Dibutylbis(pentane-2,4-dionato-O,O')tin

Biodegradation in water: screening tests

Description of key information

A read across approach has been taken to fulfil this endpoint using structurally similar substance as there is no availbale data for this substance. Two studies were assessed:
Both studies were well documented and performed in compliance with GLP and to the OECD guideline 301F. As such the studies were deemed adequate for assessment, and both were assigned a reliability score of 2.
Hanstveit, R. (2003) Dibutylbis[(1-oxododecyl)oxy]stannane (CAS#  77-58-7, dibutyltin dilaurate, DBTL): Determination of the ready biodegradability in a Manometric Respiration Test. Testing Laboratory: TNO Nutrition and Food Research, Department of Environmental Toxicology. Report No.: TNO Report No. V4015/01. Report date: 2003-06-25.
Dibutyltin dilaurate was biodegraded 23% in a manometric respiration test at a test concentration of 22.2 mg/L after 39 days of incubation. Based on these results, dibutyltin dilaurate is considered not ready biodegradable.
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 percentage degradation of dibutyltin maleate 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 ThODNH3 (1.38 mg O2.mg-1) of test substance. The biodegradation of dibutyltin maleate did not exceed the pass level of 60% ThODNH3 within 28 days and, therefore, is classified as not readily biodegradable.
Using a read-across approach, from the available data, it can be concluded that the substance in question is not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

Two studies were submitted for assessment on a read-across basis as no data was available on the substance of interest. Both studies were conducted by Hanstveit, R. (2003) on dibutyltin dilaurate and dibutyltin maleate respectively. The studies were both of high reliability, as both were performed to OECD 301F and in compliance with GLP. Both studies concluded that the respective dibutyltin compounds are not readily biodegradable. It can therefore be concluded that dibutylbis (pentane-2,4 -dionato-O,O')tin is not readily biodegradable.

Read-across between dibutyltin compounds to to dibutylbis (pentane-2,4 -dionato-O,O')tin 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.