Biodegradability, ready/inherent

As shown in Table 1, many FMs meet the biodegradation criteria of a ready or inherent test. If a FM meets the criteria of a ready test, with or without acclimation, a first-order biodegradation rate of 3 h 1 in activated sludge can be assumed [ 1 ]. For FMs that show extensive biodegradation but fail the ready test criteria, a first-order rate of 0.3 h 1 can be assumed for activated sludge treatment [1]. 

Table 1 also indicates that some FMs, including the PCMs and NMs, do not pass ready or inherent biodegradation tests. However, this does not mean that these FMs do not undergo biotransformation to polar metabolites under realistic conditions. These realistic biodegradation tests may be conducted in vitro, in bench-top die-away studies, or as continuous activated sludge and porous pot tests. Ideally, the conditions should include (1) realistic FM concentrations... 

Table 9.1 Biodegradability (in %) of selected pharmaceuticals from various classes in different OECD tests (Kiimmerer and co-workers, unpublished work) [46, 99, 106, 110]. Criterion for ready biodegradability in 301 tests and inherent biodegradability in 302 tests is > 60%.

Table 16.2 Proposed scheme for using ready or inherent biodegradation test data to assign half-lives or rate constants for use in screening-level chemical assessment or modeling [16].

US Environmental Protection Agency (2000) Interim Guidance for Using Ready and Inherent Biodegradability Tests to... 

Table 2 Using ready and inherent biodegradability data to derive input data for the EQui-librium Criterion (EQC) model [35]. Multimedia fate models like the EQC model require compartmental half-lives for air, water, soil, and sediment. The scheme in the table is offered as an interim procedure for assigning half-lives for input to such models. These are bulk half-lives (i.e., for the compartment as a whole). They are not to be interpreted as (necessarily) half-lives for any specific process, such as biodegradation. No assumptions which compromise their interpretation as bulk half-lives should be made, including, for example, the assumption that biodegradation is the important process and occurs in soil pore water only. Air half-lives are not addressed here and it is assumed that data for input to models are either measured or derived from AOPWIN or similar methodology.

OECD Guidelines for Testing Chemicals, Paris 1981/1987 no. 201-209 Effects on Biotic Systems, no. 301 Ready Biodegradability, no. 302 Inherent Biodegradability, no. 303 Simultation Test, no. 304 Biodegradability in Soil, no. 305 Bioaccumulation, no. 401 -482 Health Effects. 

The OECD Guidelines for Testing of Chemicals [2] is the first publication in which specifications for biodegradability were mentioned with requirements for ready and inherent biodegradability. 

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