Caenimonas, Geminicoccus, and Sphingopyxis) and PM_2.5 samples (Cellulomonas and Rhizobacter), while a large number of taxa significantly increased in total suspended particulate samples, such as Paracoccus, Kocuria, and Sphingomonas Network analysis indicated that Paracoccus, Rubellimicrobium, Kocuria, and Arthrobacter were the key genera in the airborne PM samples. Overall, the findings presented here suggest that diverse airborne bacterial communities are associated with PM and provide further understanding of bacterial community structure in the atmosphere during hazy and nonhazy days.IMPORTANCE The results presented here represent an analysis of the airborne bacterial community associated with particulate matter (PM) and advance our understanding of the structural variation of these communities. We observed a shift in bacterial community composition with PM fractions but no significant difference with haze levels. This may be because the bacterial differences are obscured by high bacterial diversity in the atmosphere. However, we also observed that a few genera (such as Methylobacillus, Tumebacillus, and Desulfurispora) increased significantly on heavy-haze days. In addition, Paracoccus, Rubellimicrobium, Kocuria, and Arthrobacter were the key genera in the airborne PM samples. Accurate and real-time techniques, such as metagenomics and metatranscriptomics, should be developed for a future survey of the relationship of airborne bacteria and haze.

A review on airborne microorganisms in particulate matters: Composition, characteristics and influence factors

Airborne microorganisms (AM), vital components of particulate matters (PM), are widespread in the atmosphere. Since some AM have pathogenicity, they can lead to a wide range of diseases in human and other organisms, meanwhile, some AM act as cloud condensation nuclei and ice nuclei which let them can affect the climate. The inherent characteristics of AM play critical roles in many aspects which, in turn, can decide microbial traits. The uncertain factors bring various influences on AM, which make it difficult to elaborate effect trends as whole. Because of the potential roles of AM in environment and potent effects of factors on AM, detailed knowledge of them is of primary significance. This review highlights the issues of composition and characteristics of AM with size-distribution, species diversity, variation and so on, and summarizes the main factors which affect airborne microbial features. This general information is a knowledge base for further thorough researches of AM and relevant aspects. Besides, current knowledge gaps and new perspectives are offered to roundly understand the impacts and application of AM in nature and human health.