Exploring the exposome: study measures multitude of environmental influences on health
Scientists have measured how children and pregnant women are exposed to over 120 environmental factors influencing our health — from air and noise pollution to green space and access to public transport.
The study gathered and analysed data from six European countries to build a picture of the ‘exposome’ — the array of environmental factors that humans are exposed to from the moment they are conceived.
A better understanding of the exposome could help us understand the role of the environment in the onset of various diseases, including cancer and other chronic disorders such as cardiovascular disease. Reference.
- The early-life exposome is high dimensional and not easily reducible to fewer components.
- Correlations between exposures within the same exposure group can be high.
- Correlations between exposures in different exposure groups are low.
- The exposome varies strongly by location and by life period.
Characterization of the “exposome”, the set of all environmental factors that one is exposed to from conception onwards, has been advocated to better understand the role of environmental factors on chronic diseases.
Here, we aimed to describe the early-life exposome. Specifically, we focused on the correlations between multiple environmental exposures, their patterns and their variability across European regions and across time (pregnancy and childhood periods). We relied on the Human Early-Life Exposome (HELIX) project, in which 87 environmental exposures during pregnancy and 122 during the childhood period (grouped in 19 exposure groups) were assessed in 1301 pregnant mothers and their children at 6–11 years in 6 European birth cohorts.
Some correlations between exposures in the same exposure group reached high values above 0.8. The median correlation within exposure groups was >0.3 for many exposure groups, reaching 0.69 for water disinfection by products in pregnancy and 0.67 for the meteorological group in childhood. Median correlations between different exposure groups rarely reached 0.3. Some correlations were driven by cohort-level associations (e.g. air pollution and chemicals). Ten principal components explained 45% and 39% of the total variance in the pregnancy and childhood exposome, respectively, while 65 and 90 components were required to explain 95% of the exposome variability. Correlations between maternal (pregnancy) and childhood exposures were high (>0.6) for most exposures modeled at the residential address (e.g. air pollution), but were much lower and even close to zero for some chemical exposures.
In conclusion, the early life exposome was high dimensional, meaning that it cannot easily be measured by or reduced to fewer components. Correlations between exposures from different exposure groups were much lower than within exposure groups, which have important implications for co-exposure confounding in multiple exposure studies. Also, we observed the early life exposome to be variable over time and to vary by cohort, so measurements at one time point or one place will not capture its complexities.
Dynamic Human Environmental Exposome Revealed by Longitudinal Personal Monitoring
Stanford scientists have measured the human “exposome,” or the particulates, chemicals and microbes that individually swaddle us all, in unprecedented detail
2018 Study Highlights
- Human exposome, including biotic/abiotic exposures, is vast, diverse, and dynamic
- Human exposome is influenced by environmental and spatial/lifestyle variables
- People can have distinct personalized exposomes, even when geographically close
- Human- and environment-related exposures constitute the human exposome cloud
2018 Paper Abstract
Human health is dependent upon environmental exposures, yet the diversity and variation in exposures are poorly understood.
We developed a sensitive method to monitor personal airborne biological and chemical exposures and followed the personal exposomes of 15 individuals for up to 890 days and over 66 distinct geographical locations.
We found that individuals are potentially exposed to thousands of pan-domain species and chemical compounds, including insecticides and carcinogens. Personal biological and chemical exposomes are highly dynamic and vary spatiotemporally, even for individuals located in the same general geographical region. Integrated analysis of biological and chemical exposomes revealed strong location-dependent relationships. Finally, construction of an exposome interaction network demonstrated the presence of distinct yet interconnected human- and environment-centric clouds, comprised of interacting ecosystems such as human, flora, pets, and arthropods.
Overall, we demonstrate that human exposomes are diverse, dynamic, spatiotemporally-driven interaction networks with the potential to impact human health..
- We are bombarded by thousands of diverse species and chemicals, ncbi, stanford.edu.
- Dynamic Human Environmental Exposome Revealed by Longitudinal Personal Monitoring, cell.
- Featured image literatumonline.
Development of exposome correlation globes to map out environment-wide associations
Success in mapping the human genome has fostered the complementary concept of the “exposome“.
The exposome can be defined as the measure of all the exposures of an individual in a lifetime and how those exposures relate to health. An individual’s exposure begins before birth and includes insults from environmental and occupational sources. Understanding how exposures from our environment, diet, lifestyle, etc. interact with our own unique characteristics such as genetics, physiology, and epigenetics impact our health is how the exposome will be articulated.
Exposomics is the study of the exposome and relies on the application of internal and external exposure assessment methods.
2016 Paper Abstract
The exposome concept was defined in 2005 as encompassing all environmental exposures from conception onwards, as a new strategy to evidence environmental disease risk factors. Although very appealing, the exposome concept is challenging in many respects. In terms of assessment, several hundreds of time-varying exposures need to be considered, but increasing the number of exposures assessed should not be done at the cost of increased exposure misclassification. Accurately assessing the exposome currently requires numerous measurements, which rely on different technologies; resulting in an expensive set of protocols. In the future, high-throughput ‘omics technologies may be a promising technique to integrate a wide range of exposures from a small numbers of biological matrices. Assessing the association between many exposures and health raises statistical challenges. Due to the correlation structure of the exposome, existing statistical methods cannot fully and efficiently untangle the exposures truly affecting the health outcome from correlated exposures. Other statistical challenges relate to accounting for exposure misclassification or identifying synergistic effects between exposures. On-going exposome projects are trying to overcome technical and statistical challenges. From a public health perspective, a better understanding of the environmental risk factors should open the way to improved prevention strategies.
2015 Paper Abstract
The environment plays a major role in influencing diseases and health. The phenomenon of environmental exposure is complex and humans are not exposed to one or a handful factors but potentially hundreds factors throughout their lives. The exposome, the totality of exposures encountered from birth, is hypothesized to consist of multiple inter-dependencies, or correlations, between individual exposures. These correlations may reflect how individuals are exposed. Currently, we lack methods to comprehensively identify robust and replicated correlations between environmental exposures of the exposome. Further, we have not mapped how exposures associated with disease identified by environment-wide association studies (EWAS) are correlated with other exposures. To this end, we implement methods to describe a first “exposome globe”, a comprehensive display of replicated correlations between individual exposures of the exposome. First, we describe overall characteristics of the dense correlations between exposures, showing that we are able to replicate 2,656 correlations between individual exposures of 81,937 total considered (3%). We document the correlation within and between broad a priori defined categories of exposures (e.g., pollutants and nutrient exposures). We also demonstrate utility of the exposome globe to contextualize exposures found through two EWASs in type 2 diabetes and all-cause mortality, such as exposure clusters putatively related to smoking behaviors and persistent pollutant exposure. The exposome globe construct is a useful tool for the display and communication of the complex relationships between exposure factors and between exposure factors related to disease status.
- The exposome concept: a challenge and a potential driver for environmental health research, ersjournals, 2016.
- Development of exposome correlation globes to map out environment-wide associations, ncbi, PMC4299925, 2015.
- Exposome and Exposomics, cdc, niosh.
- humanexposomeproject website.