Mixture Effects of Estrogenic Pesticides at the Human Estrogen Receptor α and β

Development of a deep neural network model based on high throughput screening data for predicting synergistic estrogenic activity of binary mixtures for consumer products

A paradigm of chemical risk assessment is continuously extending from focusing on 'single substances' to more comprehensive approaches that examines the combined toxicity among different components in 'mixtures.' This change aims to account for the cocktail effect arising from the toxicological interactions in mixtures, which can lead to increased risks. More than 1000 potential endocrine-disrupting chemicals (EDCs) have been reported, and they can be included in different industrial and consumer chemical products and released to the environment as pollutants of emerging environmental concern. Although extensive studies involving both experiments and predictions have investigated individual EDCs, predictions of their synergistic effects are still relatively lacking, an area that requires further investigation. In this study, we extensively investigated substances in consumer products, mainly marketed in South Korea, that might exhibit estrogenic activity or reproductive toxicity. A high throughput screening (HTS) assay based on OECD Test Guideline 455 for hERαHeLa-9903 cells was constructed, and 435 substances were screened using the HTS. Thirty-five (potential) estrogenic agonists were selected, and their 1412 binary mixtures that could be prepared in four different ratios were systematically tested, considering the available effective concentrations of substances and the solubility of their resulting mixtures. The best empirical dose-response curves of 35 substances and 917 mixtures were derived in this study. Based on the HTS data, a deep neural network model was developed (area under the curve (AUC): 0.837-0.881) and compared with a random forest model (AUC: 0.656-0.829) to screen for the synergistic estrogenic activity of binary mixtures.

Non-target estrogenic screening of 60 pesticides, six plant protection products, and tomato, grape, and wine samples by planar chromatography combined with the planar yeast estrogen screen bioassay

For non-target residue analysis of xenoestrogens in food, sophisticated chromatographic-mass spectrometric techniques lack in biological effect detection. Various in vitro assays providing sum values encounter problems when opposing signals are present in a complex sample. Due to physicochemical signal reduction, cytotoxic or antagonistic effect responses, the resulting sum value is falsified. Instead, the demonstrated non-target estrogenic screening with an integrated planar chromatographic separation differentiated opposing signals, detected and prioritized important estrogenic compounds, and directly assigned tentatively the responsible compounds. Sixty pesticides were investigated, ten of which showed estrogenic effects. Exemplarily, half-maximal effective concentrations and 17β-estradiol equivalents were determined. Estrogenic pesticide responses were confirmed in six tested plant protection products. In food, such as tomato, grape, and wine, several compounds with an estrogenic effect were detected. It showed that rinsing with water was not sufficient to remove selected residues and illustrated that, though not usually performed for tomatoes, peeling would be more appropriate. Though not in the focus, reaction or breakdown products that are estrogenic were detected, underlining the great potential of non-target planar chromatographic bioassay screening for food safety and food control.

Characterization of childhood exposure to environmental contaminants using stool in a semi-urban middle-class cohort from eastern Canada

Children are exposed to various environmental organic and inorganic contaminants with effects on health outcomes still largely unknown. Many matrices (e.g., blood, urine, nail, hair) have been used to characterize exposure to organic and inorganic contaminants. The sampling of feces presents several advantages; it is non-invasive and provides a direct evaluation of the gut microbiome exposure to contaminants. The gut microbiome is a key factor in neurological development through the brain-gut axis. Its composition and disturbances can affect the neurodevelopment of children. Characterization of children exposure to contaminants is often performed on vulnerable populations (e.g., from developing countries, low-income neighborhoods, and large urban centers). Data on the exposure of children from middle-class, semi-urban, and mid-size populations to contaminants is scarce despite representing a significant fraction of the population in North America. In this study, 73 organics compounds from different chemical classes and 22 elements were analyzed in 6 years old (n = 84) and 10 years old (n = 119) children's feces from a middle-class, semi-urban, mid-size population cohort from Eastern Canada. Results show that 67 out of 73 targeted organics compounds and all elements were at least detected in one child's feces. Only caffeine (97% & 80%) and acetaminophen (28% & 48%) were detected in more than 25% of the children's feces, whereas all elements besides titanium were detected in more than 50% of the children.

Hormone receptor activities of complex mixtures of known and suspect chemicals in personal silicone wristband samplers worn in office buildings

Humans are exposed to increasingly complex mixtures of hormone-disrupting chemicals from a variety of sources, yet, traditional research methods only evaluate a small number of chemicals at a time. We aimed to advance novel methods to investigate exposures to complex chemical mixtures. Silicone wristbands were worn by 243 office workers in the USA, UK, China, and India during four work shifts. We analyzed extracts of the wristbands for: 1) 99 known (targeted) chemicals; 2) 1000+ unknown chemical features, tentatively identified through suspect screening; and 3) total hormonal activities towards estrogen (ER), androgen (AR), and thyroid hormone (TR) receptors in human cell assays. We evaluated associations of chemicals with hormonal activities using Bayesian kernel machine regression models, separately for targeted versus suspect chemicals (with detection ≥50%). Every wristband exhibited hormonal activity towards at least one receptor: 99% antagonized TR, 96% antagonized AR, and 58% agonized ER. Compared to men, women were exposed to mixtures that were more estrogenic (180% higher, adjusted for country, age, and skin oil abundance in wristband), anti-androgenic (110% higher), and complex (median 836 detected chemical features versus 780). Adjusted models showed strong associations of jointly increasing chemical concentrations with higher hormonal activities. Several targeted and suspect chemicals were important co-drivers of overall mixture effects, including chemicals used as plasticizers, fragrance, sunscreen, pesticides, and from other or unknown sources. This study highlights the role of personal care products and building microenvironments in hormone-disrupting exposures, and the substantial contribution of chemicals not often identifiable or well-understood to those exposures.

Multiplex planar bioassay detecting estrogens, antiestrogens, false-positives and synergists as sharp zones on normal phase

BACKGROUND

Phytoestrogens are found in many plants used in traditional medicines. Increasingly, plant extracts (botanicals) are also being added to foods or marketed as dietary supplements. Especially such powder formulations are susceptible to adulteration and falsification, given the global processing chain. To detect estrogen-like compounds in such multicomponent mixtures, non-target screening for hormonally active or endocrine disrupting compounds in plant products is becoming more important. Unfortunately, the current planar yeast estrogen screen (pYES) is prone to zone diffusion on the normal-phase high-performance thin-layer chromatography (NP-HPTLC) plate due to long incubation times in the aqueous bioassay.

PURPOSE

The present study aimed to reduce zone diffusion on NP plates, which provides the basis for extending pYES to a multiplex bioassay, offering 4 different biological activity principles, followed by targeted identification of active zones.

STUDY DESIGN AND METHODS

The reduction of substance diffusion via a polyisobutyl methacrylate polymer coating was studied. After successful zone fixation (^fix), a multiplex bioassay was developed, in which a 17β-estradiol-strip was applied along each sample track to detect synergists and antagonists (A), and for verification (V), a 4-methyl umbelliferone-strip to exclude false-positives. After multiplex bioassay screening of 68 botanicals, the zones with hormonal activities were heart-cut eluted to reversed-phase high-performance liquid chromatography-diode array detection-high-resolution tandem mass spectrometry (RP-HPLC-DAD-HESI-HRMS/MS).

RESULTS

The separated substances were successfully fixed by the chromatogram coating. The zone sharpness (achieved after the bioassay) made it possible to add two strips, the 17β-estradiol-strip for antagonistic and synergistic, and the 4-methyl umbelliferone-strip for false-positive effect detection, resulting in a multiplex bioassay. Using the 12D hyphenation NP-HPTLC^fix-UV/Vis/FLD-pYAVES-FLD heart-cut RP-HPLC-DAD-HESI-HRMS/MS, it was possible to obtain information on estrogens, antiestrogens, false-positives, and synergists, and (tentatively) assign 17 hormonally active compounds, of which only 7 have been known to affect the human estrogen receptor, while another 4 had structural similarity to common phytoestrogens and antiestrogens.

CONCLUSIONS

The streamlined 12D hyphenation including a multiplex bioassay has been shown to differentiate hormonal effects, leading to new insights and better understanding. It can generally be used to identify unknown hormonally active compounds in complex samples.

Appraisal for Edible Use of Vegetable Crops Cultivated in Egypt after Treatment with Selected Insecticides and Fungicides: Insights of Dissipation Rates and Pre-harvest Intervals

An analytical investigation was carried out to study the dissipation rate of two commonly used pesticides, thiamethoxam (neonicotinoid insecticide) and propamocarb hydrochloride (carbamate fungicide), applied to four vegetable crops: cucumber, zucchini, lettuce and pepper, after open-field application. Samples were harvested according to a scheduled plan followed by QuEChERS extraction, then thiamethoxam residues were analyzed using a GC-ECD method, while propamocarb HCl residues were analyzed using an HPLC-UV method. Validation parameters were attained for both methods and the kinetic profile was studied, which fitted the first-order kinetics where k, t_1/2 and t₉₀ were calculated. The proper pre-harvest interval (PHI) was studied for each crop to ensure that the residues levels declined to reach below the maximum residue limit (MRL) where the crop is suitable for consumption. These values were found to be different from labelled values, which proves that the PHIs are greatly affected by changing weather conditions.

How to use statistics to claim antagonism and synergism from binary mixture experiments

We review statistical approaches applicable for the analysis of data from binary mixture experiments, which are commonly used in pesticide science for evaluating antagonistic or synergistic effects. Specifically, two different situations are reviewed, one where every pesticide is only available at a single dose level and a mixture simply combines these doses, and one where the pesticides and their mixture are used at increasing doses. The former corresponds to using factorial designs whereas the latter corresponds to fixed-ratio designs. We consider dose addition and independent action as references for lack of antagonistic and synergistic effects. Data from factorial designs should be analyzed using two-way analysis of variance models whereas data from fixed-ratio designs should be analyzed using non-linear dose-response analysis. In most cases, independent action seems the more natural choice for factorial designs. In contrast, dose addition is more appropriate for fixed-ratio designs although dose addition is not equally compatible with all types of dose-response data. Fixed-ratio designs should be preferred as they allow validation of the assumed dose-response relationship and, consequently, provide much stronger claims about antagonistic and synergistic effects than factorial designs. Finally, it should be noted that, in any case, simple ways of summarizing pesticide mixture effects may come at the price of more or less restrictive modeling assumptions. © 2021 Society of Chemical Industry.

Cytotoxicity and estrogenicity in simulated dental wastewater after grinding of resin-based materials

OBJECTIVE

This study evaluated the cytotoxic and estrogenic effects of dust and eluates released into simulated wastewater after grinding of dental resin-based materials.

METHODS

Four materials were used: ceram.x® universal, Filtek™ Supreme XTE, Lava™ Ultimate and Core-X™ flow. From each composite material, samples (5 × 2 mm, n = 50) were prepared according to the manufacturers' instructions. Lava™ Ultimate was used as blocks. All samples were ground to dust with a diamond bur (106 μm) and suspended in distilled water at 60 mg/mL. After storage for 72 h, the suspensions were separated into a soluble (eluate) and a particulate (dust) fraction. Eluates and dusts were evaluated for inhibition of Vibrio fischeri bioluminescence and cytotoxicity on human A549 lung cells (WST-1-Assay). The estrogenic activity was assessed by YES-Assay using Saccharomyces cerevisiae. Additionally, dental monomers (BisGMA, BisEMA, UDMA, TEGDMA, HEMA) and Bisphenol A were investigated.

RESULTS

All eluates showed inhibition of V. fischeri bioluminescence at concentrations above 1.1 mg/mL (p < 0.05). The activity of the eluates of ceram.x® universal and Filtek™ Supreme XTE was significantly higher than Lava™ Ultimate and Core-X™ flow (p < 0.05). In the WST-1-Assay, all materials induced cytotoxic effects at concentrations of 0.1 mg/mL (p < 0.05), while no significant differences were detected among them. The tested materials revealed no estrogenic activity. All dental monomers and Bisphenol A showed concentration dependent cytotoxic effects (p < 0.05), whereas only Bisphenol A induced an estrogenic effect (p < 0.01).

SIGNIFICANCE

Dust and eluates of resin-based dental materials released into wastewater exert bactericidal and cytotoxic effects in vitro. However, they reveal no estrogenic effect.

2D Ti3C2Tx flakes prepared by in-situ HF etchant for simultaneous screening of carbamate pesticides

Present work reports preparation of colloidal single/few layer Ti₃C₂T_x MXene flakes using minimally intensive layer delamination (MILD) method for rapid electroanalytical screening of carbamate pesticides. Lithium fluoride salt and hydrochloric acid (7.5 M LiF/9M HCl) was used to produce in-situ generated HF as etchant to remove Al successfully from Ti₃AlC₂ MAX phase. Unlike the clay method (5 M LiF/6M HCl), this methodology simplified Ti₃C₂T_x synthesis protocol resulting in Li⁺ ions intercalated Ti₃C₂T_x which was delaminated without further sonication. The delaminated Ti₃C₂T_x flakes were found to be single/few layered sheets with mostly -OH and -O terminated surface groups. The characteristic 002 peak observed in X-ray diffraction (XRD) at 2θ = 6.4° with interplaner distance of 1.1137 nm suggested broadening of the peak attributed to the presence of Li⁺ ions between Ti₃C₂T_x flakes. Delaminated Ti₃C₂T_x flakes were utilized as working electrode which demonstrated simultaneous and selective detection of carbamate pesticides methiocarb and diethofencarb by voltammetry. The oxidation peaks of the two pesticides were well separated by a potential difference of 0.35 V in 0.5 M H₂SO₄ and DPV detection limits were calculated as 0.19 μg mL^-1 and 0.46 μg mL^-1 for methiocarb and diethofencarb respectively. Ti₃C₂T_x flakes as electrochemical sensor exhibited long term stability and acceptable recoveries in real sample for environmental applications.

Testing the low dose mixtures hypothesis from the Halifax project

In 2013, 60 scientists, representing a larger group of 174 scientists from 26 nations, met in Halifax, Nova Scotia to consider whether - using published research - it was logical to anticipate that a mixture of chemicals, each thought to be non-carcinogenic, might act together in that mixture as a virtual carcinogen. The group identified 89 such chemicals, each one affecting one or more Hallmark(s) - collectively covering all Hallmarks of Cancer - confirming the possibility that a chemical mixture could induce all the Hallmarks and function as a virtual carcinogen, thereby supporting the concern that chemical safety research that does not evaluate mixtures, is incomplete. Based on these observations, the Halifax Project developed the Low-Dose Carcinogenesis Hypothesis which posits "…that low-dose exposures to [mixtures of] disruptive chemicals that are not individually carcinogenic may be capable of instigating and/or enabling carcinogenesis." Although testing all possible combinations of over 80,000 chemicals of commerce would be impractical, prudence requires designing a methodology to test whether low-dose chemical mixtures might be carcinogenic. As an initial step toward testing this hypothesis, we conducted a mini review of published empirical observations of biological exposures to chemical mixtures to assess what empirical data exists on which to base future research. We reviewed studies on chemical mixtures with the criteria that the studies reported both different concentrations of chemicals and mixtures composed of different chemicals. We found a paucity of research on this important question. The majority of studies reported hormone related processes and used chemical concentrations selected to facilitate studying how mixtures behave in experiments that were often removed from clinical relevance, i.e., chemicals were not studied at human-relevant concentrations. New research programs must be envisioned to enable study of how mixtures of small doses of chemicals affect human health, starting, when at all possible, from non-malignant specimens when studies are done in vitro. This research should use human relevant concentrations of chemicals, expand research beyond the historic focus on endocrine endpoints and endocrine related cancers, and specifically seek effects that arise uniquely from exposure to chemical mixtures at human-relevant concentrations.

Differential interactions of carbamate pesticides with drug transporters

Pesticides are now recognised to interact with drug transporters, but only few data are available on this issue for carbamate pesticides, a widely used class of agrochemicals, to which humans are highly exposed. The present study was therefore designed to determine whether four representative carbamate pesticides, i.e. the insecticides aminocarb and carbofuran, the herbicide chlorpropham and the fungicide propamocarb, may impair activities of main drug transporters implicated in pharmacokinetics. The interactions of carbamates with solute carrier and ATP-binding cassette transporters were investigated using cultured transporter-overexpressing cells, reference substrates and spectrofluorimetry-, liquid chomatography/tandem mass spectrometry- or radioactivity-based methods. Aminocarb and carbofuran exerted no or minimal effects on transporter activities, whereas chlorpropham inhibited BCRP and OAT3 activities and propamocarb decreased those of OCT1 and OCT2, but cis-stimulated that of MATE2-K. Such alterations of transporters however required chlorpropham/propamocarb concentrations in the 5-50 µM range, likely not relevant to environmental exposure. Trans-stimulation assays and propamocarb accumulation experiments additionally suggested that propamocarb is not a substrate for OCT1, OCT2 and MATE2-K. These data indicate that some carbamate pesticides can interact in vitro with some drug transporters, but only when used at concentrations higher than those expected to occur in environmentally exposed humans.

In vitro estrogenic activity of binary and multicomponent mixtures with bisphenol A

Bisphenol A and its analogs are environmental contaminants with well known estrogenic and anti-androgenic activities. In studies of human biomonitoring, simultaneous exposure to multiple bisphenols was shown in different biological samples, at picomolar to low nanomolar concentrations. Evaluation of their combined toxicities will therefore be a more realistic and reliable predictor for estimation of health risks than evaluation of only the single chemicals. In the present study, estrogenic activities of individual bisphenols were evaluated, along with their binary and multicomponent mixtures including three- and four-component mixtures, using the Organisation for Economic Co-operation and Development validated transactivation assay with the hERα-Hela9903 cell line. Concentration-dependent estrogenic activity was confirmed for all of the tested bisphenols, in the nanomolar to micromolar range. Estrogenic activities of binary and multicomponent mixtures followed a concentration addition model. Although exposure to individual bisphenols remains below their effective doses, we demonstrate that as a mixture, they can contribute additively to toxicity. This study thus emphasizes the importance of mixture toxicity evaluation for risk assessment of compounds that act like the bisphenols.

Mechanisms of action of agrochemicals acting as endocrine disrupting chemicals

Agrochemicals represent a significant class of endocrine disrupting chemicals that humans and animals around the world are exposed to constantly. Agrochemicals can act as endocrine disrupting chemicals through a variety of mechanisms. Recent studies have shown that several mechanisms of action involve the ability of agrochemicals to mimic the interaction of endogenous hormones with nuclear receptors such as estrogen receptors, androgen receptors, peroxisome proliferator activated receptors, the aryl hydrocarbon receptor, and thyroid hormone receptors. Further, studies indicate that agrochemicals can exert toxicity through non-nuclear receptor-mediated mechanisms of action. Such non-genomic mechanisms of action include interference with peptide, steroid, or amino acid hormone response, synthesis and degradation as well as epigenetic changes (DNA methylation and histone modifications). This review summarizes the major mechanisms of action by which agrochemicals target the endocrine system.

Overview of the effects of chemical mixtures with endocrine disrupting activity in the context of real-life risk simulation: An integrative approach (Review)

Research over the past years has indicated that chronic human exposure to very low doses of various chemical species in mixtures and administered via different routes (percutaneous, orally, etc.) should be the main focus of new biochemical and toxicological studies. Humans have daily contact with various chemicals, such as food additives, pesticides from fruits/vegetables, antibiotics (and other veterinary drugs) from meat, different types of preservatives from cosmetics, to name a few. Simultaneous exposure to this wide array of chemicals does not produce immediate effects, but summative effect/s over time that may be clinically manifested several years thereafter. Classical animal studies designed to test the toxic outcome of a single chemical are not suitable to assess, and then extrapolate to humans, the effects of a whole mixture of chemicals. Testing the aftermath of a combination of chemicals, at low doses, around or below the no observed adverse effect is stressed by many toxicologists. Thus, there is a need to reformulate the design of biochemical and toxicological studies in order to perform real-life risk simulation. This review discuss the potential use of computational methods as a complementary tool for in vitro and in vivo toxicity tests with a high predictive potential that could contribute to reduce animal testing, cost and time, when assessing the effects of chemical combinations. This review focused on the use of these methods to predict the potential endocrine disrupting activity of a mixture of chemicals.

Assessment of mixture toxicity of (tri)azoles and their hepatotoxic effects in vitro by means of omics technologies

Consumers are constantly exposed to chemical mixtures such as multiple residues of different pesticides via the diet. This raises questions concerning potential combination effects, especially because these substances are tested for regulatory purposes on an individual basis. With approximately 500 active substances approved as pesticides, there are too many possible combinations to be tested in standard animal experiments generally requested for regulatory purposes. Therefore, the development of in vitro tools and alternative testing strategies for the assessment of mixture effects is extremely important. As a first step in the development of such in vitro tools, we used (tri)azoles as model substances in a set of different cell lines derived from the primary target organ of these substances, the liver (human: HepaRG, rat: H4IIE). Concentrations were reconciled with measured tissue concentrations obtained from in vivo experiments to ensure comparable effect levels. The effects of the substances were subsequently analyzed by transcriptomics and metabolomics techniques and compared to data from corresponding in vivo studies. The results show that similar toxicity pathways are affected by substances and combinations, thus indicating a similar mode of action and additive effects. Two biomarkers obtained by the approach, CAR and Cyp1A1, were used for mixture toxicity modeling and confirmed the concentration-additive effects, thus supporting the selected testing strategy and raising hope for the development of in vitro methods suitable to detect combination effects and prioritize mixtures of concern for further testing.

The gut microbiome and aquatic toxicology: An emerging concept for environmental health

The microbiome plays an essential role in the health and onset of diseases in all animals, including humans. The microbiome has emerged as a central theme in environmental toxicology because microbes interact with the host immune system in addition to its role in chemical detoxification. Pathophysiological changes in the gastrointestinal tissue caused by ingested chemicals and metabolites generated from microbial biodegradation can lead to systemic adverse effects. The present critical review dissects what we know about the impacts of environmental contaminants on the microbiome of aquatic species, with special emphasis on the gut microbiome. We highlight some of the known major gut epithelium proteins in vertebrate hosts that are targets for chemical perturbation, proteins that also directly cross-talk with the microbiome. These proteins may act as molecular initiators for altered gut function, and we propose a general framework for an adverse outcome pathway that considers gut dysbiosis as a major contributing factor to adverse apical endpoints. We present 2 case studies, nanomaterials and hydrocarbons, with special emphasis on the Deepwater Horizon oil spill, to illustrate how investigations into the microbiome can improve understanding of adverse outcomes. Lastly, we present strategies to functionally relate chemical-induced gut dysbiosis with adverse outcomes because this is required to demonstrate cause-effect relationships. Further investigations into the toxicant-microbiome relationship may prove to be a major breakthrough for improving animal and human health. Environ Toxicol Chem 2018;37:2758-2775. © 2018 SETAC.

Endocrine disrupting potency of organic pollutant mixtures isolated from commercial fish oil evaluated in yeast-based bioassays

The aim of this work was to evaluate the activity of xenobiotic mixtures containing persistent organic pollutants isolated from commercial fish oil samples against sex hormone receptors, including estrogen and androgen. The applied bioassay was based on transgenic yeast strains. The mixtures were extracted from the samples using the semi-permeable membrane dialysis technique and analyzed with gas chromatography/ion trap mass spectrometry. It turned out that mixtures of chemicals isolated from fish oil may interact with human steroid sex hormone receptors in various ways: the tested samples showed both estrogenic and anti-androgenic activity. Calculated 17β-estradiol equivalents for the tested samples ranged between 0.003 and 0.073 pg g-1 (fat). Anti-androgenic activity expressed as the flutamide equivalent concentration was in the 18.58-216.21 ng g-1 (fat) range. Polychlorinated biphenyls and various DDT metabolites were the main fish oil pollutants influencing the receptors. Additivity and/or synergy between chemicals was observed in the ER/AR mediated response.

Climate variability, perceptions and political ecology: Factors influencing changes in pesticide use over 30 years by Zimbabwean smallholder cotton producers

Pesticides represent a potential public health hazard of note in farming communities. Accumulating evidence indicates that some pesticides used in agriculture act as hormone disrupters, with the potential to result in chronic health effects. Despite such a growing evidence base, pesticides remain the preferred method of pest control in agriculture worldwide. In many parts of Sub-Saharan Africa, usage is on the increase. This qualitative study assessed changes in the usage of pesticides by Zimbabwean smallholder cotton farmers in the past 30 years. Farmers reported an increase in the usage of pesticides, specifically insecticides, since the early 1980s. An increase in pest populations was also reported. The findings suggested a bi-directional causal relationship between the increase in pest population and the increase in pesticide use. Factors which emerged to have collectively impacted on the changes include climate variability, limited agency on the part of farmers, power dynamics involving the government and private cotton companies and farmers' perceptions and practices. An Integrated Pest Management Policy for Zimbabwe is recommended to facilitate integration of chemical controls with a broad range of other pest control tactics. Continuous farmer education and awareness raising is further recommended, since farmers' perceptions can influence their practices.

Investigation of the presence and endocrine activities of pesticides found in wastewater effluent using yeast-based bioassays

This study investigated the presence of a variety of pesticides (herbicides, fungicides, and insecticides) in effluent of three wastewater treatment plants as well as their endocrine activities using yeast-based in vitro assays. Although the presence of these contaminants of emerging concern is frequently reported to be present throughout the environment, their presence in wastewater treatment plants has been seldom studied. Of the 18 compounds investigated in this study, imidacloprid was the only compound not detected in all three WWTPs. Concentrations measured ranged from 3ng/L to 27μg/L for fluconazole. The yeast estrogenic and yeast androgenic screen assays were performed on target compounds in order to investigate their endocrine disruption and potential environmental risks to receiving waters. It was found that of the 14 compounds investigated 12 showed either antiestrogenic or antiandrogenic activity and seven compounds showed pleiotropic effects. In addition to confirming endocrine activities of pesticides using the yeast-based assays this study is one of the first to report activities for novel compounds including three neonicotinoids.

Hepatotoxic combination effects of three azole fungicides in a broad dose range

Single active substances of pesticides are thoroughly examined for their toxicity before approval. In this context, the liver is frequently found to be the main target organ. Since consumers are generally exposed to multiple residues of different active substances via the diet, it is important to analyse combinations of active substances for potential mixture effects. For the (tri-)azoles, a group of agricultural fungicides and antifungal drugs, combination effects on the liver are likely because of a similar mode of action. Hepatotoxic effects of mixtures of two triazoles (cyproconazole and epoxiconazole) and an imidazole (prochloraz) were investigated in a 28-day feeding study in rats at three dose levels ranging from a typical toxicological reference value to a clear effect dose. Test parameters included organ weights, clinical chemistry, histopathology and morphometry. In addition, molecular parameters were investigated by means of pathway-focused gene expression arrays, quantitative real-time PCR and enzyme activity assays. Effects were compared to those caused by the individual substances as observed at the same dose levels in a previous study. Mixture effects were substantiated by increases in relative and absolute liver weights, histopathological findings and alterations in clinical chemistry parameters at the top dose level. On the molecular level also at lower dose levels, additive effects could be observed for the induction of several cytochrome P 450 enzymes (Cyp1a1, Cyp2b1, Cyp3a2), transporters (Abcb1a, Abcc3) and of genes encoding for enzymes involved in fatty acid or phospholipid metabolism (Ppargc1a, Sc4 mol). In most cases, treatment with mixtures caused a more pronounced effect as compared to the individual substances. However, the assumption of dose additivity was in general sufficiently conservative to cover mixture effects observed under the conditions of the present study.

In vitro observations and in silico predictions of xenoestrogen mixture effects in T47D-based receptor transactivation and proliferation assays

Within endocrine disruptor research, evaluation and interpretation of mixture effects and the predictive value for downstream responses still warrant more in-depth investigations. We used an estrogen receptor (ER)-mediated reporter gene assay (ER-CALUX®) and a cell proliferation assay (WST-1 assay), both based on the T47D breast cancer cell line, to test mixtures of heterogeneous xenoestrogens. Observed concentration-response curves were compared to those predicted by the concepts of concentration addition (CA), generalized concentration addition (GCA), and a novel full logistic model (FLM). CA performed better regarding mixture potency (EC50 values), whereas GCA was superior in predicting mixture efficacy (maximal response). In comparison, FLM proved to be highly suitable for in silico mixture effect prediction, combining advantages of both CA and GCA. The inter-assay comparison revealed that ER activation is not necessarily predictive for induction of cell proliferation. The results support the use of models like CA, GCA, or FLM in mixture effect evaluation. However, we conclude that reliable estimations regarding the disruptive potential of mixtures of endocrine active substances require an integrative approach considering more than one assay/endpoint to avoid misinterpretations. The formazan-based WST-1 proliferation assay might be a possible alternative to commonly used proliferation assays in endocrine disrupter research.