Article

Something From “Nothing”-Eight Weak Estrogenic Chemicals Combined at Concentrations Below NOECs Produce Significant Mixture Effects

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Abstract

We tested whether multicomponent mixtures of xenoestrogens would produce significant effects when each component was combined at concentrations below its individual NOEC or EC01 level. The estrogenic effects of eight chemicals of environmental relevance, including hydroxylated PCBs, benzophenones, parabenes, bisphenol A, and genistein, were recorded using a recombinant yeast estrogen screen (YES). To ensure that no chemical contributed disproportionately to the overall combination effect, a mixture was prepared at a mixture ratio proportional to the potency of each individual component. The performance of four approaches for the calculation of additive combination effects (concentration addition, toxicity equivalency factors, effect summation, and independent action) was compared. Experimental testing of the predictions revealed that concentration addition and its application, the toxicity equivalency factor approach, were valid methods for the calculation of additive mixture effects. There was excellent agreement between prediction and observation. In contrast, independent action and effect summation led to clear underestimations of the experimentally observed responses. Crucially, there were substantial mixture effects even though each chemical was present at levels well below its NOEC and EC01. We conclude that estrogenic agents are able to act together to produce significant effects when combined at concentrations below their NOECs. Our results highlight the limitations of the traditional focus on the effects of single agents. Hazard assessments that ignore the possibility of joint action of estrogenic chemicals will almost certainly lead to significant underestimations of risk.

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... Moreover, the health effects mixtures of coexisting AMBs may be totally different from the individual effects. MBs are chemicals, and different chemicals have different toxic thresholds and toxicokinetic and functional pathways in causing health effects (Liu et al., 2021;Kortenkamp, 2007;Silva et al., 2002). For example, a mixture of eight estrogenic chemicals was found to have significant synergistic effects that were much higher than the individual effects (Silva et al., 2002). ...
... MBs are chemicals, and different chemicals have different toxic thresholds and toxicokinetic and functional pathways in causing health effects (Liu et al., 2021;Kortenkamp, 2007;Silva et al., 2002). For example, a mixture of eight estrogenic chemicals was found to have significant synergistic effects that were much higher than the individual effects (Silva et al., 2002). In addition, the complexity of coexisting chemicals such as various MBs and PAHs in air particles raises concerns about potential health risks upon exposure to a cocktail of chemical components in aerosol particles. ...
... In addition to the target AMBs investigated in this work, other MBs might be present in airborne particles, but information on their types, abundances, distribution patterns and health effects is still lacking. From a chemical perspective, different groups of MBs (e.g., NSP, DSP, and PSP toxins) could differ in their toxic mode of action that causes health effects via inhalation exposure (Kortenkamp, 2007;Liu et al., 2021;Silva et al., 2002). Most previous studies that aimed to reveal the relationships between coastal air particle exposure and adverse health effects focused on the health effects of PM itself and ignored the roles of PM 10 -associated MBs (or other types of chemicals) during risk evaluations. ...
Article
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Characterizing marine biotoxins (MBs) composition in coastal aerosol particles has become essential to tracking sources of atmospheric contaminants and assessing human inhalable exposure risks to air particles. Here, coastal aerosol particles were collected over an almost 3-year period for the analysis of eight representative MBs, including brevetoxin (BTX), okadaic acid (OA), pectenotoxin-2 (PTX-2), domoic acid (DA), tetrodotoxin (TTX), saxitoxin (STX), ciguatoxin (CTX) and ω-Conotoxin. Our data showed that the levels of inhalable airborne marine biotoxins (AMBs) varied greatly among the subcategories and over time. Both in daytime and nighttime, a predominance of coarse-mode AMB particles was found for all the target AMBs. Based on the experimental data, we speculate that an ambient AMB might have multiple sources/production pathways, which include air-sea aerosol production and direct generation and release from toxigenic microalgae/bacteria suspended in surface seawater or air, and different sources may make different contribution. Regardless of the subcategory, the highest deposition efficiency of an individual AMB was found in the head airway region, followed by the alveolar and tracheobronchial regions. This study provides new information about inhalable MBs in the coastal atmosphere. The coexistence of various particle-bound MBs raises concerns about potential health risks from exposure to coastal air particles.
... To our knowledge, no country or region in other parts of the world considers the risk due to simultaneous pesticide mixtures in the environment within the authorisation or risk mitigation of PPPs. This is problematic following the widely acknowledged assumption that exposure to multiple pesticides as a consequence of intensive PPP use represents a major disregarded ecological risk and a contribution to the biodiversity decline (Backhaus and Faust, 2012;Brühl and Zaller, 2019;Hayes et al., 2006;Silva et al., 2002). This assumption is often supported by studies testing equitoxic mixtures, in which all components contribute equally to the toxicity of the mixture based on a consistent measurement endpoint Backhaus et al., 2000;Silva et al., 2002). ...
... This is problematic following the widely acknowledged assumption that exposure to multiple pesticides as a consequence of intensive PPP use represents a major disregarded ecological risk and a contribution to the biodiversity decline (Backhaus and Faust, 2012;Brühl and Zaller, 2019;Hayes et al., 2006;Silva et al., 2002). This assumption is often supported by studies testing equitoxic mixtures, in which all components contribute equally to the toxicity of the mixture based on a consistent measurement endpoint Backhaus et al., 2000;Silva et al., 2002). Especially under such conditions, the combined effect of the mixture significantly exceeds respective single substance effects. ...
... The dominance of single pesticides in the monitored PPP applications implies similar conditions in agricultural fields. This marks a departure from the many studies investigating the effect of mixtures, in which the individual components equally contribute to mixture risk Backhaus et al., 2000;Silva et al., 2002). Assessing the risk of these equitoxic mixtures proved the combined effect of mixture components in principle, but does not reflect the observed toxic imbalance of components in the environment and thus overrates pesticide mixture relevance. ...
Article
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Pesticide applications in agricultural crops often comprise a mixture of plant protection products (PPP), and single fields face multiple applications per year leading to complex pesticide mixtures in the environment. Restricted to single PPP, the current European Union PPP regulation, however, disregards the ecological risks of pesticide mixtures. To quantify this additional risk, we evaluated the contribution of single pesticide active ingredients to the additive mixture risk for aquatic risk indicators (invertebrates and algae) in 464 different PPP used, 3446 applications sprayed and 830 water samples collected in Central Europe, Germany. We identified an average number of 1.3 different pesticides in a single PPP, 3.1 for complete applications often involving multiple PPP and 30 in stream water samples. Under realistic worst-case conditions, the estimated stream water pesticide risk based on additive effects was 3.2 times higher than predicted from single PPP. We found that in streams, however, the majority of regulatory threshold exceedances was caused by single pesticides alone (69% for algae, 81% for invertebrates). Both in PPP applications and in stream samples, pesticide exposure occurred in repeated pulses each driven by one to few alternating pesticides. The time intervals between pulses were shorter than the 8 weeks considered for ecological recovery in environmental risk assessment in 88% of spray series and 53% of streams. We conclude that pesticide risk assessment should consider an additional assessment factor to account for the additive, but also potential synergistic simultaneous pesticide mixture risk. Additionally, future research and risk assessment need to address the risk from the frequent sequential pesticide exposure observed in this study.
... As a consequence of this global contamination, the simultaneous exposure to a multitude of chemicals has become almost unavoidable for the general population, and made even more complex the understanding of exposure-induced adverse effects on health. Indeed, an increasing number of studies demonstrated that multiple chemical exposure can lead to different or stronger effects than exposure to each chemical separately, and point out the need of novel approaches allowing more comprehensive exposure assessment (Carlin et al. 2013;Kortenkamp 2014;Silva et al. 2002;Sarigiannis and Hansen 2012;Kostoff et al. 2018;Docea et al. 2019;Tsatsakis et al. 2017). ...
... Many studies demonstrated that synergies between several pollutants might lead to different effects than each pollutant separately. For instance, Silva et al. (2002) demonstrated on yeast cell culture that a mixture of 8 contaminants (including organochlorines and bisphenol A) displayed estrogenic activity 20 times higher than the summed effect of each chemical alone at equivalent concentration. In another study conducted on mussels, Song et al. (2016) demonstrated that combination of benzo(a)pyrene (polycyclic aromatic hydrocarbon) and dichlorodiphenyltrichloroethane (DDT, organochlorine pesticide)-induced dysregulation of proteins involved in gills' osmotic regulation and gonad metabolism, which were not affected when each chemical was alone. ...
... Mixtures can therefore induce adverse effects that were not observed, or only observed at higher level of exposure, with individual pollutants (Silva et al. 2002;Song et al. 2016;Starr et al. 2012;Shukla et al. 2017;Christen et al. 2014;Kortenkamp 2007;Orton et al. 2014). Consequently, the "safe" level of exposure established for a specific pollutant could actually lead to adverse effects due to co-exposure to other chemicals, and should be re-evaluated accordingly by regulatory agencies, who besides highlighted the need of methodologies allowing for the analysis of multiple pollutants simultaneously (Carlin et al. 2013;Kortenkamp 2014;Kostoff et al. 2018). ...
Article
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Awareness of the adverse effects of exposure to pollutant mixtures, possibly much more severe than individual chemicals, has drawn attention towards the necessity of using multi-residue methods to obtain the most possible comprehensive information on exposome. Among the different biological matrices used for exposure assessment, hair enables to detect the largest number of chemicals, including many classes such as persistent pollutants, hydrophilic metabolites and metals. Most biomonitoring studies are however focused on a limited number of pollutants and only give a partial information on exposure. Combining several multi-residue methods, the present study aimed at assessing the exposure of a population to an extensive variety of chemicals by hair analysis. One hair sample was collected from each participant (55 children and 134 adults). Samples were analysed with three different multi-residue methods, targeting, respectively, 152 organic pollutants (pesticides, PCBs, bisphenols, PBDEs), 62 polycyclic aromatic hydrocarbons (PAHs) and metabolites, nicotine and cotinine and 36 metals. From 33 to 70 organic chemicals were detected in each child’s hair sample, and from 34 up to 74 in adults. From 7 to 26 PAH were detected per child, and 7 to 21 in adults. Twenty-three to 27 metals were detected per child and 21 to 28 per adult. The highest median concentration were observed for zinc (143 μg /mg in children; 164 μg /mg in adults), bisphenol A (95.9 pg/mg in children; 64.7 pg/mg in adults) and nicotine (66.4 pg/mg in children; 51.9 pg/mg in adults). The present study provides the most comprehensive exposure assessment ever and highlights the simultaneous exposure to multiple classes of pollutants in the general population. The results support the use of multi-residue methods for future studies on exposure-associated effects, to document exposome and better consider the effect of chemical mixtures.
... This becomes even more a challenge, if the effects of environmental mixtures in bioassays cannot be explained comprehensively by the targeted chemical analysis(Neale et al., 2015). Therefore, EBM is important to assess the intrinsic toxicity of a sample including all chemicals which are unknown or occurring at concentrations below the detection limits of the chemical analytical instruments.Known and unknown chemicals and compounds may cause and or contribute to effects even at these low concentrations such as steroids and by joint effects of even dissimilar acting compounds(Kortenkamp et al., 2019;Brack et al., 2019;Silva et al., 2002). ...
... These approaches do not account for risks of chemical mixtures (Faust et al., 2019) or site-specific pollution(Krauss et al., 2019). The single substance monitoring and assessment strategy of the WFD is not sufficient and protective for the water quality, because a complex chemical mixture poses a higher risk than any individual compounds alone due to mixture toxicity effects and this risk scenario can be very site-specific(Silva et al., 2002; Faust et al., 2019; Kortenkamp et al., 2019; Carvalho et al., 2014;Brack, 2019; Krauss et al., 2019). Thus, one of the goals of the Joint Danube Survey 4 (JDS4) was the verification of the use of alternative methods for pollutant analysis with the view of a better effort-cost-benefit relation than the present monitoring strategy under the WFD.35 COMPARISON OF NOVEL AND CURRENT APPROACHES FOR THE TARGET-AND NON-TARGET SCREENING, EFFECT-BASED MONITORING AND PRIORITISATION OF RIVER BASIN SPECIFIC POLLUTANTS TO IMPROVE FUTURE WATER … ...
Chapter
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Phytobenthos samples were collected at 69 sites during JDS4. Whenever possible, samples were obtained from both riverbanks and analysed by DNA metabarcoding with two markers, 18SV4 and rbcL. The genera with the most Sequence Units were Nitzschia, Navicula, Sellaphora and Amphora. The most abundant species were Navicula cf. ramosissima, N. tripunctata and Melosira varians. Community composition shows only a weak longitudinal pattern when sorted by reach or river typology, but correlated well with temperature, dissolved oxygen, total organic carbon and conductivity. In several cases, communities obtained from the right and left riverbank at a given JDS4 site were quite different. In conclusion, although DNA metabarcoding identified less taxa at species level than classical light microscopy during JDS4 because of gaps in barcode reference libraries, the unassigned and hidden diversity present in the DNA-based datasets (i.e. intraspecific genetic diversity or morphologically cryptic lineages) help to better understand the impact of environmental variables and to describe community composition. So far, the metabarcoding approach was able to reveal 78% of all the most abundant diatom species identified in JDS2, 3 and 4, as well as six of the seven dominant taxa identified by light microscopy in JDS4. However, more complete reference databases and adjusted sampling designs will allow higher proportions of species-level matches in the future. http://www.danubesurvey.org/jds4/publications/scientific-report
... Based on the metabolite level only, one might conclude on a "something-fromnothing" scenario, i.e., that compounds which did not show effects alone produced a marked effect when administered as a mixture. It has been shown that a mixture of similarly-acting estrogenic chemicals, each dosed below its individual effect level, can exert a significant mixture effect which follows the CA concept (Silva et al., 2002). Moreover, a recent study demonstrates effects of a mixture of pesticides and phthalates on reproductive tract formation in male rats, with the individual test compounds dosed below their individual no-observed adverse effect levels (Conley et al., 2021). ...
... Furthermore, CA is preferably used if compounds in a mixture have the same mode of action, whereas IA assumes that the single compounds in a mixture act independently (Bliss, 1939;Loewe and Muischnek, 1926). Accordingly, Silva and colleagues have shown that CA is more appropriate than other models to evaluate the effect of a complex mixture of estrogenic compounds (Silva et al., 2002). (Backhaus et al., 2000) also stated in their study with similarly acting compounds that CA showed better predictions than IA when analyzing the toxicity of a mixture of quinolones. ...
Article
In real life, organisms are exposed to complex mixtures of chemicals at low concentration levels, whereas research on toxicological effects is mostly focused on single compounds at comparably high doses. Mixture effects deviating from the assumption of additivity, especially synergistic effects, are of concern. In an adverse outcome pathway (AOP)-guided manner, we analyzed the accumulation of triglycerides in human HepaRG liver cells by a mixture of eight steatotic chemicals (amiodarone, benzoic acid, cyproconazole, flusilazole, imazalil, prochloraz, propiconazole and tebuconazole), each present below its individual effect concentration at 1–3 µM. Pronounced and significantly enhanced triglyceride accumulation was observed with the mixture, and similar effects were seen at the level of pregnane-X-receptor activation, a molecular initiating event leading to hepatic steatosis. Transcript pattern analysis indicated subtle pro-steatotic changes at low compound concentrations, which did not exert measurable effects on cellular triglycerides. Mathematical modeling of mixture effects indicated potentially more than additive behavior using a model for compounds with similar modes of action. The present data underline the usefulness of AOP-guided in vitro testing for the identification of mixture effects and highlight the need for further research on chemical mixtures and harmonization of data interpretation of mixture effects.
... More recently, Thrupp et al. (2018) observed mixture toxicity effects on fish egg production, even though concentrations of the substances tested (i.e., five synthetic steroidal pharmaceuticals) were well below their NOEC values. This observation has been defined by some as the "something from nothing" phenomenon, where two (or more) substances, who individually were judged harmless, cause significant effects when dosed simultaneously (Silva et al., 2002). Along those lines there is a concern towards enhanced effects, where the observed mixture effect is larger than the sum of the effects of the individual substances. ...
... Synergisms can happen when chemicals in a mixture interact and enhance each other's toxicity. One related phenomenon is so-called "something from nothing", where two chemicals are seemingly harmless individually, but when dosed together in a mixture they lead to significant effects (Silva et al., 2002). Synergism of mixtures raises the question whether we should be concerned about these chemical interactions: ...
Thesis
Anthropogenic chemicals are essential for modern society, but many of these man-made chemicals enter the environment one way or another. For the last 10 years, the chemical industry in Europe has doubled in production and is expected to double again in the next 10 years. Ecological risk assessment aims to estimate the concentration of harmful substances in the environment and the associated effects on the ecosystem. Based on the estimated concentrations and the predicted effects, potential risks for adverse effects to the environment are identified. Effect assessment nowadays is performed using standardized toxicity tests, with individual organisms, exposed to single substances, in strictly controlled laboratory conditions. However, the environment is complex, as we have individuals living together in populations, exposed to mixtures of chemical substances, under varying environmental conditions. Mechanistic effect models have gained increasing interest from the scientific community, as they can extrapolate effects across biological levels, i.e., from sub-organismal to the population or community level. Yet, applications of mechanistic effect models for mixture toxicity in a population context are limited. The aim of the current thesis is to demonstrate the use of mechanistic models to predict population-level effects of mixtures. Focus is on the freshwater crustacean Daphnia magna (the water flea), two metals (copper and zinc), and four organic priority substances listed under the Water Framework Directive (pyrene, dicofol, alfa-hexachlorocyclohexane, and endosulfan). A generic individual-based model (IBM) implementation of the dynamic energy budget (DEB) theory was used to predict mixture toxicity effects to D. magna populations. Toxic stress was predicted using DEB-TKTD (extension of DEB including toxicokinetic-toxicodynamic processes) for sub-lethal effects and GUTS-RED-SD (reduced version of the general unified threshold model for survival assuming stochastic death) for lethal effects. A mixture toxicity implementation was developed, based on the general statistical models for mixture toxicity used in risk assessment. Two mixture toxicity approaches in mechanistic effect models can be considered: independent action or damage addition. In a first case (Chapter 2), we extrapolate effects observed at the individual level to relevant population-level effects of mixtures. The model was applied for mixtures of copper and zinc. The DEB- TKTD and GUTS sub-models were calibrated based on data from a standard 21-day chronic reproduction test (endpoints: growth, reproduction, and survival over time). A population experiment with mixtures of copper and zinc was performed. The DEB-IBM, assuming independent action for mixture toxicity, was able to reproduce the effects observed in the population experiment. Using the DEB-IBM, the observed trends were explained. The absence of zinc effects was explained through population-level compensation mechanisms. The increased mortality due to zinc is compensated by a decrease in starvation-related mortality. For copper, the switch from copper-induced mortality to starvation-related mortality explained the recovery over time observed in the experiment. Based on standard toxicity data at the individual level, mixture toxicity effects at the population were predicted. Based on the DEB-TKTD theoretical model, we hypothesize that combinations of physiological modes of action (PMoAs) in DEB-TKTD can lead to diverging effects at the population level. As a matter of fact, the PMoA will determine how the energy from food is redistributed within the population under chemical stress. We used DEB-IBM to design a population experiment, testing specific combinations of substances based on their inferred PMoAs (Chapter 3). We tested combinations of four organic substances: pyrene, dicofol, alfa-hexachlorocyclohexane (α-HCH), and endosulfan. An independent validation of mixture toxicity effects at the population level was performed with blind predictions, calibrated on individual-level effects of single substances only. Strong correlation was found between data and predictions during the constant exposed phase, the recovery phase after, and the pulsed acute phase. However, the recovery after the acute phase was not well predicted, meaning the model is unreliable in situations with high lethality. Overall, the independent action approach correctly predicted the observed mixture effects in the population experiment. The damage addition model was tested for the HCH-endosulfan mixture, but overpredicted the effects. Interestingly, synergisms (compared to statistical independent action) were observed in the population experiment that were correctly predicted by the DEB-IBM. We initially hypothesized that increased or decreased effects can occur due to the linking of DEB energy flows within the population. Overall, DEB-IBM was better in predicting mixture toxicity at the population level than current statistical models used in risk assessment. The two cases have shown the validity and relevance of mechanistic population models for mixture toxicity risk assessment. Application of these models for regulatory risk assessment is currently limited. We envision applications of mechanistic population models in current European regulations that encompass the risk assessment of chemicals, such as REACH, PPP, and BPR (Chapter 4). In this chapter, three example applications are highlighted. In a first example, mechanistic population models are used as predictive tools for the risk assessment of chemicals. Look-up tables and flowcharts were developed. A second example discusses the use of DEB-IBM as refinement tool for laboratory-to-field extrapolations. The effect of food density in combination with lethal and and sub-lethal effects to D. magna populations was investigated. As final example, DEB-IBM was linked to FOCUS (a dedicated exposure model that predicts the fate of pesticides in the environment) to predicted realistic effects of pesticide mixtures to D. magna populations. A realistic example was developed with a water body contaminated with endosulfan and funguren (a copper pesticide) due to pesticide application on nearby fields. The predicted surface water concentrations from FOCUS were linked with DEB-IBM. In addition, the DEB-IBM predictions were compared to a traditional dose-response curve analysis and predictions with a TKTD model. Good model documentation and accessibility is required to increase model transparency and reliability. An extensive description of the model, following the TRACE (transparent and comprehensive model ‘evaludation’) documentation, is provided (Appendix E). We conclude that mechanistic population models can be used for prospective and predictive risk assessment of chemical mixtures. More so than predicting effects, mechanistic population models can also give information and understanding of the driving forces of mixture toxicity within a population context. However, there is still a lack of guidance on the ‘standardized’ use of these models. More applications and communication of results would help increase acceptance of mechanistic population models for regulatory risk assessment. With this thesis we have shown that mechanistic population models can bridge multiple uncertainty gaps that were previously unaddressed in ecological risk assessment: the divide between individuals and populations, between single substances and mixtures of substances, and between constant controlled exposure conditions and dynamic exposure conditions.
... Human development during the prenatal period is an intricately ordered and tightly regulated process [1][2][3], and perturbation of maternal physiology during pregnancy by exposure to environmental chemicals can adversely affect maternal health and fetal development [4][5][6]. Of particular concern are cumulative or joint effects of chemical exposures, as multiple chemicals can act upon common physiological processes in additive or synergistic fashions [7][8][9]. Metabolomics, the study of the totality of small molecules within an organism or biological media [10][11][12], is an emerging and promising method to investigate the influence of chemical exposures [13][14][15][16], including their joint impacts on maternal health during pregnancy and subsequent development. Epidemiologic studies of metabolites or metabolic pathways affected by chemical exposures may elucidate toxicological mechanisms, indicate potential downstream effects of exposure, identify novel biomarkers of exposure, and lead to potential targets for intervention. ...
... However, these silicone samplers enabled measurement of a diverse set of chemicals in a non-invasive and minimally burdensome manner. Importantly, this broad exposure assessment supported the investigation of chemical exposures, which better approximate real world exposures and potential additive or synergistic effects [7][8][9]. Relatedly, although most correlations observed among the chemicals surveyed were weak to moderate, stronger correlations (ρ > 0.40) were observed among phthalates, lilial, tonalide, and other chemicals commonly found in fragrances. Phthalates are commonly used as scent retainers in products containing fragrance [46,47], and benzyl salicylate, ethylene brassylate, galaxolide, lilial, and tonalide are synthetic musk and scent chemicals [48,49]. ...
Article
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Metabolomics is a promising method to investigate physiological effects of chemical exposures during pregnancy, with the potential to clarify toxicological mechanisms, suggest sensitive endpoints, and identify novel biomarkers of exposures. Investigate the influence of chemical exposures on the maternal plasma metabolome during pregnancy. Data were obtained from participants (n = 177) in the New Hampshire Birth Cohort Study, a prospective pregnancy cohort. Chemical exposures were assessed via silicone wristbands worn for one week at ~13 gestational weeks. Metabolomic features were assessed in plasma samples obtained at ~24–28 gestational weeks via the Biocrates AbsoluteIDQ® p180 kit and nuclear magnetic resonance (NMR) spectroscopy. Associations between chemical exposures and plasma metabolomics were investigated using multivariate modeling. Chemical exposures predicted 11 (of 226) and 23 (of 125) metabolomic features in Biocrates and NMR, respectively. The joint chemical exposures did not significantly predict pathway enrichment, though some individual chemicals were associated with certain amino acids and related metabolic pathways. For example, N,N-diethyl-m-toluamide was associated with the amino acids glycine, L-glutamic acid, L-asparagine, and L-aspartic acid and enrichment of the ammonia recycling pathway. This study contributes evidence to the potential effects of chemical exposures during pregnancy upon the endogenous maternal plasma metabolome.
... After separation (Figure 2, B2), the individual concentrations or potencies may be too low for a measurable effect. 30 The fractionated dust extract showed 28 bioactive fractions in the TTR-binding assay (Figure 2, C2) and the fractionated serum extract contained six bioactive fractions (Figure 2, D2). A response was observed in each bioassay of the unfractionated extract at the highest tested enrichment factor (Figure 2). ...
Article
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Effect-directed analysis (EDA) aims at the detection of bioactive chemicals of emerging concern (CECs) by combining toxicity testing and high-resolution mass spectrometry (HRMS). However, consolidation of toxicological and chemical analysis techniques to identify bioactive CECs remains challenging and laborious. In this study, we incorporate state-of-the-art identification approaches in EDA and propose a robust workflow for the high-throughput screening of CECs in environmental and human samples. Three different sample types were extracted and chemically analyzed using a single high-performance liquid chromatography HRMS method. Chemical features were annotated by suspect screening with several reference databases. Annotation quality was assessed using an automated scoring system. In parallel, the extracts were fractionated into 80 micro-fractions each covering a couple of seconds from the chromatogram run and tested for bioactivity in two bioassays. The EDA workflow prioritized and identified chemical features related to bioactive fractions with varying levels of confidence. Confidence levels were improved with the in silico software tools MetFrag and the retention time indices platform. The toxicological and chemical data quality was comparable between the use of single and multiple technical replicates. The proposed workflow incorporating EDA for feature prioritization in suspect and nontarget screening paves the way for the routine identification of CECs in a high-throughput manner.
... This approach may provide new opportunities and advances in our understanding of the testicular metabolic pathways and how they can be manipulated at the clinical level. It is well established that exposure to multiple EDCs can result in metabolic disturbances at concentrations for which no effect is observed when exposure occurs individually [73,74]. This cocktail effect remains one of the greatest challenges to be addressed in the future. ...
Article
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The permanent exposure to environmental contaminants promoting weight gain (i.e., obesogens) has raised serious health concerns. Evidence suggests that obesogens are one of the leading causes of the marked decline in male fertility and are key players in shaping future health outcomes, not only for those who are directly exposed to them, but also for upcoming generations. It has been hypothesized that obesogens affect male fertility. By using an interdisciplinary strategy, combining in silico, in vitro, in vivo and epidemiological findings, this review aims to contribute to the biological understanding of the molecular transformations induced by obesogens that are the basis of male infertility. Such understanding is shaped by the use of Adverse Outcomes Pathways, a new approach that may shift the paradigm of reproductive toxicology, contributing to the improvement of the diagnosis and management of the adverse effects of obesogens in male fertility.
... Our focus herein is focusing on the third question regarding cumulative exposures to multiple agents. It is in line with the concept of a mixture effect from the toxicology literature where relevant environmental exposures may result in the phenomenon of "something from nothing" [34]. Environmental chemicals may be at exposures well below an effect level, but joint action of the components may produce significant effects. ...
Article
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Environmental exposures to a myriad of chemicals are associated with adverse health effects in humans, while good nutrition is associated with improved health. Single chemical in vivo and in vitro studies demonstrate causal links between the chemicals and outcomes, but such studies do not represent human exposure to environmental mixtures. One way of summarizing the effect of the joint action of chemical mixtures is through an empirically weighted index using weighted quantile sum (WQS) regression. My Nutrition Index (MNI) is a metric of overall dietary nutrition based on guideline values, including for pregnant women. Our objective is to demonstrate the use of an index as a metric for more causally linking human exposure to health outcomes using observational data. We use both a WQS index of 26 endocrine-disrupting chemicals (EDCs) and MNI using data from the SELMA pregnancy cohort to conduct causal inference using g-computation with counterfactuals for assumed either reduced prenatal EDC exposures or improved prenatal nutrition. Reducing the EDC exposure using the WQS index as a metric or improving dietary nutrition using MNI as a metric, the counterfactuals in a causal inference with one SD change indicate significant improvement in cognitive function. Evaluation of such a strategy may support decision makers for risk management of EDCs and individual choices for improving dietary nutrition.
... The cumulative risk assessment of some insecticides with the same action mechanism was proven to result in additive, synergistic, or other mixed effects to human health [18]. Many studies showed that multichemical mixtures had significant toxic effects, even if the concentrations of individual chemicals were below their no-observed-effect concentrations [19,20]. Compared with single insecticide application, mixtures of IMI, clothianidin, and TMX had directly additive effects [21]. ...
Article
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Multiple insecticides’ residues after the mixed application of several neonicotinoids cause combined pollution and bring new challenges to food safety and pest control during agricultural production. In this study, three neonicotinoid insecticides, namely imidacloprid (IMI), acetamiprid (ACE), and thiamethoxam (TMX), were mixed and evenly sprayed on Brassica chinensis L. in the field. Then, the insecticides’ residues were dynamically monitored to determine the differences in their rates of dissipation and final residues after 10 days. The results showed that the dissipation kinetics of neonicotinoids still conformed to the first-order kinetic model for binary or ternary application of neonicotinoid mixtures, with all determination coefficients (R2) being above 0.9 and the dissipation half-life (DT50) being 2.87–6.74 d. For treatment groups with five times the recommended dosages (IMI 300 g·hm−2, ACE 900 g·hm−2, and TMX 600 g·hm−2), mixed insecticides had a slower dissipation rate, and the DT50 values of mixtures were longer than those of single insecticides. Moreover, the final insecticide residues with mixed application were higher than those of single compounds at 10 d after spraying. Thus, mixed applications of neonicotinoids may increase food safety risks as they increase the final insecticide residues in Brassica chinensis L., and care should therefore be taken when considering the combined use of such compounds.
... Once inhaled, they persist in the body for varying lengths of time, which, amongst other things, depends on the chemical makeup. Recent evidence suggests that mixtures of chemicals can have a toxicological behaviour that differs from the toxicity of the individual chemicals [20,77] and may produce greater adverse health outcomes [64,71]. As a result, there is a growing movement in the environmental health community, including regulators, epidemiologists and health practitioners, to encourage the development of new paradigms of analysis to explore the impact of exposure to mixtures of airborne chemicals on health outcomes [24,41,57,68]. ...
Chapter
Exposure to pollution in the environment is a major contributor to disease globally and is a topic of great significance. There remains, however, a dearth of knowledge about the levels and distribution of airborne pollutants in the environment, along with how exposure to complex mixtures of airborne chemicals impacts health outcomes. Recent collaborations between artificial intelligence (AI) researchers and environmental health have demonstrated a great potential to help advance the science of air pollution epidemiology, urban planning and public policy. In this chapter, we discuss how AI can be leveraged to improve knowledge and understanding about air pollution and environmental health. We explore this question in general and present a case study on the DoMiNo project, which utilises AI algorithms in combination with pattern visualisation via VizAR and traditional epidemiological analysis to generate hypothesis about which mixtures of airborne chemicals negatively impact birth outcomes. Our results highlight both the great potential for AI in this field along with some interesting challenges for AI researchers to address in future work with environmental health researchers.
... It has been shown experimentally that chemicals may act jointly and that the combined toxicity may be higher than the toxicity of each of the single components on its own as reviewed by Kortenkamp et al. [43]. This may also be the case if substances are present at or below their regulatory thresholds, such as the EQS or NOEC [12,57]. In most cases chemicals have been shown to act additively following the established concepts of Concentration Addition (CA) or Independent Action (IA). ...
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It is acknowledged that a variety of chemicals enter the environment and may cause joint effects. Chemicals regulated under the European Chemicals Regulation REACH are often part of formulated mixtures and during their processing and use in various products they can be jointly released via sewage treatment plants or diffuse sources, and may combine in the environment. One can differentiate between intentional mixtures, and unintentional mixtures. In contrast to other substance-oriented legislations, REACH contains no explicit requirements for an assessment of combined effects, exposures and risks of several components. Still, it requires ensuring the safe use of substances on their own, in mixtures, and in articles. The available options to address intentional as well as unintentional mixtures are presented and discussed with respect to their feasibility under REACH, considering the responsibilities, communication tasks and information availability of the different actors (registrants, downstream-user and authorities). Specific mixture assessments via component-based approaches require a comprehensive knowledge on substances properties, uses, fate and behaviour, and the composition of the mixture under consideration. This information is often not available to the responsible actor. In principle, intentional mixtures of known composition can be assessed by the downstream-user. But approaches have to be improved to ensure a transparent communication and sound mixture assessment. In contrast, unintentional mixtures appear to be better addressable via generic approaches such as a mixture allocation factor during the chemical safety assessment, although questions on the magnitude, implementation and legal mandates remain. Authorities can conduct specific mixture risk assessments in well-defined and prioritized cases, followed by subsequent regulatory measures. In order to address intentional and unintentional mixtures within the current REACH framework, legal mandates together with guidance for the different actors are needed. Furthermore, further data on mixture compositions, uses and co-exposures need to be made accessible via shared databases.
... That concept also identified nodes that responded only to the mixture and not the individual exposures. 7 The study may be helpful for risk assessment because it found that mixture effects on the molecular scale-at least for these three components-were additive and could be predicted from single-compound knowledge. Model-based predictions are also useful as a reference point for assessing whether observed effects are additive, synergistic, or antagonistic. ...
... The co-occurrence of different mycotoxins in the same food commodity may change the nature of toxicity to animals and human beings due to possible antagonistic, additive or synergistic effects (Alassane-Kpembi et al., 2017). Despite the fact that synergism of mycotoxins could intensify the health risks, study on co-occurrence of mycotoxins has not received much attention till now (Silva et al., 2002). Basically, traditional and inappropriate practices of postharvest operations along with open-air storage arrangements support insect infestation, fungal growth and multi-mycotoxin formation. ...
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Incidence of mycotoxins in principal foods and grains is a major threat to achieving food safety but still remains one of the most underrated and ignored sources for food borne diseases, particularly in less developed countries. Furthermore, food insecurity together with ineffective government regulations and environmental conditions that favor fungal proliferation and toxin production merge together to make the people’s life even harder in countries like Nepal. Apart from wasting huge quantities of food every year, mycotoxins are associated with various acute and chronic health disorders including carcinogenic, mutagenic, estrogenic, digestive, vascular and nervous defects. Staple diets in less developed countries like Nepal are largely based on crops like maize, susceptible to mycotoxins which may ultimately lead to chronic health problems in large population. Although there is an immediate need to address the food safety challenges caused by mycotoxin contamination in cereal grains, studies so far in Nepal has been conducted mainly in aflatoxins in limited commodities only and very less efforts have been made to manage and mitigate the problems caused by mycotoxins in Nepal. Therefore, a thorough control of mycotoxins in overall food chain is essential to safeguard the health of the population which could be achieved by implementing stricter regulations, modern and scientific post-harvest operations, effective monitoring programs and raising necessary awareness among stakeholders. Int. J. Appl. Sci. Biotechnol. Vol 9(3): 152-159.
... The fact that combined effects may occur at "low doses", i.e. concentrations lower than NOAELs, indicate that individual NOAELs are not necessarily suitable indicators for risk assessment [49]. Silva & Kortenkamp [55], for example, showed that a mixture of 8 estrogenic chemicals, present at a concentration below their individual NOALs, was able to produce significant estrogenic activity. These xenoestrogens were able to act together ('joint action') to produce significant effects. ...
Article
Objective The biocompatibility of resin based dental composites has not yet been fully characterized even though certain monomers used in these composites are synthesized from Bisphenol A (BPA), a well-known estrogenic endocrine disruptor. As a result, they show structural relationship to BPA and can contain it as an impurity. Therefore, the estrogenic activity of 9 monomers, 2 photoinitiators, one photostabilizer and leachates of 4 commercially available composites was determined. Methods The ERα-CALUX bioassay was used to determine both agonistic and antagonistic estrogenic activities of the pure compounds (BPA, BisDMA, BisGMA, BisEMA(3), BisEMA(6), BisEMA(10), TEGDMA, TCD-DI-HEA, BADGE, UDMA, HMBP, DMPA, CQ) and the leachates of cured composite disks. The leachates of 4 commercially available composites (Solitaire 2, Ceram.x Spectra ST, G-ænial Posterior and Filtek Supreme XTE) in water and 0.1 M NaOH (pH = 13, ‘worst-case scenario’) were tested for estrogenic activity (pooled leachates from 10 cured composite disks). Results Agonistic estrogenic activity was found for the monomer BisDMA, the photostabilizer HMBP and photoinitiator DMPA. All leachates from the 4 tested composites showed significant agonistic estrogenic activity higher than the DMSO control, and the highest activity (potency and efficacy) was found for Solitaire 2, followed by Ceram.x Spectra ST. Furthermore, antagonistic estrogenic activity was found in the leachates from G-ænial Posterior. Significance These results show that significant estrogenic activity was found in all leachates of the cured composite disks, and that this estrogenicity is most likely due to a mixture effect of multiple estrogenic compounds (including BPA, HMBP and DMPA). This indicates that further research into the endocrine activity of all the compounds that are present in these composites (even at low quantities) and their possible mixture effect is warranted to guarantee their safe use.
... To date, over 200 chemicals of natural or synthetic origin have been identified to be estrogenic (Green et al., 2016). Therefore, even though most of these chemicals are documented to have relatively weak estrogenic activity individually and may result in no effects on regenerative capacity at environmentally relevant concentrations, the possibility of additive and/or synergistic effects from mixtures, such as the phenomenon known as "something from nothing" (Silva et al., 2002), should be highlighted because these chemicals are likely to exist in nature simultaneously (Sun et al., 2011;Witorsch, 2002). Therefore, future work should emphasize the combined effects of estrogenic substances following low-level chronic exposure. ...
Article
For fish and other aquatic organisms, disrupting their capacity for repair and regeneration will reduce their quality of life and survivorship in the wild. Studies have shown that 17α-ethinylestradiol (EE2), a synthetic estrogenic endocrine disrupting chemical (EEDC), can inhibit caudal fin regeneration in larval zebrafish following fin amputation. However, whether the inhibitory effects of EE2 are dependent on estrogen receptor (ER) remains unknown. Therefore, in this study, amputated zebrafish larvae were exposed to the ER agonist EE2 alone and in combination with the ER antagonist ICI 182,780 (ICI), and the change in regenerative capacity was determined. The inhibition of fin regeneration caused by EE2 alone (100 ng/L) was ameliorated after combination with ICI (30–300 μg/L), and these changes in regeneration-related signaling and the immune system corresponded with morphological observations, implying that the effects of EE2 on regeneration were possibly initiated by the activation of ER. Furthermore, the role of ER was confirmed with a natural ligand of ER, namely, 17β-estradiol (E2), and as expected, the effects of E2 (10, 100 and 1000 ng/L) paralleled those of EE2. In conclusion, EEDCs can disrupt the regenerative capacity in zebrafish, possibly due to the binding and activation of ERs and the consequent alteration of signaling pathways that regulate fin regeneration and immune competence. Given that EEDCs appear to be ubiquitous in the aquatic environment, the risk of these chemicals might be readdressed regarding their potential effects on tissue repair and regeneration.
... Beyond this "one chemical at a time" approach is growing evidence that mixtures of EDCs may have effects that cannot be predicted from outcomes based on single chemical testing. This means that doses of EDCs below the estimated no observed adverse effect level (NOAEL) for an endpoint may have adverse effects when given in combination [23][24][25][26][27][28][29]. This is a closer representation of real-world exposure compared to previous models and highly relevant to humans who are ubiquitously exposed to many chemicals [30][31][32]. ...
Article
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Humans and wildlife are exposed to endocrine-disrupting chemicals (EDCs) throughout their lives. Environmental EDCs are implicated in a range of diseases/disorders with developmental origins, including neurodevelopment and behavior. EDCs are most often studied one by one; here, we assessed outcomes induced by a mixture designed to represent the real-world situation of multiple simultaneous exposures. The choice of EDCs, which we refer to as “NeuroMix,” was informed by evidence for neurobiological effects in single-compound studies and included bisphenols, phthalates, vinclozolin, and perfluorinated, polybrominated, and polychlorinated compounds. Pregnant Sprague Dawley rats were fed the NeuroMix or vehicle, and then offspring of both sexes were assessed for effects on postnatal development and behaviors and gene expression in the brain in adulthood. In order to determine whether early-life EDCs predisposed to subsequent vulnerability to postnatal life challenges, a subset of rats were also given a stress challenge in adolescence. Prenatal NeuroMix exposure decreased body weight and delayed puberty in males but not females. In adulthood, NeuroMix caused changes in anxiety-like, social, and mate preference behaviors only in females. Effects of stress were predominantly observed in males. Several interactions of NeuroMix and stress were found, especially for the mate preference behavior and gene expression in the brain. These findings provide novel insights into how two realistic environmental challenges lead to developmental and neurobehavioral deficits, both alone and in combination, in a sex-specific manner.
... Although the synergism of mycotoxins could increase health risks, there has been little study on the combined effects of mycotoxins. Sometimes, it is possible that the threshold dose of toxicity may be exceeded when exposed to a mixture even though a single toxin exposure is less risky [5]. ...
Article
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Occurrence of mycotoxins in staple foods is a major threat to attaining food safety in developing countries. The study investigated multi-mycotoxin contamination for the first time in Nepalese maize along with the incidence of molds in 45 samples of maize used as human food from 45 districts of Nepal. The samples were analyzed quantitatively for the presence of five different mycotoxins (total aflatoxins (AF), total fumonisins (FUM), ochratoxin (OT), zearalenone (ZEA) and (DON) deoxynivalenol) using the competitive direct ELISA technique. The most frequent occurrences were for DON (100%) and AF (78%) followed by FUM and ZEA (both 76%) and OT (62%). Interestingly, all the samples contained at least two mycotoxins while at least three or more mycotoxins were found in 87% of the samples. The most commonly reported binary, ternary and quaternary combinations were DON+AF, AF+FUM+DON and AF+FUM+ZEA+DON, respectively. The mean percentage kernel mold infection was 35.33% with Fusarium, Aspergillus, Rhizopus and Penicillium genera being the predominant molds. Six different species of Aspergillus and a single species of Fusarium were identified. The estimated daily intake, margin of exposure and risk of liver cancer from consuming maize were 30.46 ng/kg bw/day and 5.58 and 0.38 cancer cases/year/100,000 population, respectively. Since maize is the second-most consumed cereal in Nepal, the contamination levels of various mycotoxins and the incidence of molds identified in the study suggests that stricter control is needed to safeguard the health of the substantial population consuming maize as a staple diet.
... It is known that people are faced with metal mixture exposures in reality. More evidences emerged suggesting the toxic effects of metal mixture exposures were not the same as that of a single metal (Silva et al. 2002;Wu et al. 2016). Therefore, we should pay more attention to the potential health effects related to metal mixture exposures in the development of dyslipidemia or alteration in lipid profile. ...
Article
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The majority of epidemiological investigations on metal exposures and lipid metabolism employed cross-sectional designs and focused on individual metal. We explored the associations between metal mixture exposures and longitudinal changes in lipid profiles and potential sexual heterogeneity. We recruited 250 men and 73 women, aged 40 years at baseline (2012), and followed them up in 2020, from the manganese-exposed workers healthy cohort. We detected metal concentrations of blood cells at baseline with inductively coupled plasma mass spectrometry. Lipid profiles were repeatedly measured over 8 years of follow-up. We performed sparse partial least squares (sPLS) model to evaluate multi-pollutant associations. Bayesian kernel machine regression was utilized for metal mixtures as well as evaluating their joint impacts on lipid changes. In sPLS models, a positive association was found between manganese and change in total cholesterol (TC) (beta = 0.169), while a negative association was observed between cobalt (beta = − 0.134) and change in low density lipoprotein cholesterol (LDL-C) (beta = − 0.178) among overall participants, which were consistent in men. Interestingly, rubidium was positively associated with change in LDL-C (beta = 0.273) in women, while copper was negatively associated with change in TC (beta = − 0.359) and LDL-C (beta = − 0.267). Magnesium was negatively associated with change in TC (beta = − 0.327). We did not observe the significantly cumulative effect of metal mixtures on lipid changes. In comparison to other metals, manganese had a more significant influence on lipid change [group PIP (0.579) and conditional PIP (0.556) for TC change in men]. Furthermore, male rats exposed to manganese (20 mg/kg) had higher levels of LDL-C in plasma and more apparent inflammatory infiltration, vacuolation of liver cells, nuclear pyknosis, and fatty change than the controls. These findings highlight the potential role of metal mixtures in lipid metabolism with sex-dependent heterogeneity. More researches are needed to explore the underlying mechanisms.
... It is possible to study mixtures in toxicology through well-established mathematical models for the calculation of expected additivity and identification of additive, synergistic, or antagonistic effects [26][27][28]. However, to the best of our knowledge, this approach has never been applied to SCFA mixtures. ...
Article
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The colon microbiota is an important player in colorectal cancer (CRC) development, which is responsible for most of the cancer-related deaths worldwide. During carcinogenesis, the colon microbiota composition changes from a normobiosis profile to dysbiosis, interfering with the production of short-chain fatty acids (SCFAs). Each SCFA is known to play a role in several biological processes but, despite their reported individual effects, colon cells are exposed to these compounds simultaneously and the combined effect of SCFAs in colon cells is still unknown. Our aim was to explore the effects of SCFAs, alone or in combination, unveiling their biological impact on CRC cell phenotypes. We used a mathematical model for the prediction of the expected SCFA mixture effects and found that, when in mixture, SCFAs exhibit a concentration addition behavior. All SCFAs, alone or combined at the physiological proportions founded in the human colon, revealed to have a selective and anticancer effect by inhibiting colony formation and cell proliferation, increasing apoptosis, disturbing the energetic metabolism, inducing lysosomal membrane permeabilization, and decreasing cytosolic pH. We showed for the first time that SCFAs are specific towards colon cancer cells, showing promising therapeutic effects. These findings open a new road for the development of alternatives for CRC therapy based on the increase in SCFA levels through the modulation of the colon microbiota composition.
... Page 2 of 14 Markert et al. Environmental Sciences Europe (2022) 34:100 micropollutants often occur in complex mixtures of numerous individual substances, which might result in a biologically relevant joint mixture toxicity, even if each individual substance occurs at low (non-toxic) concentrations [9,10]. Because of the very high number of micropollutants, however, a comprehensive monitoring of these substances and their complex mixtures remains laborious and very resource-intensive, which may explain, why this stressor group remained underaddressed-or even unaddressed-in previous multiplestressor studies (e.g. ...
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Background A variety of anthropogenic stressors influences the ecological status of rivers wordwide. Important stressors include elevated concentrations of nutrients, salt ions, heavy metals and other pollutants, habitat degradation and flow alteration. Some stressors tend to remain underrepresented in multiple-stressor studies, which in particular is apparent for micropollutants (e.g. pesticides, pharmaceuticals) and alterations of the flow regime. This case study analysed and compared the effects of 19 different stressor variables on benthic macroinvertebrates in the two German rivers Erft and Niers (Federal State of North Rhine-Westphalia, Germany). The stressors variables were assigned to four stressor groups (physico-chemical stress, mixture toxicity of 42 micropollutants, hydrological alteration and morphological degradation) and were put into a hierarchical context according to their relative impact on the macroinvertebrate community using redundancy analysis and subsequent variance partitioning. Results The results suggest a strong and unique effect of physico-chemical stress, yet at the same time reveal also a strong joint effect of physico-chemical and hydrological stressor variables. Morphological degradation showed subordinate effects. Notably, only a minor share of the explained variance was attributed to the mixture toxicity of micropollutants in these specific catchments. Conclusions The stressor hierarchy indicates that management measures for improving the ecological status still need to address water quality issues in both rivers. The strong joint effect of physico-chemical stress and hydrological alteration might imply a common source of both stressor groups in these two catchment areas: lignite mining drainage, urban area and effluents of wastewater treatment plants. The findings point at the important role of alterations in the flow regime, which often remain unconsidered in hydro-morphological surveys.
... Literature review [12,13] allowed the construction of a list of potential alterations or targets on which the compounds can interact individually or in combination. ...
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Chemicals from Pharmaceuticals and Personal Care Products (PPCPs) have become much more prevalent in the environment in recent years. The effects of these substances on human health and the environment are frequently debatable because they typically have poorly understood mechanisms of toxic action. For this reason, we set out to evaluate a binary mixture consisting of butylhydroxyanisole (BHA) and propylparaben (PPB), two approved additives that have been found in the environment and have a range of health-related effects. Based on our prior research, we chose an experimental model called Vero cells, kidney fibroblasts from the African green monkey (Chlorocebus aethiops), with high sensitivity in toxicology studies and ideal characteristics for the analysis of chemical compounds’ mechanisms of action. The experimental design includes a battery of tests using many complimentary biochemical and morphological biomarkers, the usefulness of which we have previously established. The outcomes demonstrated that the mixtures of BHA and PPB cause significant functional alterations brought on by osmotic imbalance, which are connected to irregularities in cell cycle progression, increases in ploidy, which included cell cycle imbalances as well as increases in proliferation. On the other hand, we have been able to show that the quantitative estimate of the anticipated cellular responses generally does not adjust precisely to the observed effect through the analysis of the prediction of the combined effect using mathematical models. However, once the individual compounds’ respective mechanisms of action have been established, the toxicity caused by the mixtures can be qualitatively predicted.
... Much lower concentrations of multiple individual substances can achieve a combined effect that is greater than the action of the substances themselves [270]. This effect has been aptly called "something from nothing" [271]. Therefore, the risks may be higher than indicated by studies dealing only with the effect of a single progestin. ...
Article
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Progesterone is a steroid hormone traditionally linked with female fertility and pregnancy. In current reproductive medicine, progesterone and its analogues play crucial roles. While the discovery of its effects has a long history, over recent decades, various novel actions of this interesting steroid have been documented, of which its neuro- and immunoprotective activities are the most widely discussed. Discoveries of the novel biological activities of progesterone have also driven research and development in the field of progesterone analogues used in human medicine. Progestogen treatment has traditionally and predominately been used in maintaining pregnancy, the prevention of preterm labor, various gynecological pathologies, and in lowering the negative effects of menopause. However, there are also various other medical fields where progesterone and its analogues could find application in the future. The aim of this work is to show the mechanisms of action of progesterone and its metabolites, the physiological and pharmacological actions of progesterone and its synthetic analogues in human medicine, as well as the impacts of its production and use on the environment.
... Like the prior iPSC cytotoxicity assays, a concentration addition model (GCA) produced more accurate results as concentrations increased as both ES and IA models overestimated mixture effects because of their limited ability to account for partial agonists. As the dilution increased, all tested models (GCA, IA, ES) approximated each other, agreeing with the accuracy that others have found in nuclear receptor driven in vitro assays (Silva et al., 2002;Watt et al., 2016). ...
Article
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The United States Environmental Protection Agency (EPA) has been pursuing new high throughput in vitro assays to characterize endocrine disrupting chemicals (EDCs) that interact with estrogen receptor signaling. We characterize two new PRL-HeLa cell models expressing either inducible C-terminal (iGFP-ER) or N-terminal (iER-GFP) tagged estrogen receptor-α (ERα) that allows direct visualization of chromatin binding. These models are an order of magnitude more sensitive, detecting 87 - 93% of very weak estrogens tested compared to only 27% by a previous PRL-HeLa variant and compares favorably to the 73% detected by an EPA-developed computational model using in vitro data. Importantly, the chromatin binding assays distinguished agonist- and antagonist-like phenotypes without activity specific assays. Finally, analysis of complex environmentally relevant chemical mixtures demonstrated how chromatin binding data can be used in risk assessment models to predict activity. These new assays should be a useful in vitro tool to screen for estrogenic activity.
... These results are in line with previous studies conducted in other regions on smaller groups of children, but also demonstrating multiple exposure (Iglesias-González et al. 2020;Iglesias-González et al. 2021;Palazzi et al. 2019). Although the impact of cumulative exposure on health is increasingly pointed out (Borman et al. 2017;Silva et al. 2002;Song et al. 2016), the assessment of exposure to multiple pollutants and the associated risks remains highly challenging (Hernández et al. 2017;Iglesias-González et al. 2021). Yet, most studies still resort on single compound, therefore providing information that is not representative of reality and cannot be used by regulatory agencies to establish "safe" exposure levels (Hernández et al. 2017;Kostoff et al. 2018). ...
Article
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The specific physiology and behaviour of children makes them particularly vulnerable to chemical exposure. Specific studies must therefore be conducted to understand the impact of pollution on children’s health. Human biomonitoring is a reliable approach for exposure assessment, and hair, allowing the detection of parent chemicals and metabolites, and covering wider time windows than urine and blood is particularly adapted to study chronic exposure. The present study aims at assessing chemical exposure and investigating possible determinants of exposure in children living in Luxembourg. Hair samples were collected from 256 children below 13 y/o and tested for 153 compounds (140 pesticides, 4 PCBs, 7 BDEs and 2 bisphenols). Moreover, anthropometric parameters, information on diet, residence, and presence of pets at home was collected through questionnaires. Correlations, regressions, t-tests, PLS-DA and MANOVAs, were used to investigate exposure patterns. Twenty-nine to 88 (median = 61) compounds were detected per sample. The highest median concentration was observed for BPA (133.6 pg/mg). Twenty-three biomarkers were detected in ≥ 95% of the samples, including 13 in all samples (11 pesticides, BPA and BPS). Exposure was higher at younger ages (R² = 0.57), and boys were more exposed to non-persistent pesticides than girls. Presence of persistent organic pollutants in most children suggests that exposure is still ongoing. Moreover, diet (e.g. imazalil: 0.33 pg/mg in organic, 1.15 pg/mg in conventional, p-value < 0.001), residence area (e.g. imidacloprid: 0.29 pg/mg in urban, 0.47 pg/mg in countryside, p-value = 0.03), and having pets (e.g. fipronil: 0.32 pg/mg in pets, 0.09 pg/mg in no pets, p-value < 0.001) were identified as determinants of exposure. The present study demonstrates that children are simultaneously exposed to multiple pollutants from different chemical classes, and confirms the suitability of hair to investigate exposure. These results set the basis for further investigations to better understand the determinants of chemical exposure in children.
... Nevertheless, this assumption has been controverted as some studies demonstrated that exposure to a mixture of metals induced detrimental effects in organisms (Yologlu and Ozmen, 2015) with toxicity at various biological/physiological targets (Butrimavičienė et al., 2019;Lebrun et al., 2017), even at maximum permissible concentrations to the aquatic system (Butrimavičienė et al., 2019) and concentrations close to environmental quality standards from the European Water Framework Directive (Lebrun et al., 2017). Therefore and since organisms are exposed on a daily basis to a mix of chemicals instead of a single component, ignoring the possibility of joint action of chemical substances may lead to an underestimation of environmental risks (Shao et al., 2019;Silva et al., 2002) and this has been identified as a major shortcoming that needs more attention (Backhaus and Faust, 2012). ...
Article
Rare earth elements (REEs) are considered critical elements for technology and their extraction through mining activities is expected to increase in the future. Due to their chemical similarities, they often co-occur in minerals and thus their ecotoxicity should be assessed as a group/family. However, the available ecotoxicological studies focused mainly on the evaluation of the potential toxicological impacts of individual REEs rather than their mixtures. The aim of this study was therefore to evaluate the toxicity of a representative mixture of five REEs (La, Ce, Pr, Nd and Sm) spanning environmentally relevant concentrations ranging from 0.05X (29 µg REEs L-1) to 5X (2926 µg REEs L-1) to the test organism, Hydra vulgaris, at the morphological, reproductive and regenerative levels. The data showed that lethality occurred at concentrations near (2.5 fold) to those inducing sublethal effects after chronic exposure of 7 days. The mixture affected reproduction and head regeneration and even lethality at concentrations even below those reported at environmental concentration (0.5X = 293 µg REEs L-1) in lakes. This suggests that REEs concentrations found in lakes near mining activities could disrupt regeneration and impair embryonic development. Our data also revealed that combining the 5 REEs results in an antagonistic effect, suggesting that those elements share the same receptor and that low molecular weight and high radius elements (approaching iron) were less toxic. Taken together, hydra could be used as a sensitive model organism for the assessment of aquatic ecotoxicological risks of REE mixtures but further analyses of biochemical and gene expressions should improve our understanding of the long-term effects of REEs mixtures.
Article
Endocrine-disrupting chemicals (EDCs) can adversely impact the hormonal control, sexual differentiation, reproductive success, and community structure of aquatic organisms. Nonylphenol is one kind of typical EDCs which has attracted increasing attention in recent years. The water quality criteria (WQC) of nonylphenol have been established in several countries/institutions according to the water quality guidelines. However, the reproduction toxicity characteristic of EDCs was excluded in the previous WQC study. In this study, the current research progress on WQC for nonylphenol in different countries/institutions is summarized. In addition, the methodology for deriving the WQC based on reproduction toxicity of EDCs, such as selecting a sensitive test species with a hypothalamic–pituitary–gonadal axis or an endocrine-like system, selecting the appropriate endpoint effects for reproduction toxicity, and collecting the chronic toxicity data are discussed. Finally, the predicted no-effect concentration (PNEC) of nonylphenol derived based on the reproduction toxicity endpoint data was 0.38 μg/L. This result indicated that the PNEC based on reproductive fitness occurred at significantly lower concentrations than that of the other derived toxicity endpoints. The results of this study would provide data support for WQC research and risk assessment of endocrine disruptors.
Article
Human exposure to bisphenol A (BPA) and bisphenol S (BPS) has garnered considerable global health concerns. In this paper, the daily intake (DI) of BPA and BPS in the general population of Guangzhou, China, were back-calculated using the biomarkers BPA glucuronides (BPA-G) and BPS glucuronides (BPS-G), respectively. The biomarkers are preferable to total BPA and BPS measurements because they are not susceptible to external contamination. A total of 1440 urine samples were gathered from the general population in Guangzhou, China, which were classified by age and sex into 36 pooled urine samples. 100% and 98% of pooled urine samples contained BPA-G and BPS-G at median values of 1.57 and 0.38 ng/mL, respectively. Based on urinary BPA-G and BPS-G concentrations, we determined the median DI of BPA and BPS to be 31.07 and 7.37 ng/(kg bw*d), respectively, and the highest values to be 106.77 ng/(kg bw*d) and 18.19 ng/(kg bw*d), respectively. Furthermore, our results showed that for the entire dataset, the DI of BPA and BPS were considerably greater in males than in females (p < 0.01)and declined significantly with age (p < 0.05). For risk assessment, the estimated DIs of BPA and BPS were much lower than the European Food Safety Authority’ s (EFSA) the temporary acceptable reference dose of 4 μg/(kg bw*d) advised for BPA, suggesting that the exposure risk of BPA and BPS for Guangzhou population is within a controllable safety range. This is the first study to investigate BPA and BPS exposure in the general population of Guangzhou, China, on the basis of urinary metabolites.
Article
Introduction Breast cancer (BC) is frequent with a poor prognosis in case of metastasis. The role of the environment has been poorly evaluated in its progression. We searched to assess whether a mixture of pollutants could be responsible of BC aggressiveness. Methods Patients undergoing surgery for their BC were prospectively included in the METAPOP cohort. Forty-two POPs were extracted, among them 17 dioxins (PCDD/F), 16 polychlorobiphenyls (PCB), 8 polybromodiphenylethers (PBDE) and 2,2',4,4',5,5'-hexabromobiphenyl (PBB153) were measured in the adipose tissue surrounding the tumor. BC aggressiveness was defined using tumor size and metastasis (distant or lymph nodes). Two complementary models were used to evaluate the impact of the mixture of pollutants: the BKMR (Bayesian Kernel machine regression) and WQS (weighted quantile sum regression) models. The WQS estimates the weight (positive or negative) of a certain chemical based on its quantile and the BKMR model applies a kernel-based approach to estimate posterior inclusion probabilities. The sub-group of patients with a body mass index (BMI) > 22kg/ m² was also analyzed. Results Ninety-one patients were included. Of these, 38 patients presented a metastasis, and the mean tumor size was 25.4 mm. The mean BMI was 24.5 kg/m² (+/- 4.1). No statistical association was found in the general population. However, in patients with a BMI > 22kg/ m², our mixture was positively associated with tumor size (OR: 9.73 95%CI: 1.30-18.15) and metastasis (OR = 3.98 95%CI= 1.09-17.53) using the WQS model. Moreover, using the BKMR model on chemical families, dioxin like chemicals and PCDD were associated with a higher risk of metastasis. Discussion These novel findings identified a mixture associated with breast cancer aggressiveness in patients with a BMI > 22kg/ m².
Chapter
The chemicals which interrupt and disturb the regular activity and functionality of endocrine system are called as disruptors having diverse character and structures, and disturb the functionality of endocrine glands by diverse ways. Due to these chemicals, there are several health hazards that have been reported such as neurological and behavioral disorders, metabolic dysfunction leading to obesity, and other related diseases, such as reproductive and thyroid dysfunctions, and even some can lead to the fatal diseases like cancer. They include pesticides, insecticides, fungicides like DDT and chlorpyrifos as well as the chemicals which are used in paints, perfumes, toys, furniture, plastics, electronic gadgets, and food and packaging items. Around the globe, these chemicals are present in handsome amount and are posing a serious threat to the overall health conditions of mankind. This chapter highlights the character, structure, and chemical action of these compounds, and explains the mechanism and working relating to disturbing the endocrine system by biomonitoring and data analysis.
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In malaria-endemic areas in South Africa, traditional huts are sprayed with 1,1,1-trichloro-2,2-bis(chlorodiphenyl)ethane (DDT) while modern structures are sprayed with pyrethroid insecticides. With modernization of housing and DDT sourcing costs, spray programs have changed. Coupled with this is an increase in agricultural pesticide use, creating another source of exposure. However, DDT and pyrethroids are considered endocrine disrupting chemicals (EDCs). Exposure to complex mixtures of EDCs is associated with adverse male reproductive health including a decline in sperm and semen quality. Thus, the aim of the study was to investigate the impact of exposure to a complex mixture of EDCs, DDT pyrethroids and other agricultural pesticides, on seminal parameters, hormonal regulation and sperm chromatin integrity. In a cross-sectional study conducted between 2003 and 2008 (n = 544, from three DDT-sprayed villages—n = 310, three non-DDT sprayed villages—n = 234) and 2012–2017 (n = 431 young males from three DDT-exposed—n = 236; three non-DDT exposed—n = 195); young males were recruited from a malaria endemic area in Limpopo Province, South Africa where DDT was used in indoor residual spraying. Exposure levels of DDT (measured in blood plasma) pyrethroids and other pesticides (measured in urine) were determined and a semen analysis was conducted according to WHO standards. Linear regression models were examined to evaluate DDT/DDE effects on different reproductive outcomes. In sprayed villages p,p′-DDE exposure levels were significantly lower between 2012 and 2017 (mean ± SD: 5.80 ± 6.6 μg/g) compared to the 2003–2008 (216.9 ± 210.6 μg/g) period (P < 0.001). In the non-sprayed villages p,p′-DDE exposure levels were significantly lower between 2012 and 2017 (mean ± SD: 1.47 ± 3.68 μg/g) compared to the 2003–2008 (2.81 ± 4.26 μg/g) period (P < 0.001). Sperm counts were significantly lower (P = 0.04) in the 2012–2017 period (45.30 ± 49.20 mil/ml) compared to 2003–2008 (51.91 ± 48.25 mil/ml). Analysis showed that 3,5,6-trichloro-2-pyridinol (TCPY), 1,2,3-benzotriazine-4-one (BTA) a herbicide and 3-(2,2-dichlororvinyl)-2,2-dimethyl-cyclopropane-1-carboxylic acid (Trans/DCCA) were the most common metabolites. Despite the decline in exposure levels over time, seminal parameters and chromatin integrity were still affected. While still dependent on DDT and pyrethroids for malaria vector control, a more sustainable approach is needed towards malaria elimination, involving transdisciplinary approaches.
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Are the effluents of wastewater treatment plants in high mountains of concern for aquatic biodiversity? To answer this question, we carried out an experimental study testing the short-term toxicity of some Pharmaceutical Active Compounds (PhACs) in the effluents of a plant in a mountain valley of the Italian Alps sampled during the high tourist season (i.e., the ski season) when PhACs contamination is higher. We used different tools, taking as a model the bacterium Aliivibrio fischeri: the “whole-mixture approach” (Microtox test), “component-based approach”, predictive models “Concentration Addition (CA)”, “Independent Action (IA)”, and Combination Index (CI)”. We investigated the nature of interactions potentially occurring among seven selected PhACs (clarithromycin, naproxen, acetaminophen (paracetamol), ibuprofen, diclofenac, carbamazepine, and amoxicillin). This study showed that anti-inflammatory ibuprofen and diclofenac have higher short-term toxicity (IC50
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Endocrine-disrupting chemicals (EDCs) belong to a heterogeneous class of environmental pollutants widely diffused in different aquatic and terrestrial habitats. This implies that humans and animals are continuously exposed to EDCs from different matrices and sources. Moreover, pollution derived from anthropic and industrial activities leads to combined exposure to substances with multiple mechanisms of action on the endocrine system and correlated cell and tissue targets. For this reason, specific organs, such as the prostate gland, which physiologically are under the control of hormones like androgens and estrogens, are particularly sensitive to EDC stimulation. It is now well known that an imbalance in hormonal regulation can cause the onset of various prostate diseases, from benign prostate hyperplasia to prostate cancer. In this review, starting with the description of normal prostate gland anatomy and embryology, we summarize recent studies reporting on how the multiple and simultaneous exposure to estrogenic and anti-androgenic compounds belonging to EDCs are responsible for an increase in prostate disease incidence in the human population.
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The human population is exposed to endocrine-disrupting chemicals (EDCs) as complex mixtures through inhalation (air), oral intake (water, food), or dermal applications (household and personal care products), and the measurement of so many hundreds of EDCs in human body tissues implies that adverse effects on human endocrine health must also be considered as resulting from exposure not to single chemicals but to complex mixtures in the target tissues. Much of the scientific evidence for endocrine disruption comes from studies of single chemicals, but this chapter will review emerging evidence that chemical mixtures can cause endocrine disruption through additive mechanisms between EDCs with a similar mode of action, and complementary mechanisms between EDCs with different modes of action. Since EDCs are present in human body tissues over the long term, often building up over many years, the effects of exposure to EDCs over long periods of time rather than just a short time frame is a relevant environmental issue. Most in vitro assays are performed over a period of hours or days, and emerging evidence is discussed that consequences may arise in cells after long-term EDC exposures which are not observed following only short-term exposures.
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The environmental pollution caused by toxic chemicals such as pesticides has become a global problem. The mixture of dichlorvos (DIC), dimethoate (DIM), aldicarb (ALD) poses potential risks to the environment and human health. To fully explore the interaction of complex mixtures on Caenorhabditis elegans behavioral toxicity endpoint. This study created a synergistic antagonistic heatmap (SAHmap) based on the combination index to systematically describe the toxicological interaction prospect of the mixture system. It was shown that the three pesticides and their binary as well as ternary mixture rays have significant concentration-response relationship on three behavioral endpoints of nematodes, From the perspective of synergistic-antagonistic heatmaps, all the mixture rays in the DIC-DIM mixture system showed strong synergism on the three behavioral and lethal endpoints. In the ternary mixture system, the five mixture rays showed different interaction between the behavioral endpoint and the lethal endpoint, and showed slight synergism to two behavioral endpoints as a whole. The emergence of synergism should arouse our attention to these hazardous chemicals. In addition, the use of SAHmap and the significant linear correlation among three behavioral endpoints further improved the efficiency of the study on the behavioral toxicity of pesticide mixtures to Caenorhabditis elegans.
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This chapter outlines some of the principles on which regulation of endocrine disrupting chemicals (EDCs) depends, and provides an introduction to the concepts of hazard, weight of evidence, and risk. Challenges for the regulation of chemicals which act through endocrine mechanisms are discussed. The value and limitations of different types of evidence for the assessment process and the approach of constructing adverse outcome pathways to identify key events and representative endpoints are described. Contributions to the regulatory processes by government, regulatory bodies (national and international), nongovernment organizations, the media, citizen responsibility, and the precautionary principle are outlined.
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Bisphenol A (BPA) and its substitutes, bisphenol F (BPF) and S (BPS), have previously shown in vitro obesogenic activity. This study was designed to investigate their combined effect on the adipogenic differentiation of human adipose-derived stem cells (hASCs). Cells were exposed for 14 days to an equimolar mixture of bisphenols (MIX) (range 10 nM–10 µM). Oil Red staining was used to measure intracellular lipid accumulation, quantitative real-time polymerase chain reaction (qRT-PCR) to study gene expression of adipogenic markers (PPARγ, C/EBPα, LPL, and FABP4), and Western Blot to determine their corresponding proteins. The MIX promoted intracellular lipid accumulation in a dose-dependent manner with a maximal response at 10 µM. Co-incubation with pure antiestrogen (ICI 182,780) inhibited lipid accumulation, suggesting that the effect was mediated by the estrogen receptor. The MIX also significantly altered the expression of PPARγ, C/EBPα, LPL, and FABP4 markers, observing a non-monotonic (U-shaped) dose-response, with maximal gene expression at 10 nM and 10 µM and lesser expression at 1 µM. This pattern was not observed when bisphenols were tested individually. Exposure to MIX (1–10 µM) also increased all encoded proteins except for FABP4, which showed no changes. Evaluation of the combined effect of relevant chemical mixtures is needed rather than single chemical testing.
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Hypospadias is the ectopic opening of the urethra on the penis or scrotum. Exposure to estrogenic and/or anti-androgenic chemicals in utero may play an etiologic role. DDT and the pyrethroids cypermethrin and deltamethrin, are used to control malaria. DDT is estrogenic and its breakdown product DDE is anti-androgenic; cypermethrin and deltamethrin can also disrupt androgen pathways. We examined the relationship between maternal exposure to these insecticides during pregnancy and hypospadias among boys participating in the Venda Health Examination of Mothers, Babies and their Environment (VHEMBE) in Limpopo Province, South Africa. We measured peripartum levels of p,p'-DDT and p,p'-DDE in maternal serum and urinary pyrethroid metabolites. We conducted urogenital examination on 359 one-year-old boys. A total of 291 (81.0 %) had phimosis, which prevented full urogenital examination, leaving a final sample of 68 boys for determination of the presence of hypospadias. Diagnosis was based on concordance of two independent physicians. We identified hypospadias in 23 of the 68 boys (34 %). Maternal urinary concentrations of cis-DCCA and trans-DCCA metabolites of cypermethrin and other pyrethroids, were associated with an increased risk for hypospadias, but the other metabolite 3-PBA was not (adjusted relative risk per 10-fold increase = 1.58, 95 % CI 1.07–2.34; 1.61, 95 % CI 1.09–2.36; and 1.48, 95 % CI 0.78–2.78, respectively). No associations were found between p,p'-DDT, p,p'-DDE, 3-PBA or cis-DBCA and hypospadias. We observed a high prevalence of hypospadias among boys without phymosis. Boys with higher prenatal exposure to pyrethroid insecticides were at higher risk of hypospadias. Our findings may have global implications given that pyrethroid insecticides are widely used for malaria control, in agriculture and for home use.
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This chapter begins with an overview of the extent to which endocrine-disrupting chemicals (EDCs) can enter human tissues from environmental exposure. Retention of EDCs in body tissues may be influenced both by their route of entry and by their resistance to physiological clearance processes. Their endocrine-disrupting activity and biological availability may also be influenced by endogenous metabolic reactions. Measurements using a range of body tissues have demonstrated the ubiquitous distribution of many EDCs across the human population, but the source of the body burden is difficult to establish due to the widespread use of these compounds. The measurement of so many different EDCs in human tissues demonstrates the potential for mixtures of EDCs at low doses to interfere in the long term on hormone regulation with adverse consequences for human health. Many different nonlinear, nonmonotonic dose responses to EDCs have been demonstrated, and effects at high doses may not always be predictive of effects at low doses. The effects of EDCs vary in different tissues and between individuals, but timing is also important. Critical windows of susceptibility to EDC exposure exist during prenatal life and early childhood, and some exposures to EDCs in utero can produce long-lasting effects into adult life and onto future generations.
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Background Bisphenol A (BPA) is found in many plastics widely used in everyday life and affects the immune system. Previous studies found that the selective G protein coupled estrogen receptor (GPER) agonist G-1 can reduce the inflammation associated with asthma and allergic rhinitis (AR). BPA also interferes with the protective effect of estradiol against myocardial ischemia-reperfusion injury. Objective We explored whether BPA attenuates the effect of G-1 on inflammation in a mouse AR model. Methods The AR model was established by sensitizing and stimulating female BALB/c mice with ovalbumin (OVA) and G-1/BPA. Eosinophils, neutrophils, and lymphocyte subsets (including T and B cells) in nasal mucosa and Th2 and Treg cells in the spleen were detected by flow cytometry. Cytokines and transcription factors characteristic of Th2 and Treg cells in nasal mucosa were detected using cytometric bead arrays and quantitative PCR, respectively. Results G-1 reduced OVA-induced nasal mucosal inflammation in mice. The proportions of eosinophils, neutrophils, Siglec-F⁺ neutrophils, lymphocytes, and T cell subsets were reduced by G-1, and this effect was attenuated by BPA. G-1 significantly decreased the Th2 population and levels of IL-4, IL-5, IL-13 and GATA-3; these effects were attenuated by BPA. The enhanced Treg response (as evidenced by an increased Treg population and higher IL-10 and Foxp3 levels) mediated by G-1 tended to be reduced by BPA. Discussion We found that G-1 reduced OVA-induced nasal mucosal inflammation and significantly decreased the Th2 response, while increasing the Treg response. These effects were attenuated by BPA.
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The role of the environment in breast cancer (BC) progression has recently been suggested. We aimed to assess if a mixture of pollutants, cigarette smoke, could favor its aggressivity. We also evaluated the impact of the micro-environment, largely represented by adipocytes, in mediating this. BC cells lines MCF-7 were cultured using a transwell co-culture model with preadipocytes hMADS cells or were cultured alone. Cells were treated by cigarette smoke extract (CSE) and the four conditions: control, CSE, co-culture and co-exposure (co-culture and CSE) were compared. We analyzed morphological changes, cell migration, resistance to anoikis, stemness, epithelial to mesenchymal transition (EMT) and presence of hormonal receptors in each condition. A complete transcriptomic analysis was carried out to highlight certain pathways. Several hallmarks of metastasis were specific to the coexposure condition (cell migration, resistance to anoikis, stemness) whereas others (morphological changes, EMT, loss of hormonal receptors) could be seen in the coculture condition and were aggravated by CSE (coexposure). Moreover, MCF-7 cells presented a decrease in hormonal receptors, suggesting an endocrine treatment resistance. These results were confirmed by the transcriptomic analysis. Our in vitro results suggest that a common mixture of pollutants could promote BC metastasis in a co-culture model.
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Endocrine-disrupting potential was evaluated during the sewage treatment process using in vitro bioassays. Aryl hydrocarbon receptor (AhR)-, androgen receptor (AR)-, glucocorticoid receptor (GR)-, and estrogen receptor (ER)-mediated activities were assessed over five steps of the treatment process. Bioassays of organic extracts showed that AhR, AR, and GR potencies tended to decrease through the sewage treatment process, whereas ER potencies did not significantly decrease. Bioassays on reverse-phase high-performance liquid chromatography fractions showed that F5 (log KOW 2.5-3.0) had great ER potencies. Full-scan screening of these fractions detected two novel ER agonists, arenobufagin and loratadine, which are used pharmaceuticals. These compounds accounted for 3.3-25% of the total ER potencies and 4% of the ER potencies in the final effluent. The well-known ER agonists, estrone and 17β-estradiol, accounted for 60 and 17% of the ER potencies in F5 of the influent and primary treatment, respectively. Fourier transform ion cyclotron resonance mass spectrometry analysis showed that various molecules were generated during the treatment process, especially CHO and CHOS (C: carbon, H: hydrogen, O: oxygen, and S: sulfur). This study documented that widely used pharmaceuticals are introduced into the aquatic environments without being removed during the sewage treatment process.
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Parabens and phthalates are commonly found as contaminants in human fluids and are able to provoke reproductive toxicity, being considered endocrine disruptors. To evaluate the effects of phthalate and paraben, alone or in combination, on reproductive development of the offspring, female pregnant Wistar rats were allocated in six experimental groups: three control groups [gavage (CG), subcutaneous (CS) and gavage+subcutaneous)] received corn oil as vehicle; the remaining groups were exposed to DEHP (500mg/kg, gavage), BP (100mg/kg, subcutaneously) or MIX (DEHP+ BP), from gestational day 12 until post-natal day (PND) 21. The following parameters were assessed on the offspring: anogenital distance and weight at PND1, nipple counting at PND13, puberty onset, estrous cycle, weights of reproductive and detoxifying organs, histological evaluation of reproductive organs and sperm evaluations (counts, morphology and motility). Female pups from MIX group presented reduced body weight at PND1, lower AGD and decreased endometrium thickness. Male animals showed decreased body weight at PND1 and lower number of Sertoli cells on DEHP and MIX groups; MIX group revealed increased of abnormal seminiferous tubules; DEHP animals presented delayed preputial separation and higher percentage of immotile sperms; BP males presented diminished number of Leydig cells. In conclusion, the male offspring was more susceptible to DEHP toxicity; even when mixed to paraben, the main negative effects observed seem to be due to anti-androgenic phthalate action. On the other hand, DEHP seems to be necessary to improve the effects of BP on reducing estrogenic and increasing androgenic dependent events.
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Following the restriction of bisphenol A (BPA) in certain products, a number of bisphenol analogues (BPs) have been used as BPA replacements in different applications, raising environmental and health concerns. The present study determined a total of 13 bisphenol analogues in house dust and children urine from South China families (n = 46). Among all BPs, BPA, bisphenol S (BPS) and bisphenol F (BPF) were frequently detected in house dust, with concentrations ranging from 0.54 to 26.2 μg/g (median: 2.60 μg/g), 0.07–11.5 μg/g (median: 0.32 μg/g) and 0.02–2.4 μg/g (median: 0.29 μg/g), respectively. BPA (median: 2.43 ng/mL) was also the dominant BP in children urine samples, accounting for 75.2 ± 27.4% of the total concentrations of urinary BPs, followed by BPS (0.23 ng/mL), whereas BPF was only detected in less than 30% of urine samples. Children's daily intake of bisphenols through dust ingestion and total daily intakes were estimated based on the dust and urine concentrations, respectively. The estimated intake of BPA, BPS and BPF via house dust ingestion accounted for 9%, 12% and 38% of the total intakes predicted based on urinary concentrations, respectively, and exhibited very low exposure risks.
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Background Prenatal exposure to persistent organic pollutants, including polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), dioxin-like polychlorinated biphenyls (DL-PCBs), and nondioxin-like PCBs (NDL-PCBs), has been hypothesized to have a detrimental impact on neurodevelopment. However, the association of prenatal exposure to a dioxin and PCB mixture with neurodevelopment remains largely inconclusive partly because these chemical levels are correlated. Objectives We aimed to elucidate the association of in utero exposure to a mixture of dioxins and PCBs with neurodevelopment measured at 6 months of age by applying multipollutant methods. Methods A total of 514 pregnant women were recruited between July 2002 and October 2005 in the Sapporo cohort, Hokkaido Study on Environment and Children's Health. The concentrations of individual dioxin and PCB isomers were assessed in maternal peripheral blood during pregnancy. The mental and psychomotor development of the study participants' infants was evaluated using the Bayley Scales of Infant Development-2nd Edition (n = 259). To determine both the joint and individual associations of prenatal exposure to a dioxin and PCB mixture with infant neurodevelopment, Bayesian kernel machine regression (BKMR) and quantile-based g-computation were employed. Results Suggestive inverse associations were observed between in utero exposure to a dioxin and PCB mixture and infant psychomotor development in both the BKMR and quantile g-computation models. In contrast, we found no association of a dioxin and PCB mixture with mental development. When group-specific posterior inclusion probabilities were estimated, BKMR suggested prenatal exposure to mono-ortho PCBs as the more important contributing factors to early psychomotor development compared with the other dioxin or PCB groups. No evidence of nonlinear exposure-outcome relationships or interactions among the chemical mixtures was detected. Conclusions Applying the two complementary statistical methods for chemical mixture analysis, we demonstrated limited evidence of inverse associations of prenatal exposure to dioxins and PCBs with infant psychomotor development.
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In vitro models of adipogenesis are phenotypic assays that most closely mimic the increase of adipose tissue in obesity. Current models, however, often lack throughput and sensitivity and even report conflicting data regarding adipogenic potencies of many chemicals. Here, we describe a ten-day long adipogenesis model using high content analysis readouts for adipocyte number, size, and lipid content on primary human mesenchymal stem cells (MSC) sensitive enough to compare bisphenol A derivatives quantitatively in a robust and high throughput manner. The number of adipocytes was the most sensitive endpoint capable of detecting changes of 20% and was used to develop a benchmark concentration model (BMC) to quantitatively compare eight bisphenols (tested at 0.1–100 μM). The model was applied to evaluate mixtures of bisphenols obtaining the first experimental evidence of their additive effect on human MSC adipogenesis. Using the relative potency factors (RPFs), we show how a mixture of bisphenols at their sub-active concentrations induces a significant adipogenic effect due to its additive nature. The final active concentrations of bisphenols in tested mixtures reached below 1 μM, which is within the concentration range observed in humans. These results point to the need to consider the toxicity of chemical mixtures.
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Modern society continues to pollute the environment with larger quantities of chemicals that have also become more structurally and functionally diverse. Risk assessment of chemicals can hardly keep up with the sheer numbers that lead to complex mixtures of increasing chemical diversity including new chemicals, substitution products on top of still abundant legacy compounds. Fortunately, over the last years computational tools have helped us to identify and prioritize chemicals of concern. These include toxicokinetic models to predict exposure to chemicals as well as new approach methodologies such as in-vitro bioassays to address toxicodynamic effects. Combined, they allow for a prediction of mixtures and their respective effects and help overcome the lack of data we face for many chemicals. In this study we propose a high-throughput approach using experimental and predicted exposure, toxicokinetic and toxicodynamic data to simulate mixtures, to which a virtual population is exposed to and predict their mixture effects. The general workflow is adaptable for any type of toxicity, but we demonstrated its applicability with a case study on neurotoxicity. If no experimental data for neurotoxicity were available, we used baseline toxicity predictions as a surrogate. Baseline toxicity is the minimal toxicity any chemical has and might underestimate the true contribution to the mixture effect but many neurotoxicants are not by orders of magnitude more potent than baseline toxicity. Therefore, including baseline-toxic effects in mixture simulations yields are more realistic picture than excluding them in mixture simulations. This workflow did not only correctly identify and prioritize known chemicals of concern like benzothiazoles, organochlorine pesticides and plasticizers but we were also able to identify new potential neurotoxicants that we recommend to include in future biomonitoring studies and if found in humans, to also include in neurotoxicity screening.
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We tested whether bisphenol A (BPA) or o,p'-DDT, when combined with 17beta-estradiol (E2), would contribute to the overall mixture effect using a yeast reporter gene assay, the yeast estrogen screen. Following comprehensive concentration-response analyses of the single agents, the pharmacologically well-founded models of concentration addition and independent action were used to predict entire concentration-response relationships for mixtures of the agents with a variety of fixed mixture ratios, assuming additivity. For molar mixture ratios proportional to the levels normally found in human tissues (i.e., below 1:5000, E2:BPA or o,p'-DDT), these predictions suggest that the effects of individual xenoestrogens are too weak to create an impact on the actions of steroidal hormones. However, at mixture ratios more in favor of the xenoestrogens, a significant contribution to the overall mixture effect was predicted. The predictions were tested experimentally. The observed combined effects of mixtures of E2 with either BPA or o,p'-DDT did not deviate from the additivity expectation. On combining E2 with either BPA or o,p'-DDT at approximately equieffective concentrations corresponding to molar mixture ratios between 1:20,000 and 1:100,000 (E2:BPA or o,p'-DDT), substantial modulations of the effects of E2 became discernible. The assumption that weak xenoestrogens are generally unable to create an impact upon the already strong effects of endogenous steroidal estrogens is not supported by our observations. Our studies indicate that the potential health implication of additive combination effects between xenoestrogens and steroidal estrogens deserve serious consideration.
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An estrogen-inducible screen was developed in yeast (Saccharomyces cerevisiae) in order to assess whether surfactants and their major degradation products are estrogenic. The DNA sequence of the human estrogen receptor (hER) was integrated into the yeast genome, which also contained expression plasmids carrying estrogen-responsive sequences (ERE) controlling the expression of the reporter gene lac-Z (encoding the enzyme β-galactosidase). Thus, in the presence of estrogens, β-galactosidase is synthesized and secreted into the medium, where it causes a color change from yellow to red. This recombinant strain was used to determine whether representatives of major surfactant classes and some of their principal degradation products possess estrogenic activity. The results were compared to the effects of the main natural estrogen 17β-estradiol. None of the parent surfactants tested possessed estrogenic activity. However, one class of surfactants, the alkylphenol polyethoxylates, degrade to persistent metabolites that were weakly estrogenic. Another group of degradation products, the sulfophenyl carboxylates, which are derived from the biodegradation of linear alkylbenzene sulfonates, do not appear to possess estrogenic activity.
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We have utilized a validated (standardized) estrogen receptor (ER) competitive-binding assay to determine the ER affinity for a large, structurally diverse group of chemicals. Uteri from ovariectomized Sprague-Dawley rats were the ER source for the competitive-binding assay. Initially, test chemicals were screened at high concentrations to determine whether a chemical competed with [3H]-estradiol for the ER. Test chemicals that exhibited affinity for the ER in the first tier were subsequently assayed using a wide range of concentrations to characterize the binding curve and to determine each chemical's IC 50 and relative binding affinity (RBA) values. Overall, we assayed 188 chemicals, covering a 1 × 106-fold range of RBAs from several different chemical or use categories, including steroidal estrogens, synthetic estrogens, antiestrogens, other miscellaneous steroids, alkylphenols, diphenyl derivatives, organochlorines, pesticides, alkylhydroxybenzoate preservatives (parabens), phthalates, benzophenone compounds, and a number of other miscellaneous chemicals. Of the 188 chemicals tested, 100 bound to the ER while 88 were non-binders. Included in the 100 chemicals that bound to the ER were 4-benzyloxyphenol, 2,4-dihydroxybenzophenone, and 2,2′-methylenebis(4-chlorophenol), compounds that have not been shown previously to bind the ER. It was also evident that certain structural features, such as an overall ring structure, were important for ER binding. The current study provides the most structurally diverse ER RBA data set with the widest range of RBA values published to date.
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The carcinogenic potentials of 40 National Toxicology Program chemicals previously predicted by Computer Optimised Molecular Parametric Analysis for Chemical Toxicity (COMPACT), based on the identification of potential substrates of cytochromes P4501A and 2E (CYP1A and CYP2E), have been compared with new rodent carcinogenicity results. The COMPACT predictions have also been compared with published Ames mutagenicity data and with our own Hazardexpert predictions for carcinogenicity. Concordance evaluations between rodent carcinogenicity (1/4 segments positive) and predictions by COMPACT or Hazardexpert were 64% for COMPACT (CYP1A only), 72% for COMPACT (CYP1A plus CYP2E), 70% for Hazardexpert alone, and 86% for COMPACT (CYP1A plus CYP2E) plus Hazardexpert. Sensitivities of the predictions were for COMPACT, 75%; Hazardexpert, 60%; and Ames, 54%. Positive predictivities were for COMPACT, 75%; Hazardexpert, 78%; and Ames 81%. Negative predictivites were for COMPACT, 62%; Hazardexpert, 52%; and Ames, 42%.
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The estrogenic activity of dieldrin, toxaphene, and an equimolar mixture of both compounds (dieldrin/toxaphene) was investigated in the 21-day-old B6C3F1 mouse uterus, MCF-7 human breast cancer cells, and in yeast-based reporter gene assays. Treatment of the animals with 17beta-estradiol (E2) (0.0053 kg/day x3) resulted in a 3.1-, 4.8-, and 7.8-fold increase in uterine wet weight, peroxidase activity, and progesterone receptor binding, respectively. In contrast, treatment with 2.5, 15 and 60 micromol/kg (x3) doses of toxaphene, dieldrin, or dieldrin/toxaphene (equimolar) did not significantly induce a dose-dependent increase in any of the E2-induced responses. The organochlorine pesticides alone and the binary mixture did not bind to the mouse uterine estrogen receptor (ER) in a competitive binding assay using [3H]E2 as the radioligand. In parallel studies, estrogenic activities were determined in MCF-7 cells by using a cell proliferation assay and by determining induction of chloramphenicol acetyl transferase (CAT) activity in MCF-7 cells transiently transfected with plasmids containing estrogen-responsive 5'-promoter regions from the rat creatine kinase B and human cathepsin D genes. E2 caused a 24-fold increase in CAT activity in MCF-7 cells transiently transfected with creatine kinase B and a 3.8-fold increase in cells transiently transfected with the human cathepsin D construct. Treatment of MCF-7 cells with dieldrin, toxaphene, or an equimolar mixture of dieldrin plus toxaphene (10(-8)-10(-5) M) did not significantly induce cell proliferation or CAT activity in the transient transfection experiment with both plasmids. The relative competitive binding of the organochlorine pesticides was determined by incubating MCF-7 cells with 10(-9) M [3H]E2 in the presence or absence of 2 x 10(-7) M unlabeled E2 (to determine nonspecific binding), toxaphene (10(-5) M), dieldrin (10(-5) M), and equimolar concentrations of the dieldrin plus toxaphene mixture (10(-5) M). The binding observed for [3H]E2 in the whole cell extracts was displaced by unlabeled E2, whereas the organochlorine pesticides and binary mixture exhibited minimal to nondetectable competitive binding activity. E2 caused a 5000-fold induction of beta-galactosidase (beta-gal) activity in yeast transformed with the human ER and a double estrogen responsive element upstream of the beta-gal reporter gene. Treatment with 10(-6)-10(-4) M chlordane, dieldrin, toxaphene, or an equimolar mixture of dieldrin/toxaphene did not induce activity, whereas 10(-4) M endosulfan caused a 2000-fold increase in beta-gal activity. Diethylstilbestrol caused a 20-fold increase in activity in yeast transformed with the mouse ER and a single estrogen responsive element upstream of the beta-gal reporter gene. Dieldrin, chlordane, toxaphene, and endosulfan induced a 1.5- to 4-fold increase in activity at a concentration of 2.5 x 10(-5) M. Synergistic transactivation was not observed for any equimolar binary mixture of the pesticides at concentrations of either 2.5 x 10(-5) M or 2.5 x 10(-4) M. The results of this study demonstrate that for several estrogen-responsive assays in the mouse uterus, MCF-7 human breast cancer cells, and yeast-based reporter gene assays, the activities of both dieldrin and toxaphene were minimal, and no synergistic interactions were observed with a binary mixture of the two compounds.
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There is considerable public, regulatory, and scientific concern regarding human exposure to endocrine-disrupting chemicals, which include compounds that directly modulate steroid hormone receptor pathways (estrogens, antiestrogens, androgens, antiandrogens) and aryl hydrocarbon receptor (AhR) agonists, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds. Based on quantitative structure-activity relationships for both AhR and estrogen receptor (ER) agonists, the relative potency (RP) of individual compounds relative to a standard (e.g. TCDD and 17-beta-estradiol) have been determined for several receptor-mediated responses. Therefore, the TCDD or estrogenic equivalent (TEQ or EQ, respectively) of a mixture is defined as TEQ = sigma[T(i)]xRP(i)or EQ=sigma[E(i)]xRP(i), where T(i) and E(i) are concentrations of individual AhR or ER agonists in any mixture. This approach for risk assessment of endocrine-disrupting mixtures assumes that for each endocrine response pathway, the effects of individual compounds are essentially additive. This paper will critically examine the utility of the TEQ/EQ approach for risk assessment, the validity of the assumptions used for this approach, and the problems associated with comparing low dose exposures to xeno and natural (dietary) endocrine disruptors.
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We used a recombinant yeast estrogen assay to assess the activity of 73 phenolic additives that are used as sunscreens, preservatives, disinfectants, antioxidants, flavorings, or for perfumery. Thirty-two of these compounds displayed activity: 22 with potencies relative to 17beta-estradiol, ranging from 1/3,000 to < 1/3,000,000, and 10 compounds with an impaired response that could not be directly compared with 17beta-estradiol. Forty-one compounds were inactive. The major criteria for activity appear to be the presence of an unhindered phenolic OH group in a para position and a molecular weight of 140-250 Da.
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In view of the large differences between the concentrations of estrogenic chemicals needed to elicit effects in in vitro assays and their levels in human tissues, it is hard to explain possible health risks in terms of exposure to individual compounds. Human populations, however, are exposed to mixtures of estrogenic and estrogen-like agents and it is necessary to consider the impact of combined effects. We assessed the combined effects of 1-(o-chlorophenyl)-1-(p-chlorophenyl)-2,2,2-trichloroethane (o,p'-DDT), 2,2-bis(p-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE), beta-hexachlorocyclohexane (beta-HCH), and 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (p,p'-DDT) on the induction of cell proliferation in MCF-7 cells. All four compounds are persistent organochlorines that can be found in human tissues. We performed extensive concentration-response analyses with the single agents to predict the effects of two mixtures of all four compounds with different mixture ratios. We calculated the predictions by using the pharmacologically well-founded models of concentration addition and independent action and then tested them experimentally. o,p'-DDT, p,p'-DDE, beta-HCH, and p,p'-DDT acted together to produce proliferative effects in MCF-7 cells. The combined effect of the four agents could be predicted on the basis of data about single agent concentration-response relationships. Regression analysis demonstrated that there were combination effects even when each mixture component was present at levels at or below its individual no-observed-effect-concentration. We assessed combination effects in two ways: First, evaluations in relation to the proliferative responses induced by single mixture components revealed that the combination effects were stronger than the effects of the most potent constituent. Thus, according to this method of evaluation, the combined effects may be termed synergistic. Second, comparisons with the expected effects, as predicted by concentration addition and independent action, showed excellent agreement between prediction and observation. With this approach, the combined effect of all four compounds can be termed additive.
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This paper questions the usefulness of the no-observed-effect level (NOEL) as a summary statistic for ecotoxicological experiments. Quantification of the NOEL depends critically on size and variability of an experiment: smaller and less precise experiments lead to higher values for the NOEL, which gives the wrong signal to suppliers of a NOEL. The NOEL will generally lie in a dose range where possible effects cannot be excluded, even within the context of the experiment. Hence it does not form a suitable starting point for extrapolation to field situations. Alternative methods of finding a dose with a negligible effect are discussed. A two-step procedure is proposed that involves finding the dose whose effect is at most 25%, followed by linear extrapolation to a dose whose effect is acceptably small. The procedure leads to higher values if efforts are made to increase the power of the experiment.
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Some time ago, a multiple comparison procedure for comparing several treatments simultaneously with a control or standard treatment was introduced by the present author (Dunnett [1955]). The procedure was designed to be used either to test the significance of the differences between each of the treatments and the control with a stated value 1 - P for the joint significance level, or to set confidence limits on the true values of the treatment differences from the control with a stated value P for the joint confidence coefficient. Thus the procedure has the property of controlling the experimentwise, rather than the per-comparison, error rate associated with the comparisons, in common with the multiple comparison procedures of Tukey [unpublished] and Scheffe [1953]. In the earlier paper, tables were provided enabling up to nine treatments to be compared with a control with joint confidence coefficient either .95 or .99. Tables for both one-sided and two-sided comparisons were given but, as explained in the paper, the two-sided values were inexact for the case of more than two comparisons as a result of an approximation which had to be made in the computations. The main purpose of the present paper is to give the exact tables for making two-sided comparisons. The necessary computations were done on a General Precision LGP-30 electronic computer, by a method described in section 3 below. The tables are given here as Tables II and III; these replace Tables 2a and 2b, respectively, of the previous paper. In addition to providing the exact values, a method is given for adjusting the tabulated values to cover the situation where the variance of the control mean is smaller than the variance of the treatment means, as occurs for example when a greater number of observations is allocated to the control than to any of the test treatments. Furthermore, the number of treatments which may be simultaneously compared with a control has been extended to twenty. 482
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The prediction of combined effects based on the effects of the individual components of mixtures by using the pharmacological concepts of concentration addition and independent action might be a promising tool for the risk assessment of pollutant mixtures. To analyze and compare the predictive capabilities of the reference concepts for similarly acting chemicals, the overall toxicity of a multiple mixture was determined in a bioluminescence inhibition assay with Vibrio fischeri. The mixture was composed of 16 similarly and specifically acting chemicals, anticipated to have a common mode of action via weak acid respiratory uncoupling of oxidative phosphorylation. Results show that the observed mixture toxicity is rather well predicted by both concepts. Concentration addition shows an excellent predictive power; the median effective concentration (EC50) of the mixture is predicted with an error of about 10%. Independent action, in contrast, underestimates the EC50 of the mixture by a factor of a little more than three. With respect to risk assessment procedures, it may be concluded that concentration addition gives a valid estimation of the overall toxicity for multiple mixtures with similar and specific mechanisms of action of the mixture components in this type of biotest.
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Chronic aquatic toxicity test results are commonly analyzed with statistical hypothesis tests to generate summary statistics known as the no-observed-effect concentration (NOEC) and first-observed-effect concentration (FOEC). These procedures address statistical differences among treatments but suffer several critical limitations. Use of concentration-response statistics to estimate minimal effect concentrations (i.e., EC values) from quantal and continuous data has advantages over a hypothesis-testing approach for generating a biologically relevant end point and an estimate of variability from toxicity tests. Estimation of the concentration-response statistic (EC, effective concentration) for continuous data is not straightforward but is possible with a variety of approaches. A statistical method for estimating EC values described here is based on a nonlinear regression estimation procedure. The usefulness of this method is demonstrated with continuous data from chronic toxicity tests with algae, fish, and invertebrate populations.
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Acclimation to toxicants should be studied in detail for representative pollutants.There is a great deal of information on relative resistance of different species of fish but it needs summarizing. A trend towards use of ‘standard’ fish species in research is good. With invertebrates and algae, as much as with fish, tests of sublethal effects such as growth and development are often more meaningful than tests of acute toxicity.Chemical autopsy methods seem promising, more so than histopathological approaches, which suffer from practical difficulties in field situations.RésuméMaintenant il est possible de prédire la toxicité d'un mélange de deux ou plusieurs polluants sur la base de mesurages chimiques. Les toxicités des composants individuels sont additionnées comme fractions du naissantlc50 (seuil de concentration léthale). La toxicité totale du mélange est exprimée comme un seul nombre. 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Une tendance vers l'utilisation des espèces de poissons “standard” est bonne. Avec les invertébrés et les algues autant qu'avec les poissons, les tests des effets sous-léthals, comme la croissance et le développement, sont souvent plus significatifs que les tests de toxicité aigue.Les méthodes d'autopsie chimique paraissent prometteuses, même plus que les abords histopathologiques, qui souffrent à cause de difficultés pratiques dans les situations sur le terrain.ZusammenfassungMan ist heutezutage imstande, Toxizität in Gemischen bestehend aus zwei oder mehreren Verunreinigern auf Grundlage von chemischen Messungen vorauszusagen. Die Toxizitäten von einzelnen Bestandteilen werden als Fraktionen des Anfangsstadiums “lc50” (Todesschwellenkonzentration) zusammengezählt. Vollständige Toxizität einer Mischung wird als eine einzige Zahl ausgedrückt. Es wird eine Standardterminologie für die Wirkungen von zwei oder mehreren Giftstoffen, die gleichzeitig in Aktion treten, aufgestellt.Modifizierende Umstände (wie Temperatur, Die Härte des Wassers, u.s.w.) haben grossen Einfluss auf die Toxizität. Es sollte viel fragmentarische Information zusammengetragen und auf zugrundeliegende Beispielsformen untersucht werden. Prägnante Zusammenfassungen über die Schätzung der modifizierenden Effekte wurden über die Regenbogenforelle veröffentlicht. Durch Komputer erzielte, sehr abwandlungsfähige Analysen sind vielversprechend, besonders für Studien über sublethale Toxizität. Die Wirkung von fluktuierenden Giftstoffkonzentrationen kann mittels vier approximativen Methoden geschätzt werden; die theore tische Grundlage zum Verständnis der Wirkung scheint noch immer unbewiesen. Akklimatisierung an Giftstoffe sollte genauest an repräsentativen Verunreinigern studiert werden.Es liegt viel Information über den relativen Widerstand von verschiedenen Fischarten vor; diese muss jedoch zusammengefasst werden. Der Trend, für Forschung “Standard”-Fischarten zu verwenden, ist gut. Bei wirbellosen Tieren und Algen sowie auch bei Fischen sind Tests über die sublethale Wirkung, wie Wuchs und Entwicklung, oft vielbedeutender als Tests über akute Toxizität.Chemische Autopsiemethoden scheinen vielversprechend, besser als histopathologische Angriffsmethoden, die bei Aussenstudien praktischen Schwierigkeiten unterliegen.
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There are concerns about possible combination effects of environmental chemicals with oestrogenic activity and their implications for human health. Such chemicals are present in complex mixtures in our environment. A number of studies searching for possible synergistic interactions between xenoestrogens have appeared in the literature. However, in these studies no account was taken of established concepts and methods for analysing combination effects. In the present review, we highlight conceptual issues which may be useful for a sound analysis of the effects of mixtures of xenoestrogens. We find that much published work suffers from an undue focus on measuring effects of mixtures at only one dose level. Assessments of combination effects are frequently complicated by a lack of information on dose–response relationships. Some studies which purportedly show absence of synergy have in fact overlooked synergisms.
Article
A promising tool for the risk assessment of chemical mixtures is the prediction of their toxicities from the effects of the individual components. For that purpose, concentration addition is uniformly regarded as valid for mixtures of similarly acting chemicals. Whether this concept or the competing notion of independent action is more appropriate for mixtures of dissimilarly acting chemicals is still in dispute. Therefore, the presented study analyzed and compared the predictive capabilities of both concepts for a multiple mixture designed of strictly dissimilarly acting compounds. Experimental investigations were conducted using a long-term bioluminescence inhibition assay with Vibrio fischeri. Results show an excellent predictive power of independent action, while concentration addition overestimates the mixture toxicity. Thus, the precise prediction of mixture toxicities depends on a valid assessment of the similarity/dissimilarity of the mixture components. However, concentration addition underestimates the EC50 of the mixture only by a factor of less than three. As the similarity of components is often unknown for mixtures found in the environment, it is concluded that concentration addition may give a realistic worst case estimation of mixture toxicities for risk assessment procedures.
Article
The assessment of the combined effects of substances is usually based on one of two different concepts: concentration addition or independent action. Both concepts are founded on different pharmacological assumptions about sites and modes of actions of substances, but in toxicology and ecotoxicology such knowledge is rare for most chemicals. In order to validate experimental results and to allow for precautions assessments, the quantitative relationships between concentration addition and independent action are therefore of interest. In this paper, we derive for the Weibull, the logistic, and the normal distribution functions the concentrations where the response probability due to concentration addition exceeds that due to independent action and vice versa. This is done (a) by analytically comparing both models for low and high mixture concentrations and (b) by numerically calculating the response probabilities when concentration addition and independent action agree. It is shown that the relationships between the models for joint action depend on the distribution functions, the corresponding slope parameters, and on the mixture concentrations administered.
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Halogenated aromatic compounds, typified by the polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), biphenyls (PCBs), and diphenylethers (PCDEs), are industrial compounds or byproducts which have been widely identified in the environment and in chemical-waste dumpsites. Halogenated aromatics are invariably present in diverse analytes as highly complex mixtures of isomers and congeners and this complicates the hazard and risk assessment of these compounds. Several studies have confirmed the common receptor-mediated mechanism of action of toxic halogenated aromatics and this has resulted in the development of structure-activity relationships for this class of chemicals. The most toxic halogenated aromatic is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and based on in vivo and in vitro studies the relative toxicities of individual halogenated aromatics have been determined relative to TCDD (i.e., toxic equivalents). The derived toxic equivalents can be used for hazard and risk assessment of halogenated aromatic mixtures; moreover, for more complex mixtures containing congeners for which no standards are available (e.g., bromo/chloro mixtures), several in vitro or in vivo assays can be utilized for hazard or risk assessment.
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Certain chemicals in the environment are estrogenic. The low potencies of these compounds, when studied singly, suggest that they may have little effect on biological systems. The estrogenic potencies of combinations of such chemicals were screened in a simple yeast estrogen system (YES) containing human estrogen receptor (hER). Combinations of two weak environmental estrogens, such as dieldrin, endosulfan, or toxaphene, were 1000 times as potent in hER-mediated transactivation as any chemical alone. Hydroxylated polychlorinated biphenyls shown previously to synergistically alter sexual development in turtles also synergized in the YES. The synergistic interaction of chemical mixtures with the estrogen receptor may have profound environmental implications. These results may represent a previously uncharacterized level of regulation of estrogen-associated responses.
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I write to formally withdraw the report “Synergistic activation of estrogen receptor with combinations of environmental chemicals” ([7 June 1996, p. 1489][1]) ([1][2]), for which I was corresponding author. We have conducted experiments duplicating the conditions of our earlier work, but have
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Chemicals that act as androgen receptor (AR) agonists and antagonists or inhibit fetal steroidogenesis can induce reproductive malformations in humans and laboratory animals. Several environmental chemicals disrupt development in rats and/or rabbits at fetal concentrations at, or near, exposure levels seen in some segments of the human population. In rats, fetal tissues concentrations of 10-20 p.p.m. of the DDT metabolite, p,p'-DDE, are correlated with reproductive abnormalities in male offspring. These concentrations are similar to those measured in first-trimester human fetal tissues in the late 1960s. The pesticides vinclozolin, procymidone, linuron and DDT are AR antagonists. They reduce male rat anogenital distance, and induce areolas at relatively low dosages. Hypospadias, agenesis of the sex accessory tissues and retained nipples are seen in the middle dosages, while undescended testes and epididymal agenesis are seen in the highest doses. Phthalate esters (PE) inhibit testosterone synthesis during fetal life, but do not appear to be AR antagonists. Prenatal administration of a single low dose of dioxin (50-1,000 ng TCDD/kg) alters the differentiation of androgen-dependent tissues at p.p.t. concentrations, but the mechanism of action likely involves interaction with a hormone-like nuclear transcription factor, the hormone-like receptor AhR, rather than AR. p,p'-DDT and p,p'-DDE, vinclozolin and di-n-butyl phthalate affect reproductive function in rabbits when administered during prenatal and/or neonatal life. Cryptorchidism and carcinoma in situ-like (CIS) testicular lesions were seen in male rabbits treated during development with p,p'-DDT or p,p'-DDE. Extrapolation of effects from rodents to humans would be enhanced if future studies incorporate determination of tissue concentrations of the active metabolites. Knowledge of the tissue concentrations of the active toxicants also would provide an important link to in-vitro studies, which provide more useful mechanistic information when they are executed at relevant concentrations.
Article
Experiments were conducted to assess the in vivo potency of binary mixtures of estrogenic chemicals using plasma vitellogenin (VTG) concentrations in juvenile rainbow trout (Oncorhynchus mykiss) as the endpoint. The estrogenic potencies of estradiol-17beta (E2), 4-tertnonylphenol (NP), and methoxychlor (MXC) were determined following 14 day exposures to the individual chemicals and binary mixtures of these chemicals. E2, NP, and MXC all induced concentration dependent increases in plasma VTG, with lowest observed effect concentrations of 4.7 and 7.9 ng L(-1) for E2, 6.1 and 6.4 microg L(-1) for NP, and 4.4 and 6.5 microg L(-1) for MXC. Concentration-response curves for fixed ratio binary mixtures of E2 and NP (1:1000), E2 and MXC (1:1000), and NP and MXC (1:1) were compared to those obtained for the individual chemicals, using the model of concentration addition. Mixtures of E2 and NP were additive at the concentrations tested, but mixtures of E2 and MXC were less than additive. This suggests that while NP probably acts via the same mechanism as E2 in inducing VTG synthesis, MXC may be acting via a different mechanism(s), possibly as a result of its conversion to HPTE which is an estrogen receptor alpha agonist and an estrogen receptor beta antagonist. It was not possible to determine whether mixtures of MXC and NP were additive using VTG induction, because the toxicity of MXC restricted the effect range forwhich the expected response curve forthe binary mixture could be calculated. The data presented illustrate that the model of concentration addition can accurately predict effects on VTG induction, where we know that both chemicals act via the same mechanism in mediating a vitellogenic response.
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