Revisiting simplified DEBtox models for analysing ecotoxicity data

Mechanistic effect models are gaining increasing interest in ecotoxicology and environmental risk assessment (ERA). For explaining effects on an individual's life-history traits (e.g., growth and reproduction), DEBtox is the leading toxicokinetic-toxicodynamic (TKTD) modelling approach. DEBtox is the application of a model based on dynamic energy budget (DEB) theory to toxic effects, but the term is generally used to refer to practical simplified models from this theoretical framework. The DEBtox approach has remained relatively unchanged over the last few decades, but an updated model is urgently needed. The need for revision is triggered by three, relative recent, developments: the broad acceptance of simple TKTD models for survival (GUTS), the development and successful application of reserve-less DEB models for invertebrates (DEBkiss), and the concrete interest in DEBtox from the field of ERA for pesticides in Europe. In this paper, an updated DEBtox model is presented that is based on DEBkiss, follows the TKTD formulation as established for GUTS (i.e., explicitly taking damage into consideration), and includes a starvation module that is essential for time-varying exposure (as some toxicant action mechanisms may induce starvation). The updated model is illustrated with a case study for springtails exposed to chlorpyrifos in food, and may find applications in science as well as in the regulatory arena.