Exposure Load: Using biomonitoring data to quantify multi-chemical exposure burden in a population

Analytical challenges and opportunities in the study of endocrine disrupting chemicals within an exposomics framework

Exposomics aims to measure human exposures throughout the lifespan and the changes they produce in the human body. Exposome-scale studies have significant potential to understand the interplay of environmental factors with complex multifactorial diseases widespread in our society and whose origin remain unclear. In this framework, the study of the chemical exposome aims to cover all chemical exposures and their effects in human health but, today, this goal still seems unfeasible or at least very challenging, which makes the exposome for now only a concept. Furthermore, the study of the chemical exposome faces several methodological challenges such as moving from specific targeted methodologies towards high-throughput multitargeted and non-targeted approaches, guaranteeing the availability and quality of biological samples to obtain quality analytical data, standardization of applied analytical methodologies, as well as the statistical assignment of increasingly complex datasets, or the identification of (un)known analytes. This review discusses the various steps involved in applying the exposome concept from an analytical perspective. It provides an overview of the wide variety of existing analytical methods and instruments, highlighting their complementarity to develop combined analytical strategies to advance towards the chemical exposome characterization. In addition, this review focuses on endocrine disrupting chemicals (EDCs) to show how studying even a minor part of the chemical exposome represents a great challenge. Analytical strategies applied in an exposomics context have shown great potential to elucidate the role of EDCs in health outcomes. However, translating innovative methods into etiological research and chemical risk assessment will require a multidisciplinary effort. Unlike other review articles focused on exposomics, this review offers a holistic view from the perspective of analytical chemistry and discuss the entire analytical workflow to finally obtain valuable results.

Cumulative Health Risk from Exposure Load (CHREL): Looking at multi-chemical exposures through the lens of biomonitoring guidance values

Exposure load (EL) is an indicator of multiple chemical exposures based on human biomonitoring data. We used EL methodology and human biomonitoring health-based guidance values (HB2GVs) as exposure thresholds to create a new metric called Cumulative Health Risk from Exposure Load (CHREL). HB2GVs are derived by calculating the concentration of a biomarker consistent with a health protective exposure guidance value. CHREL analysis was conducted using Canadian Health Measures Survey (CHMS) cycle 3 and 4 biomonitoring data. Based on 18 chemicals, more than half of the Canadian population had an estimated CHRELTOTAL of 1 or more, indicative of chemical exposures potentially above selected exposure guidance values. Females had a significantly lower CHRELTOTAL compared to males, 12-19 year olds had a lower CHRELTOTAL compared to older age groups (significant compared to 40-59 year olds), and nonsmokers had a significantly lower CHRELTOTAL than smokers. Small segments of the population had a CHRELLIVER or a CHRELNERV of 1 or more, indicating exposures potentially above guideline levels for chemicals affecting the liver or nervous system. CHRELCANC was calculated based on 6 chemicals with HB2GVs derived for cancer endpoints. At the 10-5 risk level, most people had an estimated CHRELCANC of 3, indicative of multiple chemicals that may exceed negligible cancer risk. The most important contributors to exposures above HB2GVs were inorganic arsenic, mercury, acrylamide, xylenes, benzene and triclosan. Keeping certain assumptions, uncertainties and limitations in mind, the CHREL indicator can be used to obtain a picture of potential cumulative health risks from combined chemical exposures in a population, and as a comparative measure between subpopulations, including vulnerable subgroups.

Associations between paediatric obesity, chemical mixtures and environmental factors, in a national cross-sectional study of Canadian children

BACKGROUND

Whilst single chemical exposures are suspected to be obesogenic, the combined role of chemical mixtures in paediatric obesity is not well understood.

OBJECTIVES

We aimed to evaluate the potential associations between chemical mixtures and obesity in a population-based sample of Canadian children.

METHODS

We ascertained biomonitoring and health data for children aged 3-11 from the cross-sectional Canadian Health Measures Survey from 2007 to 2019. Several chemicals of interest were measured in blood or urine and paediatric obesity was defined based on measured anthropometrics. Using quantile-based G computational analysis, we quantified the effects of three chemical mixtures selected a priori. Models were adjusted for sociodemographic and environmental factors identified through a directed acyclic graph. Results are presented through adjusted relative risks (RR) with 95% confidence intervals (95% CI).

RESULTS

We included 9147 children. Of these, 24.1% were overweight or obese. Exposure to the mixture of bisphenol A, acrylamide, glycidamide, metals, parabens and arsenic increased the risk of childhood overweight or obesity by 45% (95% CI 1.09, 1.93), obesity by 109% (95% CI 1.27, 3.42) and central obesity by 82% (95% CI 1.30, 2.56).

CONCLUSIONS

Our findings support the role of early childhood chemical exposures in paediatric obesity and the potential combined effects of chemicals.

Analysis of chemical exposures in racial populations in Canada: An investigation based on the Canadian health measures survey

Despite demonstrated disparities in environmental chemical exposures by racial identity, no Canadian study has systematically assessed the feasibility of using a nationally representative dataset to examine differences in chemical concentrations by race. We assessed the feasibility and constraints of analysing chemical exposures in racial populations, including visible minorities and populations of Indigenous identity, using biomonitoring data collected through the Canadian Health Measures Survey (CHMS). Our primary objectives were to assess the ability to 1) generate geometric means and percentiles of chemical concentrations for racial populations by age or sex, 2) statistically compare concentrations among racial populations, and 3) calculate time trends of concentrations by race. We conducted these analyses for several priority chemicals: lead, cadmium, benzene, bisphenol A (BPA), and di(2-ethylhexyl) phthalate (DEHP). Survey participants self-identified as one of the following: White, Black, East and Southeast Asian, South Asian, Middle Eastern, Latin American, First Nations, Metis, and Inuit. Analyses were conducted for individual and combined cycles of the CHMS. Using data from the latest CHMS cycle in which each chemical was measured, we observed that sample sizes were sufficient to report geometric mean concentrations for all races except Inuit. Due to privacy considerations associated with small sample sizes, the 5th and 95th percentile concentrations could not be consistently reported for all racial populations in this analysis. While we were able to statistically compare concentrations among racial populations, the analysis was constrained by the limited number of statistical degrees of freedom available in a single CHMS cycle. Both of these constraints were alleviated by combining multiple cycles of data. The analysis of time trends was less subject to privacy and statistical limitations; we were able to calculate time trends of chemical concentrations for all racial populations. Our findings provide an important baseline for follow-up investigations of descriptive and etiological analyses of environmental chemical exposures and race in the CHMS.

Association between exposure to chemical mixtures and epigenetic ageing biomarkers: Modifying effects of thyroid hormones and physical activity

Evidence on the effects of internal chemical mixture exposures on biological age is limited. It also remains unclear whether hormone homeostasis and lifestyle factors can modify such a relationship. Based on the Biomarkers for Air Pollutants Exposure (BAPE) study, which involved healthy older adults aged 60-69 years in China, we found that chemical mixture exposures, including metals, polycyclic aromatic hydrocarbons (PAHs), per- and polyfluoroalkyl substances (PFASs), phthalates (PAEs), and organophosphate esters (OPEs), were significantly associated with shortened DNAmTL and accelerated SkinBloodClock, in which PFASs and OPEs in blood were the primary contributors to DNAmTL, while metals and PAEs had relatively higher contributions in urine. Furthermore, lower levels of thyroxin appeared to exacerbate the adverse effects of environmental chemicals on epigenetic ageing but relatively higher levels of physical activity had the beneficial impact. These findings may have important implications for the development of healthy ageing strategy and aged care policy, particularly in light of the global acceleration of population ageing.

Metabolomics perspectives into the co-exposure effect of polycyclic aromatic hydrocarbons and metals on renal function: A meet-in-the-middle approach

Studies on the dose effects of kidney impairment and metabolomes in co-exposure to polycyclic aromatic hydrocarbons (PAHs) and metals are limited. We aimed to identify overall associations and metabolic perturbations in 130 participants (53 petrochemical workers and 77 controls) exposed to a PAHs-metals mixture in Southern China. The urinary 7 hydroxylated PAHs and 15 metal(loid)s were determined, and serum creatinine, beta-2 microglobulin, and estimated glomerular filtration rate were health outcomes. The liquid chromatography-mass spectrometry-based method was applied to serum metabolomics. Generalized weighted quantile sum (gWQS) regressions were used to estimate the overall dose-response relationships, and pathway analysis, "meet-in-the-middle" approach, and mediation effect analyses were conducted to identify potential metabolites and biological mechanisms linking exposure with nephrotoxic effects. Our results indicated that renal function reduction was associated with a PAHs-metals mixture in a dose-dependent manner, and 1-hydroxynaphthalene and copper were the most predominant contributors among the two families of pollutants. Furthermore, the metabolic disruptions associated with the early onset of kidney impairment induced by the combination of PAHs and metals encompassed pathways such as phenylalanine-tyrosine-tryptophan biosynthesis, phenylalanine metabolism, and alpha-linolenic acid metabolism. In addition, the specifically identified metabolites demonstrated excellent potential as bridging biomarkers connecting the reduction in renal function with the mixture of PAHs and metals. These findings shed light on understanding the overall associations and metabolic mechanism of nephrotoxic effects of co-exposure to PAHs and metals.

[Sustainability and climate protection : Implications on patient-centered care in radiology]

BACKGROUND

Sustainability and patient-centered radiology (PCR) include a multivariant, complex network of synergic and opportunistic elements. PCR is a subfactor of the social element, climate protection is part of the ecological element, and sustainable economics are part of the financial element.

OBJECTIVES

We aimed to identify PCR-symbiotic and PCR-opposed elements of sustainability using literature research. This article will provide an overview of the core sustainability elements and innovative concepts for supporting PCR.

MATERIALS AND METHODS

A digital literature search was carried out to identify scientific publications about sustainability and PCR via Medline. Results are provided as a narrative summary.

RESULTS

In particular, the social component and parts of the ecological element of sustainability support PCR. Climate protection and a natural environment show a positive correlation with health and patient satisfaction. Patient contact improves the quality of the diagnostic report and promotes satisfaction of patients and radiologists. However, increasing economization is often conditionally compatible with the social core element of sustainability and especially with PCR. Digital tools can ease communication and improve reports in times of increasing workload.

CONCLUSION

Socially and environmentally sustainable radiology supports the well-being of both employees and patients. Innovative concepts are necessary to balance the ecological elements of sustainability with employees' and patients' interests.

HBM4EU results support the Chemicals' Strategy for Sustainability and the Zero-Pollution Action Plan

One of the major goals of the European Human Biomonitoring Initiative (HBM4EU) was to bridge the gap between science and policy by consulting both policy makers and national scientists and generating evidence of the actual exposure of residents to chemicals and whether that exposure would be suggest a potential health risk. Residents' perspectives on chemical exposure and risk were also investigated. HBM4EU's research was designed to answer specific short-term and long-term policy questions at national and European levels, and for its results to directly support regulatory action on chemicals. A strategy was established to prioritise chemicals for analysis in human matrices, with a total of 18 substances/substance groups chosen to be investigated throughout the five-and a -half-year project. HBM4EU produced new evidence of human exposure levels, developed reference values for exposure, investigated determinants of exposure and derived health-based guidance values for those substances. In addition, HBM4EU promoted the use of human biomonitoring data in chemical risk assessment and developed innovative tools and methods linking chemicals to possible health impacts, such as effect biomarkers. Furthermore, HBM4EU advanced understand of effects from combined exposures and methods to identify emerging chemicals. With the aim of supporting policy implementation, science-to-policy workshops were organised, providing opportunities for joint reflection and dialogue on research results. I, and indicators were developed to assess temporal and spatial patterns in the exposure of European population. A sustainable human biomonitoring monitoring framework, producing comparable quality assured data would allow: the evaluation of time trends; the exploration of spatial trends: the evaluation of the influence of socio-economic conditions on chemical exposure. Therefore, such a framework should be included in the European Chemicals' Strategy for Sustainability and the data would support the Zero Pollution Action Plan.

Towards Whole Health Toxicology: In-Silico Prediction of Diseases Sensitive to Multi-Chemical Exposures

Chemical exposures from diverse sources merge on a limited number of molecular pathways described as toxicity pathways. Changes in the same set of molecular pathways in different cell and tissue types may generate seemingly unrelated health conditions. Today, no approaches are available to predict in an unbiased way sensitivities of different disease states and their combinations to multi-chemical exposures across the exposome. We propose an inductive in-silico workflow where sensitivities of genes to chemical exposures are identified based on the overlap of existing genomic datasets, and data on sensitivities of individual genes is further used to sequentially derive predictions on sensitivities of molecular pathways, disease states, and groups of disease states (syndromes). Our analysis predicts that conditions representing the most significant public health problems are among the most sensitive to cumulative chemical exposures. These conditions include six leading types of cancer in the world (prostatic, breast, stomach, lung, colorectal neoplasms, and hepatocellular carcinoma), obesity, type 2 diabetes, non-alcoholic fatty liver disease, autistic disorder, Alzheimer's disease, hypertension, heart failure, brain and myocardial ischemia, and myocardial infarction. Overall, our predictions suggest that environmental risk factors may be underestimated for the most significant public health problems.

Mixture Math: Deciding What to Add in a Cumulative Risk Assessment

Component-based approaches for cumulative risk assessment provide an important tool for informing public health policy. While current quantitative cumulative risk assessments focus narrowly on pesticides that share a mechanism of action, growing scientific evidence supports expansion of their application to encompass stressors that target a common disease. Case studies have demonstrated dose additive effects of chemicals with different mechanisms of action on liver steatosis, craniofacial malformations, and male reproductive tract developmental disruption. Evidence also suggests that nonchemical stressors such as noise or psychosocial stress can modify effects of chemicals. Focused research attention is required before nonchemical stressors can routinely be included in quantitative cumulative risk assessments.

FLEXiGUT: Rationale for exposomics associations with chronic low-grade gut inflammation

FLEXiGUT is the first large-scale exposomics study focused on chronic low-grade inflammation. It aims to characterize human life course environmental exposure to assess and validate its impact on gut inflammation and related biological processes and diseases. The cumulative influences of environmental and food contaminants throughout the lifespan on certain biological responses related to chronic gut inflammation will be investigated in two Flemish prospective cohorts, namely the "ENVIRONAGE birth cohort", which provides follow-up from gestation to early childhood, and the "Flemish Gut Flora Project longitudinal cohort", a cohort of adults. The exposome will be characterised through biomonitoring of legacy and emerging contaminants, mycotoxins and markers of air pollution, by analysing the available metadata on nutrition, location and activity, and by applying state-of-the-art -omics techniques, including metagenomics, metabolomics and DNA adductomics, as well as the assessment of telomere length and measurement of inflammatory markers, to encompass both exposure and effect. Associations between exposures and health outcomes will be uncovered using an integrated -omics data analysis framework comprising data exploration, pre-processing, dimensionality reduction and data mining, combined with machine learning-based pathway analysis approaches. This is expected to lead to a more profound insight in mechanisms underlying disease progression (e.g. metabolic disorders, food allergies, gastrointestinal cancers) and/or accelerated biological ageing.

Trends in environmental chemical concentrations in the Canadian population: Biomonitoring data from the Canadian Health Measures Survey 2007-2017

Ten years of nationally representative biomonitoring data collected between 2007 and 2017 are available from the Canadian Health Measures Survey (CHMS). These data establish baseline environmental chemical concentrations in the general population. Here we sought to evaluate temporal trends in environmental chemical exposures in the Canadian population by quantifying changes in biomarker concentrations measured in the first five two-year cycles of the CHMS. We identified 39 chemicals that were measured in blood or urine in at least three cycles and had detection rates over 50% in the Canadian population. We calculated geometric mean concentrations for each cycle using the survey weights provided. We then conducted analyses of variance to test for linear trends over all cycles. We also calculated the percent difference in geometric means between the first and most recent cycle measured. Of the 39 chemicals examined, we found statistically significant trends across cycles for 21 chemicals. Trends were decreasing for 19 chemicals from diverse chemical groups, including metals and trace elements, phenols and parabens, organophosphate pesticides, per- and polyfluoroalkyl substances, and plasticizers. Significant reductions in chemical concentrations included di-2-ethylhexyl phthalate (DEHP; 75% decrease), perfluorooctane sulfate (PFOS; 61% decrease), perfluorooctanoic acid (PFOA; 58% decrease), dimethylphosphate (DMP; 40% decrease), lead (33% decrease), and bisphenol A (BPA; 32% decrease). Trends were increasing for two pyrethroid pesticide metabolites, including a 110% increase between 2007 and 2017 for 3-phenoxybenzoic acid (3-PBA). No significant trends were observed for the remaining 18 chemicals that included arsenic, mercury, fluoride, acrylamide, volatile organic compounds, and polycyclic aromatic hydrocarbons. National biomonitoring data indicate that concentrations, and therefore exposures, have decreased for many priority chemicals in the Canadian population. Concentrations for other chemical groups have not changed or have increased, although average concentrations remain below thresholds of concern derived from human exposure guidance values. Continued collection of national biomonitoring data is necessary to monitor trends in exposures over time.

Combined chemical exposure using exposure loads on human biomonitoring data of the 4th Flemish Environment and Health Study (FLEHS-4)

To improve our understanding of internal exposure to multiple chemicals, the concept exposure load (EL) was used on human biomonitoring (HBM) data of the 4th FLEHS (Flemish Environment and Health Study; 2016-2020). The investigated chemicals were per- and polyfluoroalkyl substances (PFASs), bisphenols, phthalates and alternative plasticizers, flame retardants, pesticides, toxic metals, organochlorine compounds and polycyclic aromatic hydrocarbons (PAHs). The EL calculates "the number of chemicals to which individuals are internally exposed above a predefined threshold". In this study, the 50th and 90th percentile of each of the 45 chemicals were applied as thresholds for the EL calculations for 387 study participants. Around 20% of the participants were exposed to >27 chemicals above the P50 and to >6 chemicals above the P90 level. This shows that participants can be internally exposed to multiple chemicals in relatively high concentrations. When the chemical composition of the EL was considered, the variability between individuals was driven by some chemicals more than others. The variability of the chemical profiles at high exposure loads (EL-P90) was somewhat dominated by e.g. organochlorine chemicals, PFASs, phthalates, PAHs, organophosphate flame retardants, bisphenols (A & F), pesticides, metals, but to a lesser extent by brominated flame retardants, the organophosphorus flame retardants TCIPP & TBOEP, naphthalene and benzene, bisphenols S, B & Z, the pesticide 2,4-D, the phthalate DEP and alternative plasticizer DINCH. Associations between the EL and exposure determinants suggested determinants formerly associated with fat soluble chemicals, PFASs, bisphenols, and PAHs. This information adds to the knowledge needed to reduce the exposure by policymakers and citizens. However, a more in depth study is necessary to explore in detail the causes for the higher EL in some individuals. Some limitations in the EL concept are that a binary number is used for exposure above or below a threshold, while toxicity and residence time in the body are not accounted for and the sequence of exposure in different life stages is unknown. However, EL is a first useful step to get more insight in multiple chemical exposure in higher exposed subpopulations (relative to the rest of the sampled population).

Developmental toxicity of endocrine-disrupting chemicals: Challenges and future directions

Maternal exposure to a mixture of various endocrine disruptors (EDCs) may have a substantial impact on postnatal health of her offspring(s) and increase the risk for health disorders and diseases in adulthood. Research efforts to better understand the health risk associated with endocrine disruptor exposures in early life have increased in recent decades. This paper provides a short overview of the current challenges that researchers continue to face in selecting appropriate epidemiologic methods and study designs to identify endocrine disruptors and evaluate their adverse health effects during this critical developmental window. Major challenges involve the selection of a representative biomarker that reflects the foetal internal dose of the biologically active chemical or its metabolite(s) that may be associated with adverse health effects with regard to variable level and duration of exposure and the latency between exposure and disorder/disease manifestation. Future studies should pay more attention to identifying factors that contribute to interindividual variability in susceptibility to various EDCs and other toxicants.