FACTORS FOR INTERMEDIA EXTRAPOLATION IN BIODEGRADABILITY ASSESSMENT

In screening-level biodegradability assessment for xenobiotic chemical s it is often necessary to extrapolate from one environmental medium o r set of conditions to another, to derive an estimate of biotransforma tion rate in the medium of interest. To develop a basis for such extra polation we conducted a comparative analysis of biodegradation data fr om grab sample studies, focusing on (i) relative rates of aerobic biod egradation 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 r atios of biodegradation half-lives under the respective conditions. Th ese factors may be used in chemical screening and in setting prioritie s for further review.