Characteristics of ambient bioaerosols during haze episodes in China: A review

A super sandstorm altered the abundance and composition of airborne bacteria in Beijing

Sandstorm, which injects generous newly emerging microbes into the atmosphere covering cities, adversely affects the air quality in built environments. However, few studies have examined the change of airborne bacteria during severe sandstorm events. In this work, we analyzed the airborne bacteria during one of the strongest sandstorms in East Asia on March 15th, 2021, which affected large areas of China and Mongolia. The characteristics of the sandstorm were compared with those of the subsequent clean and haze days. The composition of the bacterial community of air samples was investigated using quantitative polymerase chain reaction (qPCR) and high-throughput sequencing technology. During the sandstorm, the particulate matter (PM) concentration and bacterial richness were extremely high (PM2.5: 207 µg/m3; PM10: 1630 µg/m3; 5700 amplicon sequence variants/m3). In addition, the sandstorm brought 10 pathogenic bacterial genera to the atmosphere, posing a grave hazard to human health. As the sandstorm subsided, small bioaerosols (0.65-1.1 µm) with a similar bacterial community remained suspended in the atmosphere, bringing possible long-lasting health risks.

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.

Characteristics of bioaerosol emissions from a municipal wastewater treatment plant: Health risk assessment and microbial composition

Bioaerosols released from municipal wastewater treatment plants (MWWTPs) contain pathogenic microorganisms, if dispersed into the atmosphere, which pose potential health risks to humans. In this study, the concentrations and size distribution of bioaerosol, factors on the bioaerosol emission, exposure risk, and microbial composition in different treatment units of a MWWTP were investigated. The results showed that bioaerosol was released to different degrees in each treatment unit, with the concentrations of bioaerosol varied widely, ranging from 978 to 3710 CFU/m3. FG and PST were primary bioaerosol emission sources in MWWTP. COD concentration, wind speed (WS) and relative humidity (RH) significantly influenced bioaerosol concentrations. The proportion of inhalable particles (< 4.7 μm) ranged from 51.35 % to 83.33 %, and bioaerosol emitted from WWTP caused a non-carcinogenic risk to children by the exposure risk assessment (HI > 1), which need to be paid more attention. Bacterial, fungal and actinomycete aerosols were detected in each treatment unit of MWWTP. Among these bioaerosols, bacterial aerosol was dominant. Importantly, several pathogenic bacteria including Sphingobium, Brevundimonas, Romboutsia, Arcobacter, Acinetobacter, and Mycobacterium were identified within the airborne bacteria population, most of which originated from wastewater or sludge, particularly in the ambient air of AeT. Pathogenic bacteria from MWWTP should be studied further to determine their long-term behavior and possible health risks.

The abundance and pathogenicity of microbes in automobile air conditioning filters across the typical cities of China and Europe

Bioaerosols are widely distributed in urban air and can be transmitted across the atmosphere, biosphere, and anthroposphere, resulting in infectious diseases. Automobile air conditioning (AAC) filters can trap airborne microbes. In this study, AAC filters were used to investigate the abundance and pathogenicity of airborne microorganisms in typical Chinese and European cities. Culturable bacteria and fungi concentrations were determined using microbial culturing. High-throughput sequencing was employed to analyze microbial community structures. The levels of culturable bioaerosols in Chinese and European cities exhibited disparities (Analysis of Variance, P < 0.01). The most dominant pathogenic bacteria and fungi were similar in Chinese (Mycobacterium: 18.2-18.9 %; Cladosporium: 23.0-30.2 %) and European cities (Mycobacterium: 15.4-37.7 %; Cladosporium: 18.1-29.3 %). Bartonella, Bordetella, Alternaria, and Aspergillus were also widely identified. BugBase analysis showed that microbiomes in China exhibited higher abundances of mobile genetic elements (MGEs) and biofilm formation capacity than those in Europe, indicating higher health risks. Through co-occurrence network analysis, heavy metals such as zinc were found to correlate with microorganism abundance; most bacteria were inversely associated, while fungi exhibited greater tolerance, indicating that heavy metals affect the growth and reproduction of bioaerosol microorganisms. This study elucidates the influence of social and environmental factors on shaping microbial community structures, offering practical insights for preventing and controlling regional bioaerosol pollution.

Characteristics and health impacts of bioaerosols in animal barns: A comprehensive study

Bioaerosols produced during animal production have potential adverse effects on the health of workers and animals. Our objective was to investigate characteristics, antibiotic-resistance genes (ARGs), and health risks of bioaerosols in various animal barns. Poultry and swine barns had high concentrations of airborne bacteria (11156 and 10917 CFU/m3, respectively). Acinetobacter, Clostridium sensu stricto, Corynebacterium, Pseudomonas, Psychrobacter, Streptococcus, and Staphylococcus were dominant pathogenic bacteria in animal barns, with Firmicutes being the most abundant bacterial phylum. Based on linear discriminant analysis effect size (LEfSe), there were more discriminative biomarkers in cattle barns than in poultry or swine barns, although the latter had the highest abundance of bacterial pathogens and high abundances of ARGs (including tetM, tetO, tetQ, tetW sul1, sul2, ermA, ermB) and intI1). Based on network analyses, there were higher co-occurrence patterns between bacteria and ARGs in bioaerosol from swine barns. Furthermore, in these barns, relative abundance of bacteria in bioaerosol samples was greatly affected by environmental factors, mainly temperature, relative humidity, and concentrations of CO2, NH3, and PM2.5. This study provided novel data regarding airborne bio-contaminants in animal enclosures and an impetus to improve management to reduce potential health impacts on humans and animals.

Impact of climate zones and seasons on indoor airborne microbial communities: Insights from a comprehensive analysis

Bacteria and fungi are ubiquitous throughout built environments and are suspended in the air, potentially affecting human health. However, the impacts of climate zones on the diversity, structure, and stochastic assembly of indoor airborne microbes remain unknown. This study comprehensively analyzed indoor airborne microbes across five climate zones in China during the summer and winter using high-throughput sequencing. The diversity and structure of indoor airborne communities vary across climatic zones. A random forest model was used to identify biomarkers in different climate zones. The results showed no relationship between the biomarkers and their rankings in mean relative abundance. The Sloan neutral model fitting results indicated that the impact of climate zones on the stochastic process in the assembly of indoor airborne microbes was considerably more important than that of seasons. Additionally, the influence of seasons on the diversity, structure, and stochastic assembly process of indoor airborne microbes differed among different climate zones. The diversity, structure, and stochastic assembly processes of bacteria present distinctive outcomes in climate zones and seasons compared with those of fungi. Overall, these findings indicate that customized strategies are necessary to manage indoor airborne microbial communities in each climate zone, season, and for specific microbial species.

Bioaerosols in the coastal region of Qingdao: Community diversity, impact factors and synergistic effect

Atmospheric bioaerosols are influenced by multiple factors, including physical, chemical, and biotic interactions, and pose a significant threat to the public health and the environment. The nonnegligible truth however is that the primary driver of the changes in bioaerosol community diversity remains unknown. In this study, putative biological association (PBA) was obtained by constructing an ecological network. The relationship between meteorological conditions, atmospheric pollutants, water-soluble inorganic ions, PBA and bioaerosol community diversity was analyzed using random forest regression (RFR)-An ensemble learning algorithm based on a decision tree that performs regression tasks by constructing multiple decision trees and integrating the predicted results, and the contribution of different rich species to PBA was predicted. The species richness, evenness and diversity varied significantly in different seasons, with the highest in summer, followed by autumn and spring, and was lowest in winter. The RFR suggested that the explanation rate of alpha diversity increased significantly from 73.74 % to 85.21 % after accounting for the response of the PBA to diversity. The PBA, temperature, air pollution, and marine source air masses were the most crucial factors driving community diversity. PBA, particularly putative positive association (PPA), had the highest significance in diversity. We found that under changing external conditions, abundant taxa tend to cooperate to resist external pressure, thereby promoting PPA. In contrast, rare taxa were more responsive to the putative negative association because of their sensitivity to environmental changes. The results of this research provided scientific advance in the understanding of the dynamic and temporal changes in bioaerosols, as well as support for the prevention and control of microbial contamination of the atmosphere.

Efficacy of treating bacterial bioaerosols with weakly acidic hypochlorous water: A simulation chamber study

The COVID-19 pandemic highlighted the dangers of airborne transmission and the risks of pathogen-containing small airborne droplet inhalation as an infection route. As a pathogen control, Weakly Acidic Hypochlorous Water (WAHW) is used for surface disinfection. However, there are limited assessments of air disinfection by WAHW against airborne pathogens like bioaerosols. This was an empirical study evaluating the disinfection efficacy of WAHW in an atmospheric simulation chamber system against four selected model bacteria. The strains tested included Staphylococcus aureus (SA), Escherichia coli (EC), Pseudomonas aeruginosa (PA), and Pseudomonas aeruginosa (PAO1). Each bacterial solution was nebulized into the chamber system as the initial step, and bioaerosol was collected into the liquid medium by a bio-sampler for colony forming units (CFU) determination. Secondly, the nebulized bacterial bioaerosol was exposed to nebulized double distilled water (DDW) as the control and nebulized 150 ppm of WAHW as the experimental groups. After the 3 and 30-min reaction periods, the aerosol mixture inside the chamber was sampled in liquid media and then cultured on agar plates with different dilution factors to determine the CFU. Survival rates were calculated by a pre-exposed CFU value as a reference point. The use of WAHW decreased bacterial survival rates to 1.65-30.15% compared to the DDW control. PAO1 showed the highest survival rates and stability at 3 min was higher than 30 min in all experiments. Statistical analysis indicated that bacteria survival rates were significantly reduced compared to the controls. This work verifies the bactericidal effects against Gram-positive/negative bioaerosols of WAHW treatment. As WAHW contains chlorine in the acid solution, residual chlorine air concentration is a concern and the disinfection effect at different concentrations also requires investigation. Future studies should identify optimal times to minimize the treated time range and require measurements in a real environment.

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.

Aeromicrobiology: A global review of the cycling and relationships of bioaerosols with the atmosphere

Airborne microorganisms and biological matter (bioaerosols) play a key role in global biogeochemical cycling, human and crop health trends, and climate patterns. Their presence in the atmosphere is controlled by three main stages: emission, transport, and deposition. Aerial survival rates of bioaerosols are increased through adaptations such as ultra-violet radiation and desiccation resistance or association with particulate matter. Current research into modern concerns such as climate change, global gene transfer, and pathogenicity often neglects to consider atmospheric involvement. This comprehensive review outlines the transpiring of bioaerosols across taxa in the atmosphere, with significant focus on their interactions with environmental elements including abiotic factors (e.g., atmospheric composition, water cycle, and pollution) and events (e.g., dust storms, hurricanes, and wildfires). The aim of this review is to increase understanding and shed light on needed research regarding the interplay between global atmospheric phenomena and the aeromicrobiome. The abundantly documented bacteria and fungi are discussed in context of their cycling and human health impacts. Gaps in knowledge regarding airborne viral community, the challenges and importance of studying their composition, concentrations and survival in the air are addressed, along with understudied plant pathogenic oomycetes, and archaea cycling. Key methodologies in sampling, collection, and processing are described to provide an up-to-date picture of ameliorations in the field. We propose optimization to microbiological methods, commonly used in soil and water analysis, that adjust them to the context of aerobiology, along with other directions towards novel and necessary advancements. This review offers new perspectives into aeromicrobiology and calls for advancements in global-scale bioremediation, insights into ecology, climate change impacts, and pathogenicity transmittance.

Characterization of bacterial species and antibiotic resistance observed in Seoul, South Korea's popular Gangnam-gu area

Public transportation facilities, especially road crossings, which raise the pathogenic potential of urban environments, are the most conducive places for the transfer of germs between people and the environment. It is necessary to study the variety of the microbiome and describe its unique characteristics to comprehend these relationships. In this investigation, we used 16 S rRNA gene sample sequencing to examine the biological constituents and inhalable, thoracic, and alveolar particles in aerosol samples collected from busy areas in the Gangnam-gu district of the Seoul metropolitan area using a mobile vehicle. We also conducted a comparison analysis of these findings with the previously published data and tested for antibiotic resistance to determine the distribution of bacteria related to the human microbiome and the environment. Actinobacteria, Cyanobacteria, Bacteriodetes, Proteobacteria, and Firmicutes were the top five phyla in the bacterial 16 S rRNA libraries, accounting for >90 % of all readings across all examined locations. The most prevalent classes among the 12 found bacterial classes were Bacilli (45.812 %), Gammaproteobacteria (25.238 %), Tissierellia (13.078 %), Clostridia (5.697 %), and Alphaproteobacteria (5.142 %). The data acquired offer useful information on the variety of bacterial communities and their resistance to antibiotic drugs on the streets of Gangnam-gu, one of the most significant social centers in the Seoul metropolitan area. This work emphasizes the relevance of biological particles and particulate matter in the air, and it suggests more research is needed to perform biological characterization of the ambient particulate matter.

East Asian monsoon manipulates the richness and taxonomic composition of airborne bacteria over China coastal area

Airborne bacteria may have significant impacts on aerosol properties, public health and ecosystem depending on their taxonomic composition and transport. This study investigated the seasonal and spatial variations of bacterial composition and richness over the east coast of China and the roles of East Asian monsoon played through synchronous sampling and 16S rRNA sequencing analysis of airborne bacteria at Huaniao island of the East China Sea (ECS) and the urban and rural sites of Shanghai. Airborne bacteria showed higher richness over the land sites than Huaniao island with the highest values found in the urban and rural springs associated with the growing plants. For the island, the maximal richness occurred in winter as the result of prevailing terrestrial winds controlled by East Asian winter monsoon. Proteobacteria, Actinobacteria and Cyanobacteria were found to be top three phyla, together accounting for 75 % of total airborne bacteria. Radiation-resistant Deinococcus, Methylobacterium belonging to Rhizobiales (related to vegetation) and Mastigocladopsis_PCC_10914 originating from marine ecosystem were indicator genera for urban, rural and island sites, respectively. The Bray-Curits dissimilarity of taxonomic composition between the island and two land sites was the lowest in winter with the representative genera over island also typically from the soil. Our results reveal that seasonal change of monsoon wind directions evidently affects the richness and taxonomic composition of airborne bacteria in China coastal area. Particularly, prevailing terrestrial winds lead to the dominance of land-derived bacteria over the coastal ECS which may have a potential impact on marine ecosystem.

The characteristics of nano-micron calcite particles/common bacteria complex and its interfacial interaction

Based on the composite pollution of atmospheric microbial aerosol, this paper selects the calcite/bacteria complex as the research object which was prepared by calcite particles and two common strains of bacteria (Escherichia coli, Staphylococcus aureus) in the solution system. The morphology, particle size, surface potential, and surface groups of the complex were explored by modern analysis and testing methods, with an emphasis on the interfacial interaction between calcite and bacteria. The SEM, TEM, and CLSM results showed that the morphology of the complex could be divided into three types: bacteria adhering to the surface or edge of micro-CaCO3, bacteria aggregating with nano-CaCO3, and single nano-CaCO3 wrapping bacteria. The complex's particle size was about 2.07 ~ 192.4 times larger than the original mineral particles, and the nano-CaCO3/bacteria complex's particle size variation was caused by the fact that nano-CaCO3 has agglomeration in solution. The surface potential of the micro-CaCO3/bacteria complex (isoelectric point pH = 3.0) lies between micro-CaCO3 and bacteria, while the surface potential of the nano-CaCO3/bacteria complex (isoelectric point pH = 2.0) approaches the nano-CaCO3. The complex's surface groups were based primarily on the infrared characteristics of calcite particles, accompanied by the infrared characteristics of bacteria, displaying the interfacial interaction from the protein, polysaccharides, and phosphodiester groups of bacteria. The interfacial action of the micro-CaCO3/bacteria complex is mainly driven by electrostatic attraction and hydrogen bonding force, while the nano-CaCO3/bacteria complex is guided by surface complexation and hydrogen bonding force. The increase in the β-fold/α-helix ratio of the calcite/S. aureus complex indicated that the secondary structure of bacterial surface proteins was more stable and the hydrogen bond effect was strong than the calcite/E. coli complex. The findings are expected to provide basic data for the mechanism research of atmospheric composite particles closer to the real environment.

Comparison of airborne bacteria and fungi in different built environments in selected cities in five climate zones of China

Bioaerosols in different built environments and climate zones have unique effects on occupant health, which demands comparisons of their characteristics to make targeted control measures. This study investigated bioaerosol distribution in five different climate zones across China with four building types (n = 686 rooms). The results showed significant disparities in bioaerosol concentrations among various buildings and climate zones. The bacterial concentrations in residences (536 ± 647 CFU/m³) were significantly higher than in schools, offices, and hospitals owing to different built environments and human activities. The highest mean value of fungal concentration was found in schools (826 ± 955 CFU/m³) due to their greater landscaping area. The bacterial concentrations in the cold zone (307 ± 506 CFU/m³) and the hot summer and cold winter zone (214 ± 180 CFU/m³) were significantly lower than in the other three climate zones. The fungal concentrations in the severe cold zone (709 ± 900 CFU/m³) and the hot summer and warm winter zone (1094 ± 832 CFU/m³) were significantly higher than in the other three climate zones; the lower the indoor temperature (T) and the higher the air exchange rate, the lower the indoor airborne bacterial concentration; the lower the relative humidity (RH), the lower the indoor airborne fungi. In addition, a higher air exchange rate could also reduce the effect of occupant density on indoor bacterial concentration. The results of this study provide valuable data on bioaerosol profiles in various built environments and climate zones and highlight the significance of T, RH, and air exchange rate on indoor bioaerosol concentrations.

Bioaerosols in an industrial park and the adjacent houses: Dispersal between indoor/outdoor, the impact of air purifier, and health risk reduction

Inhaling airborne pathogens may cause severe epidemics showing huge threats to indoor dwellings residents. The ventilation, environmental parameters, and human activities would affect the abundance and pathogenicity of bioaerosols in indoor. However, people know little about the indoor airborne microbes especially pathogens near the industrial park polluted with organics and heavy metals. Herein, the indoor bioaerosols' community composition, source and influencing factors near an electronic waste (e-waste) industrial park were investigated. Results showed that the average bioaerosol level in the morning was lower than evening. Bioaerosol concentration and activity in indoor (1936 CFU/m³ and 7.62 × 10⁵ ng/m³ sodium fluorescein in average) were lower than the industrial park (4043 CFU/m³ and 7.77 × 10⁵ ng/m³ sodium fluorescein), and higher microbial viability may be caused by other pollutants generated during e-waste dismantling process. Fluorescent biological aerosol particles occupied 17.6%-23.7% of total particles, indicating that most particles were non-biological. Bacterial communities were richer and more diverse than fungi. Furthermore, Bacillus and Cladosporium were the dominant indoor pathogens, and pathogenic fungi were more influenced by environmental factors than bacteria. SourceTracker analysis indicates that outdoor was the main source of indoor bioaerosols. The hazard quotient (<1) of airborne microbes through inhalation was negligible, but long-term exposure to pathogens could be harmful. Air purifiers could effectively remove the airborne fungi and spheroid bacteria than cylindrical bacteria, but open doors and windows would reduce the purification efficiency. This study is great important for risk assessments and control of indoor bioaerosols near industrial park.

Understanding the influence of the bioaerosol source on the distribution of airborne bacteria in hospital indoor air

The composition and concentration of airborne microorganisms in hospital indoor air has been reported to contain airborne bacteria and fungi concentrations ranged 10¹-10³ CFU/m³ in inpatients facilities which mostly exceed recommendations from the World Health Organization (WHO). In this work, a deeper knowledge of the performance of airborne microorganisms would allow improving the designs of the air-conditioning installations to restrict hospital-acquired infections (HAIs). A solution containing Escherichia coli (E. coli) as a model of airborne bacteria was nebulized using the Collison nebulizer to simulate bioaerosols in various hospital areas such as patients' rooms or bathrooms. Results showed that the bioaerosol source had a significant influence on the airborne bacteria concentrations since 4.00 10², 6.84 10³ and 1.39 10⁴ CFU mL^-1 were monitored during the aerosolization for 10 min of urine, saliva and urban wastewater, respectively. These results may be explained considering the quite narrow distribution profile of drop sizes around 1.10-1.29 μm obtained for urban wastewater, with much vaster distribution profiles during the aerosolization of urine or saliva. The airborne bacteria concentration may increase up to 10⁷ CFU mL^-1 for longer sampling times and higher aerosolization pressures, causing several cell damages. The cell membrane damage index (I_D) can vary from 0 to 1, depending on the genomic DNA releases from bacteria. In fact, the I_D of E. coli was more than two times higher (0.33 vs. 0.72) when increasing the pressure of air flow was applied from 1 to 2 bar. Finally, the ventilation air flow also affected the distribution of bioaerosols due to its direct relationship with the relative humidity of indoor air. Specifically, the airborne bacteria concentration diminished almost below 3-logs by applying more than 10 L min^-1 during the aerosolization of urine due to their inactivation by an increase in their osmotic pressure.

Characterization of airborne bacteria and fungi at a land-sea transition site in Southern China

Airborne microbe can have impact on regional to global climate as ice nuclei and cloud condensation nuclei. In coastal region, microbial aerosols are simultaneously contributed by terrestrial and marine sources under the influence of land-sea air exchange. We present a study on the characteristics of airborne bacteria and fungi, including their concentrations and communities, at a land-sea transition site in Southern China from December 2019 to December 2020. Seasonal variations of microbial communities were observed with evident profiles in summer, especially for fungal aerosols. The significant enhancement of Basidiomycota abundance in summer was contributed by local biogenic release under the influence of meteorological factors. Terrestrial sources are suggested as the dominant contributors to both bacterial and fungal aerosols rather than marine sources during the whole year period. Source-tracking analysis identified that marine contributions to airborne bacteria and fungi were 3.1-14.2 % and 4-24 %, respectively. It suggests that airborne fungi should be more suitable for long-range transport than airborne bacteria. This study improves the understanding of the conversional contribution of marine and terrestrial sources to airborne microbes in coastal region and the influencing environmental factors under land-sea exchange.

Long-range transport of airborne bacteria over East Asia: Asian dust events carry potentially nontuberculous Mycobacterium populations

The nontuberculous mycobacterial pulmonary disease (NTM-PD) caused by Mycobacterium species has increased in prevalence all over the world. The distributions of NTM-PD are possibly determined by the westerly wind traveling at high altitudes over East Asia. However, the long-range transport of Mycobacterium species has not been demonstrated by analyzing the bacterial communities in aerosols such as desert mineral particles and anthropogenic pollutants transported by the westerly wind. Here, airborne bacterial compositions were investigated including Mycobacterium species in high-elevation aerosols, which were captured in the snow cover at 2,450 m altitude on Mt. Tateyama. This was further compared to the ground-level or high-altitude aerosols collected at six sampling sites distributed from Asian-dust source region (Tsogt-Ovoo) to downwind areas in East Asia (Asian continental cities; Erenhot, Beijing, Yongin, Japanese cities; Yonago, Suzu, Noto Peninsula). The cell concentrations and taxonomic diversities of airborne bacteria decreased from the Asian continent to the Japan area. Terrestrial bacterial populations belonging to Firmicutes and Actinobacteria showed higher relative abundance at high-elevation and Japanese cities. Additionally, Mycobacterium species captured in the snow cover on Mt. Tateyama increased in relative abundance in correspondence to the increase of black carbon concentrations. The relative abundance of Mycobacterium sequences was higher in the aerosol samples of Asian continental cities and Japanese cities than in the desert area. Presumably, anthropogenic pollution over East Asia carries potential Mycobacterium species, which induce NTM-PD, thereby impacting upon the public health.

Influence of meteorological parameters and oxidizing capacity on characteristics of airborne particulate amines in an urban area of the Pearl River Delta, China

Nine amine species in atmospheric particles during haze and low-pollution days with low and high relative humidity (RH) were analyzed in urban Guangzhou, China. The mean concentrations of total measured amines (Ʃamines) in fine particles were 208 ± 127, 63.7 ± 21.3, and 120 ± 20.1 ng m^-3 during haze, low pollution-low RH (LP-LRH), and low pollution-high RH (LP-HRH) episodes, respectively. The dominant amine species were methylamine (MA), dimethylamine (DMA), diethylamine (DEA) and dibutylamine (DBA), which in total accounted for 82-91% of the Ʃamines during different pollution episodes. The contributions of Ʃamines-C to water-soluble organic carbon (WSOC) and Ʃamines-N to water-soluble organic nitrogen (WSON) were 1.52% and 2.49% during haze, 1.24% and 1.96% during LP-LRH, and 2.00 and 2.98% during LP-HRH days, respectively. The mass proportion of Ʃamines in fine particles was higher during LP-HRH periods (0.19%) than during haze and LP-LRH periods (0.16%). The mass proportion of DBA in Ʃamines increased from 7% during haze and LP-LRH episodes to 25% during LP-HRH episodes. Compared with other amines, DBA showed a stronger linear relationship with RH (r = 0.867, p < 0.01), which demonstrates its high sensitivity to high RH conditions. Meteorological parameters (including RH, the mixed layer depth, wind speed and temperature), the oxidizing capacity (ozone concentration), and gaseous pollutants (NO_x and SO₂) correlated with amines under different pollution conditions. Under high RH, acid-base reactions were the dominant pathway for the gas-to-particle distribution of amines in urban areas, while direct dissolution dominated in the background site. To our knowledge, this study is the first attempt to conduct in situ measurements of particulate amines during different pollution conditions in China, and further research is needed to in-depth understanding of the influence of amines on haze formation.

Advances in particulate matter filtration: Materials, performance, and application

Air-borne pollutants in particulate matter (PM) form, produced either physically during industrial processes or certain biological routes, have posed a great threat to human health. Particularly during the current COVID-19 pandemic, effective filtration of the virus is an urgent matter worldwide. In this review, we first introduce some fundamentals about PM, including its source and classification, filtration mechanisms, and evaluation parameters. Advanced filtration materials and their functions are then summarized, among which polymers and MOFs are discussed in detail together with their antibacterial performance. The discussion on the application is divided into end-of-pipe treatment and source control. Finally, we conclude this review with our prospective view on future research in this area.

Seasonal and vegetational variations of culturable bacteria concentrations in air from urban forest parks: a case study in Hunan, China

It is important to investigate the airborne bacterial air quality in urban forest parks as tree bacteriostasis practices are being increasingly advocated as measures to improve the air quality and public health in urban green spaces around the world. The aim of the study was to quantitatively investigate airborne culturable bacteria (ACB) concentration levels based on field measurements in every season in five selected forest communities and the uncovered space in an urban forest park, as well as the effects of several factors on the culturability of airborne bacteria. Results suggested that the airborne bacterial levels of all the forest communities reached the clean air quality standard with regard to the airborne bacteria content, with the highest concentration of ACB showing in the uncovered space (1658 ± 1298 CFU/m³) and the lowest showing in the mixed community (907 ± 567 CFU/m³). The temporal distribution analysis showed that the airborne bacteria were mostly concentrated in summer, as well as in the morning and afternoon. The bacteriostatic rates of the mixed community were significantly different with seasonal variation (p < 0.05). Spearman's correlations revealed that the concentration of ACB was significantly positively correlated with the season, wind speed (WS), temperature (T), ultraviolet light (UV), negative air ion (NAI), and total suspended particles (TSP) (p<0.05) but significantly negatively correlated with the forest community type (p < 0.05). Overall, the selection of tree species plays a key role in shaping the forest structure and improving air quality, and the urban forest highlights key priorities for future efforts toward a cleaner, healthier, and more diverse regional forest environment.

Seasonal and short-term variations of bacteria and pathogenic bacteria on road deposited sediments

The bacteria (including pathogenic bacteria) attached to road deposited sediments (RDS) may interrelate with the microbe in the atmosphere, soil and water through resuspension and wash-off, and is of great significance to human and ecological health. However, the characteristics of bacterial communities with different time scale on RDS were unknown to dates. Climate change prolonged the dry days between rain events in many areas, making the varied trend of bacterial communities might be more significant in short term. This study revealed the characteristics of bacterial communities on RDS in urban and suburban areas through seasonal and daily scale. The correlations between other factors (land use, particle size, and chemical components) and the bacterial communities were also analyzed. It was found that the season showed a higher association with the bacterial community diversity than land use and particle size in urban areas. The bacterial community diversity increased substantially throughout the short-term study period (41 days) and the variation of dominant bacteria could be fitted by quadratic function in suburbs. In addition, urbanization notably increased the bacterial community diversity, while the potential pathogenic bacteria were more abundant in the suburban areas, coarse RDS (>75 μm), and in spring. The chemical components on RDS showed special correlations with the relative abundance of dominant bacteria. The research findings would fill the knowledge gap on RDS bacterial communities and be helpful for the future research on the assembly process of bacterial communities.

Evolution of PM2.5 bacterial community structure in Beijing's suburban atmosphere

Biosafety has become one of the greatest challenges facing humanity. Outbreaks of infectious diseases caused by bacteria and viruses have had a huge impact on public health. In addition, non-severe polluted air quality has gradually become the norm; however, literature on the impacts of bioaerosols under long-term exposure to low concentrations of PM_2.5 in China is limited. This study analyzed the evolution of the PM_2.5 bacterial community in the Huairou district of Beijing under different pollution conditions. We used high-throughput sequencing to seasonally analyze samples over a year (from July 2018 to May 2019) and winter samples from different years (2015, 2016, 2018, and 2019). The results showed that the bacterial diversity and community composition of PM_2.5 were significantly different in different seasons, whereas under different pollution levels, there were no significant differences. During the observation period, the number of bacterial species decreased with the increase in pollution; however, a high proportion of bacteria can exist as core species under different pollution levels for a long time. Furthermore, bacteria can be relatively stable in the local environment during the same season but in different years. Although the relative abundances of different bacteria change differently with the variation in pollution level, there is no statistical difference. Importantly, there was a higher abundance of opportunistic pathogenic bacteria when the air quality index was 0-100 in winter. This study comprehensively revealed the characteristics of the evolution of bacterial communities under different pollution levels and in different years and emphasized the health effects of non-pollution air quality. This study can provide a theoretical basis for establishing a sound environmental microbial monitoring and defense system.

High time-resolved characterization of airborne microbial community during a typical haze pollution process

Variations of bioaerosol characteristics during the process of haze pollution have rarely been explored. In this study, high time-resolved variations of the community structures of bacteria, fungi, and ammonia-oxidizing microorganisms (AOMs) were assessed during a typical haze pollution process. The impacts of meteorological factors, water-soluble inorganic ions (WSII), and organic dicarboxylic acids (DCA) on the airborne microbial community were systematically evaluated. The results showed that the bacterial community varied greatly during the formation stages of haze pollution, and tended to stabilize with the further development of haze pollution. Nevertheless, variations of the fungal community lasted throughout the whole haze pollution process. Furthermore, Nitrososphaera absolutely dominated the ammonia-oxidizing archaea (AOA) and declined as PM_2.5 burst. Network analysis identified relatively weak interactions and co-occurrence patterns between dominant fungal genera. Importantly, dust source ions and PM_2.5 acidity exerted the most significant impacts on bacterial and fungal communities. These results identify the high time-resolved variations of airborne microbial communities during the formation and development of haze pollution process, and provide valuable data to better understand the interaction between bioaerosols and haze pollution.

Seasonal Variation Characteristics of Bacteria and Fungi in PM2.5 in Typical Basin Cities of Xi’an and Linfen, China

Microorganisms existing in airborne fine particulate matter (PM2.5) have key implications in biogeochemical cycling and human health. In this study, PM2.5 samples, collected in the typical basin cities of Xi’an and Linfen, China, were analyzed through high-throughput sequencing to understand microbial seasonal variation characteristics and ecological functions. For bacteria, the highest richness and diversity were identified in autumn. The bacterial phyla were dominated by Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes. Metabolism was the most abundant pathway, with the highest relative abundance found in autumn. Pathogenic bacteria (Pseudomonas, Acinetobacter, Serratia, and Delftia) were positively correlated with most disease-related pathways. Besides, C cycling dominated in spring and summer, while N cycling dominated in autumn and winter. The relative abundance of S cycling was highest during winter in Linfen. For fungi, the highest richness was found in summer. Basidiomycota and Ascomycota mainly constituted the fungal phyla. Moreover, temperature (T) and sulfur dioxide (SO2) in Xi’an, and T, SO2, and nitrogen dioxide (NO2) in Linfen were the key factors affecting microbial community structures, which were associated with different pollution characteristics in Xi’an and Linfen. Overall, these results provide an important reference for the research into airborne microbial seasonal variations, along with their ecological functions and health impacts.

An updated systematic review on the association between atmospheric particulate matter pollution and prevalence of SARS-CoV-2

On December 31, 2019, the novel human coronavirus (COVID-19) was emerged in Wuhan city, China, which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). There is a much controversial debate about the major pathways of transmission of the virus including airborne route. The present work is a systematic literature review (SR) aimed to assess the association of air pollution especially particulate matter pollution in the transmission and acceleration of the spread of SARS-CoV-2. The systematic literature search was performed to identify the available studies published through October 31, 2020 concerning the transmission of the disease and particulate matter air pollution in four international electronic databases. From the results of the included studies, there are suggestions that atmospheric particulate matter pollution plays a role in the SARS-CoV-2 spread, but the literature has not confirmed that it enhances the transmission although some studies have proposed that atmospheric particulate matter can operate as a virus carrier, promoting its spread. Therefore, although PM concentration alone cannot be effective in spreading the COVID-19 disease, other meteorological and environmental parameters including size of particles in ambient air, weather conditions, wind speed, relative humidity (RH) and temperature are involved. Therefore, it is necessary to consider all influencing parameters to prevent the spreading of COVID-19 disease. More studies are required to strengthen the scientific evidence and support more definitive conclusions.

Vertical variations in the concentration and community structure of airborne microbes in PM2.5

With the recent rapid development of urbanization, severe air pollution events frequently occur in China. Subsequently, variations of bioaerosols during air pollution events have attracted increasing attention in recent years. However, most published studies on bioaerosols mainly focus on the characteristics of airborne bacteria and fungi at a certain height near the ground surface. The vertical variations in microbial aerosols at different heights are not well understood. In this study, PM_2.5 samples at three heights (1.5 m, 100 m and 229.5 m) were collected from September 2019 to January 2020 in Xi'an, China. The samples were then analyzed by a fluorescence staining and high-throughput sequencing to explore the vertical variations in the concentration and community structure of the airborne bacteria. The results show that the microbial concentration in PM_2.5 decreased with increasing height on polluted days, while there was no significant difference at different heights on non-polluted days (p > 0.05). The bacterial community structures were similar at different heights on polluted days; however, on non-polluted days, the bacterial community structure at 229.5 m was significantly different from that at the other heights. Importantly, meteorological factors had more significant effects on the bacterial community at 229.5 m than at 1.5 m and 100 m. The present results can improve the understanding of vertical distribution of bioaerosols and their diffusion process.

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.

Abundance and composition of airborne archaea during springtime mixed dust and haze periods in Beijing, China

Archaea have an important role in the elemental biogeochemical cycle and human health. However, characteristics of airborne archaea affected by anthropogenic and natural processes are unclear. In this study, we investigated the abundance, structures, influencing factors and assembly processes of the archaeal communities in the air samples collected from Beijing in springtime using quantitative polymerase chain reaction (qPCR), high-throughput sequencing technology and statistical analysis. The concentrations of airborne archaea ranged from 10¹ to 10³ copies m^-3 (455 ± 211 copies m^-3), accounting for 0.67% of the total prokaryote (sum of archaea and bacteria). An increase in airborne archaea was seen when the air quality shifted from clean to slightly polluted conditions. Sandstorm dust imported a large number of archaea to the local atmosphere. Euryarchaeota, Thaumarchaeota and Crenarchaeota were the dominant phyla, revealing the primary role of soil in releasing archaea to the ambient environment. Dispersal-related neutral processes play an important role in shaping the structure of airborne archaeal assembly. Of all phyla, methanogenic Euryarchaeota were most abundant in the air parcels come from the south of Beijing. Air masses from the west of Beijing, which brought sandstorm to Beijing, carried large amounts of ammonia oxidizing archaea Nitrososphaera. The results demonstrate the importance of air mass sources and local weather conditions in shaping the local airborne archaea community.

The source and transport of bioaerosols in the air: A review

Recent pandemic outbreak of the corona-virus disease 2019 (COVID-19) has raised widespread concerns about the importance of the bioaerosols. They are atmospheric aerosol particles of biological origins, mainly including bacteria, fungi, viruses, pollen, and cell debris. Bioaerosols can exert a substantial impact on ecosystems, climate change, air quality, and public health. Here, we review several relevant topics on bioaerosols, including sampling and detection techniques, characterization, effects on health and air quality, and control methods. However, very few studies have focused on the source apportionment and transport of bioaerosols. The knowledge of the sources and transport pathways of bioaerosols is essential for a comprehensive understanding of the role microorganisms play in the atmosphere and control the spread of epidemic diseases associated with them. Therefore, this review comprehensively summarizes the up to date progress on the source characteristics, source identification, and diffusion and transport process of bioaerosols. We intercompare three types of diffusion and transport models, with a special emphasis on a widely used mathematical model. This review also highlights the main factors affecting the source emission and transport process, such as biogeographic regions, land-use types, and environmental factors. Finally, this review outlines future perspectives on bioaerosols.

Temporal variability measurements of PM2.5 and its associated metals and microorganisms on a suburban atmosphere in the central Iberian Peninsula

A novel and multidisciplinary observational analysis of atmospheric components in the Central Iberian Peninsula is presented here. PM_2.5 concentrations and both populations of cultivable and non-cultivable microorganisms and concentrations of a wide range of trace elements associated have been simultaneously studied during multiple events along one year. The aim has been to characterize their potential relations and dependencies, and their seasonal, daily and hourly evolution. Tools that could explain the atmospheric mechanisms and sources from all these elements have been also evaluated. As it would be expected from a suburban environment, absolute levels obtained were not close to legislation limits. Anthropogenic and natural sources, such as heating home, soil resuspension, or Sahara dust intrusion; and atmospheric factors are responsible for higher PM_2.5 and metals concentrations in months with both low and high temperatures. Daily and hourly evolution depends on University Campus activity, especially on traffic flow and resuspended dust due to human transit. No statistical significant differences on daily or seasonal scales between cultivable counts of fungi and bacteria were displayed. However, using the q-PCR technique, the bacterial population was lower in winter. Positive correlations between PM_2.5 and relative humidity; and PM_2.5 and cultivable microorganism have been established. It was also the case among 7 of the 11 trace elements, indicating then common natural or anthropogenic sources. In summary, this work illustrates the interest of a combined inspection of elements, interactions and dependencies when studying the unique and continuous atmospheric environment, which are typically analysed separately.

Indoor exposure levels of bacteria and fungi in residences, schools, and offices in China: A systematic review

Microbes in buildings have attracted extensive attention from both the research community and the general public due to their close relationship with human health. However, there still lacks comprehensive information on the indoor exposure level of microbes in China. This study systematically reviews exposure levels, the community structures, and the impact factors of airborne bacteria and fungi in residences, schools, and offices in China. We reviewed the major literature databases between 1980 and 2019 and selected 55 original studies based on a set of criteria. Results show that the concentration of indoor bacteria varies from 72.5 to 7500 CFU/m³ , with a median value of 1000 CFU/m³ , and the concentration of fungi varies from 12 to 9730 CFU/m³ , with a median value of 526 CFU/m³ . The concentration level of microbes varies in different climate zones, with higher bacterial concentrations in the severe cold zone, and higher fungal concentrations in the hot summer and warm winter zone. Among different buildings, classrooms have the highest average bacteria and fungi levels. This review reveals that a unified assessment system based on health effects is needed for evaluating the exposure levels of bacteria and fungi.

Pollution profiles of antibiotic resistance genes associated with airborne opportunistic pathogens from typical area, Pearl River Estuary and their exposure risk to human

To reveal the selective pressures of near-shore human activities on marine and continental bioaerosols, the pollution profile and potential exposure risk of airborne pathogens and antibiotic-resistance genes (ARGs) in Pearl River Estuaries (113.52 ^oE, 22.69 ^oN), a transitional zone between marine and continental environments, were fully explored. The results showed that the total bacteria among bioaerosols varied largely with average pollution levels of 1.86 × 10⁵ and 4.35 × 10⁴ cfu m^-3 in spring and summer, respectively, and were high than those of airborne fungi. The predominant aerodynamic diameters of bioaerosols were in respirable size range (<4.7 µm), and the microbes communities' diversity and abundance varied significantly. Besides, many opportunistic pathogenic bacteria (Burkholderia-Paraburkholderia, Staphylococcus and Acinetobacter) and fungi (Alternaria, Penicillium and Cladosporium) were dominant in bioaerosol samples. Of 21 ARGs subtypes detected, the tetracycline resistance gene tetA was the most abundant, followed by aminoglycoside resistance gene and mobile genetic elements. Correlation analysis revealed that the changes of pathogens community contributed significantly to the prevalence of ARGs in bioaerosol. Based on the average daily dose rates of microorganisms and human direct intake of ARGs, health risk of bioaerosols from the Pearl River Estuaries were also evaluated. In summary, the presence of opportunistic pathogens and diversity of ARGs strengthens the call to consider the bioaerosol in air quality monitoring and risk assessment in the future.

Factors determining the diffusion of COVID-19 and suggested strategy to prevent future accelerated viral infectivity similar to COVID

This study has two goals. The first is to explain the geo-environmental determinants of the accelerated diffusion of COVID-19 that is generating a high level of deaths. The second is to suggest a strategy to cope with future epidemic threats similar to COVID-19 having an accelerated viral infectivity in society. Using data on sample of N = 55 Italian province capitals, and data of infected individuals at as of April 7th, 2020, results reveal that the accelerate and vast diffusion of COVID-19 in North Italy has a high association with air pollution of cities measured with days exceeding the limits set for PM10 (particulate matter 10 μm or less in diameter) or ozone. In particular, hinterland cities with average high number of days exceeding the limits set for PM10 (and also having a low wind speed) have a very high number of infected people on 7th April 2020 (arithmetic mean is about 2200 infected individuals, with average polluted days greater than 80 days per year), whereas coastal cities also having days exceeding the limits set for PM10 or ozone but with high wind speed have about 944.70 average infected individuals, with about 60 average polluted days per year; moreover, cities having more than 100 days of air pollution (exceeding the limits set for PM10), they have a very high average number of infected people (about 3350 infected individuals, 7th April 2020), whereas cities having less than 100 days of air pollution per year, they have a lower average number of infected people (about 1014 individuals). The findings here also suggest that to minimize the impact of future epidemics similar to COVID-19, the max number of days per year that Italian provincial capitals or similar industrialized cities can exceed the limits set for PM10 or for ozone, considering their meteorological conditions, is about 48 days. Moreover, results here reveal that the explanatory variable of air pollution in cities seems to be a more important predictor in the initial phase of diffusion of viral infectivity (on 17th March 2020, b1 = 1.27, p < 0.001) than interpersonal contacts (b2 = 0.31, p < 0.05). In the second phase of maturity of the transmission dynamics of COVID-19, air pollution reduces intensity (on 7th April 2020 with b'1 = 0.81, p < 0.001) also because of the indirect effect of lockdown, whereas regression coefficient of transmission based on interpersonal contacts has a stable level (b'2 = 0.31, p < 0.01). This result reveals that accelerated transmission dynamics of COVID-19 is due to mainly to the mechanism of "air pollution-to-human transmission" (airborne viral infectivity) rather than "human-to-human transmission". Overall, then, transmission dynamics of viral infectivity, such as COVID-19, is due to systemic causes: general factors that are the same for all regions (e.g., biological characteristics of virus, incubation period, etc.) and specific factors which are different for each region and/or city (e.g., complex interaction between air pollution, meteorological conditions and biological characteristics of viral infectivity) and health level of individuals (habits, immune system, age, sex, etc.). Lessons learned for COVID-19 in the case study here suggest that a proactive strategy to cope with future epidemics is also to apply especially an environmental and sustainable policy based on reduction of levels of air pollution mainly in hinterland and polluting cities- (having low wind speed, high percentage of moisture and number of fog days) -that seem to have an environment that foster a fast transmission dynamics of viral infectivity in society. Hence, in the presence of polluting industrialization in regions that can trigger the mechanism of air pollution-to-human transmission dynamics of viral infectivity, this study must conclude that a comprehensive strategy to prevent future epidemics similar to COVID-19 has to be also designed in environmental and socioeconomic terms, that is also based on sustainability science and environmental science, and not only in terms of biology, medicine, healthcare and health sector.

Pollution characteristics of bioaerosols in PM2.5 during the winter heating season in a coastal city of northern China

Frequent heavy air pollution occurred during the winter heating season of northern China. In this study, PM_2.5 (particles with an aerodynamic diameter less than 2.5 μm) was collected from a coastal city of China during the winter heating season from January 1 to March 31, 2018, and the soluble ions, organic carbon (OC), elemental carbon (EC), bacterial, endotoxin, and fungal concentration in PM_2.5 were analyzed. During the winter heating season, PM_2.5 and bioaerosols increased on polluted days, and the secondary inorganic ions, including NO₃^-, NH₄⁺, and SO₄^2-, increased significantly. Meteorological factors, such as wind direction and wind speed, had major impacts on the distributions of PM_2.5 and bioaerosols. Pollutant concentration was high when there was a westerly wind with the speed of 3-6 m/s from inland area. Using the air mass backward trajectories and principal component analysis, we elucidate the potential origins of bioaerosol in PM_2.5. The backward trajectory suggested that air mass for polluted samples (PM_2.5 > 75 μg/m³) commonly originated from continent (9.62%), whereas air masses for clean samples (PM_2.5 < 35 μg/m³) were mainly from marine (56.73%). The interregional transport of pollutants from continental area contributed most to PM_2.5. Principal component analysis of the water-soluble ions and bioaerosol indicated that air pollution of the coastal city was greatly affected by coal combustion, biomass burning, and regional transmission of high-intensity pollutants from continent. Among that, interregional transport, biomass burning, and dust from soil and plants were main sources of bioaerosol. Our findings provide important insights into the origins and characteristics of bioaerosol in PM_2.5 during the winter heating season of the coastal city in northern China.

Effects of aerosol pollution on PM2.5-associated bacteria in typical inland and coastal cities of northern China during the winter heating season

Frequent heavy aerosol pollution occurs during the winter heating season in northern China. Here, we characterized the airborne bacterial community structure and concentration, during typical pollution episodes that occurred during the winter heating season of 2017-2018 in Jinan and Weihai. During this heating season, five and four heavy pollution episodes were observed in Jinan and Weihai, respectively. Compared with December and January, pollution episodes in March were significantly affected by sand dust events. Higher Bacillales were identified in the March samples from Jinan, indicating that sand dust influences bacterial communities. During similar pollution episodes, air pollution in the coastal city of Weihai was lower than the inland city of Jinan. The predominant bacteria included Staphylococcus, Cyanobacteria, Lactobacillus, Deinococcus, Enbydrobacter, Ralstonia, Bacillus, Comamonas, and Sphingomonas. These predominant bacteria are mainly from Proteobacteria, Firmicutes, Cyanobacteria, Actinobacteria, and Bacteroidetes phyla. Bacterial concentration showed significant variation with increased airborne pollutants. The highest concentration appeared during moderate pollution (up to 10⁶ cells/m³), whereas bacterial concentration decreased during heavy and severe pollution (10⁵ cells/m³), which may be related to toxic effects of high pollutant concentrations during heavy or severe pollution. Community structure variation indicated that Cyanobacterial genera were dominant in clean or slight pollution. With increased PM_2.5, Staphylococcus increased and became the most abundant bacteria in moderate pollution (up to 40%). During heavy or severe pollution, bacteria that are adaptable to harsh or extreme environments predominate, such as Deinococcus and Bacillus. In the assessment of health risks from air pollution, the bioaerosols risks must consider. Additionally, although most microbial genera are similar between the two cities, there are important differences associated with pollution level. During air pollution regulation in different regions with varied geographical and climatic conditions, bioaerosol pollution difference is an unignored factor.

Ambient bioaerosol distribution and associated health risks at a high traffic density junction at Dehradun city, India

Traffic junctions are one of the crowded places where commuters are at high risk of developing respiratory infections, due to their greater exposure to airborne and human transmitted microbial pathogens. An airborne bioaerosol assessment study was carried out at a high traffic density junction focusing on their concentration, contribution in respirable particulate matter (PM), and factors influencing the distribution and microbial diversity. Andersen six-stage viable cascade impactor and a wide-range aerosol spectrometer were used for microbial and particulate matter measurements, respectively. Statistical analysis was conducted to evaluate the relationship between bioaerosol concentration, vehicular count, PM concentration, and meteorological parameters. The mean bacteria concentration (1962.95 ± 651.85 CFU/m3) was significantly different than fungi (1118.95 ± 428.34 CFU/m3) (p < 0.05). The temporal distribution showed maximum concentration for bacteria and fungi during monsoon and postmonsoon seasons, respectively. In terms of bioaerosol loading, a considerable fraction of fungi (3.25%) and bacteria (5.65%) contributed to the total airborne PM. Most abundant bioaerosols were Aspergillus (27.58%), Penicillium (23%), and Cladosporium (14.05%) (fungi), and Micrococcus (25.73%), Staphylococcus (17.98%), and Bacillus (13.8%) (bacteria). Traffic-induced roadside soil resuspension and microbial aerosolizations from the human body were identified as the chief sources of bioaerosol emissions. The risk of lower respiratory tract infections caused by anthroponotic (human transmitted) transfer of bacterial pathogens is very high. The results of the study can be used to trace sources of microbial mediated communicable diseases, and to recommend appropriate safety measures to avoid pathogenic bioaerosol exposure.

Research Progress of HP Characteristics, Hazards, Control Technologies, and Measures in China after 2013

In recent years, hazy weather (hazy weather (HW) has frequently invaded peoples’ lives in China, resulting in the disturbance of social operation, so it is urgent to resolve the haze pollution (HP) problem. A comprehensive understanding of HP is essential to further effectively alleviate or even eliminate it. In this study, HP characteristics in China, after 2013, were presented. It was found that the situation of HP is getting better year by year while it has been a pattern of high levels in the north and low levels in the south. In most regions of China, the contribution of a secondary source for HP is relatively large, and that of traffic is greater in the regions with rapid economic development. Hazards of HP were then summarized. Not only does HP cause harm to human health, but it also has effects on human production and quality of life, furthermore, property and atmospheric environment cannot be ignored. Next, the source and non-source control technologies of HP were first reviewed to recognize the weakness of HP control in China. This review provides more systematic information about HP problems and the future development directions of HP research were proposed to further effectively control HP in China.

Distribution characteristics and noncarcinogenic risk assessment of culturable airborne bacteria and fungi during winter in Xinxiang, China

Bioaerosols are an important component of particulate matter in the atmosphere and are harmful to human health. In this study, the concentration, size distribution, and factors influencing culturable airborne bacteria and fungi in the atmosphere were investigated using a six-stage impactor device in the city of Xinxiang, China, during the winter season. The results revealed that the concentration of culturable airborne bacteria and fungi varied significantly during the sampling period: 4595 ± 3410 and 6358 ± 5032 CFU/m³, respectively. The particle sizes of the bioaerosols were mainly within stage V (1.1-2.1 μm), and fine particulate matter accounted for 45.9% ± 18.9% of airborne bacteria and 52.0% ± 18.5% of airborne fungi, respectively. With the deterioration of air quality, the concentration of airborne fungi gradually increased, and that of airborne bacteria increased when the air quality index was lower than 200 and decreased when it was higher than 200. With respect to the diurnal variation pattern of bioaerosol concentration, the highest and lowest concentrations were registered at night and noon, respectively, probably because of changes in ultraviolet radiation intensity. Bioaerosol concentration positively correlated with humidity, concentration of PM_2.5, PM₁₀, SO₂, and NO₂ and negatively correlated with O₃ concentration. The risk of exposure of humans to the airborne bacteria was primarily associated with the respiratory inhalation pathway, and the risk of skin exposure was negligible. These results should improve our understanding of the threat of bioaerosols to public health.

Characteristics of biological particulate matters at urban and rural sites in the North China Plain

Depending on their concentrations, sizes, and types, particulate matters of biological origins (bioPM) significantly affect human health. However, for different air environments, they are not well characterized and can vary considerably. As an example, we investigated the bioPM differences at an urban (Beijing) site and a rural (Wangdu) site in the North China Plain (NCP) using an online monitoring instrument, an ultraviolet aerodynamic particle sizer (UV-APS), the limulus amebocyte lysate (LAL) assay, and a high-throughput sequencing method. Generally, lower concentrations of viable bioPM (hourly mean: 1.3 × 10³ ± 1.6 × 10³ m^-3) and endotoxin (0.66 ± 0.16 EU/m³) in Beijing were observed compared to viable bioPM (0.79 × 10⁵ ± 1.4 × 10⁵ m^-3) and endotoxin (15.1 ± 23.96 EU/m³) at the Wangdu site. The percentage of viable bioPM number concentration in the total PM was 3.1% in Beijing and 6.4% in Wangdu. Approximately 80% of viable bioPM was found to be in the range from 1 to 2.5 μm. Nevertheless, the size distribution patterns for viable bioPM at the Beijing and Wangdu sites differed and were affected by PM pollution, leading to distinct lung deposition profiles. Moreover, the distinct diurnal variations in viable bioPM on clean days were dimmed by the PM pollution at both sites. Distinct bacterial community structures were found in the air from the Beijing and Wangdu sites. The bacterial community in urban Beijing was dominated by genus Lactococcus (49.5%) and Pseudomonas (15.1%), while the rural Wangdu site was dominated by Enterococcus (65%) and Paenibacillus (10%). Human-derived genera, including Myroides, Streptococcus, Propionibacterium, Dietzia, Helcococcus, and Facklamia, were higher in Beijing, suggesting bacterial emission from humans in the urban air environment. Our results show that different air harbors different biological species, and people residing in different environments thus could have very different biological particle exposure.