Green living environment protects against allergy, or does it?

The influence of pre- and postnatal exposure to air pollution and green spaces on infant's gut microbiota: Results from the MAMI birth cohort study

BACKGROUND

Animal and human studies indicate that exposure to air pollution and natural environments might modulate the gut microbiota, but epidemiological evidence is very scarce.

OBJECTIVES

To assess the potential impact of pre- and postnatal exposure to air pollution and green spaces on infant gut microbiota assembly and trajectories during the first year of life.

METHODS

MAMI ("MAternal MIcrobes") birth cohort (Valencia, Spain, N = 162) was used to study the impact of environmental exposure (acute and chronic) on infant gut microbiota during the first year of life (amplicon-based 16S rRNA sequencing). At 7 days and at 1, 6 and 12 months, residential pre- and postnatal exposure to air pollutants (NO2, black carbon -BC-, PM2.5 and O3) and green spaces indicators (NDVI and area of green spaces at 300, 500 and 1000 m buffers) were obtained. For the association between exposures and alpha diversity indicators linear regression models (cross-sectional analyses) and mixed models, including individual as a random effect (longitudinal analyses), were applied. For the differential taxon analysis, the ANCOM-BC package with a log count transformation and multiple-testing corrections were used.

RESULTS

Acute exposure in the first week of life and chronic postnatal exposure to NO2 were associated with a reduction in microbial alpha diversity, while the effects of green space exposure were not evident. Acute and chronic (prenatal or postnatal) exposure to NO2 resulted in increased abundance of Haemophilus, Akkermansia, Alistipes, Eggerthella, and Tyzerella populations, while increasing green space exposure associated with increased Negativicoccus, Senegalimassilia and Anaerococcus and decreased Tyzzerella and Lachnoclostridium populations.

DISCUSSION

We observed a decrease in the diversity of the gut microbiota and signs of alteration in its composition among infants exposed to higher levels of NO2. Increasing green space exposure was also associated with changes in gut microbial composition. Further research is needed to confirm these findings.

PM2.5 exceedances and source appointment as inputs for an early warning system

Between June 2018 and April 2019, a sampling campaign was carried out to collect PM2.5, monitoring meteorological parameters and anthropogenic events in the Sartenejas Valley, Venezuela. We develop a logistic model for PM2.5 exceedances (≥ 12.5 µg m-3). Source appointment was done using elemental composition and morphology of PM by scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). A proposal of an early warning system (EWS) for PM pollution episodes is presented. The logistic model has a holistic success rate of 94%, with forest fires and motor vehicle flows as significant variables. Source appointment analysis by occurrence of events showed that samples with higher concentrations of PM had carbon-rich particles and traces of K associated with biomass burning, as well as aluminosilicates and metallic elements associated with resuspension of soil dust by motor-vehicles. Quantitative source appointment analysis showed that soil dust, garbage burning/marine aerosols and wildfires are three majority sources of PM. An EWS for PM pollution episodes around the Sartenejas Valley is proposed considering the variables and elements mentioned.

Urban grey spaces are associated with increased allergy in the general population

BACKGROUND

the built environment in urban areas may have side effects on children's respiratory health, whilst less is known for adulthood.

AIM

to assess the association between increasing exposure to grey spaces and allergic status in an adult general population sample.

METHODS

2070 subjects (age range 15-84 yrs), living in Pisa/Cascina, Italy, were investigated in 1991-93 through a questionnaire on health status and risk factors, skin prick test (SPT), serum Immunoglobulins E (IgE), and serum antibodies to benzo(a)pyrene diol epoxide (BPDE)-DNA adducts. Land-cover exposure within a 1000 m buffer from each subject's home address was assessed through the CORINE Land Cover program (CLC 1990) within the FP7/HEALS project (2013-2018). Participants' residential addresses were geocoded and the proportion of surrounding grey spaces was calculated. Through logistic regression models, adjusting for potential confounding factors, the effect of a 10% increase in grey spaces exposure on allergic biomarkers/conditions was assessed; the relationship with serum antibodies to BPDE-DNA adducts positivity was also analyzed.

RESULTS

A 10% increase in grey spaces coverage was associated with a higher probability of having SPT positivity (OR 1.07, 95% CI 1.02-1.13), seasonal SPT positivity (OR 1.12, 1.05-1.19), polysensitization (OR 1.11, 1.04-1.19), allergic rhinitis (OR 1.10, 1.04-1.17), co-presence of SPT positivity and asthma/allergic rhinitis (OR 1.16, 1.08-1.25), asthma/allergic rhinitis (OR 1.06, 1.00-1.12), presence of serum antibodies to BPDE-DNA adducts positivity (OR 1.07, 1.01-1.14).

CONCLUSIONS

grey spaces have adverse effects on allergic status and are related to a biomarker of polycyclic aromatic hydrocarbons exposure in adulthood. Thus, they may be used as a proxy of urban environmental exposure.

Association between Land Use Mix and Respiratory Symptoms and Asthma in Children from the Generation XXI Birth Cohort

Land use mix (LUM) in the neighbourhoods has been associated with healthier lifestyles. However, less is known about the association between LUM and health outcomes, namely during childhood. The objective of this study was to evaluate the association between different LUM indexes for Porto Metropolitan Area and asthma and respiratory symptoms in children. A cross-sectional analysis was performed involving 6260 children enrolled in Generation XXI. Land use around the child's residence was assessed with the Portuguese official map of land cover using a GIS. Generalized linear mixed-effects models were fitted to estimate the association between LUM and respiratory symptoms and asthma at 7 years of age. Adjusted associations were quantified using odds ratio (OR) and 95% confidence interval (95% CI). After adjustment, LUM was associated with a lower odds of wheezing in the last 12 months [OR (95% CI) = 0.37 (0.15; 0.93) using Shannon's Evenness Index within 500 m; and OR = 0.93 (0.89; 0.98) using the number of different land use types within 250 m]. Living in neighbourhoods with high LUM has a protective effect on current wheezing symptoms. Our results highlight the association between LUM and respiratory symptoms among children, suggesting that public health considerations should be incorporated in land use decision-making.

Neighbourhood green and blue spaces and allergic sensitization in children: A longitudinal study based on repeated measures from the Generation XXI cohort

Evidence on the effect of natural environments on atopy in children is limited and inconsistent, disregarding the time-varying and cumulative exposures throughout the life course. To assess critical periods of exposure as well as the effect of longitudinal trajectories of exposure to green and blue spaces on the development of allergic sensitization in children at the age of 10 years. A longitudinal study was conducted involving 730 children enrolled in Generation XXI, a population-based birth cohort from the Porto Metropolitan Area (Portugal). Food and aeroallergens sensitization were evaluated at 10 years of age using Phadiatop Infant, Phadiatop fx1 and fx22 ImmunoCAP (Thermo Fisher Scientific, Uppsala, Sweden). Residential Normalized Difference Vegetation Index (NDVI) and distance to the nearest blue space (sea, river) were assessed using a Geographic Information System. Latent class linear mixed models were fitted to determine longitudinal trajectories of exposure. Associations were estimated using Cox proportional hazards regression models and expressed using hazard ratios (HR) and 95% confidence intervals (95% CI). Residing in neighbourhoods surrounded by more vegetation at 10 years, as well as lifetime exposure to a trajectory of higher levels of NDVI, were associated with a lower risk of allergic sensitization [HR (95% CI) = 0.095 (0.011, 0.823) and HR (95% CI) = 0.539 (0.301, 0.965), respectively]. Our findings support a role for both longitudinal, but particularly late-childhood, exposure to green spaces, in the prevention of allergic sensitization in children.

Heat waves and adaptation strategies in a mediterranean urban context

BACKGROUND

Heat waves can be considered as an emerging challenge among the potential health risks generated by urbanization and climate changes. Heat waves are becoming more frequent, long and intense, and can be defined as meteorological extreme events consisting in prolonged time of extremely high temperatures in a particular region. The following paper addresses health threats due to heat waves presenting the case study of Lecce, a city located in Southern Italy; the Mediterranean area is already recognized in international literature as a hot-spot for climate changes. This work assesses the potential impact of two different adaptation strategies.

METHODS

We have tested the effectiveness of cool surfaces and urban forestry as adaptation approaches to cope with heat waves. The microclimate computer-based model "ENVI-met" was adopted to predict thermal scenarios arising from the two proposed interventions. The parameters analysed consisted in temperature and relative humidity.

RESULTS

Urban forestry approach seem to lower temperature (that represents the major cause of urban overheating) better than cool surfaces strategy, but relative humidity produced by the evapotranspiration processes of urban forestry has also negative influences on temperature perceived by pedestrians (thermal discomfort).

CONCLUSION

Vegetation represents both an adaptation and a mitigation strategy to climate changes that guarantees an improvement of air quality, with consequent psychological and physical benefits. Wide campaigns aimed at planting trees and increasing the urban green coverage should be systematically planned and fostered by national, regional and local institutions preferably with the involvement of research departments, schools and citizens' associations.

Immune-microbiota interaction in Finnish and Russian Karelia young people with high and low allergy prevalence

Background

After the Second World War, the population living in the Karelian region was strictly divided by the “iron curtain” between Finland and Russia. This resulted in different lifestyle, standard of living, and exposure to the environment. Allergic manifestations and sensitization to common allergens have been much more common on the Finnish compared to the Russian side.

Objective

The remarkable allergy disparity in the Finnish and Russian Karelia calls for immunological explanations.

Methods

Young people, aged 15‐20 years, in the Finnish (n = 69) and Russian (n = 75) Karelia were studied. The impact of genetic variation on the phenotype was studied by a genome‐wide association analysis. Differences in gene expression (transcriptome) were explored from the blood mononuclear cells (PBMC) and related to skin and nasal epithelium microbiota and sensitization.

Results

The genotype differences between the Finnish and Russian populations did not explain the allergy gap. The network of gene expression and skin and nasal microbiota was richer and more diverse in the Russian subjects. When the function of 261 differentially expressed genes was explored, innate immunity pathways were suppressed among Russians compared to Finns. Differences in the gene expression paralleled the microbiota disparity. High Acinetobacter abundance in Russians correlated with suppression of innate immune response. High‐total IgE was associated with enhanced anti‐viral response in the Finnish but not in the Russian subjects.

Conclusions and clinical relevance

Young populations living in the Finnish and Russian Karelia show marked differences in genome‐wide gene expression and host contrasting skin and nasal epithelium microbiota. The rich gene‐microbe network in Russians seems to result in a better‐balanced innate immunity and associates with low allergy prevalence.

Analytical approaches to testing pathways linking greenspace to health: A scoping review of the empirical literature

BACKGROUND

Inadequate translation from theoretical to statistical models of the greenspace - health relationship may lead to incorrect conclusions about the importance of some pathways, which in turn may reduce the effectiveness of public health interventions involving urban greening. In this scoping review we aimed to: (1) summarize the general characteristics of approaches to intervening variable inference (mediation analysis) employed in epidemiological research in the field; (2) identify potential threats to the validity of findings; and (3) propose recommendations for planning, conducting, and reporting mediation analyses.

METHODS

We conducted a scoping review, searching PubMed, Scopus, and Web of Science for peer-reviewed epidemiological studies published by December 31, 2019. The list of potential studies was continuously updated through other sources until March 2020. Narrative presentation of the results was coupled with descriptive summary of study characteristics.

RESULTS

We found 106 studies, most of which were cross-sectional in design. Most studies only had a spatial measure of greenspace. Mental health/well-being was the most commonly studied outcome, and physical activity and air pollution were the most commonly tested intervening variables. Most studies only conducted single mediation analysis, even when multiple potentially intertwined mediators were measured. The analytical approaches used were causal steps, difference-of-coefficients, product-of-coefficients, counterfactual framework, and structural equation modelling (SEM). Bootstrapping was the most commonly used method to construct the 95% CI of the indirect effect. The product-of-coefficients method and SEM as used to investigate serial mediation components were more likely to yield findings of indirect effect. In some cases, the causal steps approach thwarted tests of indirect effect, even though both links in an indirect effect were supported. In most studies, sensitivity analyses and proper methodological discussion of the modelling approach were missing.

CONCLUSIONS

We found a persistent pattern of suboptimal conduct and reporting of mediation analysis in epidemiological studies investigating pathways linking greenspace to health; however, recent years have seen improvements in these respects. Better planning, conduct, and reporting of mediation analyses are warranted.

Influence of residential land cover on childhood allergic and respiratory symptoms and diseases: Evidence from 9 European cohorts

INTRODUCTION

Recent research focused on the interaction between land cover and the development of allergic and respiratory disease has provided conflicting results and the underlying mechanisms are not fully understood. In particular, green space, which confers an overall positive impact on general health, may be significantly contributing to adverse respiratory health outcomes. This study evaluates associations between surrounding residential land cover (green, grey, agricultural and blue space), including type of forest cover (deciduous, coniferous and mixed), and childhood allergic and respiratory diseases.

METHODS

Data from 8063 children, aged 3-14 years, were obtained from nine European population-based studies participating in the HEALS project. Land-cover exposures within a 500 m buffer centred on each child's residential address were computed using data from the Coordination of Information on the Environment (CORINE) program. The associations of allergic and respiratory symptoms (wheeze, asthma, allergic rhinitis and eczema) with land coverage were estimated for each study using logistic regression models, adjusted for sex, age, body mass index, maternal education, parental smoking, and parental history of allergy. Finally, the pooled effects across studies were estimated using meta-analyses.

RESULTS

In the pooled analyses, a 10% increase in green space coverage was significantly associated with a 5.9%-13.0% increase in the odds of wheezing, asthma, and allergic rhinitis, but not eczema. A trend of an inverse relationship between agricultural space and respiratory symptoms was observed, but did not reach statistical significance. In secondary analyses, children living in areas with surrounding coniferous forests had significantly greater odds of reporting wheezing, asthma and allergic rhinitis.

CONCLUSION

Our results provide further evidence that exposure to green space is associated with increased respiratory disease in children. Additionally, our findings suggest that coniferous forests might be associated with wheezing, asthma and allergic rhinitis. Additional studies evaluating both the type of green space and its use in relation to respiratory conditions should be conducted in order to clarify the underlying mechanisms behind associated adverse impacts.

A biodiversity hypothesis

Biodiversity hypothesis states that contact with natural environments enriches the human microbiome, promotes immune balance and protects from allergy and inflammatory disorders. We are protected by two nested layers of biodiversity, microbiota of the outer layer (soil, natural waters, plants, animals) and inner layer (gut, skin, airways). The latter inhabits our body and is colonized from the outer layer. Explosion of human populations along with cultural evolution is profoundly changing our environment and lifestyle. Adaptive immunoregulatory circuits and dynamic homeostasis are at stake in the newly emerged urban surroundings. In allergy, and chronic inflammatory disorders in general, exploring the determinants of immunotolerance is the key for prevention and more effective treatment. Loss of immunoprotective factors, derived from nature, is a new kind of health risk poorly acknowledged until recently. The paradigm change has been implemented in the Finnish allergy programme (2008-2018), which emphasized tolerance instead of avoidance. The first results are promising, as allergy burden has started to reduce. The rapidly urbanizing world is facing serious biodiversity loss with global warming, which are interconnected. Biodiversity hypothesis of health and disease has societal impact, for example, on city planning, food and energy production and nature conservation. It has also a message for individuals for health and well-being: take nature close, to touch, eat, breathe, experience and enjoy. Biodiverse natural environments are dependent on planetary health, which should be a priority also among health professionals.

Biodiversity and human health: mechanisms and evidence of the positive health effects of diversity in nature and green spaces

INTRODUCTION

Natural environments and green spaces provide ecosystem services that enhance human health and well-being. They improve mental health, mitigate allergies and reduce all-cause, respiratory, cardiovascular and cancer mortality. The presence, accessibility, proximity and greenness of green spaces determine the magnitude of their positive health effects, but the role of biodiversity (including species and ecosystem diversity) within green spaces remains underexplored. This review describes mechanisms and evidence of effects of biodiversity in nature and green spaces on human health.

SOURCES OF DATA

We identified studies listed in PubMed and Web of Science using combinations of keywords including 'biodiversity', 'diversity', 'species richness', 'human health', 'mental health' and 'well-being' with no restrictions on the year of publication. Papers were considered for detailed evaluation if they were written in English and reported data on levels of biodiversity and health outcomes.

AREAS OF AGREEMENT

There is evidence for positive associations between species diversity and well-being (psychological and physical) and between ecosystem diversity and immune system regulation.

AREAS OF CONCERN

There is a very limited number of studies that relate measured biodiversity to human health. There is more evidence for self-reported psychological well-being than for well-defined clinical outcomes. High species diversity has been associated with both reduced and increased vector-borne disease risk.

GROWING POINTS

Biodiversity supports ecosystem services mitigating heat, noise and air pollution, which all mediate the positive health effects of green spaces, but direct and long-term health outcomes of species diversity have been insufficiently studied so far.

AREAS TIMELY FOR RESEARCH

Additional research and newly developed methods are needed to quantify short- and long-term health effects of exposure to perceived and objectively measured species diversity, including health effects of nature-based solutions and exposure to microbiota.

Do Income, Race and Ethnicity, and Sprawl Influence the Greenspace-Human Health Link in City-Level Analyses? Findings from 496 Cities in the United States

Examination of the greenspace—human health relationship operates in at least four dimensions: what is considered greenspace? which moderators and mediators are included? what outcomes are measured? and which units of analysis (e.g., individuals, cities) are studied? We examined three of these four dimensions in a cross-sectional study of 496 of the 500 most populated US cities (total population size = 97,574,613, average population per city = 197,920). Spatial average models tested the effect of two greenspace measures (Normalized Difference Vegetation Index greenness and tree cover) on two outcomes (obesity and mental health), while adjusting for income, race and ethnicity, sprawl, age, sex, physical inactivity, median age of housing, and total population. We conducted analyses at the city scale, which is an understudied unit of analysis, and compared findings to individual- and neighborhood-level studies. In two of four models, greenspace was associated with better health. We found race and ethnicity moderated this relationship with varying results. In full sample analyses, cities with greater percentages of non-Hispanic Whites showed links between higher tree cover and lower obesity but marginal relationships between higher greenness and lower obesity. In subsample analyses with majority-non-Hispanic Black cities, higher tree cover was associated with lower obesity and better mental health. These findings advance previous research by showing that race and ethnicity moderate the greenspace—health link at the city level.

Skin microbiota and allergic symptoms associate with exposure to environmental microbes

A rural environment and farming lifestyle are known to provide protection against allergic diseases. This protective effect is expected to be mediated via exposure to environmental microbes that are needed to support a normal immune tolerance. However, the triangle of interactions between environmental microbes, host microbiota, and immune system remains poorly understood. Here, we have studied these interactions using a canine model (two breeds, n = 169), providing an intermediate approach between complex human studies and artificial mouse model studies. We show that the skin microbiota reflects both the living environment and the lifestyle of a dog. Remarkably, the prevalence of spontaneous allergies is also associated with residential environment and lifestyle, such that allergies are most common among urban dogs living in single-person families without other animal contacts, and least common among rural dogs having opposite lifestyle features. Thus, we show that living environment and lifestyle concurrently associate with skin microbiota and allergies, suggesting that these factors might be causally related. Moreover, microbes commonly found on human skin tend to dominate the urban canine skin microbiota, while environmental microbes are rich in the rural canine skin microbiota. This in turn suggests that skin microbiota is a feasible indicator of exposure to environmental microbes. As short-term exposure to environmental microbes via exercise is not associated with allergies, we conclude that prominent and sustained exposure to environmental microbiotas should be promoted by urban planning and lifestyle changes to support health of urban populations.

Association of neighborhood greenness with self-perceived stress, depression and anxiety symptoms in older U.S adults

BACKGROUND

Neighborhood environment, such as green vegetation, has been shown to play a role in coping with stress and mental ill health. Yet, epidemiological evidence of the association between greenness and mental health is inconsistent.

METHODS

We examined whether living in green space is associated with self-perceived stress, depressive and anxiety symptoms in a nationally representative, longitudinal sample of community-dwelling older adults (N = 4118; aged 57-85 years) in the United States. We evaluated perceived stress, depression and anxiety symptoms using the Cohen's Perceived Stress Scale, the Center for Epidemiological Studies - Depression, and the Hospital Anxiety and Depression Scale - anxiety subscale, respectively. Greenness was assessed for each participant using the Normalized Difference Vegetation Index at 250-m resolution, as well as a buffer of 1000-m. We conducted longitudinal analyses to assess the associations between greenness and mental health upon adjusting for confounders (e.g., education), and to examine potential mediation and effect modification.

RESULTS

An interquartile range (0.25 point) increase in contemporaneous greenness was significantly associated with 0.238 unit (95% CI: - 0.346, - 0.130) and 0.162 unit (95% CI: - 0.271, - 0.054) decrease in the perceived stress in base and multivariable models, respectively. The magnitude of the association was similar or even stronger when examining summer (- 0.161; 95% CI: - 0.295, - 0.027) and annual average of greenness (- 0.188; 95% CI: - 0.337, - 0.038), as well as greenness buffer of 1000-m. The greenness-stress association was partially mediated by physical activity (15.1% mediated), where increased greenness led to increased physical activity and less stress, and by history of respiratory diseases (- 3.8% mediated), where increased greenness led to increased respiratory disease and more stress. The association was also significantly modified by race, social support, physical function, socioeconomic status, and region. While greenness was not significantly associated with anxiety and depressive scores across all participants, significant inverse associations were found for Whites participants, and for individuals with higher socioeconomic status, who were physically active, as compared to their counterparts.

CONCLUSION

We found a direct association of greenness with perceived stress among older adults, and an indirect association mediated through physical activity and respiratory disease history. Our study findings warrant further examination of the mediation and modification of the greenness-mental health association.

Is the "farm effect" hypothesis still current? Atopy and allergic diseases in rural and urban children in Poland

OBJECTIVE

The prevalence of allergic diseases has reached epidemic proportions in the Western world. Although farm-living has been associated with a lower prevalence of asthma and atopy, a marked increase in atopy among rural populations after accession to the European Union has been recently reported in Poland. Here, we aimed to investigate the effect of living environment on the prevalence of atopy and allergic diseases in Polish children.

METHODS

400 schoolchildren aged 10-14 years from the capital city (223) and from traditional rural part of the country (177) were recruited from June to November 2011. Data on allergic diseases and symptoms were collected by means of questionnaire and physical examination. Atopy was assessed based on skin prick tests (SPTs) reactivity to inhalant allergens in 350 children.

RESULTS

A high discrepancy between the prevalence of allergic symptoms (46.7%) and doctor-diagnosed allergic diseases (25%) was demonstrated (p < 0.0001). Urban children had a higher overall prevalence of allergic diseases and atopy than children living in rural areas, 29.3% versus 17.1% (p = 0.007) and 33.5% versus 20% (p = 0.0045), respectively. However, no significant differences in the rates of particular allergic diseases were noted (p > 0.05). There was higher SPT positivity to trees, grass, corn, weeds, animal dander, and molds in urban children (p < 0.05).

CONCLUSIONS

Our data support the protective effect of farm-living on the prevalence of atopy and overall allergic diseases, albeit not on particular allergic diseases, in children in Poland. The underlying mechanisms are not identified, but current socioeconomic changes may be responsible.