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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

As no data was available on the substance itself, the following two studies were submitted to assess toxicity to aquatic algae and cyanobacteria:
Oldersma H, Hanstveit AO & de Wolf JM (2003) 1,3,2-Dioxastannepin-4,7-dione, 2,2-dibutyl-(DBTM) (CAS # 78-04-6): Determination of the effect on the growth of the fresh water green algae Scenedesmus subspicatus. 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.: V4017/05. Report date: 2003-10-16
The study was selected as the key study as it was performed on a similar substance, dibutyltin maleate, the non-methylated form of the registered substance. The study was performed in compliance with GLP and to the OECD guideline 201. The study was therefore assigned a reliability score of 2. The 72h ErC50 for the test material was 4.1 mg/L and the estimated 72h NOEC was 0.88 mg/L based on the growth rate.
As supporting information, the study Steger-Hartmann T (1999) Growth inhibition test of di-n-butyltin oxide (ZK 26385) on the green algae Scenedesmus subspicatus. Testing laboratory: Schering AG, Experimentelle Toxikologie, D-13342 Berlin, Germany. Owner company: Schering AG, Experimentelle Toxikologie, Berlin, Germany. Report No.: IC28. Company study No.: TXST19980234. Report date: 1999-02-17, is provided. In this study, a saturated solution of di-n-butyltin oxide (1.6 mg/L) was not toxic to the green algae Scenedesmus subspicatus.

Key value for chemical safety assessment

EC50 for freshwater algae:
4.1 mg/L
EC10 or NOEC for freshwater algae:
0.88 mg/L

Additional information

Oldersama et al (2003) has been performed using dibutyltin maelate (CAS: 78-04-6) and is being used for read-across purposes to fulfil the endpoint for dibutyltin methyl maleate (CAS: 15546-11-9). Dibutyltin maleate is determined to be the the structure most similar to dibutyltin methyl maleate and so this study is considered the key study for this endpoint.

The study has been performed to the appropriate guideline and to GLP, however as the study is being used for read-across purposes the Klimisch score has been reduced from a 1 to a 2.

In this determination of the effect on the growth of the fresh water green algae Scenedesmus subspicatus study, the 72h ErC50 for the test material dibutyltin maleate was 4.1 mg/L and the estimated 72h NOEC was 0.88 mg/L based on the growth rate. The analytical data demonstrated stable test substance concentrations during the test. The effect values were based on the average of the measured concentrations of 1,3,2-dioxastannepin-4,7-dione, 2,2-dibutyl- (DBTM). The toxicity estimates derived from the statistical model demonstrated that 1,3,2-dioxastannepin-4,7-dione, 2,2-dibutyl- (DBTM) had a significant adverse effect on the growth rate (ErC50). The lower EbC50 value is therefore considered to have no toxicological relevance. The study was conducted to the OECD Guideline no. 201 and the EU Guideline no. C.3, and in compliance with the OECD Principles of Good Laboratory Practice.

Steger-Hartmann (1999) has been performed using dibutyltin oxide and so is used a supporting information due to the fact that it is known that organotin ligands are expected to hydrolyse to this form over time.

The study has been performed to the appropriate guideline but is allocated a Klimisch score of 2 as the reliability is reduced for read-across purposes.

The green algae Scenedesums subspicatus was exposed to aqueous solutions of dbi-n-butyltin oxide (0, 0.2, 0.4, 0.8 and 1.6 mg/l) for a test duration of 72 h. The increase in biomass and growth rate of each concentration were compared to those of the controls, and the inhibition was calculated. The observed reduction in growth was not prominent and showed no concentration-dependence. It was therefore interpreted as not being substance-related. the biomass and growth rates could not be calculated. A saturated solution of di-n-butyltin oxide is not toxic to the green algae Scenedesmus subspicatus.