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Previous attempts at structure/biodegradability relations (SBRs) and available biodegradation data are reviewed and it is concluded that (1) not enough rate data on large numbers of chemicals are available to develop quantitative SBRs and (2) attempted qualitative SBRs have suffered from either poor documentation of the biodegradation evaluation or they have used limited biodegradation test data. Because of the poor reproducibility of biodegradation tests, a weight‐of‐evidence evaluation procedure is proposed. A system for collecting and evaluating biodegradation data from screening tests, biological treatment simulations, grab sample tests and field studies is described and study‐specific and summary biodegradability codes in combination with reliability codes are developed that can be used for structure/biodegradability relations.

A file of evaluated biodegradation data was used to develop a model for predicting aerobic biodegradability from chemical substructures. Chemicals initially were divided into three groups: (a) chemicals that degrade rapidly under most environmental conditions without requiring acclimation; (b) chemicals that are biodegradable, but only after an acclimation period; and (c) chemicals that degrade slowly or not at all. Chemicals in the first and last groups were then used to develop a model for classifying chemicals as rapidly biodegradable or not rapidly biodegradable. Two models, one based on linear regression and the other based on nonlinear regression, were developed from 35 preselected substructures. Both models predict the biodegradation categories correctly 90% of the time for the training set (264 chemicals) and an independent validation set (27 chemicals), and are 95% correct for chemicals that biodegrade rapidly.

The environmental fate/exposure data base (EFEDB) has been under development with U.S. Environmental Protection Agency support since 1979. It was initiated because of the difficulty of identifying environmental release, fate and exposure information using traditional literature searches. Two new components (BIOLOG and BIODEG), which contain microbial toxicity and biodegradation information, and an update of the overall EFEDB file are described. In addition, a chemical fate/exposure file (FATE/EXPOS) is discussed; it contains production and use data as well as physical‐chemical properties, chemical fate data and monitoring information. EFEDB has been greatly expanded since its initial development, and considerable conversions are planned to make most of the files available through the Chemical Information System (CIS). A major goal of EFEDB was to provide a source of data for constructing structure‐activity correlations and BIODEG is one of the first steps in providing evaluated data for such correlations. FATE/EXPOS provides sorting capabilities for setting priorities in testing or regulation based on easily obtainable information about exposure potential.

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