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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Methyl-p-toluate is regarded to be readily biodegradable (by weight of evidence including read across to methyl benzoate and QSAR results)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Benzoic acid methyl ester, structurally very closely related to the submission substance and in the HPV programme of US-EPA grouped in one sub-category together with the submission substance (sub-category Benzyl and Benzoate Esters), was tested for ready biodegradablility in two different studies using the same method, the CO2 evolution test (OECD 301B). US-EPA rated both tests for reliability and concluded, that these tests are valid without restrictions.

In the first test (US EPA reference: Quest International Ltd (1995b) The biodegradability of methyl benzoate in the sealed vessel test. Unpublished report.) within 28 days benzoic acid methyl ester was biodegraded by 95.3% (CO2 -evolution, determined from 4 replicates). The inoculum used was secondary effluent from an unacclimatised activated sludge. The 10 -day window requirement of the OECD guideline was fulfilled.

In the second test (US EPA reference: Corby J. E. (1995) EPA: CO2 Production Test C-2000. Hoechst Celanese Corporation. Unpublished report; performed compliant to GLP) two concentrations of benzoic acid methyl ester were tested, with 10 and 20 mg test item per liter. Within 15 days the test item was biodegraded by >80% (CO2 -evolution, biodegradation rate similar for both test item concentrations). The inoculum used was activated sludge (microbial content: 8.4 million CFU/mL) mixed liquor collected from the Downingtown Regional Water Pollution Control Center (Downingtown, PA). The 10-day window requirement of the OECD guideline was fulfilled.

By read-across from the very similar substance benzoic acid methyl ester and thus following US EPH HPV programme, also the submission substance, methyl-p-toluate is regarded to be readily biodegradable.

This is supported by different QSAR models (BIOWIN modules of US EPA EPI Suite; OECD models developed by Degner, OECD QSAR Toolbox), which all arrive at the same conclusion: Fast / ready biodegradability.

By weight of evidence from read across to benzoic acid methyl ester and results from different QSAR models for the submission substance itself it is concluded that the submission substance is readily biodegradable.