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The severe cases of COVID-19 infections in Italy, and notably in Lombardy (mainly in Brescia and Bergamo areas), registered at the beginning of March 2020, occurred after a period of PM 10 pollution, that exceeded the concentration of 50 μg/m 3 (the attention limit) for several days. The two events were supposed to be correlated, also based on the limited information available about the new virus. Despite that clear indications about the role of particulate matter (PM) in the virus mechanism dispersion cannot be found in literature, some researchers supposed that PM can act as virus carrier, promoting its diffusion through the air. This paper, for the first time, analyses the PM 10 situation in Lombardy (from 10th February to March 27, 2020), several days before the sanitary emergency explosion. The data of the detected infection cases are reported and discussed parallelly. As a comparison, the situation of Piedmont, located near to the Lombardy is also presented. Data are reported for Brescia, Bergamo, Cremona, Lodi, Milano, Monza-Brianza, Pavia (Lombardy), Alessandria, Vercelli, Novara, Biella, Asti, and Torino (Piedmont). The results show that it is not possible to conclude that COVID-19 diffusion mechanism also occurs through the air, by using PM 10 as a carrier. In particular, it is shown that Piedmont cities, presenting lower detected infections cases in comparison to Brescia and Bergamo in the investigated period, had most sever PM 10 pollution events in comparison to Lombardy cities. This first study may serve as a reference to better understand and predict the factors affecting the COVID-19 diffusion and transmission routes, focusing on the role of air particulate matter in the atmosphere., Competing Interests: Declaration of competing interest The author declares that she has no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Bacteria are ubiquitous throughout the earth's lower atmosphere. Bacteria, especially pathogenic bacteria, play an important role in human health. The diversity, composition, and dynamics of airborne bacteria has been widely studied; however, the characteristics of pathogenic bacteria remain poorly understood. In this study, a high throughput sequencing method was used to explore the airborne opportunistic pathogenic bacteria during autumn and winter in Xi'an, China. An aggregated boosted tree (ABT) was developed to determine the relative influence of environmental factors on the proportions of opportunistic pathogenic bacteria. Results showed that significantly more opportunistic pathogenic bacteria were found in winter than in autumn, and more opportunistic pathogenic bacteria were found in fine particulate matters (<2.5 μm) than in PM 10 (<10 μm). However, the composition of opportunistic pathogenic bacteria varied in autumn and winter. PM was the main factor affecting the proportions of opportunistic pathogenic bacteria, and air contaminants (PM, sulfur dioxide, nitrogen oxide, carbon monoxide, and ozone) influenced the proportion of opportunistic pathogenic bacteria more than meteorological factors (relative humidity, temperature, and wind speed). Different factors may be responsible for the variances in opportunistic pathogenic bacterial communities in different seasons. This study may provide a reference to support the control of pathogenic bacteria in urban environments during haze events., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Poor indoor air quality can have adverse effects on human health, especially in susceptible populations; however, few studies have measured multiple pollutants in facilities for susceptible populations at a national scale in South Korea. Therefore, we measured the concentrations of indoor pollutants (fine particulate matter (PM 10 ), CO 2 , airborne bacteria (AB), total volatile organic compounds (TVOCs), and formaldehyde) to determine their possible relation to other indoor environmental factors and characteristics of facilities with susceptible populations, such as hospitals, geriatric hospitals, elderly care facilities, and postnatal care centers throughout South Korea. Indoor pollutants were sampled at 82 indoor facilities, including 62 facilities for susceptible populations. Spearman's correlation, Kruskal-Wallis, and Mann-Whitney analyses were used to examine the relationship among and differences between pollutants at indoor facilities and indoor/outdoor differences in PM 10 concentration. There were significant correlations between indoor temperature and AB concentration (r = 0.37, p < 0.01), TVOCs, and formaldehyde (r = 0.264, p < 0.01). Indoor PM 10 concentrations were higher than outdoor concentrations at all facilities for susceptible populations (p < 0.01). CO 2 might be a good indicator for predicting indoor pollutants when categorized into two levels (≤750 ppm and >750 ppm). The hazard quotient of formaldehyde was higher than the acceptable level of 1 for children under the age of eight in postnatal care centers, indicative of unsafe levels. Therefore, more depth study for exposure characteristics of formaldehyde and indoor air quality (IAQ) in postnatal care facilities as a national scale is needed for finding the children exposure levels., (Copyright © 2018. Published by Elsevier Ltd.)

Airborne bacteria were measured when a dust storm passed Beijing in spring 2012 with a focus on cell concentration, viability and TSA- and R2A-cultured strain composition. The concentration varied at an order of 10 7 cells/m 3 with dust loading (demonstrated with PM 10 ) and they had a very close correlation (R T 2 =0.91, p<0.01). At the time of highest PM 10 of 652μg/m 3 , the bacterial concentration reached 1.4×10 8 cells/m 3 , which was larger than that before and after the dust event by one order. Bacterial viability, the ratio of number concentration of viable cells to total cells, was 32%-64% and smaller in the dust plume than that before the dust arrival. Bacterial strains from the culture ranged between 2.5×10 4 and 4.6×10 5 CFU/m 3 and no correlation with PM 10 was determined. Their composition was different before and after the dust arrival according to 16S rRNA gene sequences and strains belong to Actinomycetes and Firmicutes were the majority in the dust samples., (Copyright © 2016. Published by Elsevier B.V.)

Recently, inhalable particulate matter has been reported to carry microorganisms responsible for human allergy and respiratory disease. The unique geographical environment and adverse weather conditions of Urumqi cause double pollution of dust and smog, but research on the microbial content of the atmosphere has not been commenced. In this study, 16S and 18S rRNA gene sequencing were conducted to investigate the microbial composition of Urumqi's PM1 and PM10 pollutants in winter. Results showed that the bacterial community is mainly composed of Proteobacteria, Firmicutes and Actinobacteria, Proteobacteria accounted for the most proportion which was significant difference in some aforementioned studies. Ascomycota and Basidiomycota constitute the main part of the fungal microbial community. The difference of bacterial relative abundance in sample point is greater than in particle sizes. The sequences of several pathogenic bacteria and opportunistic pathogens were also detected, such as Acinetobacter, Delftia, Serratia, Chryseobacterium, which may impact on immunocompromised populations (elderly, children and postoperative convalescence patients), and some fungal genera may cause several plant diseases. Our findings may serve an important reference value in the global air microbial propagation and air microbial research in desert., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

This study aims to determine the microbiological quality of particulate matter (PM) in an urban area in Jeddah, Saudi Arabia, during December 2012 to April 2013. This was achieved by the determination of airborne bacteria, fungi, and actinobacteria associated PM10 and PM2.5, as well as their relationships with gaseous pollutants, O3, SO2 and NO2, and meteorological factors (T°C, RH% and Ws). High volume samplers with PM10 and PM2.5 selective sizes, and glass fiber filters were used to collect PM10 and PM2.5, respectively. The filters were suspended in buffer phosphate and aliquots were spread plated onto the surfaces of trypticase soy agar, malt extract agar, and starch casein agar media for counting of bacteria, fungi and actinobacteria-associated PM, respectively. PM10 and PM2.5 concentrations averaged 159.9 μg/m(3) and 60 μg/m(3), respectively, with the ratio of PM2.5/PM10 averaged ~0.4. The concentrations of O3, SO2 and NO2 averaged 35.73 μg/m(3), 38.1μg/m(3) and 52.5 μg/m(3), respectively. Fungi and actinobacteria associated PM were found in lower concentrations than bacteria. The sum of microbial loads was higher in PM10 than PM2.5, however a significant correlation (r=0.57, P ≤ 0.05) was found between the sum of microbial loads associated PM10 and PM2.5. Aspergillus fumigatus and Aspergillus niger were the common fungal types associated PM. Temperature significantly correlated with both PM10 (r=0.44), and PM2.5 (r=0.5). Significant negative correlations were found between O3 and PM2.5 (r=-0.47), and between SO2 with PM10 (r=-0.48). Wind speed positively correlated with airborne microorganisms associated PM. The regression model showed that the inverse PM2.5 concentration (1/PM2.5) was a significant determinant of fungal count associated PM. Chemical processes and environmental factors could affect properties of PM and in turn its biological quality., (Copyright © 2014 Elsevier B.V. All rights reserved.)