Environmental heterogeneity in human health studies. A compositional methodology for Land Use and Land cover data

The use of Land use and Land cover (LULC) data is gradually becoming more widely spread in studies relating the environment to human health. However, little research has acknowledged the compositional nature of these data. The goal of the present study is to explore, for the first time, the independent effect of eight LULC categories (agricultural land, bare land, coniferous forest, broad-leaved forest, sclerophyll forest, grassland and shrubs, urban areas, and waterbodies) on three selected common health conditions: type 2 diabetes mellitus (T2DM), asthma and anxiety, using a compositional methodological approach and leveraging observational health data of Catalonia (Spain) at area level. We fixed the risk exposure scenario using three covariates (socioeconomic status, age group, and sex). Then, we assessed the independent effect of the eight LULC categories on each health condition. Our results show that each LULC category has a distinctive effect on the three health conditions and that the three covariates clearly modify this effect. This compositional approach has yielded plausible results supported by the existing literature, highlighting the relevance of environmental heterogeneity in health studies. In this sense, we argue that different types of environment possess exclusive biotic and abiotic elements affecting distinctively on human health. We believe our contribution might help researchers approach the environment in a more multidimensional manner integrating environmental heterogeneity in the analysis.

Human absorption of monoterpenes after a 2-h forest exposure: A field experiment in a Mediterranean holm oak forest

The current body of literature points monoterpenes as one of the determinant factors of the interaction between forests and human health. The present study aims at analyzing the monoterpene absorption by humans during a 2 -hs forest exposure in a Mediterranean holm oak forest focusing on the four most abundant monoterpene compounds: alpha-pinene, beta-pinene, alpha-phellandrene and limonene. Participants' blood samples were collected before and after exposure to forest or urban environment (control). We conducted air and blood sampling using cartridges and head space method and determined the monoterpene compounds through CGMS. We identified the four compounds in forest air during the experimental study being alpha-pinene the monoterpene with the greatest concentration. Results show no significant changes in monoterpene blood concentrations for the forest and control group. However, a negative significant relationship between absorption and baseline blood concentration of the most abundant forest air monoterpenes, alpha-pinene and beta-pinene, was found in individuals visiting the forest, i.e. higher absorption was found the lower the baseline blood concentration was. Although no significant lineal correlation could be spotted between the vital variables and the monoterpene absorption, we found significant correlations between the absorption of the monoterpene compounds. This attempt, first in a Mediterranean holm oak forest, can serve as a starting point and constitute a valuable contribution for further research in regard to experimental design and laboratory analysis.

Reviewing the reliability of Land Use and Land Cover data in studies relating human health to the environment

BACKGROUND

In recent years, research has been increasingly devoted to understanding the complex human health-environment relationship. Nevertheless, many different measurements have been applied to characterize the environment. Among them, the application of Land Use and Land Cover (LULC) data is becoming more noticeable over time.

AIMS

This research aims to analyse the reliability of Land Use and Land Cover data (LULC) data as a suitable describer of the environment in studies relating human health to the environment. With a specific focus on the methodologies using LULC data, we also examine the study designs and analytical methods that have been commonly performed so far.

MATERIALS AND METHODS

We gathered studies relating human health outcomes to Land Use and Land Cover (LULC) data. A Boolean search limited to reviews was conducted in February 2019 using Web of Science Core Collection search engines. Five reviews were selected as our preliminary starting set of literature and from those, two backward snowballing searches were conducted. The first backward snowballing search used the reference lists of the first 5 reviews and revealed 17 articles. From these, the second search gathered 24 new articles also fulfilling the inclusion criteria established. In total, 41 articles were examined.

RESULTS

Our main results reported that Land Use and Land Cover (LULC) data national level data was preferred over LULC international level data. However, this tendency seems to be strongly related to the specific aims of the articles. They essentially defined the living environment either through buffer zones, using the administrative boundaries wherein the individuals reside, or using the specific location of the individuals assessed. As for the characterization of the environment, authors performed 4 principal methodologies: extracting the percentage of green space, computing the "Land Use mix", recording the type of land cover, and using the percentage of tree canopy. Besides, all the articles included measurements in urban contexts and most of them evaluated the accessibility of individuals to their surroundings. Furthermore, it was clearly stated that the complexity of the topic and the challenging data leads authors to carry out advanced statistical methods and mostly cross-sectional designs with no causal relations.

DISCUSSION AND CONCLUSIONS

Land Use and Land Cover (LULC) data has been demonstrated to be a versatile tool supporting both local-focused studies with few individuals involved and broad territorial-scoped studies with huge populations. Promising synergy has been highlighted between Electronic Health Records (EHR) and LULC data in studies dealing with massive information and broader scopes with regards to the assessment of territorial realities. As this emerging topic matures, investigators should (1) elucidate subjects of ongoing debate such as the measurement of the living environment and its characterization; (2) explore the whole potential of LULC data, using methodologies that encompass both their biophysical and socioeconomic information; (3) perform innovative designs that are able to establish causal relationships among the studied variables (for example, Cellular Automata models), and (4) expand the current set of studied health outcomes leveraging comprehensive and trustworthy health data sources such as EHR.