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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Two ready biodegradability studies were carried out on Geniset MD as follows:
An assessment of ready biodegradability of Gel-All MD (Douglas & Handley 1988) based on OECD Guideline No. 301D "Closed bottle Test" attained a degradation rate of 2% after 28 days.
Based on this result Gel-All MD cannot therefore be considered as readily biodegradable.
An assessment of the Biodegradability of Geniset MD (Handley, Mead and Bartlett 1993) based on OECD Guideline No. 301C "Modified MITI Test" attained a degradation rate of 10% after 28 days.
Results of analyses suggested that Geniset MD showed no biodegradation.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

Both biodegradation studies were carried out to GLP Standards and OECD Guidelines

Both studies gave the same conclusion of the substance being non-biodegradable and as such the decision to assign Key Study was based on the details of the results.

In the interests of maintaining assessments based on a worst case scenario the Key study assignment was given to the study that showed the lowest level of degradation i.e. Douglas & Handley 1988. This study produced a degradation rate of only 2% after 28 days.

Key Study (Douglas & Handley 1988):

The Test Substance Gel-All MD was assessed for ready biodegradability over a 28 day period.

The test was conducted using the closed bottle test according to OECD Guideline No. 301D and EEC Directive 67/548 Annex V C6. as published in 84/449/EEC.

Test concentration: 2 mg/L

Oxygen depletion (28 days): 0.100 mg O2/L

Theoretical oxygen demand (ThOD): 4.2 mg O2/L

Percentage biodegradation (28 days): 2 %

Gel-All MD attained between 2 and 7% degradation within 28 days and cannot, therefore, be considered as readily biodegradable.

Sodium benzoate (reference substance) attained 83% degradation within 28 days. Oxygen depletions in the inoculated and non-inoculated control series were within prescribed limits.

Supporting Study:

Test Type: Assessment of Biodegradability based on OECD Guideline No. 301C "Modified MITI Test" with modifications as outlined within the report and the requirements of the Japanese Ministry of International Trade and Industry's Chemical Substances Control Law (Law No. 117, 1973). The study followed the methodology outlined in the MITI Gazette, 19 July 1974 under paragraph 7 - 1: Chemical Substances by Micro-organisms.

Inoculum: Activated sludge micro-organisms have been selected following recommendations in the OECD Guidelines.

Duration: 28 days

Criteria:

a) Oxygen consumption

b) Compound specific analysis

c) Dissolved Organic Carbon analysis

d) Chemical Oxygen Demand

Results

Geniset MD attained a degradation rate from oxygen consumption values of 10% after 28 days. Results of the compound specific analyses suggested that Geniset MD showed no biodegradation.