1,721,040 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Origines des différences de résultats fournis par un modèle multimédia simple et le modèle CALTOX : cas de l'estimation des risques par ingestion liés aux émissions de dioxines des grandes installations de combustion
No full textNational audienceWe have used a simple, conservative model, written in Excel, to calculate exposure by ingestion of2,3,7,8-tetrachlorodibenzodioxin due to atmospheric emissions from large combustion plants and their subsequent deposits. We then compared the results with those yielded by CALTOX and analyzed the reasons for the differences. In the case we studied, it was possible to obtain very similar results with both models after several changes made their underlying hypotheses comparable (using the same values for physicochemical parameters and the same exposure target characteristics, modifying one of the transfer hypotheses, and adapting the hazard quotient calculation in CALTOX). Even when the hypotheses of two models seem globally the same, specific differences can result in quite different results. For this reason, the details of the hypotheses underlying the model used should always be specified. Using a simple model can, at least in early study stages, improve the transparency of studies.L'exposition par ingestion de 2,3,7,8-tétrachlorodibenzodioxine, due aux retombées au sol des rejets atmosphériques de grandes installations de combustion, a été calculée par un modèle constitué d'équations simples et majorantes, écrites sous Excel. Les résultats obtenus ont été comparés à ceux fournis par CALTOX, modèle reconnu et respectant le principe de conservation de la masse. L'origine des différences de résultats fournis par les deux modèles a été recherchée. Dans le cas étudié, l'uniformisation des valeurs de paramètres physico-chimiques et des caractéristiques des cibles d'exposition considérées, la modification d'une des hypothèses de transfert et une adaptation du mode de calcul de l'indice de risque par CALTOX, ont permis de retrouver des résultats très proches avec les deux modèles. Même lorsque les hypothèses de deux modèles paraissent globalement identiques, quelques éléments particuliers peuvent conduire à l'obtention de résultats sensiblement différents, d'où la nécessité d'indiquer en détail les hypothèses de calcul prises en compte à travers le modèle employé. Utiliser un modèle simple, au moins dans un premier niveau d'étude, peut favoriser la transparence des études
Modes de transfert des PCDD/F et des PCB vers les plantes et définition de coefficients de transfert pour la modélisation
No full textInternational audienc
Améliorer les méthodes d’estimation prospective de l’exposition aux polluants des populations autour d’une Installation Classée pour la Protection de l’Environnement
No full textInternational audienceModels’ predictions for human exposure to lead emissions of facilities were assessed through: 1) comparing the results given by several models (from stacks’emissions to human blood concentrations) ; 2) comparing predicted concentrations to observed ones. 1) The results obtained depend on the models used. Calculations made with a deterministic approach can also be completely different from those obtained with the probabilistic approach. With a «reasonably conservative» approach, the level of conservatism is unknown and variable from a study to another one. According to the objective of the risk assessment study carried out (to check the absence of inacceptable risks, to achieve a surveillance program for example), if a probabilistic approach is not conducted, several point estimations can be required. 2) Two models were used for the comparison of the predicted concentrations with measurements. The fi rst one (A) provides the distribution of the media-specifi c lead concentrations (air, soil, fruit, vegetables and blood) in the whole area investigated, whereas the second (B) estimates the concentration of exposure of individuals living in the study area. Model A tended to overestimate the exposure due to exposed vegetables in the case study. Model B was tested for 9 children with contrasting exposure conditions. It managed to capture the blood levels for 8 of them. The interest of model B is to provide outputs with lower variance than model A, but further tests are necessary to conclude about its accuracy.En France, les études d’impact réalisées dans le cadre des procédures d’autorisation des Installations Classées pour la Protection de l’Environnement (ICPE) doivent prendre en compte l’impact sur la santé des populations (loi sur l’Air de 1996 et son article 19, circulaire de la DPPR du 19 juin 2000). La démarche d’évaluation des risques sanitaires (ERS) est la méthode préconisée pour caractériser le risque encouru par une population vivant dans la zone d’influence d’une ICPE. Dans ces études prospectives, l’étape d’évaluation des expositions repose fréquemment, hors situation de pollution avérée, sur une approche de modélisation, car ce sont les risques futurs qui sont évalués. Il est donc important d’acquérir des éléments d’information sur la qualité (précision et justesse) des estimations de l’exposition obtenus par modélisation
Analyse des transferts des dioxines et polychlorobiphényles vers les végétaux
No full textInternational audienc
Common errors in the use of the CALTOX model to assess the human health risks linked to industrial emissions of pollutants
No full textInternational audienceFrench environmental law for nature protection requires that all the facilities, works, and development projects that may affect the environment should be the subject of an impact study to evaluate their consequences, including on human health. For this analysis, the risk assessment approach is used and the population's exposure is estimated with the aid of multimedia models. The CalTOX model is frequently used for this kind of study. Unfortunately, the analysis of these studies shows that the model is often badly understood and poorly used. The difficulties encountered by the users, the errors and the problems met in the interpretation of results, which are the most commonly found in the human exposure assessment, are listed and their consequences illustrated. CalTOX has been shown to have many advantages (adaptability, speed in carrying out calculations, transparency), but it ought not to be used as a "black box" because such a use may lead to many errors and a loss of confidence in the studies
Origines des différences de résultats fournis par un modèle multimédia simple et le modèle CALTOX : cas de l'estimation des risques par ingestion liés aux émissions de dioxines des grandes installations de combustion
No full textNational audienceWe have used a simple, conservative model, written in Excel, to calculate exposure by ingestion of2,3,7,8-tetrachlorodibenzodioxin due to atmospheric emissions from large combustion plants and their subsequent deposits. We then compared the results with those yielded by CALTOX and analyzed the reasons for the differences. In the case we studied, it was possible to obtain very similar results with both models after several changes made their underlying hypotheses comparable (using the same values for physicochemical parameters and the same exposure target characteristics, modifying one of the transfer hypotheses, and adapting the hazard quotient calculation in CALTOX). Even when the hypotheses of two models seem globally the same, specific differences can result in quite different results. For this reason, the details of the hypotheses underlying the model used should always be specified. Using a simple model can, at least in early study stages, improve the transparency of studies.L'exposition par ingestion de 2,3,7,8-tétrachlorodibenzodioxine, due aux retombées au sol des rejets atmosphériques de grandes installations de combustion, a été calculée par un modèle constitué d'équations simples et majorantes, écrites sous Excel. Les résultats obtenus ont été comparés à ceux fournis par CALTOX, modèle reconnu et respectant le principe de conservation de la masse. L'origine des différences de résultats fournis par les deux modèles a été recherchée. Dans le cas étudié, l'uniformisation des valeurs de paramètres physico-chimiques et des caractéristiques des cibles d'exposition considérées, la modification d'une des hypothèses de transfert et une adaptation du mode de calcul de l'indice de risque par CALTOX, ont permis de retrouver des résultats très proches avec les deux modèles. Même lorsque les hypothèses de deux modèles paraissent globalement identiques, quelques éléments particuliers peuvent conduire à l'obtention de résultats sensiblement différents, d'où la nécessité d'indiquer en détail les hypothèses de calcul prises en compte à travers le modèle employé. Utiliser un modèle simple, au moins dans un premier niveau d'étude, peut favoriser la transparence des études
MODUL'ERS : a modular computing tool for HHRA due to contaminated sites and emissions from facilities
No full textIn France, risk assessment studies have to be conducted before the implementation or the enlargement of some new facilities and before the reuse of some contaminated sites. These studies have to be performed in accordance to four principles : precautionary, specificity, proportionality, transparence. Until now, no devoted software has been developed in France to assess future exposure and risks for such studies. Because of that, many problems have been reported in exposure assessment studies leading to inconsistency between risk assessment studies and a lack of confidence in results provided. To improve the practices and the transparency of the estimates obtained in these studies, INERIS develops and diffuses modeling tools in the framework of one's missions for the Ministry in charge of the Environment. A peer-reviewed handbook, entitled 'Sets of equations for modeling exposure linked to soil contamination or emissions from an industrial facility', has been published and is available on INERIS'website. This document presents the equations used at INERIS for estimating the media concentrations, the exposure and risk levels. It also describes the origin of these equations and underlines the hypotheses on which they are built and their limits. A modeling and simulation platform (MODUL'ERS) based on the equations presented in this handbook has also been developed. Our main objectives during its conception were to provide a tool (1) suited to different site conditions and tier studies, (2) transparent for any stakeholders and helpful to perform uncertainties analysis. MODUL'ERS consists in a library of preset modules enabling the users to build models in accordance with the site conceptual model (that is to say the pathways from the source to the receptor), by downloading modules and connecting them, to create an exposure matrix. Many options are also available to create a customized application. To improve transparency of studies all the equations, parameters can be viewed by the users, as well all the intermediate calculations performed. Especially, hyperlinks enable to browse among variables and their equations. The first version of the tool will be available at soon. Coupling with a GIS is forecast. Some reports will be also published to make more transparent the assignment of values to input parameters, by describing the values collected and the choices made (best-estimate, ranges, probabilistic distributions)
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