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To better understand the impact of molds on indoor air quality, we studied the photochemistry of microbial films made by Aspergillus niger species, a common indoor mold. Specifically, we investigated their implication in the conversion of adsorbed nitrate anions into gaseous nitrous acid (HONO) and nitrogen oxides (NO x ), as well as the related VOC emissions under different indoor conditions, using a high-resolution proton transfer reaction-time of flight-mass spectrometer (PTR-TOF-MS) and a long path absorption photometer (LOPAP). The different mold preparations were characterized by the means of direct injection into an Orbitrap high-resolution mass spectrometer with a heated electrospray ionization (ESI-Orbitrap-MS). The formation of a wide range of VOCs, having emission profiles sensitive to the types of films (either doped by potassium nitrate or not), cultivation time, UV-light irradiation, potassium nitrate concentration and relative humidity was observed. The formation of nitrous acid from these films was also determined and found to be dependent on light and relative humidity. Finally, the reaction paths for the NO x and HONO production are proposed. This work helps to better understand the implication of microbial surfaces as a new indoor source for HONO emission., (© 2021 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

People spend 80% of their time indoors exposed to poor air quality due to mold growth in humid air as well as human activities (painting, cooking, cleaning, smoking…). To better understand the impact of molds on indoor air quality, we studied the emission of microbial Volatile Organic Compounds (mVOCs) from Aspergillus niger, cultivated on malt agar extract, using a high-resolution proton transfer reaction- time of flight- mass spectrometer (PTR-TOF-MS). These emissions were studied for different cultivation time and indoor relative humidities. Our results show that the concentration of the known C 4 -C 9 mVOCs tracers of the microbial activity (like 1-octen-3-ol, 3-methylfuran, 2-pentanone, dimethyl sulfide, dimethyl disulfide, nitromethane, 1,3-octadiene…) was the highest in the early stage of growth. However, these emissions decreased substantially after a cultivation time of 10-14 days and were highly affected by the relative humidity. In addition, the emissions of certain mVOCs were sensitive to indoor light, suggesting an impact of photochemistry on the relative amounts of indoor mVOCs. Based on this study, an estimation of the mVOC concentration for a standard living room was established at different air exchange rates and their indoor lifetimes toward hydroxyl radicals and ozone were also estimated. These findings give insights on possible mVOCs levels in moisture-damaged buildings for an early detection of microbial activity and new evidences about the effect of indoor light on their emission., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Microorganisms in soil are known to be a source and a sink of volatile organic compounds (VOCs). The role of the microbial VOCs on soil ecosystem regulation has been increasingly demonstrated in the recent years. Nevertheless, little is known about the influence of the microbial soil community structure and diversity on VOC emissions. This novel study analyzed the effect of reduced microbial diversity in soil on VOC emissions. We found that reduced levels of microbial diversity in soil increased VOC emissions from soils, while the number of different VOCs emitted decreased. Furthermore, we found that Proteobacteria, Bacteroidetes and fungi phyla were positively correlated to VOC emissions, and other prokaryotic phyla were either negatively correlated or very slightly positively correlated to VOCs emissions. Our interpretation is that Proteobacteria, Bacteroidetes and fungi were VOC producers while the other prokaryotic phyla were consumers. Finally, we discussed the possible role of VOCs as mediators of microbial interactions in soil.

Volatile Organic Compounds (VOCs) are reactive compounds essential to atmospheric chemistry. They are mainly emitted by living organisms, and mostly by plants. Soil microbes also contribute to emissions of VOCs. However, these emissions have not yet been characterised in terms of quality and quantity. Furthermore, long-term organic matter amendments are known to affect the microbial content of soils, and hence the quantity and quality of VOC emissions. This study investigates which and how much of these VOCs are emitted from soil amended with organic waste products (OWPs). Four OWPs were investigated: municipal solid waste compost (MSW), green waste and sludge co-compost (GWS), bio-waste compost (BIOW) and farmyard manure (FYM). These OWPs have been amended every two years since 1998 until now at a rate of ~4 tC ha -1 . A soil receiving no organic inputs was used as a reference (CN). VOCs emissions were measured under laboratory conditions using a Proton Transfer Reaction-Quadrupole ion guide Time of Flight-Mass Spectrometry (PTR-QiToF-MS). A laboratory system was set up made of two Pyrex chambers, one for samples and the second empty, to be used as a blank. Our results showed that total VOC emissions were higher in BIOW than in MSW. Further findings outlined that the most emitted compounds were acetone, butanone and acetaldehyde in all treatments, suggesting a common production mechanism for these compounds, meaning they were not affected by the OWP amendment. We isolated 21 VOCs that had statistically different emissions between the treatments and could therefore be considered as good markers of soil biological functioning. Our results suggest that organic matter and pH jointly influenced total VOC emissions. In conclusion, OWPs in soil affect the type of VOC emissions and the total flux also depends on the pH of the soil and the quantity of organic matter., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background and Objectives: Migration flux is an increasing phenomenon in Italy, and it raises several public health issues and concerns in pediatric infectious diseases. This study investigated the clinical characteristics and outcomes of a pediatric population at high-risk for tuberculosis (TB) and the potential role of immigration as a risk factor., Design: We performed an observational retrospective study of children referred to the only Pediatric Infectious Diseases Unit for Northern Sardinia over a 6-year-period (2009-2014). Main variables assessed included TB skin test (TST), confirmed by quantiFERON Gold in Tube test, thorax X-ray (TX), microbiological culture, direct microscopy for acid-fast bacilli and molecular assays., Results: Of the 246 children (mean age = 5.8 ± 3.9 years) identified, 222 (90.2%) were native to Sardinia and 24 (9.8%) were immigrants. The majority of children (n=205; 83%) were TB-exposed but not infected based on a negative TST and TX. Among the TST positive group (n= 39; 16%), 19 (49%) had latent TB (TX negative), while 20 (51%) had active TB (TX positive). The percent of TST positive children was significantly higher in the immigrant than the native group (42.5% versus 14%, p<0.001). Clinical presentations included pulmonary involvement with hilar lymphadenopathy (72%), pleurisy (13,5%), lateral-cervical lymphadenopathy (9%), pneumonia with calcifications (4.5%) and disseminated TB (4.5%). One child had multidrug-resistant tuberculosis., Conclusions: Pediatric TB represents a relevant and potentially worsening public health problem in Northern Sardinia. A strict surveillance system and appropriate treatment can prevent the most severe forms and reduce TB transmission., Competing Interests: Competing interests: The authors have declared that no competing interests exist.