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Secondary organic aerosols (SOA) formed by oxidation of typical precursors largely emitted by biomass burning, such as PAHs and furans, are still poorly characterized in terms of formation yields, physical and light absorption properties, particularly those generated at night following reaction with nitrate radicals (NO3). In the present study, we evaluated and compared the formation yields, effective density (ρeff), absorption Ångström exponent (α), and mass absorption coefficient (MAC) of laboratory-generated SOA from three furan compounds (furan, 2-methylfuran, and 2,5-dimethylfuran) and four PAHs (naphthalene, acenaphthylene, fluorene, and phenanthrene). SOA were generated in an oxidation flow reactor from the reaction between hydroxyl radicals (OH; 0.1–20 equivalent aging days) or NO3 radicals (0.05–6 equivalent aging nights of 14 h) with single furan or PAH. The ρeff, formation yields, α, and MAC of the generated SOA varied depending on the precursor and oxidant considered. The ρeff of SOA formed with OH and NO3 tended to increase with particle size before reaching a “plateau”. This was particularly evident for the nighttime chemistry experiments with NO3 radicals (1.2 to 1.6 on average for particles > 100 nm). Such results highlighted potential differences in the chemical composition of the SOA, as well as probably in their morphology, according to the particle size. Three times lower SOA formation yields were obtained with NO3 compared to OH. The yields of PAH SOA (18 to 76 %) were 5 to 6 times higher than those obtained for furans (3–12 %). While furan SOA showed low or negligible light absorption properties, PAH SOA was found to have a significant impact in the UV-Visible region, implying a significant contribution to atmospheric brown carbon (BrC). No increase in the MAC values was observed from OH to NO3 oxidation processes, probably due to a low formation of nitrogen-containing chromophores through homogeneous gas phase oxidation processes with NO3 only (without NOx). Overall, the results obtained in this work demonstrated that PAHs are significant precursors of SOA emitted by biomass burning, through both, day- and nighttime processes, and have a substantial impact on the aerosol light absorption properties and so probably on climate.

International audience; Synthetic glucocorticoids (GCs) are a group of steroids that are massively used as anti-inflammatory drugs to treat a broad spectrum of deseases such as asthma or arthritis. They may enter surface waters via urban, hospital and/or pharmaceutical industry effluents and were already detected in surface waters at concentrations ranging from < 1 to tens of ng/L. In organisms, GCs are designed to act through the glucocorticoid receptor (GR) and some studies have reported adverse effects on aquatic vertebrates, such as fish. Overall, there is still a need for knowledge on the sources and driver compounds for GR activity in different contexts. In the frame of a French national survey of EDCs in surface waters using in vitro bioassays, we previously identified a hotspot river site with high GR activity. To further identify the source(s) and the nature of this contamination, an investigative monitoring based on bioassay (MDA-Kb2) and chemical analyses was implemented in the current study. A contamination mapping was established on the basis of bioassay data, along a 40 km streatch upstream and downstream of the contaminated site allowing identification of the discharge of the contamination in the river and of its highly probable industrial origin in the sewerage network, although the contribution of waste waters from a hospital could not be excluded. By using a suspect screening approach based on HR-MS, fluticasone propionate as well as few other GCs were identified in the samples. Mass balance analysis based on quantitave chemical analysis confirmed fluticasone propionate main role in the measured GR activity. The high mobility and persistence of this contamination points out possible high environmental concern in terms of its fate and hazard for aquatic organisms.

Within the Water Framework Directive Common Implementation Strategy (WFD CIS) context, the derivation of Environmental Quality Standards (EQS) is framed by recommendations given in the European Technical Guidance Document for Deriving EQS (TGD EQS, E.C., 2018). This guidance recommends the use of data that are deemed relevant and reliable. Those are most often generated using standardised test methods, but not confined to standard studies and species. The concern raised by endocrine disruption should be tackled in diverse regulatory frameworks, among which the WFD. In this context, endocrine disruption (ED) is quoted several times as an issue in the TGD EQS but recommendations as this regards are not prescriptive. Our study attempts to assess how far can the ECHA/EFSA Guidance for the identification of endocrine disruptors (ECHA/EFSA, 2018) and its weight of evidence approach may be used within the context of the derivation of EQS for tebuconazole.The work consisted in (i) gathering ED toxicity data for aquatic wildlife and mammals not included in the initial dataset underlying the current EQS, (ii) assembling them in a database as lines of evidence of toxicity adressing endocrine activity in order to assess as rigorously as possible the ED potential of tebuconazole and finally (iii) analysing these data to evaluate how far they allowed to improve reliability of the current EQS for tebuconazole.The collection of data allowed to assemble more than 200 lines of evidence consisting in vivo mammals data (52%), in vivo wildlife data (34%) and in vitro mechanistics data (14%).The assessment did not allow to conclude on the ED potential of tebuconazole for wildlife strictly applying the guidance, whereas this ED potential was demonstrated for mammals for which at least two modes of action analysis enabled to conclude on the link between endocrine activity and adversity.Wildlife toxicity assessment would need more in-depth analysis, inter alia to collate and analyse invertebrates toxicity data in order to assess other taxa than fish and amphibians which are already well-represented in the dataset.This analysis allowed implementation of the weight of evidence approach of non-standard toxicity test within the assessment in order to strenghten relevancy and reliability of its EQS. It gives a good opportunity to evaluate how ECHA/EFSA guidance may be used in another regulatory context for which it is meant and allows highlighting the pros and cons of this exercise.

Monitoring of environmental estrogens has become a major concern to assess the quality of water bodies. In that respect, the use of in vitro reporter gene assays to monitor estrogenic activity has proven relevant as it enables an integrative and quantitative assessment of ER-active contaminants. However, in vitro cell assays may not necessarily reflect the estrogenic activity observed in vivo in fish, raising the question of the relevance of in vitro measurement of estrogenic activity to predict risk for aquatic species and ecosystems.In this context, our objective was to determine 1) whether estrogenic activity measured in vitro led to an in vivo response in a fish biological model, and 2) on the basis of such an in vitro / in vivo comparison, whether there exists an in vitro threshold value above which an in vivo effect is detected/evidenced. This study reports the use of the zebrafish-based EASZY assay to assess in vivo estrogenic activity of 33 surface (SW) and waste water (WW) samples collected across Europe and that were previously well-characterized for estrogen hormones and in vitro estrogenic activity (Könemann et al., 2018). We showed that 18 out of the 33 SW and WW samples induced estrogenic responses in transgenic zebrafish embryos leading to significant and concentration-dependant dependent up-regulation of the ER-regulated cyp19a1b gene expression in the developing brain. The in vivo 17?-estradiol-equivalents (EEQs) were highly correlated with both the chemical analytical risk quotient (RQ) based on steroidal estrogen concentrations and EEQs reported from 5 different in vitro assays. Based on in vitro vs. in vivo comparison, regression analyses allowed to determine for each in vitro assay an optimal cut-off value which was defined as an effect-based trigger values (EBTs) above which in vivo responses were observed. The definition of these in vitro assay-specific EBTs values allowed to improve the sensitivity and specificity of the individual in vitro assays for predicting a risk associated with substances acting through the same mode of action within environmental mixtures. Altogether, this study provides experimental demonstration of the toxicological relevance of in vitro-based assessment of estrogenic activity and recommends the use of such in vitro/in vivo comparative approach to refine and validate EBTs for mechanism-based bioassays.

Effect-based methods (EBM) are relevant tools to monitor chemical quality of aquatic systems as they provide integrative assessment of contamination components and inform on hazard associated with complex mixtures. In the frame of a French national program aiming at demonstrating the operational performance of passive sampling to monitor priority chemicals in surface waters, we applied a panel of in vitro bioassays to investigate 1) the occurrence of steroid- and dioxin- /PAH-like activities, 2) their distribution in the water column using grab sampling and integrative passive sampling. In addition, we looked into the relevance of in vitro estrogenicity in the water as compared to established trigger values and in vivo assessment in zebrafish. Twenty surface water sites of different anthropogenic pressures were studied. For each of them, both grab (dissolved phase and particulate matter) and integrative sampling (POCIS and Silicone Rubber membranes) were performed over a 15 days period and organic extract of each sample was analyzed with the bioassays. In vitro toxicity profiles in grab water organic extracts showed contrasted contamination patterns depending on the time of sampling (T0 and T15) and the studied sites. Estrogenic and PAH-like activities were the most occurent activities, while glucocorticoidic and anti-androgenic ones were detected at specific sites. No androgenic activity was detected. PAH-like activity was associated with both the dissolved and particulate matter phases while endocrine activities were only found in the dissolved phase. At some sites, in vitro estradiol-equivalents were found above the generic trigger value considering environmental risk (0.4 ng E2Eq/L). For 7 sites out of the 10 tested in vivo, activities were coherent with those predicted by in vitro bioassays. The present study highlights the relevance of combining a set of effect-based tools and smart sampling to monitor site-specific contamination of surface water chemical quality and the partitioning of measured activities in the water column. Our approach further includes in vivo mechanism-based assays, which enhances the toxicological relevance of the assessment. Comparison of our data with established trigger values for some activities will be discussed. Finally, ongoing chemical analyses of more than 100 priority substances, including estrogenic hormones, will allow the determination of their contribution to the biological activities detected.

Le récepteur humain Pregnane X Receptor (hPXR, NR1I2) est impliqué dans la biosynthèse, la distribution et le métabolisme de stéroïdes, d’acides biliaires et de xénobiotiques, parmi lesquels de nombreux pesticides. Quand des xénobiotiques se lient au hPXR, ce complexe forme un hétérodimère avec le récepteur X des rétinoïdes (RXR) et induit l’expression de gènes de détoxication comme les gènes codant pour les enzymes de phase I (CYP), de phase II (conjugaison) ou des protéines de transport (transporteurs de la famille ABC), résultant en une clairance des stéroïdes, des drogues et xénobiotiques par le foie et l’intestin (Timsit et al, 2007). L’activation de hPXR a été associée à des interactions médicamenteuses, la perturbation endocrinienne, la chimiorésistance, la croissance et l’agressivité de cancers du côlon et du foie (Planque et al, 2016 ; Wang et al, 2011 ; Kodama et al, 2015 ; Pondugula et al, 2016). Des études récentes ont révélé l’activité hPXR d’échantillons environnementaux de milieux aquatiques comme les effluents urbains et industriels, les eaux de surface et les sédiments de rivière (Creusot et al, 2011 ; Dagnino et al, 2012). Comparativement au PXR humain, il apparaît que le PXR de poisson zèbre (zfPXR) est activé par un plus faible nombre de pesticides (Ekins et al, 2008 ; Krasowski et al, 2011 ; Milnes et al, 2008) et que certains d’entre eux ont une meilleure affinité pour zfPXR que pour hPXR, suggérant d’importantes différences entre les deux récepteurs. De plus, les rôles du PXR dans le métabolisme du poisson ne sont pas encore pleinement élucidés. Dans ce contexte, nous avons cherché à caractériser les interactions entre les pesticides et le PXR chez l'homme et le poisson zèbre et à étudier le rôle de zfPXR dans le métabolisme du poisson. À cette fin, nous avons testé l'activité PXR d'échantillons environnementaux et de pesticides à l'aide de lignées cellulaires luminescentes exprimant soit hPXR soit zfPXR. Les pesticides les plus puissants ont ensuite été testés pour leur capacité à réguler l'expression des gènes cibles de PXR et à agir sur la prolifération cellulaire et la résistance aux médicaments dans ces cellules. Ces travaux seront combinés à des approches de modélisation (zfPXR) et de cristallographie (hPXR) pour étudier les interactions structurelles des pesticides avec hPXR et zfPXR, et à une approche in vivo utilisant le poisson zèbre pour étudier les effets des pesticides sur les gènes régulés par PXR. Dans l'ensemble, nos données permettent de mieux comprendre le rôle et les mécanismes d'action du PXR chez l'homme et le poisson zèbre et mettent en évidence des différences inter-espèces pour une meilleure évaluation des risques d'exposition aux pesticides pour la santé humaine et l'environnement.