Welcome

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 team.

 

Thank you for visiting,

Roman Ashauer

 

News

Death Dilemma and Organism Recovery in Ecotoxicology

Why do some individuals survive after exposure to chemicals while others die? Either, the tolerance threshold is distributed among the individuals in a population, and its exceedance leads to certain death, or all individuals share the same threshold above which death occurs stochastically. The previously published General Unified Threshold model of Survival (GUTS) established a mathematical relationship between the two assumptions. According to this model stochastic death would result in systematically faster compensation and damage repair mechanisms than individual tolerance. Thus, we face a circular conclusion dilemma because inference about the death mechanism is inherently linked to the speed of damage recovery. We provide empirical evidence that the stochastic death model consistently infers much faster toxicodynamic recovery than the individual tolerance model. Survival data can be explained by either, slower damage recovery and a wider individual tolerance distribution, or faster damage recovery paired with a narrow tolerance distribution. The toxicodynamic model parameters exhibited meaningful patterns in chemical space, which is why we suggest toxicodynamic model parameters as novel phenotypic anchors for in vitro to in vivo toxicity extrapolation. GUTS appears to be a promising refinement of traditional survival curve analysis and dose response models. (Published in Environmental Science & Technology, open access)

Death Dilemma and Organism Recovery in Ecotoxicology
41 Death dilemma and organism recovery.p
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Importance of Toxicokinetics for Interspecies Variation in Sensitivity to Chemicals

Imaging the distribution of a pesticide in a freshwater snail and a shrimp. Credit: Eawag/Harlan Laboratories
Imaging the distribution of a pesticide in a freshwater snail and a shrimp. Credit: Eawag/Harlan Laboratories

Interspecies variation in sensitivity to synthetic chemicals can be orders of magnitude large. Species traits causing the variation can be related to toxicokinetics (uptake, distribution, biotransformation, elimination) or toxicodynamics (interaction with biological target sites). We present an approach to systematically measure and model the contribution of uptake, biotransformation, internal distribution, and elimination kinetics toward species sensitivity differences. The aim is to express sensitivity as target tissue specific, internal lethal concentrations. A case study with the pesticides diazinon, imidacloprid, and propiconazole and the aquatic invertebrates Gammarus pulex, Gammarus fossarum, and Lymnaea stagnalis illustrates the approach. L. stagnalis accumulates more pesticides than Gammaridae when measured in whole organisms but less in target tissues such as the nervous system. Toxicokinetics, i.e. biotransformation and distribution, explain the higher tolerance of L. stagnalis to the insecticide diazinon when compared to Gammaridae. L. stagnalis was again more tolerant to the other neurotoxicant imidacloprid; however, the difference in sensitivity could not be explained by toxicokinetics alone, indicating the importance of toxicodynamic differences. Sensitivity to propiconazole was comparable among all species and, when expressed as internal lethal concentrations, falls in the range of baseline toxicity. (published in Environmental Science & Technology)

Importance of Toxicokinetics for Interspecies Variation in Sensitivity to Chemicals
37 Importance of toxicokinetics for inte
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Minimised Bioconcentration Tests: A Useful Tool for Assessing Chemical Uptake into Terrestrial and Aquatic Invertebrates?

Read our paper here (free access).

PhD position available: "Pharmaceutical Impacts in Aquatic Sediments". More information here.


Do you want to join our team? If you are a PostDoc and want to apply for a Marie-Curie IEF please get in touch.