Cumulative Risk and Impact Modeling on Environmental Chemical and Social Stressors

Mapping Cumulative Risk in Delaware: Approach and Implications for Health Equity

BACKGROUND

Addressing health equity requires attention to upstream determinants of health, including environmental and social factors that act in tandem to increase communities' exposure to and vulnerability to toxicants. Cumulative risk assessment, which evaluates combined risks from environmental and social factors, is a useful approach for estimating potential drivers of health disparities. We developed a cumulative risk score of multiple indices of environmental and social conditions and assessed block group-level differences in New Castle County, Delaware.

METHODS

This cross-sectional study used choropleth maps to visualize the distribution of environmental, social, and cumulative risks and Moran's I statistics to assess spatial clustering of cumulative risk across the county and among individual block groups.

RESULTS

Findings indicate that environmental risk rarely occurs without social risk and that environmental and social risks co-occur in distinct areas, resulting in large-scale clustering of cumulative risk. Areas of higher cumulative risk had more Black residents and people of lower socioeconomic status.

CONCLUSIONS

Replicable measures of cumulative risk can show how environmental and social risks are inequitably distributed by race and socioeconomic status, as seen here in New Castle County. Such measures can support upstream approaches to reduce health disparities resulting from histories of environmental racism.

Cumulative Risk Evaluation of Phthalates Under TSCA

The U.S. Environmental Protection Agency (EPA) is currently conducting separate Toxic Substances Control Act (TSCA) risk evaluations for seven phthalates: dibutyl phthalate (DBP), butyl benzyl phthalate (BBP), di(2-ethylhexyl) phthalate (DEHP), diisobutyl phthalate (DIBP), dicyclohexyl phthalate (DCHP), di-isodecyl phthalate (DIDP), and diisononyl phthalate (DINP). Phthalates are highly abundant plastic additives used primarily to soften materials and make them flexible, and biomonitoring shows widespread human exposure to a mixture of phthalates. Evidence supports biological additivity of phthalate mixture exposures, including the enhancement of toxicity affecting common biological targets. Risk estimates based on individual phthalate exposure may not be protective of public health. Thus, a cumulative risk approach is warranted. While EPA initially did not signal that it would incorporate cumulative risk assessment (CRA) as part of its current risk evaluation for the seven phthalates, the agency recently announced that it is reconsidering if CRA for phthalates would be appropriate. Based on our review of existing chemical mixtures risk assessment guidance, current TSCA scoping documents for the seven phthalates, and pertinent peer-reviewed literature, we delineate a CRA approach that EPA can easily implement for phthalates. The strategy for using CRA to inform TSCA risk evaluation for existing chemicals is based upon integrative physiology and a common adverse health outcome algorithm for identifying and grouping relevant nonchemical and chemical stressors. We recommend adjustments for how hazard indices (HIs) or margins of exposure (MOEs) based on CRA are interpreted for determining "unreasonable risk" under TSCA.

Making the invisible visible: Using a qualitative system dynamics model to map disparities in cumulative environmental stressors and children's neurodevelopment

BACKGROUND

The combined effects of multiple environmental toxicants and social stressor exposures are widely recognized as important public health problems, likely contributing to health inequities. However, US policy makers at state and federal levels typically focus on one stressor exposure at a time and have failed to develop comprehensive strategies to reduce multiple co-occurring exposures, mitigate cumulative risks and prevent harm. This research aimed to move from considering disparate environmental stressors in isolation to mapping the links between environmental, economic, social and health outcomes as a dynamic complex system using children's exposure to neurodevelopmental toxicants as an illustrative example. Such a model can be used to support a broad range of child developmental and environmental health policy stakeholders in improving their understanding of cumulative effects of multiple chemical, physical, biological and social environmental stressors as a complex system through a collaborative learning process.

METHODS

We used system dynamics (SD) group model building to develop a qualitative causal theory linking multiple interacting streams of social stressors and environmental neurotoxicants impacting children's neurodevelopment. A 2 1/2-day interactive system dynamics workshop involving experts across multiple disciplines was convened to develop the model followed by qualitative survey on system insights.

RESULTS

The SD causal map covered seven interconnected themes: environmental exposures, social environment, health status, education, employment, housing and advocacy. Potential high leverage intervention points for reducing disparities in children's cumulative neurotoxicant exposures and effects were identified. Workshop participants developed deeper level of understanding about the complexity of cumulative environmental health risks, increased their agreement about underlying causes, and enhanced their capabilities for integrating diverse forms of knowledge about the complex multi-level problem of cumulative chemical and non-chemical exposures.

CONCLUSION

Group model building using SD can lead to important insights to into the sociological, policy, and institutional mechanisms through which disparities in cumulative impacts are transmitted, resisted, and understood.

Per- and polyfluoroalkyl substances and psychosocial stressors have a joint effect on adverse pregnancy outcomes in the Atlanta African American Maternal-Child cohort

BACKGROUND

African Americans (AAs) experience high rates of adverse pregnancy outcomes relative to Whites. Differential in utero exposure to environmental chemicals and psychosocial stressors may explain some of the observed health disparities, as exposures to per- and polyfluoroalkyl substances (PFAS) and experiences of discrimination have been linked to adverse birth outcomes. Few studies have examined chemicals and non-chemical stressors together as an exposure mixture, which may better reflect real-life exposure patterns. Here, we adapted methods designed for the analysis of exposure mixtures to examine joint effects of PFAS and psychosocial stress on birth outcomes among AAs.

METHODS

348 participants from the Atlanta African American Maternal-Child cohort were included in this study. Four PFAS were measured in first trimester serum samples. Self-report questionnaires were administered during the first trimester and were used to assess psychosocial stress (perceived stress, depression, anxiety, gendered racial stress). Quantile g-computation and Bayesian kernel machine regression (BKMR) were used to estimate the joint effects between PFAS and psychosocial stressors on gestational age at delivery and birthweight for gestational age z-scores. All models were adjusted for maternal education, maternal age, parity, and any alcohol, tobacco and marijuana use.

RESULTS

Our analytic sample included a socioeconomically diverse group of pregnant women, with 79 % receiving public health insurance. In quantile g-computation models, a simultaneous one-quartile increase in all PFAS, perceived stress, depression, anxiety, and gendered racial stress was associated with a reduction in birthweight z-scores (mean %change per quartile increase = -0.24, 95 % confidence interval = -0.43, -0.06). BKMR similarly showed that increasing all exposures in the mixture was associated with a modest decrease in birthweight z-scores, but not a reduced length of gestation.

DISCUSSION

Using methods designed for analyzing exposure mixtures, we found that a simultaneous increase in in utero PFAS and psychosocial stressors was associated with reduced birthweight for gestational age z-scores.

Exploring Environmental Health Inequalities: A Scientometric Analysis of Global Research Trends (1970-2020)

Environmental health inequalities (EHI), understood as differences in environmental health factors and in health outcomes caused by environmental conditions, are studied by a wide range of disciplines. This results in challenges to both synthesizing key knowledge domains of the field. This study aims to uncover the global research status and trends in EHI research, and to derive a conceptual framework for the underlying mechanisms of EHI. In total, 12,320 EHI publications were compiled from the Web of Science core collection from 1970 to 2020. Scientometric analysis was adopted to characterize the research activity, distribution, focus, and trends. Content analysis was conducted for the highlight work identified from network analysis. Keyword co-occurrence and cluster analysis were applied to identify the knowledge domain and develop the EHI framework. The results show that there has been a steady increase in numbers of EHI publications, active journals, and involved disciplines, countries, and institutions since the 2000s, with marked differences between countries in the number of published articles and active institutions. In the recent decade, environment-related disciplines have gained importance in addition to social and health sciences. This study proposes a framework to conceptualize the multi-facetted issues in EHI research referring to existing key concepts.

Longitudinal association of early childhood lead exposure and adolescent heart rate variability: influence of parental education

Lead exposure has been shown to dysregulate physiological stress responses. However, few studies have investigated the effect of lead exposure on later heart rate variability (HRV), an indicator of a stress response, in large samples of children. Furthermore, the interaction between social environmental factors and lead exposure in childhood, which commonly co-occur, remains understudied. This study examined relationships between childhood lead exposure and early adolescent physiological stress responses at different levels of parental education. Participants were 406 children from Jintan, China. Blood lead levels (BLLs) and parental education data were collected at 3-5 years of age, and HRV outcomes assessed at 12 years via frequency domain measures (LF/HF ratio) collected during an induced stress test. Results show a significant interaction between parental education and BLLs at 3-5 years. This relationship was found to be most consistent for the interaction between BLLs and mother's years of education for both the planning (β = 0.12, p = 0.046) and speaking (β = 0.11, p = 0.043) phase of the stress task, suggesting that increasing years of mother's education may enhance the deleterious influence of lead exposure on the HRV frequency measure, LF/HF ratio. This research highlights the complexity in lead exposure induced outcomes.

Defining the Exposome Using Popular Education and Concept Mapping With Communities in Atlanta, Georgia

Introduction

The exposome concept provides a framework to better incorporate the environment into the study of health and disease and has been defined by academics to encompass all lifetime exposures including toxicants, diet, and lifestyle choices. However, initial applications of the exposome concept have been less apt at measuring social determinants of health, focusing primarily on conventional environmental exposures and lifestyle choices that do not reflect the complex lived experience of many communities. To bring community voice into the exposome concept, the HERCULES Exposome Research Center and its Stakeholder Advisory Board co-developed the Exposome Roadshow. We present and discuss the resulting community-exposome definition to inform and improve exposome research.

Materials and Methods

Four communities from distinct areas across metro-Atlanta participated in separate 2-day Exposome Roadshow workshops with concept mapping. Aligned with a popular education approach in which community knowledge is used to work collectively for change, concept mapping provided a systematic method to collect and visualize community members' knowledge and create a shared understanding to take action. Community members brainstormed, sorted, and rated their responses to the prompt: "What in your environment is affecting your and your community's health?" Responses were analyzed and visually depicted by concept maps consisting of separate but interrelated clusters of ideas. Community members discussed and validated the maps, selecting a final map illustrating their community's exposome.

Results

A total of 118 community members completed concept mapping. On average communities identified 7 clusters to define their exposome. The resulting concept maps offer a community definition of the exposome. Five major themes arose across all four communities: conventional environmental concerns, built environment, social relationships, crime and safety, and individual health and behaviors.

Discussion

The resulting community-exposome definition demonstrates the importance of expanding the scope of exposures beyond traditional environmental influences to include the lived experience of individuals and communities. While newer exposome definitions align more closely with this community definition, traditional exposome methods do not routinely include these factors. To truly capture the totality of lifetime exposures and improve human health, researchers should incorporate community perspectives into exposome research.

The Interplay of Environmental Exposures and Mental Health: Setting an Agenda

BACKGROUND

To date, health-effects research on environmental stressors has rarely focused on behavioral and mental health outcomes. That lack of research is beginning to change. Science and policy experts in the environmental and behavioral health sciences are coming together to explore converging evidence on the relationship-harmful or beneficial-between environmental factors and mental health.

OBJECTIVES

To organize evidence and catalyze new findings, the National Academy of Sciences, Engineering, and Medicine (NASEM) hosted a workshop 2-3 February 2021 on the interplay of environmental exposures and mental health outcomes.

METHODS

This commentary provides a nonsystematic, expert-guided conceptual review and interdisciplinary perspective on the convergence of environmental and mental health, drawing from hypotheses, findings, and research gaps presented and discussed at the workshop. Featured is an overview of what is known about the intersection of the environment and mental health, focusing on the effects of neurotoxic pollutants, threats related to climate change, and the importance of health promoting environments, such as urban green spaces.

DISCUSSION

We describe what can be gained by bridging environmental and psychological research disciplines and present a synthesis of what is needed to advance interdisciplinary investigations. We also consider the implications of the current evidence for a) foundational knowledge of the etiology of mental health and illness, b) toxicant policy and regulation, c) definitions of climate adaptation and community resilience, d) interventions targeting marginalized communities, and e) the future of research training and funding. We include a call to action for environmental and mental health researchers, focusing on the environmental contributions to mental health to unlock primary prevention strategies at the population level and open equitable paths for preventing mental disorders and achieving optimal mental health for all. https://doi.org/10.1289/EHP9889.

Framing Environmental Health Decision-Making: The Struggle over Cumulative Impacts Policy

Little progress has been made to advance U.S. federal policy responses to growing scientific findings about cumulative environmental health impacts and risks, which also show that many low income and racial and ethnic minority populations bear a disproportionate share of multiple environmental burdens. Recent scholarship points to a “standard narrative” by which policy makers rationalize their slow efforts on environmental justice because of perceived lack of data and analytical tools. Using a social constructivist approach, ethnographic research methods, and content analysis, we examined the social context of policy challenges related to cumulative risks and impacts in the state of Maryland between 2014 and 2016. We identified three frames about cumulative impacts as a health issue through which conflicts over such policy reforms materialize and are sustained: (a) perceptions of evidence, (b) interpretations of social justice, and (c) expectations of authoritative bodies. Our findings illustrate that policy impasse over cumulative impacts is highly dependent on how policy-relevant actors come to frame issues around legislating cumulative impacts, rather than the “standard narrative” of external constraints. Frame analysis may provide us with more robust understandings of policy processes to address cumulative risks and impacts and the social forces that create health policy change.

Defining and Intervening on Cumulative Environmental Neurodevelopmental Risks: Introducing a Complex Systems Approach

BACKGROUND

The combined effects of multiple environmental toxicants and social stressor exposures are widely recognized as important public health problems contributing to health inequities. However cumulative environmental health risks and impacts have received little attention from U.S. policy makers at state and federal levels to develop comprehensive strategies to reduce these exposures, mitigate cumulative risks, and prevent harm. An area for which the inherent limitations of current approaches to cumulative environmental health risks are well illustrated is children's neurodevelopment, which exhibits dynamic complexity of multiple interdependent and causally linked factors and intergenerational effects.

OBJECTIVES

We delineate how a complex systems approach, specifically system dynamics, can address shortcomings in environmental health risk assessment regarding exposures to multiple chemical and nonchemical stressors and reshape associated public policies.

DISCUSSION

Systems modeling assists in the goal of solving problems by improving the "mental models" we use to make decisions, including regulatory and policy decisions. In the context of disparities in children's cumulative exposure to neurodevelopmental stressors, we describe potential policy insights about the structure and behavior of the system and the types of system dynamics modeling that would be appropriate, from visual depiction (i.e., informal maps) to formal quantitative simulation models. A systems dynamics framework provides not only a language but also a set of methodological tools that can more easily operationalize existing multidisciplinary scientific evidence and conceptual frameworks on cumulative risks. Thus, we can arrive at more accurate diagnostic tools for children's' environmental health inequities that take into consideration the broader social and economic environment in which children live, grow, play, and learn. https://doi.org/10.1289/EHP7333.

Association between county-level coal-fired power plant pollution and racial disparities in preterm births from 2000 to 2018

Coal has historically been a primary energy source in the United States. The byproducts of coal combustion, such as fine particulate matter (PM_2.5), have increasingly been associated with adverse birth outcomes. The goal of this study was to leverage the current progressive transition away from coal in the United States (U.S.) to assess whether coal PM_2.5 is associated with preterm birth rates and whether this association differs by maternal Black/White race/ethnicity. Using a novel dispersion modeling approach, we estimated PM_2.5 pollution from coal-fired power plants nationwide at the county-level during the study period (2000-2018). We also obtained county-level preterm birth rates for non-Hispanic White and non-Hispanic Black mothers. We used a generalized additive mixed model to estimate the relationship between coal PM_2.5 and preterm birth rates, overall and stratified by maternal race. We included a natural spline to allow for non-linearity in the concentration-response curve. We observed a positive non-linear relationship between coal PM_2.5 and preterm birth rate, which plateaued at higher levels of pollution. We also observed differential associations by maternal race; the association was stronger for White women, especially at higher levels of coal PM_2.5 (> 2.0 μg/m³). Our findings suggest that the transition away from coal may reduce preterm birth rates in the U.S.

Combined Impacts of Prenatal Environmental Exposures and Psychosocial Stress on Offspring Health: Air Pollution and Metals

PURPOSE OF REVIEW

Pregnant women and their offspring are vulnerable to the adverse effects of environmental and psychosocial stressors, individually and in combination. Here, we review the literature on how air pollution and metal exposures may interact with structural and individual-level stressors (including poverty and stressful life events) to impact perinatal and child outcomes.

RECENT FINDINGS

The adverse associations between air pollution and metal exposures and adverse infant and child health outcomes are often exacerbated by co-exposure to psychosocial stressors. Although studies vary by geography, study population, pollutants, stressors, and outcomes considered, the effects of environmental exposures and psychosocial stressors on early health outcomes are sometimes stronger when considered in combination than individually. Environmental and psychosocial stressors are often examined separately, even though their co-occurrence is widespread. The evidence that combined associations are often stronger raises critical issues around environmental justice and protection of vulnerable populations.

Assessing the relation of chemical and non-chemical stressors with risk-taking related behavior and adaptive individual attributes among adolescents living near the New Bedford Harbor Superfund site

BACKGROUND

Early life exposure to neurotoxicants and non-chemical psychosocial stressors can impede development of prefrontal cortical functions that promote behavioral regulation and thereby may predispose to adolescent risk-taking related behaviors (e.g., substance use or high-risk sexual activity). This is particularly concerning for communities exposed to multiple stressors.

METHODS

This study examined the relation of exposure to mixtures of chemical stressors, non-chemical psychosocial stressors, and other risk factors with neuropsychological correlates of risk-taking. Specifically, we assessed psychometric measures of both adverse behavioral regulation and adaptive attributes among adolescents (age ∼ 15 years) in the New Bedford Cohort (NBC), a sociodemographically diverse cohort of 788 children born 1993-1998 to mothers residing near the New Bedford Harbor Superfund site. The NBC includes biomarkers of prenatal exposure to organochlorines and metals; sociodemographic, parental and home characteristics; and periodic neurodevelopmental assessments. We modelled exposure mixtures using multi-dimensional smooths within generalized additive models.

RESULTS

Children of younger mothers with lower IQ who were exposed prenatally to higher polychlorinated biphenyls and lead had poorer anger control. This pattern was not apparent for children of older mothers with higher IQs. Direction of associations between increased hyperactivity and prenatal levels of organochlorine mixtures differed by maternal age and depression symptoms. Higher cord blood Pb levels, in conjunction with poorer HOME scores, were associated with poorer self-esteem when mothers had fewer depression symptoms.

CONCLUSIONS

Analyses suggest that prenatal chemical exposures and non-chemical factors interact to contribute to neuropsychological correlates of risk-taking behaviors in adolescence. By simultaneously considering multiple factors associated with adverse behavioral regulation, we identified potential high-risk combinations that reflect both chemical and psychosocial stressors amenable to intervention.

Development of a spatial web tool to identify hotspots of environmental burdens in Wallonia (Belgium)

In response to the Walloon Environment and Health Program, the Scientific Institute of Public Services (ISSeP) developed an integrated approach of environmental exposure assessment in the Walloon region, Belgium. The study presents an index-based approach to estimate the multiple environmental burdens at regional level and detailed local resolution. Indicators are based on environmental measurements of pollutants in ambient air and soil, and on stressors for citizens related to noise and radon. These indicators were mapped as proportions to obtain an accurate comparison between spatial units. In order to indicate the need for intervention, environmental indicators are calculated as the proportion of areas where the level of detrimental environmental factors exceeds threshold values from WHO guidelines and Walloon legal threshold values. In parallel, a spatial web tool based on GIS was developed to enable a flexible and weighted combination of the normalized indicators by computing the resulting composite index online. This interactive web tool designed for policy makers and experts eases the spatial analysis of results in order to identify geographic areas where hotspot exposures are a potential risk to human health. The next steps of this work aim to integrate more environmental indicators (stressors and benefits) and some sociodemographic and health indicators in order to detect vulnerable populations. A holistic assessment is essential to inform environmental justice debates and to ensure a health conducive equal environment. Finally, this environmental health tool will support decision makers focus resources and programs to improve the environmental health of Walloons living in areas disproportionately burdened by multiple sources of pollution.

A review of maternal prenatal exposures to environmental chemicals and psychosocial stressors-implications for research on perinatal outcomes in the ECHO program

Exposures to environmental chemicals and psychosocial stressors during pregnancy have been individually associated with adverse perinatal outcomes related to birthweight and gestational age, but are not often considered in combination. We review types of psychosocial stressors and instruments used to assess them and classes of environmental chemical exposures that are known to adversely impact perinatal outcomes, and identify studies relevant studies. We discuss the National Institutes of Health's Environmental influences on Child Health Outcomes (ECHO) program that has combined existing longitudinal cohorts that include more than 50,000 children across the U.S. We describe future opportunities for investigators to use this important new resource for addressing relevant and critical research questions to maternal health. Of the 84 cohorts in ECHO, 38 collected data on environmental chemicals and psychosocial stressors and perinatal outcomes. The diverse ECHO pregnancy cohorts provide capacity to compare regions with distinct place-based environmental and social stressors.

Joint Impact of Synthetic Chemical and Non-chemical Stressors on Children's Health

PURPOSE OF REVIEW

Pregnant women are exposed to numerous synthetic chemicals (e.g., pesticides, phthalates, polychlorinated biphenyls) in their daily lives as well as a range of non-chemical stressors, including poverty, depression, discrimination, and stressful life events. Although many studies have examined individual exposures to chemical and non-chemical stressors in relation to child health outcomes, very few studies have considered these exposures together. Here, we review the recent epidemiologic literature on the joint impact of chemical and non-chemical stressors on child outcomes.

RECENT FINDINGS

Considerable co-exposure to chemical and non-chemical stressors occurs in vulnerable populations. Non-chemical stressors may modify the impact of chemical exposures on children's health, typically exacerbating their negative impact, but associations differ considerably by the chemicals and populations of interest. Additional research is urgently needed to better understand the cumulative risks of multiple stressors on children's health and the underlying physiological mechanisms.

Data Science in Environmental Health Research

PURPOSE OF REVIEW

Data science is an exploding trans-disciplinary field that aims to harness the power of data to gain information or insights on researcher-defined topics of interest. In this paper we review how data science can help advance environmental health research.

RECENT FINDINGS

We discuss the concepts computationally scalable handling of Big Data and the design of efficient research data platforms, and how data science can provide solutions for methodological challenges in environmental health research, such as high-dimensional outcomes and exposures, and prediction models. Finally, we discuss tools for reproducible research.

SUMMARY

In this paper we present opportunities to improve environmental research capabilities by embracing data science, and the pitfalls that environmental health researchers should avoid when employing data scientific approaches. Throughout the paper, we emphasize the need for environmental health researchers to collaborate more closely with biostatisticians and data scientists to ensure robust and interpretable results.

Cumulative Impact of Environmental Pollution and Population Vulnerability on Pediatric Asthma Hospitalizations: A Multilevel Analysis of CalEnviroScreen

The CalEnviroScreen created by the Office of Environmental Health Hazard Assessment, Sacramento, USA, is a place-based dataset developed to measure environmental and social indicators that are theorized to have cumulative health impacts on populations. The objective of this study was to examine the extent to which the composite scores of the CalEnviroScreen tool are associated with pediatric asthma hospitalization. This was a retrospective analysis of California hospital discharge data from 2010 to 2012. Children who were hospitalized for asthma-related conditions, were aged 0–14 years, and resided in California were included in analysis. Rates of hospitalization for asthma-related conditions among children residing in California were calculated. Poisson multilevel modeling was used to account for individual- and neighborhood-level risk factors. Every unit increase in the CalEnviroScreen Score was associated with an increase of 1.6% above the mean rate of pediatric asthma hospitalizations (rate ratio (RR) = 1.016, 95% confidence interval (CI) = 1.014–1.018). Every unit increase in racial/ethnic segregation and diesel particulate matter was associated with an increase of 1.1% and 0.2% above the mean rate of pediatric asthma, respectively (RR = 1.011, 95% CI = 1.010–1.013; RR = 1.002, 95% CI = 1.001–1.004). The CalEnviroScreen is a unique tool that combines socioecological factors and environmental indicators to identify vulnerable communities with major health disparities, including pediatric asthma hospital use. Future research should identify mediating factors that contribute to community-level health disparities.

Urinary levels of 1-hydroxypyrene and health risk assessment in children living in Mexican communities with a high risk of contamination by polycyclic aromatic hydrocarbons (PAHs)

Health complications have been associated with polycyclic aromatic hydrocarbons (PAHs) exposure, a widespread environmental pollutants family. Therefore, the objective of this investigation was to develop a probabilistic health risk evaluation (using Monte-Carlo simulation) in an infantile population living in areas with a high risk of pollution by PAHs (indoor wood combustion, brick kiln industry, municipal landfill, and low and high vehicular traffic) in Mexico. Urine samples were obtained from Mexican children (n = 135) and urinary 1-OHP concentrations (used as a PAHs biomarker) were quantified. Highest urinary 1-OHP concentrations were detected in children living in areas that use wood combustion as the principal indoor fuel (3.50 ± 0.95 µg/L). Nevertheless, estimated hazard quotients (HQ) lower than 1 were found in all assessed sites after Monte-Carlo analysis. Although HQ <1.0 (a toxic effect is not expected), more data are necessary to determine the real impact of PAHs exposure on children health status.

Complex Mixtures, Complex Analyses: an Emphasis on Interpretable Results

PURPOSE OF REVIEW

The purpose of this review is to outline the main questions in environmental mixtures research and provide a non-technical explanation of novel or advanced methods to answer these questions.

RECENT FINDINGS

Machine learning techniques are now being incorporated into environmental mixture research to overcome issues with traditional methods. Though some methods perform well on specific tasks, no method consistently outperforms all others in complex mixture analyses, largely because different methods were developed to answer different research questions. We discuss four main questions in environmental mixtures research: (1) Are there specific exposure patterns in the study population? (2) Which are the toxic agents in the mixture? (3) Are mixture members acting synergistically? And, (4) what is the overall effect of the mixture? We emphasize the importance of robust methods and interpretable results over predictive accuracy. We encourage collaboration with computer scientists, data scientists, and biostatisticians in future mixture method development.