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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

12-24% degradation within 28 days  (% of COD) and 8-17% degradation (% ThOD). COD = 2.06 mg O2/mg (OECD 302 C)

Key value for chemical safety assessment

Additional information

Three studies have been conducted evaluating the ready biodegradation of 2,6-di-tert-butylphenol.

·        inherent biodegradability

·        anaerobic aquatic biodegradation

·        ready biodegradability

In the key study, 2,6-di-tert-butylphenol was evaluated for its inherent biodegradability. The test substance attained between 12-24% degradation within 28 days calculated from oxygen uptake (% of COD) and between 8-17% degradation (% ThOD) and cannot, therefore, be considered as inherently biodegradable under the strict terms and conditions of the OECD Guidelines.

 

Test method:

The method used followed that described in the OECD Guidelines for Testing of Chemicals / Section 2: Degradation and Accumulation, Test No. 302C "Inherent Biodegradability, Modified MITI Test (II)". A mixed population of activated sewage sludge microorganisms was used as inoculum and aniline as reference substance. Initial concentration of test substance was 30 mg/l and reference substance 100 mg/l. TOC analysis of 2,6-di-tert-butylphenol was not possible due to the insoluble nature of the test material. A modified MITI test was carried out due to this fact. A COD value of 2.06 mg O2/mg was obtained for the test material.

A study was conducted to assess the anaerobic aquatic biodegradation. Under the conditions of this study, 2,6-di-tert-butylphenol did not biodegrade.

Test method:

The anaerobic aquatic metabolism of 14C-2,6-di-tert-butylphenol was investigated in primary sludge from an anaerobic digestor, representative of an intended 2,6-di-tert-butylphenoluse site according to EPA OTS 796.3140 (Anaerobic Biodegradability of Organic Chemicals) guideline. At weekly sampling intervals over a 56 day study, aliquots of the sludge were analyzed to determine the rate of biodegradation of 14C-2,6-di-tert-butylphenol. Results of this study determined that 2,6-di-tert-butylphenol did not degrade under the conditions of this study. The reference material, ethanol, demonstrated significant degradation.

A further study was conducted to assess the ready biodegradability of2,6-di-tert-butylphenol using the Modified Sturm Test.

Test method:

The purpose of the study was to measure the test substance's ready biodegradability as measured by CO2 formation in percent of theoretical CO2calculated from the total organic carbon content in accordance with OECD Guideline 301 B (Ready Biodegradability: CO2Evolution Test). The test substance was cultured with bacteria collected from a sewage treatment plant and CO2evolution was measured. Aniline was used as a positive control for this study. Results of the test showed that 2,6-di-tert-butylphenol is not readily biodegradable as measured by this method.