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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

A read across approach has been taken to fulfil this endpoint using a structurally similar substance as there is no availbale data for this substance.
The following key study was provided to fulfil the data requirement:
Hanstveit Ir. R. (2003) 1,3,2-Dioxastannepin-4,7-dione, 2,2-dibutyl- (CAS # 78-04-6, Dibutyltin maleate, DBTM): Determination of the ready biodegradability in a Manometric Respiration Test. Testing laboratory: TNO, Project Organisation, Ecotoxicology, Utrechtseweg 48, P.O. Box 360, 3700 AJ Zeist, The Netherlands. Owner company: Organotin Environmental Programme (ORTEP) Association, Stabilizer Task Force. Report No.: V4017/01. Report date: 2003-09-24
The biodegradation of dibutyltin maleate was determined in a study performed in compliance with GLP and to the methods OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test) and EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test). The study was considered reliable and adequate for assessment and accordingly assigned a reliability score of 2. The percentage degradation of 1,3,2-dioxastannepin-4,7-dione, 2,2-dibutyl- after 28 days of incubation was approximately 3% in a manometric respiration test at a test substance concentration of 37.7 mg.l-1, calculated from the Theoretical Oxygen Demand (ThODNH3) (1.38 mg O2.mg-1) of test substance. The biodegradation of 1,3,2-dioxastannepin-4,7-dione, 2,2-dibutyl- did not exceed the pass level of 60% ThODNH3 within 28 days and, therefore, is classified as not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

The key study Hanstveit Ir. R. (2003), was performed in compliance with GLP and to the guidelines OECD 301 F and EU Method C.4-D. The study was considered highly reliable and adequate for assessment and therefore assigned a reliabiltiy score of 2, due to it being read-across data. Under the conditions of the test dibutyltin maleate was found to not be readily biodegradable.

Read-across between dibutyltin compounds to dibutyltin methylmaleate concerning aquatic toxicity endpoints was considered appropriate as dibutyltin and octyltins are known to hydrolyse rapidly in water (as presented by Yoder 2003, under the data requirement hydrolysis), and form, in the case of dibutyltins, dibutyltin oxide.