Daniel Giesen

Research interests

The main interest of my research is the development, optimization and validation of quantitative structure-activity relationship (QSAR) toxicity models.

Based on the pore-water hypothesis the toxicity of organic compounds is governed by the freely dissolved fraction in the water phase. QSARs have been used to describe toxic effects to biota by using estimated porewater concentrations and the compounds’ lipophilicity. By using solid-phase microextraction (SPME) this (bio)available concentration can be measured and used to validate QSAR models used in environmental risk assessment and for REACh (Registration, Evaluation and Authorization of Chemicals), which rely on estimated porewater concentrations. A second approach is the identification of alternative compound properties, i.e. water-liposome partitioning, as alternative to the commonly used log Kow.

Furthermore, I am interested in determining sensitive life stages of test animals and the differentiation of a compound’s mode of action, time of action and life stage of action.

Selected Publications

Janssens, T.K.S., Giesen, D., Mariën, J., van Straalen, N.M, van Gestel, C.A.M, Roelofs, D (2011) Narcotic mechanism of acute toxicity of chlorinated anilines in Folsomia candida (Collembola) revealed by gene expression analysis. Environment International, 37: 929-939.

Submitted
Giesen, D., Jonker M.T.O., van Gestel, C.A.M (2011) Development and validation of data-based QSARs for the toxicity of chlorobenzenes to the soil dwelling springtail Folsomia candida. Environmental Toxicology and Chemistry

Research project

Development of QSARs for the toxicity of chemicals to the springtail Folsomia candida.

The PhD study is part of the EU-funded OSIRIS (Optimized Strategies for Risk Assessment of Industrial Chemicals through Integration of Non-Test and Test Information) project, wihch aims at developing Integrated Testing Strategies (ITS) fit for REACH that make it possible to significantly increase the use of non-testing information for regulatory decision making, and to effectively reduce animal testing to the level needed from a risk perspective.
  Our department works on the developments of QSARs for the toxicity of chemicals for Folsomia candida, taking into account the influence of soil properties and exposure pathway. In addition, the effects of a few selected chemicals on gene expression profiling of F. candida are determined and related to the lethal and sublethal effects at the individual level.

 

Example of a QSAR, showing the toxicity (expressed as its EC50, the concentration causing 50% reduction in reproduction of the springtail Folsomia candida) as a function of the lipophilicity (log Kow) of different test chemicals, tested in two different soil types.

Participants: Daniel Giesen, Kees van Gestel, Nico van Straalen