Progress, applications, and challenges in high-throughput effect-directed analysis for toxicity driver identification - is it time for HT-EDA?

The rapid increase in the production and global use of chemicals and their mixtures has raised concerns about their potential impact on human and environmental health. With advances in analytical techniques, in particular, high-resolution mass spectrometry (HRMS), thousands of compounds and transformation products with potential adverse effects can now be detected in environmental samples. However, identifying and prioritizing the toxicity drivers among these compounds remain a significant challenge. Effect-directed analysis (EDA) emerged as an important tool to address this challenge, combining biotesting, sample fractionation, and chemical analysis to unravel toxicity drivers in complex mixtures. Traditional EDA workflows are labor-intensive and time-consuming, hindering large-scale applications. The concept of high-throughput (HT) EDA has recently gained traction as a means of accelerating these workflows. Key features of HT-EDA include the combination of microfractionation and downscaled bioassays, automation of sample preparation and biotesting, and efficient data processing workflows supported by novel computational tools. In addition to microplate-based fractionation, high-performance thin-layer chromatography (HPTLC) offers an interesting alternative to HPLC in HT-EDA. This review provides an updated perspective on the state-of-the-art in HT-EDA, and novel methods/tools that can be incorporated into HT-EDA workflows. It also discusses recent studies on HT-EDA, HT bioassays, and computational prioritization tools, along with considerations regarding HPTLC. By identifying current gaps in HT-EDA and proposing new approaches to overcome them, this review aims to bring HT-EDA a step closer to monitoring applications.

Silicone wristband as a sampling tool for insecticide exposure assessment of vegetable farmers.

The use of passive sampling devices (PSDs) as an appropriate alternative to conventional methods of assessing human exposure to environmental toxicants was studied. One-time purposive sampling by a silicone wristband was used to measure insecticide residues in 35 volunteer pepper farmers in the Vea irrigation scheme in the Guinea savannah and the Weija irrigation scheme in the coastal savannah ecological zones of Ghana. A GC-MS/MS method was developed and validated for quantifying 18 insecticides used by farmers in Ghana. Limits of detection (LODs) and quantitation (LOQs) ranged from 0.64 to 67 and 2.2-222 ng per wristband, respectively. The selected insecticides showed a range of concentrations in the various silicone wristbands from not detected to 27 µg/wristband. The concentrations of 13 insecticides were above their LOQs. Chlorpyrifos had the highest detection frequencies and concentrations, followed by cyhalothrin and then allethrin. This study shows that silicone wristbands can be used to detect individual insecticide exposures, providing a valuable tool for future exposure studies. Ghanaian vegetable farmers are substantially exposed to insecticides. Hence, the use of appropriate personal protective equipment is recommended.

Do cats mirror their owner? Paired exposure assessment using silicone bands to measure residential PAH exposure.

It has been suggested that domestic animals can serve as sentinels for human exposures. In this study our objectives were to demonstrate that i) silicone collars can be used to measure environmental exposures of (domestic) animals, and that ii) domestic animals can be used as sentinels for human residential exposure. For this, we simultaneously measured polycyclic aromatic hydrocarbons (PAHs) using silicone bands worn by 30 pet cats (collar) and their owner (wristband). Collars and wristbands were worn for 7 days and analyzed via targeted Gas Chromatography-Mass Spectrometry (GC-MS). Demographics and daily routines were collected for humans and cats. Out of 16 PAHs, 9 were frequently detected (>50% of samples) in both wristbands and collars, of which Phenanthrene and Fluorene were detected in all samples. Concentrations of wristbands and collars were moderately correlated for these 9 PAHs (Median Spearman's r = 0.51 (range 0.16-0.68)). Determinants of PAH concentrations of cats and humans showed considerable overlap, with vacuum cleaning resulting in higher exposures and frequent changing of bed sheets in lower exposures. This study adds proof-of-principle data for the use of silicone collars to measure (domestic) animal exposure and shows that cats can be used as sentinels for human residential exposure.

Identification of antimicrobial and glucocorticoid compounds in wastewater effluents with effect-directed analysis.

Pharmaceuticals, such as glucocorticoids and antibiotics, are inadequately removed from wastewater and may cause unwanted toxic effects in the receiving environment. This study aimed to identify contaminants of emerging concern in wastewater effluent with antimicrobial or glucocorticoid activity by applying effect-directed analysis (EDA). Effluent samples from six wastewater treatment plants (WWTPs) in the Netherlands were collected and analyzed with unfractionated and fractionated bioassay testing. Per sample, 80 fractions were collected and in parallel high-resolution mass spectrometry (HRMS) data were recorded for suspect and nontarget screening. The antimicrobial activity of the effluents was determined with an antibiotics assay and ranged from 298 to 711 ng azithromycin equivalents·L-1. Macrolide antibiotics were identified in each effluent and found to significantly contribute to the antimicrobial activity of each sample. Agonistic glucocorticoid activity determined with the GR-CALUX assay ranged from 98.1 to 286 ng dexamethasone equivalents·L-1. Bioassay testing of several tentatively identified compounds to confirm their activity revealed inactivity in the assay or the incorrect identification of a feature. Effluent concentrations of glucocorticoid active compounds were estimated from the fractionated GR-CALUX bioassay response. Subsequently, the biological and chemical detection limits were compared and a sensitivity gap between the two monitoring approaches was identified. Overall, these results emphasize that combining sensitive effect-based testing with chemical analysis can more accurately reflect environmental exposure and risk than chemical analysis alone.

Association between chemical mixtures and female fertility in women undergoing assisted reproduction in Sweden and Estonia.

OBJECTIVE: Women of reproductive age are exposed to ubiquitous chemicals such as phthalates, parabens, and per- and polyfluoroalkyl substances (PFAS), which have potential endocrine disrupting properties and might affect fertility. Our objective was to investigate associations between potential endocrine-disrupting chemicals (EDCs) and female fertility in two cohorts of women attending fertility clinics. METHODS: In a total population of 333 women in Sweden and Estonia, we studied the associations between chemicals and female fertility, evaluating ovarian sensitivity index (OSI) as an indicator of ovarian response, as well as clinical pregnancy and live birth from fresh and frozen embryo transfers. We measured 59 chemicals in follicular fluid samples and detected 3 phthalate metabolites, di-2-ethylhexyl phthalate (DEHP) metabolites, 1 paraben, and 6 PFAS in >90% of the women. Associations were evaluated using multivariable-adjusted linear or logistic regression, categorizing EDCs into quartiles of their distributions, as well as with Bayesian Kernel Machine Regression. RESULTS: We observed statistically significant lower OSI at higher concentrations of the sum of DEHP metabolites in the Swedish cohort (Q4 vs Q1, ß = -0.21, 95% CI: -0.38, -0.05) and methylparaben in the Estonian cohort (Q3 vs Q1, ß = -0.22, 95% CI: -0.44, -0.01). Signals of potential associations were also observed at higher concentrations of PFUnDA in both the combined population (Q2 vs. Q1, ß = -0.16, 95% CI -0.31, -0.02) and the Estonian population (Q2 vs. Q1, ß = -0.27, 95% CI -0.45, -0.08), and for PFOA in the Estonian population (Q4 vs. Q1, ß = -0.31, 95% CI -0.61, -0.01). Associations of chemicals with clinical pregnancy and live birth presented wide confidence intervals. CONCLUSIONS: Within a large chemical mixture, we observed significant inverse associations levels of DEHP metabolites and methylparaben, and possibly PFUnDA and PFOA, with OSI, suggesting that these chemicals may contribute to altered ovarian function and infertility in women.

High-Performance Data Processing Workflow Incorporating Effect-Directed Analysis for Feature Prioritization in Suspect and Nontarget Screening.

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.

Pesticide residue levels in vegetables and surface waters at the Central Rift Valley (CRV) of Ethiopia.

Seven pesticides, profenofos, metalaxyl, λ-cyhalothrin, 4,4'-DDT, 4,4'-DDE, and α- and ß-endosulfan, were determined in vegetables (tomato, onion) from 20 locations and surface waters from 12 locations in the Central Rift Valley (CRV) of Ethiopia. Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) and solid phase extraction (SPE) methods were used for the vegetables and water, respectively. In 2.5% of the tomato samples, profenofos was detected above European maximum residue limits (MRLs), in 12.5% of the samples metalaxyl, and in 2.5% α- and ß-endosulfan. In 5% of the onion samples, profenofos was detected above European MRLs, in 7.5% of the onion samples metalaxyl, and in 5% λ-cyhalothrin. In surface water, profenofos was detected at the highest concentration of 2300 µg/L in the Bulbula River, 890 µg/L near the agricultural land north of Lake Ziway (ANLZ-1), 1700 µg/L in the floriculture effluent (FE-1), and 900 µg/L in tap water at the Batu Drinking Water (BDW) supply. These results show that the levels of pesticides are in several cases substantially elevated, and emphasize the need of regular pesticide monitoring programs for surface waters and vegetables in the Ethiopian CRV.

Occurrence of legacy and alternative plasticizers in indoor dust from various EU countries and implications for human exposure via dust ingestion and dermal absorption.

Plasticizers are a category of chemicals extensively used in consumer products and, consequently, their presence is ubiquitous in the indoor environment. In the present study, an analytical method has been developed for the quantification of plasticizers (7 legacy phthalate esters (LPEs) and 14 alternative plasticizers (APs)) in indoor floor dust based on ultrasonic and vortex extraction, Florisil fractionation and GC-(EI)-MS analysis. Dust samples (n = 54) were collected from homes, offices, and daycare centers from different EU countries (Belgium, the Netherlands, Ireland and Sweden). Method LOQs ranged from 0.2 to 5 µg/g. Tri-n-hexyl trimellitate (THTM) was not detected in any sample, whereas dimethyl phthalate (DMP), diphenyl phthalate and acetyl triethyl citrate (ATEC) were detected only in 6, 2 and 1 out of 54 samples, respectively. The highest concentrations of plasticizers were measured in Swedish offices, at a mean concentration of total plasticizers of 1800 µg/g, followed by Swedish daycare centers at 1200 and 670 µg/g for winter and spring sampling, respectively. Generally, the contribution of APs was slightly higher than for LPEs for all indoor environments (mean contribution 60% and 40%, respectively based on contributions per indoor environment). For the APs, main contributors were DINP in Belgian homes (28%), Swedish offices (60%), Swedish daycare centers (48%), and Dutch offices (31%) and DEHT in Belgian (28%), Irish (40%) and Dutch homes (37%) of total APs. The predominant LPE was bis-2-ethylhexyl-phthalate (DEHP) with a mean contribution varying from 60% to 85% of total LPEs. Human exposure was evaluated for dust ingestion and dermal absorption using hazard quotients (HQs) of plasticizers (ratio between average daily doses and the reference dose). None of the HQs of plasticizers exceeded 1, meaning that the risk for adverse human health effects from these plasticizers via dust ingestion and dermal absorption is unlikely.

Review of the analysis of insecticide residues and their levels in different matrices in Ghana.

This review reports on how Ghanaian scientists analyse insecticide residues in various matrices in their laboratories as well as the levels of insecticides found in Ghana. It covers different sample preparation methods such as solid-liquid and liquid-liquid extraction. The main technique used for this analysis was gas chromatography (GC) with various detectors such as electron capture, flame photometric, nitrogen phosphorus, and mass spectrometric detection. Liquid chromatography (LC) with mass spectrometric detection was sometimes used to determine the levels of very polar insecticide residues. From the articles reviewed 74% of the insecticides detected were organochlorines with DDTs, lindanes, and endosulfans as most abundant ones. Levels of the insecticides of interest analysed, varied from below the detection limits to clearly above the safety limits. The lowest detected concentration of insecticide residues reported in fruits and vegetables was δ-lindane in pawpaw (0.06 mg/kg) while the highest was fenvalerate (25.6 mg/kg). Insecticide residues reported in sediment were predominantly organochlorines with concentrations ranging from 9.68 ng/kg to 10.98 µg/kg. Endosulfan and its metabolites were the main insecticides found in water bodies with concentrations ranging from 0.036 µg/L to 62.3 µg/L. DDT and its metabolites were the dominant insecticides found in human fluids.

High-Throughput Effect-Directed Analysis Using Downscaled in Vitro Reporter Gene Assays To Identify Endocrine Disruptors in Surface Water.

Effect-directed analysis (EDA) is a commonly used approach for effect-based identification of endocrine disruptive chemicals in complex (environmental) mixtures. However, for routine toxicity assessment of, for example, water samples, current EDA approaches are considered time-consuming and laborious. We achieved faster EDA and identification by downscaling of sensitive cell-based hormone reporter gene assays and increasing fractionation resolution to allow testing of smaller fractions with reduced complexity. The high-resolution EDA approach is demonstrated by analysis of four environmental passive sampler extracts. Downscaling of the assays to a 384-well format allowed analysis of 64 fractions in triplicate (or 192 fractions without technical replicates) without affecting sensitivity compared to the standard 96-well format. Through a parallel exposure method, agonistic and antagonistic androgen and estrogen receptor activity could be measured in a single experiment following a single fractionation. From 16 selected candidate compounds, identified through nontargeted analysis, 13 could be confirmed chemically and 10 were found to be biologically active, of which the most potent nonsteroidal estrogens were identified as oxybenzone and piperine. The increased fractionation resolution and the higher throughput that downscaling provides allow for future application in routine high-resolution screening of large numbers of samples in order to accelerate identification of (emerging) endocrine disruptors.

Thyroid-stimulating hormone levels in newborns and early life exposure to endocrine-disrupting chemicals: analysis of three European mother-child cohorts.

BackgroundVarious studies have reported interactions between thyroid hormones and early life chemical exposure. Our objective was to analyze the associations between markers of endocrine-disrupting chemical exposure and thyroid function in newborns, determined through heel prick blood spots.MethodsThree European mother-child cohorts (FLEHSI-Belgium, HUMIS-Norway, and the PCB cohort-Slovakia. Total n=1,784) were pooled for the purpose of this study. Data on thyroid-stimulating hormone (TSH) were obtained from national neonatal screening registries, and samples of cord plasma and/or breast milk were collected to determine exposure to various chemicals. Multiple regression models were composed with exposure and cohort as fixed factors, and adjustments were made for a priori defined covariates.ResultsMedian TSH concentrations were 1, 1.10, and 2.76 mU/l for the Belgian, Norwegian, and Slovak cohorts, respectively. For polychlorinated biphenyl (PCB)-153 and dichlorodiphenyldichloroethylene (p,p'-DDE), children in the third exposure quartile had a 12-15% lower TSH at birth. Results remained unchanged after additional adjustment for birth weight and gestational weight gain. No effect on TSH was observed for the other compounds.ConclusionEarly life exposure to PCB-153 and p,p'-DDE impacts newborn TSH levels. Higher exposure levels were associated with 12-15% lower TSH levels.

Multigeneration toxicity of imidacloprid and thiacloprid to Folsomia candida.

In a recent study, we showed that the springtail Folsomia candida was quite sensitive the neonicotinoid insecticides imidacloprid and thiacloprid. This study aimed at determining the toxicity of both compounds to F. candida following exposure over three generations, in natural LUFA 2.2 standard soil. In the first generation, imidacloprid was more toxic than thiacloprid, with LC50s of 0.44 and 9.0 mg/kg dry soil, respectively and EC50s of 0.29 and 1.5 mg/kg dry soil, respectively. The higher LC50/EC50 ratio suggests that thiacloprid has more effects on reproduction, while imidacloprid shows lethal toxicity to the springtails. In the multigeneration tests, using soil spiked at the start of the first generation exposures, imidacloprid had a consistent effect on survival and reproduction in all three generations, with LC50s and EC50s of 0.21-0.44 and 0.12-0.29 mg/kg dry soil, respectively, while thiacloprid-exposed animals showed clear recovery in the second and third generations (LC50 and EC50 > 3.33 mg/kg dry soil). The latter finding is in agreement with the persistence of imidacloprid and the fast degradation of thiacloprid in the test soil.

Rapid Screening of Acetylcholinesterase Inhibitors by Effect-Directed Analysis Using LC × LC Fractionation, a High Throughput in Vitro Assay, and Parallel Identification by Time of Flight Mass Spectrometry.

Effect-directed analysis (EDA) is a useful tool to identify bioactive compounds in complex samples. However, identification in EDA is usually challenging, mainly due to limited separation power of the liquid chromatography based fractionation. In this study, comprehensive two-dimensional liquid chromatography (LC × LC) based microfractionation combined with parallel high resolution time of flight (HR-ToF) mass spectrometric detection and a high throughput acetylcholinesterase (AChE) assay was developed. The LC × LC fractionation method was validated using analytical standards and a C18 and pentafluorophenyl (PFP) stationary phase combination was selected for the two-dimensional separation and fractionation in four 96-well plates. The method was successfully applied to identify AChE inhibitors in a wastewater treatment plant (WWTP) effluent. Good orthogonality (>0.9) separation was achieved and three AChE inhibitors (tiapride, amisulpride, and lamotrigine), used as antipsychotic medicines, were identified and confirmed by two-dimensional retention alignment as well as their AChE inhibition activity.

Changes in Neurotransmitter Profiles during Early Zebrafish (Danio rerio) Development and after Pesticide Exposure.

During early development, neurotransmitters are important stimulants for the development of the central nervous system. Although the development of different neuronal cell types during early zebrafish (Danio rerio) development is well-studied, little is known of the levels of neurotransmitters, their precursors and metabolites during development, and how these levels are affected by exposure to environmental contaminants. A method based on hydrophilic interaction liquid chromatography coupled to tandem mass spectrometry has been applied for the first time to zebrafish embryos and larvae to study five neurotransmitter systems in parallel, including the dopaminergic-andrenergic, glutaminergic-GABAnergic, serotoninergic, histaminergic, and cholinergic systems. Our method enables the quantification of neurotransmitters and their precursors and metabolites in whole zebrafish from the period of zygote to free-swimming larvae 6 days postfertilization (dpf). We observed a developmental stage-dependent pattern with clear differences between the first 2 days of development and the following days. Whereas the neurotransmitter levels steadily increased, the precursors showed a peak at 3 dpf. After exposure to several pesticides, significant differences in concentrations of neurotransmitters and precursors were observed. Our study revealed new insights about neurotransmitter systems during early zebrafish development and showed the usefulness of our approach for environmental neurotoxicity studies.

Highly Selective Screening of Estrogenic Compounds in Consumer-Electronics Plastics by Liquid Chromatography in Parallel Combined with Nanofractionation-Bioactivity Detection and Mass Spectrometry.

The chemical safety of consumer products is an issue of emerging concern. Plastics are widely used, e.g. as casings of consumer electronics (TVs, computers, routers, etc.), which are present in houses and offices in continuously increasing numbers. In this study, we investigate the estrogenic activity of components of plastics coming from electronics' casings. A recently developed fractionation platform for effect-directed analysis (EDA) was used. This platform combines reversed-phase liquid chromatography in parallel with bioassay detection via nanofractionation and with online high-resolution time-of-flight mass spectrometry (TOFMS) for the identification of bioactives. Four out of eight of the analyzed plastics samples showed the presence of estrogenic compounds. Based on the MS results these were assigned to bisphenol A (BPA), 2,4-di-tert-butylphenol, and a possible bisphenol A analog. All samples contained flame retardants, but these did not show any estrogenicity. The observed BPA, however, could be an impurity of tetrabromo-BPA (TBBPA) or TBBPA-based flame retardants. Due to the plausible migration of additives from plastics into the environment, plastics from consumer electronics likely constitute a source of estrogenic compound contamination in the indoor environment.

Pesticide Mixture Toxicity in Surface Water Extracts in Snails (Lymnaea stagnalis) by an in Vitro Acetylcholinesterase Inhibition Assay and Metabolomics.

Many chemicals in use end up in the aquatic environment. The toxicity of water samples can be tested with bioassays, but a metabolomic approach has the advantage that multiple end points can be measured simultaneously and the affected metabolic pathways can be revealed. A current challenge in metabolomics is the study of mixture effects. This study aims at investigating the toxicity of an environmental extract and its most abundant chemicals identified by target chemical analysis of >100 organic micropollutants and effect-directed analysis (EDA) using the acetylcholinesterase (AChE) bioassay and metabolomics. Surface water from an agricultural area was sampled with a large volume solid phase extraction (LVSPE) device using three cartridges containing neutral, anionic, and cationic sorbents able to trap several pollutants classes like pharmaceuticals, pesticides, PAHs, PCBs, and perfluorinated surfactants. Targeted chemical analysis and AChE bioassay were performed on the cartridge extracts. The extract of the neutral sorbent cartridge contained most of the targeted chemicals, mainly imidacloprid, thiacloprid, and pirimicarb, and was the most potent AChE inhibitor. Using an EDA approach, other AChE inhibiting candidates were identified in the neutral extract, such as carbendazim and esprocarb. Additionally, a metabolomics experiment on the central nervous system (CNS) of the freshwater snail Lymnaea stagnalis was conducted. The snails were exposed to the extract, the three most abundant chemicals individually, and a mixture of these. The extract disturbed more metabolic pathways than the three most abundant chemicals individually, indicating the contribution of other chemicals. Most pathways perturbed by the extract exposure overlapped with those related to exposure to neonicotinoids, like the polyamine metabolism involved in CNS injuries. Metabolomics for the straightforward comparison between a complex mixture and single compound toxicity is still challenging but, compared to traditional biotesting, is a promising tool due to its increased sensitivity.

Demographic, Reproductive, and Dietary Determinants of Perfluorooctane Sulfonic (PFOS) and Perfluorooctanoic Acid (PFOA) Concentrations in Human Colostrum.

To determine demographic, reproductive, and maternal dietary factors that predict perfluoroalkyl substance (PFAS) concentrations in breast milk, we measured perfluorooctane sulfonic (PFOS) and perfluorooctanoic acid (PFOA) concentrations, using liquid chromatography-mass spectrometry, in 184 colostrum samples collected from women participating in a cohort study in Eastern Slovakia between 2002 and 2004. During their hospital delivery stay, mothers completed a food frequency questionnaire, and demographic and reproductive data were also collected. PFOS and PFOA predictors were identified by optimizing multiple linear regression models using Akaike's information criterion (AIC). The geometric mean concentration in colostrum was 35.3 pg/mL for PFOS and 32.8 pg/mL for PFOA. In multivariable models, parous women had 40% lower PFOS (95% CI: -56 to -17%) and 40% lower PFOA (95% CI: -54 to -23%) concentrations compared with nulliparous women. Moreover, fresh/frozen fish consumption, longer birth intervals, and Slovak ethnicity were associated with higher PFOS and PFOA concentrations in colostrum. These results will help guide the design of future epidemiologic studies examining milk PFAS concentrations in relation to health end points in children.

Prenatal exposure to endocrine disrupting chemicals and birth weight-A prospective cohort study.

Prenatal exposure to endocrine disrupting chemicals may affect fetal development through disruption of hormonal actions and epigenetic modifications, potentially predisposing individuals to later on-set health risks, such as obesity. The objective of this study was to determine associations between biological exposure markers of various endocrine disrupting chemicals and birth weight in a newly established, prospective mother-child cohort in the Netherlands. Birth weight (n = 91) was obtained from birth records, and exposure to dichlorodiphenyldichloroethylene (DDE), three di-2-ethylhexyl phthalate (DEHP) metabolites, polychlorinated biphenyl-153, perfluorooctanesulfonic acid (PFOS), and perfluorooctanoic acid (PFOA) was determined in cord plasma. For DDE, exposure was also measured in breast milk. Linear regression analysis was used to determine associations between compounds and birth weight, which were stratified for gender and adjusted for a priori defined covariates. Increased exposure to DDE was associated with lower birth weight in boys (>95.89 ng L-1, -325.9 g, 95% CI -634.26 to -17.56), whereas in girls a tendency towards a higher birth weight was observed. Lower birth weights for boys were also observed for high exposure to MECPP, and to a certain extent also for PFOA. MEHHP and PFOS exposure on the other hand were associated with higher birth weights in boys. In girls no effects were observed for these compounds. It can be concluded that prenatal exposure to DDE, perfluorinated alkyl acids, and phthalates was associated with changes in birth weight in this population. Associations were gender specific, and appeared to be non-linear. Since the population was relatively small, results should be interpreted with caution.

Metabolomics to Explore Imidacloprid-Induced Toxicity in the Central Nervous System of the Freshwater Snail Lymnaea stagnalis.

Modern toxicology is seeking new testing methods to better understand toxicological effects. One of the most concerning chemicals is the neonicotinoid pesticide imidacloprid. Although imidacloprid is designed to target insects, recent studies have shown adverse effects on nontarget species. Metabolomics was applied to investigate imidacloprid-induced sublethal toxicity in the central nervous system of the freshwater snail Lymnaea stagnalis. The snails (n = 10 snails) were exposed for 10 days to increasing imidacloprid concentrations (0.1, 1, 10, and 100 µg/L). The comparison between control and exposure groups highlighted the involvement and perturbation of many biological pathways. The levels of several metabolites belonging to different metabolite classes were significantly changed by imidacloprid exposure. A change in the amino acids and nucleotide metabolites like tryptophan, proline, phenylalanine, uridine, and guanosine was found. Many fatty acids were down-regulated, and the levels of the polyamines, spermidine and putrescine, were found to be increased which is an indication of neuron cell injury. A turnover increase between choline and acetylcholine led us to hypothesize an increase in cholinergic gene expression to overcome imidacloprid binding to the nicotinic acetylcholine receptors. Metabolomics revealed imidacloprid induced metabolic changes at low and environmentally relevant concentration in a nontarget species and generated a novel mechanistic hypothesis.