Factors for intermedia extrapolation in biodegradability assessment

In screening-level biodegradability assessment for xenobiotic chemicals it is often necessary to extrapolate from one environmental medium or set of conditions to another, to derive an estimate of biotransformation rate in the medium of interest. To develop a basis for such extrapolation we conducted a comparative analysis of biodegradation data from grab sample studies, focusing on (i) relative rates of aerobic biodegradation in fresh water and surface soil; and (ii) relative rates of aerobic and anaerobic biodegradation in surface soil. The results of this data review are expressed as a series of factors that represent ratios of biodegradation half-lives under the respective conditions. These factors may be used in chemical screening and in setting priorities for further review.