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Biodegradation in water: screening tests

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Description of key information

Not readily biodegradable

Key value for chemical safety assessment

Additional information

No studies on "Biodegradation in water" are available for the substance in itself.

Nevertheless studies conducted with an analogue molecule (Similar Substance 01) were considered to complete the assessment. Further information are reported in the Read Across justification attached to section 13.


The first ready biodegradability evaluation (Huntsman, 1993; Huntsman, 1994) was made by two studies in which BOD5 and COD were calculated. The studies were conducted following ISO 5815 Second Edition 1989-08-01 (E) corresponding to 92 / 96 / EEC C.5 and DEV DIN 38'409 - H 41-1 (1980) corresponding to 92 / 96 / EEC C.6, respectively.

The tested concentrations for BOD5 assessment ranged from 6.4 and 824.6 mg/l. The concentration of substance for COD assessement was 2.5 mg/l. The BOD5 value was 6 mg O2/g obtained at the maximum concentration of the substance tested; the COD value was 1113 mg O2/g.

In agreement with the "Guidance on the Application to the CLP Criteria", for biodegradation test performed in less than 28 days, the ready biodegradability of a substance can be assessed calculating the BOD5/COD ratio. If the result is >= than 0.5 the substance can be considered readily biodegradable.

In this case the substance cannot be considered as readily biodegradable because the BOD5/COD ratio is below the 0.5 value.

An analogue consideration can be made for the second study (Huntsman, 1984) performed to assess the ready biodegradability of the substance. In this case the BOD5 was tested at concentrations ranging from 1 to 500 mg/l. The COD determination was performed using 1 g/l of substance. The BOD5 value was 0 mg O2/g and the COD value was 1562.7 mg O2/g. As mentioned above the BOD5/COD ratio was below the 0.5, therefore the substance is confirmed to be non readily biodegradable.


To assess the potential of the substance under registration to be inherently bodegradable, a study ws performed according to EEC Directive, L133 (pp. 99-105) Volume 31, May 88 (ISSN 0378-6978) according to OECD Guideline for Testing of Chemicals No. 302B, Paris 1981.

The initial concentration of test substance was 150 mg/l approximately. The DOC was determined for 28 days. During the first 3 hours was observed an adsorption of 25.9 %. After 28 days the bioelimination of the substance measured as DOC (mg/l) was 44.2 %.

Based on the available information, the substance can be considered as not readily biodegradable.