Internal Exposome Research Articles

Exposome, oxidative stress and inflammation in multiple sclerosis: the EXPOSITION study protocol

Abstract Background The functional exposome approach examines the relationship between biological effects (internal exposome) and the sum of environmental exposures (external exposome). Multiple sclerosis (MS) is characterized by selective demyelination and acute inflammation; miRNAs and microbiota are emerging in the pathogenesis as inflammation and oxidative stress biomarkers. The EXPOSITION study protocol has been designed to study such biomarkers variation in response to the external exposome (air pollution, urbanization, lifestyles) in people with MS (pwMS). Methods EXPOSITION is a cross-sectional observational study collecting a sample of 200 pwMS residing in Lombardy, Northern Italy. Sample size is based on the prediction of differential expression of candidate miRNAs through bioinformatic analyses. All participants will be investigated for social, demographic and clinical data as well as general and specific external exposome factors. The internal exposome factors will be collected for each participant from blood and stool samples, as well as from nasal swabs. Exposome clustering and correlation statistical techniques will be applied and variation of miRNA and microbiota will be tested in association with the variation of the external exposome in urban and extra-urban environments. Results and conclusions The expected results will help pwMS and researchers understanding which biomarkers and which components of the external exposome are associated to oxidative stress and inflammation, to improve precision medicine and contrast disease progression. The relationship between urban exposome and biodiversity is an important dimension in the study of environmental impact on human health. This study may provide preliminary data to assess which nature-based solutions are suitable for enhancing the biodiversity of urban areas. Key messages • The functional exposome approach could be used to link environmental risk factors and disease biomarkers using the right methology. • EXPOSITION will quantify the variation of miRNA and microbiota in association with the variation of external exposome, in urban and extra-urban environments.

Exposure to air pollutants on maternal internal exposome during pregnancy and its impact on the child neurodevelopment at first year.

Exposure to air pollutants on maternal internal exposome during pregnancy and its impact on the child neurodevelopment at first year.

Mapping the maternal metabolome and internal exposome to identify biomarkers of preterm and early term birth among African Americans

Mapping the maternal metabolome and internal exposome to identify biomarkers of preterm and early term birth among African Americans

Exploring Internal Exposome and Biological Systems through Multi-Omics Integration: Insights into Gestational Age at Delivery among African Americans

Exploring Internal Exposome and Biological Systems through Multi-Omics Integration: Insights into Gestational Age at Delivery among African Americans

Geospatial Science for the Environmental Epidemiology of Cancer in the Exposome Era.

Geospatial science is the science of location or place that harnesses geospatial tools, such as geographic information systems (GIS), to understand the features of the environment according to their locations. Geospatial science has been transformative for cancer epidemiologic studies through enabling large-scale environmental exposure assessments. As the research paradigm for the exposome, or the totality of environmental exposures across the life course, continues to evolve, geospatial science will serve a critical role in determining optimal practices for how to measure the environment as part of the external exposome. The objectives of this article are to provide a summary of key concepts, present a conceptual framework that illustrates how geospatial science is applied to environmental epidemiology in practice and through the lens of the exposome, and discuss the following opportunities for advancing geospatial science in cancer epidemiologic research: enhancing spatial and temporal resolutions and extents for geospatial data; geospatial methodologies to measure climate change factors; approaches facilitating the use of patient addresses in epidemiologic studies; combining internal exposome data and geospatial exposure models of the external exposome to provide insights into biological pathways for environment-disease relationships; and incorporation of geospatial data into personalized cancer screening policies and clinical decision making.

3D Airway Epithelial-Fibroblast Biomimetic Microfluidic Platform to Unravel Engineered Nanoparticle-Induced Acute Stress Responses as Exposome Determinants.

Insights into how biological systems respond to high- and low-dose acute environmental stressors are a fundamental aspect of exposome research. However, studying the impact of low-level environmental exposure in conventional in vitro settings is challenging. This study employed a three-dimensional (3D) biomimetic microfluidic lung-on-chip (μLOC) platform and RNA-sequencing to examine the effects of two model anthropogenic engineered nanoparticles (NPs): zinc oxide nanoparticles (Nano-ZnO) and copier center nanoparticles (Nano-CCP). The airway epithelium exposed to these NPs exhibited dose-dependent increases in cytotoxicity and barrier dysregulation (dominance of the external exposome). Interestingly, even nontoxic and low-level exposure (10 μg/mL) of the epithelium compartment to Nano-ZnO triggered chemotaxis of lung fibroblasts toward the epithelium. An increase in α smooth muscle actin (α-SMA) expression and contractile activity was also observed in these cells, indicating a bystander-like adaptive response (dominance of internal exposome). Further bioinformatics and network analysis showed that a low-dose Nano-ZnO significantly induced a robust transcriptomic response and upregulated several hub genes associated with the development of lung fibrosis. We propose that Nano-ZnO, even at a no observable effect level (NOEL) dose according to conventional standards, can function as a potent nanostressor to disrupt airway epithelium homeostasis. This leads to a cascade of profibrotic events in a cross-tissue compartment fashion. Our findings offer new insights into the early acute events of respiratory harm associated with environmental NPs exposure, paving the way for better exposomic understanding of this emerging class of anthropogenic nanopollutants.

Exposome: from definition to future challenges.

The exposome concept arises from the need to integrate different disciplines of public health and environmental sciences, mainly including environmental epidemiology, exposure science, and toxicology. The role of the exposome is to understand how the totality of an individual's exposures throughout the lifetime can impact human health. The etiology of a health condition is rarely explained by a single exposure. Therefore, examining the human exposome as a whole becomes relevant to simultaneously consider multiple risk factors and more accurately estimate concurrent causes of different health outcomes. Generally, the exposome is explained through three domains: general external exposome, specific external exposome, and internal exposome. The general external exposome includes measurable population-level exposures such as air pollution or meteorological factors. The specific external exposome includes information on individual exposures, such as lifestyle factors, typically obtained from questionnaires. Meanwhile, the internal exposome encompasses multiple biological responses to external factors, detected through molecular and omics analyses. Additionally, in recent decades, the socio-exposome theory has emerged, where all exposures are studied as a phenomenon dependent on the interaction between socioeconomic factors that vary depending on the context, allowing the identification of mechanisms that lead to health inequalities. The considerable production of data in exposome studies has led researchers to face new methodological and statistical challenges, introducing various approaches to estimate the effect of the exposome on health. Among the most common are regression models (Exposome-Wide Association Study - ExWAS), dimensionality reduction and exposure grouping techniques, and machine learning methods. The significant conceptual and methodological innovation of the exposome for a more holistic evaluation of the risks associated with human health is continuously expanding and will require further investigations related to the application of information obtained from studies into prevention and public health policies.

Exploring the internal exposome of seminal plasma with semen quality and live birth: A Pilot Study

Infertility is clinically defined as the inability to achieve pregnancy within 12 months of regular unprotected sexual intercourse and affects 15% of couples worldwide. Therefore, the identification of novel biomarkers that can accurately predict male reproductive health and couples’ reproductive success is of major public health significance. The objective of this pilot study is to test whether untargeted metabolomics is capable of discriminating reproductive outcomes and understand associations between the internal exposome of seminal plasma and the reproductive outcomes of semen quality and live birth among ten participants undergoing assisted reproductive technology (ART) in Springfield, MA. We hypothesize that seminal plasma offers a novel biological matrix by which untargeted metabolomics is able to discern male reproductive status and predict reproductive success. The internal exposome data was acquired using UHPLC-HR-MS on randomized seminal plasma samples at UNC at Chapel Hill. Unsupervised and supervised multivariate analyses were used to visualize the differentiation of phenotypic groups classified by men with normal or low semen quality based on World Health Organization guidelines as well as by successful ART: live birth or no live birth. Over 100 exogenous metabolites, including environmentally relevant metabolites, ingested food components, drugs and medications, and metabolites relevant to microbiome-xenobiotic interaction, were identified and annotated from the seminal plasma samples, through matching against the NC HHEAR hub in-house experimental standard library. Pathway enrichment analysis indicated that fatty acid biosynthesis and metabolism, vitamin A metabolism, and histidine metabolism were associated sperm quality; while pathways involving vitamin A metabolism, C21-steroid hormone biosynthesis and metabolism, arachidonic acid metabolism, and Omega-3 fatty acid metabolism distinguished live birth groups. Taken together, these pilot results suggest that seminal plasma is a novel matrix to study the influence of the internal exposome on reproductive health outcomes. Future research aims to increase the sample size to validate these findings.

Assessing How Social Exposures Are Integrated in Exposome Research: A Scoping Review.

Exposome research aims to describe and understand the extent to which all the exposures in human environments may affect our health over the lifetime. However, the way in which humans interact with their environment is socially patterned. Failing to account for social factors in research exploring the exposome may underestimate the magnitude of the effect of exposures or mask inequalities in the distribution of both exposures and outcomes. We aimed to describe the extent to which social factors appear in the exposome literature, the manner in which they are used in empirical analyses and statistical modeling, and the way in which they are considered in the overall scientific approach. We conducted a scoping review of the literature using three databases (PubMed, Embase, and Web of Science) up to January 2022. We grouped studies based on the way in which the social variables were used in the analyses and quantified the type and frequency of social variables mentioned in the articles. We also qualitatively described the scientific approach used by authors to integrate social variables. We screened 1,001 records, and 73 studies were included in the analysis. Fifty-five () used social variables as exposures or confounders or both, and a wide array of social variables were represented in the articles. Individual-level social variables were more often found, especially education and race/ethnicity, as well as neighborhood-level deprivation indices. Half of the studies used a hypothesis-free approach and the other half, a hypothesis-driven approach. However, in the latter group, of 35 studies, only 8 reported and discussed at least one possible social mechanism underlying the relationship observed between the social variable and the outcome. Social factors in exposome research should be considered in a more systematic way, considering their role in structuring both the specific external and the internal exposome. Doing so could help to understand the mechanisms of construction and, potentially, alleviate social inequalities in health and mitigate the emergence of new ones. https://doi.org/10.1289/EHP11015.

Invited Perspective: The Mysterious Case of Social Determinants of Health.

Invited Perspective: The Mysterious Case of Social Determinants of Health.

A Holistic Approach to Urban and Children’s Mental Health

Abstract Background EU data show that there is a continuous increase in mental health problems in children. The multiple exposures in the physical and social domain influence the internal exposome and the final health outcomes. The Equal-Life project research focuses on the exposome (physical, social and internal) and mental health of children and adolescents. Methods Literature reviews on children's mental health and a total of physical and social exposures from 9 different European cohorts are used to set a framework of data interpretation. In addition, information gathered from 3 surveys/65 interviews with stakeholders from different fields was used to look for a transdisciplinary framework for analysis of the cohort data. The approach develops (in a co-design approach) tools that help stakeholders to collect and organize the information necessary to make decisions. The exposome is as if it were a multilayer system and requires approaches that are able to manage the interconnections between the various variables involved in the field of children's mental health. Results The main points extracted are an early life exposure to urban planning related factors (noise/air pollution, traffic), social factors (family relations, stress), biomarkers related to environmental and social exposures. Concerning the life course approach, vulnerable settings were identified such as schools, neighbourhoods, accessibility to green restorative spaces. These ingredients are the basis of interaction between scientists and community stakeholders and from the policy domains to find and interpret the scientific results for the implementation of protective and promotive policies in cities. Conclusions Transdisciplinary approach is necessary for management and developing strategies for solving mental health problems in urban spaces when considering all kind of exposures. The development of tools through co-design sessions with different stakeholders gives important contributions for this goal. Key messages • Development of interventions and policies for better mental health of children and adolescents should be based on available evidence for meaning of external and social exposome. • The main outcome of Equal-Life is to develop tools where stakeholders have access and opportunity to use it for solving mental health issues at national or local level.

Differential Effects of mTORC1 and mTORC2 Inhibition on High-Resolution Mass Spectrometry (HRMS) Metabolomics and the Internal Exposome in Pancreatic Beta Cell Lines

ObjectivesThe mechanistic Target of Rapamycin Complexes (mTORC1/mTORC2) are critical nodes for metabolism. We applied an HRMS-based untargeted metabolomics approach to determine the role of mTORC1/mTORC2 on the internal exposome in pancreatic cell line (β-TC6). mTORC1 is a nutrient-sensing network, while mTORC2 phosphorylates Akt on Ser473 and modulates energy metabolism, thus mTORC1/mTORC2 are targets for precision nutrition.MethodsWe used glucose-responsive, insulin-secreting, pancreatic beta-cell lines. mTORC1/mTORC2 were inhibited by RapaLink-1, a third-generation inhibitor encompassing rapamycin linked to an mTOR kinase inhibitor, or rapamycin, compared to the control. We compared the HRMS-based untargeted metabolomics (LC-MS/MS) between groups to identify the differentially expressed metabolites, predictive metabolic networks, and systems biology pathways. We employed the XCMS online cloud-based bioinformatics platform to link mTOR-regulated metabolites to biological pathways using the python mummichog algorithm. Statistical significance (P < 0.001) was assessed by ANOVA followed by adhoc unpaired t-test.ResultsPCA dimension reduction and cloud plot clustering machine learning showed differential expression of metabolites between RapaLink and rapamycin-treated pancreatic beta cells. RapaLink significantly increased aminobutyrate (P < 0.001), D-glucose (p = 0.02), and O-phosphoryl ethanolamine (p = 0.003), compared to rapamycin. RapaLink also decreased glycine level (P < 0.000001) compared to the control. While both RapaLink and rapamycin decreased alanine (p = 0.003), L-asparagine (p = 0.01), L- aspartate (p < 0.001), taurine (p = 0.003), and uridine monophosphate (p = 0.004) compared to the control. The predictive metabolic pathways affected included malate-aspartate shuttle, adenosine nucleotide degradation, and glucose degradation.ConclusionsmTORC1 and mTORC2 have differential effects on glucose, bile acids, short-chain fatty acids, nucleotides, and amino acid metabolism, and thus could serve as targets for precision nutrition in pancreatic diseases and type 2 diabetes interventions.Funding SourcesFunded by the City University of New York, GC Advanced Science Research Center Seed Grant Award # 95,649–00. XCMS online is a cloud-based open-source bioinformatics platform developed by the Scripps Institute.

Analytical strategies to profile the internal chemical exposome and the metabolome of human placenta

As a non-invasive biological matrix, the placenta offers great and novel opportunities to monitor fetal exposure to exogenous chemicals and their biotransformation products (the internal chemical exposome), as well as the biological responses associated, in large-scale epidemiological studies. However, it is first crucial to ensure that analytical methods based on high-resolution mass spectrometry (HRMS) can detect the low abundant components of the internal chemical exposome present in these complex biological matrices. In this study, we aimed to develop a robust analytical method (extraction and sample preparation) sensitive enough to profile the internal chemical exposome and the metabolome of placenta using high-resolution mass spectrometry (HRMS) for future application in mother child cohorts. Several extraction solvents (methanol, methanol/H2O (50/50 v/v), methyl tert-butyl ether/methanol/H2O) were tested and their ability to extract components of the internal exposome and metabolome were compared. Then, sample preparation methods commonly used for metabolomics application (methanolic protein precipitation) were compared with solid phase extraction (SPE), protein and phospholipid removal plates (PPRP) and combination of SPE and PPRP. The methods were compared and validated using qualitative (i.e., numbers of features and chemical classes ID), quantitative parameters adopted from targeted multi-residue analysis (recovery experiments, repeatability and matrix effect) as well as the ability of these methods to be implemented for high-throughput applications. The analytical repeatability of the two most effective methods (methanolic extraction followed by either protein precipitation or PPRP) were tested at the batch level to determine the best concentration factors to be used for improving detection of components of the internal chemical exposome and metabolome without impacting on the analytical response. Finally, these two methods based on protein precipitation and PPRP were tested on 40 placenta samples from the French PELAGIE birth cohort, and annotation was performed on the related datasets to compare the respective impacts of PPT and PPRP. A wide range of exogenous (e.g., biocides, pharmaceuticals, personal care products) and endogenous chemicals (steroids, prostanoids, lipids, carnitins) could be detected and annotated (some of them for the first time in placenta). We show that both methods are complementary but that PPRP allows the injection of more concentrated extracts without impacting the LC repeatability and therefore improve the detection (presence and signal area fold change) of many exogenous and endogenous chemicals.

Editorial] Gut microbiota modulation: A tailored approach for the prevention of chronic diseases

Editorial] Gut microbiota modulation: A tailored approach for the prevention of chronic diseases

Validation of external and internal exposome of the findings associated to cerebral small vessel disease: A Mendelian randomization study

The exposome characterizes all environmental exposures and their impact on a disease. To determine the causally-associated components of the exposome for cerebral small vessel disease (CSVD), we performed mendelian randomization analysis of 5365 exposures on six clinical and subclinical CSVD measures. We found statistically significant evidence (FDR-corrected P < 0.05) that hypertension, high cholesterol, longer television-watching time, lower educational qualifications, younger age of first sexual intercourse, smoking, reduced pulmonary function, higher subjective overall health rating, and frequent tiredness were associated with increased risk of intracerebral hemorrhage or small vessel stroke. Adiposity, diabetes, frequent alcoholic drinks, higher white blood cell count and neutrophil count were significantly associated with higher risk of non-lobar hemorrhage or small vessel stroke, but not lobar hemorrhage. Hypertension, higher arm or leg fat-free mass and higher sitting height were significantly associated with higher white matter hyperintensities. The results were robust to sensitivity analyses and showed no evidence of horizontal pleiotropy. We also identified 41 exposures suggestively associated (uncorrected P < 0.05) with multiple CSVD measures as the “the CSVD exposome”. This exposome-wide association study provides insight into CSVD development and prevention.

A concise review towards defining the exposome of oesophageal cancer in sub-Saharan Africa.

Oesophageal cancer (EC) is among the common causes of illness and death among all cancers worldwide. Advanced EC has a poor prognosis, with worse outcomes observed in low-income settings. Oesophageal squamous cell carcinoma (ESCC) is the most common EC histology reported globally, with the highest ESCC incidence rates in the 'Asian Belt' and the African EC corridor. While the aetiology of ESCC is well-documented in the 'Asian belt', data for the African EC corridor and the entirety of sub-Saharan Africa (SSA) are fewer. To help address gaps in ESCC aetiology in SSA, we critically evaluated evidence of lifestyle, environmental, and epigenetic factors associated with ESCC risk and discussed prospects of defining ESCC exposome. Unlimited English and non-English articles search were made on PubMed Central and Web of Science databases from January 1970 to August 2021. In total, we retrieved 999 articles and considered meta-analyses, case-control, and cohort studies. The quality of individual studies was assessed using the Newcastle-Ottawa scale. Details extracted include the year of publication, country of origin, sample size, comparators, outcomes, study subjects, and designs. Together, we assessed 13 case-control studies and two meta-analyses for the effect of lifestyle or environmental exposures on ESCC risk. Again, we evaluated seven case-control studies and one meta-analysis regarding the role of epigenetics in ESCC tumorigenesis. In general, evidence of ESCC aetiology points to essential contributions of alcohol, tobacco, hot beverages, biomass fuel, and poor oral health/hygiene, although more precise risk characterisation remains necessary. We conclude that ESCC in SSA is a multifactorial disease initiated by several external exposures that may induce aberrant epigenetic changes. The expanding aetiological research in this domain will be enhanced by evidence synthesis from classical and molecular epidemiological studies spanning the external and internal exposome.

Environmental risk factors of type 2 diabetes-an exposome approach.

Type 2 diabetes is one of the major chronic diseases accounting for a substantial proportion of disease burden in Western countries. The majority of the burden of type 2 diabetes is attributed to environmental risks and modifiable risk factors such as lifestyle. The environment we live in, and changes to it, can thus contribute substantially to the prevention of type 2 diabetes at a population level. The 'exposome' represents the (measurable) totality of environmental, i.e. nongenetic, drivers of health and disease. The external exposome comprises aspects of the built environment, the social environment, the physico-chemical environment and the lifestyle/food environment. The internal exposome comprises measurements at the epigenetic, transcript, proteome, microbiome or metabolome level to study either the exposures directly, the imprints these exposures leave in the biological system, the potential of the body to combat environmental insults and/or the biology itself. In this review, we describe the evidence for environmental risk factors of type 2 diabetes, focusing on both the general external exposome and imprints of this on the internal exposome. Studies provided established associations of air pollution, residential noise and area-level socioeconomic deprivation with an increased risk of type 2 diabetes, while neighbourhood walkability and green space are consistently associated with a reduced risk of type 2 diabetes. There is little or inconsistent evidence on the contribution of the food environment, other aspects of the social environment and outdoor temperature. These environmental factors are thought to affect type 2 diabetes risk mainly through mechanisms incorporating lifestyle factors such as physical activity or diet, the microbiome, inflammation or chronic stress. To further assess causality of these associations, future studies should focus on investigating the longitudinal effects of our environment (and changes to it) in relation to type 2 diabetes risk and whether these associations are explained by these proposed mechanisms.

Decoding our environment: The European Human Exposome Network

BACKGROUND AND AIM: European citizens are increasingly concerned about the effects of climate change, urbanization, and environmental deterioration on health. This concern is well reflected in the European Green Deal and the cross-cutting zero-pollution strategy that has the ambition to: “protect citizens' health from environmental degradation and pollution, address air and water quality, hazardous chemicals, industrial emissions, pesticides and endocrine disruptors”. The sum of the environmental exposures to people-kind is called the exposome and can nowadays be systematically measured. Exposome research is recognized by the European Commission as an important innovative research area that could significantly contribute to these ambitions and future policies. METHODS: The European Human Exposome Network (EHEN) was initiated in 2020 and consists of 9 large-scale projects in which a total of 126 partners from 24 countries participate. EHEN is tasked to develop a FAIR (Findable Accessible Interoperable Reusable) Toolbox for exposome research including but not limited to the development of new assessment methods for the external (e.g. sensors, geospatial models) and internal exposome (e.g. biomonitoring, OMICs-technologies); linkage of these measures to health records in bespoke and administrative datasets; developing methods for causal and biological interpretation of results; and to translate knowledge into impact through novel intervention strategies. RESULTS:In the first year of EHEN significant steps have been made in cross-cutting working groups to address common challenges and opportunities. An example is the FAIRification of exposome research in Europe and on ethical considerations in exposome research. CONCLUSIONS:The EHEN is a significant boost to exposome research in Europe and beyond. Besides scientific challenges, there are also legal and political challenges not in the least how we link exposome findings into policy such as the European Green Deal and the cross-cutting zero-pollution strategy. KEYWORDS: Exposome, Green deal, FAIR, external exposome, internal exposome, causal inference

A non-targeted approach to identify potential breast carcinogens in women firefighters after a fire event

BACKGROUND AND AIM: Female firefighters remain understudied in both exposure and epidemiology studies. Furthermore, occupational studies generally focus on toxic chemicals that are well characterized. The objective of this study was to identify potentially novel chemical exposures associated with a fire event among female firefighters. METHODS: We applied non-targeted analysis methods to three longitudinal serum samples collected in the days and weeks after a fire. To assess exposure to potential breast carcinogens among women workers after an urban structural fire event the Women Workers Biomonitoring Collaborative (WWBC), we recruited female firefighters in San Francisco and developed a biospecimen archive. Female firefighters (n=18) were recruited and provided 3 serum samples—within 48 hours, 1 week, and 1 month after fighting a fire. We applied a non-targeted analytical approach with liquid chromatography quadrupole time of flight mass spectrometry (LC-QTOF/MS) in both the positive and negative ionization modes. RESULTS:We detected over 20,000 features, representing potential chemical exposures in study participants. Exact masses of features were matched to a curated in-house library of 7,935 environmental chemicals and potential breast carcinogens, tentatively identifying 1,667 chemicals. MS/MS fragmentation analysis allowed us to further confirm 181 candidate chemicals based on the predicted fragmentation pattern of each chemical. These chemicals included per-/poly-fluoroalkyl substances, endocrine disrupting chemicals and chemicals associated with mammary tumor development. We will confirm the identity of at least 5 of these novel chemicals by re-running the samples with known standards. CONCLUSIONS:Non-targeted analytical approaches in carefully designed exposure studies can help “look beyond the lamp post” to identify novel exposures with health concerns. KEYWORDS: non-targeted analysis, generalized suspect screen, occupational exposures, internal exposome

Hemoglobin adducts of acrylamide in human blood – what has been done and what is next?

BACKGROUND AND AIM: Acrylamide is found in many commonly consumed foods. Dietary exposure is of concern and food is being monitored worldwide as acrylamide is neurotoxic, crosses the placenta, restricts intrauterine growth and increases the risk of certain cancers and obesity. In animals, acrylamide causes heritable mutations, tumors, developmental, reproductive, and neurotoxicity. The impact on human health of dietary exposure to acrylamide remains poorly understood and it is impossible to say what level can be deemed safe as the assessment of acrylamide from diet is uncertain. We aim to summarize the internal dose of acrylamide in humans measured through quantification of hemoglobin (Hb) N-terminal valine adduct levels from acrylamide using mass spectrometric methods METHODS: We performed a search up to February 2020 and included peer-reviewed articles and reports in English. Data were extracted and mean Hb adduct levels by smoking status and country of origin were calculated. RESULTS:Methods and results from a total of 75 studies of 31,202 individuals from 15 countries were reviewed. Adduct levels were highest in occupational exposed individuals and three-fold higher in smokers as compared to non-smokers. Adducts ranged from 3 to 210 pmol/g Hb in non-smokers and this wide range suggests that dietary exposure to acrylamide varies largely. Relative to smoking, the correlation between estimated dietary intake of acrylamide and Hb adducts was weak and the validity of the methods used for assessment of dietary intake vary. Non-smokers from the USA and Canada had higher levels as compared with non-smokers from Europe and Asia. Within Europe, individuals from UK had the highest levels. CONCLUSIONS:Large studies starting with early-life exposures using validated high-throughput analyses of adducts from acrylamide and other heat-generated compounds, together with comprehensive assessment of diet, smoking and socio-economic factors, would improve evaluation of the effects of dietary acrylamide on health. KEYWORDS: Biomarkers of exposure, Food, Internal exposome