Biodegradation and Quantitative Structure-Activity Relationship (QSAR)

The biodegradability of organic compounds in terrestrial and aquatic systems is one of the most important factors related to their environmental fate, their adverse effects to humans and the environment and, consequently, their chemical risk assessment. Today there is an array of models for classifying the biodegradability of organic chemicals. Those models range from the simple group contribution models, models based on chemometric methods up to the expert systems based on various artificial intelligence techniques. The objectives of this report are (i) to review and evaluate the published biodegradability classification models and (ii) to recommend the reliable procedures for estimating biodegradability of organic chemicals in the environment. The evaluation procedure has shown that the majority of biodegradability models evaluated in this review have classification rates in the 85-90% range and thus all have a solid classification power. The recommended procedure is to use all evaluated and available models for classifying biodegradability of organic chemicals, i.e. the appropriate BIOWIN model, the set of structural rules, the MultiCASE system, the appropriate CATABOL model and the multivariate PLS model. If there is a consensus between applied models, classification of biodegradation may be considered as very reliable. However, if there is agreement between only four or three of those models, such classification should be considered as reliable or only reasonable, respectively.