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The association between PM 2.5 (particulate matter ≤ 2.5 µm) short-term exposure and its health effect is non-linear from the epidemiological studies. And this nonlinearity is suggested to be related with the PM 2.5 heterogeneity, however, the underlying biological mechanism is still unclear. Here, a total of 38 PM 2.5 filters were collected continuously for three weeks in winter Beijing, with the ambient PM 2.5 varying between 10 and 270 µg/m 3 . Human monocytes-derived macrophages (THP-1) were treated with PM 2.5 water-soluble elutes at 10 µg/mL to investigate the PM 2.5 short-term exposure effect from a proinflammatory perspective. The proinflammatory cytokine tumor necrosis factor (TNF) induced by the PM 2.5 elutes at equal concentrations were unequal, showing the heterogeneity of PM 2.5 proinflammatory potentials. Of the various chemical and biological components, lipopolysaccharide (LPS) showed a strong positive association with the TNF heterogeneity. However, some outliers were observed among the TNF-LPS association. Specifically, for PM 2.5 from relatively clean air episodes, the higher LPS amount corresponded to relatively low TNF levels. And this phenomenon was also observed in the promotion tests by treating macrophages with PM 2.5 elutes dosed with additional trace LPS. Gene expression analysis indicated the involvement of oxidative-stress related genes in the LPS signaling pathway. Therefore, a potential oxidative-stress-mediated suppression on the PM 2.5 -borne LPS proinflammatory effect was proposed to be accounted for the outliers. Overall, the results showed the differential role of LPS in the heterogeneity of PM 2.5 proinflammatory effects from a component-based perspective. Future experimental studies are needed to elucidate the signaling pathway of LPS attached on PM 2.5 from different air quality episodes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

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 10 1 to 10 3  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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Aerosols of biological origins, known as bioaerosols, in addition to having the aerosol properties, have those of a living system that offers them some enabling functionalities. From science to technology, visible progress around the world has been made in bioaerosol field before and especially during the COVID-19 pandemic. Here the roles of bioaerosol across various disciplines, including air quality, climate and human health are highlighted and appreciated in light of Anthropocene and one health concept. In particular, we recognized the importance of aerobiology under haze air pollution, allergenic pollen and bioaerosol involvement in infectious and inflammation-related non-communicable diseases. Future interdisciplinary studies focusing on the chemical and biological process of microorganisms in air, airborne transmission of emerging pathogens and allergens and the association between bioaerosol exposure and the development and variations of human microbiome and immune response are needed to elucidate the interactions of bioaerosols with the earth system.

Air pollution and climate change are potential drivers for the increasing burden of allergic diseases. The molecular mechanisms by which air pollutants and climate parameters may influence allergic diseases, however, are complex and elusive. This article provides an overview of physical, chemical and biological interactions between air pollution, climate change, allergens, adjuvants and the immune system, addressing how these interactions may promote the development of allergies. We reviewed and synthesized key findings from atmospheric, climate, and biomedical research. The current state of knowledge, open questions, and future research perspectives are outlined and discussed. The Anthropocene, as the present era of globally pervasive anthropogenic influence on planet Earth and, thus, on the human environment, is characterized by a strong increase of carbon dioxide, ozone, nitrogen oxides, and combustion- or traffic-related particulate matter in the atmosphere. These environmental factors can enhance the abundance and induce chemical modifications of allergens, increase oxidative stress in the human body, and skew the immune system toward allergic reactions. In particular, air pollutants can act as adjuvants and alter the immunogenicity of allergenic proteins, while climate change affects the atmospheric abundance and human exposure to bioaerosols and aeroallergens. To fully understand and effectively mitigate the adverse effects of air pollution and climate change on allergic diseases, several challenges remain to be resolved. Among these are the identification and quantification of immunochemical reaction pathways involving allergens and adjuvants under relevant environmental and physiological conditions.

Interactions of particulate matter (PM) and respiratory tract play a crucial role in PM-related respiratory diseases. The majority of the work focuses on the oxidative stress induced by reactions between PM-borne redox-active components and lung lining fluid (LLF). The effects of PM-borne biological components are largely unknown. Of all PM-borne biologicals, bacteria, as living microorganisms, are closely related with inflammatory immune responses. However, its inhalation risk is usually determined without considering the respiratory physiological conditions. In this study, a surrogate lung fluid (SLF) with four typical antioxidants was applied to characterize the ambient bacteria, including concentrations of total bacteria/viable bacteria/culturable bacteria, metabolic activity, bacteria-derived endotoxin, as well as the community structure. Comparing to those determined by SLF, we find that use of PBS leads to an underestimation of the bacterial culturability and metabolic activity. No effect was seen regarding the number of total bacteria and viable bacteria (with intact membrane). Population structure change was seen for bacteria cultured from SLF-collected samples, when compared to that from PBS. Spore-forming bacteria, e.g., genus Bacillus , were found to be easily recovered with SLF. This implies that use of PBS could underestimate the bacteria inhalation risk, especially those bacterial endospores. Our work highlights the necessity to consider the respiratory airway environment when evaluating microbial inhalation risk. Unlabelled Image • Surrogate lung fluid (SLF) was applied to assess the lung-bioaerosol interaction. • Bacterial aerosols were characterized with SLF under different levels of air quality. • The culturability and metabolic activity of bacterial aerosols were enhanced by SLF. • Spore-forming bacteria are prone to recover and outgrow within SLF. • Bacterial exposure risk was underrated without considering lung fluid. [ABSTRACT FROM AUTHOR]

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. Image 1 • The PM of biological origins (bioPM) in urban Beijing and rural Wangdu were compared. • Viable bioPM in Beijing peaked around ∼2 μm, while below 2 μm in Wangdu. • Particulate air pollution dimmed the diurnal variation of viable bioPM. • The airborne bacterial communities showed large disparities between Beijing and Wangdu. • Human-derived bacterial genera contributed more to the air of urban Beijing. Urban and rural populations are exposed to distinct ambient bioPM communities. Humans themselves play a role in shaping the structure of bioPM in densely populated urban areas. [ABSTRACT FROM AUTHOR]

Exposure to indoor airborne microbiomes (bioaerosols) is closely associated with human health. However, knowledge regarding the characteristics of indoor bioaerosols in areas affected by serious ambient air pollution is still limited. In this study, indoor bioaerosols were characterized in winter Beijing via quantitative polymerase chain reaction (qPCR) and amplicon sequencing, and compared to outdoor bioaerosols. Concentrations of indoor bioaerosol were significantly lower than those of the adjacent outdoor bioaerosol, and were not significantly affected by outdoor air pollution. Community structures of indoor bioaerosol were distinct from those of outdoor environment, and were differentially affected by ambient air pollution. Specifically, significant change was observed in indoor fungal community impacted by hazy air pollution, while not in bacteria and archaea. Compared to outdoor air, indoor air was preferentially enriched with fungi (~10%) in winter. Besides, about 40% of the bacteria indoors were likely contributed by outdoor bacteria. The results provide useful information regarding the impact of ambient air pollution on indoor bioaerosols, and furtherly highlight the distinction between indoor and outdoor bioaerosol assemblies. [Display omitted] • Impact of winter haze pollution on indoor airborne bacteria, fungi and archaea was delineated. • The abundance and diversity of indoor bioaerosols were lower than those outdoors. • The percentage of fungi in bioaerosols indoors was higher that outdoors. • Nearly 40% of indoor bacterial communities were contributed by outdoor air. • Ambient haze pollution differentially affected the indoor and outdoor fungal aerosols. [ABSTRACT FROM AUTHOR]