Perspectives for integrating human and environmental exposure assessments

Integrated Risk Assessment (IRA) has been defined by the EU FP7 HEROIC Coordination action as “the mutual exploitation of Environmental Risk Assessment for Human Health Risk Assessment and vice versa in order to coherently and more efficiently characterize an overall risk to humans and the environment for better informing the risk analysis process” (Wilks et al., 2015). Since exposure assessment and hazard characterization are the pillars of risk assessment, integrating Environmental Exposure assessment (EEA) and Human Exposure assessment (HEA) is a major component of an IRA framework. EEA and HEA typically pursue different targets, protection goals and timeframe. However, human and wildlife species also share the same environment and they similarly inhale air and ingest water and food through often similar overlapping pathways of exposure. Fate models used in EEA and HEA to predict the chemicals distribution among physical and biological media are essentially based on common properties of chemicals, and internal concentration estimations are largely based on inter-species (i.e. biota-to-human) extrapolations. Also, both EEA and HEA are challenged by increasing scientific complexity and resources constraints. Altogether, these points create the need for a better exploitation of all currently existing data, experimental approaches and modeling tools and it is assumed that a more integrated approach of both EEA and HEA may be part of the solution. Based on the outcome of an Expert Workshop on Extrapolations in Integrated Exposure Assessment organized by the HEROIC project in January 2014, this paper identifies perspectives and recommendations to better harmonize and extrapolate exposure assessment data, models and methods between Human Health and Environmental Risk Assessments to support the further development and promotion of the concept of IRA. Ultimately, these recommendations may feed into guidance showing when and how to apply IRA in the regulatory decision-making process for chemicals

Acute-to-chronic species sensitivity distribution extrapolation

International audienceSeeking to make greater use of available data for risk assessment of substances, we constructed, for the situation in which chronic data are limited or even nonexistent but acute data are relatively large, an acute to chronic transformation (ACT) methodology based on the concept of species sensitivity distributions (SSDs). This ACT methodology uses a comparison of acute and chronic SSDs, separately for vertebrate data (with 22 substances) and for invertebrate data (with 15 substances). Rather than comparing an acute toxicity value with a chronic value, as when calculating an acute to chronic ratio (ACR), samples of acute and chronic data corresponding to the same category of species were compared. Starting from a sample of acute data, the ACT methodology showed relationships that enable the creation of a sample of predicted chronic values. This sample can then be used to calculate a predicted chronic hazardous concentration potentially affecting 5% of species (HC5%), just as with a sample of real chronic toxicity values. This ACT approach was tested on I I substances. For each substance, the real chronic HC5% and the predicted chronic HC5% were calculated and compared. The ratio between chronic HC5% and ACT HC5% was, on average, 1.6 and did not exceed 4.4 for the I I substances studied

Utilisation d'un échantillonneur passif (DGT) pour l'évaluation de la remobilisation des métaux dans les sédiments (expérimentation et modélisation)

Les enjeux écologiques, réglementaires et économiques imposent que des méthodologies robustes d évaluation des risques environnementaux des sédiments contaminés soient proposées aux gestionnaires et autres parties prenantes. Dans ce travail, nous avons développé une nouvelle démarche permettant d évaluer le transport et la mobilité des métaux dans les sédiments.La DGT (Diffusion Gradient in Thin films) est un échantillonneur passif capable de prélever le métal labile en solution et le métal remobilisable par la phase particulaire. Dans cette étude, un modèle original permettant l interprétation des cinétiques expérimentales de la DGT dans les sédiments appelé PRObabilistic multi-compartmental model for Finting DGT kinetics in Sediments (DGT-PROF) a été développé. Il considère la présence de deux pools de métal labile correspondants aux métaux labiles fortement et faiblement adsorbés sur la phase solide. La pertinence de l approche DGT-PROFS a été évaluée sur un panel de 34 sédiments artificiels constitués en laboratoire qui diffèrent par : la présence ou pas d hydroxydes de fer (goethite ou ferrihydrite), la présence ou pas d acides humiques, le type de contaminant (Cd ou Cu) et l âge de la contamination (8, 65 et 190 jours). Cette démarche permet aussi d évaluer l effet de ces paramètres sur la remobilisation des métaux dans les sédiments.Les résultats montrent que la capacité du sédiment à relarguer le métal dépend inversement du pH et de l âge de la contamination. La présence des hydroxydes de fer augmente significativement la capacité de la phase solide du sédiment à fixer le métal. Cependant, la présence des AH augmente la labilité des métaux vis-vis la DGT via la formation de complexes humiques mobiles.La complémentarité des ces deux outils (DGT et DGT-PROFS) a ensuite été confrontée à des mesures DGT effectuées sur des sédiments naturels provenant de différentes régions de France, et possédant des seuils de contamination en Cd, Ni, Pb et Mn très contrastés.Evaluation of the mobility and bioavailability of metals associated to sediments have an important economic issue for the management of contaminated sites. Therefore, environmental, economic and regulation issues require to have access to a robust methodologies for environmental risk assessment of contaminated sediments. In this work, we developed a new approach for assessing the transport and mobility of metals in sediments. Diffusive gradients in thin-films (DGT) is a dynamic in-situ measuring technique that assesses the kinetics of metal resupply from the solid phase to the pore water. In this study, an original model for the interpretation of DGT experimental kinetics in sediments called DGT-PROFS model was developed. It allow to quantify metal partitioning between two particulate pools, describing weak and strong interactions with metals. The relevance of the DGT / DGT-PROFS approach was evaluated in a variety of formulated sediments that differed in the presence or not of humic acids (HA) and/or iron hydroxides (i.e., goethite and ferrihydrite). The impact of the time after contamination of the solid phase (aging effect) was also evaluated. Also, this approach allows to evaluate the effect of these parameters on the remobilization of metals in sediments. The results showed that sediments capacity to release metals depends strongly on the pH, HA and the age of the contamination. Results interpretation by DGT-PROFS model show that in the presence of HA and absence of iron hydroxides, Cd is mainly associated with weak sites, while Cu is bound to strong sites. Similarly, in the presence of both iron hydroxides and HA, Cu appeared to be more heavily associated with the strong sites than did Cd. When the incubation time increased from 8 to 190 days, a proportion of Cd initially adsorbed onto weak sites transferred to the strong sites, suggesting that the adsorption of Cd on sediments is partially controlled by slow kinetic processes. The complementarity of these tools (DGT device and DGT-PROFS model) was then evaluated on natural sediments from different regions of France, and having contamination levels of Cd, Ni, Pb and Mn very contrasting.AIX-MARSEILLE3-Bib. élec. (130559903) / SudocSudocFranceF

Determination of the residence time of suspended particles in the turbidity maximum of the Loire estuary by 7Be analysis

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Linking fate model in freshwater and PBPK model to assess human internal dosimetry of B(a)P associated with drinking water

International audienceIn the present study, we demonstrate an integrated modeling approach for predicting internal tissue concentrations of chemicals by coupling a multimedia environmental model and a generic physiologically based pharmacokinetic (PBPK) model. A case study was designed for a region situated on the Seine river watershed, downstream of the Paris megacity, and for benzo(a)pyrene emitted from industrial zones in the region. In this case study, these two models are linked only by water intake from riverine system for the multimedia model into human body for the PBPK model. The limited monitoring data sets of B(a)P concentrations in bottom sediment and in raw river water, obtained at the downstream of Paris, were used to re-construct long-term daily concentrations of B(a)P in river water. The re-construction of long-term series of B(a)P level played a key role for the intermediate model calibration (conducted in multimedia model) and thus for improving model input to PBPK model. In order to take into account the parametric uncertainty in the model inputs, some input parameters relevant for the multimedia model were given by probability density functions (PDFs); some generic PDFs were updated with site-specific measurements by a Bayesian approach. The results of this study showed that the multimedia model fits well with actual annual measurements in sediments over one decade. No accumulation of B(a)P in the organs was observed. In conclusion, this case study demonstrated the feasibility of a full-chain assessment combining multimedia environmental predictions and PBPK modeling, including uncertainty and sensitivity analyses

Linking multimedia environmental and PBPK models to assess health risks of lead associated to drinking water - A case study

Human exposure to chemicals through multiple pathways is classically estimated by the so-called 'multimedia models', calculating the distribution of contaminants among products of interest for humans (like drinking water, inhaled air, vegetables, meat, milk, etc). Combined to data describing human behavior (diet composition, time spent outside, etc), such multimedia models provide an estimation of the daily quantity inhaled or ingested by the population of interest. Once the exposure scenario is identified, the dose-response assessment is typically achieved by comparing exposure outputs (e.g, the daily intake) to reference doses, estimated from toxicological data. Coupling multi-media models for different exposure pathways with a generic physiologically based pharmacokinetic (PBPK) model for the human population enables to assess directly the impact of the exposure scenarios on the chemical's concentration in the target tissues.One aim of the European 2-FUN project (Full-chain and UNcertainty Approaches for Assessing Health Risks in FUture ENvironmental Scenarios) was to develop an integrated 'multimedia-PBPK' toolbox that also incorporates uncertainty and inter-individual variability analyses by Monte Carlo simulations, and different kinds of sensitivity analysis. In the present study, an integrated modeling approach was demonstrated for predicting internal tissue concentrations of chemicals by coupling a multimedia environmental model and a PBPK model. A case study was designed for a region situated on the Seine river watershed, downstream of the Paris megacity and for lead emitted from industrial zones in the region. The limited monitoring datasets of lead concentrations in bottom sediment and in raw river water, obtained at the downstream of Paris, were used to re-construct long-term daily concentrations of lead in river water. The re-construction of longterm series of lead level played a key role for the intermediate model calibration (conducted in multimedia model), and thus for improving model input to PBPK model. In order to take into account the parametric uncertainty in the model inputs, some input parameters relevant for the multimedia model were given by probability density functions (PDFs); some generic PDFs were updated with site-specific measurements by a Bayesian approach.This case study demonstrated the feasibility of a full-chain assessment combining multimedia environmental predictions and PBPK modeling, including uncertainty analysis

Identification of sensitive parameters in the modeling of SVOC reemission processes from soil to atmosphere

International audienceSemi-volatile organic compounds (SVOCs) are subject to Long-Range Atmospheric Transport because of transport–deposition–reemission successive processes. Several experimental data available in the literature suggest that soil is a non-negligible contributor of SVOCs to atmosphere. Then coupling soil and atmosphere in integrated coupled models and simulating reemission processes can be essential for estimating atmospheric concentration of several pollutants. However, the sources of uncertainty and variability are multiple (soil properties, meteorological conditions, chemical-specific parameters) and can significantly influence the determination of reemissions. In order to identify the key parameters in reemission modeling and their effect on global modeling uncertainty, we conducted a sensitivity analysis targeted on the ‘reemission’ output variable. Different parameters were tested, including soil properties, partition coefficients and meteorological conditions. We performed EFAST sensitivity analysis for four chemicals (benzo-a-pyrene, hexachlorobenzene, PCB-28 and lindane) and different spatial scenari (regional and continental scales). Partition coefficients between air, solid and water phases are influent, depending on the precision of data and global behavior of the chemical. Reemissions showed a lower variability to soil parameters (soil organic matter and water contents at field capacity and wilting point). A mapping of these parameters at a regional scale is sufficient to correctly estimate reemissions when compared to other sources of uncertainty

Short-term accumulation and elimination of carbon-14 in the common carp Cyprinus carpio under laboratory conditions

International audienceThis study examined the short term transfer of carbon-14 (14C) in the common carp Cyprinus carpio under laboratory conditions. Various experiments were achieved in order to investigate direct or trophic transfer for 4 days, using waterborne 14C-labelled arginine or 14C-labelled food pellets respectively. Radiolabelled food was prepared with 14C-labelled arginine or glucose in order to test how transfer kinetics might vary with the biochemical form of 14C. Elimination experiments were achieved using fish fed for 5 days on radiolabelled food and then placed under starvation for 4 days. In all experiments, water, food and fish activities were monitored every day. Different fish fractions (whole body, muscle) were sampled in order to elucidate the role of muscle as a potential storage. Results suggested that direct water-to-fish absorption rate was 20% d-1 per fish. Carps incorporated 14.3% of the absorbed 14C. Fish activity did not increase over days, due to a strong decrease in 14C concentration in the water (resulting from aquarium sorption). During trophic transfer experiments, food was entirely ingested and 14C sources rapidly assimilated. For either arginine or glucose, results suggested that 19-20% of ingested 14C was incorporated, yielding a significant increase in fish activity over days. No difference in mass-specific activity was observed among muscle and whole body. Total activity in the muscle represented 29%-32% of whole body activity, this proportion reflecting the contribution of muscle to whole body weight. During elimination experiments, results showed a significant decrease in whole body total activity and mass-specific activity with arginine. The decrease was not significant with glucose due to a great variability among fish. Results suggested that an essential amino-acid like arginine can be used as an energy source under starvation and that muscles can act as a storage for essential amino-acids

Evaluation of DGT and DGT-PROFS modeling approach to estimate desorption kinetics of Cs in soils

International audienceThe aim of this paper is to assess the suitability of DGT to extract kinetic rates of desorption of cesium (Cs) from soils. For this purpose, laboratory experiments with a natural soil spiked with Cs were carried out under three different contamination conditions, reflecting either an increase in Cs contamination level or an ageing of the contamination within the soil. The experimental results (i.e. the Cs accumulation kinetics onto DGT probes) were interpreted by the DGT-PROFS model. The latter calculates the partitioning of Cs between two particulate pools, describing weak and strong interactions respectively, as well as kinetic rates describing exchange reactions. It was shown that experimental conditions did not show any major impact on desorption rates, suggesting that desorption kinetics were not significantly affected by contamination level and ageing. Instead, the distribution of Cs among weak and strong sites was shown to be the predominant factor governing the differences observed in the remobilization of Cs to porewater among experimental conditions. The DGT technique combined with the DGT-PROFS modelling approach was proved to be efficient in estimating the desorption kinetic rates of Cs in soils