PERPEST is a model that Predicts the Ecological Risks of PESTicides in freshwater ecosystems. This system predicts the effects of a particular concentration of a pesticide various (community) endpoints, based on empirical data extracted from the literature, see figure 1. The method that it uses is called Case-Based Reasoning (CBR), a technique that solves new problems  (e.g., what is the effect of pesticide) by using past experience (e.g., published microcosm experiments). The database containing the "past experience" has been constructed by performing a review of freshwater model ecosystem studies evaluating the effects of pesticides. This review assessed the effects on various endpoints (e.g. community metabolism, phytoplankton, macro-invertebrates) and classified them according to their magnitude and duration.

The PERPEST model searches for situations in the database which resemble the question case, based on relevant (toxicity) characteristics of the compound.

This allows the model to predict effects of pesticides for which no evaluation on a semi-field scale have been published. PERPEST results in a prediction showing the probability of classes of effects (no, slight or clear effects, plus an optional indication of recovery) on the various grouped endpoints. The model is described in the scientific paper written by Van den Brink et al. (2002). Please use the Contactform on the menu to request more information about PERPEST.


Currently there are three versions to download of the PERPEST model:

  1. The original version that is released in 2003 and described in Van den Brink et al., 2002 and 2005. The manual of this version is available (Van Nes and Van den Brink, 2003)
  2. Released in 2007 and has an extended data base. The first version could only predict the effects of insecticides and herbicides whereas the second version also includes fungicides. This version can also evaluate the effects of insecticide, herbicide and fungicide mixtures, separately. For this version no updated manual is available but is thoroughly tested.
  3. Released in 2009 and can predict the effects based on more complex exposure endpoints than the peak alone. It can predict the effects of single and multiple applications on the basis of the highest peak concentration and 7-day and 21-day Time Weighted Average concentrations. in 2010 the model will be elaborated so it can also deal with mixtures of insecticides, herbicides and fungicides, after which it will be thoroughly tested. In 2010 also an updated manual will be available.


Perpest output

figure 1. Example of output from Perpest



  • Maintenance and improvement of the TOXSWA model to support its use by the Dutch Board for the Authorizaton of Pesticides and Biocides(Ctgb) and phytopharmoceutical industries.
  • Further development of the TOXSWA model, including its user interface, consisting of e.g. improved pesticide process descriptions, hydrology or coupling to entry route models.
  • Development of methods to consider regional variation for the calculation of PECs, with special attention to the degradation rate of pesticides in different aquatic systems.