Pollution, stochasticité at hétérogénéité spatiale dans la dynamique d'une population de truites présentatnt une structure d'âge et vivant dans un réseau de rivières

International audienceWe report the strategy adopted for the modeling of a resident brown trout population living in a theoretical river network. We consider chronic cadmium pollution occurring in one stretch of river. Using RAMAS Metapop, spatial modeling allows us to integrate spatial heterogeneity influencing the population dynamics and also influenced by the heterogeneity of the environmental contamination. We show how to perform the assessment of global impact of pollution from local perturbations using this modeling step: we build for instance population level dose-response curves linking population features with pollutant concentrations. We take advantage of the flexibility of RAMAS Metapop to deal with demographic stochasticity in order to discuss the use of deterministic models or stochastic models (extinction risk concepts) to provide population endpoints for decision-making. Besides, we confirm the conclusion of a previous contribution focused on the potential effect of migratory disruptions due to pollution: random variations in the dispersal pattern during the breeding event expand the extinction risk of the trout population. So increasing efforts are necessary to develop knowledge relative to toxicant-induced spatial behaviors and to integrate such effects in the definition of environmental quality criteria

Passive sampling methods for contaminated sediments: risk assessment and management

This paper details how activity-based passive sampling methods (PSMs), which provide information on bioavailability in terms of freely dissolved contaminant concentrations (Cfree), can be used to better inform risk management decision making at multiple points in the process of assessing and managing contaminated sediment sites. PSMs can increase certainty in site investigation and management, because Cfree is a better predictor of bioavailability than total bulk sediment concentration (Ctotal) for 4 key endpoints included in conceptual site models (benthic organism toxicity, bioaccumulation, sediment flux, and water column exposures). The use of passive sampling devices (PSDs) presents challenges with respect to representative sampling for estimating average concentrations and other metrics relevant for exposure and risk assessment. These challenges can be addressed by designing studies that account for sources of variation associated with PSMs and considering appropriate spatial scales to meet study objectives. Possible applications of PSMs include: quantifying spatial and temporal trends in bioavailable contaminants, identifying and evaluating contaminant source contributions, calibrating site-specific models, and, improving weight-of-evidence based decision frameworks. PSM data can be used to assist in delineating sediment management zones based on likelihood of exposure effects, monitor remedy effectiveness, and, evaluate risk reduction after sediment treatment, disposal, or beneficial reuse after management actions. Examples are provided illustrating why PSMs and freely dissolved contaminant concentrations (Cfree) should be incorporated into contaminated sediment investigations and study designs to better focus on and understand contaminant bioavailability, more accurately estimate exposure to sediment-associated contaminants, and better inform risk management decisions. Research and communication needs for encouraging broader use are discussed

Application of the tissue residue approach in ecological risk assessment

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A Cancer Research UK multicenter randomized phase II study of induction chemotherapy followed by gemcitabine- or capecitabine-based chemoradiotherapy for locally advanced nonmetastatic pancreatic cancer.

TPS222Background: around 7,400 patients are diagnosed with pancreatic cancer in the UK each year and mortality from the disease parallels its incidence, indicating that an effective treatment is required. Localized inoperable cancer accounts for 30-40% of advanced disease and its optimal management is unclear. Chemotherapy alone is the predominant modality in the UK while CRT is the treatment of choice in the USA. It has been reported that participants receiving either modality have a median survival in the region of 10 months. Nonrandomized studies have shown that selected participants who attain stable or responsive disease after 3 to 4 months of induction chemotherapy may benefit from consolidation CRT. Both gemcitabine and capecitabine have been shown to be potential radiosensitisers.Methods: the Cancer Research UK funded National Cancer Research Institute SCALOP trial is a two-arm randomized phase II trial using a Fleming's single stage design for each arm. Patients will receive 16 weeks of GEMCAP induction chemotherapy; 76 of those who have responded, or have stable disease, will then be randomised to receive 5.5 weeks of either gemcitabine- or capecitabine-based consolidation chemoradiation (50.4 Gy in 28 fractions with either gemcitabine 300 mg/m2 weekly or capecitabine 830mg/m2 bd ). The trial will assess: 1) What are the activity, toxicity, and feasibility of use of the regimens and does either justify consideration as an arm in a future phase III trial? 2) Is it possible to deliver high quality CRT across centres in the UK? 3) In participants who progress following induction chemotherapy, what is the pattern of care in UK centres and what is their prognosis? The trial incorporates a radiotherapy quality assurance element consisting of a radiotherapy protocol, a test case that must be successfully completed before recruitment can begin at a centre, and ongoing assessment of all plans for compliance with protocol. The trial will also store blood samples for future translational studies. The trial has just opened to recruitment in 5 centers in the UK with 23 further centers in set up.No significant financial relationships to disclose