He has extensive experience with in vitro system development and application, with PBPK modelling and with the theoretical and practical aspects of the risk assessment process. He has been the supervisor of over 12 PhD theses and has a list of more than 140 publications. He coordinated an EU project on the use of in vitro data in biokinetic modelling. He is the leader of two workpackages in the EU-funded integrated programme on alternative methods to estimate acute toxicity (A-Cute-Tox). He was from 1993-2002 a member of ECVAM Scientific Advisory Committee (ESAC) and is chairman of the ECVAM Task Force on Integrated Testing. He is an observer in IVTIP (In vitro Toxicity Industrial Platform). He is a member of the Health Council in the Netherlands, of the Dutch Board for the Accreditation of Pesticides and the Editor of the journal Toxicology in vitro.