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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The following studies have been submitted in support of the biodegradation in water: screening tests endpoint:
Beimborn (2000) Determination of the Biodegradability of TZ 03498 the the Manometric Respirometry Test. Report no.: 99/0606/26/1. Report date: 2000-11-06.
Errécalde et al (1995) Biotransformation of Butyltin Compounds Using Pure Strains of Microorganisms. APPLIED ORGANOMETALLIC CHEMISTRY, VOL. 9, 23-28 (1995).
Günzel P et al (1991) Study on the biodegradability of Di-n-butyltin dichloride in the modified Sturm test. Report no.: IC 4/92. Report date: 1993-07-09.
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. Report no.: V4017/01. Report date: 2003-09-24.
Hanstveit R (2003) Dibutyloxostannane (Dibutyltin oxide, CAS No. 818-08-6): Determination of the ready biodegradability in a Manometric Respiration Test. Report no.: V4016/01. Report date: 2003-09-24.
von Schulthess. A (1992) Report on the test for ready biodegradability in the Modified Sturm Test of Irgastab T 22 M. Report no.: 928294. Report date: 1992-09-18.
von Schulthess. A (1993) Report on the test for ready biodegradability in the Modified Sturm Test of Irgastab 17 M. Report no.: 928310. Report date: 1993-04-14.
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.
All references have been allocated a Klimisch score of 2 except for Errécalde et al (1995) which has been allocated a Klimisch score of 4. No data were available on the registration substance, all available studies were performed on similar substances and read-across to the registration substance.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

All dibutyltin compounds degrade into dibutyltin and the appropriate ligand, and so on this basis, it is possible to read-across between the different dibutyltin compounds to address the biodegradation in water: screening tests endpoint. As no biodegradation data are available for diisotridecyl 3,3'-[(dibutylstannylene)bis(thio)]dipropionate this endpoint has been addressed by using the weight of evidence approach reading across from data conducted on other dibutyltin compounds. This approach shows that diisotridecyl 3,3'-[(dibutylstannylene)bis(thio)]dipropionate is not biodegradable.

Reference: Beimborn (2000) - Read-across from DBT-2EHMA.

Reliability score and rationale: 2 (reliable with restrictions) Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.

Results: The biodegradabiliy of TZ 03498 was examined in a manometric respirometry test, according to OECD 301 F. The mean biodegradation after 28 days was 35.3% and the test substance could therefore not be classified as ready biodegradable. The study was extended to 74 days, for which the mean biodegradability was found to be 56%.

Reference: von Schulthess. A (1992) - Read-across from DBT-2EHMA.

Reliability score and rationale: 2 (reliable with restrictions) Study conducted in accordance with generally accepted scientific principles, possibly with incomplete reporting or methodological deficiencies, which do not affect the quality of the relevant results.

Results: In a Determination of the biodegradability study by measurement of the carbon dioxide formation in per cent of ThCO2 (Theoretical Carbon dioxide) calculated from the ThOC (Theoretical organic carbon) or TOC (Total organic carbon), TK 11638 was found to be not readily biodegradable. The study was conducted according to the 84/449/EEC C.5 guideline (Biotic degradation: modified Sturm test).

Reference: von Schulthess. A (1993) - Read-across from DBT-2EHMA.

Reliability and rationale: 2 (reliable with restrictions) Study conducted in accordance with generally accepted scientific principles, possibly with incomplete reporting or methodological deficiencies, which do not affect the quality of the relevant results.

Results: In a Determination of the biodegradability study by measurement of the carbon dioxide formation in per cent of ThCO2 (Theoretical Carbon dioxide) calculated from the ThOC (Theoretical organic carbon) or TOC (Total organic carbon), TK 11638 was found to be not readily biodegradable. The study was conducted according to the 84/449/EEC C.5 guideline (Biotic degradation: modified Sturm test).

Reference: Hanstveit R (2003) - Read-across from DBTO.

Reliability score and rationale: 2 (reliable with restrictions) Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. Read-across from supporting substance.

Results: In a Ready Biodegradability: Manometric Respirometry Test (OECD Guideline 301 F) the test material was considered to be not readily biodegradable. The percentage degradation of dibutyloxostannane after 28 days of incubation did not exceed 0% in a manometric respiration test at a mean test substance concentrations of 34±3.9 mg/l calculated from the ThOD NH3 (1.54 mg O2/mg) of test substance. The biodegradation of dibutyloxostannane did not exceed the pass level of 60% ThOD NH3 within 28 days and, therefore, is classified as not readily biodegradeable. Dibutyloxostannane is not toxic to the inoculum, but a slight inhibition of the degradation of the reference substance was observed.

Reference: Günzel P et al (1991) - Read-across from DBTC.

Reliability score and rationale: 2 (reliable with restrictions) Preferred study for this SIDS endpoint; guideline study conducted under GLP.

Results: In a study on the biodegradability (performed to OECD 301B) of Di-n-butyltin dichloride in the modified Sturm test the test material can be described as not readily biodegradable under the conditions of the test, according to the stringent test criteria.

The test product di-n-butyltin dichloride was degraded within 28 days to approx. 6 % in the saturated solution of 4 mg/l, and to approx. 1% in the concentration of 20 mg/l (suspension). The data indicate that inhibition of the microbial population occurred to a certain extent during an adaption period of approx. 20 days, because the CO2produced by the test solutions was lower than that of the blank. This was, however, not concentration-dependent. Therefore, it can be suggested that the particles of the suspension were not bioavailable for the microbes. This does not mean that the test compound is not biodegradable at all, but further testing may be necessary to establish biodegradability.

Reference: Hanstveit Ir. R. (2003) - Read-across from DBTM.

Reliability score and rationale: 2 (reliable with restrictions) Preferred study for this endpoint; guideline study conducted under GLP.

Results: In a Determination of the ready biodegradability in a Manometric Respiration Test (OECD Guideline 301 F) the test material can be described as not readily biodegradable under the conditions of the test, according to the stringent test criteria. 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% ThODNH3within 28 days and, therefore, is classified as not readily biodegradable.

Reference: Hanstveit Ir. R. (2003) - Read-across from DBTL.

Reliability score and rationale: 2 (reliable with restrictions) Preferred study for this endpoint; guideline study conducted under GLP.

Results: The biodegradability was determined as described under "Manometric Respirometry Test" in the OECD Guideline 301F for testing of chemicals: "Ready Biodegradability," using oxygen consumption as test criterion in a 39 day test. The test was extended to 39 days, because the plateau phase had not been reached after 28 days of incubation.

The test material was degraded for 23% after 39 days. The 60% degradation criterion was not met and therefore, under the conditions required by OECD Guideline 301F, was considered not ready biodegradable.

Reference: Errécalde et al (1995) - Read-across from TBTC and it's degradation products.

Reliability score and rationale: 4 (not assignable) Provided for informational purposes only.

Results:The debutylation of tributyltin chloride by several strains of fungi, yeasts and bacteria is described.Under standard conditions and with low initial concentration of substrate, significant bioticdegradation of tributyltin (6-32%) was detectedafter five days at 28 °C. Dibutyltin and monobutyltin were formed in all cases, with higher yields of the latter. Two microorganisms catalysed the transformation of monobutyltin to dimethyltinand trimethytin whereas all microorganisms wereable to methylate inorganic tin(IV) to trimethyltin.Results suggest that tributyltin biodegradation by microorganisms is generally possible, providedsufficiently low concentrations of substrate are used. All 7 microorganisms biodegraded TBTC at various extents ranging from 6 to 32% (of tin), and the major product of TBT degradation was MBT. For DBTC, most of the degradation to MBT was abiotic, and fungi biodegraded DBT to MBT to extent of 10-26% (of tin).