Microbial aerosol chemistry characteristics in highly polluted air

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.

Ambient particle composition and toxicity in 31 major cities in China

Current assessment of air quality or control effectiveness is solely based on particulate matter (PM) mass levels, without considering their toxicity differences in terms of health benefits. Here, we collected a total of 465 automobile air conditioning filters from 31 major Chinese cities to study the composition and toxicity of PM at a national scale. Dithiothreitol assay showed that normalized PM toxicity (NIOG) in different Chinese cities varied greatly from the highest 4.99 × 10-3 for Changsha to the lowest 7.72 × 10-4 for Yinchuan. NIOG values were observed to have significant correlations with annual PM10 concentration (r = -0.416, p = 0.020) and some PM components (total fungi, SO4 2- and calcium element). The concentrations of different elements and water-soluble ions in PM also varied by several orders of magnitude for 31 cities in China. Endotoxin concentrations in PM analyzed using limulus amebocyte lysate assay ranged from 2.88 EU/mg PM (Hangzhou) to 62.82 EU/mg PM (Shijiazhuang) among 31 Chinese cities. Besides, real-time qPCR revealed 10∼100-fold differences in total bacterial and fungal levels among 31 Chinese cities. The concentrations of chemical (water soluble ions and trace elements) and biological (fungi, bacteria and endotoxin) components in PM were found to be significantly correlated with some meteorological factors and gaseous pollutants such as SO2. Our results have demonstrated that PM toxicity from 31 major cities varied greatly up to 6.5 times difference; and components such as fungi and SO4 2- in PM could play important roles in the observed PM toxicity. The city-specific air pollution control strategy that integrates toxicity factors should be enacted in order to maximize health and economic co-benefits. This work also provides a comprehensive view on the overall PM pollution situation in China.

Contribution of Particulates to Airborne Disease Transmission and Severity: A Review

The emergence of coronavirus disease 2019 (COVID-19) has catalyzed great interest in the spread of airborne pathogens. Airborne infectious diseases are classified into viral, bacterial, and fungal infections. Environmental factors can elevate their transmission and lethality. Air pollution has been reported as the leading environmental cause of disease and premature death worldwide. Notably, ambient particulates of various components and sizes are harmful pollutants. There are two prominent health effects of particles in the atmosphere: (1) particulate matter (PM) penetrates the respiratory tract and adversely affects health, such as heart and respiratory diseases; and (2) bioaerosols of particles act as a medium for the spread of pathogens in the air. Particulates contribute to the occurrence of infectious diseases by increasing vulnerability to infection through inhalation and spreading disease through interactions with airborne pathogens. Here, we focus on the synergistic effects of airborne particulates on infectious disease. We outline the concepts and characteristics of bioaerosols, from their generation to transformation and circulation on Earth. Considering that microorganisms coexist with other particulates as bioaerosols, we investigate studies examining respiratory infections associated with airborne PM. Furthermore, we discuss four factors (meteorological, biological, physical, and chemical) that may impact the influence of PM on the survival of contagious pathogens in the atmosphere. Our review highlights the significant role of particulates in supporting the transmission of infectious aerosols and emphasizes the need for further research in this area.

The exposure risks associated with pathogens and antibiotic resistance genes in bioaerosol from municipal landfill and surrounding area

Pathogenic microbes with antibiotic resistance can thrive on municipal solid waste as nutrients and be aerosolized and transported to vicinities during waste disposal processes. However, the characterization of pathogenic bioaerosols and assessment of their exposure risks are lacking. Herein, particle size, concentration, activity, antibiotic resistance, and pathogenicity of airborne microorganisms were assessed in different sectors of a typical landfill. Results showed that active sector in downwind direction has the highest bioaerosol level (1234 CFU/m³), while residential area has the highest activity (14.82 mg/L). Botanical deodorizer from mist cannon can effectively remove bioaerosol. Most bioaerosols can be inhaled into respiratory system till bronchi with sizes ranging from 2.1-3.3 and 3.3-4.7 µm. Pathogenic bacteria (Bacilli, Bacillus, and Burkholderia-Paraburkholderia) and allergenic fungi (Aspergillus, Cladosporium, and Curvularia) prevailed in landfill. Although high abundance of microbial volatile organic compounds (mVOCs) producing bioaerosols were detected, these mVOCs contributed little to odor issues in landfill. Notably, surrounding areas have higher levels of antibiotic-resistance genes (ARGs) than inner landfill with tetC, acrB, acrF, mdtF, and bacA as dominant ones. Most ARGs were significantly correlated with bacterial community, while environmental parameters mainly influenced fungal prevalence. These findings can assist in reducing and preventing respiratory allergy or infection risks in occupational environments relating to waste management.

Inhalable particle-bound marine biotoxins in a coastal atmosphere: Concentration levels, influencing factors and health risks

Characterizing marine biotoxins (MBs) composition in coastal aerosol particles has become essential to tracking sources of atmospheric contaminants and assessing human inhalable exposure risks to air particles. Here, coastal aerosol particles were collected over an almost 3-year period for the analysis of eight representative MBs, including brevetoxin (BTX), okadaic acid (OA), pectenotoxin-2 (PTX-2), domoic acid (DA), tetrodotoxin (TTX), saxitoxin (STX), ciguatoxin (CTX) and ω-Conotoxin. Our data showed that the levels of inhalable airborne marine biotoxins (AMBs) varied greatly among the subcategories and over time. Both in daytime and nighttime, a predominance of coarse-mode AMB particles was found for all the target AMBs. Based on the experimental data, we speculate that an ambient AMB might have multiple sources/production pathways, which include air-sea aerosol production and direct generation and release from toxigenic microalgae/bacteria suspended in surface seawater or air, and different sources may make different contribution. Regardless of the subcategory, the highest deposition efficiency of an individual AMB was found in the head airway region, followed by the alveolar and tracheobronchial regions. This study provides new information about inhalable MBs in the coastal atmosphere. The coexistence of various particle-bound MBs raises concerns about potential health risks from exposure to coastal air particles.

High time-resolved variations of proteins in PM2.5 during haze pollution periods in Xi'an, China

Proteinaceous matter is an important component of PM_2.5, which can cause adverse health effects and also influence the air quality and climate change. However, there is little attention to high time-resolved variations and potential role of aerosol proteins during haze pollution periods. In this study, PM_2.5 samples were first collected by a medium flow sampler in autumn and winter in Xi'an, China. Then three high time-resolved monitoring campaigns during haze pollution periods were conducted to determine the evolving characteristics of total protein concentration and explore the interactive relationship between protein and other chemical compositions. The results showed that the average protein concentration in PM_2.5 in Xi'an (5.46 ± 3.32 μg m^-3) was higher than those in most cities of China, and varied by seasons and air pollution conditions. In particular, the protein concentration in PM_2.5 increased with the increase of air quality index (AQI). The continuous variations of aerosol proteins during the haze pollution periods further showed that PM_2.5, atmospheric humidity and long-distance air mass transport exerted the significant impacts on the protein components in aerosols. Based on the present observation, it is suggested that aerosol proteins might affect the generation of secondary aerosols under haze weather conditions. The present results may provide a new possible insight into the variations and the role of aerosol proteinaceous matter during the formation and development of haze pollution.

Release of inhalable particles and viable microbes to the air during packaging peeling: Emission profiles and mechanisms

Packaging is necessary for preserving and delivering products and has significant impacts on human health and the environment. Particle matter (PM) may be released from packages and transferred to the air during a typical peeling process, but little is known about this package-to-air migration route of particles. Here, we investigated the emission profiles of total and biological particles, and the horizontal and vertical dispersion abilities and community structure of viable microbes released from packaging to the air by peeling. The results revealed that a lot of inhalable particles and viable microbes were released from package to the air in different migration directions, and this migration can be regulated by several factors including package material, effective peeling area, peeling speed and angles, as well as the characteristics of the migrant itself. Dispersal of package-borne viable microbes provides direct evidence that viable microbes, including pathogens, can survive the aerosolization caused by peeling and be transferred to air over different distances while remaining alive. Based on the experimental data and visual proof in movies, we speculate that nonbiological particles are package fibers fractured and released to air by the external peeling force exerted on the package and that microbe dispersal is attributed to surface-borne microbe suspension by vibration caused by the peeling force. This investigation provides new information that aerosolized particles can deliver package-borne substances and viable microbes from packaging to the ambient environment, motivating further studies to characterize the health effects of such aerosolized particles and the geographic migration of microbes via packaging.

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.

The effect of human settlement temperature and humidity on the growth rules of infected and recovered cases of COVID-19

This study investigated the impact of humidity and temperature on the spread of COVID-19 (SARS-CoV-2) by statistically comparing modelled pandemic dynamics (daily infection and recovery cases) with daily temperature and humidity of three climate zones (Mainland China, South America and Africa) from January to August 2020. We modelled the pandemic growth using a simple logistic function to derive information of the viral infection and describe the growth of infected and recovered cases. The results indicate that the infected and recovered cases of the first wave were controlled in China and managed in both South America and Africa. There is a negative correlation between both humidity (r = - 0.21; p = 0.27) and temperature (r = -0.22; p = 0.24) with spread of the virus. Though this study did not fully encompass socio-cultural factors, we recognise that local government responses, general health policies, population density and transportation could also affect the spread of the virus. The pandemic can be managed better in the second wave if stricter safety protocols are implemented. We urge various units to collaborate strongly and call on countries to adhere to stronger safety protocols in the second wave.

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.

Dispersion of Antibiotic Resistance Genes (ARGs) from stored swine manure biogas digestate to the atmosphere

Biogas digestate is a reservoir of antibiotic resistance genes (ARGs) and could pose a high health risk to both human and animals if the host microorganisms of ARGs become aerosolized. The purpose of this study was to investigate the diversity and relative abundance characteristics of aerosol-loaded ARGs from biogas digestate during storage, and to explore whether the change of ARGs in biogas digestate directly affect the dispersion of aerosol-loaded ARGs. This study reported for the first time that 28 of 42 ARG subtypes detected in the biogas digestate could be dispersed to the atmosphere via aerosol dispersion in a lab-scale dynamic emission vessels experiment. The relative abundance or diversity of ARGs in aerosols were different from that in biogas digestate, and no significant correlation were observed between the relative abundance of ARGs in biogas digestate and aerosols. The dominant ARGs were tetracycline resistance genes in biogas digestate and β-lactam resistance genes in aerosols. The process of biogas digestate storage reduced the total relative abundance of targeted ARGs in biogas digestate, decreased by 0.35 copies/16S rRNA after 30 days of storage, but increased the abundance of some ARG subtypes, including tetM, tetX, tetQ, tetS, ermF and sul2. High-concerned ARGs, including NDM-1, mcr-1 and vancomycin resistance genes (including vanA, vanB, vanRA and vanSA), were found in biogas digestate, and NDM-1 and vanB were also detected in aerosols. These results indicated a potential risk of ARGs dispersion during biogas digestate storage. Further research on the dispersion of ARGs from biogas digestate is required to elucidate the emission mechanism and develop mitigation measures.

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.

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.

Two mechanisms for accelerated diffusion of COVID-19 outbreaks in regions with high intensity of population and polluting industrialization: the air pollution-to-human and human-to-human transmission dynamics (Preprint).. [DOI: 10.2196/preprints.19331]

BACKGROUND

Coronavirus disease 2019 (COVID-19) is viral infection that generates a severe acute respiratory syndrome with serious pneumonia that may result in progressive respiratory failure and death.

OBJECTIVE

This study has two goals. The first is to explain the main factors determining the 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 with of accelerated viral infectivity in society.

METHODS

Correlation and regression analyses on on data of N=55 Italian province capitals, and data of infected individuals at as of April 2020.

RESULTS

The main results are: o The accelerate and vast diffusion of COVID-19 in North Italy has a high association with air pollution. o Hinterland cities have average days of exceeding the limits set for PM10 (particulate matter 10 micrometers or less in diameter) equal to 80 days, and an average number of infected more than 2,000 individuals as of April 1st, 2020, coastal cities have days of exceeding the limits set for PM10 equal to 60 days and have about 700 infected in average. o Cities that average number of 125 days exceeding the limits set for PM10, last year, they have an average number of infected individual higher than 3,200 units, whereas cities having less than 100 days (average number of 48 days) exceeding the limits set for PM10, they have an average number of about 900 infected individuals. o The results reveal that accelerated transmission dynamics of COVID-19 in specific environments is due to two mechanisms given by: air pollution-to-human transmission and human-to-human transmission; in particular, the mechanisms of air pollution-to-human transmission play a critical role rather than human-to-human transmission. o The finding here suggests that to minimize future epidemic similar to COVID-19, the max number of days per year in which cities can exceed the limits set for PM10 or for ozone, considering their meteorological condition, is less than 50 days. After this critical threshold, the analytical output here suggests that environmental inconsistencies because of the combination between air pollution and meteorological conditions (with high moisture%, low wind speed and fog) trigger a take-off of viral infectivity (accelerated epidemic diffusion) with damages for health of population, economy and society.

CONCLUSIONS

Considering the complex interaction between air pollution, meteorological conditions and biological characteristics of viral infectivity, lessons learned for COVID-19 have to be applied for a proactive socioeconomic strategy to cope with future epidemics, especially an environmental policy based on reduction of air pollution mainly in hinterland zones of countries, having low wind speed, high percentage of moisture and fog that create an environment that can damage immune system of people and foster a fast transmission of viral infectivity similar to the COVID-19.

CLINICALTRIAL

not applicable

Functional metagenomic analysis of dust-associated microbiomes above the Red Sea

Atmospheric transport is a major vector for the long-range transport of microbial communities, maintaining connectivity among them and delivering functionally important microbes, such as pathogens. Though the taxonomic diversity of aeolian microorganisms is well characterized, the genomic functional traits underpinning their survival during atmospheric transport are poorly characterized. Here we use functional metagenomics of dust samples collected on the Global Dust Belt to initiate a Gene Catalogue of Aeolian Microbiome (GCAM) and explore microbial genetic traits enabling a successful aeolian lifestyle in Aeolian microbial communities. The GCAM reported here, derived from ten aeolian microbial metagenomes, includes a total of 2,370,956 non-redundant coding DNA sequences, corresponding to a yield of ~31 × 10⁶ predicted genes per Tera base-pair of DNA sequenced for the aeolian samples sequenced. Two-thirds of the cataloged genes were assigned to bacteria, followed by eukaryotes (5.4%), archaea (1.1%), and viruses (0.69%). Genes encoding proteins involved in repairing UV-induced DNA damage and aerosolization of cells were ubiquitous across samples, and appear as fundamental requirements for the aeolian lifestyle, while genes coding for other important functions supporting the aeolian lifestyle (chemotaxis, aerotaxis, germination, thermal resistance, sporulation, and biofilm formation) varied among the communities sampled.