GROUP-CONTRIBUTION METHOD FOR PREDICTING PROBABILITY AND RATE OF AEROBIC BIODEGRADATION

Two independent training sets were used to develop four mathematical m odels for predicting aerobic biodegradability from chemical structure. All four of the models are based on multiple regressions against coun ts of 36 preselected chemical substructures plus molecular weight. Two of the models, based on linear and nonlinear regressions, calculate t he probability of rapid biodegradation and can be used to classify che micals as rapidly or not rapidly biodegradable. The training set for t hese models consisted of qualitative summary evaluations of all availa ble experimental data on biodegradability for 295 chemicals. The other two models allow semi-quantitative prediction of primary and ultimate biodegradation rates using multiple linear regression. The training s et for these models consisted of estimates of primary and ultimate bio degradation rates for 200 chemicals, gathered in a survey of 17 biodeg radation experts. The two probability models correctly classified 90% of the chemicals in their training set, whereas the two survey models calculated biodegradation rates for the survey chemicals with R2 is-ap proximately-equal-to 0.7. These four models are intended for use in ch emical screening and in setting priorities for further review.