Conceptual, mathematical and simulation models are important and exciting, because they capture general principles of a scientific area and because they can make
predictions.This website is about the development of ecotoxicological models, the research focus of my
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We are inviting applications for a one-year position suitable for candidates holding a PhD or equivalent research experience. The position is funded by the University of York's Centre for Chronic Diseases and Disorders and aims to investigate what new knowledge can be extracted with GUTS when applied in human toxicology and medical research.
We are very pleased to announce that our session “Beyond concentration response – mechanistic organism level effect modeling” has been accepted for the SETAC-EU conference in Basel (May 2014). The session is in the track "Effect modeling and predictive toxicology".
We welcome studies on any organism and any pollutant, including mixtures and multiple stressors. Presentations about unifying frameworks, generally applicable models and comprehensive studies that compare several organisms or stressors are encouraged, as well as systematic investigations into relationships between model parameters and physical-chemical properties or species traits. We will give priority to studies where model predictions are confronted with data. The focus of the session shall be on the combination of theoretical and experimental approaches and we encourage discussion of model choice, predictive power, data requirements and model complexity.
You can submit your abstract here. We’re looking forward to your submissions!
Elke Zimmer and Roman Ashauer
Abstract: Exposure and depuration experiments for Gammarus pulex and Daphnia magna were conducted to quantitatively analyze biotransformation products (BTPs) of organic micropollutants (tramadol, irgarol, and terbutryn). Quantification for BTPs without available standards was performed using an estimation method based on physicochemical properties. Time-series of internal concentrations of micropollutants and BTPs were used to estimate the toxicokinetic rates describing uptake, elimination, and biotransformation processes. Bioaccumulation factors (BAF) for the parents and retention potential factors (RPF), representing the ratio of the internal amount of BTPs to the parent at steady state, were calculated. Nonlinear correlation of excretion rates with hydrophobicity indicates that BTPs with lower hydrophobicity are not always excreted faster than the parent compound. For irgarol, G.pulex showed comparable elimination, but greater uptake and BAF/RPF values than D.magna. Further, G. pulex had a whole set of secondary transformations that D. magna lacked. Tramadol was transformed more and faster than irgarol and there were large differences in toxicokinetic rates for the structurally similar compounds irgarol and terbutryn. Thus, predictability of toxicokinetics across species and compounds needs to consider biotransformation and may be more challenging than previously thought because we found large differences in closely related species and similar chemical structures.
Published in Environmental Science & Technology (link to paper at ES&T).
Abstract: Organisms in the environment experience fluctuating, pulsed, or intermittent exposure to pollutants. Accounting for effects of such exposures is an important challenge for environmental risk assessment, particularly given the simplified design of standard ecotoxicity tests. Dynamic simulation using toxicokinetic-toxicodynamic (TK-TD) models describes the processes that link exposure with effects in an organism and provides a basis for extrapolation to a range of exposure scenarios. In so doing, TK-TD modeling makes the risk assessment more robust and aids use and interpretation of experimental data. Toxicokinetic-toxicodynamic models are well-developed for predicting survival of individual organisms and are increasingly applied to sublethal endpoints. In the latter case particularly, linkage to individual-based models (IBMs) allows extrapolation to population level as well as accounting for differences in effects of toxicant exposure at different stages in the life cycle. Extrapolation between species remains an important constraint because there is currently no systematic understanding of species traits that cause differences in the relevant processes. Toxicokinetic-toxicodynamic models allow interrogation of exposure profiles to determine intrinsic toxicity potential rather than using absolute maximum concentrations or time-weighted averages as surrogates. A decision scheme is proposed to guide selection of risk assessment approaches using dose extrapolation based on Haber's Law, TK-TD models, and/or IBMs depending on the nature of toxic effect and timing in relation to life history.
Published in Integrated Environmental Assessment and Management (link to paper at IEAM).