Fungal and Bacterial Communities in Indoor Dust Follow Different Environmental Determinants

Urban green and grey space in relation to respiratory health in children

We assessed the effect of three different indices of urban built environment on allergic and respiratory conditions.This study involved 2472 children participating in the ongoing INMA birth cohort located in two bio-geographic regions (Euro-Siberian and Mediterranean) in Spain. Residential surrounding built environment was characterised as 1) residential surrounding greenness based on satellite-derived normalised difference vegetation index (NDVI), 2) residential proximity to green spaces and 3) residential surrounding greyness based on urban land use patterns. Information on wheezing, bronchitis, asthma and allergic rhinitis up to age 4 years was obtained from parent-completed questionnaires. Logistic regression and generalised estimating equation modelling were performed.Among children from the Euro-Siberian region, higher residential surrounding greenness and higher proximity to green spaces were negatively associated with wheezing. In the Mediterranean region, higher residential proximity to green spaces was associated with a reduced risk for bronchitis. A higher amount of residential surrounding greyness was found to increase the risk for bronchitis in this region.Associations between indices of urban residential greenness and greyness with respiratory diseases differ by region. The pathways underlying these associations require further exploration.

High temporal variability in airborne bacterial diversity and abundance inside single-family residences

Our homes are microbial habitats, and although the amounts and types of bacteria in indoor air have been shown to vary substantially across residences, temporal variability within homes has rarely been characterized. Here, we sought to quantify the temporal variability in the amounts and types of airborne bacteria in homes, and what factors drive this variability. We collected filter samples of indoor and outdoor air in 15 homes over 1 year (approximately eight time points per home, two per season), and we used culture-independent DNA sequencing approaches to characterize bacterial community composition. Significant differences in indoor air community composition were observed both between homes and within each home over time. Indoor and outdoor air community compositions were not significantly correlated, suggesting that indoor and outdoor air communities are decoupled. Indoor air communities from the same home were often just as different at adjacent time points as they were across larger temporal distances, and temporal variation correlated with changes in environmental conditions, including temperature and relative humidity. Although all homes had highly variable indoor air communities, homes with the most temporally variable communities had more stable, lower average microbial loads than homes with less variable communities.

The role of outdoor fungi on asthma hospital admissions in children and adolescents: A 5-year time stratified case-crossover analysis

BACKGROUND

Some fungal spores can trigger asthma exacerbation but knowledge of which outdoor fungal spores contribute to asthma hospitalisation is limited.

OBJECTIVES

To examine the role of outdoor fungal spores in child and adolescent asthma hospitalisations.

METHODS

We conducted a bi-directional time-stratified case-crossover study of child and adolescent asthma hospitalisations over 5 years. Conditional logistic regression assessed the role of 20 fungi taxa (Same day [L0] and lagged [L1-3]) adjusted for maximum temperature, humidity and grass pollen. Strata specific effects were explored if there was evidence of effect modification by age, sex, air pollutants or grass pollen. Non-linear effects examined with Generalized Additive Models.

RESULTS

Of 2098 children hospitalised for asthma, 60% were boys; mean age was 5.5±3.7 years. Fungal spore counts peaked during warm months. Regression models found weak associations with Coprinus [L0,L1: OR=1.03, 1.01-1.06], Periconia [L0: OR=1.03, 1.001-1.07] and Chaetomium [L2: OR=1.08, 1.0-1.2]. Sex appeared to act as an effect modifier with girls having stronger associations with Cladosporium, Coprinus and total fungi. Older adolescent (14-18 years) hospitalisation was significantly associated with Coprinus and Ustilago/smuts. Air pollutants and grass pollen did not appear to act as effect modifiers. Non-linearity was not detected.

CONCLUSION

There may be associations between some outdoor fungal spores and asthma hospitalisations. Further research needed to explore whether these findings can be replicated; and examine whether fungal sensitisation and/or human rhinovirus infections are associated with stronger effects. If findings are replicated, then the need to develop predictive models for fungal spore distribution and levels may become more important.

Concentrations and identification of culturable airborne fungi in underground stations of the Seoul metro

The purpose of this study was to measure the culturable airborne fungi (CAF) concentrations in the underground subway stations of Seoul, Korea at two time points. This study measured the CAF concentrations in enclosed environments at 16 underground stations of the Seoul Metro in 2006 and 2013 and investigated the effects of various environmental factors, including the presence of platform screen doors, temperature, relative humidity, and number of passengers. CAF concentrations at the stations in 2006 were significantly higher than that at the same stations in 2013 (p < 0.001). Furthermore, there was a significant correlation between CAF concentration and relative humidity (r = 0.311, p < 0.05). Geotrichum and Penicillium were the predominant genera. The CAF concentrations in stations with an operating supply air were significantly higher than that in stations with no supply air (p < 0.001). Therefore, it is recommended that special attention be given to stations with clean supplied air to improve the indoor air quality of these subway stations.

What Have We Learned about the Microbiomes of Indoor Environments?

The advent and application of high-throughput molecular techniques for analyzing microbial communities in the indoor environment have led to illuminating findings and are beginning to change the way we think about human health in relation to the built environment. Here I review recent studies on the microbiology of the built environment, organize their findings into 12 major thematic categories, and comment on how these studies have or have not advanced knowledge in each area beyond what we already knew from over 100 years of applying culture-based methods to building samples.

The advent and application of high-throughput molecular techniques for analyzing microbial communities in the indoor environment have led to illuminating findings and are beginning to change the way we think about human health in relation to the built environment. Here I review recent studies on the microbiology of the built environment, organize their findings into 12 major thematic categories, and comment on how these studies have or have not advanced knowledge in each area beyond what we already knew from over 100 years of applying culture-based methods to building samples. I propose that while we have added tremendous complexity to the rich existing knowledge base, the practical implications of this added complexity remain somewhat elusive. It remains to be seen how this new knowledge base will change how we design, build, and operate buildings. Much more research is needed to better understand the complexity with which indoor microbiomes may affect human health in both positive and negative ways.

What Have We Learned about the Microbiomes of Indoor Environments?

The advent and application of high-throughput molecular techniques for analyzing microbial communities in the indoor environment have led to illuminating findings and are beginning to change the way we think about human health in relation to the built environment. Here I review recent studies on the microbiology of the built environment, organize their findings into 12 major thematic categories, and comment on how these studies have or have not advanced knowledge in each area beyond what we already knew from over 100 years of applying culture-based methods to building samples. I propose that while we have added tremendous complexity to the rich existing knowledge base, the practical implications of this added complexity remain somewhat elusive. It remains to be seen how this new knowledge base will change how we design, build, and operate buildings. Much more research is needed to better understand the complexity with which indoor microbiomes may affect human health in both positive and negative ways.